The spatial solitons can create reversible or irreversible single-mode waveguides in the propagating materials. The important features are the 3D orientation and graded index profile matched to the laser fundamental mode. Bright spatial solitans are theoretically demonstrated and experimentally observed in the propagation of laser beams in widely available photorefiactive crystals such as Bi₁₂ (BSO) and LiNbO₃ (LN). We show the first observation of waveguiding by screening-photovoltaic bright solitons in LN and the low absorption and dispersion of the corresponding light produced waveguides (with femtosecond laser pulses). Applications in high coupling efficiency, adaptive optical interconnections and photonic crystal production are possible.

Based on crystal optics, Conoscopy is a unique implementation of polarized light interference process,. In the basic interference set-up a light beam is projected onto a diffusive object. The beam creates a light point on a target, which via reflection disperses the light in all directions. A complete solid angle of the diffused light is analyzed.. The measurement process corresponds to the retrieval of a distance of the light point from a fmed reference plane. Three dimensional measurement systems based on Conoscopic Holography are steadily gaining ground against conventional techniques. Conoscopic system have evolved from an exotic solution to the fist choice for all measurement problems not covered by triangulation techniques. Currently, they can be utilized on many applications such as quality control measurements, digitizing, reverse engineering and in-process inspection. A review of Conoscopic Holography principle will be presented in the first part of the paper. The exclusivity of Conoscopic Holography and its distinction from commonly used techniques will be reviewed.

We have developed a holographic optical tweezers system based on diffractive optical elements (DOES) implemented on a liquid crystal spatial light modulator (LC-SLM) able to generate fine positioned traps on the sample. Our own algorithms and code allows to calculate phase DOES that can transform a single laser beam into an array of independent traps, each with individually specified characteristics, arranged in arbitrary three-dimensional (3D) geometrical configurations. Different DOEs can be dynamically projected to the SLM in order to achieve a rearrangement of the configuration of the trapping spots. Silica or latex micro-beads are trapped in different configurations of spots to demonstrate the fine control capability on each trap. Our setup is built on a standard video microscope coupled with a laser source, a spatial light modulator and a three axis nano-positioning system. It allows to obtain 3D multi-trapping and a fine calibration for the positioning of the traps.

The features of e m inhomogeneous polarized field, which concern an angular momentum, are considered. It is shown that the e-m field produced by differently polarized optical beams may carry orbital angular momentum. Such angular momentum arises in field area with the point of circular polarization (C -point). Superposition of relatively simple orthogonally polarized beams is considered. Experimental results of particles capturing by such focused beam are presented. On the other hand, in the vicinity of s -contour (field line with linear polarization) spin angular momentum vanishes. At the same time such angular momentum appears when superposition of beams with different wave-length is considered.

In this work we present a numerical evaluation of the forces in an optical tweezers system, for metallic nanoparticles in the Rayleigh regime. Initially a Gaussian beam is described in the scalar approximation, and the forces it can apply on Rayleigh dielectric and metallic particles are computed within the point-dipole approach. The method is then extended to dielectric and metallic Rayleigh particles in a Laguerre-Gaussian beam, i.e. a higher order beam that is increasingly used for optical trapping experiments. We discuss the limits of the approximation for the beam intensity by comparing the numerical results with the experimental measurements that can be found in literature.

Interrelation of the fine structure of the vector field and its averaged polarization characteristics is considered. It is shown that space averaged Stokes parameters are defined by dispersion of the phase difference in its saddle points. The dispersion of phase difference and dimension of areas with considerable polarization changes are defied by the averaged space between the nearest adjacent component vortices of the same sign. The results of computer simulation and experimental investigation are presented. Good correlation between these results is observed.

In this paper we discuss and demonstrate the trapping and manipulating the particles by three types of single traps (Gaussian trap, vortex trap and "vortex less" trap), which are formed by one optical device. Experimental results are presented.

The actual growth of high-technologies and future applications in micro- and nano-manufacturing have raised the need for low cost / high performance micro-positioners. Photonic packaging, optical device testing, MEMS positioning/alignment, fiber alignment, micromachining, micro-manipulation, semiconductor handling systems, microsurgery are some examples of applications, from which the most are in the optical field. Very often, micro-positioning systems with micron or submicron resolution m needed to be run open loop, without feedback position sensors. Such devices are achievable with strain actuators like piezoelectric, magnetostrictive or electrostrictive ones. Two kinds of actuators could be used, with continuous motion or with discrete motion. The first could reach all the points from a space but request real time control. The second could reach only a finite number of points in space, but the command is binary, easy to implement. The working space for discrete actuators can be reached using a lot of actuators, series connected. The paper presents a piezoelectric actuator with 3 DOF, that could be used for micro-positioning. The investigated actuator is a scale model, for checking the principle and the models.

A strongly focused laser beam through an objective microscope with high NA allows the trapping of dielectric particles with micrometric sizes. The trapping force is proportional to the power of the laser, the relative refractive index (the ratio between the refractive index of the particle and the refractive index of the medium surrounding it) and the trapping geometry (shape of the laser beam, shape of the particle, transmission and reflection coefficients). Numerical models to evaluate the trapping force can be developed for simple geometrical shapes of the trapped particle. For particles with complicated shapes the trapping force should be measured experimentally. The goal of this paper is to evaluate a measurement method based on the equilibrium between the drag force in a fluid with known viscosity and the transversal trapping force. A particle with a known size is fist trapped in a cell filled with water. After stable trapping, the cell is shifted with controlled velocities using piezoelectric actuators. If the velocity exceeds a certain threshold, the particle escapes from the trap. This threshold allows to determine the trapping force. Experimental results obtained with high and low index particles are presented and discussed.

Relaxation of pulsed photocurrents under optical bias is studied in amorphous films of glassy alloys As₂Se₃:Sn_x (x=0 to 3.5 at. %) by the time-of-flight technique and steepness band-to-band light illumination. In frame of multiple-trapping model it is shown that by adding tin to the glass former As₂Se₃, the hole drift mobility is strongly increased and hamper the recombination. The kinetics of the long-term photocurrent decay can be described by stretched exponential hction. The dispersion parameter a, which can be deduced from the time dependence of the photocurrent I_ph(t) -infinity- exp[-(τ/τ)^α] and, is about 0.47 for undoped samples, and 0.35 for tin-containing samples. The obtained results indicate the variation in occupation of deep localized centers. For the investigated samples, the width of distribution of the deep traps is approximately kT/α~50-70 meV.

We present a discrete model for the motion of a beam of classical particles propagating across a rectangular lattice. These particles are represented by their classical probabilities to be found in different cells of the lattice. We consider two kinds of interactions between the particles and the intmvening substance. In free space the particles slightly deviate fiom a pure forward movement. When they collide with an obstacle, they are elastically reflected. Rather surprisingly, our simple model predicts a wavy character for the probability profile of this non-quantum particle beam. We observe maxima and minima under very general conditions. Specifically, particles experience difgaction around obstacles. These fiinges are not the result of interference of certain waves, but rather of the particle reflections on obstacles, as well as of the deviations from a pure advancing movement. We study the influence of the dimensions of the source, of the obstacles and of the interaction between the beam and the screens.

Here we study the temporal evolution of a magnetemechanical, inverted spherical pendulum. The oscillator is a rigid, stainless steel, hollow needle. The needle has one end fixed in a spherical-like articulation, while the other extremity has no mechanical contact. The oscillation is driven by a longitudinal, periodically magnetic field added to a constant value of a static field. A video camera takes simultaneously the optical images of the projections of the oscillating needle along two mutually normal directions. The pairs of temporal sequences are analyzed in the real space, phase space and Fourier space. Among all the external parameter that can be usually varied, like the strength of the static magnetic field, the amplitude and the frequency of the driving magnetic field, or the momentum of inertia of the oscillating body, of a crucial importance seems to be the magnetc-mechanical feed-back of the oscillating system.

In this paper the results of complex study of optic-physical characteristics of dacron films with different ordering degrees of their supermolecular structures are presented. The estimation of polymer macromolecules orientation influence on its light scattering matrix (LSM) is given.

The outcomes of research of chaos in the field of optical radiation scattered by nematic liquid crystal during phase transition fluid - liquid crystal are represented in this paper. It was shown that the Lyapunov's maximal index of time dependence of intensity is more than zero, it means that chaos exists in the system. Moreover, the degree of randomicity increases with the growth of plate thickness of liquid crystal.

Photoluminescent porous silicon films were prepared and their microstructure investigations showed a double scale porosity, the walls of the micropores being formed by a nanowires network. The temperature dependence of both the electrical transport and photoluminescence processes in these films, as well as the spectral distribution of the photoluminescence, were measured. The results prove a clear correlation between the two processes. A simple quantum confiiement model was proposed for the calculation of the electronic energy in nanocrystalline silicon. The model explains the observed experimental behavior of both the electrical transport and the photoluminescence and justifies their correlation. Its quantitative predictions are in excellent agreement with the microstructure investigations. The model can be applied to a wide class of materials.

The UMTS Bearer Independent Core Network program introduced the 3^rd Generation Partnership Program Release 4 BICN architecture into the legacy UMTS TDM-switched network. BICN is the application of calI server archltecture for voice and circuit switched data, enabling the provisioning of traditional circuit-switched services using a packet-switched transport network. Today's business climate has made it essential for service providers to develop a comprehensive networking strategy that means introduction of RCBICN networks. The R4-BICN solution to the evolution of the Core Network in UMTS will enable operators to significantly reduce the capital and operational costs of delivering both traditional voice sewices and new multimedia services. To build the optical backbone, which can support the third generation (3G) packetized infrastructure, the operators could choose a fibre connection, or they could retain the benefits of a wireless connectivity by using a FSO - Free Space Optical link, the only wireless technology available that is capable of achieving data rates up to 2.4 Gbit/s. FSO offers viable alternatives for both core transmission networks and for replacing microwaves links in NodeB - RNC access networks. The paper and presentation aim to demonstrate the manner in which FSO products and networks are employed into R4-BICN design solutions.

Among the problems that are solved successfully within the concept of singular optical, one must emphasize: the techniques for generation of isolated singularities (also called wave front dislocations, vortices, or amplitude zeroes) in the field [ 1,2]; the topology of the network of amplitude zeroes for the speckle field at the model (qualitative) level [3-5]; the optical techniques for diagnostics of singularities for the field [6,7]; the use of singularities for the field in solving application problems, such as manipulating small particles (i.e. optical traps and tweezers) [8,9]. The interest in the study of local amplitude and phase structures of the field in the vicinity of singularities, not only for monochromatic radiation field but also for polychromatic fields, has considerably increased recently [3, 10-12]. Papers [13, 14] devoted to the study of the scenario and mechanisms of nucleation and evolution of singularities in the vicinity of caustics have appeared.

The principle of optical actuation of arrays of micromechanical cantilevers has widespread applications in optical signal processing. The paper demonstrates that, depending on the configuration and operating mode of the micromechanical cantilever array, optical actuation can be used to design broadband detectors, optical computing units for addition, integration or differentiation of optical signals, to implement devices that can measure simultaneously the wavelength and the optical power of a laser source with constant efficiency from UV to FIR, or to determine the amplitude and phase profile of an incident light beam. Moreover, an array of optically actuated biased cantilevers can work as an optical data storage device that encodes arrays of optical pixels (images) with a predetermined number of gray levels.

Temporally restricted objects may be superresolved using the moving of two masks such as pinholes or gratings. The first one performs the encoding process of the input object and the second one is responsible for the decoding operation. This approach is efficient for exceeding the resolving capability beyond Abbes's limit of resolution but several problems exist in the system matching. We propose superresolution techniques based on the use of tilted wave illumination. In a first approach, the second grating used for the decoding operation is removed and substituted by a digital post-processing stage. In a second approach, the two masks are replaced by the use of a Vertical Cavity Surface Emitting Lasers (VCSEL) array. This VCSEL array provides a set of tilted waves at different angles and incoherent one to each other. By means of an interferometric recording process we ensure the transmission of several spatial frequency bands of the object's spectrum in parallel. After a reconstruction process, the resolution of any optical system can approach the natural λ/2 resolution limit. Unlike other interferometric superresolution techniques for this approach the exact reconstruction of the input object is obtained. Moreover, any desired synthetic coherent transfer function can be realized at ultra fast rates changing the electrical driving of the VCSEL array.

Laser interferometer displacement measuring transducers have a well-defined traceability route to the definition of the meter. The laser interferometer is de-facto length scale for applications in micro and nano technologies. However their physical unit -half lambda is too large for nanometric resolution. Fringe interpolation-usual technique to improve the resolution-lack of reproducibility could be avoided using the principles of absolute distance measurement. Absolute distance refers to the use of interferometric techniques for determining the position of an object without the necessity of measuring continuous displacements between points. The interference pattern as produced by the interference of two point-like coherent sources is fitted to a geometric model so as to determine the longitudinal location of the target by minimizing least square errors. The longitudinal coordinate of the target was measured with accuracy better than 1 nm, for a target position range of 0.4μm.

The feasibilities of using interferometric techques in the diagnostics of phase singularities and in the study of a phase structure of the field in their vicinity are demonstrated. The peculiar evolution of singularities into caustics produced by phase elements of singularity-generating objects of spherical and cylindrical shape are studied.

The results of experimental research of Muler's matrices reflecting metallized surfaces with a periodic structure, in the capacity of which diffraction grates are used, are presented in the paper. The analysis of the power distribution of radiation of the different types and of azimuth of the polarization relative to the horizontal reference plane depending on the reflection angle α and orientation angle of grating grooves θ. Functional regularities of the angles' α and θ influence on the polarization characteristics of the reflected radiation of diffraction grate are determined. The role of correlation of the quantity of diffusion and mirror components of the reflected radiation on its polarization characteristics is shown.

The correlation structure of 2-D Stokes vector parameters of physiologically normal and pathologicaly changed biotissues is investigated. The totality of diagnostically urgent interconnections between biotissue physiological state and statistical moments of 2-D Stokes vector parameters is found.

The interconnection between geometry of biotissue structure with their polarization properties has been studied. It has been shown that for physiologically normal biotissues polarization properties of radiation scattered on architectonic nets formed by protein fibrils possess the fractal character. Pathological changes of biotissues architectonics are accompanied with the transformation of self-similar structure of Mueller-matrix images into stochastic and statistic ones.

A novel three-dimensional model has been proposed for simulating plume behavior and 'micron-sized particles' movement and interaction. It describes particles expansion in vacuum or into an environmental gas and particles interaction with various obstacles. The model simulates 'standard' Pulsed Laser Deposition (PLD) system behavior, but also some droplet reduction techniques used in PLD (e.g. shadow mask technique) having good results in plasma expansion for the first several centimeters from target. The carried out simulations have shown that in the PLD with plasma reflection (PLDPR) the influence of mass and particle's surface area on the droplets trajectory is significant. By increasing of the particle mass or by decreasing particle's surface, the probability of the particle to be driven into the deposition area by plume fine particles is considerably decreasing.

Rigorous Coupled-Wave Analysis for 2D gratings is reviewed. The main features of RCWA such as the Fourier expansion of the dielectric function in the grating area, solving the Maxwell equation inside the grating, the eigenvalue problem and the matching of the tangential fields at the interfaces are described. Key improvements of the theory, that allows the reduction of the work time by orders of magnitude, such as the reduction of the sue of the matrix for the eigenvalue problem are stressed. The computer code written based on this theory passed consistency tests and was checked against other computer codes.

In the present paper we have focus our study on relaxation of photodarkening in α-As₂Se₃ doped with Sn and rare-earth (RE) ions (Dy³⁺, Pr³⁺, Ho³⁺, Sm³⁺, Nd³⁺, Er³⁺). The relaxation process of photodarkening is described by a stretched exponential function with the dispersion parameter 0<α2Se₃ glass was probed by a local probe like ¹¹⁹Sn Moessbauer spectroscopy, and in conjunction with Temperature Differential Scanning Calorimetry (TMDSC) some aspects of the molecular glass structure were elucidate. Recommendation concerning the stabilization of the glass structure by metal impurity against photostructural transformation have been suggested, and which are very important for chalcogenide glasses doped with rare-earth ions as perspective materials for fibre optics amplifiers operating at the 1.3 μm and 1.5 μm telecommunication windows.

The polarimetric method of information polarization selection, which is effective in phase-inhomogeneous layer (PIL) diagnostics in their images has been presented. The technique of BT's polarization visualization and SNR increasing of the image of BT's architectonics has been elaborated. The possibilities of polarization-correlation analyses of architectonics images of the BT have been studied.

Specific features of the formation of local and statistical polarization structures of laser radiation scattered in phase- inhomogeneous layers (PIL) of biological tissue (BT) were studied. The distribution of azimuth and eccentricity of boundary field polarization was found to correlate with the orientation-phase structure of multifractal PIL. A method of polarization phase reconstruction of BT architectonics was suggested.

Air pollution monitoring needs real-time measurement systems for low pollutant concentration levels. The authors have designed and manufactured an experimental integrated chemo-optical sensor on silicon containing a sol-gel layer, a silicon nitride waveguide and a silicon photodiode. This sensor was included in a measurement system, which has its own microcontroller for data acquisition and an autonomous power supply. The measured data are calculated and managed when the microcontroller is serially connected to the computer, dedicated software being performed. In this way, the "classical" laboratory equipment for air pollution measurements can be replaced by an autonomous real-time measurement system.

The perceptron is useful to be used in different forms and implemented into different technologies for could study of limits and development directions of neural networks in respectively technologies. In this paper the authors present, from theoretical point of view one model of perceptron with a single layer achieved with optoelectronic and optic devices. The showed perceptron has more advantage such as: its threshold can be modified, the type of inputs can be modified from excitatory to inhibitory and vice versa etc.

Between other sensing and identification technologies that of Surface Acoustic Waves, (SAW), is a unique sensing system. The principal advantage to most SAW systems is that they can use two or three SAW sensors and compare the measurements between them, providing a good accuracy. We have carried out the design of both piezoelectric substrate and interdigital transducers, (IDTs), and has tested them in a delay line mode operation. The measurement of changes in the surface waves characteristics were materialized by applying of a radio frequency electric field to the piezoelectric crystal by means of IDTs. The finger width of the IDTs was measured by high accuracy optical coherent method. The results are presented in the work. The potential development of microsensors as an array of four or five miniature sensors, sensitive to Werent chemicals may be used as mobile chemical detecting units carried by remote control vehicles to the site chemical contamination.

All fiber optic seismic sensors contain a mechanical system which determines the optics to encode somehow the ground motion when an earthquake occur. This system basically consists in an inertial mass fixed on an elastic element. The first condition for a proper earthquake detection is determined by the ability of the mechanical system to reproduce accurately enough the movement of the ground. In this paper we report some theoretical results concerning this problem, and especially the conditions which must be accomplished by the mechanical system in two usual frequency ranges (both far of its natural frequency). This is done by analitically solving the motion differential equation of the mechanical system for a simple forcing (which stands for the earthquake) and numerical simulation.

Poly (vinyl alcohol) [PVA] is a photo-induced cross-linking polymer, water-soluble, biocompatible, used in holography, nonlinear optics, as tissue engineering scaffolds and as polymer matrices for enzymes immobilization. PVA has been investigated for use as binder polymer in optical waveguides for sensor applications. The Y-shaped waveguides is composed of a buffer layer (lower refractive index) - SiO₂, a core layer (higher refractive index) - PVA doped for the refractive index and sensibility increasing and a cladding layer (lower refractive index) - an other polymer. The light propagation in doped PVA waveguides represents the sensing element of the sensor. The preliminary results suggest that doped PVA polymers are promising for optical (bio)chemical sensors; the processes used to make them, represent environmentally friendly technology.

We present preliminary experiments for an integrated optical sensor based on a Mach-Zehnder interferometer for biological applications. The sensor is sensitive to refractive index change produced by the presence of a biological species in the cladding of the optical waveguide. A "window" can be patterned in the upper cladding, so that the evanescent wave can be in direct contact with the environmental (the sensitive layer). We investigated as optical waveguides a new material, SU-8, a negative photoresist well known from the development of 3D micromachmed structures. We structured, by photolithographic techniques, rib and channel optical waveguides. We studied the influence of the silicon substrate on propagation losses and the possibility to use these losses for the selective attenuation of the higher order modes on the vertical direction. As biological materials we experimented collagen, which is a bio-polymer which can bind different enzymes or antibodies.

This paper presents novel ways of implementing waveguide components in photonic crystal slabs based on silicon-on- insulator (SOT). The integration platform we consider consists of hexagonal holes arranged in a triangular lattice ('hexagon-type' photonic crystal). The waveguides are made of one missing row of holes (Wl) with triangular air inclusions symmetrically added on each side of the waveguide. Size and position of these inclusions are tuning parameters for the band diagram and can be used for minimizing the distributed Bragg reflection (DBR) effect. The waveguides show single-mode behavior with reasanably high group velocity and large transmission window, inside the gap between H-like modes**. These waveguides, closely resembling conventional ridge waveguides, can be combined to form efficient bends and Y-junctions. The bends and Y-junctions include intermediate short waveguide sections at haif the bend angle playing the role of corner 'mirrors'. Qualitative design rules were obtained from 2D calculations based on effective index approximation.

In this paper we present one model for parameters used in EDFA (Erbium Doped Fiber Amplifier) in the case of high- power limit. We use for this model the absorption and emission cross-sections as a function of wavelength. In this model we use the fraction of Er³⁺ ions in the excited state as a function of wavelength for high-power limit. In addition, we present and compare these characteristics for different erbium-doped glasses in the case of EDFA. The results obtained here can be used to evaluate and to determine the characteristics for noise figure and for gain in the case of EDFA.

The operators of telecommunications have targeted their efforts towards realizing applications using broad band fiber optics systems in the access network. Thus, a new concept related to the implementation of fiber optic transmission systems, named FITL (Fiber In The Loop) has appeared. The fiber optic transmission systems have been extensively used for realizing the transport and intercommunication of the public telecommunication network, as well as for assuring the access to the telecommunication systems of the great corporations. Still, the segment of the residential users and small corporations did not benefit on large scale of this technology implementation. For the purpose of defining fiber optic applications, more types of architectures were conceived, like: bus, ring, star, tree. In the case of tree-like networks passive splitters (that's where the name of PON comes from -Passive Optical Network-), which reduce significantly the costs of the fiber optic access, by separating the costs of the optical electronic components. That's why the passive fiber optics architectures (PON represent a viable solution for realizing the access at the user's loop. The main types of fiber optics architectures included in this work are: FTTC (Fiber To The Curb); FTTB (Fiber To The Building); FTTH (Fiber To The Home).

In this paper, the performance of PSK (phase shift keying) homodyne system in the present of laser phase noise is calculated. It is shown that the phase noise leads to a significant performance degradation for coherent systems. The obtained results are shown graphcally.

In this paper the authors present, from theoretical point of view some logical gates (NOT, OR, AND), demultiplexer (DNIUX) and multiplexer (MUX) achieved with optical devices. The important advantages of the models are: the speed of the information transfer is high, the data transmission rates are high, the processing power is high. Another advantage is that the light signal processed and transmitted (in different applications) isn't converted in electronic signal and then reconverted in optical signal. The light signal remains all the time into optical domain.

In this paper the authors present, from theoretical point of view some logical circuits achieved with optical devices that work using a ternary logic. Those three levels are clearly distinct and the danger of confusion does not exist.

In terms of communication performance, optics (micro optics, integrated optics) has proved superiority to electronics. In this area, the diffractive optical elements (DOE) play a very important role using their shap to bend light (dieactive optics work by breaking up incoming waves of light into a large number of waves, which recombine to form completely new waves). There are several methods of analyzing and designing such devices and in each situation some goals are of interest: the accuracy of accomplished function, the dieaction efficiency, dimensions restrictions. In this paper we use Genetic Algorithms (GA) to optimize the performances of such diffkactive elements. The theoretical considerations are verified by simulations on computer for CGH used as fan-out interconnection hologram.

An optical transmission system is a method of transferring information in the shape of bits or symbols for the case of digital systems, and of analogue waves for the case of analogue systems, between fixed points located on a fiber optics cable. Today and in the near future there are numerous such transmission techniques available. The increase of demands for data transfer from phone subscribers can be met only by means of digital techniques applied in the local network, in addition to the use of digital telephone exchange and of the digital transmission systems in the trees network. In order to increase the quantity of information transferred through one fiber, optical multiplexing techniques have been conceived and tested. The optical multiplexing is additional to the electrical signal multiplexing. The requests for the access network will become more and more complex, a larger flexibility and a wider band being needed. For the purpose of complying with these requests, the coherent simultaneous or alternative transmission towards the optical amplifiers represents a factor of technical progress. The multiplexing with wave length division allows for more channels to be transported through the same fiber with different wave lengths, in one or both directions.

In this paper we compare different free space propagation algorithms based on fast Fourier transform (FFT). They are used to calculate 1D and 2D difiaction patterns in near field and far field as well. Four algorithms are considered: angular spectrum propagation, direct integral formulation, fractional Fourier transform using single FFT (S_FFT) and fractional Fourier transform using two FFT (D_FFT). We compare these algorithms and discuss their advantages and drawbacks for one and two-dimensional objects.

Although higher reliability is expected from submicron and nanotechnology so far only a few attempts have been made to apply reliability theory to submicron and nanodevices. The way to reliable nanotechnology is to identify relevant physical failure mechanisms and corresponding failure rates, determine reliability indices, and investigate reliability models down to nanoscale including quantum processes. Perhaps the most significant problem concerns the sensitivity of future IC generations face to various noise sources, and in patxularly face to energetic particles. This paper analyses some of the above problems. At the same time, we propose the implementation of a new soft error detecting technique based on time redundancy.

Based on the transmission spectra of Er³⁺-doped LiNb0₃ optical waveguides in this paper we report some experimental and theoretical results concerning the evaluation of some spectroscopic parameters which characterize the above mentioned waveguides. The absorption experimental spectra were used to determine the homogeneous absorption and emission cross sections, the oscillator strength of the absorption transition, the spontaneous emission probabilities, radiative lifetime and the excitation energy in three regions of the optical spectra: around 1550 nm, 980 nm and 550 nm, respectively. The obtained results can be used for the design of optical guided lasers, amplifiers and other optoelectronic devices.

In the small gain approximation and the unsaturated regime in this paper we report some original results concerning the evaluation of the Fano factor, statistical fluctuation and spontaneous emission factor which characterize the photon statistics on the number of excited modes, dopant concentration and power pumping in the single and double pass Er³⁺ - doped LiNbO, straight waveguide amplifiers pumped near 1484 nm using erfc, Gaussian and constant profile of the Er³⁺ ions in LiNbO, crystal. We demonstrated that for 50 mW input pump power the Poisson photon statistics are maintained in the above mentioned amplifiers for concentrations of the Er ions smaller than l0²⁶ m^-3 and also high gains and low noise figures are achievable. The obtained results can be used for the design of optoelectronic integrated circuits.

Presented in this paper are numerical algorithms necessary to determine the surface error by means of optical interferometry. These algorithms are based on digital processing of phase-modulated fringe patterns, and are using the discrete Fourier transform method.

A series RLC electric circuit with the metal-ferroelectric-semiconductor (MFS) heterwdructure playing the role of nonlinear capacity shows various nonlinear dynamics such as period doubling and Ruelle-Takens scenarios of evolution to chaos. Experimental investigations and preliminary theoretical analysis on the dynamics of this structure are considered. We mainly focus on a period-doubhng bifurcation evolution to chaos induced by the change in the amplitude of a sinusoidal driving with given frequency and by the change in the frequency of driving signal of fixed amplitude. In this paper we concentrate on an integrated image of these phenomena as reflected in 3D graphs of spectral analysis. A theoretical model of this MFS structure as nonlinear element of an electrical circuit based on a system of two coupled nonlinear Duffing oscillators is proposed. Numerical simulations for electrical variables in the circuit were performed both by specific methods of nonlinear investigations and by 3D plots representing Fourier power spectra as function of the frequency and the amplitude of the forcing as control parameters. The dynamics of the theoretical model are in reasonable agreement with the experimental results.

In the frame of paraxial approximation, we consider the case of free atoms interacting with an Lagtierre-Gaussian beam. Using Power-Zienaii-Wooley scheme, we calculate the interaction Hamiltonian in the quadrupole approximation and including center of mass motion of the atomic system. The expression of the center of mass transition probability is derived in analytic form. The influence of the beam and atomic system parameters on the center of mass transition probability are discussed.

The paper presents the basic concepts of the optical correlators. In our knowledge, it is the first systematic presentation of the applications of optical correlators. The main three types of optical correlators: the optical correlator in incoherent light, the optical correlator in coherent light (VanderLugt) and the joint transform correlator are presented. The optical correlators are very powerll systems used for image recognition, that perform a correlation between a bidimensional function which represents a Scene that must be analyzed and another bidimensional function that contains information about the reference function. This correlation is optically realized by a Fourier transform between the two functions. The optical Correlators have found a lot of applications for image recognition and target detection in various fields, such as the military field, robotics, medical field, industry a.s.o. Among the various applications of the optical correlators we can mention: digital fingerprints identification, credit card security, antique scripts recognition, determination of the cosmic ships and satellites behavior, amelioration of cancer tests precision, quality control etc.

The design and fabrication of two binary phase diffractive optical elements is presented. We use iterative Fourier transform algorithms and a geometrical optics approach to design the diffractive elements. The outgoing beam shapes of the designed elements are compared by computer simulations. The advantages and disadvantages of each design are presented.