High intensity laser pulses offer key means for the growth of novel photonic structures exhibiting passive, but also active optical functionalities. New materials and complex structures are developed by pulsed laser deposition by utilizing the highly energetic multi-component laser plasma. Additionally, reactive sputtering methods and the flexible control of growth conditions offer the potential to tune the materials structure on growth, thus yielding unique properties in the finally produced device. Purely epitaxial thin film waveguides for laser sources and nanocomposite thin layer and composite multi-layer structures for dynamic hologram recording and physicochemical sensing have been demonstrated. Spatially selective and precise laser ablation offers unique opportunities and opens up new avenues for surface processing and microfabrication commencing with the realization of surface etched and, especially, printed passive and active diffractive micro- and potentially nano-structures.

Photo-excitation processes were investigated in Chlorophyll solutions by irradiation with various light sources. The photo-excited volume and surface effects found during bleaching experiments with Ultra Violet (UV) and Visible (VIS) spectra irradiation were recorded by dynamic optical beam diagnostics. The in-situ optical diagnotics for several spatial beams with different wavelengths was treated in a Beer-Lambert vectorial form. Bleached Porphyrins were photodeposited from Chl solutions on polymethyl-methacrylate (PMMA) surfaces using UV photons. The photodeposited material was confined by masks to simple patterns. The complex photodeposition processes of the bleached material is initiated by UV photons, followed by a VIS photons post irradiation and final fixation in the dark. Optical density profiling along with optical and scanning microscopies show a non-crystalline, bio-organic ovoid characteristic microstructure of the deposited material.

Optical code division multiplexing (OCDM) technique and its applications to ultrafast photonic network are reviewed. After introducing the principle operation of OCDM, several experimental demonstrations are presented. These include a high spectral efficiency OCDM/WDM transmission, photonic access node, optical path networks, and photonic routing.

Maximally entangled states, Werner state and maximally entangled mixed states (MEMS) have been created and fully characterized by a novel high brilliance universal source of entangled photon pairs with striking spatial characteristics. Mixed states of any structure, spanning a 2 x 2 Hilbert space may be created by this source. The non local properties of the generated entanglement have been tested by standard Bell measurements. Tunable Werner states and Maximally Entangled Mixed States (MEMS) have been created by an original patchwork technique and investigated by quantum tomography. The entropic and nonlocal properties of these states have been also undertaken.

Soliton formation in photorefractive crystals with strong optical activity is analyzed. We shall demonstrate that self-confinement of the laser beam is not enough to define such a beam "a soliton": in fact this state is completely define by both intensity and polarization soliton dynamics. We report here the characterization of the soliton state for CW and pulsed beams.

Among the various characteristics of solid-state lasers their emission wavelength, operating regime and output power are of major importance. This paper shows how chemical concepts can help to design or choose the best laser material for a given set of characteristics through the "structure properties relationships." Specific examples are given for the three above-mentioned properties: Neodymium activated lasers operating in the ⁴F_3/2 → ⁴I_9/2 channel and Cr⁴⁺ activated materials, for the wavelength adjustment; Ytterbium doped crystals for femtoseconds pulses generation, as an example of the material adaptation to a laser operating regime; Prediction of the thermal conductivity of a material: an important parameter for the production of high power laser beams.

The paper discusses some directions for improvement of efficiency and power scaling of Nd lasers: (1) the direct pmping into the emitting level ⁴F_3/2; (2) the use of concentrated Nd laser materials; (3) new laser materials, particularly ceramic materials; (4) advanced laser resonator design.

High-density plasma created near a solid surface by an intense femtosecond laser pulse emits ultrashort x-ray pulses that are synchronized with the laser pulse. We show the spectral and temporal properties of broadband soft-x-rays emitted from a femtosecond laser-produced plasma on a metal surface. The soft x-ray emission was increased about 20-fold by fabricating an array of nanocylinders on a gold surface. We demonstrate the cross-correlation measurement of soft x-ray pulse duration in the femtosecond region by using an optical field-induced ionization process in Kr gas. We used a 10-ps soft x-ray pulse to demonstrate the time-resolved absorption measurement of optically excited silicon near its L_II,III edge. We also employed a picosecond soft x-ray to measure the spatiotemporal evolution of ablated particles in femtosecond-laser-produced aluminum plasma.

We report spectral features of a frequency-shifted-feedback semiconductor laser with the anti-reflection coating of low reflectivity on the output facet. Although many peaks due to the chip mode were observed, a few peaks are connected each other without break showing a continuous spectral range wider than 100 GHz. A homodyne detection of the laser output showed higher order beat signals supporting the continuity of the laser spectrum over wide spectral range.

Mathematical modeling, based on rate equations, is used to estimate the theoretical limits of the emission efficiency of 3-μm Er:YAG laser in various generation regimes. This model uses exclusively spectroscopic data and includes upconversion from both initial (4I11/2) and terminal 4Il3/2) laser levels and cross-relaxation from the 4S3/2 level. The energy transfer processes, very active at high erbium concentrations, assure the re-circulation of the excitation on the metastable levels of Er3+, leading to supraunitary quantum efficiency and high emission efficiency in CW regime. In contrast with the CW (and free-generation) regime, the energy transfer processes are frozen during the generation of the giant pulse in Q-switch regime, limiting severely the access to the stored energy. As a consequence, the efficiency in Q-switch is low. We find simple analytic expressions for the emission efficiency in CW, free-generation and Q-switch regimes. We compare the results of the modeling with the available experimental results. Finally, some suggestions to improve the overall efficiency of the 3-μm erbium lasers working in Q-switch regime are given.

The structural data obtained from of high resolution optical spectroscopic investigations on Nd³⁺, Eu³⁺ and Yb³⁺ ions in rare earth calcium oxoborate crystals RCOB, mainly GdCOB and YCOB, but also EuCOB, are compared with those obtained from other studies such as X-ray diffraction or differential thermal analysis. The dependence of non-equivalent center intensities and on R³⁺ (dopants) ionic radii is in qualitative accord with X-ray diffraction data. The glassy like behavior of ⁴F_3/2 Nd³⁺ emission under selective excitation, as well as the shift of one line of ⁵D_o → ⁷F₁ Eu³⁺ emission are explained in terms of cationic structural disorder of RCOB crystals.

High power blue radiation obtained by intracavity frequency-doubling of a continuous wave diode end-pumped Nd:YAG laser operating on the ⁴F_3/2 → ⁴I_9/2 transition is reported. The maximum output power for the randomly polarized beam at 946 nm was 3.7 W for 9.5 W absorbed pump power at 808 nm; the slope efficiency with respect to the absorbed pump power was 44%. For the polarized fundamental radiation the maximum power was 1.1 W (26% optical-to-optical efficiency with respect to the absorbed power), the laser operating with 38% slope efficiency. Intracavity frequency-doubling by a 2.0-mm thick KNbO₃ crystal placed in a linear resonator yielded 159-mW single-ended blue-output with optical conversion efficiency versus the absorbed pump power of 4.8%. Using a V-type resonator increased the blue power at 418 mW with 11.6% optical conversion efficiency in absorbed power; the laser optical conversion efficiency was 6.7%, while the conversion of the available infrared power reached 50%.

A diode radial pumped microchip Yb:YAG laser that consists of a Yb-doped core surrounded by undoped YAG of slab shape is presented. Quasi-continuous wave pumping of an 800-μm thick 10-at.% Yb doped core of 2 x 2 mm² square shape with pulses of 5-Hz repetition rate and 2.5% duty cycle delivers 66-W output peak power at 220-W input pump power with 49% slope efficiency. 112-W peak power with 63% slope efficiency and 38% optical-to-optical efficiency, were obtained from a of 1.2 x 1.2 mm² square 15-at.% Yb:YAG core of 800-μm thickness. Continuous-wave operation with up to 90 W were obtained from a 400-μm thick Yb:YAG/YAG structure with a 10-at.% Yb:YAG square core of 2x2-mm² area; the slope efficiency and optical-to-optical efficiency with respect to the pump power were 40% and 28%, respectively. Measurements of the optical phase distortions induced by pumping gives focus shift bellow 0.05 m and shows the absence of astigmatic effects, indicating the axial heat flow in this pumping configuration.

Highly efficient one-micron laser emission in Nd-doped vanadates under direct pumping into the ⁴F_3/2 emitting level is reported. A 1.0-mm-thick, 1.0-at.% Nd:YVO₄ crystal operated with 80% slope efficiency (79% overall optical-to-optical efficiency) under Ti:Sapphire pumping and 75% slope efficiency versus absorbed power under diode laser pumping at 880 nm. Slope efficiency of 80% (overall optical-to-optical efficiency of 77%) under Ti:Sapphire pumping and 66% with respect to the absorbed power under diode laser pumping at 879 nm is obtained from a 3.0-mm-thick, 1.0-at.% Nd:GdVO₄ crystal. These values, which were superior to those obtained by pumping into the ⁴F_5/2 level, were explained consistently by the effect of the quantum defect between the pump and laser radiation, the superposition of pump and laser mode volumes, the pump level efficiency and the residual optical losses.

Chaotic behavior is a common feature of mechanical, electrical, optical or other kind of systems. If a certain device, described by a group of mathematical relations with input and output variables and depending on parameters, is stimulated with a known deterministic signal, then its output can behave randomly in some conditions. If two identical or slightly different systems are interconnected together in such way that the input of the second is fed by the output of the first, then a synchronization effect can occur between the outputs of the two devices. Particularly, in the field of optical communication, a number of systems in which the information signal is send from modulator to demodulator through a chaotic carrier and in the same time masked by it, can be imagined. This paper analyses the potential use of Self Pulsating Laser Diodes (SPLD) in an amplitude modulation scheme able to make a data link with preservation of information secrecy.

Fundamental 1064 nm wavelength radiation of a diode pumped passively Q-switched Nd:YAG microchip laser was frequency doubled by periodically poled (PP) and conventional type II KTP crystals. Second harmonic (SH) conversion efficiency of 60% and 47% has been achieved with PPKTP and KTP crystals, respectively. SH pulse energy of as much as 6 μJ, at 900 Hz repetition rate, has been obtained for 10 μJ pulse energy of the input 1064 nm radiation focused with a waist radius of 25 μm inside the 8 mm long PPKTP crystal. We estimated an effective nonlinear coefficient of 6.9 pm/V and a thermal acceptance FHWM bandwidth of 5.78°C for the PPKTP sample.

New aspects of RCOB structure were obtained from Eu³⁺ absorption/emission spectra in GdCOB and EuCOB host lattices. The spectra of Eu³⁺ in powders and single crystals are comparatively analyzed. The Eu³⁺ spectra show at least three non-equivalent centers whose static spectral characteristics were used to assign structural modes. An explanation of the difference between GdCOB: Eu³⁺ and EuCOB spectra in terms of a disordered occupancy of rare earth and calcium sites is given.

The interpretation of complex Yb³⁺ optical spectra in non-linear gadolinium calcium oxoborate GdCa₄O(BO₃)₃-GdCOB crystals is still contradictory. The electronic structure of two Yb³⁺ centers in GdCOB is analyzed, including a crystal field parametric calculation for the main center. The possible models for vibronics intensities are discussed. The presence of a minor center whose relative intensity is of ~10%, indepenent on Yb³⁺ content, and Gaussian line-shapes are connected to the RCOB crystal disordered structure proposed recently from X-ray data.

A diode end-pumped Nd:YAG laser passively Q-switched by Cr⁴⁺:YAG saturable absorber and intracavity frequency-doubled by a LBO nonlinear crystal is described. Using a linear cavity the maximum average power at 1.06-μm fundamental wavelength was 3.3 W, 22.5 kHz repetition rate and 25.2-ns pulses duration. The maximum peak power was 12 kW for an average power of 1.8 W, laser pulses of 17.5-ns duration and 209.3-μJ energy. Intracavity frequency-doubling employing a V-type laser resonator yielded 532-nm green pulses of 226-μJ energy and 86-ns width at 4.2-kHz rate of repetition. The theoretical calculations based on a model of rate of equations show good agreement with the experiments at both fundamental and second-harmonic wavelengths.

An ophthalmic surgical instrument is presented. It contains a specific Q-switch YAG:Nd laser, an optical stereomicroscope, two red output laser diodes and a digital system for optical processing of the microscope images. As Q-switch, a Cr⁴⁺:YAG crystal is used. It works in monopulse or double pulse regime. Four red spots mark the optical object plane. The laser beam is sent in the central part, between four spots and is focused at 150 microns behind the optical plane to reduce the risk of pitting the lens when performing posterior capsulotomies. In order to obtain eleven different energy levels in the (2÷10)mJ domain, eleven attenuators are used. The laser ophthalmic system must fulfill many precautions. The energy level, the pulse length and the used attenuators must have such values to eliminate every undesired effect in the medical applications. This instrument has an important application in posterior capsulotomies and posterior membranectomies.

The paper presents a modeling of heat generation by non-radiative de-excitation processes in pumped laser materials. This model explains consistently the differences in heat generation in Nd laser materials in presence and in absence of laser emission and its dependence on the emission wavelength, on laser extraction efficiency and on Nd concentration.

Efficient quasi-three-level emission at 946 nm in Nd:YAG requires a proper balance between the laser emission and the reabsorption induced by the residual thermal population of the terminal laser level. The paper shows that the emission properties can be increased by direct 885 nm pumping into the emitting level (slope efficiency in absorbed power equal to 0.68, compared with 0.48 for the traditional pumping at 809 nm) and infers that the reduced pump absorption can be overcome by using laser resonators with multi-pass of pump radiation inside the laser material.

The paper discusses the basic possibilities for enhancement of the output power of the self-frequency-doubling devices based on Nd-activated nonlinear crystals, by acting on the factors that determine the intracavity intensity at the fundamental frequency. It is inferred that a very important factor of improvement is the increase of the quantum defect ratio at the fundamental frequency by pumping directly into the emitting level. The relation between the conditions that enhance the intracavity intensity and the frequency-doubling performances is discussed and verified by the marked enhancement of emission at 530 nm in Nd:GdCa₄O(BO₃)₃ with direct pumping at 887 nm.

Spectroscopic and emission decay investigation on single crystal Nd:YAG (with up to 3at.%Nd) and transparent ceramic (up to 9at.%Nd) samples indicate that the state of Nd ions (the sites occupied by the Nd ions, the crystal field and electron-phonon interactions, energy transfer between the Nd ions) are identical. Coupled with the similarity of the thermo-mechanical properties and with specific features of ceramics, such as a high production yield, possibility to produce very large components with uniform Nd doping up to very high concentrations, reduced production cost, these studies show that the transparent ceramic Nd:YAG can be used for construction of lasers. These conclusions are supported by efficient laser emission data.

The paper discusses the problem of Nd concentration dependence of the emission quantum efficiency in Nd:YAG at low pump intensities, based on a modeling which uses the emission decay data. The measurements on crystalline or ceramic Nd:YAG samples with Nd concentrations up to 9at.%Nd show a marked dependence on concentration, induced by the energy transfer self-quenching. The parameters of ion-ion interactions that determine the transfer are used for an analytical modeling of the concentration dependence of the emission quantum efficiency, which gives a very good description of the experimental data.

A new theoretical model of an undulator for free electron lasers is presented. The current undulator structure is a series of hypocicloidal wires. The magnetic field components for each wire present a 120 degree symmetry (for a model with 3 branches). This new treatment of the problem could be extended to the nonlinear dynamical analysis of the electrons in the studied structure.

The possibility of basic enhancement of the global efficiency of frequency-doubling devices for the one-micron continuous-wave Nd lasers by direct pumping into the emitting level and by the use of concentrated laser materials is discussed. This possibility is demonstrated for 1.0 and 2.4-at.% Nd:YAG crystals pumped by a Ti:Sapphire laser at 885 nm. A slope efficiency of 0.79 in absorbed power was obtained for the 1064 nm emission of the 1-at.% Nd:YAG. The effect of enhancement of intracavity emission on the second harmonic emission is manifested in a drastically reduction of emission threshold and in an enhanced dependence on the absorbed power. The use of concentrated Nd:YAG crystals enables a better use of the pump power and increases the overall efficiency of the frequency-doubling devices.

The effect of energy transfer on the VUV-to-VIS quantum cutting in Praseodymium-activated phosphors for Xe dimer luminescence lamps is discussed. From the modeling of emission process in presence of energy transfer it is inferred that the failure to observe efficient energy transfer-assisted quantum cutting in these phosphors is caused by the low efficiency of transfer with respect to the radiative de-excitation of the metastable VUV state ¹S_o of Pr at the low Pr concentrations specific to these systems.

Mathematical modeling is used to estimate the characteristics of the upconversion-pumped Er:YAG laser emitting in green function of the erbium concentration, reflectivity of the coupling mirror and co-doping. Besides the excited-state absorption, cooperative upconversion processes as well as cross-relaxation are included in our model. The main drawback of the Er:YAG system is the presence of a parasitic absorption at the emission wavelength, originating from the ⁴I_13/2 level. The results of our simulations suggest that the highest efficiency could be obtained for an erbium concentration of 5 at.% and a reflectivity of the coupling mirror 0.94. Tentative reducing the population of the ⁴I_13/2 level by co-doping would have a weak but negative influence.

The development of masers in the 1950's made possible amplifiers that were much quieter than other contemporary amplifiers. An analysis of narrow-band yields a fundamental theorem (Caves theorem) for phase-insensitive linear amplifiers; it requires that such an amplifier, will add noise as large as half-quantum of zero-point fluctuations. For phase-sensitive linear amplifiers the theorem establish a lower limit on the product of the noises added to the two phases. In the last decade it was shown theoretically that solid-state masers without inversion may be obtained in multilevel spin systems in dilute paramagnetic solids at high temperature subjected to several strong fields. In the present paper the author applies the Caves theorem to the maser without inversion in order to find out the best ways in which the proposed device can work.

Considering the rise time (understanding the rise speed as well) of the electrical intensity of the pumping pulse as the key parameter characterizing the output power of a copper-type laser, we present here a simplified model of the main kinetic processes occuring during the electrical pumping pulse and afterglow in a Ne-CuBr laser. The a priori knowledge of the typical temporal behavior of the electron density and electron temperature reduces the number of coupled differential equation to be solved. The importance of the parasitic radiative filling of the lower laser levels 2D via channels that are not involving the upper laser levels 2P is enhanced. The comparative green-yellow lasing efficiencies and the temporal timing of the optical pulses with respect to the excitation pulse are consistent with the experiments.

Oxide films grow in atmosphere as a result of oxidation reaction and mass transport of the element through the oxide film. In most III-V compounds (as GaAs) semiconductor oxides of III-element and V-element are formed individually. The AlGaAs/GaAs laser diodes were exposed to facet oxidation at mirror surfaces in normal environmental conditions for a storage process. It was observed a decrease of optical output power in the early stage of experiment together with a constancy of the ratio P/P(O) for the long time term (month). We suggest the development at the mirror laser facet of a natural oxide film as Ga₂O₃ and GaAsO. We present a SEM (Scanning Electron Microscopy) image of a natural oxide film grown in atmosphere at the surface of AlGaAs as laser facet, as well as a picture of a facet oxidation of a laser device. The EDS (Electron Dispersion Spectrum) of a natural oxide put into evidence the O (Kα) signal. Dielectric coating using Al2O3 and a-Si layers protected a part of laser devices, and at the mirror surface a reflectivity of 70% in the emission range of the laser (890 nm) was measured. The emitted power for dielectric coated devices was constant, so the rapid degradation process was slowed down.

Based on the rate equations model, a numerical analysis of an amplitude modulated laser diode is performed. The results both theoretical and numerical, are important in biostimulating experiments we perform in two medical clinics, where stable modulated beams are required.

The paper describes the specific quasi-optical phenomena involved in the generation of the high coherent celestial and biological radiation. It examines the generation mechanism of the high coherent radiation in the living systems in the presence of the ambient celestial primordial isotropic background. Josephson and Kerr mechanisms provide an explanation of the concept of bio-coherence as a novel possibility of electromagnetic communication.

Strontium lanthanum aluminates crystals (ASL) doped with Nd³⁺ with formula Sr_1-xNd_yLa_x-yMg_xAl_12-xO₁₉ are interesting crystals for lasers operating in i.r. (~900 nm range) or blue spectral ranges. This paper uses high-resolution spectroscopy, at low temperatures, for investigation of the influence of composition and Nd³⁺ doping of ASL crystals on emission properties. Preliminary spectral characteristics of two non-equivalent centers were determined. From these data and their dependence on composition, structural models for the two centers are proposed.

TiO₂ nano powder was prepared by laser pyrolysis of gas phase reactants. TiCl₄ (vapor) was used as titanium precursor. The crystalline structures and morphologies of the powder have been analyzed by transmission electron microscopy (TEM), selected area electron diffraction (SAD) and Raman spectrometry. The different characterization techniques suggest that a nano-crystalline mixture of anatase and rutile is obtained.

Laser pyrolysis of a hydrocarbon-based mixture is a continuous method for the synthesis of soot-containing fullerene. In this synthesis process, the mechanism of fullerene formation and soot is the radical mechanism of the PAH formation. In the flames producing both fullerenes and soot, exactly forming carbon cages require particular types of reaction sequences. The fullerene concentrations are strongly correlated with those of PAHs in the flame. The equilibrium soot-PAHs-fullerene is dependent on experimental parameters. FTIR spectra of soot extracts and exhaust gases are discussed in the frame of this dependence.

A study of the effect of polyaniline doping (with HCl) on the DC and AC conductivity of polyaniline is reported. Additional ESR studies are reported. It is concluded that the charge tansfer in pristine and doped polyaniline occurs through one-dimensional variable large hopping, that the charge transport is dominated by polarons. The presence of high spin bipolarons is ruled out by ESR data.

We report the effect of sintering time on thermal diffusivity of BSCCO (Bi-Pb-Sr-Ca-Cu-O) superconductors doped with Sm with different concentration. The superconductor samples were sintered for 24, 48 and 100 hours respectively at 850 Celsius. Thermal diffusivity measurement was carried out at 80 - 300 K by using photoflash technique. The sintering time was found indirectly affect the thermal diffusivity in the way it influenced the grain size and grain alignment.

Multi-pulse Nd:YAG (λ = 1.064 μm, τ ~ 100-300 ns, ν = 1-30 kHz laser irradiation of titanium at low intensities, below or in some cases just above the single-pulse melting threshold of titanium led to the development of a large variety of surface structures. The morphology evolution was strongly influenced by the number of the subsequent laser pulses as well as the ambient gas. In air the formation of crown-, or dome-shaped micro-structures was evidenced. In vacuum the micro-relief is characterized by smooth polyhedral structures developing in the surface plane. In nitrogen the cumulative laser irradiation induced the growth of uniformly distributed micro-column arrays with a high aspect ratio, protruding above the non-irradiated target surface. Morphological, structural and chemical characterizations of the laser treated surface areas were performed by scanning electron microscopy, X-ray diffractometry, Raman spectroscopy, and wavelength dispersive X-ray spectroscopy. The growth mechanisms which lead to the formation of the specific structures are investigated. Moreover, the potential applications of the laser processed surfaces are discussed.

Hydroxylapatite layers were grown by pulsed laser deposition on a titanium nitride buffer deposited on silicon or a titanium alloy. Usually the layers are deposited in the presence of water vapors or in oxygen with partial pressures of several mbar. In this study depositions were carried out in vacuum of about 10^-5 Torr in order to preserve the memory of the physicochemical state of the expelled material from the target under laser beam impact. This enabled us to study the morphology, the structure and the composition of deposited material by various investigation techniques (XRD, TEM, XPS, SEM). We observed that the deposition is made essentially of hydroxylapatite that have two well-known morphologies: (1) an homogeneous film made of grains of nanometric size without chemical interaction between them and which form a not very dense film; (2) particulates (droplets) where are ejected in solid, pasty or liquid state, accredited by characteristic morphologies and which have complex structures whose origins are the physicochemical transformation and decomposition of hydroxyplapatite during laser beam-target interaction. The physical conditions to obtain a continuous and dense hydroxylapatite film are discussed.

Nanometer-sized calcium titanate (CaTiO₃) particles were synthesized by the modified sol-gel method, from Ca(CH3COO)2 and Ti(C4H90) an ideal cation stoichiometry for CaTiO4 perovskite. EDTA was used like chelating agent. XRD analysis for their crystal structure and TEM for their texture characterized the materials obtained after heating in the range 600 - 10000C. The TEM photographs reveal nanoparticles in the size range 50 - 45 nm with a mean diameter found at 120 nm.

A compact pulsed electron beam source based on a channel-spark discharge was studied with the aim to find the optimum operating conditions for an efficient ablation of ferroelectric materials for thin-film deposition. The ablation plasma was studied by time-resolved optical emission spectroscopy. The temporal evolution of the spectral lines of target material and working gas was monitored. In the present discharge configuration a long lasting plasma is characteristic, as proved by the temporal evolution of excited atoms and ions.

AlN thin films with thickness in the nanometer range were prepared by Pulsed Laser Deposition technique. The extension of PLD/RPLD for obtaining good AlN nanostructures is a consequence of high reproducibility, control of the film growth rate and stoichiometry, and low impurity contamination. We investigated in this paper the effect of laser wavelength, pulse duration, and ambient gas pressure on the composition and morphology of the deposited films. We demonstrate that we deposited stoichiometric and even textured AlN thin films by PLD from AlN targets using 3 laser sources generating pulses of 34 ns@248 nm (source A), 450 fs@248 nm (source B), and 50 fs@800 nm (source C). Plamsa investigations by Optical Emission Spectroscopy and Time-of-Flight Mass Spectrometry are in agreement with the studies of films, showing plasma richer in Al ions for source A, and the prevalent presence of AlN positive ions in the plasma generated under the action of sources B and C.

Soots obtained by laser pyrolysis of different gaseous/vapor hydrocarbons were investigated. The morphology variation of carbon soot versus process parameters and nature of reactants was analyzed and discussed. The role of oxygen is essential in obtaining soot particles having considerable curved-layer content.

A novel three-dimensional model has been proposed for simulating pulsed laser ablation plume behvior and 'micron-sized particles' movement. It describes the plume expansion in vacuum or into an environmental gas. The model combined the advantages of Monte-Carlo and Finite Element methods, being able to give a detailed image of particles behavior, both from microscopic and macroscopic points of view. The particle interaction with obstacles is aimed to provide us a more comprehensive understanding of Pulsed Laser Deposition (PLD) techniques, with the final objective of obtaining droplets-free surfaces.

Dielectric and especially ferroelectric materials can be used in many applications such as dynamic random access memories and infrared sensors. The dielectric properties of such materials have to be improved. For this purpose several compositions in the BaO-B₂O₃-TiO₂ system have been studied. The investigated composition was BaTiO₃ with a different amount of B₂0₃ in the range 25 - 50 mol%. Depending on the B₂O₃ amount the melting temperatures of the investigated glasses were in the range 1100 - 1250°C. The vitreous materials have been submitted to thermal treatment in order to obtain surface and bulk crystallization. The Differential Thermal Analyses (DTA) showed out the tendency of crystallization for these samples in the 600 - 800°C-temperature range. For structural analyses there have been used the X-ray diffractometry. DTA analyses, electronic microscopy and atomic force microscopy on samples crystallized by controlled thermal treatments.

Atomic data are needed for the quantitative interpretation of experimental spectroscopic data in laser ablation devices. They include cross sections and rate coefficients for various processes such as ionization, excitation, recombination, charge exchange, and also transition probabilities for line emission. This work presents results on electron impact excitation and ionization per photon coefficients as related to the interpretation of plume emissions accompanying 248 nm laser ablation of graphite in vacuum. We used the Atomic Data and Analysis Structure (ADAS) computer package and the generalized collisional-radiative model to simulate experimental line brightness and emissivities from plasma.

The half-metallic ferromagnetic chromium dioxide (T_c = 390 K) is a prospective material for spintronics applications. We employed pulsed laser deposition (PLD) to grow thin films of various chromium oxides. The experiments have been carried out in oxygen at different dynamical pressures, using a KrF* laser source (λ = 248 nm, τ_FWHM ≥ 30 ns), various chromium oxide targets, such as CrO₃, Cr₈O₂₁ (the latter ones both pure and doped with Y and Sb respectively, for stabilization purposes) and sapphire substrates (c-cut). We optimized the laser fluence. To avoid CrO₂ reduction to Cr₂O₃ in very thin films when kept in atmospheric air, we applied a protection with gold. X-ray diffraction, electron microscopy and Raman spectroscopy evidence uniform films containing CrO₂.

A numerical model of the heat conduction and laser beam deflection in a fluid heated by a thin, cylindrical resistance wire is presented. The model, developd using combined finite difference method technique is used to determine the temperature distribution in a test fluid sample and the heating wire. A probe laser beam passing through the sample is deflected by the refractive index gradient caused by the temperature gradient. The transient probe beam deflection can be recorded using a position sensitive detector. Simultaneous determination of the thermal diffusivity and thermal conductivity of the test fluid is possible by comparing the theoretical results of the probe beam deflection and the experimentally measured deflection.

The effects of several deposition parameters on the quality of deposited boron nitride (BN) films by pulsed laser deposition (PLD) with short laser pulses are studied. The laser fluence, nitrogen background pressure, Si(100) substrate temperature and laser wavelength were varied in order to find the maximum content of the cubic phase in our BN films. We found that laser fluence and wavelength are affecting strongly the structure of BN films while background pressure and substrate temperature are affecting slightly the film morphology.

NSF using gaseous polarized ³He became a popular tool for many polarized neutron scattering applications due to the number of advantages that this technique presents, but also due to significant increasing of technical performancies demonstrated in that field in the last years. The realization of flexible and reliable devices for neutron beam polarization is a focal point in the instrumental development program at the Hahn-Meitner Institute Berlin (HMI). The technique applied in our case to obtain nuclear-spin-polarized ³He is metastability-exchange optical pumping (MEOP) using a cw Nd:LNA laser with 5.8 W output power and 2.5 GHz bandwidth. The general aspects regarding optical pumping in optical polarizing cells are described. The construction of the optical pumping volume is presented, the last results regarding optical pumping cells (OPC) and filter cells preparation are discussed. The status and perspectives of the project are presented.

The paper presents the experimental results on adsorption properties of carbon nanopowders which have been obtained by laser pyrolysis of hydrocarbon-based mixtures. We have investigated the adsorption of benzene, n-hexane and ciclohexane. The influence of the nanocarbon morphology (which depends on gaseous precursors and synthesis conditions) on adsorption characteristics is reported.

Femtosecond laser ablation of Ti, Zr and Hf has been investigated by means of in-situ plasma diagnostics. Fast plasma imaging with the aid of an intensified charged coupled device (ICCD) camera was used to characterize the plasma plume expansion on a nanosecond time scale. Time- and space-resolved optical emission spectroscopy was employed to perform time-of-flight measurements of ions and neutral atoms. It is shown that two plasma components with different expansion velocities are generated by the ultra-short laser ablation process. The expansion behavior of these two components has been analyzed as a function of laser fluence and target material. The results are discussed in terms of mechanisms responsible for ultra-short laser ablation.

The interest to use laser surface processing in microtechnology as a friendly method from the technologic and environmental point of view lead our studies about laser radiation interaction with photo-resist and metallic thin films. In this view we have tried in our experiments to process metallic thin films deposited on silicon substrate by using laser radiation. To obtain a good quality of the metallic thin film removal from the silicon surface a careful selection of the incident laser intensity, number of pulses and irradiation geometry is needed. The threshold value for the laser cleaning intensity depends on the number of incident laser pulses. A careful experimental estimation of the cleaning conditions from the point of view of incident laser energy, fluence, intensity and irradiation geometry was realized for aluminum, copper, and chromium thin films.

The present study refers to an application of optical techniques in restoration of icons. These are, technically speaking, paintings on wood panel using pigments mixed with egg yolk. Making a section through the layers that compose an icon, they appear in the following order: a support made of wood panel; a preparation made from a mixture of an organic glue and a substance for volume (most frequently used are CaSO₄ or CaCO₃ in natural spread forms of crystallization; a layer of paint and gold or silver sheets and the final almost transparent layer which consists in a natural resin also known as varnish. During the classic intervention, the specialist is assisted by modern optoelectronic devices. The cleaning process is based on the laser beam next to conventional methods. Cleaning with solvents or with scalpeds is less accurate than cleaning with laser and the precision of the later method is requested in fine art restoration.

In this paper we present the first results obtained at the ENEA Research Center of Frascati in the diagnosis of stone samples by laser induced fluorescence. The characteristics of the fluorescence spectra (intensity, shape, bands) were both analyzed in coincidence with the laser excitation and up to the fluorescence decay. Two kinds of stones were examined: marble and tuff. In particular, we focused our interest in the different response to the light excitation of the clean and dirty parts of marble. Moreover, a first attempt to detect stone surfaces under water has been carried out. Complementary information has been obtained with measurements of spectral reflectance.

This paper analyses the objective functions that define the dimensional parameters in case of laser drilling. Using the STATGRAPHICS program, the regression polynoms that define the objective function have been established.

In this paper, we report some experimental results concerning new aspects in laser ablation process of the YBCO thin film. Both structural and superconducting properties of the studied films were analyzed by transmission electron microscopy, selected area electron diffraction, elastic recoil detection analysis, Raman spectra, atomic force microscopy images and the ac magnetic susceptibility. We have obtained the epitaxial films with relative large area of c-axis grown film and high critical temperature, without any post ablation annealing process.

The plasma generated by ablation of hydroxyapatite Ca₁₀(PO₄)₆(OH)₂ with ultrashort laser pulses was studied in order to get a deeper insight in the fundamental mechanisms of the interaction of femtosecond laser pulses with the biocompatible target material. First, the propagation of the luminous plasma plume was observed using a fast ICCD camera while time- and space-resolved emission spectroscopy was employed to measure the plasma composition and its evolution as a function of time and space. It is shown that the kinetic energies of ablated atoms and ions are one order of magnitude smaller than those generated by hydroxypatite nanosecond laser ablation. Rather low temperatures of about 3500 and 2500 K are deduced from the relative intensity of spectral lines.

We designed a computer program to investigate laser action upon materials. Basically, this program investigates temperature shape in target under the influence of laser absorption and evaporation. A numerical model for simulating laser-target interaction has been developed. The phenomena occurring in the target are analyzed by solving one-dimensional heat conduction equation under the condition of normal vaporization. We analyzed with this program the interaction between UV laser with fluence 5J/cm² and a titanium target. We took into consideration the actual time shape of laser pulse. Results are in reasonable agreement with the experimental determination.

We have investigated thin films of Ni, Pt, Pd, Ni-Pt and Ni-Pd deposited by pulsed laser ablation. Our study was focused on the correlation of layer morphology and composition vs. synthesis parameters (material, laser fluence and wavelength). In order to obtain bimetallic films we alternatively irradiated two different metal targets. A Nd:YAG laser (λ = 355 and 532 nm, 5 ns pulse duration, fluence 15 - 30 J/cm²) was used. Film analysis was made by AFM and RBS. The synthesized layers had a roughness (Ra) between 15 and 40 nm for Pt and Pd and between 80 and 120 nm for Ni. The rate deposition was in the range of 0.04 - 0.8 Å. In the composite layers, in condition of equally radiated targets, the Ni/Pd at. concentration was 50/50%, while for the Ni/Pt layer was 30/70%.

LiNbO₃ thin films were grown on (100) MgO substrates by pulsed KrF* (λ = 248 nm, τ_FWHM~20 ns, ν = 1 Hz) laser ablation of Li-rich ceramic targets in low pressure oxygen atmosphere. The substrates were heated during the thin film deposition process at 550°C. The as-grown thin films were submitted to a heat treatment in oxygen atmosphere. Moreover, after analyses the films were annealed for the second time, for 2 hours in air at atmospheric pressure. We studied the effect of ambient gas pressure and heat treatments on the stoichiometry, structure and optical properties of the deposited films. The composition and crystalline state of the deposited films were investigated by X-ray diffraction (XRD), Rutherford backscattering spectroscopy (RBS) and nuclear reaction analyses (NRA).

In this paper we extend a thermal model of the laser interaction with solids. The previous model [Appl. Phys. B 71, 523-531, (2000)] takes into account Gaussian laser beams and calculate the temperatures only at the center and at the corner of the input face. In the present paper we extent the model for three dimensional temperature profiles and take into account an explicit surface absorption. We will apply the model at CO₂ laser interaction with optical components (ZnSe).

A pulsed laser has been used to generate a laser plasma plume (a dusty plasma) from a pressed powder target situated in the room atmosphere. This dusty plasma has been analyzed with a probe laser beam, a polarizing interferometer and a CCD camera. Our results show that this dusty plasma is a depolarizing medium. The maximum depolarization degree of the probe laser beam is 5%.

We present a short overview on the application of fractional cyclic and linear canonical transformations to optical signal processing and dedicate some of the discussions to the particular features found in the fractional Fourier transform domain.

In the foreseeable future silicon based electronics will reach limits in miniaturization and switching speeds, imposed by fundamental physical constraints. The quest for smaller gates and higher processing speeds with the attendant increase of chip functional density will reach the point where quantum effects dominate. Alternative strategies will then be required to overcome the limitations of silicon; among the most promising are those exploiting the properties of biological molecules, notably microtubules. These have the advantages associated with carbon chemistry, including the scope for constructing large highly complex macromolecular assemblies, and share the exciting electronic properties of semi- and superconductors. Biological systems have the potential to bypass the limiting effects of single particle quantum systems through the interactions of complex molecules, necessarily based on hydrocarbon polymers.

In this work the theoretical study of pulse string construction of holographic gratings in photopolymeric materials with light-induced optical attenuation has been carried out. The analytical model describing a spatial-temporal transformation of holographic grating field during construction process is developed. The model has a view of recurrence relation and takes into consideration light-induced changing of optical attenutation and diffusion processes. The results of numerical simulation on the base of the model are presented and include analysis of record stage, self-amplification stage and whole pulse string construction. The behavior of spatial profile and diffraction characteristics of constructed gratings are estimated with the help of numerical simulation. For calculation of selective properties we used perturbation technique.

Electron-beam and holographic recording of diffraction gratings was processed in the layers of poly-N-poxypropylcarbazole (PEPC) and co-polymers of carbazolylalkylmethacrylate with octylmethacrylate (CAM:OMA) containing additions of CHI₃. The dependence of the diffraction efficiency of planar gratings on the recording current was studied. The influence of post-effect and storage in the dark on the diffraction efficiency is considered. By chemical development technique the reflecting relief diffraction gratings are obtained with the diffraction efficiency of 25-30%.

Future photonic networks will perform routing and switching in the optical layer by use of ultrafast photonic processing. An ultra-wideband hierarchical hybrid optical time division multiplexing/wavelength division multiplexing (OTDM/WDM) network is proposed for the future core photonic network. As its enabling technologies, continuous C- and L-wavelength-band signal generation, OTDM-WDM multiplexing format conversions, and OTDM wavelength-band conversions are demonstrated.

A new topic in both theoretical and experimental studies of optical solitons is provided by the possibility of existence of spatiotemporal optical solitons (sometimes called "light bullets" or "superspikes"), which are completely localized pulses of light. These fully localized spatiotemporal physical objects result from the simultaneous balance of diffraction and dispersion by nonlinear phase modulation. They hold promise for potential applications in ultrafast all-optical processing devices, where each spatiotemporal soliton may represent an elementary bit of information, provided that stable "light bullets" can be formed from pulss at reasonable energy levels in available optical materials. A brief up-to-date survey of recent theoretical and experimental studies in the field of spatiotemporal solitons in optical media is given.

In this paper, we demonstrate a (3D) analytical solution of stimulated Brillouin scattering (SBS) for high reflectivity and fidelity phase conjugation mirrors (PCM). The results are checked with experimental ones, which were obtained with CS₂ and optical fibers as nonlinear materials and high PCM reflectivities are found out. Furthermore, analytical SBS reflectivity for pumping with Gauss-Laguerre modes is demonstrated and shown to suppress high modes, when using SBS mirrors. These findings are used in some all solid-state laser (SSL) systems with SBS-PCM in order to obtain near Gaussian beams, depolarization compensation and high brightness.

We discuss the merits of low coherence interferometry to investigate the Faraday effect in a diluted magnetic semiconductor (DMS) crystal placed in one of the interferometer arm. We describe the combination of modulation effects due to the Farady effect in the DMS probe with the modulation due to a vibrating mirror in the interferometer. Essential for the measurement of the Verdet constant is the control of polarization in the two arms of the interferometer. We show that by watching the resulting spectra of the photodetected signal, clear distinction is possible between the circular and linear polarization of the input light.

We found out analytical solutions of the propagation equations in photorefractive crystals with nonlinear birefringence, large optical activity and absorption, which show the occurrence of spatial solitons, in the usual orientations with respect to the external electric field. Here, we calculate the Stokes parameters of these solitons and we show their polarization evolutions on the Poincare sphere, in function of the crystal orientation, propagation distance, the soliton-background-intensity-ratio and the external electric field. The experimental polarization states correspond well to our analytical results and numerical simulations. These results are useful for selection of optimum parameters in spatial soliton generation and for future applications in optical switching, routing and storage.

Our fluorescence study gave information on the presence of chemical defects and irregularities in crystal structure, offering a good tool for quality evaluation of organic crystalline materials. We have analyzed the correlation between the bulk or thin film samples' quality determined by experimental parameters (thermal gradient, moving speed of the growth interface, crucible configuration, slow or fast solidification rates) and the fluorescence characteristics for pure meta-dinitrobenzene and meta-dinitrobenzene doped with 8 hydroxyquinoline or 1.3 dihydroxybenzene. The comparative study of the position and shape of the fluorescence emissions for pure and controlled doped materials gave us information on the chemical defects.

In this work a preliminary study of the influence of light illumination on the optical constants of chalcogenide thin films with non-stoichiometric Ge₁₉Sb₁Te₈₀ composition is presented. Films of Ge₁₉Sb₁Te₈₀ with a thickness of ~1 μm were deposited onto glass substrates by vacuum thermal evaporation of parent glasses. The as-deposited films were exposed to light by using a 500 W HBO mercury lamp. The optical constants of the films, before and after their illumination, were evaluated from the ellipsometric measurements in the spectral range of 300 - 820 nm. It has been established that illumination of the films leads to a decrease of the refractive index in the studied spectral region, while a slight increase of the extinction coefficient in the 600 - 800 nm range is observed. For the given film composition the optical bandgap energy of 0.76 eV reduces to 0.62 eV. The film structure shows a very slow recovery expresed in the increase of bandgap energy towards its initial value. The observed decrease of the bandgap energy after illumination is indicative that the film structure undergoes rearrangements upon exposure to light leading to the effect of photodarkening.

The polymer layers from carbazolylmethacrylates (CAM) with oktylmethacrylates (OMA) were prepared and investigated by us. The investigation of mechanical properties of such materials are extremely important, whatever the successful application might be. Load and depth sensing indentation with a Berkovich indenter were performed in order to evaluate the mechanical properties of polymer films. The effective elastic modulus and the hardness were determined on the basis of load-displacement data. The reliability of the chosen analytical method was checked using of number of repeats. The influence of chemical composition, action of UF-light and aging on the mechanical properties of CAM:OMA polymer materials was investigated.

We investigate polarization and intensity all-optical bi- and tri-stability in interference structures that include both a birefringent LiNbO₃ layer of different crystallographic orientations and an absorbing layer. The origin of this multistability is the thermo-optical nonlinearity present in the structures. Regenerative pulsations are demonstrated using the electro-optical and the photorefractive properties of the LiNbO₃ crystal. The unstable dynamical behavior is explained heuristically as being due to competing nonlinearities.

In this paper we study the predictability of the ideal four-level laser for different pump modulation frequencies. Time series obtained from the well-known two ODE system are processed using the Grassberger-Procaccia algorithm in order to estimate the correlation dimension and the errror-doubling time (computed via the Kolmogorov entropy). Results evidence windows of low predictability, which can be associated with chaotic behavior. The attractor dimension, approximated by the correlation dimension, varies between 1.61 and 2.56 for different pump modulation frequencies. However, these values were obtained in a somehow indefinite or indeterminate way. Supported by the large discrepancies in the results reported when chaotic dynamics is analyzed in other areas of physics (e.g. atmospheric physics), the rather vague character of the criteria used when setting some parameters on which the above-mentioned quantities crucially depend is emphasized.

In the last years the Er-doped LiNbO optical waveguides are widely used for the fabrication of integrated optical components. We report some original results concerning the evaluation of the spectral optical gain, spectral noise figure and spectral signal-to-noise ratio in the bent Er-doped LiNbO waveguide of the Mach-Zehnder interferometer pumped near 1484 nm using erfc, Gaussian and constant profile of the Er ions in LiNbO crystal. Our model is based on a quasi-two-level system and the small gain approximation in the unsaturated regime in order to simulate the optical amplification in Er-doped LiNbO straight and bent waveguide amplifiers and we demonstrated that rather high gains (~1.5 dB), low noise figures (~3.5 dB) and good signal-to-noise ratios (~56.5) at the end of the bent arm of the integrated Mach-Zehnder interferometer are achievable for 70 mW input pump power. The obtained results can be used for the design of the integrated optical circuits, Mach-Zehnder interferometers which can be utilized for example for the precise measurement of the displacements, seismic motions, etc.

The relationship, expressing the particle number parameter of a confined quantum system (for instance an ideal bosonic or fermionic gas) in terms of the chemical potential, may be considered as an integral equation for determining the fugacity. Fugacity is obtained as infinte series in the increasing powers of the particle number, which is strongly convergent for the entire range of the thermodynamic parameters, including the region of the so called Bose-Einstein condensation. The asymptotic behavior of the expansion coefficients for increasing ordering number is studied and a simple rule for it is discovered.

The results obtained using Z-Scan methods (transmission -- TZ-Scan and multiple-pass -- MZ-Scan) for the characterization of the partial transparent nonlinear optical materials (NOM) are presented. For a typical NOM, a monocrystalline Si wafer with thickness 0.4 mm, at λ = 1060 nm, the nonlinear bulk effects are dominant in comparison with the nonlinear effects produced by the entrance interface (due to the sufficient large transmission of Si). In this case, the MZ-Scan at low laser intensity (several MW/cm²) can be analyzed similarly to the TZ-Scan, considering the multiple passes inside the sample and linear Fresnel reflections on both sample faces. Due to these multiple passes inside the sample, the sensitivity of the method is increased. The nonlinear optical susceptibility experimentally determined by multiple-pass Z-Scan is in agreement with a theoretical estimation of this parameter, with the results of other treatments of MZ-Scan and TZ-Scan and with its values obtained by two and four-wave mixing.

The main goal of this paper is the study of the stimulated Brillouin scattering (SBS) in multimode fibers, at 1550 nm wavelength, cw operation, in order to build high power IR fiber lasers. Two theoretical models are considered, the usual plane wave model and a modal model, developed in this paper. The theoretical results for SBS threshold and SBS reflectivity are compared with the experimentally determined values. Good agreement was obtained when using the mode structure analysis.

We demonstrated that a synthesized light source (SLS) consisting of two low coherence light sources is capable of enhancing spatial resolution in optical coherence tomography (OCT). The axial resolution of OCT is given by the half of coherence length of the light source. We fabricated an SLS with a coherence length of 2.3 μm and the side lobe intensity of 29% under the intensity ratio of LED 1: LED 2 = 1: 0.4 by combining two light sources, LED 1 with a central wavelength of 700 nm and spectral bandwidth of 100 nm, and LED 2 of 898 nm and 85 nm. The coherence length of 2.3 μm is 56% of the shorter coherence length in two LED's, therefore the axial resolution is 1.2 μm.

Among other carbonaceous species, polycyclic aromatic hydrocarbons (PAHs) are of relevance for astrophysics. It is expected that they are present in the interstellar medium and they are considered as possible carriers of the diffuse interstellar bands. To prove this, absorption spectra of PAHs under conditions similar to those met in the interstellar medium should be obtained. We report here the application of cavity ring-down laser absorption spectroscopy to neutral PAHs, namely anthracene and pyrene, cooled in a supersonic jet. The absorption spectra corresponding to the S₁(0) ← S₀(0) transition of anthracene near 361 nm and to the S₂(1,0) ← S₀(0) transitions of pyrene around 321 nm and 316 nm have been studied. The results are similar to the excitation spectra previously reported in the literature.

A new therapy laser device is presented. The device consists of a central unit and different types of laser probes. The laser probe model SL7-650 delivers seven red (650 nm), 5 mW diode lasers convergent beams. The beams converge at about 30 cm in front of the laser probe and the irradiated area might be varied by simple displacement of the laser probe with respect to the target. The laser probe SL1-808 emits single infrared laser beam up to 500 mW. The efficiency of the use of this device in physiotherapy, and rheumatology, has been put into evidence after years of testing. Dermatology and microsurgery are users of infrared powerful laser probes. The device has successfully passed technical and clinical tests in order to be certified. The laser device design and some medical results are given.

This paper presents some experimental results in order to give an interpretation of the action mechanism of laser radiation on biological tissue (especially vegetal tissue). Different types of woody plant tissue (Sequoia sp.) were irradiated with a low power 633 nm He-Ne laser beam. The laser power can be modified. The fresh weight of callus tissue increased about 70% as related to the untreated sample, when the laser's power was 10 mW. We observed that a 5 mW-laser power developed the bud differentiation. But, a significant promotion appeared for a higher laser powers (10 mW). The influence of laser radiation on the callus tissue growth process was detected also by the performing morphological and biochemical analysis.

Besides the biochemical action of methotrexate (MTX) and 5-fluorouracil (FU) their effect in destroying cancer tumours could be enhanced by exposure to light at different doses. Absorption, excitation and emission spectra of 10^-4M - 10^-5M MTX solutions in natural saline and sodium hydroxide at pH = 8.4 were measured, while their exposure to coherent and uncoherent light in the visible and near ultraviolet (UV) spectral ranges was made (Hg lamps and Nitrogen pulsed laser radiation were used). Absorption spectra exhibit spectral bands in the range 200 nm - 450 nm. The 200 - 450 nm excitation spectra were measured with emission centered on 470 nm; MTX fluorescence excitation was measured at 390 nm and the emission was detected between 400 nm and 600 nm showing a maximum at 470 nm. Spectra modifications, nonlinearly depending on exposure time (varying from 1 min to 20 min), evidenced MTX photo-dissociation to the fluorescent compound 2,4 diamino-formylpteridine. In the 5-FU case the absorption spectra exhibit bands between 200 nm and 450 nm. The emission fluorescence spectra were measured between 400 nm and 600 nm, with λ_ex = 350 nm for UV Hg lamp and with λ_ex = 360 nm for laser irradiated samples; at irradiation with N₂ laser emitted radiation the excitation spectra were measured in the range of 200 nm - 400 nm, with λ_em = 440 nm. New vascularity rapid destruction was observed for conjunctive impregnated with 5-FU solution whilst exposed to incoherent UV and visible light.

Elastic backscattering LIDAR represents one of the most promising tools for attaining remotely information about the distribution of aerosols and particulates in the atmosphere, which could lead to a better understanding of climate processes. In this paper we shall examine the uncertainties associated with such measurements and try to determine which of the LIDAR parameters need to be optimized in order to minimize the measurement errors. An optimization method of the operative characteristic associated with the LIDAR signal validation is also proposed.

Change is intrinsic to ecosystems, but is also the essence of instability and the outgrowth of situations that lack sustainability. It must also be recognized that change can be associated with either restoration or degradation. Compressed multiband image data provides increased flexibility and practicality for systematic change detection on a regional basis. Combining such capability with conceptual extensions of spatial pattern analysis represents a methodology for systematically monitoring spatial structure of spectral change across landscapes in order to profile characteristic broad scale regimes of change and to indicate trends in those regimes. Sustainability and ecosystem health are watchwords of contemporary ecosystem management. To solve urgent needs in application of remote sensing data, environmental change must be detected based on monitoring spatial and temporal regimes across landscapes. Environmental landscape level indices are used to examine land cover transitions. Based on classified TM images for North-Western Black Sea, Constantza urban area, Romania, conditional probability matrices of land cover transition are compared to measures of landscape structure. Based on proper algorithms for structural composition modeling were defined landscape elements being estimated the probabilistic behavior of pixels. This approach suggests a means of linking the probabilistic behavior of the fine scale dynamics to the pattern observed at larger spatial scales.

Biometric is automated method of recognizing a person based on physiological or behavior characteristics. Among the features measured are retina scan, voice, and fingerprint. A retina-based biometric involves the analysis of the blood vessels situated at the back of the eye. In this paper we present a method, which uses the fractal analysis to characterize the retina images. The Fractal Dimension (FD) of retina vessels was measured for a number of 20 images and have been obtained different values of FD for each image. This algorithm provides a good accuracy is cheap and easy to implement.

UV-VIS spectra of the CoBr₂ in poly(ethylene glycol) (PEG) are presented and analyzed. PEG 200 and PEG 1000, i.e., two different chain length of the oligomer have been considered. The deconvolution of these spectra was performed to determine the local symmetry, or sub-species, of the complex ions formed in the CoBr₂/PEG systems. We found that the Co-coordination by some of the ligand's atoms of the polymer is dependent on the chain length of the PEG.

Urban area is a mosaic of complex, interacting ecosystems, rich natural resources and socio-economic activity. Dramatic changes in urban's land cover are due to natural and anthropogenic causes. A scientific management system for protection, conservation and restoration must be based on reliable information on bio-geophysical and geomorphologic, dynamics processes, and climatic change effects. Synergetic use of quasi-simultaneously acquired multi-sensor data may therefore allow for a better approach of change detection and environmental impact classification and assessment in urban area. It is difficult to quantify the environmental impacts of human and industrial activities in urban areas. There are often many different indicators than can conflict with each other, frequently important observations are lacking, and potentially valuable information may non-quantitative in nature. Fuzzy set theory offers a modern methodology for dealing with these problems and provides useful approach to difficult classification problems for satellite remote sensing data. This paper describes how fuzzy logic can be applied to analysis of environmental impacts for urban land cover. Based on classified Landsat TM, SPOT images and SAR ERS-1 for Bucharest area, Romania, it was performed a land cover classification and subsequent environmental impact analysis.

The realization of new ultraviolet laser sources and the improvement of existing laser sources require new optical components with more and more severe requirements. Three examples will be considered here: solid-state ultraviolet (UV) laser sources, excimer laser sources and free electron laser (FEL) sources. In the first case, dichroic mirror with high steepness between high reflecting and high transmitting wavelength range are required, to make UV tunable sources. In the second case, the use of graded mirrors in the laser cavity allows an improvement of the laser beam quality. In the third case optical coatings able to withstand the synchrotron radiation are needed. The required performance for optical coatings to be used in this kind of laser sources are described, and critical points underlined.

Rare earth activated phosphors are largely used in optoelectronic devices, X-ray intensifying screens and fluorescent lamps. Luminescent properties (color, efficiency, and decay parameters) and powder characteristics (particle morphology and size, crystalline structure) that are regulated during the synthesis process determine the phosphor utilization potential. Photoluminescence (PL) and cathodoluminescence (CL) investigations are used in order to evaluate the quality of phosphor based on europium and terbium activated calcium tungstate. CL and PL spectra as well as CCL-SEM pictures of some CaWO₄: Eu,Tb samples are discussed in relation with some of their preparation parameters. The mutual interaction of the two activating ions is put in evidence.

In this paper we present a simulation strategy for the accurate prediction of the functionality of an InP based opto-electronic modulator. The device is composed by an InP-InGaAsP p-i-n diode embedded in a rib waveguide and a Mach-Zehnder interferometer. Finite Element Analysis for both semiconductor and optical equations solution is exploited. We present numerical results indicating that with a 2 mm-long device a reverse bias of 11 V is needed for a 180° phase shift.

Spectroscopic diagnostics, using intensified high speed CCD camera, was applied to study the arc dynamics in low voltage circuit breakers, in vacuum and in air. Time-resolved emission spectroscopy of the vacuum arc plasma, generated during electrode separation, provided information about the interruption process. The investigations were focused on the partial unsuccessful interruption around current zero. Absorption spectroscopy, in a peculiar setup, was used in order to determine the metallic atoms densities in the interelectrode space of a low voltage circuit breaker, working in ambient air.

Terbium activated gadolinium oxysulphide phosphor (Gd₂O₂S: Tb) shows bright green luminescence and high efficiency under X-ray excitation. Phosphor utilization depends on powder characteristics and luminescent properties that are regulated during the synthesis stage. The paper prsents some of our results referring to the synthesis of Gd₂O₂S: Tb phosphor by solid state reaction route, from oxide precursors. The influence of flux composition and amount as well as the sulphide supplier concentration on phosphor properties was investigated in order to prepare efficient luminescent powders for the manufacture of X-ray intensifying screens for medical diagnosis.

The paper presents some aspects referring to the synthesis of niobium activated yttrium orthotantalate phosphor (YTaO₄:Nb), utilizable in the manufacture of X-ray intensifying screens for medical diagnosis. The influence of some preparative conditions such as activator concentration and firing regime on the crystalline structure and luminescent characteristics are investigated. Photoluminescence spectroscopy, X-ray diffraction and FT-IR spectroscopy are used to evaluate the material quality.

Our paper provides analytical expressions for the statistical errors related to statistical processing of digitally recorded Newton's rings interference patterns by least squares fitting. These results completes some of our previous papers concerned with Newton's rings fringe patterns processing, which well describe an iterative numerical algorithm that we commonly use for fringe processing.

A grating type interferometer uses a grazing reflection on the testing surface. The grazing reflectance could be very large and the projected roughness height on the incident light directions is small. We built such an interferometer using a diffractive optical element (DOE) realized in National Institute of Microtechnology. We obtain resolvable quality fringes for different materials from industrial quality metal pieces to wood. Contour map of a testing flatness metallic proof is obtained followng a 4 step algorithm: smoothing for both direction of interferogram, skeletonizing interference fringes, computing heights that correspond to the deviation from a plan surface for each fringe point; representing 3D contour lines of equal (400 nm) height.