This PDF file contains the front matter associated with SPIE Proceedings Volume 9286, including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

In this paper the authors present a monolithic Photonic Integrated Circuit which includes a transmitter and a receiver for NG-PON2. With this layout it is possible to build an OLT and, by redesigning some filters, also an ONU. This technology allows reducing the losses in the transmitter and in the receiver, increasing power budget, and also reducing the OEO conversions, which has been a major problem that operators want to surpass.

The ability to produce narrow optical pulses has been extensively investigated in laser systems with promising applications in photonics such as clock recovery, pulse reshaping, and recently in photonics artificial neural networks using spiking signal processing. Here, we investigate a neuromorphic opto-electronic integrated circuit (NOEIC) comprising a semiconductor laser driven by a resonant tunneling diode (RTD) photo-detector operating at telecommunication (1550 nm) wavelengths capable of excitable spiking signal generation in response to optical and electrical control signals. The RTD-NOEIC mimics biologically inspired neuronal phenomena and possesses high-speed response and potential for monolithic integration for optical signal processing applications.

We present a calculation of the required number of bits to be received in a system of communications in order to achieve a given level of confidence. The calculation assumes a binomial distribution function for the errors. The function is numerically evaluated and the results are compared with the ones obtained from Poissonian and Gaussian approximations. The performance in terms of the signal-to-noise ratio is also studied. We conclude that for higher number of errors in detection the use of approximations allows faster and more efficient calculations, without loss of accuracy.

In this paper we demonstrate, how fast and slow light phenomena in ring resonator can simultaneously be observed at a single frequency, using strongly coupled ring resonators. We also report on the design of a ring resonator with SOI technology that operate in optical wavelength 1.55 micron and have (one micro-ring) a factor for fast light ~22 picosecond (ps) and a factor for slow light ~12 ps with bandwidth ~100GHz with mixing angle (θ) 30 degrees, however depended on mixing angle and number of rings. Using light in a mixed polarization state, we show that fast and slow light can be obtained from a single incident wave packet. We simulate one micro-ring and extend our result to more micro-ring.

We discuss the development of laser induced fluorescence sensors and their application in the evaluation of water pollution and physiological status of higher plants and algae. The sensors were built on the basis of reliable and robust solid-state Nd:YAG lasers. They demonstrated good efficiency in: i) detecting and characterizing oil spills and dissolved organic matter; ii) evaluating the impact of stress on higher plants (cork oak, maritime pine, and genetically modified Arabidopsis); iii) tracking biomass changes in intertidal microphytobenthos; and iv) mapping macroalgal communities in the Tagus Estuary.

We present a measuring technique for displacement and position sensing over a limited range with detection of standingwave pattern inside of a passive Fabry-Perot cavity. The concept considers locking of the laser optical frequency and the length of the Fabry-Perot cavity in resonance. Sensing of the interference maxima and minima within the cavity along the beam axis has been tested and proven with a low loss photoresistive photodetector based on a thin polycrystalline silicon layer.

Lidar (light detection and ranging) presents better sensitivity than fire surveillance based on imaging. However, the price of conventional lidar equipment is often too high as compared to passive fire detection instruments. We describe possibilities to downscale the technology. First, a conventional lidar, capable of smoke-plume detection up to ~10 km, may be replaced by an industrially manufactured solid-state laser rangefinder. This reduces the detection range to about 5 km, but decreases the purchase price by one order of magnitude. Further downscaling is possible by constructing the lidar smoke sensor on the basis of a low-cost laser diode.

This work reports results from the development of a software to process the parameters involved in the characterization of fiber taper profiles, while using optical microscopy, a high-definition camera and a high- precision translation stage as the moveable base on which the taper is positioned. In addition to this procedure, image processing algorithms were customized to process the acquired images. With edge detection algorithms in the stitched image, one would be able to characterize the given taper radius curve that represents the taper profile when the camera has a sufficient resolution. As a consequence, the proposed fiber taper characterization procedure is a first step towards a high-resolution characterization of fiber taper diameters with arbitrary profiles, specially this case, in which tapers are fabricated with the stepwise technique that allows the production of non- biconical profiles. The parameters of the stitched images depends on the used microscope objective and the length of the characterized tapers. A non-biconical arbitrary taper is measured as an example for the illustration of the developed software and procedure.

We developed a system to investigate resonant nonlinear optical interactions in acetylene molecules, confined in a hollow-core photonic crystal fiber (HC-PCF), using light injection through a low-loss splice from one end of the fiber, allowing us to work at low power. Electromagnetically induced transparency (EIT) was observed in the 1500 nm telecommunications window.

An Ytterbium-Holmium co-doped all-fiber CW laser is reported. The fiber used in the laser setup has been fabricated through the conventional MCVD process in conjunction with the SD technique and finally drawn using a standard fiberdraw tower. The laser was built in a linear Fabry-Perot configuration in which two fiber Bragg gratings reflecting at 2.05 μm were used as the cavity couplers. Under 1.06-μm in-core pumping of the fiber, CW lasing at 2.05 μm was provided due to energy transfer Yb³⁺→Ho³⁺. The laser demonstrated low threshold (~0.8 W), moderate slope efficiency of lasing (~8.4% when measured vs. pump power launched into the active fiber), and high stability: during 6 hours its output power fluctuated within a 3% range. The laser spectrum width at a 3-dB level using an optical spectrum analyzer with a 37-pm resolution was measured to be ~70 pm.

The conversion of sunlight into laser light by direct solar pumping is of ever-increasing importance because broadband, temporally constant, sunlight is converted into laser light, which can be a source of narrowband, collimated, rapidly pulsed, radiation with the possibility of obtaining extremely high brightness and intensity. Nonlinear processes, such as harmonic generation, might be used to obtain broad wavelength coverage, including the ultraviolet wavelengths, where the solar flux is very weak. The direct excitation of large lasers by sunlight offers the prospect of a drastic reduction in the cost of coherent optical radiation for high average power materials processing. This renewable laser has a large potential for many applications such as high-temperature materials processing, renewable magnesium-hydrogen energy cycle and so on. We propose here a scalable TEM00 mode solar laser pumping scheme, which is composed of four firststage 1.13 m diameter Fresnel lenses with its respective folding mirrors mounted on a two-axis automatic solar tracker. Concentrated solar power at the four focal spots of these Fresnel lenses are focused individually along a common 3.5 mm diameter, 70 mm length Nd:YAG rod via four pairs of second-stage fused-silica spherical lenses and third-stage 2D-CPCs (Compound Parabolic Concentrator), sitting just above the laser rod which is also double-pass pumped by four V-shaped pumping cavities. Distilled water cools both the rod and the concentrators. 15.4 W TEM00 solar laser power is numerically calculated, corresponding to 6.7 times enhancement in laser beam brightness.

Non-radiative (Forster-type) energy transfer of an exciton between two quantum dots (QDs) plays an important role in artificial structures where semiconductor nanocrystal QDs play the role of building blocks. We theoretically study the effect of surrounding medium (e.g. dielectric substrate) on the transfer rate. Applying a simple model to describe the QDs, we demonstrate that the transfer rate can be strongly enhanced in the vicinity of a metal surface if the donor QD is excited in resonance with surface plasmons characteristic of this surface. Then the scaling law with the interdot distance becomes more complex than R-6 and the characteristic Forster radius can increase by an order of magnitude. We also show that transfer rate between two QDs is not exactly / R-6 even within the dipole-dipole approximation, in free space if the electron and hole in the dot are in the weak confinement regime

This work we presents a detailed result of Organic Light Emitting Diodes based on europium complex as emitting layer, the tris (dibenzoylmethane) – mono (4,7-dimethylphenantroline) europium (III) – Eu(DBM)₃phen. The electrical d.c. and a.c. behavior is analyzed and correlated with the electroluminescence data. The electroluminescence spectra show the Eu³⁺ ion transitions, with the main emission at 612 nm. The driving voltage is about 20 V although the electrical current is only 0.1 mA (Wall Plug Efficiency up to 4×10^-3 %). Under some conditions, emissions from others organic emitters can be observed. A model considering the charge confinement and the materials energy levels is proposed and discussed.

The uncertainty of a wavemeter has been evaluated taking into account all contributions. This wavemeter was developed to give traceability to the frequency of external cavity diode lasers. These lasers were stabilized and used as light source in the assembly of a new interferometric system for the gauge block calibration. The wavemeter experimental setup is also presented and is based in a Michelson interferometer, a He-Ne laser used as a reference wavelength and a Vernier counter that allowed us to reduce the uncertainty below 1ppm.

In this paper an alternative method of manufacturing SRR structures through the selective removal of a thin layer of silver-palladium deposited on the surface of the Al₂O₃ ceramic by laser ablation process using nanosecond Nd:YAG laser (1064 nm) was presented. The SRR structures array were subject to transmittance measurements using the TDS (Time Domain Spectroscopy). Both electric and magnetic resonances were observed at frequencies determined by the structural parameters of the SRR. In case of the E field perpendicular to an SRR structure and one resonance area for 0.56 THz with the E field parallel to the structure, two characteristic resonant dips for 0.31 THz and 0.62 THz were obtained. Studies have confirmed that using selective laser removal process enables the preparation of the resonant structure in the range of THz.

In this paper, we present some examples of micromachining of poly(L-lactide) with a CO2 laser and an analysis of changes in material properties in the heat affected HAZ induced by the fluence well above the ablation threshold. The complexity of the processes of decomposition implies the need for simultaneous use of many selective analytical techniques which complement each other to give a full image of the changes. Introduced changes were characterized using Differential Scanning Calorimetry (DSC), Gel Permeation Chromatography (GPC), X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared spectroscopy (ATR-FTIR). It turns out that CO2 laser processing of poly(L-lactide) mainly induces surface changes. However, oxidation of the surface was not observed. We recorded a bimodal distribution and some reduction in the molecular weight. Infrared spectroscopy in turn revealed the existence of absorption bands, characteristic for the vinyl groups (RCH=CH2). The appearance of these bands indicates that the decomposition of the polymer occurred, among others, by means of the cis-elimination reaction.

In this work it is presented a study about the ability of multispectral techniques for evaluating in situ, nondestructively, the progress of laser removal of crusts and paints in granitic rocks. For this purpose, granites with different characteristics were cleaned by the third harmonic of a Nd:YVO4 laser, and a multispectral camera was used to monitor the process by recording images of the rock surface during the cleaning. Although preliminary, the results are promising and show that the comparative analysis of the spectra could be used for successfully monitoring the cleaning process. Furthermore, it has been possible to discriminate between black crusts of different nature, biogenic and anthropogenic, by analyzing specific spectral bands.

The irradiation of polylactide by KrF excimer laser with subthreshold fluence results in modification of its properties via photochemical reactions. A common approach is to modify chemical composition of polymer surface by UV irradiation, for example, in order to improve their wetting properties. In this paper, authors present a possibility of bulk modification of poly(L-lactide) which is related to photofragmentation and creation of new terminal groups. The irradiation results in decrease of molecular weight and increase of polydispersity. The appearance of new terminal groups is responsible for enhancement of absorption in UV-C range. The intensity of chemical composition changes introduced by UV irradiation can be precisely dosed thanks to a pulse character of laser source. Modifications can be controlled during the process by the analysis of energy transmitted through a polymer sheet. The distribution of absorption coefficient changes along with the depth of irradiated polymer and its correlation with polydispersity was discussed. Presented technique can be used for selective and controllable modification of hydrolytic degradation time of biodegradable polyesters utilized in biomedical applications.

Laser micromachining systems based on excimer lasers are usually oriented to work with mask projection regime because of the low pulse repetition rate as well as large beam aperture of the laser source. In case of fabricating of the complex 3D structures, this approach introduces a number of limitations. Alternative solution might be usage of direct writing laser mode. Some examples of the so called contour ablation approach for fabricating microlenses with an absolutely monotonically changing cross-sectional profile are presented in the literature. Based on this idea and introducing new variables like automatic mask selection as well as optimizing process algorithms led us to obtain more versatile method for shape approximation. Hence, there were fabricated structures with cross-sectional profiles described as functions that are monotonic on specified intervals such as Fresnel microlenses. In this paper we describe approximation of process parameters for obtaining desired cross-sectional profiles and finally fabrication of few exemplary microlenses. All structures were characterized by a digital optical microscopy and compared to the given profiles. The accuracy of reproduction of the desired structures at the level of single microns was achieved.

Pyridazinium ylids are zwitterionic compounds with a visible band resulting from an intramolecular charge transfer from the carbanion towards the heterocycle. The degree of order of ylid molecules in polymer matrices can be estimated by the dichroism of thin films. The visible band intensity measured on two perpendicular directions (one parallel and other perpendicular on the film stretching direction) determines the dichroic ratio, a parameter proportional to the relative number of the oriented ylid molecules along the stretching direction. From the spectral study it results that about 53% of ylid molecules are oriented when the degree of stretching is about 4. This kind of studies contributes to establish the mechanism of the orientation of the lateral polymer chains and also can offer information about the direction of the intramolecular electronic transfer responsible for the visible absorption band appearance.

Nowadays a growing number of scientists relies on optical spectral measurements for their research. The market is full of new plug-and-play equipment for spectral analysis that take the fuss out of the measurements. As with other instruments (computers, lasers, etc.) the researcher doesn´t need any longer to work with someone with a post-graduate formation on the technology to be able to do excellent research. But, as in every instrument, there are limitations on the instrument use that affect its precision and resolution. Currently there is in the market a large variety of equipment for spectral measurements. They range from the huge long focal length double pass monochromators to the small pocket size USB connected array spectrometers. The different configurations have different sensitivities on the light input system, light intensity, coherence, polarization, etc. In this talk we will discuss a few of the limitations in spectral measurements that can be found in experimental setups.

This work presents a numerical method for determination of spectral transmittance minimum wavelengths of spectrophotometric holmium oxide filter in large band slits. The method used the filter spectral transmittance at 0.05 nm band slit to create a calculated numerical spectral transmittance for 8 and 12 nm band slits. The numerical transmittance minimum wavelength positions for the filter obtained using this method were compared to the results obtained at Mexico National Metrology Institute in the same band slits. The normalized error was the comparison criteria for the results which showed that obtained values were satisfactory according its stated uncertainties.

We show how to generate, encode, transmit and detect single photons. By using single photons we can address two of the more challenging problems that communication engineers face nowadays: capacity and security. Indeed, by decreasing the number of photons used to encode each bit, we can efficiently explore the full capacity to carry information of optical fibers, and we can guarantee privacy at the physical layer. We present results for single and entangled photon generation. We encode information in the photons polarization and after transmission we retrieve that information. We discuss the impact of fiber birefringence on the photons polarization.

In classical cryptography, the bit commitment scheme is one of the most important primitives. We review the state of the art of bit commitment protocols, emphasizing its main achievements and applications. Next, we present a practical quantum bit commitment scheme, whose security relies on current technological limitations, such as the lack of long-term stable quantum memories. We demonstrate the feasibility of our practical quantum bit commitment protocol and that it can be securely implemented with nowadays technology.

In this work we present a theoretical model that takes into account the impact of loss in the generation of photon-pairs through the four-wave mixing process in a highly nonlinear waveguide. Moreover, we also include in the theoretical model the Raman scattering that occurs inside that waveguide. Results indicate that, the bandwidth over which we can efficiently generate correlated photon-pairs is limited by both the phase-matching condition and the Raman scattering process. Results indicate that, in a non-negligible loss regime the presence of the loss coefficient tends to improve the degree of correlation between the photon-pairs generated inside the waveguide.

The well-known phase-shifting approach for three-dimensional surface measurement uses multiple fringe patterns along with the phase-shifting algorithm to obtain 3-D profiles with high accuracy though this approach is not applicable for dynamic object measurement techniques such as time-averaged holography and in cases when only a single interference fringe pattern is available. In this case the fringe tracing method can be used that is based on localization of centers of interference fringes. We propose a technique for the reconstruction of the contour map from fringe patterns which comprises standard image processing techniques and a scheme for reconstruction of the map of continuous curves from the binary matrix of pixels representing fringe centers. The approach of image division into grid cells is taken and such problems as derivation of approximate line equations in each cell using Hough transformation, grouping contacting cells into curves and interpolation between curves with fractures are solved. The functionality of this approach is demonstrated for a demanding optical image containing fractures and noise.

A system using laser speckle effect is proposed to segment images reflecting vibration movements of di use targets. Longitudinal movements are difficult to identify when simple imaging systems are used. The proposed system produces a two dimensional segmentation of the target and it is sensitive to longitudinal movements. The speckle effect, produced when coherent light is reflected and interferes when hitting rough surfaces, can be used in order to accomplish this purpose. A pattern with high and low intensity spots is observed depending on the illuminated scene. In our optical system, two silicone membranes are illuminated using a beam expanded laser source and their patterns are recorded using a video camera. One of the membranes experiences a longitudinal controlled movement while the remaining scene is still. Speckle data is processed using a temporal gradient and a regional entropy computation. This method produces a binary individual pixel classification. Four sets of parameters have been tested for the entropy computation and the area under the receiver operating characteristic (ROC) curve was used to select the best one. The selected set-up achieved a ROC value of 0.9879. A data set with 12 different membrane velocities was used to define the threshold that maximizes the classifier accuracy. This threshold was applied to a validation data-set composed by 4 sinusoidal movements with distinct velocities. The accuracy of this technique has achieved values between 92% and 97%. The results show that the target was accurately identified with the optical non-contact apparatus and the developed algorithm.

In this work the performance of annealed proton-exchanged (APE) waveguides in periodically poled stoichiometric lithium tantalate (PPSLT) for high power applications in the C-band is investigated. Two APE-PPSLT chips comprising 50 waveguides produced with different poling periods and mask width for proton-exchange (PE) were characterized. The performance of the PPSLT devices was also compared with a periodically poled lithium niobate (PPLN) waveguide. Despite lower efficiency, no photorefractive issues or deleterious green light emission were observed in the PPSLT waveguides. The experimental results suggest that the homogeneity of the PPSLT waveguides can be further improved, which will enhance their efficiency.

Over the years, the increased search and exchange of information lead to an increase of traffic intensity in todays optical communication networks. Coherent communications, using the amplitude and phase of the signal, reappears as one of the transmission techniques to increase the spectral efficiency and throughput of optical channels. In this context, this paper present a survey on format conversion of modulated signals using MZISOAs, based exclusively on all-optical techniques through wavelength conversion. We also present two proposal using all-optical techniques: One for the conversion of amplitude modulation signals to a continuous phase modulation format, and another technique for the conversion of OOK signals to QPSK and QAM signals. Both approaches are experimentally validated.

In this paper we propose and demonstrate by simulation an all-optical modulation format conversion from non-return-tozero on-off keying (NRZ-OOK) at 10 Gb/s to dual-polarization quadrature-phase-shift keying(DP-QPSK) at 20 Gb/s for each channel, by cross phase modulation (XPM) in a polarization-maintaining highly nonlinear fiber (PM-HNLF). The obtained results show a constellation diagram with an error vector magnitude (EVM), 17.26% and 18.79%, for each channel. The input powers of the two NRZ-OOK channels were 16.9dBm and 13.9dBm for a 3km fiber length. We also studied the impact of the nonlinear fiber length in the conversion of the signal and analyzed the system performance based on error vector magnitude (EVM) for different fiber lengths.

In this paper we address soliton-soliton interactions in a nonlinear cubic-quintic optic media, using for that purpose numerical methods and high performance graphics processor unit (GPU) computing. We describe an implementation of GPU-based computational simulations of the generalized Nonlinear Schrodinger Equation, obtaining simulations more than 40 times faster relative to CPU-based simulations, especially in the multidimensional case. We focus our attention in the study of soliton collisions and scattering phenomena that, offering the possibility of steering light with light, open a path towards future optical devices.

Hydrogen and heat energy from the reaction of magnesium with water can be used for engines and fuel cells. However, at least 4000 K is necessary for magnesium oxide reduction. Ultra high brightness solar-pumped lasers become essential to make this renewable process technology efficient and economically competitive. 2.3 mg/kJ solar laser - induced magnesium production efficiency has been achieved by T. Yabe et al., in 2012, by focusing a 53 W solar laser beam on a mixture of MgO with Si as reducing agent. This result is however far from the 12.1 mg/kJ attained with 2 kW/mm2 CO2 laser beam. To improve substantially the solar laser - induced Mg production efficiency, a simple high-power, high brightness Nd:YAG solar laser pumping approach is proposed. The solar radiation is both collected and concentrated by four Fresnel lenses, and redirected towards a Nd:YAG laser head by four plane folding mirrors. A fused-silica secondary concentrator is used to compress the highly concentrated solar radiation to a laser rod. Optimum pumping conditions and laser resonator parameters are found through ZEMAX© and LASCAD© numerical analysis. High-record solar laser beam brightness figure of merit - defined as the ratio between laser power and the product of M_x ² and M_y ² - of 10.5 W is numerically achieved, being 5.5 times higher than the previous record and about 1600 times more than that of the most powerful Nd:YAG solar laser. 8340 W/mm² is numerically achieved at its focal region, which can quadruple the magnesium production efficiency with clean energy.

One of the most used techniques for measuring the optical aberrations of the human eye is the so-called Shack-Hartmann aberrometer. In this paper, a compact experimental setup is presented for the acquisition of in vivo human eye aberrations. This experimental aberrometer system will be used as the adaptive optics (AO) arm of a flood illuminating system. The experimental results of the eye aberrations acquisition using our proposed system are presented and compared with the irx3 commercial aberrometer, probing the validity of our system. Also, we present the preliminary results of the capture of the fundus of a model eye.

With the aim of taking into account all optical aberrations, a personalized pseudophakic optical model was designed for refractive evaluation using ray tracing software. Starting with a generic model, all clinically measurable data were replaced by personalized measurements. Data from corneal anterior and posterior surfaces were imported from a grid of elevation data obtained by topography, and a formula for the calculation of the intraocular lens (IOL) position was developed based on the lens equator. For the assessment of refractive error, a merit function minimized by the approximation of the Modulation Transfer Function values to diffraction limit values on the frequencies corresponding up to the discrimination limits of the human eye, weighted depending on the human contrast sensitivity function, was built. The model was tested on the refractive evaluation of 50 pseudophakic eyes. The developed model shows good correlation with subjective evaluation of a pseudophakic population, having the added advantage of being independent of corrective factors, allowing it to be immediately adaptable to new technological developments. In conclusion, this personalized model, which uses individual biometric values, allows for a precise refractive assessment and is a valuable tool for an accurate IOL power calculation, including in conditions to which population averages and the commonly used regression correction factors do not apply, thus achieving the goal of being both personalized and universally applicable.

Of all the non-linear fiber propagation models proposed over the years, the Gaussian Noise (GN) model is growing in popularity due to its simplicity and yet reliability when it comes to predict performance of uncompensated coherent transmission (UT) systems that rely on state-of-the art digital-signal processing (DSP) for dispersion compensation. However, many of the systems currently deployed rely on optical CD compensation. Overhauling or upgrading these systems with the most recent DSP is not always feasible. In this context, it is important to broad the range of the GNmodel to dispersion managed (DM) systems, so both scenarios can benefit from a low complexity, fast and reliable performance prediction tool. In this paper, we validate the first results comparing the performance in both accuracy and simulation time of the GN model simulating a realistic DM scenario that relies on periodical spans of non-dispersion shifted fiber (NDSF) to perform the dispersion compensation. The same realistic scenarios were modeled with commercial software and the GN model. The objective was to predict the optimal launch power for different link lengths, central wavelengths and channel spacing values. Preliminary results obtained with the GN model are in good agreement with the ones from the commercial software for several link distances tested up to 2400 Km.

We experimentally demonstrate a set of ultra-high capacity free space passive optical networks (PONs) using quadrature phase shift keying (QPSK), 16-quadrature amplitude modulation (16-QAM) Nyquist pulse shaped and orthogonal frequency-division multiplexing (OFDM) modulations. Moreover, these technologies support up to 10 Gb/s services per user and allow a smooth and full integration between fiber and optical wireless access networks.

In this paper we’ll try to improve conversion gain of an integrated opto-electronic mixer, based on InP/InGaAs hetero junction bipolar transistors in both single and cascode configurations. For this purpose we’ll use a hybrid-Pi model, extracted from physical parameters of HBT transistors. For verification of our results and calibration of software simulator, at first, we compared our simulation results with empirically reported experiments for a prefabricated HBTOEM sample. Then we examine the simulator on our modified proposed HBT to prove its better gain performance. As a result of our improvements, down conversion power gain for the new proposed mixer in comparison with previously reported results is improved about 11dB, 16dB and 19dB respectively in optical modulation frequencies about 200MHz, 1GHz and 10GHz for single mixer. These values for cascode mixer are about 6dB, 10.5dB and 16dB respectively in optical modulation frequencies about 200MHz, 1GHz and 10GHz. These improvements are mainly because, current gain of HBT device has been improved from 130 to 318.

Recently, many studies show that an indoor horse riding exercise has a positive effect on promoting health and diet. However, if a rider has an incorrect posture, it will be the cause of back pain. In spite of this problem, there is only few research on analyzing rider’s posture. Therefore, the purpose of this study is to estimate a rider pose from a depth image using the Asus’s Xtion sensor in real time. In the experiments, we show the performance of our pose estimation algorithm in order to comparing the results between our joint estimation algorithm and ground truth data.

This paper proposes a new methodology for the generation of quadrature amplitude modulation signals, based on all-optical processing from nonlinear interferometric devices. The degradation of the systems performance is numerically analyzed, as a function of operational parameter’s unbalance and physical impairments of the system. The results shows that the probe laser power and the coupling factor of optical couplers are the most sensitive parameters of the proposed format conversion system.

USC-OSA is a student chapter whose objective is to bring Optics knowledge closer to the non-optics community. The activity developed at the Hospital school was one of the most important last year. It was consisted in a few Optics experiments and workshops with hospitalized children of different ages and pathologies. The experiments had to be adapted to their physical conditions with the aim of everyone could participate. We think this activity has several benefits including spreading Optics through children meanwhile they have fun and forget their illness for a while.

We have adapted low cost webcams to the slit lamps objectives with the aim of improving contact lens fitting practice. With this solution we obtain good quality pictures and videos, we also recorded videos of eye examination, evaluation routines of contact lens fitting, and the final practice exam of our students. In addition, the video system increases the interactions between students because they could see what their colleagues are doing and take conscious of their mistakes, helping and correcting each others. We think that the proposed system is a low cost solution for supporting the training in contact lens fitting practice.

The drugs of abuse, which affect human nature and cause numerous crimes, have become a serious problem throughout the world. There are hundreds of amphetamine analogues on the black market. They consist of various alterations of the basic amphetamine molecular structure, which are yet not yet included in the lists of forbidden compounds although they retain or slightly modify the hallucinogenic effects of their parent compound. It is their important variety that makes their identification quite a challenge. A number of analytical procedures for the identification of amphetamines and their analogues have recently been reported. We are presenting the profile of the main hallucinogenic amphetamines obtained with the hyphenated techniques that are recommended for the identification of illicit amphetamines, i. e. gas chromatography combined with mass spectrometry (GC-MS) and gas chromatography coupled with Fourier transform infrared spectrometry (GC-FTIR). The infrared spectra of the analyzed hallucinogenic amphetamines present some absorption bands (1490 cm^-1, 1440 cm^-1, 1245 cm^-1, 1050 cm^-1 and 940 cm^-1) that are very stable as position and shape, while their intensity depends of the side-chain substitution. The specific ionic fragment of the studied hallucinogenic compounds is the 3,4-methylenedioxybenzyl cation (m/e = 135) which has a small relative abundance (lesser than 20%). The complementarity of the above mentioned techniques for the identification of hallucinogenic compounds is discussed.

Cancer cells can be easily killed when they reach a temperature above 40 degrees. This is known as hyperthermia and the incorporation of nanoparticles (NPs) is helpful to locally rise the temperature. The local heating of NPs could also be used to deliver drugs encapsulated in a specific location inside a body. To achieve the local heating it is necessary to know the temperature profile of the NPs when excited by laser radiation. The COMSOL software was used to simulate the temperature pro le of the NPs in an aqueous solution (the cells are mainly composed of water). An analysis is made regarding the temperature rise for different irradiation parameters, NPs concentration and the corresponding potential of locally affecting cancerous cells without significantly affecting adjacent healthy cells.

Laser surface texturing is a promising tool for improving metallic biomaterials performance in dental and orthopedic bone-replacing applications. Laser ablation modifies the topography of bulk material and might alter surface properties that govern the interactions with the surrounding tissue. This paper presents a preliminary evaluation of surface modifications in two biometals, stainless steel 316L and titanium alloy Ti6Al4V by UV nanosecond Nd:YVO4. Scanning electron microscopy of the surface textured by parallel micro-grooves reveals a thin layer of remelted material along the grooves topography. Furthermore, X-ray diffraction allowed us to appreciate a grain refinement of original crystal structure and consequently induced residual strain. Changes in the surface chemistry were determined by means of X-ray photoelectron spectroscopy; in this sense, generalized surface oxidation was observed and characterization of the oxides and other compounds such hydroxyl groups was reported. In case of titanium alloy, oxide layer mainly composed by TiO2 which is a highly biocompatible compound was identified. Furthermore, laser treatment produces an increase in oxide thickness that could improve the corrosion behavior of the metal. Otherwise, laser treatment led to the formation of secondary phases which might be detrimental to physical and biocompatibility properties of the material.

We present a model in which polymeric spherical microstructures embedded with a light absorbing dye are shown to attain the phase transition temperature necessary for the release of a drug contained in its polymeric matrix into the surrounding medium. By numerically solving the heat diffusion equation and considering a Gaussian near-infrared source it is shown that heating is mostly confined to the particle although limited heat transfer occurs out into the surrounding medium. The influence of different operational parameters is analyzed. Based on the results, we elaborate on the experimental implementation of this kind of remotely operated drug delivery systems.

Light and its properties is a subject that strongly attracts children from very early ages. Inquiry-based science teaching although addressed in the curricula of various countries and suggested by some international organizations, continues to have a very low expression in the teaching practices of the majority of primary school teachers and preschool educators. In this sense, we have organized several continuing training courses in order to encourage these education professionals to promote this approach to science teaching in the classroom, with the children. As part of this training process, teachers and educators put into practice, with their students, the didactic knowledge they have developed, in order to become aware of the virtues of an inquiry-based approach to children's learning. Through the implementation of the "Reflection of Light" activity, in this article, we intend to analyze the process of teaching and learning promoted in a 3rd grade class by one of the teachers participating in the training courses. The analysis of the process reveals that the teacher in training carried out a successful didactic integration of the inquiry-based science teaching approach recommended for children. In turn, the children also developed a good understanding of the contents of the activity explored in the classroom.

This paper results from a pedagogical intervention project carried out at a primary school. The intervention took place in a class of the 3rd year, composed by 16 students, and it incorporated a practice of Inquiry-Based Science Education (IBSE), addressing the curricular topic “Light and Shadows”. Various inquiry activities on some of the factors that might influence the length of shadows were implemented in the classroom, during a total of 10 hours, spread over 4 lessons. At the end of each lesson, a class diary was prepared – a descriptive and reflective narrative based on field notes and audio recordings made during participant observation in the context of the classroom. The aim of this paper is, through the analysis of one of those class diaries, to describe and interpret the teaching and learning process that took place in the classroom. The results of an assessment test show that the children acquired a good understanding on some of the factors that influence the length of shadows. We will also discuss some of the processes that stimulated the construction of this learning.

The question regarding visual imagery and visual perception remain an open issue. Many studies have tried to understand if the two processes share the same mechanisms or if they are independent, using different neural substrates. Most research has been directed towards the need of activation of primary visual areas during imagery. Here we review some of the works providing evidence for both claims. It seems that studying visual imagery in blind subjects can be used as a way of answering some of those questions, namely if it is possible to have visual imagery without visual perception. We present results from the work of our group using visual activation in dreams and its relation with EEG’s spectral components, showing that congenitally blind have visual contents in their dreams and are able to draw them; furthermore their Visual Activation Index is negatively correlated with EEG alpha power. This study supports the hypothesis that it is possible to have visual imagery without visual experience.

Madeira wine is a fortified wine produced in Madeira Island, Portugal. Its characteristics are strongly influenced by the winemaking method used which includes a typical and unique step called estufagem. This process consists on heating the wine up to 55 ºC for at least 3 months. In this paper, the characterization of the sensor for the pilot scale facility of estufagem installed in Madeira University is presented, being the device an optimization of a previous version. The response of the sensor was tested towards colour and refractive index, showing a good performance. Madeira wine with different estufagem times was also analysed.

Triazolium ylids are dipolar molecules with separated charges in their ground electronic state; the positive charge is located on one Nitrogen atom belonging to the heterocycle and the negative charge is located near the ylid carbanion. The intramolecular charge transfer from the carbanion to heterocycle gives a visible electronic absorption band, very sensitive to the solvent nature. Its position in the wavenumber scale offers information about the intermolecular interactions in which the ylid molecules are engaged. The spectral study revealed the presence of both universal and specific interactions in solutions of 1,2,4-triazolium ylids with protic solvents. By choosing adequate binary solvents, the contribution of the specific interaction of the weak hydrogen bond between the –OH atomic group of the protic solvents and the ylid carbanion can be estimated. Ternary solutions of the studied ylids achieved with Methanol +Benzene, Water + Ethanol and 1,3 Propanediol + Dimethyl formamide binary solvents are analyzed from spectral point of view and the difference between the potential energies in molecular pairs of the types: 1,2,4-triazolium ylid-protic solvent and 1,2,4-triazolium ylid-non protic were estimated on the basis of the statistic cell model of ternary solutions.

In the last decades the fiber Bragg gratings (FBG) and Fabry-Perot Interferometer (FPI) micro cavities based sensors have become one of the most attractive optical fiber sensing technologies. However, its production requires a significant economical investment. We propose a cost effective solution based on micro cavity generated by the recycling of optical fibers destroyed through the catastrophic fuse effect. This technique considerably reduces the experimental complexity and the production costs. In this paper, the application of these sensors in the monitoring of several parameters, such as refractive index, pressure, strain and temperature is presented.

The historical development of lighting technologies has been characterized by what evolution theorists call 'punctuated equilibrium': a succession of long periods of stable development followed by short periods of rapid change when key technological breakthroughs give rise to new lighting paradigms. Nowadays with the massive deployment of LED-based solid state lighting systems the illumination field is undergoing one of such accelerated transformation events. In parallel, a growing body of research has unveiled some of the complex interactions between the daily cycles of light and darkness and the regulating mechanisms of individuals, populations and ecosystems, including humans. This communication addresses some of the challenges that this new situation poses for the development of sustainable lighting systems.

This work addresses the study of repeatability of an optical laser system, previously implemented by our research team, for characterization of the fiber distribution and mass density of two paper samples with different characteristics. In the experiment that has been carried out in the current work, both paper samples were laser scanned by the system on a total of 16 times (4 times per day in 4 different days). The data acquired and registered during the experimental work, associated to both tested samples, were then processed and the obtained results showed that the optical system is precise.

The channeled spectra of optically active crystalline layers, (quartz of Maramures was used in our experiments) placed between two identical crossed polarizers, were recorded and the difference Δn_c = n_l − n_r between the crystal refractive indices for circularly polarized radiations to left and to right, respectively, was computed by using the conditions of the minima and maxima of flux density in channeled spectrum. The theory of the phenomena determining the channeled spectra is discussed here. The optical rotatory dispersion of quartz is estimated in the visible range and the obtained results are concordant with those from literature. The quartz optical rotatory dispersion decreases when the wavelength of radiation increases (from blue to red). This kind of measurements is important for industry of optical devices working in polarized light. The method described in this paper is distinguished by rapidity and a large spectral range in which can be applied.

When linearly polarized light impinging on a lens, it will reflect and refract along the lines curves resulting from the interception of a plane (plane of polarization) with a sphere (lens surface) maintaining the orientation of refraction and reflection within the plane of polarization. This effect is significant only looking at the lens laterally. Therefore, a lens acts as a lateral analyzer when the polarization plane of polarized light incident on the lens is rotated. Following this principle that in the spherical surface of a lens fit n circles of radius r, where n is inversely proportional to r, and each circle is a lens itself. Then if a beam of light is shined in one of these areas, the phenomenon is expressed lateral side and diametrically opposite to where the incident linearly polarized light, the lens acting as a waveguide for the light beam polarized.

TeO2 based glasses with the molar composition (70-x-y)TeO₂-20WO₃-10Y₂O₃-xEr₂O₃-yYb₂O₃, where x = 0 and 0.5 mol% and y = 0, 0.5, 1, 2 and 4 mol%, were prepared by the melt quenching technique. The Raman spectra of the vitreous samples, using laser excitation line of 532 nm showed a band distribution related with Te-O and W-O bond vibrations. The introduction of WO₃ results in a higher bandwidth relatively to SiO₂ based glasses and even other TeO₂ based glasses, making this vitreous system promising for Raman optical amplification. The use of UV laser excitation line of 325 nm induced surface modifications on the samples.

We present a flexible fluorescence lifetime imaging device which can be employed to scan large sample areas with a spatial resolution adjustable from many micrometers down to sub-micrometers and a temporal resolution of 20 picoseconds. Several different applications of the system will be presented including protein microarrays analysis, the scanning of historical samples, evaluation of solar cell surfaces and nanocrystalline organic crystals embedded in electrospun polymeric nanofibers. Energy transfer processes within semiconductor quantum dot superstructures as well as between dye probes and graphene layers were also investigated.

Relying on the next generation chip-scale technology, Plasmonics, here is presented a novel plan for Dielectric-Loaded Surface Plasmon Polariton-based Ring Resonator (DLSPP-RR) switching configuration. The device is a 1x2 switch with a left-rob Y splitter in the middle of coupling region to share the electromagnetic energy between the two straight and bend output waveguides. Like other active devices, specially switching structures, this plan also will have the potential to be prepared as an active device if its trapped-modes into ring resonator can be controlled on the frequency axis. We implemented simulation of the device by means of the rigorous 3D Finite Element Method (3D-FEM) to certificate its truly passive performance. The obtained results are mixed as transmission spectrums of two output ports on a relatively close frequency band around the telecommunication wavelength of λ = 1550 nm.

We present an overview of the pulse compression phenomenon obtained during the propagation of ultra-short pulses in common used optical waveguides. In the case of the silicon-on-insulator (SOI) waveguides, using the modified and realistic variational approach (MVA) that involves the Rayleigh’s dissipation function (RDF), we conduct the analysis of the compression mechanism on different input profiles. This study allows to show the effects of fourth-order dispersion (FOD), the nonlinear coefficients of absorption (nonlinear absorption) and the chirp, not only on symmetric and compact pulses but also on those with asymmetric profile as the Airy pulses. Indeed, considering the case of linear compression, the conditions of their occurrence are obtained. A relation between the FOD, the group-velocity dispersion (GVD) and the chirp is proposed in this way. In the nonlinear case, using the symmetric profiles as input pulses, we demonstrate a periodic compression induced by the interplay between the self-phase modulation (SPM) and the FOD. This appears as a new mode to generate the pulse compression phenomenon. Then, we show that when large values of the initial chirp and absorption coefficients as the two-photon absorption (TPA) present in these waveguides are considered, the compression mechanism is completely destroyed with at least the observation of one pulse amplification over a short distance of propagation before the pulse broadening. Finally, the study relating to the Airy pulses, leads rather to the reduction of the compression length induced by the SPM, the TPA and the free-carrier absorption (FCA) showing the pulse asymmetry influence.

Recently we developed a new method of spherical submicron particle production by pulsed laser irradiation of primary small irregular nanoparticles suspended in liquid. For the first time we demonstrated that the nanoparticles can not only reduce their sizes under the pulse laser irradiation, but can grow essentially. To control the particle formation process, the mechanism of particle interaction with laser pulse has to be understood. Particle heating-melting-evaporation model was successfully applied to clarify this mechanism.

Laser-induced breakdown spectroscopy (LIBS) is a fast, fully optical method, that needs little or no sample preparation. In this technique qualitative and quantitative analysis is based on comparison. The determination of composition is generally based on the construction of a calibration curve namely the LIBS signal versus the concentration of the analyte. Typically, to calibrate the system, certified reference materials with known elemental composition are used. Nevertheless, such samples due to differences in the overall composition with respect to the used complex inorganic materials can influence significantly on the accuracy. There are also some intermediate factors which can cause imprecision in measurements, such as optical absorption, surface structure, thermal conductivity etc. This paper presents the calibration procedure performed with especially prepared pellets from the tested materials, which composition was previously defined. We also proposed methods of post-processing which allowed for mitigation of the matrix effects and for a reliable and accurate analysis. This technique was implemented for determination of trace elements in industrial copper concentrates standardized by conventional atomic absorption spectroscopy with a flame atomizer. A series of copper flotation concentrate samples was analyzed for contents of three elements, that is silver, cobalt and vanadium. It has been shown that the described technique can be used to qualitative and quantitative analyses of complex inorganic materials, such as copper flotation concentrates.

The tunable mode conversion between symmetric and antisymmetric optical modes induced by acoustic flexural waves in optical microwires is proposed. The acoustic frequency dictates the resonant coupling between the optical modes, and consequently, the modes in which the mode conversion occurs. On the other hand, the efficiency of the mode conversion can be controlled by the acoustic wave amplitude. Moreover, symmetric modes can also be excited by a double resonant coupling between a symmetric and an antisymetric mode, and further between the antisymmetric mode excited and another symmetric mode, leading to a mode conversion between symmetric modes.

The developed directional coupler using polymer optical fiber performance is studied analytically where related theories are integrated and the outcomes are analyzed. Important theories such as simplified coupled mode theory and elliptical point contacts are integrated where the parameters such as coupling length, distance between the two fibers cores and forces are varied. Using simplified coupled mode theory, coupling coefficient and coupling efficiency is obtained based on the parameters of multimode fiber coupler such as the operating wavelength, numerical apertures, coupling length and diameter of the cores. The two fibers are initially tapered at certain length at most 20 mm and attached to geometrical blocks with certain radii and the middle tapered regions of the fibers are brought closed in proximity and they are lapped to each other. Investigation of different radii of the geometrical blocks represents the effect of macro-bending when the fibers are bent when attached to the circular blocks. This concept is used to transfer the modes from first fiber to the second. Then a particular amount of load force is exerted upon one side of the blocks so that the gap is closed and leads to increment of coupling length between the two fibers. The various load force amount will give different coupling lengths and distances between the two cores, thus leading to different coupling efficiencies. Analytically the expression that represents the coupling efficiency with force is an integrated expression from simplified coupled mode theory and Hertz’s Law of elliptical point contacts. Optimized coupling efficiency obtained is as high as 70% for this study.

In this study we present a scheme for modelocked laser stabilization that narrows the RF linewidth and lowers the timing jitter. The aim of this scheme is to stabilize the pulse repetition frequency (PRF) to be used in an absolute long distance measurement technique. In the most of the stabilization schemes, PRF is kept constant, however in this scheme; the PRF is required to perform a sweep, while achieving a relative error in the order of 10^-8 or better within the tuning range. The laser used is a symmetrical cladding single section InAs/InP quantum dash emitting at 1550 nm and with a pulse repetition frequency of 4.37 GHz The techniques proposed for stabilization are hybrid mode-locking and optical feed-back. In hybrid modelocking, the PRF is locked to the local oscillator (LO), lowering the RF linewidth and the jitter. By performing a frequency modulation of LO, the PRF is modulated. The optical feedback technique uses a fraction of the output radiation that is fed back into the laser cavity after a certain delay. If the delay line is correctly adjusted, this will reduce the timing jitter of laser. The progress in this technique is in the synchronization of the LO with the delay line, combining the benefits of both techniques. Performing a sweep in PRF, the synchronization circuit adjusts the delay line to match incoming pulses within the cavity. Preliminary results are showed.

The aim of this study was to evaluate the behavior of two types of resin cements , conventional dual and dual self adhesive, through in vitro and in situ experiments. For the in vitro assay were selected two resin cements that were handled and dispensed over a mylar strip supported by a glass plate. The Bragg grating sensors were positioned and another portion of cement. was placed, covered by another mylar strip. For the in situ experiment 16 single-rooted teeth were selected who were divided into 2 groups: group 1 - conventional dual resin cement Relyx ARC and group 2 - dual self adhesive resin cement Relyx U200 ( 3M/ESPE ). The teeth were treated and prepared to receive the intracanal posts. Two Bragg grating sensors were recorded and introduced into the root canal at different apical and coronal positions. The results showed that the in vitro experiment presented similar values of polymerization shrinkage that the in situ experiment made in cervical position; whereas Relyx ARC resulted lower values compared to Relyx U200; and cervical position showed higher shrinkage than the apical.

The development of SPP-based terahertz waveguides has demonstrated being of great potential to achieve an appropriate trade-off between losses and dispersion, particularly for sensing and imaging operations at that spectral band. In this work, we implement a microstructured fiber comprising an air core surrounded by an array of silver rods and air holes. With our geometry, we can reach losses of 0.01 cm^-1 and dispersion nearly zero for a broad range of the terahertz region. Our goal is to demonstrate that we can optimize those waveguide structures to improve their properties at terahertz band.

This paper presents the synthesis of gold nanoparticles (AuNPs) suitable to the construction of engineering biosensors. The phenomenon of Localized Surface Plasmons Resonance (LSPR) and Surface Plasmon Polarization are explored in these sensors. AuNPs allow developing nanoscale devices that interacts with chemical and biological systems. The LSPR is the main operation principle explored in these nanosystems that promote electromagnetic wave oscillation on such small metallic structures. Our results have shown that the resonance is directly linked to the size of the nanoparticles, the nature of the dielectric material and support environment where the device is being studied, previously reported for Zhao et al. [1]. Nanoparticles with size of 56 to 88 nm was obtained this work. The Turkevich method was to used to make AuNP’s with spherical morphology, this system is it possible to application in biosensor because your strong interation with light and environment.

An experimental setup has been developed for different gas species sensing based on the Wavelength Modulation Spectroscopy (WMS) principle. The target is the measurement of ammonia, carbon dioxide and methane concentrations. The WMS is a rather sensitive technique for detecting atomic/molecular species presenting the advantage that it can be used in the near-infrared region using optical telecommunications technology. In this technique, the laser wavelength and intensity are modulated applying a sine wave signal through the injection current, which allows the shift of the detection bandwidth to higher frequencies where laser intensity noise is reduced. The wavelength modulated laser light is tuned to the absorption line of the target gas and the absorption information can be retrieved by means of synchronous detection using a lock-in amplifier, where the amplitude of the second harmonic of the laser modulation frequency is proportional to the gas concentration. The amplitude of the second harmonic is normalised by the average laser intensity and detector gain through a LabVIEW® application, where the main advantage of normalising is that the effects of laser output power fluctuations and any variations in laser transmission, or optical-electrical detector gain are eliminated. Two types of sensing heads based on free space light propagation with different optical path length were used, permitting redundancy operation and technology validation.

The physical mechanisms involved in the writing process of long period fiber gratings (LPFG) using mid-infrared radiation emitted by CO2 lasers limit the obtained characteristics, in particular the minimum period that can be achieved. In order to evaluate the performances of a new methodology developed by us, we analyzed its capability to produce gratings with different periods (from 600 μm down to 300 μm). We also present a repeatability study on the obtained LPFG characteristics (mainly the resonant wavelength and grating length) for several values of the repetition period.

Electric current sensor based on magnetostriction phenomenon has been reported in several papers. In common these previous papers used a fiber Bragg grating (FBG) to determine the strain of the magnetostrictive material. However, magnetostriction sensors present few disadvantages often neglected, such as the temperature dependence of magnetostriction. In this paper a Terfenol-D rod (a giant magnetostrictive material-GMM) is used for tests. For simultaneous measurement of temperature and strain two multiplexed FBGs are used. The first test presents unipolar characteristics of Terfenol-D magnetostriction. Other test determines the Terfenol-D response for different temperatures. The Terfenol-D sensitivity increase when the temperature increases, however the saturation of the material occurs in small field values. The characteristics presented in this paper must be taken into account in the development of magnetostrictive sensors and its limitations.

A new configuration for volatile organic compound sensing is proposed. A sub-milimiter four-hole suspended core optical fiber tip, spliced to a standard single mode fiber, is dipped in a liquid volatile compound and the reflected signal is continuously interrogated. When the fiber is immersed in acetone it suffers a 14 dB signal drop. Different menisci form in each cladding cavity, with different evaporation times and rates. The signal restores its initial state not when the evaporation process is complete but after the collapse of a dominant meniscus.

Although light has long being used in medicine, scattering always hindered its use. This study intends to evolve into three different frontlines: development of methodologies to concentrate light inside biological tissues, development of an optical tissue phantom and development of multifunctional gold nanoparticles with therapeutic potential for targeting anticancer drug delivery. The impact of the scattering agent (milk) concentration in the measured wavefront and spot radius is analyzed. Wavefront correction proves to be efficient in overcoming the scattering effect in the different phantoms. Future studies for developing a photodynamic approach under near-infrared wavelength are now in progress and will be further presented.

Currently, the surface plasmon resonance (SPR) based sensors are mainly focused in visible frequencies, being a barrier for a better integration with the typical fiber optical communication transmission bands. Here, it is presented a theoretical analysis of a SPR based fiber optic sensor with a uniform gold coating on a U-shaped probe. The sensor does not require any fiber etching treatment which eases and improves the control of the overall process. The response of the device to refractive index variations was investigated and a resolution of 10^-8 is foreseen for refractive indices around 1.413, becoming the proposed sensor a useful tool for biological and chemical applications.

Studies to determine the concentration of hydrogen peroxide (H2O2) are important in biological system due to cellular damages provoked by reative oxygen species that include H2O2. An alternative to detect H2O2 is through an optical nanosensors based on silver nanoparticles, which have great potential for chemical and biological sensing applications. Here we demonstrate that attenuated total reflectance (ATR) from interaction of silver nanoparticles and hydrogen peroxide were able to detect very low levels of H₂O₂ around 0,001mM.

Injection molding is an important polymer processing method for manufacturing plastic components. In this work, the thermal monitoring of the thermoplastic injection molding is presented, since temperature is a critical parameter that influences the process features. A set of fiber Bragg gratings were multiplexed, aiming a two dimensional monitoring of the mold. The results allowed to identify the different stages of the thermoplastic molding cycle. Additionally, the data provide information about the heat transfer phenomena, an important issue for the thermoplastic injection sector, and thus for an endless number of applications that employ this type of materials.

In this work, the regeneration of saturated fiber Bragg gratings during the diamond coating of the fiber is presented. Due to the high temperatures characteristic of the hot filament chemical vapor deposition (HFCVD) process (around 800 ºC), uniform fiber Bragg gratings (FBGs) are not appropriate to be coated. Nevertheless, regenerated Bragg gratings are a suitable solution for this drawback. Its production process involves the inscription of a saturated FBG followed by a time consuming heat treatment. Here it is proposed to take advantage of the high temperatures characteristic of the HFCVD process to simultaneous regenerate the grating and coat the fiber with diamond.

In this work, a remote curvature sensor using a standard OTDR as the interrogation system is presented. This approach uses a core diameter mismatch sensor which is formed by a short section of a multimode fiber, with a length of 3 mm, sandwiched between two singlemode fibers. In this case, the attenuation of the optical signal will vary as the fiber is bent allowing interrogating the sensor with OTDR technology. Preliminary results indicate a resolution range of ~0.0003 cm^{- 1}, sensitivity in the range of ~-208.46 dB/cm^-1 and a variation of 2.67 dB in the OTDR trace within the bend radius range.

The spectral shifts measured in different solvents are expressed as functions of the solvent macroscopic parameters. The value of the correlation coefficient multiplying the functions of electric permittivity was determined by statistical means. The correlation coefficient depends on the electric dipole moment of the spectrally active molecules. The electro-optical parameters in the ground state of the solute molecules can be approximated by molecular modeling. The excited state parameters are usually estimated using the results obtained both by HyperChem Programme and solvatochromic study. The importance of this approximate method is that it offers information about of the excited state of solute molecule for which our measuring possibilities are very restrictive. The information about the excited electronic state is affected by the limits in which the theories of liquid solutions are developed. Our results refer to two molecules of vitamins from B class, namely B3 and B6.

Optical fiber sensors based on the phenomenon of plasmonic resonance can be interrogated applying different methods, the most common one being the spectral approach where the measurand information is derived from the reading of the wavelength resonance dip. In principle, a far better performance can be achieved considering the reading of the phase of the light at a specific wavelength located within the spectral plasmonic resonance. This approach is investigated in this work for surface plasmon based fiber optic sensors with overlays which are combinations of bimetallic layers, permitting not only to tune the wavelength of the plasmon resonance but also the sensitivity associated with the phase interrogation of the sensors. The metals considered for the present analysis are silver, gold, copper, and aluminum.

The design, fabrication and tests of a new generation of superconducting magnets for the upgrade of the LHC require the support of an adequate, robust and reliable sensing technology. The use of Fiber Optic Sensors is becoming particularly challenging for applications in extreme harsh environments such as ultra-low temperatures, high electromagnetic fields and strong mechanical stresses offering perspectives for the development of technological innovations in several applied disciplines.

We present system of structure health measurement by optical fiber sensors based on fiber Bragg gratings. Our system is focused to additionally install to existing buildings. We prepared first set-up of the system to monitoring of the nuclear power plant containment shape deformation. The presented system can measure up to several tens of sensors simultaneously. Each sensor contains optical fiber grating to measurement of change of length and the other independed fiber grating to monitor the temperature and the other ineligible effects.

We present vibration fiber sensor set up based on tilted fiber Bragg grating (TFBG) and fiber taper. The sensor uses the TFBG as a cladding modes reflector and fiber taper as a bend-sensitive recoupling member. The lower cladding modes (ghost), reflected from TFBG, is recoupled back into the fiber core via tapered fiber section. We focused on optimization of TFBG tilt angle to reach maximum reflection of the ghost and taper parameters. Comparative measurements were made using optical spectrum analyzer and superluminiscent diode as broadband light source. We present dependence between intensity of recoupled ghost mode and sensor deflection.

Sinusoidal gratings of equal spatial frequency but different orientation require different levels of contrast to be detected by the human visual system. This phenomenon defined as oblique effect has a neuronal origin. The purpose of this work was to determine the neuronal magnitude of this effect, by isolating it from the optics of the eye. A visual interferometer was assembled to generate and project on the retina an interference pattern consisting of sinusoidal gratings with variable orientation (0º to 165º, 15º step). Adding background light to the interference pattern of 12 cycles/degree (cpd), different contrast levels were generated while the retinal illuminance was kept unaltered. A 2º circular stimulus was presented (during 500 ms) on the fovea producing a retinal illuminance of 134 Td (trolands). The contrast sensitivity threshold of four observers (ages 23, 33, 33, 52 years old) was determined using a Yes-No psychophysical method, and the 50% odds of correct response determined by a Weibull cumulative function. The four observers showed different contrast sensitivity thresholds dependent on the grating orientation. Oblique gratings (≈45º/≈135º) required more contrast to be detected than horizontal and vertical gratings. The maximum differences in contrast sensitivity between orientations ranged from 0.15 to 0.31 log units. The mean contrast threshold across all orientations was then calculated to investigate the effect of age on the contrast sensitivity. It was found a 0.046 log units decrease per decade (r=0.94). Oblique effect is an evident neuronal phenomenon with considerable inter-subject variability, making grating orientation important information in contrast sensitivity evaluation.

In small diameter positron emission tomography (PET) systems, the determination of the depth-of-interaction (DOI) of 511 keV gamma photons in scintillator crystals is of great importance, in order to achieve high DOI resolution with good uniformity within the entire field-of-view. In this work, we propose a new method for DOI determination, in which a single layer of LYSO crystals is read out on both ends through the use of silicon photomultipliers (SiPMs), but using wavelength-shifting fibers and a reduced number of SiPMs on one end. This design results in a simpler and less expensive readout when compared to the typical dual-ended readout method, which requires two photodetectors per crystal and corresponding readout electronics. GATE simulation of the system was carried out and experimental proof-of-concept studies were performed on a single detector cell (composed of two LYSO crystals operating in coincidence), to evaluate the amount of light detected on each side of the crystal and the achievable DOI resolution with this method, taking into account the attenuation of the light signal on the fiber side with crystal-SiPM distance. The feasibility of applying this new method in full detector rings for a small animal PET system is evaluated and discussed, considering different alternatives for position readout electronics.

In the present work, samples of healthy and adenocarcinoma-affected human gastric tissue were analyzed using transmission time-domain THz spectroscopy (THz-TDS) and spectroscopic THz imaging at 201 and 590 GHz. The work shows that it is possible to distinguish between normal and cancerous regions in dried and paraffin-embedded samples. Plots of absorption coefficient α and refractive index n of normal and cancer affected tissues, as well as 2-D transmission THz images are presented and the conditions for discrimination between normal and affected tissues are discussed.

The detection of cancer at the dysplasia stage is one of the most important goals in biomedical research. Optical techniques, specifically diffuse reflectance and intrinsic fluorescence, may improve the ability to detect gastrointestinal (GI) cancers, since they have exquisite sensitivity to some intrinsic biomarkers present on the tissues. This work follows the research that has been done towards the implementation of a spectroscopy microsystem for the early detection of GI cancers. For that purpose, the behavior of the fluorescence signal, at different temperatures and considering the most important biomarkers in GI malignancy detection, was studied and presented.

An approximated technique to optimize the gain profile of multi-pump broadband hybrid amplifiers (Raman+EDFA) under residual pump recycling is applied to a WDM system. The Optimized hybrid amplifier configurations with multi-pumping were analyzed considering different number of input channels in order to check the global gain saturation and the changes in the global gain profile that occur due to signal-pump, signal-signal, and pump-pump interactions. This work extends the optimization of the gain profile from Raman+EDFA hybrid amplifiers and studies the signal-signal interactions, signal-pumping and pumping-pumping WDM systems. Multiple input channels allowed the gain characterization of the Raman+EDFA hybrid amplifier in terms of global gain, ripple, and noise figure considering applications for WDM systems.

We perform a thorough performance and complexity analysis of a recently proposed Volterra series nonlinear equalizer (VSNE) for digital post-compensation of nonlinear fiber impairments in high-speed and long-haul coherent optical communication systems. Using a maximum absolute value selection criteria, we implement a pruning strategy for the matrix-based VSNE and compare its performance/complexity with the symmetric VSNE (symVSNE) and simpli ed VSNE (simVSNE) algorithms. The theoretical analysis is supported by simulation results obtained for a single-channel 224 Gb/s PM-16QAM transmission system with a signal propagation distance of 1920 km.

In this paper, the implementations of clock and carrier recovery in digital domain are analyzed. Hardware implementation details, resources estimation and real-time results are presented. Analog-to-Digital Converters (ADC), operating at 1.25Gsa/s, and a Virtex-6 Field-Programmable Gate Array (FPGA), have been used, allowing the implementation of a real-time Quadrature Phase Shift Keying (QPSK) system operating at 1.25Gb/s. The real-time mode operation is successfully demonstrated over 80 km of Standard Single Mode Fiber (SSMF).

In this paper are presented three optical fiber sensors for carotid pulse wave acquisition. Two probes are based on silica fiber Bragg gratings and the other is intensity-based using plastic optical fibers. Starting with feasibility tests of such measurements with FBG sensors, the sensors evolution was towards a simple method with a lower cost sensor. The sensors were full characterized and some human tests were performed. The results showed a fair compromise between easiness of applicability and technician training, as well as good pressure wave acquisition performance.

A small dimension, real-time readout dosimeter is desirable for specific applications in medical physics as for example, dose measurement in prostate brachytherapy. This particular radiotherapy procedure consists in the permanent deposition of low energy, low-dose and low-dose rate small sized radioactive seeds. We developed a scintillating fiber optic based dosimeter suitable for in-vivo, real-time low dose and low dose rate measurements. Due to the low scintillation light produced in the scintillating fiber, a high sensitive and high gain light detector is required. The Silicon Photomultipliers are an interesting option that allowed us to obtain good results in our studies.

An intrinsic fiber optic dosimeter (FOD) targeted to nuclear applications is presented. The proposed real-time dosimeter provides dose information based on the historic record over time of the effects of ionizing radiation on single- and multimode pure silica fibers, and also on PMMA plastic fibers. The effect of ⁶⁰Co gamma irradiation on optical links based on silica and plastic fibers were assessed, considering thermal environment effects over a wide range of variation of the operating parameters. Cerenkov radiation and radiation-induced absorption effects were in focus. The corresponding distortion and spectral transmission degradation were evaluated over wide range of the operating parameters. Radiation induced attenuation (RIA) has shown a spectral band dependent behaviour up to 840 Gy dose levels. The performance of different fibers was assessed against the performance of non-irradiated fibers. From the measurements of dose rate and total dose imparted by ionizing radiation in the fibers we verified that fibers with radiation resistance issues showed wavelength-dependent radiation sensitivity increasing with dose rate. Upon evaluation of correlations between the total dose, the induced loss at various dose rates and different wavelengths, it was concluded that intrinsic fiber dosimeters can be used for dose rates in the range 4 - 28 Gy/min., typical of severe radiation environments.

An overview of the work done within the Mathematical Optics group at the CSIR’s National Laser Centre will be presented. We will focus on our work done in laser beam shaping with the use of digital holograms for the generation of superimposed optical fields which carry orbital angular momentum (OAM) and the development of OAM measurement techniques. Since OAM offers a potentially infinite-dimensional state space, much interest has been generated in its measurement for higher-dimensional quantum information processing to be realised. We generate superpositions of higher-order Bessel beams and show that even though we can create a field which carries no overall OAM, we can still witness an angular rotation in the intensity profile of the beam. We also develop a new OAM measurement technique by means of digital holograms.

We propose a novel face detection algorithm in order to improve higher detection rate of face-detector than conventional haar - adaboost face detector. Our purposed method not only improves detection rate of a face but decreases the number of false-positive component. In order to get improved detection ability, we merged two classifiers: adaboost and support vector machine. Because SVM and Adaboost use different feature, they are complementary each other. We can get 2~4% improved performance using proposed method than previous our detector that is not applied proposed method. This method makes improved detector that shows better performance without algorithm replacement.

In computational imaging by pattern projection a sequence of microstructured light patterns codified onto a programmable spatial light modulator is used to sample an object. The patterns are used as generalized measurement modes where the object information is expressed. Our paper makes two specific contributions within the field of single-pixel imaging through patterned illumination. First, we perform an analysis of the optical resolution of the computational image. This resolution is shown not to be limited at all by the optical quality of the collection optics. This result is proved by using a low NA microscope objective for imaging at a CCD camera. Spatial frequencies that are not transmitted through this low quality optics are demonstrated to be present in the retrieved image through patterned illumination. Second, we experimentally demonstrate the capability of our technique to properly recover an image even when an optical diffuser is located in between the sample and the single-pixel detector.

There are several factors such as the chosen optical source, central wavelength, spectral bandwidth, spectrometer optical components and the detector specifications that affect the overall performance of a spectral domain optical coherence tomography (SD-OCT) imaging system. Among these factors a good design and implementation of the spectrometer is of paramount importance as it directly affects the system resolution, sensitivity fall-off, maximum imaging depth, SNR and in general the system performance. This study demonstrates the design steps and some considerations during the design of a spectrometer. The imaging performance of this design is assessed. The obtained experimental results prove an improvement of the overall performance of the common path SD-OCT imaging system and agree with the expected outcome from the design stage.

In the paper, we show that the nonlinear spatial non-linear equivalency functions on the basis of continuous logic equivalence (nonequivalence) operations have better discriminatory properties for comparing images. Further, using the equivalent model of multiport neural networks and associative memory, (including matrix-matrix and matrix-tensor with adaptive-weighted correlation, multi-port neural-net auto-associative and hetero-associative memory (MP NN AAM and HAM ) and the proposed architecture based on them, we show how we can modify these models and architectures for space-invariant associative recognition and clustering (high performance parallel clustering processing) images. We consider possible implementations of 2D image classifiers, devices for partitioning image fragments into clusters and their architectures. The main base unit of such architectures is a matrix-matrix or matrix-tensor equivalentor, which can be implemented on the basis of two traditional correlators. We show that the classifiers based on the equivalency paradigm and optoelectronic architectures with space-time integration and parallel-serial 2D images processing have advantages such as increased memory capacity (more than ten times of the number of neurons!), High performance in different modes . We present the results of associative significant dimension (128x128, 610x340) image recognition - renewal modeling. It will be shown that these models are capable to recognize images with a significant percentage (20- 30%) damaged pixels. The experimental results show that such models can be successfully used for auto-and heteroassociative pattern recognition. We show simulation results of using these modifications for clustering and learning models and algorithms for cluster analysis of specific images and divide them into categories of the array. Show example of a cluster division of image fragments, letters and graphics for clusters with simultaneous formation of the outputweighted spatial allocated images for each cluster. Show results of other of modeling experiments with images of large dimension, such as clustering fragments (blocks 7x 7, 3x3, 15x15 and other sizes), 610x340 elements images into 8 clusters. We show that it is the use of nonlinear processing and nonlinear functions improves the quality of classification and image recognition. We offer criteria for the quality evaluation of patterns clustering with such MP NN AAM. It is shown that time of learning in the proposed structures of multi-port neural net classifier / categorizer-clustering (MP NN C) on the basis of equivalency paradigm, due to their multi-port, decreases by orders and can be, in some cases, just a few epochs. Other experimental data is also shown.

The phenomenon of dynamic speckle allows for non-invasive whole-field detection of physical or biological activity in objects through statistical description of laser speckle dynamics. Effective way to improve the statistical analysis is generation of controlled speckle patterns. SLM implementation of an optical simulator of dynamic speckle patterns is proposed by feeding a correlated sequence of 2D random phase distributions to the phase-only SLM. Atthevarying in space correlation radius of the phase fluctuations in the successive frames, the SLM produces regions of different activity on a screen under laser illumination. Feasibility of the proposed approach is proved both by simulation and experiment.

Optical non-invasive inspection tools and methods had expensively proven, for several decades now, their invaluable importance in the preservation of cultural heritage and artwork. In this paper we will report on an optical non-invasive microtopographic characterization work on pre-historical and pre-colonial ceramics and pottery of tribes in the Paranaiba valley in Minas Gerais, Brazil. The samples object of this work were collected at the Inhazinha archeological site (19º 10'00" S / 47° 11'00" W) in the vicinity of Perdizes municipality in transition between the West mining area and the “triangle” area in the center of Brazil. It is a hilly region (850m high) traversed by a number of rivers and streams tributary of Araguari river like Quebra Anzol river and Macaúba and Olegário streams. The Inhazinha site’ excavations are part of the Project Jigsaw Hook which since 1980 aimed the establishment of a chrono-cultural framework associated with the study of the socio-cultural dynamics corresponding to successive occupations of hunter-recollector-farmer’ tribes in prehistoric and pre-colonial times in the Paranaíba valley in Minas Gerais, Brazil. Two groups of indigenous Indian occupations were found. Both of the pre-colonial period dated at 1,095 ± 186 years ago (TL-FATEC/SP for Zone 1) and of the early nineteenth century dated at 212 ± 19 years ago (EMS-CENA-USP/SP) and 190 ± 30 years ago (C14- BETA/USA) in Zone 2 seemingly occupied by southern Kayapós tribes. The pottery found is decorated with incisions with different geometric distributions and levels of complexity.

One important key to improve the bulk-heterojunction photovoltaics (BHJs) is the fill-factor (FF). In this work, a study of the FF dependence factors on BHJs with an active layer of MEH-PPV / PCBM is made. The FF changes from 20% to 70%, depending on the current – voltage behavior and on the photovoltaic equivalent circuit parameters changes (parallel and series resistances, voltage open circuit, short circuit current and photocurrent). The efficiency changes from 1% to 5%. A theoretical simulation for FF optimization is made allowing a better understand of the physical process involved in the BHJ that modulates such parameter.

Holographic polymer dispersed liquid crystals (H-PDLC) are made by holographic recording in a photo-polymerization induced phase separation process in which the liquid crystal molecules diffuse to dark zones in the diffraction grating. The devices with H-PDLC materials develop a dynamic behavior that may be modified by means of an electric field. We study a photopolymer formulation with high diffraction efficiency but with the problem of high electric conductivity. We use a bleaching post-exposure treatment to obtain devices with a better electro-optical performance.

Random access memories (RAM) are fundamental in conventional electronic switches and routers to manage short-term congestion and to decrease data loss probabilities. Switches in all-optical networks (AONs), however, do not have access to optical RAM, and therefore are prone to much higher loss levels than their electronic counterparts. Fiber-delay-lines (FDLs), able to delay an optical data packet a fixed amount of time, have been proposed in the literature as a means to alleviate those high loss levels. However, they are extremely bulky to manage, so their usage introduces a trade-off between practicality and performance in the design and operation of the AON. In this paper we study the influence that FDLs have in the performance of flows crossing an all-optical switch that acts as their bottleneck. We show how extremely low numbers of FDLs (e.g., 1 or 2) can help in reducing losses by several orders of magnitude in several illustrative scenarios with high aggregation levels. Our results therefore suggest that FDLs can be a practical means of dealing with congestion in AONs in the absence of optical RAM buffers or of suitable data interchange protocols specifically designed for AONs.

In this work a mixed integer optimization linear programming (MILP) model applied to IP over WDM networks, in order to reduce network energy consumption. Simulations were made based on a real network topology as well as on forecasts of traffic matrix based on statistical data from 2005 up to 2017. Several techniques were tested an the bypass technique yielded up to 88% savings, as well as absence of transponders between IP and WDM layer potentially saving up to 48%, by shortest path routing technique. Energy aware routing optimization model, has led to an overall reduction in consumption up to 51% in 2017.

The convergence of new technologies in the digital world has made devices with internet connectivity such as televisions, smatphone, Tablet, Blu-ray, game consoles, among others, to increase more and more. Therefore the major research centers are in the task of improving the network performance to mitigate the bottle neck phenomenon regarding capacity and high transmission rates in information and data. The implementation of standard HbbTV (Hybrid Broadcast Broadband TV), and technological platforms OTT (Over the Top), capable of distributing video, audio, TV, and other Internet services via devices connected directly to the cloud. Therefore a model to improve the transmission capacity required by content distribution networks (CDN) for online TV, with high-capacity optical networks is proposed.

We theoretically investigate the optical response of ensembles of polarizable metallic nanoparticles (NPs) that form (i) submonolayer films considered as 2D systems, and (ii) thin 3D films where NPs are embedded in a dielectric matrix. In both cases we find that short-range clustering leads to a broadening and a spectral shift of the absorption band related to the surface plasmon resonance in inividual NPs. We show that clustering can help achieving spectrally broad surface plasmon resonance (SPR) bands, especially if NPs aggregate into fractal clusters, which can be interesting for some applications, such as SERS. In particular, submonolayer films on NPs generated using the dillusion-limited aggregation algorithm, produce sizable and spectrally broad absorption, which can be tuned to the visible range by choosing an appropriate substrate. Calculated results for thin 3D films are compared to experimental data obtained for Au=TiO₂ nanocomposite layers produced by reactive co-sputtering