This PDF file contains the front matter associated with SPIE Proceedings Volume 8001, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Color perception in real conditions is determined by the spectral and spatial properties of objects and illumination. These properties are best evaluated by spectral imaging, a technique that records the reflecting spectral profile for each point of the scene. Using this technique on a set of natural scenes it was found that the color gamut expressed in the CIELAB color space is much smaller than the theoretical limits defined for the object colors. Moreover, the colors more frequent are those around the white point and their frequency of occurrence can be well described by a power law. Spatial variations of the spectral composition of the illumination across natural scenes were also quantified by placing small reflecting spheres in different locations of the scenes. The extent of these variations across scenes was found to be large and of the same order of magnitude as the variations of daylight along the day. These findings show that colors in nature are considerable constrained and that constancy mechanisms must be efficient over a wide range of stimuli variations to compensate for large natural variations of illumination.

The advent of modern solid-state sources enabled almost any spectrum for lighting and a wide range of possibilities in color rendering. The quality of the lighting has been typically evaluated by the color rendering index which measures how much the colors of objects illuminated by the light under test look similar to those produced when the objects are illuminated by the daylight or a conventional incandescent light. On the other hand, how colorful or vivid the colors under the illumination are perceived is also an important quality to evaluate lighting. We investigated, computationally, the spectral profiles of the illumination that maximizes the theoretical limit of the perceivable object colors. A large number of metamers with various degree of smoothness were generated using the Schmitt's elements method at chromaticity points on and around the Planckian locus ranging from 2,222 K to 20,000 K. The general color rendering index (CRI) and MacAdam volumes in CIELAB color space were calculated for each metamer. The metamers maximizing the CRI had smoother spectra than the metamers maximizing the MacAdam volume. These results show that maximum colorfulness in nature can only be obtained with spectrally non-smooth illumination.

Common descriptors of light quality fail to predict the chromatic diversity produced by the same illuminant in different contexts. The aim of this paper was to study the influence of the chromatic adaptation in the context of the development of the color diversity index, a new index capable of predicting illuminant-induced variations in several types of images. The spectral reflectance obtained from hyperspectral images of natural, indoor and artistic paintings, and the spectral reflectance of 1264 Munsell surfaces were converted into the CIELAB color space for each of the 55 CIE illuminants and 5 light sources tested. The influence of the CAT02 chromatic adaptation was estimated for each illuminant and for each scene. The CIELAB volume was estimated by the convex hull method and the number of discernible colors was estimated by segmenting the CIELAB color volume into unitary cubes and by counting the number of non-empty cubes. High correlation was found between the CIELAB volume occupied by the Munsell surfaces and the number of discernible colors and the CILEAB color volume of the colors in all images analyzed. The effects of the chromatic adaptation were marginal and did not change the overall result. These results indicate that the efficiency of the new illuminant chromatic diversity index is not influenced by chromatic adaptation.

A new experimental setup for any standard Video Display Unit (VDUET) with dichromatic glasses was developed for fixation disparity (FD) accessing. A computer software produce a dark field with white targets for central and peripheral fusion and two lines colors red and green for dissociated vision with the use of red and green filters. These lines can be moved right or left by the subject, until are seen apparently aligned. The real displacement between the lines is then recorded. The fixation curve (FC) is obtained by the interposition of prisms before one or both eyes, as in a regular commercial FD test. A comparison for FD and measurement time between this experimental setup and two commercially available methods, Wesson and Saladin cards, was performed in thirty-two university students. The means slope, x-intercept and y-intercept were 0.13, -0.22 and -5.63 for Saladin; 0.01, -2.29 and -1.88 for Wesson; and 0.61, -1.33 and -2.46 for VDUET. The mean measurement test time was 582.3 s, 501.3 s and 444.8 s for Saladin, Wesson and VDUET. The FC measured by these three methods was different but not statically significant (ANOVA one-way, Tukey post-hoc test) with the exception of the slope between Wesson test and VDUET (p<0.05). The average time measurement for the VDUET was the faster by about one minute, although statically significant differences (ANOVA one-way, Tukey posthoc test) were only found between Saladin and VDUET (p<0.01). The VDUET has some features that represent some improvement over the current commercial methods for DF measurement.

The scattering properties of transparent conductive oxide (TCO) layers are fundamentally related to the performance of thin film silicon solar cells. In this study we introduce an experimental technique to access light scattering properties at textured TCO-silicon interfaces. Therefore we prepared a sample with a polished microcrystalline silicon layer, which is deposited onto a rough TCO layer. We used the measured results to validate calculations obtained with rigorous diffraction theory, i.e. a numerical solution of Maxwell's equations. Furthermore we evaluated four approximate models based on the scalar scattering theory and ray tracing and compared them to the rigorous diffraction theory.

We investigate optical spatial solitons in a one-dimensional periodic stack whose unit cell is composed of two materials possessing quadratic nonlinearities and subjected to an array of microheaters. The periodic temperature gradient induces a variation in the refractive index due to the thermooptic effect. In contrast to ordinary photonic crystals, in such thermo-laminated system one may easily change parameters such as period and modulation depth of the induced index modulation. Furthermore, one can easily translate the modulation in time and introduce defects. We have found that is possible to steer solitons, change its shape, split it in two or more lower power solitons and move them independently.

The wavefront aberration is the difference between the real wavefront forming an image of an object point and a close reference sphere, described as an aberration function. This wavefront aberration function has been expressed by different authors as different polynomial families or polynomial series. This polynomial has their own characteristics and applications. The physical interpretation is customarily done in terms of Seidel, Zernike, Stephenson and many other aberrations. We will compare these different representations and will propose a new one.

This paper is intended to introduce ptychography, a novel and very promising phase retrieval technique. It is based on the lens-less recording of a series of diffraction patterns caused by coherent object illumination. In the visible region of light, ptychography has successfully been implemented for visible light microscopy and optical metrology. Ptychography has also successfully been applied to X-ray microscopy where it is difficult to manufacture good quality lenses and where, at high X-ray energies, absorption contrast is low but where phase contrast is significant. In the course of this paper theoretical fundamentals of ptychography are explained, advantages in comparison to traditional optical techniques are represented and applications are shown.

We have investigated laser ablation in InSb in the fluence regime of 8.5 J/cm² to 21 J/cm² by studying the crater morphology. Crater morphology shows a non linear change in depth, volume and roughness at fluence of 14.5 J/cm² (Fcr) and above. These non linear variations with presence of several micro-cavities at the crater bottom (potential bubble nucleation sites) suggest a different material removal mechanism at F_cr and above. The results have been explained in light of various ablation theories which support explosive boiling as a possible mass removal mechanism at Fcr and above. Thermal melting model for laser ablated InSb is in good agreement with the experimental results.

Compressive sensing (CS) has recently emerged and is now a subject of increasing research and discussion, undergoing significant advances at an incredible pace. The novel theory of CS provides a fundamentally new approach to data acquisition which overcomes the common wisdom of information theory, specifically that provided by the Shannon-Nyquist sampling theorem. Perhaps surprisingly, it predicts that certain signals or images can be accurately, and sometimes even exactly, recovered from what was previously believed to be highly incomplete measurements (information). As the requirements of many applications nowadays often exceed the capabilities of traditional imaging architectures, there has been an increasing deal of interest in so-called computational imaging (CI). CI systems are hybrid imagers in which computation assumes a central role in the image formation process. Therefore, in the light of CS theory, we present a transmissive single-pixel camera that integrates a liquid crystal display (LCD) as an incoherent random coding device, yielding CS-typical compressed observations, since the beginning of the image acquisition process. This camera has been incorporated into an optical microscope and the obtained results can be exploited towards the development of compressive-sensing-based cameras for pixel-level adaptive gain imaging or fluorescence microscopy.

Purpose: Average roughness (R_a) is generally used to quantify roughness; however it makes no distinction between spikes and troughs. Shape parameters as kurtosis (R_ku) and skewness (R_sk) serve to distinguish between two profiles with the same R_a. They have been reported in many biomedical fields, but they were no applied to contact lenses before. The aim of this study is to analyze surface properties of four silicone hydrogel contact lenses (CL) by Atomic Force Microscopy (AFM) evaluating Ra, Rku and Rsk. Methods: CL used in this study were disposable silicone hydrogel senofilcon A, comfilcon A, balafilcon A and lotrafilcon B. Unworn CL surfaces roughness and topography were measured by AFM (Veeco, multimode-nanoscope V) in tapping mode^TM. R_a, R_ku and R_sk for 25 and 196 μm² areas were determined. Results: Surface topography and parameters showed different characteristics depending on the own nature of the contact lens (Ra/Rku/Rsk for 25 and 196 μm² areas were: senofilcon A 3,33/3,74/0,74 and 3,76/18,16/1,75; comfilcon A: 1,56/31,09/2,93 and 2,76/45,82/3,60; balafilcon A: 2,01/33,62/-2,14 and 2,54/23,36/-1,96; lotrafilcon B: 26,97/4,11/-0,34 and 29,25/2,82/-0,23). In lotrafilcon B, with the highest R_a, R_ku showed a lower degree of peakedness of its distribution. Negative Rsk value obtained for balafilcon A showed a clear predominance of valleys in this lens. Conclusions: K_ku and R_sk are two statistical parameters useful to analyse CL surfaces, which complete information from R_a. Differences in values distribution and symmetry were observed between CL.

Purpose: The lipid layer of the tear film limits evaporation during the inter-blink interval and also affects tear stability. This study was designed to validate a new software application designed to characterize the tear film lipid layer through texture and colour pattern recognition. Methods: Using the Tearscope-plus (slit lamp magnification 200X), the lipid layer was examined in 105 healthy young adults and interference photographs acquired with a Topcon DV-3 digital camera. The photographs were classified by the new software and by 2 further observers (observer 1 and observer 2) with experience in examining the eye surface. Results: Strong correlation was detected between the categories determined by the new application, observer 1 and observer 2 (Cramer's V, from 0.81 to 0.87, p<0.001). Best agreement (96.2%) was noted between the new method and observers 1 and 2 for recognizing meshwork patterns, whereas observers 1 and 2 showed greatest correspondence when classifying colour fringe patterns. Conclusions: The new application can objectively categorize LLPs using the Tearscope-plus.

The establishment and development of optometry in Portugal resulted from the committed work of many individuals and institutions. These efforts have had good results in terms of raising the public's awareness of the major role played by optometrists in primary eye care. Back in the late 80's higher education in optometry was started. Ten years ago the results of scientific research on the topic first became available and are now also contributing to the success of optometry in Portugal. In regard to the optometry profession, specific regulations are to be discussed in the national parliament. The Associação de Profissionais Licenciados de Optometria (APLO), as the professional organization representing optometrists in Portugal, has been critically important in this process. This article will present an overview of the history of optometry in Portugal, of change in the foreseeable future and of the APLO's experience and activities.

The aluminium oxynitride system offers the possibility to obtain a wide range of optical responses, by combining metallic aluminium, aluminium oxide and aluminium nitride properties, and thus opening a significant number of possible applications. The main purpose of the present work is to study the variation of the optical properties of AlNxOy thin films as a function of their composition (by varying both x and y coefficients), and the correspondent changes in their morphology and structure. The films were deposited by DC reactive magnetron sputtering, with the discharge parameters monitored during the deposition in order to control the chemical composition. The measurements reveal a smooth change of films Reflectance/Transmittance as a function of the concentration ratio of non metallic elements (O+N) to metallic Al, thus revealing the possibility to tailor the films optical properties according to the application envisaged.

Optical coherence tomography is nowadays an established imaging technique in Ophthalmology, with a key role on early detection of macular diseases, benefiting from the tremendous evolution in principles and technological developments of the last 20 years. In this paper the most important physical principles behind time-domain, spectral-domain and Fourier-domain OCT will be presented, along with examples of applications in different imaging fields, emphasizing the limitations of current systems, their performance parameters, as well as the challenges for the future within this field of development.

Nanoparticles have great potential towards optical investigations in biological tissues which include imaging applications as well as therapeutic applications. However the effectiveness of these techniques is greatly governed by the optical properties of the nanoparticles. In this context this work performs computational investigations in determining the scattering and absorption efficiencies of spherical nanoparticles for a variety of nanoparticle dimensions and compositions over a wavelength band ranging from 380nm - 1064nm. The simulation results show that the optical response of the nanoparticles greatly varies with the material property, the radii of the particle as well as the laser wavelength and the results obtained aids in the selection of suitable nanoparticle for specific biomedical applications.

This paper describes a strategy for the detection of gastrointestinal (GI) dysplasia using a miniaturized system to be integrated within an endoscopic capsule. This system will be able to perform spectroscopy measurements in specific spectral bands, which have the potential to provide biological information of normal and diseased tissue. The designed instrument is based on highly selective thin-film optical filters and silicon photodiodes for the selection and detection of different spectral bands significant for diagnosis. A thin-film optical interference filter and a silicon photodiode were designed and fabricated for diffuse reflectance measurements in the green spectral band. A qualitative analysis of GI spectroscopic data using this specific spectral band is performed. Using a single optical filter, a good sensitivity and specificity were obtained for the diagnosis of GI dysplasia.

In this work, we have theoretically grounded conceptions of characteristics points observed in coordinate distributions of Mueller matrix elements for a network of human tissue biological crystals. Found is interrelation between polarization singularities of laser images inherent to these biological crystals and characteristic values of above matrix elements. We have determined criteria for statistical diagnostics of pathological changes in the birefringent structure of biological crystal network by using myometrium tissue as an example.

The objective of this paper is to carry out photoacoustic investigation of surface plasmons, so as to explore the possibility of employing photoacoustic techniques in real time sensing based on plasmon resonance spectroscopy. Such sensors exploit the high sensitivity of the surface plasmon frequency to the refractive index of layers of adsorbed molecules on the surface. Generally the resonance conditions are influenced by the material adsorbed onto the thin metal film, which will be explored in this project. An in house developed photoacoustic technique is employed as the detection system and subsequent spectroscopic investigations.

High precision measurements of long distances for intrasatellite ranging have very specific requirements and constraints. In particular, performance parameters like accuracy, ambiguity range, update rate, complexity, weight and flexibility are of great relevance for space missions. The baseline of optical laser metrologies for distance measurement in space relies on diode pumped Nd:YAG NPRO (Non-Planar Ring Oscillator) lasers with significant demands on power, mass, and cost. Semiconductor diode lasers represent one option, offering compactness, integrability and flexibility, but the current drawback of this technology is the non-availability of frequency-stable laser diodes, either CW or pulsed. In this paper we present a new metrology concept based on quantum dot modelocked diode laser with relaxed requirements in terms of frequency stability, that can meet the specifications of a metrology system for intrasatellite distances up to 250m with accuracies better than 100 micrometers.

Pose and illumination are identified as major problems in 2D face recognition (FR). It has been theoretically proven that the more diversified instances in the training phase, the more accurate and adaptable the FR system appears to be. Based on this common awareness, researchers have developed a large number of photographic face databases to meet the demand for data training purposes. In this paper, we propose a novel scheme for 2D face database diversification based on 3D face modeling and computer graphics techniques, which supplies augmented variances of pose and illumination. Based on the existing samples from identical individuals of the database, a synthesized 3D face model is employed to create composited 2D scenarios with extra light and pose variations. The new model is based on a 3D Morphable Model (3DMM) and genetic type of optimization algorithm. The experimental results show that the complemented instances obviously increase diversification of the existing database.

In this work we analyze the optical quality, performance, and recording mechanism of holographic diffraction gratings recorded in photopolymerizable sol-gel glasses. These classes of holographic photomaterials have various compositions, one of which incorporates a High Refractive Index Species (HRIS), already developed in our group GICO-UCM. The new types of photopolymerizable glasses under study incorporate ionic liquid (IL). We present a comparative study, showing distinctive behaviors for each photopolymerizable glass class, and determining particular features for various ranges of applications.

So far, concepts for three dimensional biomedical imaging rely on scanning in at least one dimension. Single-shot holography1, in contrast, stores three-dimensional information encoded in an electro-magnetic wave scattered back from a sample in one single hologram. Single-shot holography operates with simultaneous recordings of holograms at different wavelengths. While the lateral sample information is stored in the interference patterns of individual holograms, the depth information is obtained from the spectral distribution at each lateral image point, similar to Fourier-domain optical coherence tomography². Consequently, the depth resolution of the reconstructed image is determined by the bandwidth of the light source, so that a broadband light source is needed to obtain high depth resolution. Additionally, the holographic material, in which the holograms are stored, restricts the useable bandwidth. A thick photorefractive crystal can store several holograms of different wavelengths at once. As the crystal works best when using a source with a discrete spectrum, a light source is needed that has a spectrum with well distinguishable laser lines. In a proof-of-principle experiment, we use colliding pulse mode-locked (CPM)³ laser diodes as light sources with a comb-like spectrum to demonstrate the concept of single-shot holography by storing multiple holograms at the same time in a photorefractive Rh:BaTiO3 crystal.

Ln2O3-doped fluorosilicate (SNbKZF: SiO₂ - Nb₂O₅ - K₂O - ZnF₂) glasses were prepared and characterized through various spectroscopic techniques such as optical absorption, excitation and emission spectra at room temperature to derive luminescence properties of Ln³⁺ ions in these glasses. Judd-Ofelt analysis has been successfully applied to evaluate the Judd-Ofelt intensity parameters Ωλ (λ = 2,4 and 6) and in turn radiative properties such as radiative transition probabilities A_R, branching ratios β_R, radiative lifetime τR and stimulated emission cross-sections σ( λ_p) of the fluorescent levels of Ln³⁺ ions in titled glasses. The predicted values of τ_R and β_R from the fluorescent level to its lower lying levels have been compared with the experimental ones. The fluorescence decay rates have been measured and are found to exhibit single exponential nature at lower concentrations and turn into non-exponential at higher concentrations. The non-exponential decay rates are well-fitted to Inokuti-Hirayama model for S = 6 indicating that the nature of the energy transfer process among the Ln³⁺ ions is of dipole-dipole type. In the present work all our systematic analysis has been presented with an example of results obtained in Sm³⁺: SiO₂ - Nb₂O₅ - K₂O - ZnF₂ glasses. These results are used to access the gain media and in turn useful not only to write waveguides but also to modify the fluorescence properties through femtosecond laser irradiation.

We present a laser direct-write technique that is capable of providing microlens arrays on soda-lime glass substrate from one step ablation process, permitting one to shorten the typical times of microlens fabrication with other direct-writing techniques. The technique is based on the combination of a Q-switched Nd:YVO4 laser and a galvanometer system for addressing the output beam laser. The geometrical and optical parameters of the microlenses have been measured to characterize the microlens arrays produced on an area of 2 mm×2 mm. Focal length values around 118 μm have been obtained by measuring the sag and the diameter of the microlens with a confocal microscope (nondirect method) or directly, using a microscope objective with a CCD camera. The practicality of both methods is shown in the good agreement between the obtained results for the focal length of microlenses. By using a noncontact profilometer, the surface roughness of the microlens has been measured and compared with that of a glass substrate.

In this work we perform a simulation study for yttrium calcium oxyborate (YCOB) as the nonlinear medium for optical parametric amplification. These results will be used to design a new large bandwidth, 10 Hz, OPCPA stage at the Laboratory for Intense Lasers at IST, pumped by an ytterbium-based amplifier and seeded by a white light continuum. Different regimes are tested to assess the scalability of the material

A wide range of applications in diffractive optics (DO) have benefited from the use of liquid crystal (LC) panels, ranging from imaging applications, both in mono and in polychromatic illumination, in optical signal processing or in digital holography to name a few. These are fields where we have dedicated a large research effort in recent years and here we will describe part of our results. We have studied the design and implementation of apodizing filters in imaging systems, which can be e.g. applied to compensate the longitudinal secondary axial color (LSAC). We have also analyzed the design of diffractive lenses by the generation of phase elements resulting from the multiplexing of diffractive lenses to control de polychromatic point-spread function (PSF). We analyze the use of transmission liquid crystal displays and liquid crystal on silicon (LCoS) displays that work in reflection. The later tend to exhibit temporal fluctuations in the phase modulation, which we have analyzed in order to produce more efficient diffractive optical elements (DOEs).

Dynamic Pulsing is demonstrated using a pulsed MOPA fiber laser at 1064nm. The output of the MOPA laser is a pulsed profile consisting of a burst of closely spaced pulses. Tests were performed under several materials with pulse bursts ranging from 10ns to 1μs and operating from 500kHz down to single shot. In particular, percussion drilling in stainless steel is demonstrated showing improvements in quality and speed of the process. These profiles allow high flexibility and optimization of the process addressing the specificity of the end application. Dynamic Pulsing allows the same MOPA fiber laser to be used in diverse materials as well as different processes such us marking, drilling, scribing and engraving. The pulsed fiber laser used in this study is a MOPA-DY by Multiwave Photonics. It is based on a modulated seed laser followed by a series of fiber amplifiers and ending with an optically isolated collimator. This pulsed laser model has an output in such a way that each trigger produces a fast burst of pulses, with a repetition frequency within the burst of the order of tens of MHz. Within the burst it is possible to change the number of pulses, the individual pulse profile, burst pulse period and even to generate non-periodic burst pulse separations. The laser allows full freedom for all these combinations. The study here reported compares the impact of pulse peak power, number of pulses within a burst and the pulse burst period, on process quality (heat affected zone, debris, hole uniformity) and drilling yield.

We characterize ultrabroadband white-light continuum generated in a 10 mm block of bulk sapphire pumped by ~280 fs, ~ 1 mJ laser pulses at 1053 nm. This results in a smooth and stable spectrum, extending at least from 400 to 1100 nm. The white-light continuum is characterized by using the technique of cross-correlation frequency resolved optical gating (XFROG). We used a high pass filter to minimize the effect of the spectral components above 1000 nm of the continuum spectrum in order to avoid experimental artifacts caused by the intense 1053 nm peak, and we observed good agreement between the retrieved and directly measured spectra.

The characterization of the laser linewidth and laser frequency stability is critically important for the evaluation of a metrology system performance when the working principle is based in interferometric processes. In particular, the midterm stability range, corresponding to noise in the hundreds of hertz to kilohertz bandwidth, affects strongly the measurement final accuracy when working at measurement rates at the ksample/s level. In this case, it is of crucial importance to know the uncertainty associated to the measurement of the laser instantaneous frequency and what is the variance of this value within the measurement period. In this paper we present a simple method to measure the frequency noise and obtain the Allan variance statistics for an External Cavity Diode Laser (ECDL) used in a Frequency Sweeping Interferometry (FSI) scheme for long distance high accuracy measurements. For this type of lasers, the main contributors affecting the midterm stability are the current and technical noise, including thermal and mechanical fluctuations, optical feedback, as well as the feedback stabilization techniques employed to reduce acoustic disturbances. The proposed method is based in the principle of delayed interferometry, where the variation of the laser center frequency is characterized for measurement conditions in the kilohertz range. The final accuracy of the metrology system is evaluated in accordance with the laser stability characteristics obtained by this method.

In this paper the crystalline and morphological properties of Pd thin films deposited on glass substrate by pulsed laser deposition (PLD) technique at different substrate temperatures have been investigated. These films were deposited with an excimer (XeCl) laser source (λ= 308 nm, pulse duration of 30 ns, repetition rate of 10 Hz).The fabricated films were characterized by various methods such as X-ray diffraction (XRD) and atomic force microscopy (AFM). The thickness and refractive index of samples were measured using ellipsometry. There was influence of substrate temperature on the surface roughness of thin film. The rms roughness increases with increasing temperature. As the temperature increase the crystallinity of the film also increases.

In this contribution we present an approach to incremental interferometric measurements of displacements over a limited range where the atmospheric wavelength of the coherent laser source is either directly stabilized to a mechanical reference or is corrected to fit to the reference. The idea comes from the possibility to use a highly stable material for a reference frame, material which can perform thermal expansion coefficients on the level 10^-8/K within a large temperature range up to 50K. Over a range of several K which may be the practical range for displacement measurements the coefficient is even smaller. This may outperform the best techniques of correction for the variations of the refractive index of air. The mechanics is always a part of the measurement setup and represents one of the sources of uncertainty. A link of the refractive to the mechanical reference can practically eliminate another source of uncertainty.

Wearable devices are used to record several physiological signals, providing unobtrusive and continuous monitoring. A main challenge in these systems is to develop new recording sensors, specially envisioning bioelectric activity detection. Available devices are difficult to integrate, mainly due to the amount of electrical wires and components needed. This work proposes a fiber-optic based device, which basis of operation relies on the electro-optic effect. A Lithium Niobate (LiBnO3) Mach-Zehnder Interferometer (MZI) modulator is used as the core sensing component, followed by a signal conversion and processing stage. Tests were performed in order to validate the proposed acquisition system in terms of signal amplification and quality, stability and frequency response. A light source with a wavelength operation of 1530- 1565 nm was used. The modulated intensity is amplified and converted to an output voltage with a high transimpedance gain. The filtering and electric amplification included a 50Hz notch filter, a bandpass filter with a -3 dB bandwidth from 0.50 to 35 Hz. The obtained system performance on key elements such as sensitivity, frequency content, and signal quality, have shown that the proposed acquisition system allows the development of new wearable bioelectric monitoring solutions based on optical technologies.

In the last two decades digital holography emerged as one of the most promising techniques for obtaining the complex object-wave (amplitude and phase). However, due to the coherent nature of the light source used in digital holography, the reconstructed hologram is subjected to speckle noise. Moreover, the resolution and size of the sensor employed in digital holography are smaller compared to the formerly used holographic plates in optical holography. This results in a reduced resolution for the reconstructed hologram. This paper discusses two resolution improvement methods, which are both based on the same recording process. However, the recorded data is processed differently to obtain a resolution improved reconstruction. The two methods are compared in terms of corresponding optical resolution, phase accuracy and processing time.

Three-layer slab waveguide with the substrate layer made of a left-handed material (LHM) of negative and complex permittivity (ε) and permeability (μ) is investigated as an optical sensor. The effect of the negative optical parameters of the substrate on the effective index, the power, the penetration depth, and the sensitivity of the senor is studied in details. The structure is also treated as an evanescent wave optical sensor.

The main goal of this work is to create a generic foundry service that allows outside users (i.e., universities and small- and-medium enterprises) that do not have fabrication facilities to obtain their own custom-made InP-based photonic-integrated chips (or ASPIC, application-specific photonic-integrated circuits, similar to ASIC in electronics). In this approach, the foundry supplies the user with the cross-section of the interconnect waveguide structure, and the mask layout dimensions and performance of several pre-defined- and wellcharacterized building blocks (BB) such as photodiodes, phase modulators, and spot-size converters (for lowloss fiber-chip coupling). Using this information, the user can generate a mask layout for the foundry by placing the building blocks onto his layout canvas and interconnecting them with the interconnect waveguides. Furthermore, since the material cross-section of the interconnect waveguide is known, the user can design, simulate, and include a mask layout for a desired passive devices such as MMIs, and AWGs, which can subsequently be fabricated at the foundry. We describe the technology development towards obtaining a versatile generic-foundry platform which gives users the freedom to design a large variety of photonic-integrated- devices and circuits. Our generic-foundry technology is based on the fabrication process of our commercially-available high-speed- photodiodes and balanced photodiodes (high-frequency response up to and beyond 100 GHz). We have expanded this fabrication process to include a total of three different types of interconnecting waveguides: a low-contrast-, a medium-contrast, and a high-contrast waveguide, as well as transition BBs to couple light from one waveguide type into the other.

This paper evaluates various strategies proposed for single cell refractometry and spectroscopy using fiber optic sensors and microfluidic chips. Details concerning design, fabrication and characterization of the chips will be addressed. Preliminary results obtained with alternative on-chip configurations using combination of fiber Bragg gratings with mirrored single mode and multimode fibers will be presented indicating the possibility of performing simultaneous assessment of cellular refractive index and absorption properties.

A few Petawatt lasers are operative now in the world and a few more are under construction in several places. One of them is under construction at Salamanca, Spain, in the framework of a Consortium between the Central Government of Spain, the regional Government of Castilla y Leon and the University of Salamanca. The Spanish PW will reach that extreme power with 30 Joule / 30 femtosecond pulses, using Ti:Sapphire CPA technology and delivering one shot per second. The Salamanca laser will allow synchronized pump/probe experiments with a unique 200 TW probe sharing the same front end. The laser is now under construction and full operation is expected in less than two years. That laser will be a user facility opened to the national and the international scientific community. To understand the meaning of such a system, a review of the technology and its extreme applications in the foreseen range of powers and intensities is presented.

Lithium Fluoride (LiF) presents interesting optical properties and it has been proposed as an active optical material for colour centre (CC) lasers and amplifiers. The use of a grating to reduce the laser threshold and to narrow the line-width has also been demonstrated. More recently, LiF gained increased attention due to its unique characteristics as x-ray imaging detector for high resolution microscopy and for the development of CC lasers using gratings induced by high energy femtosecond laser pulses. We present a review of our recent work in the production of photonic structures, like photo-induced Bragg gratings and wave-guides either by laser CW illumination or by femtosecond laser irradiation. CW laser illuminated gratings were written in both coloured LiF crystals and films. Gratings and wave-guides are characterized using confocal microscopy, optical absorption and emission spectroscopy, near field scanning, scattering and insertion loss measurements.

We report the fabrication of a master oscillator power-amplifier (MOPA) 340W continuous-wave fiber laser. In the two-stage MOPA configuration the 100W power of master oscillator at 1090nm wavelength is amplified by Yb-doped large-mode-area fibers as the power amplifiers medium which are pumped by six 30W laser diodes in each stage. 20/400μm double cladding Yb-doped fiber was used for making the master oscillator and two other stages. For enhancing the long term reliability of the system and minimizing its loss at splices several tests were conducted (e.g various thermal pastes and mode stripping methods were used). In conclusion the optical efficiency of the MOPA is about 69% and the output power stability is ±0.5% within around 100 hours measuring time.

Planar waveguides of SiO₂:TiO₂ (multilayer structure) and SiO₂:CeO₂ (thick layer) were prepared onto commercial glass substrates using a sol-gel technique combined with dip-coating. These glassy coatings were structural characterised by Transmission Electron Microscopy (TEM) Energy Dispersive X-ray analysis and by Confocal Microscopy. Thicknesses of 1230 nm and 4,15 μm and refractive indices of 1.59 and 1.48 for SiO₂:TiO₂ (70:30) and SiO₂:CeO₂ (95:5) waveguides were obtained, respectively, by Spectroscopic Ellypsometry. Losses of 0.8 dB/cm were measured by double prism method in the SiO₂:CeO₂ system.

When passing a pulsing beam of polarize light of a light emitter d iode (LED) or a semiconductor laser thru an optical system and two photodiodes spatially arranged at 90⁰ to each other and both with their detection surfaces parallel to the transmission shaft of light, and polarization axis oriented at 45⁰ of the vertices of the edges where the photodiodes join, in the outputs of two operational amplifiers, e have two signals with the same shape in time, i.e. a pulse train with the same phase, but when you turn the polarization plane, change the radiance of the light projected onto the photodiodes, being out of phase signals to the outputs of the amplifiers, where the d ifference between the fronts of the pulses is proportional to the angle of rotation of the plane of polarization of polarization light. In a digital circuit phase discriminator, a puls e is obtained equal to the time d ifference between two sides of the rise time in the output of two amplifiers. The width of this is directly proportional to the value of rotation the plane of polarization of light, that is, the greater the rotation, the greater the width of this.

We design an experiment to obtain a Bose-Einstein Condensate (BEC) using ⁸⁷Rb atoms. Taking advantage of this setup, we develop a simple and efficient method to transfer atoms from a first Magneto- Optical-Trap(MOT) to a second one. Our system consists of two glass vacuum cells horizontally connected with a MOT aligned at the center of each cell. Once rubidium atoms are loaded into the first MOT, the pushig beam forces them to move forward to the second MOT. We use a near-resonant weak laser beam to make the atoms reach the second cell. MOT1 and MOT2 both run in retroreflected-three beam MOT configuration.

In array of nonlinear waveguides, a giant compression of the input beam can be achieved by exciting a rogue wave. Input field almost homogeneously distributed over hundreds of waveguides concentrates practically all the energy into a single waveguide at the output plane of the structure. We determine the required input profile of the electric field to achieve maximal energy concentration at output. We illustrate the phenomenon modeling the array by direct numerical simulations of the discrete nonlinear Schrodinger equation.

Generalized quantum measurements (also known as positive operator-valued measures or POVMs) are of great importance in quantum information and quantum foundations, but often difficult to perform. We present an experimental approach which can in principle be used to perform arbitrary POVMs in a linear-optical context. One of the most interesting POVMs, the symmetric, informationally complete-POVM (or SIC-POVM), is the most compact set of measurements that can be used to fully describe a quantum state. We use our technique to carry out the first experimental characterization of the state of a qutrit using SIC-POVMs. Because of the highly symmetric nature of this measurement, such a representation has the unique property that it permits all other measurement outcomes to be predicted by a simple extension of the classical Bayesian sum rule, making no use of complex amplitudes or Hilbert-space operators. We demonstrate this approach on several qutrit states encoded in single photons.

The performance of the optical frequency comb generation based on the re-circulating frequency shifter has been analyzed and demonstrated in this paper. We have theoretically analyzed the condition for flatness of the optical frequency comb and the relative intensity noise influence. And the resulting performance analysis has been confirmed by a successfully generated 16 comb lines, which are stable and flat with spacing 12.5 GHz.

Nowadays, it has become an essential task to characterize the nonlinear optical response of new materials, in order to identify suitable candidates for ultrafast processing in all-optical devices. One of the most widely-used techniques for this purpose is the Z-scan, which consists on measuring the nonlinear refractive and absorptive responses of a material by scanning the sample along the optical path of a convergent Gaussian beam. We will analyze the nonlinear response of carbon disulfide and new organic composites. In our setup, using a high-repetition rate femtosecond laser, we have included an optical chopper for managing thermal effects in order to characterize electronic nonlinearities.

A 10 Hz, 10 mJ-level Yb:KYW diode-pumped regenerative amplifier for picosecond pulses at 1040 nm was developed. It will be used in front end of the PHELIX petawatt laser system at the Helmholtz-Center GSI to pump an optical parametric amplifier (OPA) for temporal contrast enhancement. In order to achieve a high temporal contrast, this regenerative amplifier is used as the pump source in a chirped-pulse amplification arrangement, which generates picosecond pulses before frequency doubling. For synchronization purposes, the seed pulses are derived from the femtosecond oscillator of the petawatt laser system, frequency shifted and pre-amplified by two fiber amplifiers.

Tailoring and structuring optical fibres to nanoscale dimensions is rapidly becoming a focus area of research and is important for the eventual success of future in-fibre optical systems and novel technologies. Here, I review one aspect of our work in establishing and pursuing this field: localizing light for sensing.

Beam transformations process by active materials allows, in a controlled manner, the redistribution of the irradiance and phase of light. A material that exhibits quadratic gain or loss and refractive index profiles is regarded as active GRIN (GRadient-INdex) material. Complex refractive index is examined in order to discuss what loss or gain means in terms of the refractive index. General conditions for beam transformations by active GRIN materials are obtained in a 2D space of the complex curvature. Irradiance evolution through an active selfoc microlens is presented and it is analyzed at planes where beam shaping occurs.

Microstructured optical fibers (MOFs) as a novel type of light guiding media typically combine structural elements with very different chemical and optical behavior, e.g. silica - air, silica - high refractive index glasses. The applicative potential is very manifold: devices for telecommunication, nonlinear optics, sensing devices, fiber based gas lasers, etc. We report about preparation and characterization of selected total internal reflection (TIR) guiding MOFs: Air Clad Fiber, Suspended Core Fiber and heavy metal oxide (HMO) glass core MOFs. We fabricated Air Clad Fibers with extreme air fraction. The bridge width of about 0.13 μm corresponds to a numerical aperture (NA) of about 0.6. Suspended core fibers for evanescent sensing were prepared by pressurized drawing of arrangements of three and four capillaries. By inflating the cavities the NA was increased up to 0.68. Material combined MOFs were prepared for nonlinear application (e.g. supercontinuum generation) with lanthanum aluminum silicate glass core. Thermochemical and optical behaviors of high nonlinear core glass candidates were investigated for alumina concentration up to 20 mol% and lanthanum oxide concentration up to 24 mol% in silica matrix. The manufactured HMO glass core MOF with a La₂O₃ concentration of 10 mol% shows a similar background loss level like the unstructured HMO glass fiber about 1 dB/m.

A simple interrogation technique for refractive index measurement is proposed, using a multimode interference-based fiber tip structure. The fiber probe is a section of a multimode fiber, spliced to a single-mode fiber and interrogated in reflection. The interrogation technique uses two fiber Bragg gratings as discrete optical sources; by means of relative intensity variation of the reflected signals, those sources will provide a measurement of refractive index changes, while taking advantage of the MMI-based fiber tip. The read-out system uses a WDM and two photodetectors to separate both signals. A sensitivity of -5.87/RIU, in the refractive index range 1.30- 1.38, was achieved with the proposed configuration.

Air-silica nanowires present suitable waveguides to enhance nonlinearities and generate cyclical temporal compression and broadband supercontinuum (SC) in only few millimeters length. We report on the generation of few optical cycles in air-silica nanowires with core diameters ranging from 400 nm to 900 nm. We show that it is possible to shift the zero dispersion wavelengths toward a wavelength of about 470 nm. We demonstrate that soliton self-compression of lowenergy 100 fs input pulse down to 1.94 fs is possible by pumping in the anomalous dispersion regime a 570 μm-long 700 nm-core diameter air-silica nanowire. We achieve a very high temporal compression ratio of 51.55 from 100 fs to less than single optical cycle. We obtain broadband supercontinuum spanning from 260 nm to 1500 nm. By adding one photon per mode noise with a random phase, a very high degree of coherence over the entire generated supercontinuum bandwidth is shown.

Microstructured optical fibers (MOFs) have been widely studied owing to their potential for obtaining novel transmission, nonlinear and sensing characteristics. Sensing applications of MOFs cover various types of devices for measurements of different physical and specific chemical compounds in gases and liquids employing evanescent field techniques. Such fibers can also be used as active and passive elements in fiber-optic polarimetric and interferometric sensors. We present an in-line fiber modal interferometer fabricated in boron-doped highly birefringent microstructured fiber. The boron-doped region located in the middle of the core decreases the effective index of the fundamental mode and facilitates coupling between the fundamental and the first order mode. The coupling regions have the form of fiber narrowings fabricated using CO2 laser and are distant by a few millimeters. The spectral intensity at the sensor output is modulated only by intermodal interference produced by a short piece of fiber between the two coupling points. Moreover, as the fiber is highly birefringence, each pair of polarization modes produces its own intermodal fringes, which results in the contrast modulation of the overall interference signal observed at the fiber output, and provides an additional degree of freedom to measure simultaneously a pair of measurands.

This paper presents a new model for an absorptive-dispersive optical bit memory using stimulated Raman scattering slow-light (SRS). The structure of our model is developed in a low loss silicon-on-insulator (SOI) waveguide based on Stimulated Raman Scattering (SRS). Waveguide has two parts, Raman cell and feedback pass. This model functions as a memory bit and can store an optical pulse by generating a pulse train in the output. Also by using a p-i-n diode structure in Raman cell, the delay time between OB output pulses can be tuned through changing the bias voltage.

Quantum laws can be used to implement secure communication channels; this has been named quantum cryptography. In quantum cryptography the security does not depend of limited computational power, but is inherent to the laws that govern the propagation and detection of single and entangled photons. We show how single and entangled photon-pairs can be efficiently generated using four-wave mixing in optical fibers. We analyze the source statistics, degree of entanglement and impact of spontaneous Raman scattering. By coding information in the photons polarization we are able to transmit quantum information over 20 km of standard single mode fiber.

We investigate a clock enhancement technique using semiconductor optical amplifier based Mach-Zehnder interferometer (SOA-MZI) for all-optical clock recovery with numerical simulations. The simulations determine the optimal operation points of the SOA-MZI for return-to-zero (RZ) and non-return-to-zero (NRZ) inputs, achieving effective clock performance improvement.

We report an in-depth investigation of the inter-modulation crosstalk in subcarrier multiplexed (SCM) systems with optical demultiplexing (ODeMux). Both theoretical derivations and numerical simulations show that the crosstalk in ODeMux systems mainly comes from the nonlinear mixing of the baseband and subcarrier modulations inside the signal channels. Several key parameters are then studied to estimate their effects on the magnitude of the crosstalk. As a result, performance optimization strategies are proposed for ODeMux SCM systems.

Achievable resolution of nano-rings, fabricated using commonly employed conventional mask based photolithography, is limited by diffraction of light. In this work conventional photolithography is modified to incorporate the phenomenon of surface plasmons to overcome the diffraction limit and thus to fabricate nano rings. Here, an embedded-amplitude mask based surface plasmon lithography is numerically investigated to conceptalize a noval methodology to fabricate the proposed nano-ring structure. Results of FDTD simulation shows sharp transmission peaks at the hole edges which could be recorded using suitable thinned photoresist to obtain nano ring structures.

Optoelectronic oscillators can provide low noise oscillators at radio frequencies in the 0.5-40 GHz range and in this paper we review two recently introduced approaches to optoelectronic oscillators. Both approaches use an optical fibre feedback loop. One approach is based on passively modelocked laser diodes and in a 40 GHz oscillator achieves up to 30 dB noise reduction. The other approach is based on resonant tunneling diode optoelectronic devices and in a 1.4 GHz oscillator can achieve up to 30 dB noise reduction.

In the present work, a simple scheme for a Raman distributed fiber laser is proposed. The lasing scheme is based in the combination of two random cavities which act as distributed mirrors when pumped by a single laser. The distributed mirrors are created as a consequence of Rayleigh scattering and double Rayleigh scattering formed in the dispersion compensating fiber as a result of the high Raman gain. The proposed distributed fiber laser presents stable operation at room temperature, showing a maximum variation of ~0.09dBm in a 30 minutes time window. The output spectrum of the distributed fiber laser presents a broadband bandwidth of 10nm with a 30dBm signal to noise ratio. This configuration allows suppression of the Rayleigh associated noise growth typical in Raman lasers, while using it as an active part of the laser cavity.

At present time the DFB (Distributed FeeBack), VCSEL (Vertical Cavity Surface Emitting Laser) and FBG (Fiber Bragg Grating) based laser diodes are suitable like laser source for using in laser interferometry. Their linewidth of the emission spectrum and the mode-hop free tuning range of the wavelength are crucial parameters for laser sources in laser interferometry, especially absolute laser interferometry. We present our set-up of the fiber laser interferometer where these laser diodes can be used. The design of the optical set-up of the experimental interferometer is realized using fiber optics to reduce the influence of the index of refraction of air. The measurement probe was realized by standard optical fiber with reflection coated optical connector. Our primary wavelength of this laser interferometer is 760 nm. We used the DFB laser diode at 760 nm wavelength with mode-hop free tuning range above 1 nm and fiber output up to 10 mW. We present our first characteristics without external stabilization of the output wavelength. We compared our new DFB laser source with our previously developed laser source with VCSEL diode and with FBG based laser diodes. On the basis of our simulations and measurements of the commercially available fiber gratings we designed a special 100 mm long fiber Bragg grating with apodization. Finally, we simulated required parameters of fiber gratings arrays for laser interferometry - multiple fiber gratings. Results are presented.

We investigate optoelectronic oscillator (OEO) configurations based on a laser diode driven by resonant tunnelling diode (RTD) optical waveguide photo-detector (PD) oscillators, with an optical fiber feedback loop carrying a fraction of the laser diode optical output that is re-injected into the OEO through the optical waveguide of the RTD-PD. In the configurations reported here, we take advantage of the RTD negative differential resistance to provide electrical highbandwidth. The optical fiber loop acts as a high quality optical energy storage element with low transmission loss. The RTD based OEO can produces stable and low-phase noise microwave signals with attractive applications in photonics and communication systems, mainly in fiber-optic based communication links since the RTD-OEO can be accessed both optically and electrically.

We apply the diagrammatic formalism developed in Ref.1 to the study of several phenomena related to the electromagnetic vacuum of molecular dielectrics. Our approach is based on the linear response theory in the dipole approximation and exploits the fluctuation-dissipation theorem. The fundamental object which derives from it is an analytical formula for the polarization propagator in terms of the electrical susceptibility and the single-particle polarizability. That formula is used to compute the spectrum of dipole emission and the total vacuum energy density. In the former, we can distinguish the coherent emission from the total radiative emission. Regarding the latter, we show that the Lamb energy is only a part of it. As a further application, our formalism is applied to calculate, approximately, the optical response of nematic liquid crystals.

We present a novel co-axial dual core resonant leaky fiber (DCRLF) design for inherent gain equalization of S-band erbium doped fiber amplifier (EDFA). Spectral leakage loss variation of the structure has been utilized to suppress the amplified spontaneous emission (ASE) in the C-band and to achieve inherent gain flattening in the S-band of an EDFA. We show 19 dB flat gain with ± 1.1 dB ripple over 30 nm bandwidth (1490-1520 nm) and 20 dB flat gain with ± 2.1 dB ripple over 40 nm bandwidth (1485-1525 nm). We have also carried out a detailed tolerance study of the designed Sband EDFA with respect to the outer cladding parameters.

This paper introduces a new bidirectional mmRoF system based on optical frequency multiplication (OFM) scheme using dual drive Mach-Zehnder Modulator (DD-MZM) and OFDM modulation. The emphasis is put on the optimization of optical modulation index to the MZ intensity modulator for OFDM signal with high PAR which imposes a limitation on the system bit error rate (BER) performance due to the nonlinearity of the MZ modulator. The theoretic analysis on carrier to composite triple beat ratio is performed. The extension to system BER for QAM format is presented and the experimental proof is given in a 40 GHz mmRoF system.

In this paper we present comparative performance results of optical amplification alternatives, employed to extend the reach of the optical link for the transport of RoF (Radio over Fiber) signals for wireless applications.

In this work, we conduct a thoroughly comparison between different Stokes polarimeters based on Liquid Crystal Displays: polarimeters based on a single Twisted Nematic Liquid Crystal panel and on two Parallel Aligned Liquid Crystal panels. We carry out an optimization of the different polarimetric systems in order to reduce the noise propagation when measuring the polarization. In addition, we implement the three best optimized polarimeters. The experimental results are provided and discussed. We demonstrate that by performing an accurately optimization of a dynamic Stokes polarimeter based on a single Twisted Nematic Liquid Crystal panel, we achieve results close to those obtained by polarimeters based on two Parallel Aligned Liquid Crystal panels.

The light transmission factor of a device containing a liquid crystalline layer between crossed polarizers was estimated considering the losses by reflection at the separation surfaces and the phase change induced by the liquid crystalline layer for a monochromatic radiation. The computed transmission factor of this device and that experimentally obtained were compared in this study. The differences between the intensities in the computed and experimental spectra are explained by the diffusion phenomenon in liquid crystalline layer. The changes induced by an external electric field both in the values of the main refractive indices and in birefringence determine modification for the light transmission factor of the used device. The results obtained in this study could be applied to design polarization filters in the visible range.

Organic-inorganic hybrid materials are a technologically key class of advanced multifunctional materials that fulfil the challenging strict requirements of the beginning of the century: higher levels of sophistication, miniaturisation, recyclability, reliability and low energy consumption with potential to be used as low-cost components in optical networks operating at high bit rates. In this work, high-rejection optical filters (19 dB) first-order Bragg gratings inscribed in channel waveguides written in thin films of sol-gel derived organic-inorganic hybrid based on methacrylic acid modified zirconium tetrapropoxide, Zr(OPrn)4, (so-called di-ureasils), using UV-laser direct-write method.

In optical security (protection against forgery and counterfeit of products and documents) the problem is not exact reproduction but the production of something sufficiently similar to the original. Currently, Diffractive Optically Variable Image Devices (DOVID), that create dynamic chromatic effects which may be easily recognized but are difficult to reproduce, are often used to protect important products and documents. Well known examples of DOVID for security are 3D or 2D/3D holograms in identity documents and credit cards. Others are composed of shapes with different types of microstructures yielding by diffraction to chromatic dynamic effects. A maskless interferometric lithography technique to generate DOVIDs for optical security is presented and compared to traditional techniques. The approach can be considered as a self-masking focused holography on planes tilted with respect to the reference optical axes of the system, and is based on the Scheimpflug and Hinge rules. No physical masks are needed to ensure optimum exposure of the photosensitive film. The system built to demonstrate the technique relies on the digital mirrors device MOEMS technology from Texas Instruments' Digital Light Processing. The technique is linear on the number of specified colors and does not depend either on the area of the device or the number of pixels, factors that drive the complexity of dot-matrix based systems. The results confirmed the technique innovation and capabilities in the creation of diffractive optical elements for security against counterfeiting and forgery.

PART ONE: The "Lab on Fiber" concept envisions novel and highly functionalized technological platforms completely integrated in a single optical fiber that would allow the development of advanced devices, components and sub-systems to be incorporated in modern optical systems for communication and sensing applications. The realization of integrated optical fiber devices requires that several structures and materials at nano and micro scale are constructed, embedded and connected all together to provide the necessary physical connections and light-matter interactions. This paper reviews the strategies, the main achievements and related devices in the "Lab on Fiber" roadmap discussing perspectives and challenges that lie ahead. PART TWO: After having reviewed, in the previous part, the main results achieved in the "Lab o Fiber" roadmap through the development of several wavelength-scale devices and components based on the lab on fiber concept, here we focus the attention on new trends involving innovative nano-fabrication strategies enabling to exploit further intriguing photonic and/or plasmonic phenomena at the forefront of optical research. Novel complex fabrication techniques of "Lab-on-fiber" device at the nanoscale are here presented and discussed, from advanced multi material stacks and drawing technique up to the use of nanotechnologies, including standard lithographic tools as well as new nano-imprinting approaches. In particular, for the first time, we report some preliminary results obtained by our multidisciplinary research group concerning the design and fabrication of a 2D hybrid metallo-dielectric photonic crystal (PC) nanostructure, directly realized by innovatively applying the electron beam lithography technique on the cleaved end of standard single mode optical fibers.

This paper presents a comparative study of the behaviour of different kinds of optical fibre sensors in response to high temperatures. It compares the performance of regenerated fibre Bragg gratings (FBGs) written in hydrogen-loaded and non-loaded fibres with long period gratings (LPGs) written through the two different processes of ultraviolet (UV) irradiation and electrical arc discharges. This work shows the importance of the use of hydrogen-loaded fibres to achieve regenerated FBGs capable of withstanding high temperatures as high as 955°C. In addition, the results demonstrated that LPGs recorded by electric arc discharges have higher thermal resistance than LPGs written by UV radiation.

Optical device based on a tilted fibre Bragg grating (TFBG) to perform simultaneous measurement of refractive index (RI) and temperature is proposed. Using two different demodulating techniques, namely monitoring the core mode wavelength and the area of the transmission spectrum, it is possible to measure, separately, temperature and RI, respectively. The proposed method uses a grating, which does not require a reduced diameter, and a single measurement equipment. Measurements with resolution up to 5.7 x 10^-4 and 0.5 °C were achieved, for RI and temperature, respectively. Theoretically, the resolution of RI measurements can go as bellow as 2 x 10^-5.

We propose the use of distributed Raman amplification to improve the sensitivity of fiber optic gyroscopes through the use of longer fiber coils. The performance limitations due to noise and nonlinear phase have been analyzed and we show that, even in the presence of pump and signal asymmetries, the proposed configurations allow increased sensitivity. Concretely, it is possible to achieve a 5-fold increase in fiber length (and sensitivity) compared to traditional schemes with no amplification. Potential applications include the design of highly sensitive fiber-based rotational seismometers.

The optimization of polymer-based optoelectronic devices such as light-emitting diodes (LEDs), photodetectors and photovoltaic cells requires the understanding how molecular properties and the spatial arrangement of the conjugated strands affect the electronic processes underlying the functioning of these devices. Since some of the important features are determined largely by the individual molecular strands and other features depend strongly on the nanostructure, a multi-scale modelling of materials and device properties is needed. In this work we discuss the atomistic and nanoscale modelling of charge injection, transport and trapping single-carrier diode based on poly(p-phenylene venylene) (PPV), which also applies to other optoelectronic devices.

Although semiconducting polymers are very attractive to be used in optoelectronic devices due to their molecular structure, they are not pristine semiconductors. After deposition it is possible to find out several structural and chemical defects, with different origins, that strongly influence exciton dynamics since they create deep energetic sites, where excitons can migrate leading to their quenching or reducing exciton diffusion length. By using a self-consistent quantum molecular dynamics method we performed a computational study to understand the influence of well-known polymer defects on excitons dynamics. Our results show that these defects influences mainly intramolecular exciton localization and exciton energy.

Integrated optics is a well established technology that finds its main applications in the fields of optical communication and sensing. However, it is expanding into new areas, and in the last decade application in astronomical interferometry has been explored. In particular, several examples have been demonstrated in the areas of beam control and combination. In this paper, different examples of application integrated optics devices for fabrication of beam combiners for astronomical interferometry is given. For the multiaxial beam combiners, a UV laser direct writing unit is used for mask fabrication. The operation principles of the coaxial combiners fabricated in hybrid sol-gel were validated using an interferometric set-up. These results demonstrate that hybrid sol-gel technology can produce quality devices, opening the possibility of rapid prototyping of new designs and concepts.

The European Space Agency (ESA) foresees several robotic missions to the Moon and to Mars ultimately aimed for the preparation of future Human exploration activities. To accomplish the robotic mission objectives Imaging LIDARs (LIght Detection And Ranging) are one of the identified key technologies that shall provide essential range and image information to the spacecraft Guidance, Navigation and Control (GN&C) system during spacecrafts critical and automatic operations. Two technology development contracts have been established for the development and demonstration of Imaging LIDAR technologies. The two applications considered were: to support spacecraft descent and landing manoeuvres; and to assist the rendezvous and docking operations between two spacecrafts. Two elegant breadboards have been designed and manufactured. The goal of these activities was to implement novel technologies in order to reduce substantially the mass and power consumption of Imaging LIDAR sensors. The Imaging LIDAR sensors foreseen for these two applications have a mass <10kg, power consumption <60Watt, measure distances up to 5000m, with a field of view up to 20x20 degrees, range resolutions down to 2 cm, and a frame rate higher than 1 Hz.

Aero-optical effects occur around moving air vehicles and impact passive imaging or active systems. The air flow around the vehicle is compressed, and often there is a turbulent shear and/or boundary layer both of which cause variations in the index of refraction. Examples of these are reconnaissance aircraft, the Stratospheric Observatory for Infrared Optics (SOFIA), and optically homing hypersonic interceptors. In other applications, a laser beam can be formed within the vehicle, and projected outward and focused on an object. These include the Airborne Laser Laboratory, Airborne Laser and the Airborne Tactical Laser. There are many compressible fluid mechanics computer programs that can predict the air density distribution of the surrounding flow field including density fluctuations in turbulent shear and/or boundary layers. It is necessary for the physical optics to be used to predict the properties of the ensuing image plane intensity distribution, whether passive or active. These include the time-averaged image blur circle and instantaneous realizations. (Ray tracing is a poor approximation that gives erroneous results for small aberrations.)

The term "Socio-optics" (as a natural part of Socio-physics), is rather not found in literature or at Congresses. In Optics books, there are not made references to optical models applied to explain social phenomena, in spite of Optics relying on the duality particle-wave which seems convenient to model relationships among society and its members. The authors, who have developed a few models applied to explain social phenomena based on knowledge in Optics, along with a few other models applying, in Social Sciences, knowledge from other branches of Physics, give their own examples of such optical models, f. e., of relationships among social groups and their sub-groups, by using kowledge from partially coherent optical phenomena or to explain by tunnel effect, the apparently impossible penetration of social barriers by individuals. They consider that the term "Socio-optics" may come to life. There is mentioned the authors' expertise in stimulating Socio-optics approach by systematically asking students taken courses in Optics to find applications of the newly got Wave and Photon Optics knowledge, to model social and even everyday life phenomena, eventually engaging in such activities other possibly interested colleagues.

Image distribution is getting more and more processor demanding, due to the increased quality requirements and the need for real time imaging. Therefore, improved techniques and processors are being designed. Another attractive approach is keeping image processing in the optical domain and extending, as much as it is possible, the functionalities performed to this domain. Optical processing is a reality in many research fields, namely optical communications. Results reported in literature show that it is possible to exploit optical components to accomplish image capture, optical transform processing, sampling and thresholding. We propose a general architecture for all-optical image acquisition, processing and transmitting, and review potential best fit for each functionality.

The electronic absorption spectra of four carbanion monosubstituted pyridazinium ylids in binary solvents are analyzed in this paper. The binary solvent is made, in different ratios, by two miscible liquids (one active and one inactive from the intermolecular interactions point of view). The composition of the first solvation shell of the studied ylids was established by using the spectral data. The concentration of the active solvent in the first solvation shell is higher than in the rest of the ternary solution. The difference is appreciable especially at low molar concentrations of the active solvent in ternary solutions. The interaction energy in pairs of pyridazinium ylid-active solvent molecules was also estimated in the limits of a cell model of the ternary solution.

In this work, it is shown a panoramically view of advances and works on fundamental optical technology developed and Physics Section at Pontificia Universidad Católica del Perú PUCP in Lima Peru. This includes works in, precision optics manufacturing, optical testing, and optical design and simulation and also in optical thin film evaporation and its design techniques

Determining the precise location of irradiance centroids is a key step for optical triangulation and wavefront sensing based on wavefront slope measurements (as e.g. in Hartmann-Shack aberrometry). Since most aberrometers include some kind of optical relay system to reimage the irradiance distributions provided by the wavefront sampling element onto the irradiance detector, it is esential to ensure that the centroid position and momentum information is preserved along this operation. In optical systems with ABCD difrraction kernels the centroids propagate according to an effective geometrical optics rule. However, the presence of finite apertures partially blocking the incoming beam or non-uniform transmittances unevenly altering its original irradiance distribution may give rise to potentially significant departures from this simple geometrical picture. The potential magnitude of this bias makes it advisable to take proper steps to counteract it in the design of aberrometric setups.

Aluminium nanoparticles were produced by pulsed laser ablation of a sample of pure aluminium situated in distilled water. This technique provides the possibility to generate a large variety of nanoparticles that are free of both surfaceactive substances and counter-ions The sample was irradiated by the focused output of the third harmonics of pulsed nanosecond Nd : YAG laser operating at 10 Hz frequency. The typical thickness of the liquid above the target was 10 mm. In order to select the most efficient material removal conditions the irradiation print on the ablated surface was analyzed as a function of the irradiation parameters (incident laser fluence, irradiation pulses number or irradiation time) with optical microscopy and white light interferometry. The presence of the ablated aluminium nanoparticles in the liquid was evidenced by SEM. For SEM measurement, one drop of solution containing Al nanoparticles was placed on a gold coated silicon substrate and dried. The minimum diameter of nanoparticles estimated by SEM was under 100 nm. The SEM results show also clusters of spherical particles together with well-defined singles. In order to improve the quantity of the ablated material the irradiation cell was mounted on a computer-driven X-Y stage and translated during laser exposure.

A simple photonic instantaneous RF frequency measurement system based on complementary modulation is proposed and experimentally demonstrated. A peak-to-peak frequency error of 400 MHz was achieved over an RF frequency range of 1-20 GHz.

When light propagates parallel to a main direction different from the optical axis, the main refractive indices corresponding to the ordinary and extraordinary radiations are determined with a Rayleigh interferometer from the phase difference between the radiation crossing the anisotropic layer (placed in the measure beam) and one isotropic layer (placed in the comparison beam). The two main indices are measured by using linearly polarized light with electric field intensity successively oriented parallel and perpendicular to the optical axis of the anisotropic layer. For incidence angles different from zero two refractive indices are measured: the refractive index for the ordinary radiation and that for the effective radiation. The effective value of the refractive index was determined from the equation of the refractive indices surfaces. Quartz from Maramures area and liquid crystalline layer were used as uniaxial samples. The birefringence of the liquid crystalline layer was modified by varying the intensity of the external electrostatic field. An increase of the birefringence was evidenced when the intensity of the electrostatic field increased.

Effects of gain or loss on the propagation of light beams through active GRIN media are discussed. Complex refractive indices are studied to discuss what gain or loss means in terms of the real and imaginary parts of them. The real part of the refractive index determines the guidance behavior of the active material and the gain or loss is determined by the sign of the imaginary part of the refractive index. Comparison between Gaussian beam propagation in active GRIN media with parabolic refractive index profile and hyperbolic secant refractive index profile is outlined.

Lead phosphate glasses containing rare earth ions were prepared in a glow box in order to minimize concentration of hydroxyl groups. Rare earths as an optically active ions were limited to Eu³⁺, Dy³⁺, Tb³⁺ and Er³⁺. Luminescence of rare earth ions in lead phosphate glasses was registered in visible spectral region. Luminescence bands correspond to ⁵D₀ - ⁷F_J(J = 0 ÷ 4) transitions of Eu³⁺ ions, ⁴F_9/2 - ⁶H_J/2 (J = 11, 13, 15) transitions of Dy³⁺ ions, ⁵D₃ - ⁷F_J' (J' = 1 ÷ 6) and ⁵D₄ - ⁷F_J (J = 3 ÷ 6) transitions of Tb³⁺ ions, and ⁴S_3/2 - ⁴I_15/2 transitions of Er³⁺ ions, respectively. Luminescence decays from excited states of rare earth ions have been analyzed in details.

Heavy metal oxide and oxyhalide glasses containing Er³⁺ ions have been investigated. Near-infrared luminescence at about 1550 nm and up-conversion spectra of Er³⁺ ions were registered under excitation by 980 nm diode laser line. Several luminescence bands are observed, which correspond to the ⁴I_13/2 - ⁴I_15/2 (1550 nm), ²H_11/2,⁴S_3/2 - ⁴I_15/2 (550 nm), ⁴F_9/2 - ⁴I_15/2 (670 nm) and ⁴I_9/2 - ⁴I_15/2 (800 nm) transitions of Er³⁺, respectively. The optical transitions of Er³⁺ ions have been examined as a function of glass host and PbX₂ (X = F, Cl, Br) content.

Two series of novel push-pull heterocyclic azo dyes have been synthesized and characterized. The two series of compounds were based on different combinations of π-conjugated bridges (bithiophene and thienylpyrrole) which also act simultaneously as donor groups, together with diazo(benzo)thiazolyl as acceptor moieties. Their thermal stability and electrochemical behavior were characterized, while hyper-Rayleigh scattering (HRS) was employed to evaluate their second-order nonlinear optical properties. The results of these studies have been critically analyzed together with several thienylpyrrole azo dyes reported earlier from our laboratories in which the thienylpyrrole system was used as the donor group functionalized with aryl and (benzo)thiazolyldiazene as acceptor moiety. The measured molecular first hyperpolarizabilities and the observed linear optical and redox behavior showed strong variations in function of the heterocyclic spacers used (bithiophene or thienylpyrrole) and were also sensitive to the acceptor strength of the diazenehetero(aryl) moiety.

Dysprosium doped fluorosilicate (SNbKZLF:SiO₂-Nb₂O₅-K₂O-ZnF₂-LiF) glasses have been prepared and studied through excitation, emission and decay rate analysis. Sharp emission peaks were observed at 485 nm (blue) and 577 nm (yellow) under 387 nm excitation, which are attributed to ⁴F_9/2 → ⁶H_15/2 and ⁴F_9/2 → ⁶H_13/2 transitions, respectively, of Dy³⁺ ions. The yellow-to-blue intensity ratio increases (0.85 to 1.19) with increase in Dy³⁺ ion concentration. The decay rates exhibit single exponential for lower concentrations and turns into non-exponential for higher concentrations. The non-exponential nature of the decay rates are well-fitted to the Inokuti-Hirayama model for S = 6, which indicates that the nature of the energy transfer between donor and acceptor ions is of dipole-dipole type. The lifetime for the ⁴F_9/2 level of Dy³⁺ ion decreases (0.42 to 0.14 ms), whereas energy transfer parameter increases (0.11 to 0.99) with increase of Dy³⁺ ion concentration (0.05 to 4.0 mol %). The chromaticity coordinates have been calculated from the emission spectra and analyzed with Commission International de I'Eclairage diagram. The chromaticity coordinates appeared in the white light region for all concentrations of Dy³⁺ ions in the present glasses. The correlated color temperature value decreases from 5597 K (closer to the day light value of 5500 K) to 4524 K with increase of Dy₂O₃ ion concentration from 0.01 to 4.0 mol %. These results indicate that Dy³⁺:SNbKZLF glasses can be considered as a potential host material for the development of white light emitting diodes.

Glasses from the system 15PbO-5Li₂CO₃-(80-x)B₂O₃-xAg₂O (x=0.5,1,2 and 4) have been prepared by the melting quenching technique. Their physical and structural properties were accessed by means of XRD, FTIR, SEM and EDS. The prepared materials present a glass surface and amorphous nature. FTIR and Raman results indicate that silver oxide acts as a network modifier even at small quantities, by converting three coordinated to four coordinated borons. These results were evaluated by measuring the relative concentrations of BO₃ and BO₄ units in the glass matrix. Other physical properties, such as density are also affected by the silver oxide composition.

The electron beam (EB) induced changes in solubility of thin As-S-Se films have been studied. Optimal absorption current choice, nano structure relief and shape dependence on acceleration voltage discussed. The possibilities of practical use of these materials as resist for gratings and optical diffractive element production using EB. New results are presented that indicate chalcogenide glasses as promising electron beam resists.

We consider design of hardware realizations of optoelectronic reconfigurable universal or multifunctional logical elements of two-valued logic with current inputs and current outputs on the basis of CMOS current mirrors and circuits which realize the limited difference functions. We show advantages of such elements consisting in encoding of Boolean variables by the photocurrent levels, that allows easily to provide optical inputs (by photodetectors) and optical outputs (by light-emitting devices). The conception of construction of the family of the offered optoelectronic photocurrent reconfigurable universal or multifunctional logical elements (OPR ULE) consists in the use of a current mirrors realized on 1.5μm or 0.35 μm technology CMOS transistors. Presence of 15-30 transistors, 1÷4 photodetectors makes the offered circuits quite compact and allows their integration in 1D and 2D arrays. In the presentation we consider the whole family of the offered circuits, show the simulation results and possible prospects of application of the circuits in particular for time-pulse coding for multivalued, continuous, neuro-fuzzy and matrix logics. The simulation results of the NOT, AND, OR, OR-NOT,XOR current logical elements and OPR ULE on the 1.5 μm or 0.35 μm technology CMOS transistors showed that the level of logical unit can change from 1 μA to 10 μA for low-power consumption variants and from 10 μA to 100 μA for high-speed variants. Signals delays, values of fronts and cutoffs at operation with impulse logical signals with 1uA logical unit are not exceed 70-140 ns and at operation with impulse logical signals with 100 μA logical unit are no more than 4-6 ns and the consumption power is 100-4000 μW.

Brownian motion is a subject of renewed interest since the development of photon correlation spectroscopy (PCS) in the last decade. The dynamic properties of microemulsions and colloidal systems are studied by measuring the relaxation of concentration fluctuations. The mixture of C₁₂E₅nanoemulsion with PEG have been studied by small-angle X-ray scattering and dynamic light scattering in order to determine structure and dynamic of the system. Light scattering experiment shown an exponential relaxation for pure C₁₂E₅ nanoemulsion that the shape of the relaxation change with increasing of polymer concentration in the C₁₂E₅ nanoemulsion, that relaxation becomes non-exponential, which demonstrates increase of cooperatively in the C₁₂E₅ nanoemulsion.

Two spectrally active molecules - carbanion monosubstituted cycloimmonium ylids having as heterocycles benzo-[f]- quinolinium and p-phenyl-pyridazinium - can offer information about the local field of forces in binary solutions. Hyper Chem. 8.0.6 software was used to characterize these molecules from the structural, energetic and electro-optical point of view. The visible band of the cycloimmonium ylids appears by an intramolecular charge transfer (ICT) from the carbanion to the heterocycle. It is very sensitive to the solvent nature. The projection of the excited state dipole moment on the dipole moment in the electronic ground state was obtained for two studied ylids on the basis of the existent theories regarding the intermolecular interactions in liquid phase studied by spectral means.

Variable - angle ATR-FTIR spectroscopy was applied to the evaluation of the in-depth homogeneity of amidation within superficial layers of poly(ethylene terephthalate) (PET) surfaces. Thin films of PET were subjected to aminolysis with triethylenetetramine and tetraethylenepentamine by wet chemistry and using air plasma as precursor, respectively, in order to create surface functionalities. By varying the incidence angle of the infrared radiation, chemical changes were investigated from layers of different thicknesses. The amide II band has been selected as a marker for monitoring the aminolysis products and for depth profiling. The choice of an exponential decay of the in-depth amide distribution was justified by the quite regular decreasing of the angular absorbance with depth of penetration of the evanescent wave.

A series of novel donor-acceptor chromophores designed to have good second order nonlinear optical responses has been synthesized and characterized. This series of compounds was designed to explore the consequence of using different electron accepting moieties which were linked through an arylthiophene bridge to a pyrrole heterocycle that plays the role of an auxiliary donor group. These new push-pull chromophores have been extensively characterized using cyclic voltammetry, thermogravimetric analysis and hyper-Rayleigh scattering (HRS) in solution. The measured molecular first hyperpolarizabilities and the observed electrochemical behavior showed that they were very sensitive to the acceptor strength of the acceptor moieties. Moreover, the combination of their good nonlinearity and high thermal stability make them good candidates for potential device applications.

The synthesis and characterization of new chromophores with second-order nonlinearities containing thienylpyrrole 1a, 2a-b, bithiophene 3 and arylthiophene 4 as π-conjugated bridges and indanonedicyanovinyl acceptor group are reported. The effect of placing the acceptor group at thiophene or pyrrole rings on the optoelectronic properties was also evaluated for thienylpyrrole derivatives 1a and 2a-b. The linear optical properties (absorption and emission) for all compounds were evaluated in dioxane solutions. In addition, the hyperpolarizabilities β of chromophores 1-4 were measured using hyper-Rayleigh scattering in dioxane solutions and thermogravimetric analysis (TGA) was used to evaluate their thermal stability. The experimental results indicate that chromophores 1-4 are endowed with both excellent optical nonlinearities and high thermal stability making them interesting candidates for nonlinear optical (NLO) applications.

To characterize the degree of consistency of parameters of the optically uniaxial birefringent protein nets of blood plasma a new parameter - complex degree of mutual anisotropy is suggested. The technique of polarization measuring the coordinate distributions of the complex degree of mutual anisotropy of blood plasma is developed. It is shown that statistic approach to the analysis of complex degree of mutual anisotropy distributions of blood plasma is effective in the diagnosis and differentiation of acute inflammation - acute and gangrenous appendicitis.

In orthodontics, the decreasing of tooth-size by reducing interproximal enamel surfaces (stripping) of teeth is a common procedure which allows dental alignment with minimal changes in the facial profile and no arch expansion. In order to achieve smooth surfaces, clinicians have been testing various methods and progressively improved this therapeutic technique. In order to evaluate the surface roughness of teeth subject to interproximal reduction through the five most commonly used methods, teeth were inspected by scanning electron microscopy and microtopographically measured using the optical active triangulation based microtopographer MICROTOP.06.MFC. The metrological procedure will be presented as well as the comparative results concluding on the most suitable tooth interproximal reduction method.

Since biological tissues can have the intrinsic property of altering the polarization of incident light, optical polarization studies are important for a complete characterization. We have measured the polarized light scattered off of different dental tissues and biomaterials for a comparative study of their optical polarization property. The experimental setup was composed by a He-Ne laser, two linear polarizers and a detection system based on a photodiode. The laser beam was passed through one linear polarizer placed in front of the sample, beyond which the second linear polarizer (analyzer) and the photodiode detector were placed. First, the maximum laser-light intensity (reference condition) was attained without the sample in the laser path. Then, the sample was placed between the two polarizers and the polarization shift of the scattered laser light was determined by rotating the analyzer until the reference condition was reached. Two dental-resin composites (nanocomposite and hybrid) and two human dental tissues (enamel and dentine) were analyzed under repeatability conditions at three different locations on the sample: 20 measurements of the shift were taken and the average value and the uncertainty associated were calculated. For the human dentine the average value of the polarization shift found was 7 degrees, with an associated uncertainty of 2 degrees. For the human enamel and both dental-resin composites the average shift values were found to be similar to their corresponding uncertainties (2 degrees). The results suggest that although human dentine has notable polarization properties, dental-resin composites and human enamel do not show significant polarization shifts.

Normal and cancer affected samples of colon tissue have been measured using transmission time-domain terahertz spectroscopy and continuous wave terahertz imaging. We show that it is possible to distinguish between normal and cancerous regions in the samples when they are fixed in formalin or embedded in paraffin. Plots of the refractive index of normal and cancer affected tissues as well as 2-D transmission THz images are shown. Experimental results will be presented and the conditions for discrimination between normal and affected tissue will be discussed.

Electronic Speckle Pattern Interferometry (ESPI) has been used in experiments to measure displacement on the surface of bones undergoing external forces. However in order to asses directly the derivative of the displacements a related technique, Shearography, is used. This technique has been applied in biomechanical experiments although limited to small pieces of bone to determine their elastic properties. In this work we propose the use of Shearing Speckle Interferometry to evaluate the mechanical behaviour of the human mandible under compressive stress, simulating masticatory forces or impacts, in order to analyze the strain distribution on mandibular bone.

Photocured polymers are widely used in dental applications. The optical properties of the dental composites change during curing; the appearance of the composites also changes. Recently, a new silorane-based composite resin and dental nanocomposite have been introduced. However, research regarding the effect of the silorane monomers or the size filler on appearance after curing of the resin composite is limited. This work aims to examine the optical properties of silorane-based composite and nanocomposite, in terms of scattering and absorption during curing. Six dimethacrylate-based dental resin composite (five universal and one nanocomposite) and one silorane-based dental resin composite (all shades A2 and T) were studied. The curing irradiance was 1100mW/cm². The spectral reflectance of 1mm thick composite samples against white and black backgrounds were measured both before and after curing, and were converted to scattering and absorption coefficients using the Kubelka-Munk Theory. Both for pre and post-curing dental resin composites, the Albedo coefficient (K/S) shows that absorption prevails over the scattering for short wavelengths while for medium and large wavelengths, the scattering becomes more important, except for the T shade of the nanocomposite. After curing, the scattering and absorption values decreased for both types of materials. Changes in the absorption coefficient values should be caused by changes in the camphorquinone (CQ) absorption, whereas the scattering changes found should be directly attributable to index of refraction changes of the resin during curing.

In this work we describe a setup employed for the recording of vertical dispersive holographic screens that can be used for medical applications. We show how to obtain holographic screens with areas up to 1200 cm², focal length of 25±2 cm and diffraction efficiency of 7.2%. We analyze the technique employed and the holographic screens obtained. Using this screen we describe a setup for the projection of Magnetic Resonance or Tomographic Images. We also describe and present the first results of an autostereoscopic system for 3D medical imaging.

The FBGs (Fibre Bragg Grating) are adequate sensors for measuring strain in biomedical applications. This work evaluates the efficacy of some products and processes, which are used for the decontamination and sterilization of these sensors. Fibre optic samples, partially stripped of the primary coating, were contaminated by E. coli and S. aureus and suffered decontamination processes by autoclave heating, immersion in ethylene oxide, sodium hypochlorite, chloramine T or peracetic acid and illumination ultra-violet radiation. After each process fibre samples were removed, washed in sterile saline and placed individually in BHI broth tubes. Tubes that showed turbidity of the BHI broth were considered positive. The sterilization practices by heating and immersionand avoided the formation of bacteria colonies, whereas illumination processes were not effective to avoid the bacteria colony growth.

Nowadays, cataract extraction with IOL implantation aims not only to restore the crystalline lens' transparency, but also to improve patients' retinal image quality. The refractive outcome and visual quality in pseudophakic eyes is mainly determined by the combination of corneal and internal optics resulting from the implanted IOLs. The optical function of the IOLs depends on its position in the eye. The IOL distance to the corneal apex determines the optical power needed for optical correction. In this paper it is described the usage of a slit-scanning imaging system to determine IOL positioning. Through the projection of the light from a slit onto the eye, this tomography system allows to acquire multiple sections of the anterior eye segment, at different meridians. The developed system's software corrects geometric and optical distortion of the images and provides 3-dimentional models of the eye's structures from the 2-dimensional sections. With this noninvasive technique, cross-sectional images of an eye with an aphakic IOL were obtained in order to reconstruct its 3- dimensional model of the lens and assess its position in the anterior segment camera.

We develop a computational model to analyze the effect of scattering on image formation in the human eye with cataracts. With this model we compare the scattered light on the retina and in the exit pupil of the eye and find significant differences in the effects observed. We found that the effect of scattering due to the retina reduces the effect of scattering due to cataracts in the second pass, and the most important parameter that affects scattering is the size of the particles.

The aim of this method is to determine the thickness of a transparent medium, close to the corneal thickness, using the angle at the first and second Purkinje images are aligned for a specific optical slit width. An optical slit is projected in an oblique angle relatively to the transparent medium, producing two different reflections in each medium surface (first and second Purkinje images). The slit is then moved until the first and second Purkinje images of the slit are aligned in such a way, that look as if they were a continuous slit. The slit width, the angle between the illumination and observation, and the medium index are used, then, to calculate the medium thickness. This method was implemented in a slit lamp and the central thicknesses (CT) of nine gas-permeable contact lenses (CL) were measured, with this method and a mechanical gauge and the results were compared. The mean CT difference ± standard deviation, between the two methods was 0.004 ± 0.008 mm with minimum and maximum absolute values of 0.002 and 0.019 mm. This technique showed good precision to measure the CT of CL and should be tried in human corneas.

The main purpose of this work is to study the influence of the holding setups commonly used to measure the aberrations of crystalline lenses. Measurements for bovine lenses were performed with a point diffraction interferometer when the crystalline lens leans in the bottom of a glass cell filled with some preserving solution and when the lens leans over a ring placed in the glass cell in order to avoid the contact of the lens with the cell. Significant changes were found not only for symmetric aberrations but also for non symmetric ones.

The aim of this work was to find out if differences exist in accommodative and convergence response for different computer monitors' and a printed text. It was also tried to relate the horizontal heterophoria value and accommodative response with the symptoms associated with computer use. Two independents experiments were carried out in this study. The first experiment was measuring the accommodative response on 89 subjects using the Grand Seiko WAM-5500 (Grand Seiko Co., Ltd., Japan). The accommodative response was measured using three computer monitors: a 17-inch cathode ray tube (CRT), two liquid crystal displays LCDs, one 17-inch (LCD17) and one 15 inches (LCD15) and a printed text. The text displayed was always the same for all the subjects and tests. A second experiment aimed to measure the value of habitual horizontal heterophoria on 80 subjects using the Von Graefe technique. The measurements were obtained using the same target presented on two different computer monitors, one 19-inch cathode ray tube (CRT) and other 19 inches liquid crystal displays (LCD) and printed on paper. A small survey about the incidence and prevalence of symptoms was performed similarly in both experiments. In the first experiment, the accommodation response was higher in the CRT and LCD's than for paper. There were not found significantly different response for both LCD monitors'. The second experiment showed that, the heterophoria values were similar for all the stimuli. On average, participants presented a small exophoria. In both experiments, asthenopia was the symptom that presented higher incidence. There are different accommodative responses when reading on paper or on computer monitors. This difference is more significant for CRT monitors. On the other hand, there was no difference in the values of convergence for the computer monitors' and paper. The symptoms associated with the use of computers are not related with the increase in accommodation and with the horizontal heterophoria values.

Purpose: White light optical profiling (WLOP), no usually applied to contact lenses (CL), is a well-established technique for non-contact measurement of surface topography over large areas at moderate lateral and high vertical resolution (sub-nanometer). The aim of this study is to analyze surface properties of five hydrogel CL evaluating representative roughness parameters as Roughness Average (Ra) and Root-Mean-Square Roughness (R_q), that depend on the sampling length, obtained by WLOP. Methods: Lenses used in this study were two highly biocompatible CL and three silicone-hydrogel CL. Unworn CL surface roughness and topography were studied with WLOP (Wyco NT1100) in VSI mode (Vertical Scanning Interferometry). 50X and 20X objectives were used. Height roughness parameters R_a and R_q were calculated for 625, 2500, 10829 and 67646 μm² areas using the WycoVision®32 analytical software package. Results: High quality 3D topographic images were recorded at randomly different surface locations. Surface topography and Ra and Rq show different values depending on the contact lens and the measurement areas, with the highest roughness scores in biocompatible CL (R_a/R_q for 625, 2500, 10829 and 67646 μm² areas were: Hioxifilcon 31,04/40,07 - 32,88/44,94 - 42,26/61,54 and 47,88/63,24; omafilcon A 17,61/22,41 - 22,18/28,20 - 49,84/65,98 and 67,12/89,37; senofilcon A 14.47/18,65 - 14,79/18,84 - 12,62/16,09 and 35,93/46,61; comfilcon A: 9,58/11,93 - 14,70/18,42 - 12,17/16,21 and 38,81/51,13; balafilcon A: 7,60/9,69 - 16,30/20,84/ - 9,77/12,83 and 24,19/32,09). Higher roughness parameters were obtained for larger areas in all lenses. Conclusions: Highly biocompatible CL presented the highest roughness surface. WLOP provides useful information about contact lens surface measuring larger areas than other techniques used before.

We have studied the intrinsic variability of color coding by examining the temporal fluctuations of chromatic-opponent neurons at the large scale. Simple reaction times were measured for stimuli selected along the red-green direction in the isoluminant plane of the human color space (S-cone constant or L-M axis). Stimulus size also changed from 8 minutes of arc to 10 degrees. Fluctuations increased as the mean reaction time increased and showed a bi-linear scaling function. The coefficient of variation was always lower than predicted by a Poisson process. The variability decreased as a function of the chromatic contrast and as a function of the stimulus size. The analysis of the hazard functions was consistent with power-law dominant random processes at low stimulus size and low contrasts and log-normal dominant processes at high contrasts. Our results conclude that response variability is signal-dependent and evidence for a random multiplicative process in human color vision. We suggest that multiplicative internal noise modulates red-green spatial summation and chromatic contrast processing and may represent a fundamental limit in spatially disordered networks.

In this work, a polymeric sensitive layer based on the acid-base equilibrium of phenol and of its derivative p-nitro-phenol is presented for carbon dioxide measurements. Thin films casted on glass slides were tested, using a LED source (λc at 410 nm) and an Ocean Optics USB4000 spectrometer, in the 0% to 15.25% CO₂ concentrations range, showing a 40% maximum transmittance variation with a 51s response time and a 0.15% resolution. Preliminary results indicate that CO₂also induces refractive index changes in the sensitive layer. Using a fiber based interferometric setup, a CO₂ dependent refractive index change of ~0.045 RIU was observed, in the 0%-90% CO₂ concentration range.

In this paper, we present the numerical simulation of the Be deposition phenomena using the Thermionic Vacuum Arc (TVA) method. The Be marker layer must be adherent to the substrate and compact to resemble bulk beryllium. Thermionic Vacuum Arc (TVA) is an externally heated cathode arc which can be established in high vacuum condition, in vapors of the anode material. The arc is ignited between a heated cathode provided with a Whenelt cylinder and the anode which is a crucible containing the material to be evaporated [1]. We have used the COMSOL software to simulate the Be deposition phenomena using the TVA method.

We describe in this paper a pilot experiment of optimization of a white-light source for a low-coherence interferometry. The white-light source combines the light beams generated with colour LEDs. By modelling of the white light spectra, a contrast of a white light interference fringe could be changed and set to the maximal value. The second part of this paper is a description of a white-light fringe analysis ensured with a low-cost colour CCD camera. The used detection technique employs a phase-crossing algorithm which identifies a zero optical path difference as the point where the phase difference between the red, green and blue part of the white-light interference fringe becomes equal to zero. The optimized white light source is designed to be a crucial part of an experimental setup for the surface diagnostics and automatic calibration of gauge blocks.

Transmission properties of bidimensional arrays of dielectric spheres are highly dependent on the size and the refractive index of the spheres and on the compactness of the array. In this paper we present the design of filters in the infrared part of the spectrum based on microspheres with high refractive index values. The design and optimization of the filters are performed using two methods: computer calculations with FDTD software and building and measuring macroscopic models of the system, in the microwave regime. We propose the design of filters of practical interest in buildings, able to remove infrared through windows, the frequencies that belong to temperatures above 25 °C.

Lateral chromatic aberration or lateral color refers to the change in image position with wavelength, and so to the change in magnification, at the image plane of an optical system. In an imaging spectrometer, this introduces a slop and/or curvature in the spectral image line of an object point, a feature that is known as keystone. The variation in keystone when the spectrometer is illuminated with and without the optical system under test allows measuring the lateral chromatic aberration in a wide spectral band.

Saccharomyces cerevisiae morphology is known to be dependent on the cell physiological state and environmental conditions. On their environment, wild yeasts tend to form complex colonies architectures, such as stress response and pseudohyphal filaments morphologies, far away from the ones found inside bioreactors, where the regular cell cycle is observed under controlled conditions (e.g. budding and flocculating colonies). In this work we explore the feasibility of using micro-fiber optics spectroscopy to classify Saccharomyces cerevisiae S288C colony structures in YPD media, under different growth conditions, such as: i) no alcohol; ii) 1 % (v/v) Ethanol; iii) 1 % (v/v) 1-butanol; iv) 1 % (v/v) Isopropanol; v) 1 % (v/v) Tert-Amyl alcohol (2 Methyl-2-butanol); vi) 0,2 % (v/v) 2-Furaldehyde; vii) 5 % (w/v) 5 (Hydroxymethyl)-furfural; and viii) 1 % (w/v) (-)-Adenosine3', 5'cyclic monophosphate. The microscopy system includes a hyperspectral camera apparatus and a micro fiber (sustained by micro manipulator) optics system for spectroscopy. Results show that micro fiber optics system spectroscopy has the potential for yeasts metabolic state identification once the spectral signatures of colonies differs from each others. This technique associated with others physico-chemical information can benefit the creation of an information system capable of providing extremely detailed information about yeast metabolic state that will aid both scientists and engineers to study and develop new biotechnological products.

The thermo-sensitive phase transition behavior of linear copolymers based on N-isopropylacrylamide and acrylamide (poly(NIPAAm-co-AAm)) has been studied by means of ATR - FTIR spectroscopy. The investigations were carried out in aqueous solution or different phosphate buffer systems (pH = 7.4). The variables here were the comonomer ratio in the copolymers, the copolymer concentration in the solution and the ionic strength of the solvent. Increasing the ratio of AAm in the final copolymer composition produced a large shifting of the lower critical transition temperature (LCST) towards higher values, as a well as a broadening of the phase transition domain, regardless the solvent type.

Stress caused by increase population density in maize produce significant yield loss. To remedy it, photosynthetic activity maintenance even under unfavorable conditions is required. Senescence delay induced by stress in stay-green genotypes (SG) could contribute to maintaining photosynthetic capacity. In this work we observed differences in reflectance curves of two hybrids (SG and no SG) when population level increased. Significant differences in chlorophyll absorption spectral region were observed. Therefore spectral signatures studies maize could help to understanding of the physiological basis of SG character to predict the growing conditions in which these hybrids would express their production potential.

Some pyridazinium ylids used as precursors in obtaining pulmonary active drugs were studied from the point of view of intermolecular interaction nature in different solvents. The solvatochromic effect in solvents with different physicalchemical properties was used to establish the nature of the intermolecular forces acting on the pyridazinium ylid molecules in binary solutions. In the aprotic solvents only universal interactions were emphasized, while in the protic ones a supplemental hypsochromic shift of the visible electronic band proves the existence of specific interactions. The supply of different kind of interactions in pyridazinium ylid solutions was also estimated.

We show how confocal microscopy can be used as a simple, fast and flexible technique to fabricate multiple diffractive masks on a single plate. These masks are useful to make full bandgap photonic crystals with a woodpile structure in a single illumination step. The versatility for the control of the confocal microscope allows to define the illumination area and codify the features of the diffractive mask in a simple and straightforward way. The period of the diffraction grating can be easily established by modifying the illumination area. This allows to control the dimensions of the woodpile structures and consequently the bandgap spectral range of the fabricated structures.

Optical response of a system of (nearly) identical polarizable particles, coupled by electromagnetic interactions is studied theoretically addressing the following question: Is it possible to extract information concerning the spatial correlations in the particles' positions from the experimentally measurable optical response of the system? The relation between the spectral-dependent solutions of the coupled-dipole equations and the type and parameters of the particle-particle correlation function in real space is analyzed. The physical system considered is a collection of metallic nanoparticles distributed over a square or cubic lattice in a random-correlated way, relevant to metaldielectric composites interesting for nanoplasmonics. We show that it is possible to propose a numerical criterium that allows for conclusion concerning the degree of correlation in the particle positions using the (experimentally measurable) extinction spectrum of the system.

In this work we develop an analysis of polarization control schemes suitable for quantum key distribution systems. Both time division multiplexing and wavelength division multiplexing based schemes are considered. A model for the optimization of the temporal separation between reference pulses and polarization encoded photons is presented. The model accounts for the reference pulse shape, the single photon detector gate width, and the respective temporal separation between them. The theoretical results are validated through experimental measurements. These results can be used to optimize the performance of polarization control schemes and therefore to optimize the polarization encoded quantum key distribution systems.

The paper considers results of designing and modeling analogue-digital converters (ADC) with continuously logical functions (CLF), namely equivalently (nonequivalently) functions. Such ADC, named us complementary - dual equivalently (CDE ADC). Compared with usual converters, for example, reading, a bit-by-bit equilibration, and so forth, have a number of advantages: high speed and reliability, simplicity, small power consumption, the big degree of integration in linear and matrix files. The considered aspects of designing of CDE ADC in an initial binary code will be us Gray. Base digit cells of such CDE ADC, series-pipelined are connected in structures, consist from 23 CMOS the transistors, one-two photo diodes, have low (1,5-3,5) supply voltage, work in current modes with the maximum values of currents (10-40 μA). Therefore such new principles of realization high-speed low-discharge ADC have allowed, as have shown modeling experiments, to reach time of transformation less than 20-30 nS at 5-6 bits of a code Gray and the general power 1-5 mW. CDE ADC open new prospects for realization linear and matrix (with picture operands) micro photoelectronic structures which are necessary for neural networks, digital optoelectronic processors, neurofuzzy controllers, and so forth.

Many optical systems need to be evaluated but they cannot be disassembled to test the imaging lens separately. Then, they have to be tested in a retroreflecting configuration, frequently called double-pass. A typical example of this procedure is in the optical eye. In this manuscript we will describe the different possibilities that might exist when these tests are performed. The main differences are due to the different optical properties of the surfaces on which the image is formed. We will describe the different system conditions and how they can be evaluated and implemented.

With the aim of contribution to the study of atmospheric ozone layer, a new sensitive radiometer for atmospheric minor constituents has been installed in the Observatorio Atmosférico de la Patagonia Austral, División LIDAR, CEILAP (CITEDEF-CONICET), in October 2010. This observatory is established in the city of Rio Gallegos (51° 36' S, 69° 19' W), Argentina, close to the spring ozone hole. The millimeter wave radiometer was developed in STEL (Solar Terrestrial Environment Laboratory), Nagoya University, Japan. This passive remote sensing instrument is able to measure the ozone (O₃) amount in the high stratosphere and mesosphere continuously and automatically with a high time resolution. The millimeter wave radiometer ozone profiles will be supplemented with the ozone profiles obtained from the DIAL system existent in the observatory. The millimeter wave radiometer is based on the spectral signal detection from the atmosphere due to the molecular rotational transition of molecules under study. The operation is based on a superheterodyne system which uses a Superconductor-Insulator-Superconductor (SIS) mixer receiver operating at 203.6GHz. The SIS mixer junction consists of a sandwich structure of Nb/AlOx/Nb, and is cooled to 4.2K with a closed cycle He-gas refrigerator. Two additional heterodyne-mixed stages are realized with the aim to shift the measured spectral line until a frequency around of 500 MHz. A FFT (Fast Fourier Transform) spectrometer system is used as a back end. The aims of this work are to show the potential of the millimeter wave radiometer installed in the subpolar latitudes close to the polar ozone hole and to present the preliminary result of the first measurements.

Present studies report step by step analysis, theoretical as well as experimental along with simulations, of evaluating the output Jones matrix for different experimental configurations consisting of combination of polarizers and waveplates at different orientations using Jones calculus. This development is an attempt to ease the polarization studies using Jones calculus through sensors, data acquisition and analysis tools. The studies provide an extensive laboratory exercise through hands-on as well as computer simulations to the undergraduate students to comprehend various concepts related to polarization.

In this work, we present results of broadband emissions ranging from 800 to 1500 nm generated by using Photonic Crystal Fibres (PCFs) made from borosilicate glasses. The borosilicate PCFs, fabricated by the Stack-and-Draw technique, consist of five hollow ring periods around the solid core. The solid core is based on the lead-doped borosilicate glass. The PCFs with their external diameters ranging from about 3.8 to 6 microns were excited with a commercial pulsed diode laser (wavelength at 1065 nm, Power <100mW). The PCF length used to generate broadband emissions was less than a meter. The Optical Attenuation of these PCFs was measured via the Cut-Back method and their Dispersion Spectra were calculated by using the Finite Element Method (FEM) and the scanning electronic microscope images. Finally, we believe that short borosilicate PCFs with lead-doped cores (related to high non-linear properties) may be used in broadband emissions, supercontinuum generations or other non-linear applications.

In this work, a high-birefringent Sagnac loop interferometer torsion sensor is presented. The sensing head is inserted between the output ports of a high-birefringent coupler and it is formed by a section of standard single mode fiber. The sensing head characterization is done for torsion, temperature and strain measurements. The spectral response of this sensing head presents two interferometers, which are dependent on the light polarization states. Interference occurs due to the different lengths of the coupler output arms. This configuration allows the exclusion of a polarization controller, since it is possible to manipulate directly the polarization of light that travels inside the coupler. When the sensing head is subjected to torsion, it is possible to observe a beat between the two interferometers. In this case, there is a simultaneous π/4 excitation of the two polarization states in the splices region. The torsion sensitivity is related to the sensing head length. The sensor response is periodic and the twist range can be from -2π to 2π. The sensor is unaffected by temperature and strain variations. This configuration is simple and when compared to the conventional configuration, the polarization controller is suppressed. The setup can be used in specific applications, such as in mechanical engineering.

A fiber optic FBG cladding modes based sensor, for simultaneous measurement of strain and temperature is presented. The FBG cladding modes are efficiently excited by the large core misalignment. This technique enables the possibility to readout simultaneously in reflection the cladding mode (λ_cl) and the core mode (λ_co). λ_cl, λ_co depend on strain and temperature and show different sensibilities for each parameter, enabling their discrimination. The experimental result shows a good performance in terms of linearity and sensitivity.

The underground movement of water through soil and rock is an important phenomenon in Civil Engineering. Its study is made more appealing to students if small scale prototypes are used, where several layouts of soil and water in steady state/transient conditions can be studied in detail. A water tank prototype was built with a reflective optical fibre pressure sensor based on a GRIN lens and a mirror. The mirror is connected to an elastic membrane that is deformed when water pressure is applied and the lens is correctly aligned with the mirror and fixed. The distance between the mirror and the lens changes, so the reflective optical power changes as well and it is directly proportional to the water pressure inside the tank. The results obtained for water pressure up to 4 kPa for filling and emptying operations show that the sensor has a linear response for pressure changes between 1.7 kPa and 3.4 kPa with a slope of 181 μW/kPa for filling and 191 μW/kPa for emptying. It is also observed some hysteresis that may possibly be reduced by choosing another material for the membrane. Using this type of sensor head it is possible to monitor different pressure points in the small scale prototype using the standard OTDR (Optical Time Domain Reflectometer) equipment.

A single-photon source based on the stimulated four-wave mixing (SFWM) process in optical fibers is presented. At the output of the source, the state of polarization (SOP) of the photons can be adjusted in order to obtain any linear polarization. A theoretical model to describe the average photon counts recorded in the avalanche photodiodes (APDs) is presented. The experimental results show an accurate detection of two non-orthogonal linear SOPs after propagation through a 60 km quantum channel, and good agreement with theory. This source, operating in a low power regime, can be used for quantum key distribution (QKD) using polarization-encoding in quantum communications.

A Brillouin Stokes comb laser with increased flatness is reported. The feedback for the laser is provided by a distributed mirror combined with a narrowband seed laser. The Brillouin seed power and wavelength optimization is crucial in order to obtain a uniform power level between Stokes lines. The Brillouin seed must have a relatively large power and its wavelength must be located close to the Raman peak gain region. The flat-amplitude bandwidth is also determined by the choice of Raman pump wavelength. A flat-amplitude bandwidth of 34 nm from 1538 nm to 1572 nm is measured when Raman pump wavelength is set to 1455 nm. 425 uniform Brillouin Stokes lines with 0.08 nm spacing are generated across the wavelength range. The average signal-to-noise ratio of 15 dB is obtained for all the Brillouin Stokes lines. This type of laser can be used in optical communications as a multiwavelength source and also in metrology as a frequency ruler.

An encapsulated fiber optic sensor head for the detection of level of fuel in a tank is presented. The design is based on a concentric cam used along with a float and extrinsic intensity modulation of light. The sensor has been tested for its performance to measure a fuel level range of 35cm and a sensitivity of 0.2316 volts/cm was observed during rise in fuel level. The sensitivity and range of level sensing can be varied by varying the length of the connecting rod.

Optical fibre sensors for Hydrogen detection at low concentrations has become a growing research area using Palladium as an active medium. Palladium is widely used in hydrogen sensing as it show a high and selective affinity for hydrogen. This metal is capable to absorb hydrogen up to 900 times its own volume which permits that during the expansion mechanical forces are applied in the fibre modifying the optical response. Several optical fibre hydrogen sensor heads coated with Palladium are presented and compared using different working principles: interferometric, intensity and fiber grating-based sensors. These principles were applied in Fabry-Perot cavities, fibre Bragg gratings written in fibre SMF28 with etching in the cladding, multimode interferometers and fibre end micro-mirrors. Palladium thin film coatings over the fibre surface and with thicknesses from 10nm to 350nm were produced by using the sputtering RF technique. These studies were performed in a Hydrogen/Nitrogen atmosphere with Hydrogen concentrations from 0% to 4% (lower limit explosion). The Bragg grating inscribed in a fibre with reduced cladding diameter appears to be one of the best approaches for a fibre optic sensing head for Hydrogen detection. Future work will continue the investigation of other fibre optic structures with Hydrogen sensing capabilities and their application in specific field situations will be assessed.

Towards the development of new optical fiber sensors it was studied the application of nanosecond infrared laser radiation in the micropatterning of optical fibers. Nd:YAG laser pulses were focused on silica fibers by an apparatus projected to position the fiber regarding the laser beam and analyze the interaction. Experiments allowed determining the conditions to vaporize the required amount of material. Holes with few microns and depths higher than 10 microns were accomplished with multiple shots and advancing the fiber regarding the beam's focus. The results analysis demonstrated the possibility of obtaining patterns and the technique potential in the development of fiber sensors.

In this paper, two novel hybrid multimode/single mode fiber Fabry-Pérot (FP) cavities were compared. The cavities fabricated by chemical etching are presented as high temperature and strain sensors. In order to produce this FP cavity a single mode fiber was spliced to a graded index multimode fiber with 62.5 μm core diameter. The multimode fiber was cut approximately 150 μm away from the splice. Then the tip of the fiber containing the multimode fiber segment was dipped into a solution of 48% of HF during 8 minutes, creating a concavity due to the fact that the reaction between HF and the germanium doped fiber core is much faster than the reaction between HF and the pure silica cladding. By this method a concavity of approximately 100 μm deep was created at the fiber tip. Two different FP cavities can be fabricated. The first cavity is obtained when a spliced with an identical tip concavity fiber (Sensor A) and the second is created when a tip concavity is spliced to a single mode fiber (Sensor B). The Fabry-Perot cavities were tested as a high temperature sensor in the range between room temperature and 800°C and as strain sensors. A reversible shift of the interferometric peaks with temperature allowed to estimate a sensitivity of 0.75 ± 0.03 pm/°C and 0.98 ± 0.04 pm/°C for the sensor A and B respectively. For strain measurement sensor A demonstrated a sensitivity of 1.85 ± 0.07 pm/με and sensor B showed a sensitivity of 3.14 ± 0.05 pm/με. The sensors demonstrated the feasibility of low cost fiber optic sensors for high temperature and strain.

Sensors based on side-polished plastic optical fibre are presented. To enhance the sensitivity to a certain physical parameter, the guiding properties of an optical fibre have to be weakened. Side-polishing technique offers a simple implementation, since the mechanical resistance of the POF allows an easy removal of a portion of the jacket, cladding and core. Three sensors are characterized under a wide range of external refractive indexes. Both, theoretical and experimental results show that the range of operation of the refractive index sensor can be shifted by using different geometries or different macrobending conditions of the sensitive area. The phenomenon behind the principle of operation of the sensor is the reflection and transmission of light at an interface of two dielectric media expressed by Fresnel's equations. The use of this intrinsic scheme to monitor the cure process of a material or the viscosity of a liquid is also presented. The changes in refractive index are used to monitor, in real time, the cure of different materials such as resins and varnishes because the optical properties of the material can be related to the density of the material. The viscosity of a liquid is related to the droplet formation in a convexly bended sensor.

In this work, we present a simple approach to design a multichannel sampled fiber Bragg grating (SFBG) for dispersion compensation, based on groups of SFBG with phase modulation between groups. We present also an apodization technique that minimizes the high group delay ripple that occurs with this approach. This design can be implemented with a uniform phase mask and a low resolution positioning device.

A single-mode non-adiabatic tapered optical fiber (NATOF) sensor was inserted into a Sagnac loop interferometer allowing tuning its sensitivity to refractive index (RI) by use of polarization control. By adjusting any polarization controllers inserted in the Sagnac loop interferometer, various cladding modes are selectively excited in each arm of the interferometric taper resulting into different phase changes for the clockwise and counterclockwise beams. By this method, sensitivity of the sensor for RI in the range from 1.3380 to 1.3510 was tuned between 876.24 RIU/nm to 1233.07 RIU/nm.

The development of an interferometric optical fiber inclinometer is described in this paper. A weak tapered region is induced in a standard single mode fiber in the vicinity of the cleaved fiber tip, using a standard fusion splicer. In this situation an in-fiber Michelson interferometer is constructed that is sensitive to curvature applied in the tapered region. It is shown that depending on the angular range, fringe visibility and/or peak position depend strongly on the applied curvature enabling low cost dielectric inclinometer to be setup that is suitable for high voltage applications. It is presented an analysis of the sensor response by means of experimental measurements and manipulation of these experimental data through computational simulations. The results coming from the numerical simulations indicate a good performance of the sensor within range of angular variation between 3 and 6 degrees and 10 and 14 degrees. A low cost strategy to interrogate the response of sensor using electrically modulated fiber Bragg gratings, a photodetector and frequency analysis is described. The results presented by this electric interrogation technique show a good sensitivity in the range 3.5 to 5.5 degrees.

In this work, we analyze a remote optical sensor system composed of two Fiber Bragg Gratings (FBGs) and one Long Period Grading (LPG) capable of simultaneously sensing the temperature and the refractive index, separated by 50 km from the optical source and the interrogation unit. Since the active components of the system and the sensor head are separated over such a large distance, it is necessary to consider Raman amplification o strengthen the optical signal. We present both experimental measurements and the results of numerical simulations, which describe the signal evolution and predict the measurement results for a remote sensor based on a LPG. The simulation codes are also used to study a hybrid sensor composed of two FBGs with a LPG. We show that the power ratio between the two central wavelengths of the FBG has a linear relation with the change of refractive index of the sensored medium.

Conjugated luminescent polymers have been shown to exhibit stimulated emission under optical pumping. Dilution in polymethylmethacrylate (PMMA) leads to an enlargement, towards longer wavelengths, of the gain region. In addition, ultrafast optical switching is observed when a second pulse is applied during excited state lifetime. These two properties are of high importance for optical communications and can bring to the plastic optical fibres (POFs) the equivalent of erbium amplification in silica fibres. In this communication we report on the gain and switching properties of PMMA films and POFs doped with conjugated oligomers and polymers, prepared by blending or copolymerisation. The dopants were functionalised with polar side groups to improve their solubility in MMA and/or with reactive methacrylate groups so they can be copolymerised with MMA.

In this work, the structural health monitoring of a self-supported steel tower with 50 meters high used for mobile communications are presented. For this test, a fiber Bragg grating based biaxial horizontal accelerometer was used to obtain the structure frequencies. The frequencies for the first resonant modes were obtained from the acceleration data recorded over time, resulting from the application of mechanical horizontal impulses on the tower. The results shown that the frequencies measured in both directions are within the values expected for this type of structure and can be used to calibrate numerical models that represent their structural behavior.

In this work, a simple real-static nanostrain sensor based on a Bragg grating structure is presented. The setup is constituted by a narrow linewidth laser as light source, an optical circulator and a photodetector. The sensing head is formed by a chirped Bragg grating inscribed in a standard single mode fiber (SMF-28) by the phase technique. The fiber face end is cleaved and coated with a silver mirror, obtaining a Fabry-Perot interferometer. It is observable that the fringes period increases along the grating, due to the chirp spectrum (0.4 nm/cm) characteristics. The laser is fixed in one slope region of the fringe pattern. When strain is applied, the optical power changes linearly. A sensitivity of 5.72 μW/με in a range of 2 με . The sensing head resolution is 70 nε for a measurement step of 875 nε.

This paper presents preliminary results in determining the optimum parameters for graffiti removal in a ornamental granite, Rosa Porriño, by means of Nd:YVO4 laser at the wavelength of 355 nm and different fluences. The spray-paints (black, blue, red and silver) tested in this work were chemically characterized by means of elemental analysis, XRF, SEM/EDX and FTIR. The assessment of cleaning and characterization of the stone substrate before and after irradiation was performed by means of optical microscopy, SEM-EDX, and confocal microscopy. The analysis of the irradiated samples showed in some cases, damage in the granite substrate associated to thermal effects. The severity and kind of damage, depends on the laser fluence delivered, the constituent mineral irradiated, and the color used to paint the stone. So, at the highest levels of fluence the laser beam is able to scratch the surface, being the depth of the grooves in the stone measured by confocal microscopy. Moreover, SEM images show the differential damage caused in mineral constituents of granite i.e., quartz, feldspars, and biotite, the latter providing to be the most affected mineral, reaching melting even at low levels of fluence. It was appreciated that the color of the spray-paint affects the results of cleaning, and observed differences could be attributed to different organic constituents in the paints or the presence of metallic particles in its composition, as occurs with silver paint.

Conventional LED based illuminating systems for microscopes are either ring illuminators or expensive fiber optics based sources to input the light at the conventional places. Here we describe a different design strategy that leads to a compact, economical, relatively cool and more versatile source that is usable in the transmission as well as the reflection configuration; the module can be easily configured for discrete wavelengths for fluorescence markers and thus is suitable for biology related applications. We show the performance characteristics of the module that we have developed. Comparison measurements show that led based source that we have developed has adequate homogeneity of the illumination field, white leds lead to better contrast and use of narrow band leds have significant advantages over the conventional approach in fluorescence microscopy applications.

Since the first reported Nd:YAG solar laser, researchers have been exploiting parabolic mirrors and heliostats for enhancing laser output performance. We are now investigating the production of an efficient solar-pumped laser for the reduction of magnesium from magnesium oxide, which could be an alternative solution to fossil fuel. Therefore both high conversion efficiency and excellent beam quality are imperative. By using a single fused silica light guide of rectangular cross section, highly concentrated solar radiation at the focal spot of a stationary parabolic mirror is efficiently transferred to a water-flooded V-groove pump cavity. It allows for the double-pass absorption of pump light along a 4mm diameter, 30mm length, 1.1at% Nd:YAG rod. Optimum pumping parameters and solar laser output power are found through ZEMAX^TM non-sequential ray-tracing and LASCAD^TM laser cavity analysis. 11.0 W of multimode laser output power with excellent beam profile is numerically calculated, corresponding to 6.1W/m² collection efficiency. To validate the proposed pumping scheme, an experimental setup of the double-stage light-guide/V-groove cavity was built. 78% of highly concentrated solar radiation was efficiently transmitted by the fused silica light guide. The proposed pumping scheme can be an effective solution for enhancing solar laser performances when compared to other side-pump configurations.

Incoming solar energy is firstly collected 137 small parabolic mirrors, 180mm in diameter, 210mm in focal length and then coupled by 137 optical fibers with 2mm in diameter each, to a diffusion bounded thin-disk Nd:YAG laser material. The flexibility of optical fiber allows the placement of laser cavity in a convenient place away from the solar collection mirrors. The conical polishing of the fiber output sections permits further enhancement of pump light absorption by the Nd:YAG thin-disk, diffusion bounded to an undoped YAG cap with 80mm maximum diameter. For optimal pumping condition with 1.8mm diameter polished tip, 20W laser power was numerically calculated, corresponding to a collection efficiency of 5.9 W/m². M² factors of M_x2=88.5 and M_y2=89.4 were also attained, indicating an almost symmetrical absorption profile. The proposed scheme can provide a solution to the thermal problems that has plagued the solarpumped lasers for many years.

Here we numerically demonstrated that the phase profile of a given temporal optical pulse can be retrieved by photonic semi-differintegration, where by semi-differintegration we mean either a 0.5th-order differentiation or integration. In both cases, the signal's temporal phase can be obtained by simple dividing two temporal intensity profiles, namely the intensities of the input and output pulses of a spectrally-shifted semi-differintegral. In both cases, we obtained simple analytical expressions for the phase profile. We numerically prove the viability of these proposals.

We describe the design and implementation study of a high dynamic range, third order contrast-ratio measurement diagnostic for a high power laser chain. The device, known as Optical Parametric Amplification Correlator (OPAC) is based on degenerate three-wave mixing in a nonlinear crystal, it is self-referencing and compact. By measuring the idler pulse with a slow detector and a set of calibrated filters, a dynamic range of up to 10¹⁰ is achievable. The pulse contrast is to be characterized at the mJ-level, 10 Hz, Ti:sapphire pre-amplifier stage, in a time window of 100 ps.

Optical microscopy as a means to identify graphene is hampered by the low absorptivity of its monolayers and few-layer structures. However for many of the upcoming applications for graphene, it is essential to develop techniques to readily deliver images of graphene based structures. We report on two novel techniques and additionally on a well-known, but modified technique for the identification of graphene. All of the described methods employ standard optical reflection and transmission microsocopy and can be readily adapted in most laboratories. One of the novel techniques is based on the enhancement of the optical contrast by refractive index matching using oil immersion microscopy. The second technique, microdroplet condensation, exploits the hydrophobicity difference between the carbonic sheets and almost any arbitrary substrate. The third technique is a modification of the already well known technique to enhance the visibility contrast of graphene using interferometric effects by employing a Si wafer coated with a dielectric of specific thickness.

Differential Ray Tracing (DRT) is applied to optimize the design of a Schwarzschild objective with large aperture and for arbitrary object position. This optical system lacks of cylindrical symmetry about the non-paraxial base ray, causing astigmatism of a pencil of rays around this ray. The analysis determines the mirror radii ratio that makes the pencil anastigmatic, leading to an excellent image performance. In particular, the classical aplanatic Schwarzschild design is obtained in the limiting case where the base ray becomes paraxial. One example of a design, similar to a typical commercial objective for microscopy, is presented and the image quality is analyzed with an optical design program.

The frequency comb of a femtosecond laser can be used like a ruler for length metrology. This permits measuring absolute distances with direct traceability to the atomic Cesium clock of the time standard. Optical frequency combs have received much attention in recent years due to their enormous potential in optical frequency metrology applications. We have studied an Erbium doped femtosecond fiber laser for applications in optical frequency metrology and found agreement of the measured frequency to within 2x10^-14. It has a number of advantages over other femtosecond lasers due to its greater compactness, longterm operation with less power consumption, compatibility with existing fiber optics and covering of the telecommunication range. With this system, the Spanish Centre of Metrology is establishing a new practical realization of the metre with an improved accuracy in two orders of magnitude with respect to the current system based on iodine stabilized lasers.

We perform an accurate numerical modelling of both tapered and microstructured fibers using a finite element numerical approach. We compute the propagation modes, i.e., distribution of the electric field over the cross section, effective modal area and dispersion characteristics. The dependence of the dispersion properties on wavelength are calculated by solving the eigenvalue equation for fiber modes and using Sellmeier equation. The optical properties of tapered fibers are shown to be very sensitive to the core size. The zero dispersion wavelength can be shifted to the visible range and, in some cases, two zero dispersion wavelengths are observed. The dependence of the dispersion properties and of the effective mode area of a microstructured fiber with hexagonal symmetry on the air-hole diameter and the hole-to-hole spacing is also investigated.

In this work we present bend loss characteristics of silica Photonic Crystal Fibers (PCFs) in the VIS-NIR-IR region. The PCFs made using the Stack-and- Draw technique consist of triangular and rectangular hollow lattices. The bend loss dependency of these PCFs was characterized by using an optical spectrum analyzer (OSA) and a white light source. The optical transmittance spectra were measured for different bend radius. These PCFs are sensitive to bending losses in the VIS-NIR region, but insensitive in the IR region. These PCFs may be used to bend sensors or optical filters.

This article discusses a kind of Digital Ion Trap Mass Spectrometry. This system is based on the DSP/MCU controllers and a D/A converter and a special transformer and a power amplifier and an avalanche photodetector. It can get a higher precision and very exact voltage for measurement. Because it changes low voltage to ±250V in the end by transformer and no switches to turn on and turn off, therefore there is no EMI/EMC disturbs, and system has a small volume. We also can make a higher voltage system such as ±1000V or ±2000V following the method we discussed below.