Avalanche photodiodes specifically designed for single photon counting semiconductor avalanche structures have been developed on the basis of various materials: Si, Ge, GaP, GaAs and InGaAs at the Czech Technical University in Prague during the last 20 years. They have been tailored for numerous applications. Recently, there is a strong demand for the photon counting detector in a form of an array; even small arrays 10×1 or 3×3 are of great importance for users. Although the photon counting array can be manufactured, there exists a serious limitation for its performance: the optical cross-talk between individual detecting cells. This cross-talk is caused by the optical emission of the avalanche photon counting structure which accompanies the avalanche multiplication process. We have studied in detail the optical emission of the avalanche photon counting structure in the silicon shallow junction type photodiode. The timing properties, radiation pattern and spectral distribution of the emitted light have been measured for various detection structures and their different operating conditions. The ultimate limit for the cross-talk has been determined and the methods for its limitation have been proposed.

We present a laser system based on a tunable Titanium:Sapphire (Ti:Sa) laser optimized for maximum efficiency of the optical pumping process of Rb atoms. The system represents the first and crucial part of the HpG (hyperpolarized gasses) production process. It was designed for laboratory purposes where the expensive and complicated Ti:Sa laser is justified because of its variability. narrow linewidth and easy tuning of the wavelength. The system consists of a modified commercial Ti:Sa laser pumped by a Nd:YAG laser, beam-forming and polarizing optics, and heated interaction cell attached to a vacuum manifold and gas containers placed in homogeneous magnetic field generated by a set of Helmholz coils.

A 640×512 pixel, long-wavelength cutoff, narrow-band (Δλ/λ~10%) quantum well infrared photodetector (QWIP) focal plane array (FPA), a four-band QWIP FPA in the 4-15 μm spectral region, and a broad-band (Δλ/λ~42%) QWIP FPA having a 1 5.4 μm cutoff have been demonstrated. In this paper, we discuss the electrical and optical characterization of these FPAs. and their performance. In addition, we discuss the development of a very sensitive (NEDT-10.6 mK) 640×512 pixel thermal imaging camera having a 9 μm cutoff.

Recent theoretical and experimental results in nonlinear optics of semiconductor nanostructures and intracavity nonlinear mixing of laser modes are reviewed. A comparative analysis of the implemented and newly suggested schemes for the difference- and sum-frequency, second-harmonic, and parametric generation is presented. In particular, the problems of nonlinear photonic crystals, true- and quasi-phase-matching designs, and the use of the longitudinal, transverse, and 2D (metal or dielectric) gratings in the surface-emitting semiconductor devices are discussed. The most promising schemes of nonlinear-mixing lasers, both quantum cascade (intersubband) and diode-type (interband), are described. Finally, numerous applications of nonlinear-mixing lasers and open issues in physics and technology posed by the problem are given.

A metal resistor bolometer for the detection of x-ray emission from laser plasma has been designed and fabricated. The bolometer is placed on a thin polymeric foil with the use of thin film technology. The foil is suspended on a GaAs substrate. The Au/Pt/Ti thin film resistor of 2000 Ω resistance and 0.19 %/K temperature coefficient is used for sensing temperature. A detection head equipped with the bolometer and accompanying read-out electronics has been fabricated and used in a plasma experiment.

The work is oriented to development of methods for the absolute laser interferometry. The difference between absolute and incremental measurement is described. In the field of the absolute laser interferometry, the linewidth of the laser source limits the maximum measurable distance and the interval of mode-hop free tuning range determines the resolution of the distance measurement. Then, is work is oriented to selection of the primary laser source for the absolute laser interferometry and to determination of its characteristics. Methods of measurements and calculation of basic parameters of the tunable lasers are well described. The method of the absolute laser interferometry with wavelength-scanning interferometry technique improved by an amplitude division of interference fringe was designed and it is described. The Fabry-Perot etalon was designed and it is used to measure the tuning range ofthe laser source.

At the present time fiber-optics and optical communication are in rapid progress. Modern technologies such as DWDM (Dense Wavelength Division Multiplex) need precise stability of laser frequencies. According to this fact, requirements of new etalons of optical frequencies in the telecommunication band is rapidly growing. Lasers working in near infrared telecommunication band (1500-1600 nm) can be stabilized to ¹²C₂H₂ or ¹³C₂H₂ (acetylene) gas absorption lines. The acetylene gas absorption has been widely studied and accepted by international bodies of standardization as a primary wavelength reference in the near infrared band around 1550nm. Our aim was to design and develop a compact fibre optics laser system generating coherent light in near-JR band with high frequency stability (at least 1.10^-8). This system should become a base for realization of a primary frequency standard for optical communications in the Czech Republic. Such an etalon will be needed for calibration of wavelength-meters and spectral analysers for DWDM communication systems. We are co-operating with CMI (Czech Metrology Institute) on this project. We present stabilized laser system based on a single frequency DFB (Distributed Feedback) laser diode with a narrow spectral profile. The laser is pre-stabilized by means of the FM-spectroscopy on a passive resonator. Thanks to a fast feed-back loop we are able to improve spectral characteristics of the laser. The laser frequency is locked by a relatively slow second feed-back loop on an absorption line of acetylene vapour which is sealed in a cell under the optimised pressure.

We examine here various types of Si:Er-based light emitting diodes (LEDs) grown with an original Sublimation MBE technique and radiating at 1.54 microns under p-n junction breakdown. It is concluded that p-n junction breakdown mechanism is the most effective way to control Er-related EL in reverse biased LEDs. Maximal Er-related EL intensity and excitation efficiency at room temperature are achieved in LEDs operating under mixed breakdown regime where tunnel and avalanche breakdown mechanisms present equally. The effective excitation cross section and the lifetime of excited Er³⁺, the internal quantum efficiency and the thickness of the "dark" region are measured for SMBE grown LEDs radiating under mixed p-n junction breakdown.

The distance changes between structural elements inside a building (e.g. walls, pillars, stairs, etc.) ought to be monitored, especially in seismic-prone areas, in order to assess its stability. Fibre Bragg grating (FBG) sensors are now the most interesting choice for this purpose, since several gratings can be included in the fibre, resulting in a quasi-distributed sensor, which can be illuminated using a single light source and interrogated simply by a single optical spectrum analyzer (USA), using wavelength multiplexing. The paper deals with such a sensor, which was installed for monitoring the distance changes in a construction joint between two building blocks inside the University "Politehnica" of Bucharest. Since this city is placed in a seismic-prone area, we use a fast scanning USA, so that the dynamic behavior of the monitored construction joint is expected to be captured during future earthquakes. Slow drifts of the construction joint width will be also monitored. The paper describes the sensor structure and working principle, the experimental tests and main parameters evaluation. The reported sensor is temperature compensated. It has an estimated distance resolution better or equal to 10 μm, and a linearity of +0.2%...-0.35% for displacements up to 0.55 mm. Simulated dynamic tests are also reported.

Besides the ongoing rapid development of processing power of computers new standardised interfaces are emerging. Thus, future measuring software will be able to process information of the quality of a measuring operation. This exceeds the current state-of-the-art. The originality of this research lies with the proposal of a novel method for computing a quality factor for each measuring point. The method is applicable for optical imaging sensors. However, similar regimes may be applied for other types of sensors. This paper presents a general methodology for computing a quality factor for focusing. Thereby different criteria such as unimodality, accuracy, reproducibility, definition range, general applicability and robustness are covered. The application of the proposed quality factor enables a more profound evaluation of a focusing process than the pure specification of the uncertainty of the focus position does. Within a closed quality loop it enables a higher level of control of the measuring process resulting in a significantly decreased measuring uncertainty and an increased robustness. Thereby the closed quality loop comprises the CAD process, inspection planning, measuring operations and the comparison between CAD data and measured geometry. The paper closes with some experimental results showing the soundness of the proposed method.

Charged centers exist in the phosphor layer of common alternating current thin film electroluminescent devices. In this article, the electron scattering process by these centers is studied through phase shift analysis. The scattering rates in different cases are gained and compared with other important scattering processes. The electron transport process is simulated by means of the Monte Carlo method. Quantitative results about the influence of charged centers on electron kinetic energy are gained.

Measurement of liquid level in tanks is an important function in many industrial processes. Optical-fiber sensors have high sensitivity and its non-electrical nature and immunity to electromagnetic interference make them safe for applications in explosive environments and oil tanks. In this work we present a liquid-level sensor system based on laser feedback interferometry. Considering that the index of refraction of liquid hydrocarbons is in the range from 1.45 to 1.55, and the air reflectivity varies between 3.37% and 4.65%, we could demonstrate that it is possible to measure displacements of even 8.00 meters with a resolution of a half of the wavelength of the signal emitted. Thus, we can obtain a sensor with a high resolution in a broad range of measurements based in this technique. The effects of undesired internal reflections or backscattering due to the oil vapor could be also taken into account.

The Laser Induced Fluorescence is a well-known and established analytical technique. We are reporting on the research and development of the remote sensing technique for water pollution of the organic pollutants dissolved in the water or flowing on the water level. The recent development in diode pumped compact micro lasers, solid state photon counters and fast timing electronics opens quite new application possibilities. We are relying on the diode pumped Nd:YAG microlaser, passively Q-switched and frequency doubled. It provides pulse energy exceeding 100 nJ in 600 ps long pulses at 532 nm with the repetition rate of 10 kHz within a compact, small and low power package. The fluorescence signal is detected by the customized silicon photon counting detector. The compact time-to-digital converter with 20 ps timing resolution and a personal computer interface has been constructed for the device. The small receiving optics apertures together with advanced time gating of the detected signal permits to operate in an outdoor environment in daylight background conditions with acceptable signal to noise ratio. The first measurement results. the capabilities of the technique in the environmental monitoring along with the device construction will be presented.

Mechanical construction of the fiber absolute laser interferometer is presented in this article. The unique system is based on the VCSEL laser diode (wavelength 760 nm) and uses single-mode fibers. Optical setup consists of new E2000/APC connectors and fiber optic isolator to minimize the back-reflection to the laser diode. The whole system is placed on the massive duralumin plate to minimize mechanical influences. Base plate is placed on the rack with control electronics to create compact unit. The whole system is developed for industrial applications.

We report about theoretical results and experiments, which led to the demonstration of optical bistability on the specially modified laser diode (LD) created on the double heterostructure Ga_1-xAl/GaAs with saturable absorbtion section. To prove the bistability, the time method for bistability impulse verification (BIV) by bistable laser diode samples of realized BLD were determined. Also the mathematic model of the W-A characteristic was derived, used for the simulation of the characteristic for the realized BLD. Element values of the electrical equivalent circuit of the BLD for small hanges of signal were calculated for selected operating points of the simulated W-A characteristics. The dependency of bistability on the temperature is monitored by measuring the BLD W-A characteristic.

Titanium- carbonitride thin films were grown at room temperature using a hybrid deposition arrangement combining DC magnetron sputtering and KrF pulsed laser deposition (MSPLD). Carbon and titanium were simultaneously deposited on the same Si substrate, dimensions of 3 cm × 3 cm. Films were fabricated in argon- nitrogen atmosphere of 1 Pa - 5 Pa, for laser fluence of 15 Jcm^-2 and magnetron power of 150 W. Film properties were modified by RF discharge held between the target and substrate. Film crystallinity was studied by XRD and the composition depth profile of TiCN layers by glow discharge optical emission spectroscopy (GDOES).

At present non-contact photonic systems based on laser profiling are applied in industry and transportation. Often they have restrictions in overall dimensions. These restrictions result in the captured image will have the distortions. Linear distortions caused by rotation of camera relative to object are excluded by Eller's transformations. Non-linear distortions caused by small distance between camera and object and optic aberrations may be decreased by calibration. To provide required accuracy it is necessary to find correspondence between image and real coordinates using optical calibration. Original method and equipment for the measuring system calibration have been developed. Dependence between image and real coordinates may be approximated by polynomial function. Special equipment includes the precision mechanical array allowing to place needed vertical and horizontal rail coordinates, platform for camera and laser mounting, test monitor and computer to calibrate was developed.

The bi-directional mode expansion and propagation method (BEP) is known as an accurate and efficient method for modelling field distribution in waveguide structures with strong back-reflections like waveguide gratings and photonic crystals. Recently, a two-step algorithm for eigenmode calculation based on the expansion into the modes of an empty metallic waveguide has been proposed by P. Bienstman. Proper truncation rules possessing good convergence of the expansion method for both TE and TM modes have also been recently published by Sauvan et al. We have combined these approaches in the development of a simple version of the two-dimensional (2-D) BEP method that makes use of the expansion into the eigenmodes of a parallel-plate waveguide. Results of model calculations are compared with several well-established methods.

The scattering of electromagnetic waves by a slab whose refractive index is changing along its boundary planes is exactly calculated in a closed analytical form. The key feature of the calculation is the introduction of a new set of modes. As an specific example the reflected and transmitted field generated by the interaction of an incoming plane wave by a N-layered medium whose layers are perpendicular to the boundary planes of a slab are given.

Negative refractive optics is considered to bring forth new optical functions that have been out of reach for classical optics. Since materials with a negative refractive index are difficult to find or fabricate, the photonic crystal (PhC) is currently deemed the most potential candidate bringing negative refraction into the optical regime without requiring the material's refractive index itself being negative. In this work, we first look at the optical properties of a slab lens and then analyze a common PhC structure with negative refractive behavior with respect to optical transmission, dispersion and wavefront aberration. By taking a PhC slab we determine the geometrical and physical conditions that allow it to provide imaging similar to a lens.

We present here last results on development and research of Si:Er-based light emitting structures grown with original sublimation molecular beam epitaxy (SMBE) technique. The paper contains a description of the experimental facilities, results of the light emitting media (Si:Er and Si_1-xGe_x:Er) research and device applications.

Based on the transmission spectra of Er³⁺-doped LiNbO₃ 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 (utilising the density matrix formalism and the McCumber's theory and taking into account the Stark splitting of the levels), the oscillator strength of the absorption transition, the spontaneous emission probabilities, the radiative lifetime and the excitation energy in three regions of the optical spectrum: around 1550 nm, 980 nm and 550 nm, respectively. Also, we measured the rising and falling times and we calculated the homogeneous upconversion factor corresponding to the transition ⁴I_15/2->⁴F_7/2.

The paper briefly reviews existing computational techniques for electromagnetic wave propagation at optical frequencies (Discrete Dipole Approximation, the T-matrix - Extended Boundary Condition methods, the Multiple Multipole Method, Finite Difference (FD) and Finite Element (FE) Methods), and contributes to the development of FD methods. The overall objective is to put together a set of complementary tools for simulations in nanoscale photonics. One powerful tool - FE analysis - is applied to optimization of plasmon-enhanced AFM tips in apertureless near-field optical microscopy. Another tool is a new FD calculus of "Flexible Local Approximation MEthods" (FLAME). In this calculus, any desirable local approximations (e.g. scalar and vector spherical harmonics, Bessel functions, plane waves, etc.) are seamlessly incorporated into FD schemes. FLAME achieves a remarkable accuracy improvement, as compared to FEM, for problems with cylindrical and spherical plasmon nanoparticles and for a photonic crystal with an array of cylindrical rods and a waveguide bend.

This paper discusses methods for calculation properties of apodized fiber Bragg gratings (FBGs). These are one of the most enveloping optical devices in telecommunications and sensor systems. Work is aimed to simulation of FBGs, with utilization especially in sensor systems and laser interferometry for semiconductor laser stabilization at wavelength about 760nm. Program for FBG properties calculation was written in Matlab software. At first, FBG is divided into several uniform sections. To calculate properties of each uniform section is used coupled-mode theory. Coupled-mode theory is ordinary used for electromagnetic field specification in waveguides with periodic perturbations in the propagation direction. Next the transfer matrix method is used for overall properties calculation. The main point of simulation is reflectivity spectrum calculation in dependence of fiber dimensions and material properties. These FBGs have wide range of use in optical systems as band filters, in-fiber sensors or fiber grating lasers and amplifiers for their unique properties.

To analyze the impact of the infrared radiation emitted or absorbed on the quantum transport, the rectangular potential barrier is considered as a model of a nanostructure. The analysis is limited to the first quantization level in which only the electron is considered as a quantum particle but the electromagnetic field is classical and described by the vector potential. This model is used if the interaction of infrared radiation with semiconductor structures is studied and it is acceptable even for large electromagnetic fields present in lasers. The solution of the time dependent Schroedinger equation with the time-periodical electrostatic potential is carried out using the Floquet theorem. The coupling of electromagnetic radiation with free electron gas is included in the single electron Hamiltonian by the vector potential. The Kramers-Henneberger unitary transformation enables include the coupling as a time-dependent dressing term in the electrostatic potential. In the high frequency limit it is sufficient to consider only the time-averaged potential. The transmittance of the potential barrier is found using both methods and the results are compared; the effect of the electromagnetic field dressing is observable.

The greatest parts of numerical simulation methodology of photosensitive VLSI pixels are the planning of simulation procedure and numerical modeling results verification procedure. To design the optimal simulation methodology leads to obtain the accurate data for practical design of photosensitive pixels. After a series of simulations the algorithm for charge capacity CCD elements calculation through the two-dimensional physic-topological modeling had been developed. This algorithm gives the set of optimal driving voltages for CCD element too. This algorithm had been widely used in practical design of photosensitive CCD and demonstrates the good calculation time economy.

Accessibility of coherent light sources is accompanied by wide use of coherent optics methods, applicable in photonic devices. Currently, various types of relatively cheap laser diode modules (LDMs) are offered. Attention should be paid to coherent properties of them. Coherence of LDMs, which are offered and sold by a collaborating company¹, had been studied. In our previous work² we pointed out the properties of LDMs and suggested an improvement by cooling. The work has been kept on. Some preliminary results are presented. A method to measure very short coherence length is presented, too, and applicability of laser diode modules in photonic devices is briefly discussed.

This paper is devoted to creation of novel CMOS APS imagers with focal plane parallel image preprocessing. The general principle of analog subtraction is described. The important research direction devoted to analogue implementation of main preprocessing operations (addition, subtraction, neighbored frame subtraction, module, and edge detection of pixel signals) in focal plane of CMOS APS imagers. The following results are presented: the algorithm of edge detection for analog realization, and patented focal plane circuits for analog image reprocessing (signals subtraction, additional, edge detection).

The optical fiber cutoff frequency is by one of its critical parameters, which couple working wavelength of lights, optical fiber dimension and refractive indexes of core and cladding into one numerical parameter. If the operational wavelength of the light source will be shorter than the cut-off wavelength is, then the fiber will support except fundamental mode the propagation of several higher modes too. Such fibers conserve themselves the advantageous characteristics for telecommunication application (small auenuation, slight dispersion), but it is possible to use them for sensor-based applications utilizing the mode coupling among guided modes. For the external influences plotting (e.g. temperature) causing on telecommunication fiber along the transmission route then the attenuation shift is not applicable because it impends the transmission in its principle either by an BER increase with keeping the transmission rate constant or by transmission rate fall with constant BER conservation. None of these implications is acceptable in optical backbones. Once from among few possibilities how to solve this problem is to set the operating conditions of the SM fiber nearby cutoff normalized frequency. In the paper the basic theory together with the simulation of the mode distribution will be shown for particular types of optical fibers for temperature changes within the interval O°C-80°C.

Molecular-mechanics based simulations are applied to investigate the structures and phase stability of InGaN alloys. The variation of bond lengths and angles with increasing In composition is found. This causes the considerable structural change and the phase separation of InGaN alloys. The interaction parameter (Ω= -1.3435x + 6.1607 (kcal/mol) ) dependent on In composition is also calculated. The phase diagram for InGaN alloys shows an asymmetry with respect to x0.5. The critical temperature for the phase separation is 1392 K at x = 0.44. These results are in agreement with experimental results.

Thulium-Doped Fiber Amplifier (TDFA) are considered for long-haul transmission systems as they allow amplification in the S-band (1.46- 1.53 μm) thanks to the Tm³⁺ emission at 1.47 μm from the ³H₄-³F₄ transition. Presently TDFA are fluoride based because of the low phonon energy of this glass. But as it presents some drawbacks (reliability, splice to silica, ...), we propose to realize a silica-based TDFA. The fibre under investigation in this article has a high A1₂O₃ concentration in order to improve the efficiency of the 1.47 μm-thulium emission. The fiber has a low Tm concentration, around 40 ppm mol, a 16.5×10^-3 refractive index and a core radius of 2.3 μm. Lifetime from the ³H₄ and ³F₄ levels were measured to be 58 μs and 540 μs, respectively. Gain measurements were conducted using a single wavelength pumping scheme at 1060 nm and 1 W of pump power. Although the highest measured gain was 0.9 dB for a 4m long fiber, this experimental result was compared with numerical modeling. From these simulations, we estimate the characteristics of the fibre to increase the gain up to 20 dB.

Supercontinuum generation in planar rib waveguides promising for numerous applications is predicted theoretically. Its physical origin is connected with radiation and fission of higher-order solitons in anomalous dispersion region caused by the modification of dispersion by the waveguide contribution.

In recent years rapid progress has been made in the field of long-period gratings (LPG) inscribed in optical fibers. Though in most cases LPGs in standard commercial single-mode fibers have been investigated, great effort has also been put to LPGs in experimental fibers with modified structures, whose properties can significantly differ from those of LPGs in standard fibers. This contribution deals with two novel types of optical fibers for LPG inscription. The first of them is a single-mode fiber in which the refractive index in the fiber cladding increases quadratically with radius. In the second fiber, the cladding index decreases quadratically with radius. Basic results of a theoretical analysis of LPGs inscribed in these fibers are presented along with details on the preform fabrication by the MCVD method and on fiber drawing. Examples of transmission spectra of LPGs inscribed by a focused beam of a CO₂ laser are given and properties ofthe LPGs are discussed.

While fabrication of photonic components at the wafer level is a long standing goal of integrated optics, new applications such as optical interconnects are introducing new challenges for waveguides and optoelectronic component fabrication. Indeed, global interconnects are expected to face severe limitations in the near future. To face this problem, optical links on top of a CMOS circuits could be an alternative. The critical points to perform an optical link on a chip are firstly the realization of compact passive optical distribution and secondly the report of optoelectronic components for the sources and detectors. This paper presents two different approaches for the integration of both waveguides and optoelectronic components. In a first "total bonding" approach, waveguides have been elaborated using classical "Silicon On Insulators" technology and then reported using molecular bonding on top off Si wafers. The S0I substrate was then chemically etched, after what InP dies were moleculary bonded on top of the waveguides. With this approach, optical components with low loses and a good equilibrium are demonsrated. Using molecular bonding, InP dies were reported with no degradation of the optoelectronic properties of the films. In a second approach, using PECVD silicon nitride or amorphous silicon coupled to PECVD silicon oxide, basic optical components are demonstrated. This low temperature technology is compatible with a microelectronic Back End process, allowing an integration of the waveguides directly on top of CMOS circuits. InP dies can then be bonded on top of the waveguides.

Microstructure fibers (MSFs) are attractive for applications in fiber lasers and many other devices for optical communication. This paper deals with the preparation and characterization of MSFs with cores doped with ytterbium and erbium ions. The fibers were drawn from preforms consisting of a stack from a central rod and silica capillaries inserted in a silica tube. Rods whose central parts were doped with rare-earth ions were used. These rods were prepared by the MCVD method combined with liquid-phase etching. The fibers were characterized by optical microscopy and by measurement of their spectral attenuation. They were also tested in experimental amplifier and laser set-ups. The fibers were excited at 1060 nm and saturated gains of about 26 dB, or laser power conversion efficiency at a wavelength range around 1550 nm were measured. These measurements show results comparable with conventional fibers doped in the core with ytterbium and erbium ions.

The paper deals with optimization of fibre laser based on experimental erbium- and ytterbium-doped fibre with simple double-clad structure pumped by multimode laser diode in 980 nm band. Fibre preparation and its characteristics are described. Different resonator configurations were investigated for the laser optimization, including high reflectivity fibre loop mirror. Experimental optimization ofthe pump wavelength, fibre length and output coupler ratio were carried out. The results obtained under the cladding pumping are compared with those measured with a fibre ring laser containing the same fibre single-mode pumped at 1060 nm.

We describe the behavior of long period gratings (LPG) in 980nm pumped Erbium doped optical fibers. We have reformulated the coupled mode analysis of long period gratings to incorporate the gain term. Our results show that varying the gain coefficient can control the transmission spectrum of the grating by appropriate choice of pump power levels.

We implemented a frequency resolved optical gating (FROG) measurement method using cross-phase modulation (XPM) in a microstructured optical fiber (MOF). This method allows for measuring shorter pulses or pulses with lower energy than XPM FROG in a conventional fiber. High birefringence of the MOF must be accounted for. We found that the standard FROG reconstruction algorithm, the generalized projection (GP), failed for this setup and we used the genetic algorithm (GA) instead. Although GA is much slower than GP, it is a global search method which is less prone to get stuck to local minima. GA has several parameters that need to be adjusted. In this article, we present the optimization process and the optimal parameters for theoretically simulated data. FROG error less than 1 × 10^-4 is achieved in less than 30 minutes with our 32-bit program running on a single Cpu AMD Athlon64 3200+ under 32-bit Windows XP SP2.

Xerogel layers have been used in the development of fiber-optic chemical sensors with the aim of enhancing the interaction of detected chemicals with light waves transmitted in the fiber. In most of fiber-optic sensors xerogels layers have been applied onto the fibers. This paper shows an alternative approach, in which xerogel detection layers are applied onto the walls of holes of silica capillaries. Single capillaries as well as multiple capillaries of microstructure fibers were used as substrates for the application of xerogel layers. Sensitivities of the prepared layers to vapours of water and toluene were determined experimentally. In these experiments, light was coupled into the capillaries and the xerogel layers were brought into contact with gaseous mixtures of the chemicals and nitrogen. Spectral changes of the output light from the capillaries were measured in a wavelength range from 1300 to 1800 nm. Results of these measurements are shown and compared with those obtained for layers applied onto silica fibers. These results show that capillary fibers modified by xerogel layers offer novel means for increasing the detection sensitivity.

In this contribution we describe the similarities and especially the differences arising when typical methods for the characterization of optical channel waveguides are applied to waveguides fabricated in different substrates that strongly differ in the refractive-index contrast. Behavior of straight channel waveguides fabricated by i) ion-exchange technique K+ ↔ Na+ or Ag+ ↔ Na+ in borosilicate or Er doped silicate glasses, ii) Ti-diffusion into the LiNbO₃ substrate, and iii) silicon-on-insulator technology will be compared. Fabry-Perot resonator method based on a highly coherent fine-tunable semiconductor laser using different types of end-fire coupling arrangements will be described. Measurements of basic parameters of the optical waveguides, e.g. optical field distribution, optical losses, group effective index and their spectral dependencies will be presented and their features typical for particular waveguide structures will be compared.

Use of annular core fiber (ACF) for chemical trace analysis is novel approach in the field of evanescent wave optical sensors. It allows extending the sensitivity of conventional absorbance spectroscopy by extending optical interaction path length of evanescent wave. ACF is waveguide, typically consisting of small diameter tubes capable of guiding light through a sample by evanescent wave. AFC waveguides are capillaries that contain a liquid or gas sample for spectroscopic analysis. The core of doubly clad step index optical fiber is a dielectric annulus lying between two different claddings. Benefit of this solution is possibility to use of small volume samples, long path lengths by constraining light propagation within a liquid or gas medium by evanescent wave. Preform preparation by MCVD process and fiber drawing and coating of this special capillary structure have been realized in the workplace of IREE AS CR. Primary shielding of silica capillary is ultraviolet radiation activated acrylic copolymer. Basic optical characteristic were measured - attenuation, refractive index (RI) profile, loss spectral distribution, near field intensity distribution.

Paper presents some results obtained by the measurement of polarization properties of fibers in the incidence of different external effects as temperature, torsion and magnetic field. To emphasize applied physical effect rare earth (Nd³⁺) fiber has been used. Study of polarization is important from the polarization dispersion point of view for communication systems and also in the area of interferometric and polarization sensors, distributed sensors or general interferometric measurements. Analysis of individual effects is solved theoretically and practically in the series of works. Our contribution solves a relatively short part of fiber, where additionally fluctuation of power between both polarization modes could affect.

Different interferometric methods were used to measure the dispersion characteristics of a holey fiber, in which birefringence is induced by two large holes adjacent to the fiber core. Employing a lateral force method, we measured the spectral dependence of the phase modal birefringence for two lowest-order spatial modes. Using a wavelength scanning method and a technique of spectral-domain tandem interferometry, we measured the spectral dependence of the group modal birefringence for both spatial modes over two different wavelength ranges. The technique of spectral-domain tandem interferometry, which employs a white-light source, a polarizer, a tandem configuration of a Michelson interferometer and the optical fiber, an analyzer and a low-resolution spectrometer, was also used to measure the intermodal group dispersion. Two different group optical path differences between both spatial modes, which were X- or Y-polarized, were measured as a function of wavelength.

We report about fabrication and properties of Gallium Nitride (GaN) layers containing the Rare Earth (RE) ions. Gallium nitride is a promising wide band gaps direct semiconductor material, which doped with the RE ions would play a very important role in various optoelectronics and photonics applications. The GaN thin films were deposited by magnetron sputtering in Ar + N₂ gas mixture using Ga₂O₃ target as the source of Gallium. For the RE doping, the Er₂O₃, Yb₂O₃, Pr₂O₃ and Nd₂O₃ pellets, or Er and Yb powder were laid on the top of the Ga₂O₃ target. The GaN layers were deposited on silicon, silica on silicon, Corning glass or quartz substrates. The results of the experiments were evaluated in terms of the relations between the technology/precursors approaches and the composition and luminescence properties of the fabricated thin films.

A preliminary study of the effects of coherence on the transmitted field through a photonic crystal is presented and discussed with reference to a particular geometry.

Operation of some optical devices such as a surface plasmon resonance compact sensor relies on cylindrical waves. On the contrary, optical power is usually transmitted via collimated beams. A holographic grating structure may serve in coupling of a collimated laser beam and its transformation into the beam with the cylindrical wave front, and the vice versa transformation on outcoupling. The paper deals with the role of an aperture shape in focusing of the cylindrical waves. Elliptical and rectangular apertures are discussed, and the transversal as well as longitudinal diffraction in the zone of the focal line is studied. A special feature of this problem is that in the focal plane the Fraunhofer diffraction takes place only in the direction perpendicular to the focal line. The Fresnel difracton causes a modulation along the focal line. A consequence of the elliptical aperture is that the focal line is not illuminated uniformly: illumination declines from the center to the ends. For practical purposes the rectangular aperture turn out to be much more suitable.

Dynamics of powerful femtosecond singular-phase pulsed beams in a dielectric medium under the ionization conditions is analyzed numerically. The multiphoton ionization is revealed to contribute to the stable (quasi-soliton ) regime of pulse propagation over distances exceeding five diffraction length. Use of the singular beams allows one to reach the larger densities of the light field and generated plasma.

When observing remote celestial bodies and examining the structure and evolution of space it is important to acquire and analyze the spectrum of stars by means of dispersion gratings. To do so, we developed for the Subaru telescope facility in Hawaii a highly dispersive volume phase holographic (VPH) grism with high efficiency of 80% or more and high resolution from 2500-8000 covering the visible wavelength region. The VPH grism consists of two prisms and a refractive index modulation grating which satisfies the Bragg diffraction condition. To achieve highest performance we employed the rigorous coupled wave analysis (RCWA) in designing the VPH grating made from photopolymer. The grating was fabricated with grating periods ranging from of 0.68 to 1 μm for design wavelengths of 400nm, 520nm and 680nm. We further worked out the relationship between the thickness of the grating and the refractive index modulation of the polymer, rigorously analyzed the gradient of the interference fringes and multi-layers structure using glass substrates. The design and evaluation based on RCWA is effective for the fabrication of high-performance VPH grisms and will be thoroughly presented in this talk.

Elliptical outgoing beam is the main drawback of edge-emitting diode lasers, and for majority of their applications the elliptical beam needs to be transformed into another cross-sectional shape. Usually, a collimated circular beam with appropriate diameter is requested. Such a beam can be obtained in different ways, and this contribution deals with one of them - usage of off-axis holographic diffractive optics. Compensation for beam ellipticity from 1:2 for near infrared to 1:4 for visible spectra of the diode laser beam can be realized by holographic diffractive singlets recorded onto spherical substrate. Singlets employing for these ellipticities have to work in a strong off-axis mode with angles of diffraction reaching 75 deg. Theoretical analysis is presented and experimental results are given for reflection mode of operation.

The theoretical model of the evanescent waves coupling with dielectric and metallic strip gratings is described. The interaction of electromagnetic field with lamellar periodic structures and their diffraction properties are determined by coupled wave method implemented as the Fourier modal method. The simulations of the ellipsometric response under internal reflection for different geometrical and material configurations are presented. The attention is concentrated on the study of coupling strength influence, effects connected with stripes geometry, and, with absorption in metallic elements of grating.

Holographic gratings that are recorded as a whole in a single exposition are limited in size because of the available power of suitable laser sources and nonlinear response of and/or reciprocity effects in a recording medium. A sequential-illumination technique can help in this case. This technique relies on piecewise grating recording that consists in scanning with a relatively narrow laser beam, a pencil, across the grating surface employing an appropriate optical set up. The contribution describes a method utilizing a small parallel displacement of the laser pencil by turning a plane-parallel plate, which is then transferred to a larger angular deflection by a short focus lens. Simultaneously, the beam is expanded angularly. This all can take place either before light enters the beam-splitter or along paths of both the interfering beams. In this way, uniform diffraction efficiency gratings that are much larger than the cross-section of the beam can be achieved. The laser pencil can be moved in polar or rectangular coordinates. Recording of larger gratings supposes large precise collimating mirrors. If they are not available e.g. due to their high price, they can be replaced by long propagating homocentric beams with their origins in the same distance from the recording plate.

The article is considering by applications of electronic speckle pattern interferometry (ESPI) in the composite materials industry. The use of composite materials in various construction elements has substantially increased over the past years. These materials are widely used in situations where large strength-to-weight ratios are required. This paper collects some information about possibilities, advantages, and disadvantages of ESPI applications by nondestructive testing of composite materials and briefly introduces a damping feature of composites. Theory of plate vibrations allows us to determine Poisson's ratio V , Young's modulus E and shear modulus G from the measured resonant frequencies. We are able to analyze the damping behavior of various types of composite materials from measured mode shapes.

A two-channel demultiplexer with channel spacing 1nm and the bandwidth around 1nm is demonstrated. The demultiplexer device is established based on cascaded holographic filters. Each filter addresses a channel. Each filter is established by constructing a single volume holographic gating in a single LiNbO₃ crystal and it drops the light from a specific DWDM channel (wavelengths of ~1550nm) with 90-degree geometry. Volume holographic gratings in photorefractive material have been applied to demultiplexer devices in DWDM systems owing to the narrow spectral selectivity. However, when channel numbers in a volume hologram is increased, we have to store more holographic gratings in this recording medium. Thus, the diffraction efficiency of each channel will decrease because all the gratings share the dynamic range of the recording material. In our design, the dynamic range can be efficiently used and thus the diffraction intensities of each channel can be increased. In addition, the device could be compact owing to the 90-degree geometry. In this device, we can increase the channel number by cascading another different filter.

Volume holographic storage has received increasing attention owing to its potential high storage capacity and access rate. In the meanwhile, encrypted holographic memory using random phase encoding technique is attractive for an optical community due to growing demand for protection of information. In this paper, encryption-selectable holographic storage algorithms in LiNbO₃ using angular multiplexing are proposed and demonstrated. Encryption-selectable holographic memory is an advance concept of security storage for content protection. It offers more flexibility to encrypt the data or not optionally during the recording processes. In our system design, the function of encryption and non-encryption storage is switched by a random phase pattern and a uniform phase pattern. Based on a 90-degree geometry, the input patterns including the encryption and non-encryption storage are stored via angular multiplexing with reference plane waves at different incident angles. Image is encrypted optionally by sliding the ground glass into one of the recording waves or removing it away in each exposure. The ground glass is a key for encryption. Besides, it is also an important key available for authorized user to decrypt the encrypted information.

One of the main advances of dynamical holography is the possibility to operate with coherent images in real-time experimental situation. Non-degenerate four-wave mixing has some advantages among different holographic methods because it gives the possibility to perform visualization of infra-red images or to convert visible radiation into ultra-violet region. In the work we study different schemes of frequency conversion of coherent images by thin and volume dynamic holograms nonlinearly formed in multilevel resonance media in conditions of non-degenerate four-wave mixing. The theoretical model of dynamic gratings formation in dye solutions based on coupled-wave equations has been developed. Experimental realization of frequency conversion of coherent images from infra-red to the visible and between different wavelengths of visible region has been performed. It has been shown that the criterion of hologram thickness is dependent on the optical density of medium and intensity of input radiation. The diffraction efficiency of dynamic gratings has been measured in conditions of optical bleaching and in the mode of strong absorption, enabling recording of thin gratings.

The need for high speed communications together with availability of novel photonic devices have triggered a development of broadband optical networks. Current techniques for accessing bandwidth in a multi-user environment in optical networks rely on dense wavelength-division multiple access (DWDMA) and time-division multiple access (TDMA) approaches. On the other hand, code-division multiple access (CDMA) has been used more in RF wireless communication systems. However, by combining CDMA approaches with emerging optical technologies and novel code design, optical CDMA systems that provide unique multi-user access to shared optical bandwidth can be realized.

A simple device, Frequency Tracer (FT), for ultrashort light pulse duration and chirp simultaneous measurement is introduced. FT operation is based on the second-harmonic autocorrelator beam two-dimensional image analysis (time versus frequency), and it is able to evaluate the temporal phase variation over femtosecond pulse duration. The spectral information of fs pulse in FT originates from the angular divergence of a second-harmonic signal beam, and there is no need in using the spectral apparatus. Femtosecond pulses duration and chirp measurements of the Ti:sapphire laser system multipass amplifier (MPA) during adjustment of compressor pair of gratings were done.

Results of experimental investigation of diode pumped Nd:YVO₄ laser passively mode locked using either second harmonic nonlinear mirror or semiconductor saturable absorber are reported. As an active element the 5mm long Nd:YVO₄ crystal end pumped by 20 W fiber coupled laser diode was used. The linear folded resonator has on the other end either saturable absorber with single 15 nm thick In _0.25 Ga_0.75 As quantum well layer integrated on the top of Bragg mirror (SESAM) either nonlinear mirror (NLM) consisting of a dichroic dielectric mirror and 10 mm long type I LBO crystal critically phase matched for second harmonic generation. Using the nonlinear mirror the threshold for mode locked operation was 10 W of pump power and we obtained 4.5 W of output power with single pulse duration of 6.2 Ps for pump power of 15 W. Using the SESAM the pulse duration of 13-16 ps was achieved for pump power from 3W to 18 w for low output coupling.

A very low-loss and low switching energy vertical micro-cavity has been developed for all-optical signal reshaping. This saturable absorber-based device shows insertion loss as low as 0.2 dB and a switching energy of 13 μJ/cm² while keeping a response time lower than 5 ps. Such a low loss and low switching energy device has high potential applications in 2R regenerated transmission lines.

Light wavefront inversion (phase conjugation) in a-As-S-Se films has been studied experimentally. Phase conjugation (PC) of plane and spherical waves is carried out in a-As₄₀S₁₅Se₄₅ films using degenerate four-wave-mixing (DFWM) geometry at 633 nm. In the plane wave case simultaneous PC efficiency and DE measurements have been made versus exposure time, light intensity and holographic grating period. The maximal PC efficiency was 2.3% and the minimal PC specific recording energy was 2 J/(cm²%) whereas the maximal DE was 0.9% and the minimal specific hologram recording energy was 10 J/(cm²%). The optimal grating period was 2 μm. When compared to a-Se films a-As-S-Se films exhibit lower PC efficiency but higher photosensitivity. The advantages of a PC setup for the investigation of photoinduced processes in comparison with a usual holographic setup are observed.

The results of theoretical investigations into two-wave mixing in media with saturated absorption and refractive index modulation are presented. The processes of nonlinear self-focusing, self- and cross-modulation due to scattering on dynamically-induced optical gratings are taken into consideration. Numerical modeling of spatial solitons formation and interaction in the volume of nonlinear medium was performed.

The paper is a study into the spectroscopic and nonlinear-optical properties of semiconductor photorefractive crystals based on cadmium telluride (CdTe) doped with transition metals or irradiated by electrons and gamma-quanta. The protorefractive response is analyzed using the four-wave mixing pattern of laser pulses one of which is delayed in time. It is found that both irradiation and doping of cadmium telluride crystals with vanadium, titanium or iron leads to changes in the spectroscopic and nonlinear-optical properties of the crystals. Apart from relatively narrow (about 100 nm ) bands appearing in the absorption spectra due to additional energy levels within the band gap, one can observe variations in the absorption factor over a wide spectral region ( 1-3 μm). Recording of dynamic holograms is realized with no external electric field owing to pulsed laser radiation at a wavelength of 1.06 μm and diffraction efficiency of 1-2%. Continuous laser excitation (1.5 μm wavelength and an applied external electric field of about 2 kV /cm ) with the use of the two-wave mixing pattern has enabled energy transfer to a weak wave giving the amplification factor that comes to 1 cm^-1.

A new scheme for all optical XOR and NOTXOR based on UNI (Ultrafast Nonlinear Interferometer) technique is demonstrated on a 10 GBps data pattern. As a difference between our schema with the old UNI structure, we employ a counter-propagation geometry that avoided the use of a filter and wavelength converter for the elimination of the control signal at the output of the system. Likewise in this scheme only one polarization maintaining fiber (PMF) is used.

We report on recent results of laser ablation in semiconductors obtained by simultaneous irradiation of the sample with a superposition of the fundamental beam of a picosecond-Neodymium-Vanadate (Nd:VAN) laser (1064 nm, 10 ps pulse duration) and a small fraction of its second harmonic (SH) produced in a thin nonlinear crystal. In this fashion, the ablation yield could be increased by 70%. In addition, the ablation quality was improved in terms of surface smoothness. The underlying mechanism can be attributed to a 'seeding' of the target area with free carriers by the 532 nm radiation.

The results of theoretical and experimental investigations into four-wave mixing in microresonators with resonant and thermal nonlinearities are presented. Theoretical models of dynamically-induced optical gratings have been derived in two cases of the light beams interaction: when a nonlinear medium is incorporated into Fabry-Perot interferometer and for the off-cavity configuration. Experimental realization of intracavity four-wave mixing performed using ethanol solution of Rodamine 6G as a nonlinear medium. It is shown that the use of nonlinear interferometer increases significantly an efficiency of dynamic optical gratings. The potentialities for obtaining of high efficiency conversion of optical information owing the spectroscopic properties of multilevel resonant media are discussed.

Photorefractive one-dimensional photonic lattices are optically induced in iron-doped lithium niobate. Discrete linear diffraction and formation of bright gap solitons due to nonlinear self-action of light beams within such lattices are experimentally investigated at wavelength of 633 nm.

We present an analytic method to determine the modulus of the coupling coefficient between polarization modes in the semiconductor optical amplifier (SOA) subjected to a cross polarization modulation (XPolM). We evaluate also the impact of the dependence in polarization of the gain on mode conversion. This analysis is based on the association of the coupled mode theory with experimental measurements of the Stokes parameters at the output of the SOA. A validation of the model is made with a good accuracy.

In this paper a new HS chromaticity diagram for 10-degree observer with more linear colour distribution is presented. Both, the spectral locus and curve of purple colours generate unity circle -the HS diagram. By using the CIE lightness L as the third dimension, the Lrnn colour space is generated. This new colour space is embedded into cylinder radius of 100 (it stands for chroma) and height of 100 (it stands for lightness). If n is plotted against m the points in resulting Lmn-space are not uniquely related to chromaticity because their position depends on the value of L. The colours of all object-colour stimuli fall within this cylinder boundary. The spectrum locus of the monochromatic stimuli is generally well outside the boundary of object-colour stimuli.

The paper deals with influence of the 2D sampling process upon image quality. The Optical Transfer Function (OTF), which is closely related to the Point Spread Function (PSF) of optical and electro-optical imaging systems, can be regarded as an objective measure of their quality. The main goal was the implementation of direct and blind deconvolution methods in MATLAB environment, in order to estimate these parameters and use them for computation of other characteristics, such as the Modulation Transfer Function (MTF) and the Phase Transfer Function (PTF). Relations between these functions are very useful in deriving the MTF for various geometrical shapes of elementary detectors of image sensors. This paper is focused on direct deconvolution by inverse and Wiener filtering, special focus is held on blind deconvolution using Iterative Blind Deconvolution (IBD), Simulated Annealing (SA) and Blind Deconvolution by Genetic Algorithm (BDGA). The whole process has been modeled in MATLAB. The Graphical User Interface (GUI) was also developed for setting of the deconvolution methods parameters. The parameter PSNR was also used for comparison and evaluation. The image deconvolution method based on the Blind Deconvolution by Genetic Algorithm seems to be very useful, especially from the point of view of computational requirement and results as well.

The subjective image quality seems to be one of crucial parameters in modern multimedia systems. The perception of observer is a final issue to be followed and technical parameters of the system are the issues of second order. Therefore the traditional approach of "fidelity" would be better consequently replaced by the multimedia term the subjective image perceived quality or "goodliness". It can be shown that some distortions and/or artifacts can be perceived as pleasant and the goodliness will be increased when the distortion level is increased. At the same time the fidelity will drop down. Based upon more than four years of research experience the paper discusses various impacts of modem multimedia technology on the subjective quality of image. The main attention is focused on the image compression techniques and standards. The nature of distortions and artifacts is demonstrated on selected examples of image compression standards (fractals, DIVX, VP6 etc.). Finally the relevant image quality parameters are listed and analyzed for the area of imaging security systems.

This paper deals with the subjective and objective image quality evaluation. The demand of an accurate image and video objective quality assessment tool is extremely important in modern multimedia systems. Possible enhancement of the performance in existent image quality assessment approaches using multiple quality measures with the support of the artificial neural network data processing is proposed. The analysis results of the known quality measures and their suitability for the particular image or video quality assessment problem are presented. The most suitable measures are used to implement the novel image quality assessment tool using artificial neural network data processing. Optimization of the proposed model has been done in order to achieve as highest generalization feature of the model as possible. Performance of the implemented model for the image quality assessment has been evaluated using the database of distorted images and subjective image quality assessment results with respect to the Mean Opinion Score (MOS) obtained by the group of observers. It is shown that the proposed image quality assessment model can achieve high correlation with the subjective image quality ratings.

This paper introduces video compression and image processing methods for fast multimedia channels. Standards designed for image and video coding (JPEG2000, MPEG-4 and MPEG-7), being not strictly defined, present a large field for further experiments and improvements. Our method was developed on fundamentals of Vector Quantization (VQ) and the most advantageous qualities of Karhunen-Loeve Transform (KLT) (known also as Principal Component Analysis - PCA). We also present a direct an idea of how to implement optical transform that can be used with accordance to the methods presented. Among other compression techniques, KLT optimality is discussed as a purpose for further improvement to the method.

Image compression algorithms based on the discrete wavelet transform are nowadays very popular for their power and other properties. However, classical decomposition of the image with one static mother wavelet is generally far from optimal. This paper introduces a lossless still image compression method based on spatially adaptive wavelet transform, where the mother wavelet is varying along the signal to achieve better energy conservation. The decision-making process, which is responsible for mother wavelet selection, works in dependence on local pixel values and internal statistics. New mother wavelet is determined for every coded pixel (deccorelation step). The preliminary results of this method on several images of different types show, that the compression ratio of proposed method is comparable to the JPEG2000 algorithm with static 5/3 wavelet filter. Our intention is to apply this new adaptive method to the compression of astronomical images and optimize carefully the decision-making process according to this type of images. Since these images have very specific properties, we expect that our method will overcome JPEG2000 and also recent compression algorithms used in astronomy (HCompress, PMT or FITPRESS).

Small robotic telescopes (like BOOTES in Spain, BART in Czech Republic or FRAM in Argentina) are constructed for continuous galactic survey and fast reactions to GRB (Gamma Ray Burts) alerts. Due subtile construction performance of those instruments strongly depends on temperature, atmosphere scintillations etc. In this article will be discussed possibilities of performance improvement based on knowledge of any transfer characteristic like modulation transfer function MTF (or Point Spread Function PSF of course) of imaging system introducing a robotic telescope.

For the purpose of biophotonics, free running and Q-switched Er:YAG lasers were constructed. As Q-switches the rotating mirror and Pockels cell were used. In the case of rotating mirror placed inside the resonator the maximum of generated laser energy was 210 mJ in a free-running mode regime when pulses up to 110 μs long (FWHM) were generated. The resulted parameters of the giant pulses were 30 mJ energy, and 250 ns pulse length. For the Pockels cell Q-switching, the laser was generating 325 mJ of energy in a 250 μs pulse, and 60 mJ of energy in a 60 ns pulse in the case of free running and Q-switched regime, respectively. This output properties together with the generating wavelength (2.94 μm), coinciding exactly with the absorption peak of water, giving us the possibility of using this radiation to the efficient interaction with biological tissue. The transport of the radiation to the interaction place was solved by the special cyclic olefin polymer coated silver hollow glass waveguides with the inner diameter of 700 μm and the length of 10 - 50 cm. For the contact treatment the sealed caps were used for preventing delivery system damage. The aim of this work was except of special laser systems development, the investigation ofthe effect differences between long (free running) and short (nanosecond) laser pulses on ophthalmic (cornea, sclera), urologic (ureter wall), or dental (enamel, dentine) tissue.

A rapid analysis of microorganisms is necessary for medical, pharmaceutical or food technology applications to identify harmful bacteria. Conventional identification methods require pure cultures from isolates and are often time demanding. Raman spectroscopy offers an alternative approach to identify microorganisms. With Raman microscopy it is possible to measure structures in the sub micrometer range, and therefore single bacteria cells are accessible. Micro-Raman mapping experiments proof that the bacterium shows a spatial homogeneity, since bacteria normally exhibit no compartments, therefore one spectrum of a single vegetative bacterial cell is sufficient to identify the strain. In contrary bacterial spores and yeast cells exhibit a high spatial dependency of the observed Raman spectra. For heterogeneous samples like single spores or yeast cells a mean spectrum from up to ten different positions is required to describe the complete cell. Using micro-Raman spectra of single bacterial cells and average spectra of yeast cells it is possible to create a database and identify microorganisms on species or even strain level.

Tracing of foreign objects inside living cells is very exciting way how to study interior of living objects in nondestructive way. We imported fluorescent submicron particles into the living cells using liposomes as carriers to study the local mechanical heterogeneity of the cell cytoplasm. Thermal motion of these probes within the cell is tracked using fluorescent video-microscopy. The time-records of the probe positions reveal their trajectories and accessible space to the probes inside the cytoplasm of living cells. Further analyses of the thermal motion of the probes can reveal the mechanism of sub-cellular transport and properties of the cytoplasm in vivo.

Thin films of ZrO₂ and hydroxyapatite/ZrO₂ were created by pulsed laser deposition using KrF and ArF excimer laser. Films were tested by XRD, SEM and WDX methods and in-vitro for cytotoxicity, adhesion and cell proliferation.

We demonstrate how the standing wave created from two counter-propagating non-diffracting (Bessel) beams can be used for confinement of sub-micron sized particles. At the same time we proved that changing the phase shift between these two beams can be efficiently used for precise delivery of sub-micron objects in unison. We succeeded in delivery of polystyrene particles of diameter 410 nm over a distance of 300 μm.

A heated probing tip of the scanning microscope being placed in close vicinity to, but not in atomically dense contact, the sample surface with smaller local temperature , may produce a very intensive microwave radiation flux onto the surface via evanescent modes of electromagnetic field. The necessary condition implies existence of overlapped absorption frequency domains both for the tip and sample materials. We consider this problem theoretically discussing several mechanisms of the heat transportation to and from the tip: a heating from the background radiation of vacuum chamber, the contact heating through the tip holder, and cooling by radiation emitted onto the surface. We have estimated the possible effects at different tip and sample materials and conclude that the largest radiation effects (at room temperature conditions) have to occur when using materials with similar dielectric properties. A construction of an oscillating microwave source is proposed using normal vibration mode of the scanning probe microscope. Numerical estimations of the output power and radiation frequency range involved are given.

The overview of the last investigations in the areas of scanning near-field optical microscopy (SNOM), surface diagnostics and surface modification with nanometre resolution using SNOM are observed. The operation principles of different types of SNOM are examined. The various method of SNOM probes fabrication with high transmission coefficient, in particularly, on the base of tapered single-mode optical fiber are studied. Besides high resolution imaging SNOM areas of application in scientific research are the local optical diagnostics of sample surface and surface modification for superhigh density data recording and nanoelectronics. The different methods of SNOM diagnostics are observed. It are the local optical spectroscopy of semiconductor nano-objects (quantum wells, wires and dots), near-field photoconductivity of heterostructures, the mapping of semiconductor laser radiation in near-field zone, the creation of point source of terahertz radiation and so on. The various methods of pattern fabrication with minimal size ofabout 30 - 50 nanometres using SNOM are investigated.

Scanning probe microscopy with multiple optically held probes is presented. Acousto-optical deflectors are employed to rapidly switch the optical trap between two positions so that the trapped probes are not allowed to leave the trap region. The probes are fluorescently labelled and their vertical position is acquired from the level of two-photon fluorescence. This particle position detection technique is very sensitive and allows obtaining surface details with resolution better than 10 nm. Using two probes simultaneously accelerates the measurement process and allows scanning of larger regions.

We use a laser-irradiated metal tip to create a locally enhanced field at the tip apex. The tip acts as an optical antenna and is held a few nanometers above the sample surface so that a highly localized interaction between the enhanced field and the sample is achieved. The method has been successfully combined with vibrational spectroscopy by making use of the well-known effect of surface enhanced Raman scattering (SERS). We mapped out the vibrational modes of individual single-walled carbon nanotubes (SWNT) with a resolution down to l0nm.

In this paper we describe properties of optical forces and torques acting on colloidal particles placed into interference laser field created by three plane waves having wavevectors in one plane. We assume interference of all three beams and we study the properties of this 2D optical lattice and particle behavior. This set-up enables selective confinement according to particle sizes which could be used for optical extraction of some components from colloidal system.

The use of QDs as a basis for new optoelectronic devices is very promising, due to a long electron lifetime at their excited levels. Therefore the inter- and intra-band light absorption studies in QDs are useful not only for investigations of photodetectors but they also are the necessary condition of the development of new types of mid-infrared lasers. The preliminary results of experimental and theoretical studies of the optical phenomena in n- and p-doped InAs/GaAs QDs and artificial molecules formed by pairs of QDs are presented.

Group theory is a mathematical method, largely used in applications like quantum mechanics and radar theory, which allows establishing a direct relation between the elements of different groups and that can be easily extended to optics. The groups of the special unitary matrices, SU(n), possess a great importance in the field of optics, as they can be related to the light polarization, planar propagation properties and optical devices properties. By means of the Pauli, Gell-Mann and Dirac matrices, respectively for n=2, n=3 and n=4, a corresponding coherence matrix can be defined. In the case of n=2, this coherence matrix describes the behavior of optical radiation at any case, polarized, depolarized or partially polarized light. For n=3, it can be used for the analysis of non-planar waves. Finally, for n=4, the coherence matrix allows the analysis of the polarization properties of the optical devices, from linear and deterministic media to highly scattering or depolarizing media. In this work, the theoretical background of the group theory and its application to optics is described, and some examples of its application are presented, for instance, the description of optical devices by the Quaternions and the application of 4x4 coherence matrix for the characterization of biological tissues by means of the entropy-factor.

At the FMPI Comenius University, also education in Optics and Lasers study programme at the undergraduate level (the 4th-5th years of MSc study) is offered. Compulsory laboratory works on Wave Optics, Quantum Electronics, and Nonlinear Optics, also are included. Some of advanced laboratory works, especially in wave optics and nonlinear optics, are presented, in order to share ideas and opinions related to the educational process.

The laboratory works are meant to train the university students mastering modem information technologies and techniques based on optical data transmission and processing. These works involve the use of fiberoptic systems and transmission methods for optical signals. Students study the operation principles of fiberoptic communication and processing systems, optoelectronic components, one- and multimode fibers, optical input/output couplers, multiplexers, optical dividers and connectors.