This PDF file contains the front matter associated with SPIE Proceedings Volume 9441, including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Even though a nanoparticle is much smaller than the wavelength used for their spatial confinement in an optical trap, the nanoparticle shape strongly influences force interaction between the light and the nanoparticle. The nanoparticle orientation with respect to the beam propagation and polarization strongly influences the light scattering pattern and thus the acting optical forces and torques upon the nanoparticle. We demonstrate experimental and theoretical results concerning the optical trapping of metal nanoparticles and the influence of the trapping wavelength on shaped plasmonic nanoparticles.

In the field of optical micromanipulations the optical landscapes are also used for sorting of micro (nano) particles. This sorting processes are actuated by intense laser fields devised in an arrangement to a particular sorting problem. The primary forces acting on the particles are given by gradient and scattering forces resulting from the design of the optical landscape. Anyway the field scattered by particles gives rise to additional optical forces. This effect is called optical binding and the particles due to their mutual forces induced by light may create an optically bound structure. We study these scattering and forces numerically by the Coupled dipole method (CDM). With this method we can model groups of arbitrary shaped particles of different composition even inhomogeneous. We are interested in asymmetric configurations because the net force acting on the particles is nonzero despite of the group of particles remains optically bound. By these means we offer a new sorting mechanism based on asymmetric scattering of optically bound particles.

Following the Keplerian idea of radiative forces one would intuitively expect that an object illuminated by sunlight radiation or a laser beam is accelerated along the direction of the photon flow. Such radiation pressure forms the basis for the concept of solar sail, or laser acceleration of micro-particles. In contrast, a hypothetical optical field known from the realm of science-fiction as the "tractor" beam attracts the matter from large distances against the beam propagation. We present a geometry of such"tractor" beam in micro-scale and experimentally demonstrate how it acts upon spherical micro-particles of various sizes or optically self-arranged structures of micro-particles.

Micro-particles with higher refractive index than the surrounding medium irradiated by a laser beam are pushed by optical forces towards places having the highest local optical intensity. These intensity maxima are usually created by focusing a laser beam using a microscope objective with high numerical aperture. A convenient alternative offers usage of light patterns created by an interference of collimated beams. This way tens or hundreds of optical traps are created in a spatially well-organized structure (also called as optical lattice) which is well-suited for studies of quasi-crystalline structures, targeted delivery of living cells or particle sorting and fractionation. Hereby, we investigate theoretically and experimentally properties of optical traps organized in hexagonal, rectangular and calleidoscopic structures created by interference of 3 up to 8 collimated laser beams.

Metal-dielectric core-shell particles represent promising tools in nanoplasmonics. In combination with optical tweezers they can be manipulated in a contactless way through fluid and their plasmonic properties can be used to probe or modify the local environment. We perform a numerical parametric study to find the particle geometry and material parameters under which such particle can be stably confined in optical tweezers. We use the theory based on Mie scattering in the focal field of an ideal water immersion objective of numerical aperture NA=1.2. For very thin metal layers we find that strong trapping on the optical axis can be achieved.

We have devised an analytical and sorting system combining optical trapping with Raman spectroscopy in microfluidic environment, dedicated to identification and sorting of biological objects, such as living cells of various unicellular organisms. Our main goal was to create a robust and universal platform for non-destructive and non-contact sorting of micro-objects based on their Raman spectral properties. This approach allowed us to collect spectra containing information about the chemical composition of the objects, such as the presence and composition of pigments, lipids, proteins, or nucleic acids, avoiding artificial chemical probes such as fluorescent markers. The non-destructive nature of this optical analysis and manipulation allowed us to separate individual living cells of our interest in a sterile environment and provided the possibility to cultivate the selected cells for further experiments. We used a mixture of polystyrene micro-particles and algal cells to test and demonstrate the function of our analytical and sorting system. The devised system could find its use in many medical, biotechnological, and biological applications.

We introduce tunable optofluidic microlasers based on optically stretched or thermally modified, dye-doped emulsion droplets of liquid crystals (LC) confined in a dual-beam optical trap. Droplets were created in microfluidic chips or by shaking. Optically trapped microdroplets emulsified in water and stained with fluorescent dye act as an active ultrahigh-Q optical resonant cavity hosting whispering gallery modes (WGMs). Tuning of the laser emission wavelength was achieved by a controlled deformation of the droplet shape using light-induced forces generated by dual-beam optical trap and by thermal changing of the order in the LC.

Magnetic fluids (ferrofluids) consist of magnetic nanoparticles (diameter ~10nm) which are dispersed in a liquid, often with the use of surfactants. They were first developed by NASA to address the unique requirements of moving liquid fuel in microgravity conditions. With a help of a holographic optical tweezers, interaction of magnetic nanoparticles with strongly focused laser beam was observed. When the light intensity was high enough, magnetic nanoparticles were removed from the beam center and they formed a dark ring. Creation process lasts less than 330μs and cannot be observed precisely even with ultrafast camera. Such rings exist when the laser beam is affecting the sample and disappear (with a lifespan of 10’th second range) after the laser is switched off. Moreover, when several rings are created simultaneously, complex interactions between them can be observed. In this work, the results of our experiments will be presented with hypotheses about the physical background of such a behavior.

High-power mid-infrared (mid-IR) fiber-based supercontinuum (SC) sources are considered a key enabling technology for numerous applications in such important areas as microscopy, spectroscopy, medicine, and military. Most of the applications require robust, high power, sources emitting radiation in the 2-4 μm spectral band. To meet these requirements, a suitable design of SC laser source has to be applied. High-power SC generation in soft glass fibers is a relatively new research domain and the number of research groups dealing with this topic is still very small. Nevertheless, the results already achieved are very impressive and promising regarding practical applications of SC sources. In this paper I briefly reviewed the developments in scaling up the output average power and spectral coverage in the mid-IR region in fluoride fiber-based SC sources that have been achieved recently by my group.

Thulium-doped fiber lasers are attractive light sources in the infrared region at around 2 micrometers. Their slope efficiency may reach 70 % and thus they are challenging the well-established ytterbium-doped fiber lasers operating at around 1 micrometer. Two-micrometer radiation sources have many advantages over the one-micrometer sources, e.g., better eye-safety, relaxed non-linear limits and more efficient material processing for some types of materials. Particularly important applications of lasers at 2 micrometers are in nonlinear frequency conversion to mid-infrared wavelength. In this paper we review our recent progress in research of thulium-doped fibers and fused fiber components.

To homogenize inversion profiles and mitigate thermo-optic effects in high-power, end-pumped lasers the optimal spatial profile of pump beam should be close to ‘top-hat’ one, whereas typical pumping beams have Gaussian-like profiles. The aim of work was to examine feasibility of laser beam transformation with the use of a beam shaper consisted of a pair of aspheric refractive elements. Two beam shapers (with magnification m = 0.4, 0.8 respectively) for transformation of Gaussian profile to Super-Gaussian were designed and fabricated applying Magneto-Rheological Finishing technology. Both elements were experimentally verified for diffraction limited and partially coherent laser beams. The analytical model based on Fourier transform plane wave decomposition was applied for verification of experiments and to determine the performance of fabricated elements.

Temperature dependence of spectroscopic characteristics as well as laser properties of the bulk Bridgman-grown Fe:ZnSe and Fe,Cr:Zn_1-xMg_xSe (x = 0.19, 0.38) active media were investigated under room and various cryogenic – liquid nitrogen - temperature . The pumping was provided by Er:YAG laser radiation at the wavelength of 2.94 μm, with energy 15 mJ in 110 ns Q-switched pulse or 200 mJ in 220 μs free-running pulse. The 55 mm long hemispherical resonator was formed by a dichroic pumping mirror (T = 92 % @ 2.94 μm and R = 100% @ 4.5 μm) and a concave output coupler (R = 95 % @ 4.5 μm, r = 200 mm). A strong dependence of generated output radiation parameters on temperature was observed for all samples.

We present a diode-pumped actively mode-locked Tm:YLF laser. Continuous-wave mode-locked regime was achieved using an acousto-optic modulator and a stable train of pulses with 150 MHz repetition rate, 220 ps pulse width and 1.2 W average output power at 1.91 μm in a nearly diffraction-limited beam was obtained. Laser characteristics in the freerunning regime with both continuous and pulsed pumping as well as humidity-related issues are also reported.

A single and double-bounce grazing-incidence Nd:YVO₄ laser is presented. The output pulse energy of ~20 mJ with slope efficiency reaching up to 24.5% was achieved. The beam quality parameter M² was 1.25.

In this work, we would like to demonstrate our results on performing (6+1)x1 tapered fiber bundle combiners using a trielectrode fiber splicing system. In our combiners we have used 9/80 μm (core/clad) diameter fibers as single-mode signal input ports. Using this fiber, instead of a conventional 9/125 μm single-mode fiber allowed us to reduce the taper ratio and therefore significantly increase the signal transmission. We have also performed power combiner which is based on the LMA fibers: input signal fiber 20/125μm and passive double clad fiber 25/300 μm at the output.

In this work, we have investigated operation of a quasi-continuously diode pumped Yb:YAG laser at room and cryogenic temperatures. In free-running regime, an increase in laser efficiency has been observed from 52 % optical-to-optical efficiency at room temperature to 69 % at 92 K. With passive mode-locking, the laser operated with higher efficiency and stability against Q-switching instabilities when the laser crystal was cooled to cryogenic temperatures. On the other hand, increase in pulse duration as a consequence of linewidth narrowing has been observed. At room temperature, pulses with duration of 2.8 ps were generated with 4 % optical-to-optical efficiency, compared to 11.8 ps pulse duration and 13 % optical-to-optical efficiency at 85 K.

V:YAG saturable absorber, developed mainly for 1.3 μm lasers Q-switching, was used as a passive Q-switch for the 1.03 μm Yb-doped YAG (10% Yb/Y, 3mm long) and LuAG (15% Yb/Lu, 1mm long) lasers. Longitudinally diode pumped gain medium together with the V:YAG crystal were placed inside the 22mm long hemispherical laser cavity. For Yb-doped crystal excitation fibre-coupled (fibre core diameter 100 μm) laser diode (max power amplitude 20W, emission wavelength 968 nm) was used. The laser diode was operating in a pulsed regime (repetition rate 10 Hz, pumping pulse width 2 ms) to reduce parasitic thermal effects inside the gain medium. Stable Q-switching was obtained for laser output coupler reflectivity 70% and V:YAG initial transmission 70% at Yb laser emission wavelength. For the both tested active media the parameters of the generated giant pulses were similar. Pulses with duration of 2.5 ns (FWHM), energy about 0.3 mJ, and peak power up to 120kW were generated. The maximal Q-switched pulses repetition rate inside the single pumping pulse was 6.6 kHz in case of Yb:YAG and 8.6 kHz in case of Yb:LuAG. The beam transversal profile was close to the fundamental Gaussian mode. The output was partially polarized.

We present first to our knowledge self-starting graphene-chitosan based ultrafast fiber laser setup. Graphene-chitosan composite placed between two fibres connectors is saturable absorber in demonstrated setup and is responsible for modelocking operation. Laser is built with polarization maintaining fibres which grants self-start feature. Laser produces ~300 fs soliton pulses centered at 1566 nm with 10 nm FHWM optical bandwidth. Time bandwidth product of demonstrated laser is 0.37. Repetition rate of 42 MHz and average output power of 1.2 mw corresponds to pulse energy and peak power of 20 pJ and 62 W, respectively. As an active media in laser Erbium-doper fiber was used. Presented setup proves graphene is novel promising material for ultrafast lasers production at worldwide scale.

In this work, femtosecond pulse generation in Er-doped fiber laser using graphene oxide (GO) paper based saturable absorber (SA) is presented. The article includes the characterization of optical properties of prepared SA material and detailed description of the laser performance. Stable mode-locking operation was achieved, with 515 fs soliton pulses centered at 1559 nm. The GO paper SA is characterized by 5.4% modulation depth and 155 MW/cm² of saturation intensity. The nearly wavelength-independent linear absorption combined with straightforward fabrication process make it a suitable material for application as a SA in low-power mode-locked fiber lasers operating in various spectral ranges.

The main aim of this work is oriented towards preparation and spectral properties evaluation of optical frequency references for laser standards – molecular iodine cells. These references represent the crucial part of setups for practical realization of the meter unit – highly stable laser standards. Furthermore, not only in the most precise laboratory instruments, but also in less demanding interferometric measuring setups the frequency stabilization of the lasers throught the absorption in suitable media ensure the direct traceability to the fundamental standard of length. A set of absorption cells filled with different amounts of molecular iodine (different saturation pressure point of absorption media) was prepared and an agreement between expected and resulting spectral properties of these cells was observed and evaluated. The usage of borosilicate glass instead of common fused silica as a material for cells bodies represents an approach to simplify the manufacturing technology process and also reduces the overall cell costs. A great care must be taken to control/avoid the risk of absorption media contamination by impurities releasing from the cell walls. We introduce an iodine purity and spectral properties evaluation method based on measurement of linewidth of the hyperfine transitions. The proposed method was used for verification of great iodine purity of manufactured cells by comparison of spectral properties with cells traditionally made of fused silica glass with well known iodine purity. The results confirmed a great potential of proposed approaches.

The similarities and differences of spatial shifts to the centroids of reflected beams, and their (optical vortex) structure are discussed and reviewed. The differences between vortex-induced shifts to a beam centroid on reflection, and to the distribution of the vortices themselves is discussed. We conclude by discussing the shifts of a reflected beam containing a single anisotropic vortex.

We demonstrate the vortex point spread function (PSF) whose shape and the rotation sensitivity to defocusing can be controlled by a phase-only modulation implemented in the spatial or frequency domains. Rotational effects are studied in detail as a result of the spiral modulation carried out in discrete radial and azimuthal sections with different topological charges. As the main result, a direct connection between properties of the PSF and the parameters of the spiral mask is found and subsequently used for an optimal shaping of the PSF and control of its defocusing rotation rate. Experiments on the PSF rotation verify a good agreement with theoretical predictions and demonstrate potential of the method for applications in microscopy, tracking of particles and 3D imaging.

We propose a fast, simple and experimentally robust method for reconstructing background-rejected optically-sectioned microscopic images using two-shot structured illumination approach. Innovative data demodulation technique requires two grid-illumination images mutually phase shifted by π (half a grid period) but precise phase displacement value is not critical. Upon subtraction of the two frames the input pattern with increased grid modulation is computed. The proposed demodulation procedure comprises: (1) two-dimensional data processing based on the enhanced, fast empirical mode decomposition (EFEMD) method for the object spatial frequency selection (noise reduction and bias term removal), and (2) calculating high contrast optically-sectioned image using the two-dimensional spiral Hilbert transform (HS). The proposed algorithm effectiveness is compared with the results obtained for the same input data using conventional structured-illumination (SIM) and HiLo microscopy methods. The input data were collected for studying highly scattering tissue samples in reflectance mode. In comparison with the conventional three-frame SIM technique we need one frame less and no stringent requirement on the exact phase-shift between recorded frames is imposed. The HiLo algorithm outcome is strongly dependent on the set of parameters chosen manually by the operator (cut-off frequencies for low-pass and high-pass filtering and η parameter value for optically-sectioned image reconstruction) whereas the proposed method is parameter-free. Moreover very short processing time required to efficiently demodulate the input pattern predestines proposed method for real-time in-vivo studies. Current implementation completes full processing in 0.25s using medium class PC (Inter i7 2,1 GHz processor and 8 GB RAM). Simple modification employed to extract only first two BIMFs with fixed filter window size results in reducing the computing time to 0.11s (8 frames/s).

We demonstrate capabilities of near-field scanning optical microscopy (NSOM) in collection and illumination mode. NSOM in collection mode was used for high resolution characterization of optical field of patterned light emitting diodes. In the scanned near field, we resolved enhanced emission from patterned regions with high resolution images of emitting surface. Also NSOM in illumination mode was used for patterning of predefined structures on semiconductor surfaces. For the diode patterning the electron beam direct writing lithography was used. Using NSOM lithography we prepared predefined planar structures in GaP surface. In the small open areas of predefined surface structure GaP nanowires were grown.

We consider an optical system in which the optical vortex moves inside the focused Gaussian beam. The vortex movement is due to the vortex lens inserted in front of the focusing objective. We gradually shift the vortex lens along the x-axis which is perpendicular to the axis of laser beam propagation (z-axis). This causes that in the image plane vortex moves along a straight line but the line inclination depends on the position of the observation plane. There is a characteristic position of the observation plane, in which the vortex trajectory is perpendicular to the vortex plate shift. We call this plane a critical plane. The critical plane is sensitive to small phase variations which can be introduce by a transparent sample. We propose a way of retrieving the phase profile (at the critical plane) of such a beam. Our procedure is based on the Fourier transform phase demodulation method. We also investigate how the system reacts to the known phase variations introduced into the critical plane.

In this work soft X-ray (SXR) and extreme ultraviolet (EUV) laser-produced plasma (LPP) sources employing Nd:YAG laser systems of different parameters are presented. First of them is a 10-Hz EUV source, based on a double-stream gaspuff target, irradiated with the 3-ns/0.8J laser pulse. In the second one a 10 ns/10 J/10 Hz laser system is employed and the third one utilizes the laser system with the pulse shorten to approximately 1 ns. Using various gases in the gas puff targets it is possible to obtain intense radiation in different wavelength ranges. This way intense continuous radiation in a wide spectral range as well as quasi-monochromatic radiation was produced. To obtain high EUV or SXR fluence the radiation was focused using three types of grazing incidence collectors and a multilayer Mo/Si collector. First of them is a multfoil gold plated collector consisted of two orthogonal stacks of ellipsoidal mirrors forming a double-focusing device. The second one is the ellipsoidal collector being part of the axisymmetrical ellipsoidal surface. Third of the collectors is composed of two aligned axisymmetrical paraboloidal mirrors optimized for focusing of SXR radiation. The last collector is an off-axis ellipsoidal multilayer Mo/Si mirror allowing for efficient focusing of the radiation in the spectral region centered at λ = 13.5 ± 0.5 nm. In this paper spectra of unaltered EUV or SXR radiation produced in different LPP source configurations together with spectra and fluence values of focused radiation are presented. Specific configurations of the sources were assigned to various applications.

The optical frequency comb has become an indispensable tool for high precision spectroscopy. Also experiments in the field of ultrafast physics rely on the frequency comb technique to generate precisely controlled attosecond optical pulses by means of the high-order harmonic generation. However, in order to generate even shorter laser pulses or to apply this technique in investigations of nuclear structure, combs of frequencies of the order of MeV are necessary. It seems that it may not be possible to achieve such photon energies by high-order harmonic generation. In this context the possibility of the generation of Thomson and Compton-based frequency combs is presented. Diffraction of generated radiation by a sequence of laser pulses and its analogy to the diffraction grating is elucidated.

We present an innovative soft X-ray polarimeter and spectrometer SOLPEX, the instrument to be mounted aboard the International Space Station (ISS) in 2015/2016. The SOLPEX will be composed of three individual measuring units: the soft X-ray polarimeter with 1-2% linear polarization detection limit, a fast-rotating drum X-ray spectrometer with very high time resolution (0.1s) and a simple pin-hole soft X-ray imager-spectrometer with moderate spatial (~20arcsec), spectral (0.5 keV) and high time resolution (0.1s). This set of instruments will provide unique opportunity to complement the efforts to reliably measure the X-ray polarization and contribute towards understanding the physics of solar flares. The standard flare model states that electrons are being accelerated in specific regions of the corona at or near magnetic reconnection site and then propagate along reconnected magnetic field lines toward the atmospheric denser layers. There, they are decelerated and lose their energy mainly through the bremsstrahlung process. Deposited energy is readily converted to directed evaporation of the plasma to be detected through the Doppler-shifted emission lines in extreme ultraviolet and soft X-ray spectral ranges Due to highly anisotropic character of impulsive phase electron beams, resulting emission is expected to be polarized. Both these processes: bremsstrahlung emission of supposedly polarized X-ray flux and accompanying plasma evaporation velocities are to be simultaneously observed by the proposed SOLPEX instruments.

We discuss a chain of three nonlinear oscillators excited by an external field. We show that during system’s evolution squeezed states can be generated in all three modes. Such generated squeezing appears simultaneously in all modes but for different quadratures. We show that degree of the squeezing and time of its appearance depend on the values of the parameters determining strengths of external and internal couplings and dumping of the system.

The generation of photon pairs inside metallo-dielectric layered media by spontaneous parametric down conversion is highly efficient. A theoretical model of spontaneous parametric down conversion based on vectorial quantum-mechanial approach is used to obtain spatial, frequency and temporal photon-pair characteristics. As an example, a structure consisting of eleven alternating Galium-Nitride and silver layers is analyzed. Strong constructive interference of the sub-frequency fields results in narrow spatial and frequency distributions of photon-pairs emitted at high generation rates. Photon pairs are mainly created in Galium-Nitride layers, the silver layers serve as a linear reflector.

A model of a nonlinear, damped kicked oscillator is discussed. For such a model intra-mode correlations described by mutual information parameter I[α] based on the Wehrl entropy are considered. Furthermore, the system’s quantum evolution is compared to its classical counterpart. The mutual information parameter is discussed as a proposal for quantum chaos’ witness.

We present a two-dimensional cellular automata (CA) model involving a set of two-level subsystems (”atoms”) which are located in square lattice, and can emit and absorb quanta of energy. Our model is an extension of the one-dimensional model discussed in the papers.1, 2 We concentrate on the spreading of disorder in the system and propose entropic parameters describing two-dimensional system’s dynamics. We show that whereas entropic measure undergoes saturation effects, its counterpart normalized per number of excitations can exhibit exponential grow.

Using the characteristic function of a twin beam composed of both paired and noise components we derive the corresponding statistical operator in the Fock-state basis. Applying the Peres-Horodecki criterion for a partially transposed statistical operator, we determine the negativity of the twin beam to quantify entanglement. In parallel, nonclassicality of the twin beam is quantified by nonclassical depth which is the acceptable amount of noise photons that preserves non-classicality manifested by negative values of the Glauber-Sudarshan quasiprobability function. The connection between entanglement and non-classicality is discussed considering the noise present either in one or both fields constituting the twin beam. Also the state of dimensionality via the Schmidt number as well as von Neumann entropy of the twin beam is analyzed.

A new technique for processing complex fringe patterns containing multiple fringe sets is presented. It can be used either to filter out parasitic fringes or to extract two separate, superimposed fringe families with information encoded in their phase. The method is based on two dimensional continuous wavelet transform. A new ridge extraction algorithm utilizing wavelet scale and angle coordinate maps extrapolation procedure is proposed. This procedure allows to analyze fringe patterns with locally overlapping spectra, is fully automatic and does not require user involvement. Method validity, accuracy and robustness are confirmed using numerical simulations.

In the interferometry, the Fourier Transform Method (FTM) is one of the efficient ways for an interferogram evaluation and it can be used in many practical applications. Fourier transform used in the process of phase reconstruction gives an opportunity to eliminate some unwanted phenomena which are carried in the interferogram due to the process of measuring – for example a random noise of the sensor or a variation in the background intensity. Moreover, reconstructed phase can be obtained only from one registered interferogram, thus this method can be simply implemented in a real measurement process. During the FTM interferometry, an interferogram is reconstructed in several steps. Viewed from a mathematical part and a software implementation, the most complicated is a step called unwrapping; discontinuous image – as a result of atan function – is processed and the continuous phase is retrieved. This work presents a modified solution of an interferogram phase reconstruction without using the unwrapping process – the phase is obtained from its gradient using the piecewise quadratic function.

The surface flatness of transparent plates is frequently tested in Fizeau and Twyman-Green interferometers. In case of quasi-parallel plates, however, a common problem is the additional reflection from the plate rear surface and the occurence of three-beam interference. Conventional methods of interferogram analysis such as temporal phase shifting or Fourier transform fail when the three overlapping fringe sets are present in the image. Our method of deriving optical parameters of the plate requires recording two interferograms: a two-beam interferogram without a reference beam and the three-beam interference one. The images are processed using single-frame techniques only and information about shape of both surfaces and optical thickness variations of the plate is retrieved. Unwanted parasitic fringes introduced by the glass plate protecting the CCD matrix in the camera are also handled using recently developed special smoothing technique. The proposed method is based on algorithmic solution and does not require modification of a sample or the optical setup. The measurement procedure and the detailed image processing path will be presented on the example of quasi-parallel plate interferograms recorded in the Twyman-Green setup.

We discuss a recently proposed method of the implicit smoothing splines in the context of the interferometric fringe pattern processing. The algorithm extends classic smoothing spline method to the case of the measurements being in some non-trivial functional relation to the estimated distribution, i.e., to the case of the implicitly given data. This is the case of the phase estimation based on the intensity of the related fringe pattern. While there are certain preprocessing complications involved in the application of the implicit smoothing splines, the method offers very accurate continuous (unwrapped) phase estimation and outperforms well-established fringe pattern analysis tools. In this paper we present theoretical background of the implicit smoothing splines as well as numerical results related to their application to the fringe pattern phase estimation problem.

Lasers provide us with unique kind of light – coherent light. Besides being the keystone of historical interferometric measuring methods, coherent waves, now accessible in a very easy way, become a base of new optical measuring and information processing methods. Moreover, holographic recording seems today to have become a common term, even among common, not especially optically educated people. The presentation deals with our attempt to take our students' interest in the coherence of light and getting them familiar with the phenomenon, indeed.

In this article we show a fibre-optic device based on the Sagnac effect designed for measuring rotational motions which appear during seismic events. The experimental investigations of presented Autonomous Fiber-Optical Rotational Seismographs indicate that such devices keep the accuracy no less than 5.1·10^-9 to 5.5·10^-8 rad/s in the frequency band from 0.83 Hz to 106.15 Hz. Furthermore, their operations are controlled fully remotely via Internet. We present the comparison of results obtained by such system in the field test with a mechanical rotational seismometer which is mounted simultaneously in the seismological observatory in Książ, Poland.

White-light interferometry is an established and proven method for the measurement of the shape of objects. White-light interferometry is able to measure the shape of objects with optically smooth as well as optically rough surfaces. A major disadvantage of white-light interferometry is its low scanning velocity and the long measurement time related. We present a system that measures the shape of object with optically rough surface and can achieve the scanning velocity up to 100 μm/s with a standard frame rate of 25 Hz. The experimental results are shown.

Optical homogeneity of materials intended for optical applications is one of the criterions which decide on an appropriate application method for the material. The existence of a refractive index inhomogeneity inside a material may disqualify it from utilization or by contrary, provide an advantage. For observation of a refractive index inhomogeneity, even a weak one, it is convenient to use any of interferometric methods. They are very sensitive and provide information on spatial distribution of the refractive index, immediately. One can use them also in case when the inhomogeneity evolves in time, usually due to action of some external fields. Then, the stream of interferograms provides a dynamic evolution of a spatial distribution of the inhomogeneity. In the contribution, there are presented results of the analysis of interferograms obtained by observing the creation of a refractive index inhomogeneity due to illumination of thin layers of a polyvinyl-alcohol/acrylamide photopolymer and a plate of photorefractive crystal, lithium niobate, by light and a refractive index inhomogeneity originated at the boundary of two layers of polydimethylsiloxane. The obtained dependences can be used for studying of the mechanisms responsible for the inhomogeneity creation, designing various technical applications or for diagnostics of fabricated components.

Recent years have seen a rapid growth in demand for ultra high speed data transmission with end users expecting fast, high bandwidth network access. With this rapid growth in demand, data centres are under pressure to provide ever increasing data rates through their networks and at the same time improve the quality of data handling in terms of reduced latency, increased scalability and improved channel speed for users. However as data rates increase, present technology based on well-established CMOS technology is becoming increasingly difficult to scale and consequently data networks are struggling to satisfy current network demand. In this paper the interrelated issues of electronic scalability, power consumption, limited copper interconnect bandwidth and the limited speed of CMOS electronics will be explored alongside the tremendous bandwidth potential of optical fibre based photonic networks. Some applications of photonics to help alleviate the speed and latency in data networks will be discussed.

We describe fabrication process of optical waveguide structures such as multi-mode optical splitter and optical waveguide with surface Bragg grating in polydimethylsiloxane (PDMS). Technology based on drawing of thin photoresist fiber with diameter up to 100 μm was developed and optimized. In this way, fibers drawn from photoresist form cores of waveguides in PDMS slab. After removal of the photoresist, created air channels can be filled in with different liquids. We prepared multimode waveguide structures in PDMS composed of two PDMS materials with different refractive indices. Using this technology, also complicated waveguide structures were prepared as optical splitter and surface Bragg grating were prepared in PDMS material.

In this paper, capabilities of the fabrication technology for planar waveguide structures and devices in polydimethylsiloxane (PDMS) are presented. Direct laser writing in combination with imprinting technique was used to pattern photoresist layer as a master for imprinting process. In the next step, PDMS waveguide structures as channel waveguide, Y-branch waveguide splitter and ring resonator were imprinted. Finally, optical and morphological properties of prepared devices were investigated by confocal microscopy and atomic force microscopy.

A strain sensor that operates in the intensity domain by converting the wavelength information from the fiber Bragg grating sensor, into intensity variation is presented in this paper. The fiber-optic sensor system involves a highly birefringent fiber as a demodulation system and a FBG sensor which is used for strain measurement.

Optical fibers designed for high power laser radiation delivery represent important tools in medicine, solar systems, or industry. For such purposes several different types of glass optical fibers such as silica, sapphire, or chalcogenide ones as well as hollow-glass fibers, photonic crystal fibers and Bragg fibers have been investigated. Air-core Bragg fibers or photonic crystal fibers offer us the possibility of light transmission in a low dispersive material - air having a high damage threshold and small non-linear coefficient. However, preforms for drawing Bragg fibers can be fabricated by MCVD method similarly as preforms of standard silica fibers. In this paper we present fundamental characteristics of laboratory-designed and fabricated Bragg fibers with air cores intended for delivery of laser radiation at a wavelength range from 0.9 to 1.5 μm. Bragg fibers with different air core diameters of 5, 45 and 73 mm were prepared. The fiber core was surrounded by three pairs of circular Bragg layers. Each pair was composed of one layer with a high and one layer with a low refractive index with a contrast up to 0.03. Several laser sources emitting at 0.975, 1.06, and 1.55 μm were used as radiation sources. Attenuation coefficients, overall transmissions, bending losses, and spatial profiles of output beams from fibers were determined at these wavelengths. The lowest attenuation coefficient of 70 dB/km was determined for the 45 μm and 73 mm air-core fiber when radiation from a laser was launched into the fibers by using optical lenses. However, multimodal transmission has been observed in such condition. It has also been found that bending losses of such fibers are negligible for bending diameters higher than 15 mm.

We present the optical fiber sensor based on fused silica capillary as a sensing element spliced between the lead-in and lead-out singlemode (SM) fibers. In the region of the splice the cladding modes of capillary are excited from the fundamental mode of led-in SM fiber. The intermodal interference of the propagating cladding modes results in the formation of the resonant peaks in the transmission spectrum. With the variations of the external refractive index the shift of resonance wavelength of the peak can be observed. The sensitivity for the refractive index values around n=1.33 is observed and using the wet etching technique can be increased, what gives an assumption for its using in a biomedical sensing applications.

Polarization splitting performance of a special multi-component glass made dual – core microstructure optical fiber (DC MOF) was investigated in the near infrared region. The output dual-core intensity ratio changes were analyzed behind a rotating polarizer both in spectrally resolved and integrated manner under broadband femtosecond pulse excitation of the fiber in the C-band. The polarization angle dependence of the dual-core intensity ratio exhibited similar non-symmetrical character in the case of both camera and spectrometer registration method. The 70 nm broad femtosecond radiation allowed to set an optimal wavelength, at which the extinction ratio difference between the extreme cases was maximized with significantly higher value than by the spectrally integrated method. Non-proper polarization splitting performance was observed with angle distance different than 90° between the extreme cases for the both orthogonal input polarization directions. Afterwards, optimizing the input polarization angle the angle distance became the proper right-angle, which behavior is interpreted in terms of inhomogenously polarized fundamental supermodes supported also by numerical mode analysis of the investigated DC MOF.

In this paper, we review two main recently dominating applications of magneto-optics (MO). The first one is related to a unique MO non-reciprocity. For example, the MO non-reciprocity in the isolators enables complete transmission in the forward propagation direction, while it prevents spurious back-reflection, which is needed to preserve proper operation of active optical elements like lasers or amplifiers in optical systems. Local enhancement of MO activity by optical field concentration in nanostructured magneto-plasmonic and magneto-photonic systems opens new horizons in optical isolators, circulators, and switches. We will discuss enhancement of MO effects using surface magneto-plasmons in periodic grating and apply it to nonreciprocal isolating systems. The second main application of the magneto-optics is the characterization of magnetic multilayers, periodic systems, and nanostructures. MO techniques profit from high near-surface sensitivity to local magnetization, nondestructive character, ultrafast response, and possibility to measure all components of the magnetization vector by means of MO vector magnetometry. Furthermore, the MO Kerr effect allows the separation of magnetic contributions originating in different depths, different materials in multilayer systems as well as laterally modulated and self-organized nanostructures fabricated via modern nanotechnologies.

This paper deals with the study of thin silicon films deposited by plasma-enhanced chemical vapor deposition on the industrial iron-nickel alloy substrate. This approach is promising for fabrication of low-cost high-efficiency solar cells. The main aim is to characterize the intrinsic hydrogenated microcrystalline silicon layer which fulfills its role of the absorber and has a direct impact on the solar cell performance. The real-time ellipsometric data obtained during the material deposition in the reactor are used to study the composition of the grown material. Based on the designed optical model, the evolution of the material crystallinity as well as the thickness and composition of the surface roughness layer are established in addition to an estimation of the average growth rate. Transmission electron microscopy was used to obtain the images of material structure and to verify conclusions of optical modeling.

We report on the optical properties of plasmonic glasses which are metal-dielectric composites composed of metallic inclusions in a host dielectric medium. The investigated structures are of quasi-random nature, described by the pair correlation function, featuring a minimum center-to-center distance between metallic inclusions and long range randomness. Plasmonic glasses exhibiting short-range order only may be fabricated using bottom-up, self-assembly methods and have been utilized in a number of applications such as plasmonic sensing or plasmon-enhanced solar harvesting, and may be also employed for certain non-linear applications. It is therefore important to quantify their properties. Using theoretical methods we investigate optical of 1D, 2D, and 3D structures composed of amorphous distributions of metallic spheres. It is shown, that the response of the constituent element, i.e. the single sphere localized surface plasmon resonance, is modified by the scattered fields of the other spheres in such a way that its peak position, peak amplitude, and full-width at half-maximum exhibit damped oscillations. The oscillation amplitude is set by the particle density and for the peak position may vary by up to 0.3 eV in the optical regime. Using a modified coupled dipole approach we calculate the effective (average) polarizability of plasmonic glasses and discuss their spectra as a function of the dimensionality, angle of incidence and polarization, and the minimum center-to-center distance. The analytical model is complemented and validated by T-Matrix calculations of the optical cross-sections of amorphous arrays of metallic spheres obtained using a modification of the Random Sequential Adsorption algorithm for lines, surfaces, and volumes.

Refractive index sensors based on surface plasmon resonance (SPR) in a thin metal film deposited on an unclad core of a multimode fiber are presented. The sensing element of the fiber optic SPR sensors is a bare core of a step-index optical fiber made of fused silica with a double-sided sputtered gold film. First, an in-line transmissionbased sensing scheme with the fiber optic SPR probe is used. Second, a reflection-based sensing scheme with a terminated fiber optic SPR probe is employed. The fiber optic SPR probes have different lengths and the thickness of the sputtered gold film is about 50 nm. Both sensing schemes utilize a wavelength interrogation method so that the refractive index of a liquid is sensed by measuring the position of the dip in the transmitted or reflected spectral intensity distribution. As an example, the aqueous solutions of ethanol with refractive indices in a range from 1.333 to 1.364 are measured. For the transmission-based sensing scheme a polarization-dependent response is revealed.

A model of a surface plasmon resonance fiber-optic sensor with a double-sided metallic layer is presented. Most of such fiber optic sensing configurations are based on a symmetric circular metal layer deposited on a bare fiber core used for excitation of surface plasmon waves. To deposit a homogeneous layer, the fiber sample has to be continually rotated during deposition process, so the deposition chamber has to be equipped with an appropriate positioning device. This difficulty can be avoided when the layer is deposited in two steps without the rotation during the deposition (double-sided deposition). The technique is simpler, but in this case, the layer is not at and a radial thickness gradient is imposed. Consequently, the sensor starts to be sensitive to polarization of excitation light beam. A theoretical model is used to explain the polarization properties of such a sensing configuration. The analysis is carried out in the frame of optics of layered media. Because the multimode optical fiber with large core diameter is assumed, the eccentricity of the outer metal layer boundary imposed by the thickness gradient is low and the contribution of skew rays in the layer is neglected. The effect of the layer thickness gradient on the performance of the sensor is studied using numerical simulations.

The paper reports results obtained from optical spectrophotometry complemented with data from FTIR, Raman scattering and XRD measurements to characterize hydrogenated silicon (Si:H) thin films deposited by PECVD deposition from silane – argon plasma diluted with hydrogen. The dispersive optical properties and microstructure have been determined as a function of the hydrogen dilution which has been found to result in an inhomogeneous growth during which the material evolves from amorphous Si:H to microcrystalline Si:H. Porosity originating from microvoids has been discovered and calculated using effective medium approximations. Bruggeman effective medium approximation (BEMA) has been used to calculate volume fractions of microvoids and amorphous and crystalline phase.

There are various optical methods for the measurement of the geometrical shape of objects. We calculate the measurement uncertainty for several “paradigm” methods, by means of the Cramér - Rao lower bound. Thus the parameters, on which the measurement uncertainty depends, can be found. Substantial features of individual optical measurement methods (geometrical arrangement, optically smooth or rough surface, used light, dominant source of noise) of various measurement methods are compared and their influence on the measurement uncertainty is discussed.

Precise evaluation of intracellular cholesterol distribution is crucial for improving diagnostics of diseased states associated with cholesterol alteration. Time-resolved fluorescence techniques are tested for non-invasive investigation of cholesterol in living cells. Fluorescent probe NBD attached to cholesterol was employed to evaluate cholesterol distribution in peripheral blood mononuclear cells (PBMC) isolated from the human blood. Fluorescence Lifetime Imaging Microscopy (FLIM) was successfully applied to simultaneously monitor the spatial distribution and the timeresolved characteristics of the NBD-cholesterol fluorescence in PBMC. Gathered data are the first step in the development of a new perspective non-invasive diagnostic method for evaluation of cholesterol modifications in diseases associated with disorders of lipid metabolism.

We report on Raman spectroscopy measurements - separated by a given time intervals - for the selected yeast strains (biofilm positive and biofilm negative) on colonies grown directly on the Petri dishes or on the well-plate. Chemometric principal component analysis of these spectra sets generated clusters of data points, from which the reproducibility of the measurement could be analysed. Consequently, these resulted in clusters coinciding well with the biofilm positive and biofilm negative strains measurement of a particular sample dish, suggesting good reproducibility of our measurement procedure, even when the samples were prepared and measured days up to months apart. This suggests the potential of Raman spectroscopy in routine clinical diagnostic.

In this paper we study signal amplitude in Chirp-modulated Chirped Laser Dispersion Spectroscopy (CM-CLaDS). CLaDS is a laser-based spectroscopic technique for molecular sensing that uses heterodyne detection to measure optical dispersion caused by molecular transitions. With baseline-free nature and high-immunity to optical power fluctuations CLaDS is well suited to long distance remote, open-path monitoring and stand-off chemical detection. In this work we analyze CM-CLaDS performance. We show that for certain conditions using proper modulation waveform can provide increase in the signal amplitude with respect to previously presented configurations.

In this paper we present results of an implementation of thin two-dimensional (2D) photonic crystal (PhC) patterned in thin polydimethylsiloxane (PDMS) membranes on the light emitting diode (LED) surface. PDMS membranes were patterned by using the interference lithography in combination with imprinting technique. 2D PhC surface relief structures of period 580 nm were patterned in thin PDMS membranes with depth up to 150 nm. Patterned PDMS membranes placed on different optoelectronic device surface could modify the final optical properties.

This work presents an algebraic analysis and computer simulations of imaging properties of a refractive tunable-focus fluidic lens with two continuously variable radii of curvature. Such lenses make possible to change aberration properties. It is shown that such a tunable-focus lens makes possible to correct simultaneously its spherical aberration and coma, which is not possible with the conventional fix-focus lens. Formulas are derived for the calculation of paraxial parameters and Seidel aberration coefficients of the lens. Imaging properties are demonstrated on several examples.

The paper shows that the localization of a given light polarization state singularity of the optical field is strictly related to the elliptical analyzer properties. There are at least four reasons for such an approach: 1) there is an infinite number of light polarizations state representations; 2) the light polarization state cannot be measured directly; 3) non-measurable polarization state distribution of a light wave can be transformed into a measurable one using an elliptical analyzer; 4) the analyzer’s properties strictly determine the light polarization state representation. As a consequence, in my opinion, one cannot consider the properties of light polarization state singularities regardless of the analyzer’s polarization properties.

A new high sensitivity polarimeter has been established based on a fast change of the geometrical phase caused by a small change of an examined medium birefringence. In this setup sensitivity and measurement range can be controlled. The obtained sensitivity amounts up to 800 with regard to classical polariscopes. The proposed setup enables carrying out real time measurements. Stability and measurements resolution have been examined. Numerical simulations and measurements were performed.

To show flames in the visible and low infrared regions of radiation in the wavelength range from 400 nm to 2000 nm a design of optical systems technical borescope is presented. The proposed glass and technical parameters of the optical system correspond to the diameters of the lens elements and their distance of the borescope for VIS only. The correction lengths and distances of images are approximately the same and also correspond to the mechanical construction of the existing borescope for visible light. To record images in the wavelength range from 800 nm to 1000 nm it is possible to use the classic black-and-white cameras, e.g. OSCAR OS-458. Recording wavelengths in the range of 900 nm to 1700 nm allows, for example, InGaAs camera Bobcat 1.7-320.

In this work we focus on the application of the two dimensional photonic crystal (2D PhC) embedded in the surface of Al_0.295Ga_0.705As/GaAs multi-quantum well light emitting diode (LED) to enable improvement of the light extraction from the LEDs. The 2D PhC structures described in this contribution were fabricated by the E-Beam Direct Write (EBDW) Lithography and consist of pillars with the period of 700 nm. In this paper a new approach is presented to measure the PhC-LEDs based on evaluating light-current characteristics from Near Surface Light Emission Image (NSLEI) measurements in comparison with standard light-current characteristics measured by integrating sphere. The measured LED emission intensity increased by 20-30% when PhC was patterned on the top of LED structure in comparison with the reference LED without PhC. In addition, it was found that the measured light extraction intensity is higher in the case of NSLEI measurements. This originates in the ability that mostly the light intensity emitted from the LED surface is measured while the edge emission effect is suppressed.