We have demonstrated InGaAsP/AlGaAs double fused 1.5 micrometers multiple wavelength vertical cavity lasers and arrays in which element definition is obtained by localized fusion. Laser elements emit in continuous wave under electrical and optical pumping. Multiple wavelength single element VCSELs have been fabricated in the same batch taking advantage of layer thickness nonuniformity of InGaAsP/InP material close to the edge of the wafer. To obtain multiple wavelength arrays a controllable cavity length variation using anodic oxidation has been performed. The wavelength span in an 8 by 1 laser array is 10 nm. Single mode operation with more than of 40 dB side mode suppression ratio is characteristic for laser elements in the array.

A new calibration free procedure (CF-LIPS) for quantitative elemental analysis of material, based on laser induced plasma spectroscopy technique, has been developed and patented by the pulsed laser spectroscopy group at IFAM/CNR (Pisa). This procedure allows for fast and reliable quantitative analysis of materials in solid, liquid or gaseous phase. Precision of order of a few parts percent can be obtained, for all the elements in the samples, with typical sensitivities of one part per million or better. Major constituents, trace elements and impurities are all measured in the same run. The two major advantages of the CF-LIPS technique, compared with conventional chemical analysis methods, are the independence on samples pretreatment and calibration curves. The problems related to the so-called 'matrix effect', which produces a lack of linearity in emission spectra, are completely overcame by the application of this standardless analytical procedure, which is based on the measure of the relevant physical quantity characterizing the plasma. These features make CF- LIPS an eligible method for on-line elemental analysis or in field quantitative measurements. In fact, CF-LIPS is the only existing technique which gives precise quantitative results, comparable with laboratory chemical analysis, in real time and in situ. The comparatively low cost of the system, along with its intrinsic speed and ease of use, will probably help, in next few years, a further diffusion of the calibration-free LIPS technique for material analysis, environmental protection and Cultural Heritage conservation and study.

Mixed valence ion doped polymers are potential materials for the real time holography. We review the intimate mechanisms imposing suitable optical properties in Fe:PVA, stressing on the main role played by the Fe ions. Under the UV exposure, both the refractive index and the absorption coefficient are changing due to a local electron transfer from the PVA matrix to the Fe³⁺ ions. The absorption coefficient proved to be dependent on a new-formed low spin Fe²⁺ state whereas the refractive index and the absorption coefficient are changing due to a local electron transfer from the PVA matrix to the Fe³⁺ ions. The absorption coefficient proved to be dependent on a new-formed low spin Fe²⁺ state whereas the refractive index is related to the total content of the high spin Fe²⁺ state. The diffraction efficiency data are explained in terms of the Fe²⁺/Fe³⁺ ratio. Additional data concerning the electron transfer in Sn:PVA thin films are also discussed.

We study the phenomena connected with high concentration of incoming ions emerging during field-assisted migration in otpical glass. We find that ion dynamics are very different at concentrations higher and lower than a certain parameter called the transition concentration. To explain anomalies at high ionic concentrations, we introduce a supplementary local electric field. This field opposes to the field E₀ existing in the glass at all concentrations of incoming ions and is connected with a local space charge. We investigate its dependence on concentration and on E₀. These effects are studied using a model with concentration-dependent diffusion coefficients and mobilities. We present a method to obtain the concentration dependence of the relevant quantities. Theoretical curves are compared with experimental results measured in usual silicate glasses, during Ag⁺-Na⁺ exchanges.

In this paper we present the computed dopant field in the neighborhood of the melt/solid interface in the case of Bridgman-Stockbarger semiconductor crystal growth system in microgravity. The computation is made in quasi-steady state approximation for crystal and melt with thermophysical properties similar to those of gallium-doped germanium, using the 'precrystallization-zone' model. In the quasi- steady state approximation the translation of the ampoule is replaced by supplying melt into the ampoule with velocity V₁ and removing crystal at the other end of the ampoule at the rate V_s equals V₁. The 'precrystallization-zone' is considered to be a thin layer masking the crystal in which exists a periodical microstructure created by the periodical structure of the crystal which governs the arranging of the own atoms into a specific crystalline lattice. In fact, in this layer we have periodically distributed places which are not available for the dopant. Using this approximation and model, we find relevant radial segregation due to the precrystallization-zone. We also find that reducing the diameter of the rod a lower radial segregation appears. Therefore the influence of the precrystallization-zone is relevant even in microgravity and there is no reason to ignore this zone in general.

We obtained polymer dispersed liquid crystal (PDLC) films using a nematic liquid crystal E7 and polymethyl methacrylate by the Solvent Induced Phase Separation method. Using the Thermally Stimulated Depolarization Current method we determined the clearing point of the pure liquid crystal and the PDLC films. The glass transition temperature of the PMMA matrix has also been determined. The result have been compared with those obtained by Differential Scanning Calorimetry. During the TSDC measurements we registered the optical transmission as a function of temperature, thus the thermal switch operation being demonstrated.

Amorphous C-Ni superlattice films designed as normal- incidence reflector for 5 nm have been grown on quartz substrates by magnetron sputter deposition in Air discharge. An extended set of characterization techniques has been applied: Transmission Electron Microscopy (TEM) and Atomic Force Microscopy (AFM) in order to characterize the growth conditions. TEM measurements revealed information about the evolution of smoothness and the uniformity of the multilayer structure function of the distance of the substrate. A new DSP-controlled AFM system has been involved in investigating the surface topography of the final surface of the multilayer structure as well as the substrate. A new DSP- controlled AFM system has been involved in investigating the surface topography of the final surface of the multilayer structure as well as the substrate. A detailed analysis of AFM topographic images is presented. Special attention has been paid to an important parameter for such mirrors, the surface roughness, for nanometric and micrometric ares, invovling AFM tips with different radius of curvature. Roughness analysis as well as the implication of the different radius curvature tips use din AFM-contact experiments are presented together with the power spectral density function calculation.

During the last decade the interest in polymeric material for second-order nonlinear optical properties has been constantly growing. They combine structural electronic properties, with good thermal and mechanical stability, a relatively low cost and easy processability. The second order nonlinear optical (NLO) properties of such materials have electronic origin, with an ultra-fast response time. In the present paper, we report the preparation and characterization of a new material with a higher concentration of a NLO chromophore. We have synthesized a new dye monomer by the phase transfer catalyzed reaction. We have prepared the copolymer with styrene, by bulk copolymerization; the initiator was di-t-butyl peroxide at 120 degrees C. We have characterized the monomer and the copolymer by IR; UV-Vis; H-NMR spectroscopy. The glass transition temperature and the melting point have been obtained using the differential scanning calorimetry. For studying the NLO properties, the samples have been poled by the Corona poling method, in an electric field of approximately 100V/micrometers . We have appreciated the second- order nonlinear coefficient by comparing the light signal passing through the sample, with the signal passing through a standard quartz plate.

It was shown that the acoustic emission (AE) intensity decreases with the increase of the temperature and relaxation of the preliminary deformation of the InP crystals and alternatively sharply enhances with the predeformation degree rise. The results obtained allowed to conclude that the emission process of acoustic waves is tightly related to both the deformation stresses and structure state of defects, characterizing the starting InP crystals before the AE initiation by microindentation.

This paper presents the wet synthesis method of high purity cadmium and zinc sulphides for phosphors. As row materials are used zinc sulphide, cadmium sulphide and cadmium-zinc sulphide in order to obtain a large types of phosphors.

Chemical synthesis by concomitant precipitation of metallic ions for obtaining a PLZT 10/65/35 composition starting from hydroxides and oxalates was made. Another task was the sintering of oxide powders obtained by thermal decomposition of synthesized precipitates using hot pressing method followed of heat treatment in oxygen stream.

Some of the III-V compounds such as InSb, InAs, In As_1-xP_x, have high thermal conductivity very high mobility of electrons and low effective masses. Their figures of merit being high enough they are useful materials. For thermoelectric materials, the high mobility of electronics is a very important factor.

Aluminophosphate glasses doped with rare-earth ions have recently attracted a large interest owing to their relevant non-linear optical properties. Until now, all studies were done over the glasses doped with rare-earth ions, in which the rare-earth ions were into a vitreous silica matrix. Our study was made as for rare-earth ions into a vitreous aluminophosphate matrix. In the first step, the samples of rare-earth doped glasses were obtained by melting the raw materials batch and then by adding rare-earth oxides. In the second step, the resulted glass was annealed. By means of a spectrophotometer, were drawn absorption and transmission spectra, in UV-visible domain. For IR domain we used a SHIMADZU-FTIR-8001PC spectrophotometer.

We present some investigations on the correlation between the crystalline quality controlled by the physical defects induced by the growth conditions and the optical and electrical properties of a benzene disubstituted derivative.

Using a variational procedure, we have calculated the energy levels in a GaAs spherical quantum dot under the action of an external electric field, assuming an infinite confinement potentia. Our results show that the electronic states depend strongly not only the applied electric field, but also on the quantum confinement. Because the field-induced spatial separation of conduction and valence electron is in GaAs quantum dot decreases the overlap between their associated wave functions, in the presence of the electric field it is expected a reduction of the luminescence. We obtained the dependence of the recombination rate between conduction and valence electrons as a function of the applied field for different dot radii. We have found that large polarizations are expected for GaAs quantum dot with a radius R >= 100 angstrom. These aspects must be taken into account in the interpretation of optical phenomena related to shallow impurities in which the effect of an applied electric field competes with the quantum confinement.

Cerium activated strontium-magnesium orthophosphate phosphor exhibits strong UV luminescence whereas cerium-manganese activated phosphor shows pink luminescence. These phosphors could be used for the manufacture of eritemal or copy machine lamps and for fluorescent lamps for luminous signs, respectively. Samples of (Sr_{1- x}Mg_x)₃(PO₄)₂:Ce and (Sr_{1- x}Mg_x)₃(PO₄)₂:Ce, Mn phosphors with variable compositions were synthesized and characterized. Crystalline structure and luminescence properties were determined and discussed in order to establish the optimum synthesis conditions for phosphor preparation.

CdS-CdTe heterojunctions are valuable candidates for photovoltaic conversion of solar energy. In this work, thermal vacuum evaporation has been used to grow CdTe films on glass supported CdS substrate. Cadmium sulphide thin layers have been grown by chemical bath deposition. The influence of different preparation foundations on thin film quality has been studied. The otpical homogeneity and film thickness was used as criteria to select the best substrate for the subsequent CdTe deposition. Some structural and optical characteristics of CdS/glass and CdTe/CdS/glass structures have been determined.

Under short TJV or roentgen radiation, the self-activated calcium tungstate phosphors (CaWO4:W) exhibit blue luminescence and could be used as luminescent pigments for the manufacture of X-ray intensifying screens and fluorescent lamps for luminous signs. As luminescent pigments, CaWO4:W phosphor has to possess high luminescence characteristics and well defined particle sizes. This study presents the influence of synthesis conditions on morphostructural and luminescent characteristics of CaWO4:W phosphors. Phosphors were prepared by thermal synthesis from mixtures consisting of precipitated CaWO4 and CaCl2 as flux; both reagents were luminescent grade. Calcination was performed at 600-1000 °C for 0.5-2.0 h, in air. The crystalline structure (XRD-patterns), particle size distribution and luminescent characteristics (emission and excitation spectra) ofphosphors were determined and interpreted.

Attempts were made to synthesize copper activated zinc sulphide phosphors sensitive to (beta) -radiation. In this purpose, homogeneous synthesis mixtures were prepared from luminescent grade zinc sulphide - thiosulfate route -, copper nitrate and alkaline and/or alkaline-earth chloride and were fired at 800-900 degrees C, in nitrogen atmosphere. ZnS:Cu,Cl phosphors prepared in various synthesis conditions were characterized by crystalline structure, particle size distribution and luminescent properties under UV excitation. Some ZnS:Cu,Cl sample phosphors were used to manufacture radioluminescent sources and their sensitivity of (beta) radiation was estimated. The optimum synthesis conditions were established.

In Pb(Zr_1-x Ti_x)O₃, experiments have shown that conductivity is p-type. The excess of cation over oxygen vacancies causes a superoxidation of many simple oxides, including ZrO₂. These A position vacancies attract electronics to complete the electron shells of surrounding oxygens: they act as acceptors causing the presence of holes in the lattice. The new revised theoretical model presents the basic steps in the solid plasma linear analysis of any acousto-electric problem.

We have investigated the magnetoresistance and structure of binary metallic system formed by Cu and Co. The samples were prepared by electrochemical deposition from a single electrolyte acid solution on copper coated glass substrate. The structure of the alloy films before and after annealing has been determined by X-ray diffraction. Two cubic phase which could not be precise identified. Field dependence of the magnetoresistance were measured for different field orientations. Isotropic negative magnetoresistance effect of 2 percent at room temperature for Cu-Co structures before annealing and of 0.9 percent after annealing was found. The temperature dependence of resistivity was measured.

We have investigated the magnetotransport properties of binary metallic systems formed by Ni-Bi and Cu-Ni multilayers. The samples were prepared by electrochemical deposition. Ni-Bi systems were obtained from two separate solutions and Cu-Ni systems from a single electrolyte. The films have been characterized using spectro-ellipsometry. Field dependence of the Hall resistivity and magnetoresistance for both the multilayer deposited structures were measured. Anisotropic magnetoresistance for Cu-Ni structures was found.

In this paper we discuss the upconversion processes responsible for violet luminescence from the Erbium levels ²P_3/2 and ²H2_9/2 in diluted Er:YAG crystals, excited with pulsed as well with cw lasers. Besides the general need for new spectroscopic data concerning laser materials, the interest for this study is generated by the fact that energy levels of very different quantum efficiencies can produce, function of the pumping conditions, fluorescence spectra of comparable intensities or even with reversed intensity ratio.

We have evaluated the resonant photodetection characteristics of long wavelength double fused InGaAsP/AlGaAs vertical cavity lasers. Using VCSEL structures fabricated by the localized fusion technique for laser generation, light detection is also possible in open circuit, short circuit and forward biased (FB) regimes. The wavelength selectivity of the detection increases with driving current in FB regime. Detection spectrum with FWHM as low as 0.02 nm is demonstrated in the FB regime at currents above threshold. Investigated structures emit and detect light with high spectral selectivity and may be very useful as multifunctional elements for signal generation a d detection in wavelength division multiplexing systems.

This paper describes the construction of high precision towers for support of an optoelectronical detect during fabrication. For fabrication of an optoelectronical detector is necessary a special room with a special environment. After assembling the frame of detector must be in plane, in range of +/- 10 micrometers .

In this paper the authors use the launch model of guided modes on a multimode optical fiber, obtaining with computer help - important numerical results, which refer to efficiency of exciting a desired LP₀₁ mode. All the theoretical considerations are based on the gaussian beam approximation.

In this paper, the authors intend to present and analyze the Gaussian model, frequently used when we want to control the coupling between an optical source and a multimode fiber optic. Based on this mode, is determined the coupling coefficient in case of injecting radiation coming from a coherent source, analyzing the effect of different factors over the efficiency of this coupling.

The experimental results of the power-related frequency shift of an iodine-stabilized He-Ne laser with two methods of power variation: misalignment of the laser cavity and change of the polarization orientation between iodine cell and gain tube are reported. A small-power internal-mirror He-Ne laser PLL offset-locked to an iodine-stabilized He-Ne laser was used as the reference laser. The data were processed following three methods: the standard matrix method, the diagonal method and the reference line method. All three methods gave compatible result, but the diagonal method is taking advantage of collecting fewer data and being faster. Significant differences appeared among values of power-related frequency shifts, if the method of power variation was different, no matter the group of hfs components or method of data processing under consideration. For the same group of hfs components, deviations of less than 1 kHz may exist between frequency shifts computed by using the above mentioned methods of data processing, while the deviations between the frequency shifts calculated at the same power level do not exceed 2 kHz. This is regardless of groups of hfs components. BY contrary, differences up to about 14 kHz for a given group of hfs components were observed if the method used to get the power variation was different.

We propose a simple method for integration by numerical computations of the atomic rate equations for three-level systems and the laser amplifier equations. We calculate the gain coefficient in erbium-doped fiber considering the effects of pump on the system dynamics. Described the atomic rate equations for three-level system and the dynamics Maxwell-Bloch equations for erbium-doped fiber laser amplifier is presented.

The paper discuses the influence of cross-relaxation parameter on the characteristics of the sensitized photon avalanche. A system Pr³⁺ as activator ion and Yb³⁺ as sensitizer ion were considered for the avalanche process. By numerical modelling of a system of rate equations, time dependencies and pump rate dependencies of populations of energy levels were calculated for three different values of cross-relaxation rate. Correlation between cross-relaxation rate and threshold value of pump intensity was established.

This paper present a new computing procedure for measuring the bulk absorption coefficient of the laser optical components that present a layered structure as the coated otpical components. Previously, this measurement has ben conducted usually by laser calorimetry with the procedures provided by ISO 11551. However these methods assume the probes to be homogenous and for the inhomogeneous samples this assumption may introduce significant errors in the value of the absorption coefficient. The method is based upon the general solution of the heat diffusion equation calculated for an optical component irradiated by a laser beam with all parameters known. Because the optical component has a layered structure, in order to obtain the solution of the mentioned equation in each layer, a system of heat equations has to be solved. The solutions of this system correspond to the diffusion in each layer and they strongly depend upon the absorption coefficient of each layer. Due to the fact that the values for absorption coefficient are small for the studied samples, these solutions are developed in Taylor series with respect to the absorption coefficient. This development leads to a set of algebraic equations that provides the absorption coefficient value of each layer if the temperature in one point of that layer is known. This method has been experimentally tested by evaluating the absorption coefficient of a ZnSe sample with an AR coating of BaF₂ and the result proved to be in agreement with the results obtained by numerically simulating this process.

The short presentation of the YAG:Nd laser's parameters is followed by phenomena that take place at the intersection of the laser radiation with the material to be processed. The laser induced temperature distribution, the parameters that condition the laser process use, the factors that influence the precision of the laser operation, and the technological particularities on the puncture, are problems dealt with before the experimental research's results. The abstract presents a method of selective chemical metallizing of the puncture made in ceramics, as well as application areas and advantages of the laser puncture.

Reactive pulsed laser ablation deposition of thin films is a technique which has already given good results for the formation of metal and semiconductor oxide and nitride films. To improve the quality of the deposited films it is important to understand the ablation process and the materials transport phenomena from the target to the collecting substrate. Optical emission spectroscopy of the plasma plume, formed by the interaction of the laser pulse with the target is generally used to try to understand the reaction mechanisms during the transport process. An eight speed camera was also used to determine plasma plume expansion velocity and the total duration of luminous emission of the plume. The effect of ambient pressure in the ablation chamber on the plasma composition was observed.

An analysis of low temperature lineshapes for various absorption lines of several RE³⁺ ions from the beginning Nd³⁺ and end of lanthanide series Er³⁺, Tm³⁺ embedded in the same crystal - YAG known as important laser systems for 1-3 micrometers emission is presented. New aspects of the dependence of electron-phonon coupling on RE³⁺ ions and matrix are observed from the analysis of many transitions of these ions at low temperature. These data show that eh electron-phonon coupling presents a symmetric behavior in the lanthanide series, larger toward beginning and end. With only very few exceptions, less than 2 percent, the broadenings or splittings of zero-phonon liens could be connected to optical Raman phonons of undoped lattice. That means that the parity of 4fⁿ states could still be considered a good parent quantum number, even if the local symmetry has no inversion, and the near resonant coupling involves the even part of the electron-phonon coupling operator. Besides, the one phono relaxation involve the undoped lattice phonons. For ions with small spin-orbit coupling, the vibronic contribution to the line intensity given by ir phonons through a Van Vleck mechanism could be important for spin forbidden transitions.

Based on some experimental measurements performed on Er³⁺-doped Ti:LiNbO₃ optical waveguides, this paper presents some result concerning the evaluation of some nonlinear parameters: third order nonlinearities, the saturation change in refractive index using the low-finesse waveguide Fabry-Perot resonators.

It is analyzed the influence of a longitudinal magnetic field on the operating mode of a He-Ne laser, knowing that the magnetic field is used for the suppressing of the (lambda) 3.39 micrometers , which is amplified in the same time with (lambda) 632.8 nm. It was used the Faraday magneto-optic effect at resonance, so that eh (lambda) 632.8 nm He-Ne laser radiation travels through a Ne-Ne mixture, with the pressures ratio p_He/p_Ne equals 5, in population inversion conditions, placed in a longitudinal magnetic field. It was studied the laser medium amplification coefficient dependence on the parameters: discharge current intensity and total gas pressure. For the relation between the rotation angle of the polarization plane in a magnetic field and the laser amplification coefficient, in the He-Ne mixture, it was found a linear theoretical dependence. By fitting the experimental data, there are obtained nonlinear dependencies, for (alpha) (p) and (alpha) (I), which can be explained in the atomic collisions theory.

The paper presents the possibility of analyzing the electromagnetic field as a constrained dynamical system. The transversality of the electromagnetic waves leads to difficulties in their covariant description. The longitudinal and the temporal components appear as non- physical degrees of freedom. In order to develop a canonical formalism it is necessary to use a phase space extended with ghost type generators. In this space the gauge symmetry of the field can be replaced by a global BRST symmetry. Our construction will correspond to a generalized symmetry that can be split in many pieces. This decomposition could be very useful in the description of multi-interaction processes.

The acoustic transmission line model has been used for a quantitative theoretical description of a resonant photoacoustic (PA) cell excited in its first longitudinal more. Based on this model, the PA cell was divided into a finite number of sequential components represented by analogue electric circuits. Their specific influence to the acoustic behavior of the cell is presented. The parameters of the cell were determined and the result were compared to predictions from classical theory and to the experimental values. In order to obtain an optimum geometry of the cell, the influence of the buffer radius onto the resonance frequency and the quality factor of the photoacoustic cell was studied for a constant value of the buffer length of 75 mm.

In many applications related to the electromagnetic field analysis in a cylindrical coordinates systems (r, z, (xi) ), the following periodic integrals have to be calculated.

A self-heating He-Se laser tube has been developed. It was all Pyrex, 60 cm active length, 2 mm ID. The laser beam consisted of seven green lines 28 mW total power. We have examined, by perturbation spectroscopy, the existence of amplification along the laser tube axis. The experimental set-up consisted of: laser tube, two laser mirrors dielectrically deposited for full reflection on 500 +/- 50 nm spectral region, a grating monochromator 0.2 nm resolution, a chopper, an EMI 9558QB photomultiplier and a lock-in amplifier. The spontaneously emitted light in the perpendicular direction to the tube axis has been monitored. The laser radiation field that exists in the active medium involves the decreasing of the upper laser level population and thus, the intensity of the corresponded spontaneously emitted line decreases too. Using the chopper, the laser beam is periodically interrupted so that, a modulation of the intensities of the spectral lines appears. The signal sign is opposite for amplification and absorption region, placed inside the metal reservoir, just where the metal vapors penetrate the discharge. Taking into account the energies of the involved levels, we have proposed reaction.

A simple method that allows the determination of the rates of the two-ion up-conversion processes governing 3-micrometers laser emission in concentrated erbium systems is presented. The method is based on the analysis of the kinetics of the ⁴I_11/2 level, excited with short 532 nm laser pulses, for various pulse intensities.

Wavelength measurement is a critical topic in many applications. Stationary interferometers, such as Fizeau and Murty, can be successfully used, considering the proportionality between the wavelength and the fringe spacing in the interference pattern.In this work we present a 1D algorithm for the calculation of the fringe spacing and error sources. The final accuracy that can be achieved is also assessed. The experimental data are taken from fringe pattern recorded with a Murty interferometer.

This paper investigates the generation of ultra-short pulses form directly modulated multiple-quantum-well (MQW) laser diodes. The ultra-short pulse generation is stimulated using the rate equations' model. The effects of the input signal parameters on the duration and magnitude of the pulses are examined from simulations. Particular interest is paid to the influence of spontaneous emission factor on the chaotic laser behavior. The study is focused on improving the understanding of how the phenomenological laser parameters influence the nonlinear dynamics and on establishing the connections between the modulation signal parameters and the nonlinear dynamic behavior. The numerical simulations carried out for different laser structures show good agreement with previously reported results and demonstrate period bifurcation and chaos for some ranges of the bias current and modulation index.

This paper presents the efficiency of Smith-Purcell radiation generation for lamellar and triangular metal gratings (MG) in H-polarization. The efficiency was calculated by the modal expansion method for lamellar MG and the improved point matching method for triangular MG, respectively. Most important MG parameters involved in the calculation were: the space period, the total number of grooves, the profile and the shape of the groove, and the geometry of the reflecting surface. Calculations were performed for relativistic electron beams with energies in 1-50 MeV domains. The emission angle of coherent SP radiation depending on MG and REB parameters is also presented.

This paper present the fabrication and mirrors passivation process of InGaAs/AlGaAs/GaAs narrow stripe 980 nm emission wavelength laser diodes. After mesa-stripe definition and Au-contact deposition procedures, a procedure of in-vacuum cleaving and in-situ passivation with (lambda) /2-thick ZnSe layers was performed. 960 micrometers and 500 micrometers length laser diodes bars was fabricated as a result. Antireflection-high reflectivity coating were formed on the bars facets. Laser diodes were soldered p-junction-side down on copper submounts. The room temperature CW threshold current value of 20 mA and CW maximum output power of 440 mW at 760 mA pumping current were obtained. The far-field emission pattern of laser diodes is lateral single mode in large range of output powers. These laser diodes were used for laser diode module fabrication. In this module the laser diodes was coupled with tapered single mode 9 micrometers /125 micrometers optical fiber with a fused microlens at the end. CW output optical power of 40 mW from the fiber was obtained at 240 mA operating current of the laser diode module.

This paper describes the fabrication technique and operating characteristics of cleaved-coupled cavity (C3) tunable source with central emissions wavelength 835 nm and 980 nm. The C3 concept is realized using gain-guided AlGaAs/GaAs single quantum well and ridge-waveguide InGaAs/AlGaAs/GaAs multiquantum well heterostructures. The tunable wavelength range for these devices was 10 nm and 16 nm respectively. The coupled cavity was formed by cleaving the laser diode chips in two parts. The cleaved sections held together by the contact metals, were then indium soldered p-side up to a copper heat sink for CW operation. The sections length of the 980 nm C3 laser was 320 micrometers and 440 micrometers and 240 micrometers , 260 micrometers for 835 nm device. The emission spectra of 835 nm and 980 nm C3 laser diodes are presented.

We propose a rigorous theoretical simulation of the homojunction solar cell spectral response which allows us to derive the absorption spectra of the given samples and to study the influence of high energy particle beams on the cell performances. Moreover, the computation based on our model provide the values of certain microscopical parameters which are consequently used in solar cells design optimization.

This paper reports on minimizing measurement errors that are characteristic of small distances of the object plane through continuous focusing of optical system that concentrate radiation on a typical opto-electronic detection device. One such system is the catoptric objective that uses a focusing system based on the movement of a mobile element inside the objective. Our results show that decreasing the distance between the mobile and fixed element leads to an increase of the focal distance and consequently of the object plane distance. The measurement precision increases with optical amplification, and hence, we studied the way optical amplification, and hence, we studied the way optical amplification changes with a continuous focusing, in two different situations: the detection device is calibrated at the maximum distance and the detection device is calibrated at the minimum distance. Finally, we present different examples of variation of measurement precision for discrete values of properties of some objectives. In order to minimize image-focusing errors for the extreme distances, aberrations optimization of the optical systems for an intermediate position of the object plane was factored in.

The study of recombination lifetimes and kinetics is an essential part of the analysis of recombination mechanisms in semiconductors. The fundamental differences between the experimental techniques, which are used for, frequency- resolved and for time-resolved spectroscopy are present in this paper. A photoconductive frequency-resolved spectrometer (PCFRS) for carrier lifetime determination in semiconductor is described. The PCFRS uses a super-bright light emitting diode, which can be modulated directly and the sample acts as a detector. An embedded system with 68HC11 microcontroller ensures all basic functions of this spectrometer. This PCFRS is designed for a narrow lifetimes range, the operation range is between 0.159 s and 0.159 ms. Typical error is less than 0.5 percent for the range of lifetimes reported.

A new method of processing Newton's rings fringe patterns is presented. After the center of the circular rings is found, a special type of pixel intensity spectrum is calculated, in which the 2D pattern is reduced to a 1D profile showing a periodic structure of fringes. By further processing the parameters of the initial interferogram can be easily extracted. The statistical nature of the method leads to a higher accuracy and a better immunity to noise.

This paper presents an electropneumatical system computer assisted for compensate the sag of an optoelectronical detector. This system is used for compensate the sag of a frame of an optoelectronical detector during the fabrication. For push-up group we use pneumatically servocylinders which allowed a very precise control of the sag through force. Each servo cylinder includes a proportional pressure regulator for regulating the pressure proportional to a specified electrical nominal value. The system is controlling by a PC with 2 acquisition board, one of them for monitoring the force of the transducer and the other board for controlling the pressure of the gas in servo cylinders. The software subsystem for developing the tuning numerical algorithm contents WIN 98 operating system, TestPoint rapid application development platform for data acquisition and graphic user software and Delphi rapid application developing platform for real time control algorithm module.

Product designing is one of the phase of the project management. The Quality System's elements, referable to design, are included in the project management. The produce definition in accordance with the stated and implied requirements, is the most important phase for the product's quality. Obviously, the sooner the best solution is selected and the deficiencies detected, the better the product quality will be, and at better price. From here, it reslut the importance of the design and Quality System planning. Design is a creative task which stars with stated needs and existing Knowledge, and ends with definition of a product that satisfy those needs and is industrially feasible. The products must be designed for the client's, not the company's benefit. The products that do not have the right set of features will not be as well saleable those products that have the right set of features. The best design may fail if it is not correctly planned. Quality planning provide a structure that helps a successful project. The emphasis is made on learning the concepts and abilities, on tools and techniques required to build quality.

In this paper, the possibilities to improve the quality of products/processes using modern methods and equipment for non-destructive control are presented. The quality control is represented by the operation techniques and activities used to fulfil the conditions concerning the quality, it is a way to verify the realization of quality and to establish necessary actions to correct the non-conformities. The defectoscopy represents an assembly of methods to examine materials, prices and joins to discover their defects by non-destructive control methods. The essential requirements of non-destructive control, in connection with the imperatives of total quality's concept determinate in a short period of time a high attainment of systems' quality. In the second part of the paper, the possibility to achieve non-destructive control with the aid of robotic system, the appropriate cases in which the robots are useful, the type of robot together with constructive details are presented. The two main directions where the robotics is useful are non-destructive control in technological flux and the control in hostile or unapproachable environment for human operator. In the first case are used with proper software, and in the second, remote control robots. Finally, the advantage offered by the robot utilization for non- destructive control in special situations is emphasized.

Using a numerical code assisted data processing we show that the precision in the ellipsometric type measurements can be improved with a sufficient degree of confidence, up to an order of magnitude. Our method is based on fitting the experimental data with a pari of functions of known theoretical behavior. Essentially, we corroborate the result obtained from one strongly nonlinear function to those given by another behaving 'ultra-linearly'. When working with consistent experimental data, this procedure leads to a pair of 'outputs' that enhance one another producing an increased degree of precision. The paper explicitly applies this idea to an ellipsometric type measurement for the refraction index of a glass specimen.

The object of this paper is to evalute both the temperature distribution and the dopant concentration for a 5 micron diameter single mode SiO₂ fiber optic that is doped with GeO₂. Fundamentally, what drives the need to know this information springs from a theoretical model which suggest that the index of refraction, leading from the center to the edge, follows a parabolic curve.

In many opto-electronical apparatuses it is necessary to overlap two or more optical images on the same image plane. For apparatuses having similar optical scheme, such a problem means different optical path and components for subassemblies with similar function. For each application, there are designed specific optical channels using similar optical elements to project similar objects, which differ in shape and size. Hence such devices have many disadvantages and basically they are not interchangeable. That is why it is very important to find new methods to joint optical channels and the paper presents the results of the studies we have made in this direction.

Thermographic methods and equipment are very useful in detecting energy losses by heat emission in thermoelectric plants; these methods allow the predictive maintenance of such plants and ensure a diminution of operating costs. Classical methods for determination of warmer spots and ares are inefficient and sometimes impossible to achieve, especially in the case of large plants. A global analysis of the areas into which can appear heat leakage was carried out using thermography, the method being independent from the complexity and the placing of plants. The method of thermography allows an easy location of these thermal losses and their qualitative estimation. Experiments were carried out using the LORIS thermovision equipment. The thermal images were processed dedicated software, ThermaGRAM for Windows 95. Some relevant thermal images presented in this paper, also.

In view of the increased need of an effective, practical and unified test set to evalute the modeling capabilities of beam propagation method (BPM) based programs, we prose an incident set of tests to be used for a standard evaluation. The proposed test have been chosen to be simple, easy to implement and enable a fairly good evaluation without the need of any experiment. Interesting aspects of the tests' results and some straightforward, practical criteria to estimate program capabilities and to tune the simulation parameters are presented. A cross-checking between 'Mode Solver' based and BPM based programs is also put into discussion. A paraxial error evaluation method is presented and the transverse mesh influence on the paraxial error is analyzed.

Laser crystals with disordered structure present a series of advantages for diode pumping or short pulse generation as compared with ordered crystal. Such a system proved to be calcium lithium niobium gallium garnet (CLNGG) doped with Nd³⁺. The papers present the growth and x-ray analysis of specially doped CLNGG. Very few spectroscopic data on this system have been previously published. The paper present low temperature absorption spectra, site selective excitation and lifetime measurements of Nd³⁺ in CLNGG. At least four distinct nonequivalent centers are observed, the spectral lines for every center presenting a disordered Gaussian shape. based on structural, spectral static and emission dynamics data an attempt of modeling the structure of these centers is proposed.

This paper presents a method to retrieve the relative phase of an optical field starting from three digitized intensity records. One record is that of the classical intensity of the field itself, while the second and the third are intensities obtained after some filtering operations performed in the Fourier space of the optical field. The paper also gives several applications of the algorithm to both 1D and 2D cases.

Based on the coupled amplitude equations model in this paper we present a theoretical analysis of the third order harmonic generation process in optical organic waveguides. Also, we report the experimental conditions which must be accomplished in order to obtain the best conversion efficiency. The obtained results can be used for the design of the optical organic waveguides in which third harmonic is generated.

This paper investigates the dependence of local emissivity, for two spectrum lines of helium, upon the location within a stationary double layer. The experimental result are explained starting from a new phenomenological model, which takes into account the non-elastic interactions between the accelerated electrons and the atoms of the working gas.

Our paper studies the influence of the irradiation by fast electrons on the characteristic properties and microscopic parameters of certain MOSFET transistors with p-induced channel. Using the experimental data, an appropriate theoretic model and an optimization method, the following specific parameters were computed for the irradiated and un- irradiated samples: the electron mobility, the Fermi energy value, as well as the saturation voltage and the changing of the drain channel length.

Starting from the experimental channeled spectra I of the nematic EBBA liquid crystal and using a nonlinear optimization algorithm, we computed the dispersion curves of the ordinary and extraordinary indices, of the birefringence and the band contributions to these dependencies, as functions of the temperature. The theoretical interpretation of the spectra and the data processing technique allowed us to compute the realistic variation of the order parameter S and correction factor g with the same external parameter.

An extended version of the Antisymmetrized Molecular Dynamics method is derive din order to study clustering aspects for two conduction regimes defined by the role of intercrystalline barriers and crystallites in CdSe thin films and to compute the related interaction potentials. The influence of the fast electron irradiation on the conduction mechanism is consequently expressed in terms of the changings in microscopical parameters.

We study from a theoretical point of view the electromagnetic enhancement related to the surface enhanced Raman scattering on silver gratings. The local field is obtained by means of numerical calculations based on the rigorous coupled-wave analysis. Enhancements of up to 10⁶ in the Raman signal of molecules adsorbed on these gratings could be obtained at the excitation wavelength (lambda) equals 514 nm.

In this paper we present some experimental results concerning the effect of fast electrons irradiation on the specific conduction mechanisms in semiconducting polycrystalline vacuum evaporated CdSe thin layers, in strong electric field, and we give an interpretation of the non-ohmic electrical conduction in these layers. Two conduction regimes defined by the different roles of the intercrystalline barriers and crystallites respectively are analyzed. The changing of some microscopic parameters is calculated from the fitting of the experimental and theoretical I-E characteristics, both for irradiated and unirradiated films.

The beam quality of solid-state lasers with high average power can be greatly improved using phase conjugators based on stimulated Brillouin scattering (SBS). The common phase conjugators used until now are liquid or gas cells.Using SBS in glass fibers as phase conjugators the field of applications can be expended. The long interaction length and small cross-sections of the fibers result in an appreciable reduction of SBS threshold and avoid optical breakdown which could happen in liquids and gases at high input energies. Other advantages of glass fiber phase conjugators are harmlessness and easy handling. We have experimentally investigate a phase conjugator base don SBS obtained in an undoped quartz fiber with core diameter of 200 micrometers . The SBS threshold reflectivity and phase conjugation capability were measured with 18 ns pulses at 1.06 micrometers wavelength with different input energies.

An extension of the 'Orthogonal Collocation Method' is proposed in order to treat various realistic problems of nonlinear waveguiding in multiple-layer structures. The simulation results may be an important factor in designing multiple quantum wells structures which are widely used in optical signal processing devices.

The aim of this paper is to present some results in the experimental study of heat transfer in fluids by optoelectronic methods. The thermal source was a thin metal wire (TMW) heated by electrical impulses and the propagation medium was the distilled water. We studied the following configurations for the thermal wave propagation and heat transfer. (1) Horizontal TMW far from the water tank walls; (2) Horizontal TMW in the proximity of a vertical metal wall and at a discontinuity introduced by another metal wire; (3) Horizontal TMW with a controlled air bubble flow. The phase perturbations in the transparent medium were visualized by a compact schlieren system with laser diode illumination and were digitally processed in a PC. These results offer a better understanding of some progressively complex thermohydrodynamic phenomena. Some possible applications are in visualization of the route to turbulence in these flows and in designing calibrated phase objects.

We consider the problem of wavelength reuse assignment and of routing in all-optical networks. Since the capacity of number of wavelengths of current optical communication devices are restraint, the optical wavelength reuse is the only solution for this issue. The problem is NP-complete and therefore does not have one and only solution. Several algorithms were proposed along the years on this subject. In this work we develop a metric for wavelength assignment algorithms in all-optical networks like deBruijn networks for instance. We derive an upper bound of traffic corresponding to connections in such a network. The bound depends on the number of edges of the network respectively. We compare the bound with the simple shortest path algorithm to test its validity. The simulation test result show that it is feasible to get several all-optical connections to each node in a large network using relatively limited number of wavelength compared with the number of traffic sources.

During the pulsed high power laser target interaction a local heating or material ablation takes place in function of incident laser energy. In both cases a stress wave is induced in the material volume with characteristics determined by the phenomena taking place in the interaction region. Analyses of the detected acoustic wave first peak amplitude and especially of the region of the transversal wave appearance results in a method of interaction regime characterization, ablation threshold determination and multipulse processes in-situ monitoring.

Zero-order transmission silver gratings of very narrow and deep enough slits exhibit exceptional transmission properties in visible and near-IR light. By using a rigorous electromagnetic analysis of light diffraction, we show that the transmission enhancement occurs as a result of a resonant interaction of the incident light with surface plasmons located inside the grating slits.

Modern procedures have been elaborated taking into account the laboratory findings and developments of the past two decades concerning the factors increasing the solubility of iron oxides in the cleaning agent and conditioning improving the characteristics of the protective layer, both having in mind the present state of corrosion in romanian power energetic plants. The basic reagent formulae consists in citric acid, hydro-chloric acid, ferrous sulfate as dissolution activator and a corrosion inhibitor, operating at T 80-85 degrees C. The removal of thick corrosion deposits is achieved in a basic step-by-step procedure, the number of steps depending on the layer thickness and on the degree of damage of the underlying base metal. After chemical cleaning, a passive magnetic film will be formed under special conditioning of water with long-chained amines.

In the process of development new chemicals to be used for generating smoke screens, a method for evaluating the masking ability for the IR spectral domain was needed. The experimental set-up, involving a thermovision equipment and a reference body is presented. The experiments were carried out for different types of chemical mixtures, both in laboratory and field conditions and the attenuation coefficients were calculated. The relevant thermal images, processed using dedicate software, are also presented.

Experimental data of mass spectrometric analysis of vitreous As₂(S, Se)₃ chalcogenide glasses shows the perceptible difference in the values of As_m(S, Se)_n ion currents before and after laser illumination. Data of the computational calculation of the stableness of molecular units are in good correlation with obtained experimental mass spectrometric data. After laser illumination we detect new kinds of molecular units as As_m, S_n, and Se_n. The observed changes of the ion currents in the mass spectrum may be explained in view of some re-arrangement in the shot-range order of the component atoms under illumination. We propose for discussion the results of computational modeling of molecular units such as As_m(S,Se)_n observed experimentally in the As₂(S,Se)₃Sn_0.1 alloys by their mass spectrometric analysis before and after laser illumination. In this report we suppose that a study of the composition of condensed molecules by the intermediacy of mass spectrometry and HyperChem Computational Chemistry Program may harvest complementary information useful in orders to building structural models of chalcogenide glasses. In reslut of this work we also conclude that tin atoms in the As₂(S,Se)₃Sn_0.1 network are bonded in two modes: before illumination as 2(S,Se) equals Sn equals 2(S,Se)-type and after illumination as (S,Se)-Sn-(S,Se)-type.

The gyroscopes are defined as devices, which can measure, autonomously, rotational motions relative to inertial space. They are of central importance for flight control, for navigation/orientation in the air, at sea and on land, and also for stabilization/guidance of smart weapon systems. Benefitting form advances in semiconductor technology, the basis of gyro systems has changed from mechanical platforms to strapdown technology. For strapdown use, new types of gyroscopes, such as optical gyros, have been developed. This paper presents optical gyros, emphasizing the fiber gyro and its principal advantages such as solid-state operation, light weight, small size, low power consumption, rapid turn- on time and high reliability, that are important considerations for many high-performance application areas.

The hot cracking problem encountered when 1 mm thick stainless steel sheets are seam welded using a long pulse Nd:YAG laser is studied. Cracks are observed only in regions where the primary austenite was formed in the cooling phase, depending on it amount in the weld. The initiators of cracks were found between the heat affected zone and base metal as a band of segregate. High repetition rates decrease the crack formation at constant average power and welding sped. The primary austenite dendrites are strongly influenced by cooling rate. Melt thickness increase with pulse energy when pulse duration and repetition rate are kept constant. The optimum focus position was approximately 0.5 mm below the level of the workpiece front face and produced good quality seam welds.

The development of the selective laser sintering (SLS) technique used for rapid building of 3D models from metal powders is presented. The aim of research efforts in laser sintering is to create strong and dense models with no need post-machining. The feasibility of SLS is demonstrated by the mechanical properties of models obtained, which nearly the equivalent to the products formed by sintering in conventional way. However, the range of the materials available to SLS technique is limited to weldable metals and alloys. The main benefit of this laser application is the exact control of process parameters. A Nd:YAG laser working in CW regime was used. It was obtained sintered powder parts with a fine accuracy up to 0.4 mm. The shrinkage degree of height was lower than 10 percent. The microstructure and mechanical properties of SLS processed materials are similar with those of conventionally processed material. The strength and the bulk hardness of the sintered material were tested.

This paper addresses the equations necessary to evalute the required sampling frequency as a function of the ratio of amplitudes between the clock frequencies and the frequencies that are modulated onto the respective clock frequencies. A key ingredient that is also involved in the appropriate selection of the sampling frequency is the base band noise level that is indicated for each of the channels that are provided in the protocol from the information providers. By using the technique was associated with thermal signature and imaging processing, one is able to use a multiplicity of fast fourier transforms to subtract out images from background and noise and to recreate the image in a clean and noise free environment. In so doing one is able to maintain the image without subjection to outside disturbance or distress.

A new application of glass surface treatment is presented here. Fine polishing of optical fiber end, core/cladding surface, is performed. A small power monomode longitudinal 10 W cw CO₂ laser is used. A decrease of the roughness form about 5 microns to hundreds of nanometers was achieved. The microstructure of the surfaces has been studied using atomic force microscopy. Applications of polished fiber surfaces are given.

The laser ablation is one of the best ways to obtain smooth thin film deposited on various substrates. However, to obtain a 'droplets-free' surface some special experimental setups are necessary.ONe of them is the 'eclipse' method, using a plane shadow mask. Based on studies on the plume behavior in a 'standard' deposition and in a plane shadow mask eclipse deposition, we prose a new shadow mask having a an helicoidal shape, which permit to obtain a abetter film quality - maximum droplets size about 10 times smaller than for the plane shadow mask. The plume behavior and thin film quality are presented and discussed.

In actual systems the optic signal are detected, processed and electronically recorded. These hybrid system diminish considerably the processing speed of otpical signals. So, it is absolutely necessary to implement the processing signals of optic systems which have to be competitive with the actual electronic systems. In this paper, the authors present from theoretical point of view, the realization of some logical gates with photonic devices and combinational logic circuits with photonic deices as decoder, demultiplexer and multiplexer.

In this paper the author presents a laser irradiation alert station which uses the directivity characteristic of the photosensible element in order to determine the direction of the irradiation beam. In order to solve this problem, the author considers a certain number of photodetectors obtained after the average optimization of the medium value of the square estimation error in different directions of the space. The M measure matrix is obtained as a result of this optimization. Having the values of the measure matrix elements, the error which occurs in determining the direction can be calculated taking into consideration different values of the error with which the senor determines the direction of the radiation beam.

Monolithic top emitting resonant cavity light-emitting diodes operating in the 650 and 880 nm ranges have been prepared using solid-source molecular beam epitaxy growth. Transfer matrix based modeling together with a self- consistent model have been sued to optimize the devices' performances. The design of the layer structure and doping profile was assisted by computer simulations that enabled many device improvements. Among the most significant ones intermediate-composition barrier-reduction layers were introduced in the DBR mirrors for improving the I-V characteristics and the cavity and mirrors were detuned aiming at maximum extraction efficiency. The fabricated devices showed line widths below 15 nm, CW light power output of 8 and 22.5 mW, and external quantum efficiencies of 3 percent and 14.1 percent in the 650 nm and 880 nm ranges, respectively - while the simulations indicate significant performance improvement possibilities.

A comprehensive analysis of the small-signal direct modulation response, based on quantum well (QW) laser rate equations model is presented. This theoretical model is first analytically analyze din order to estimate the influence of the phenomenological parameters taken into account on the modulation bandwidth. We show theoretically that the leakage current increases the low frequency parasitic-like roll-off effect and degrades the differential gain. Results from modulation measurements of a 5 QW AlInGaAs/InP structure are presented. The measurements are fitted with the theoretical model evaluation and the modulation response figures of merit are deduced. The modulation bandwidth limitation mechanisms are related to the extracted parameters and explained by means of carrier transport effects. Simulation results are used in order to assess the carrier capture/escape time ratio influence and leakage current influence on the modulation response.

We present two different Ac magnetic field sensing configurations exploiting the Faraday effect in the semiconductor compound Cd_0.57Mn_0.43Te. The first configuration is a typical polarimetric set-up; the periodic magneto-optic polarization rotation of a linearly polarized input in the transducer crystal is converted into intensity modulation by means of a polarization analyzer. In the second configuration, the Faraday modulation appears in the electronic spectrum of the interference signal at the output of a hybrid Mach-Zehnder interferometer. Both set-ups include noise rejection schemes to improve the signal to noise ratio.

LabVIEW is a consistent development and execution environment that provides a method to implement various test and measurements' systems containing stand alone laboratory instruments. This paper describes a virtual instrument created in LabVIEW that facilitates the control of a dual channel laser power/energy meter through a computer serial port, for accurate laser power/energy data logging and handling. The program has a modularity structure and could be easily used in conjunction with the device in any application involving laboratory laser power/energy measurements. The program was tested with very good results for the characterization of different types of lasers.

In optical design applications for night vision system they are situations when an optical system have to work in multiple configurations. This paper speaks about such a situation when an eyepiece have to combine the image from the image intensifier screen with the image of the symbology needed for gun aiming. We use the Multi-Config Zemax facility, with the accent on the necessary operations and delicate points of the optical design process. We present some results for a real situation.

This paper investigates the feasibility of using an optically power sensor head as part of an intelligent sensor by means of a model realized using MSI CMOS integrated circuits with a view to a future ASIC version. Measurements were made under control of commands transmitted along the optical power line and digital data returned. This was achieved with an electrical power at the sensor head of less than 100 (mu) W, enabling the system to operate with an optical power of 1 mW.

Thermal imaging converts the IR radiation of a scene into a live picture of that scene; the thermal image is a pictorial representation of temperature differences. One of the most promising new sensor for thermal imaging is the IR focal plane array. The IR focal plane array consists of a large number of minuscule IR detectors which can resolve targets as little as one tenth of a degree warmer than their surroundings, and offer enormous gains in data throughput per unit time without mechanical scanning. Imaging arrays are the most advanced IR detectors and commonplace in products ranging form hand-held IR cameras for industry and security use, to sophisticated systems for military applications.

The atomic fountain is a new high-performance primary frequency standard where the stability is of the order of 10^-17 and the accuracy of the order of 10^-16. Our goal is to realize such a standard in our laboratory. In an atomic fountain we can distinguish three basic parts: the cesium atom source, the microwave and the C-field region, and the detection are. In this paper we briefly recall an atomic fountain operation and present the first research results obtained in our laboratory concerning the atomic cesium fountain.

The new atomic Rb-Cs fountain should confirm the recent theoretical calculations relating to the collisions of rubidium atoms. According to this theory, the displacement of the frequency of clock due to the collisional shift was predicted to be 15 times lower for ⁸⁷Rb than for ¹³³Cs at equal density. Using Rb instead of Cs in a foundation standard may lead to an order of magnitude improvement in frequency stability together with an excellent accuracy. In this paper we describe the operation of a laser cooled ⁸⁷ frequency standard and present a new measurement of the ⁸⁷Rb ground state hyperfine frequency with a relative accuracy of 2.4 10^-15 by comparison with a Cs fountain atomic standard. In order to measure this, first we determined the absolute frequency of the reference H-maser by comparison with the LPTFs Cs fountain. Second, we corrected the measured frequency to take into account different systematic shifts: magnetic field, black body, microwave leakage, collisions. The measured frequency is 6 834 682 610.904 333 Hz. This value differs form previously published values^1,2 by about 2-3 Hz and is 10⁴ times more accurate.

A small average power CO₂ laser for some industrial applications is presented. The laser might operate both in a continuous regime and in a pulsed one or in a combination of two. Average power up to 20 W and peak power of several hundreds of kW has been achieved. The advantages of the good optical quality bema of a longitudinal discharge laser and of a high peak power pulsed regime are simultaneously achieved. A high voltage capacitor, which is switched on by means of a rotary spark gap, sustains the pulsed regime. The commutation between the two regimes might be easily done and a mixed operation is obtainable. By superposition of the two regimes, a continuous heating of the materials by the continuous beam as well as an evaporation due to high peak power are obtainable. Drilling, cutting and marking of different types of glasses as well as different plastic materials were performed.

One of our latest developments regards the achievement of an omnidirectional acoustic transducer able to work in marine environment in a wide band of frequency. Our research has involved allowing a fairly linear variation of the impedance active component. This paper presents some aspects concerning the effective achievement of the acoustic transducer and the compensation of the impedance reactive component in order to obtain a maximum transfer of power. The acoustic transducer have a specific construction and are made of PZT-type piezoelectric ceramic obtained in laboratory. Some essential aspects of the measurement methodology and the results obtained are also addressed.

This paper describes equipment used for gluing the parts of an optoelectronical detector. Two rails compose this equipment and a dispenser and electronically system for control the moving of dispenser in two directions and the start/stop of the glue. For rails we use modular components. The moving on the X direction is realized with two long shaft and bushing. For transversal moving we use a special guiding and bushing. This equipment will fix on a granite table using special support. Electronic systems will fix on a control plane near a granite table and will link with thin and very flexible cable with equipment.

An optoelectronical detector is composed by a frame where we assemblies all the parts. Technical conditions, 20 micrometers on the wire positioning requires a high level of mechanical precision in the assembly procedure. During the procedure of fabrication the frame of detector is fixed on a special support. To obtain high assembly precision compensation of this deformation is necessary. The equipment for compensate this deformation is composed by a pneumatic system, with sensor for measurement the force and a PC for monitoring and controlling. This paper describes the method for measurement the sag of frame of an optoelectronic detector using pneumatic equipment.

We present fiberized OCT systems developed to image biological tissue with high depth resolution. The systems can deliver transversal as well as longitudinal OCT images. When in the transversal mode, the systems provide a confocal image simultaneously with the OCT image. Design particularly in adopting the system for imaging either the skin or the retina in vivo are presented. They refer to the interface optics, power to the tissue and imaging speed. Images from retina and skin in vitro and in vivo are shown. When applied to the eye, line rates up to 1 kHz and frame rates up to 5 Hz can be used. In order to improve the penetration depth in skin, lower scanning rates are used. ALso, flow of milk into a vessel simulator is investigated using Doppler OCT. In this case, no transversal scanning is applied. The laminar profile of the velocity inside the vessel is determined with the depth accuracy of the OCT.

Speckle interferometry for non destructive testing of out of plane or in-plane stresses or deformations of rough mechanical parts is a powerful and modern technique. Basics of speckle phenomena and interferometry in specked light are reviewed. Electronic speckle pattern interferometry for vibration analysis and a Duffy-Young digital camera for in- plane measurement are presented.

Phenol exists in wastewater streams for many industrial processes. The toxicity of phenolic effluents is well known as their treatment must be accomplished. Among the methods of recovery, the technique of adsorption provides a convenient way with low cost. For modeling the diffusion process it is necessary to know the diffusion constant. The technique of double-exposure holographic interferometry is used to study phenol diffusion in water in the presence and in the absence of activated carbon. The diffusion constant is calculated by a simple and direct measurement of interferograms.

This paper present the physico-chemical properties of some synthetic porphyrin dyes obtained at ZECASIN SA. We have measured the absorption, excitation and fluorescence spectra of these dyes in different solvents. From them we have concluded that the most reliable due for our studies concerning the photodynamic therapy with UV lasers is Zn II- tetrakis-sulfonatophenyl porphyrin.

Researches on thermal processes developed inside the human body and on the quantity of heat emitted by the body in its environment allowed obtaining important information about the equilibrium between the human body and its environment and about the body's biological activity and state of health. Methods like thermography and thermovision, involving measuring human body's temperature, are presently used at present as medical diagnose methods for diseases even in their early stages of development. A very accurate piece of information about the thermal processes that are developing inside the human body can be obtained from direct measurements of the heat emitted by the body's surface using thermal flux sensors of a thermoelectric type. Thermoelectric effects occurring in anisotrope and inhomogeneous media are involved in functioning of this type of sensors that can detect heat fluxes up to 10^-8 W/cm².

This paper presents an analysis of the remote sensing methods of extracting information on soils and land cover. For this porpoise we selected Danube Delta, a complex ecosystem, with an important role in Romanian environment and economy. Several types of satellite images were used; in order to assess their suitability in land cover and vegetation changes detection. Landsat MSS and TM, ERS 1 and 2 images were used. We applied contrast enhancing and special filtering procedures to improve image and remove speckle. At the end of this phase, we obtained good quality images with not significant information losses. One these images we performed unsupervised and supervised classifications. The result of this application was the confirmation that only combined sets of images can be a useful tool for land cover assessment, vegetation and soil discrimination. Beside the multi sensor approach, another condition for a compete observation is the multitemporal approach, by using several images acquired at different intervals of time, in this way we can obtained a good vegetation discrimination on seasonal basis.

This paper presents an autoassociative memory built for graphic pattern recognition. The network was designed for the validation of handwritten signatures form bank documents. Neurons interconnections are considered to be implemented optically by computer generated holograms (CGH). The network functioning was simulated on computer and the paper presents the result of simulations on a data set and a CGH layout for neutron interconnections.

The functioning principles, hardware and software structures are presented, and on this basis, the essential differences between the usual optical system at which the sighting in direction is stabilized and an optical system of a special type whose stabilized element is its viewing field are brought to evidence. The principal applications these optical systems with viewing field stabilized by using of some reverential elements of inertial type can have are also presented. In those situations in which is oriented upon some fixed target the ISVFS presents some functioning similarities with those opto-electronic devices that achieve the stabilization of the image received on a monitor screen by 'point by point' analysis of this image.

This paper studies the influence of radiation thermometer optical system properties on the total radiating energy upon an optoelectronic detection device when the measuring distance ins variable. The first pat is a brief analysis of characteristics of concentrating IR radiation through the thermometer objective. The sources used are smaller, larger or equal than the detection device field of view. When using the equal sources, the specific shape of the measuring area was taken into account, and included in the total field of view. Catoptric objective was used. In addition, this paper present the main error sources on concentrating IR radiation on the detection device in following conditions: the calibration is performed at a finite and infinite distance, the radiation source is assumed to be perfectly Lambertian and the objective is catoptric.

This paper presents work to determine the effects produced by low energy laser radiation on the metabolism and growth of a yeast cell suspension. As experimental material, we used young yeast culture in liquid medium, then distributed on a solid medium, to obtain isolated colonies. As laser source, we used a He-Ne laser, and the irradiation was made with different exposure times. Form each irradiated material, a sample of white grape sterile must was sowed, that has fermented at 18 divided by 20 degrees C for 10 divided by 15 days, after that some properties was tested. Some microscopic studies were also made. The results prove some influence of low energy laser irradiation, which can induce mutations, with new properties of the irradiated material. These mutations can be obtained in a positive sense, with new and important perspectives in wine industry. Also, we observed an inhibitory effect of the laser radiation on the yeast cell growth, due, probably to the too high values of the exposure.

The lock-in amplifier technique is frequently use din characterization of optoelectronic devices. A digital lock- in amplifier and a digital direct synthesis signal generator are implemented with a general propose 68HC11E1FN microcontroller. The resolution in frequency is less than 1 Hz. The digital lock-in amplifier over a frequency range from 1 Hz to 1 kHz and can measure signal at any harmonic of the reference signal. Typical error is less than 0.5 percent for the range of frequencies reported. This digital lock-in technique is inexpensive and can be used in experiments with low frequency response.

The environmental diagnosis and supervision mobile system for emergency cases it is flexible system which support the decision and the management of the risks. To optimize the time reaction, in case of emergency, is synonymous to save the maximum possible lives. The decision in such a case must be strongly supported by a wide information pictures, information needed in a command center both for the acting operators and civilian people. The system described below try to clarify the general architecture necessary to be adopted in order to response at such a need. The authors inform with this occasion that his architecture it is a very flexible one and could be configured upon request.

The low power radio frequency capacitively coupled plasma sustained in air at atmospheric pressure is described with the aim of using it as spectral source for atomic emission spectroscopy of pneumatically nebulized liquid samples and the direct analysis of non-conductive solid samples. The plasma was generated at a frequency of 13.56 MHz, absorbed RF powers of 20-70 W and air flow rates of 0.1-11/min, begin intrinsic part of the resonant circuit of a free-running oscillator. The liquid samples were pneumatically nebulized using a Meinhard nebulizer and introduced into the plasma via a 4-roller peristaltic pump. The rotational temperature and the intensity ratio of ion to atom lines for Ca were determined experimentally. Detection limits were determined using the '3(sigma) method' given by Boumans for 11 elements at an RF power of 50 W and air flow-rate of 0.7 1/min. The same plasma was used for the direct analysis of non- conductive solid samples. All measurements have been carried out on cylindrical samples pellets of chalk, pressed in a steel press at a pressure of 87 X 10⁵ Pa, at an RF power of 40 W and air flow-rate of 0.5 1/min.

This paper analyses the behavior of fatty acid-cholesterol mixtures, components of biological membranes, under the influence of the electromagnetic filed. The mixtures acid lauric-cholesterol, prepared in this layers of 24 micrometers , have a liquid crystal behavior at room temperature. Spectra obtained in the range (330 divided by 800) nm put into evidence some regions of resonance between the oscillatory system characterizing the textures and the electromagnetic field. The result are discussed in terms of Maxwell's formalism. A good agreement between experiment and theory was obtained for the lauric acid. The impurification with cholesterol leads to a greater disorder in the system and the agreement with the theory is no more satisfactory.

The ability to accurately measure the particle sizes distribution of particle suspensions and dispersions has proven to be crucial for ensuring the success of a wide process materials and final products. We propose tow optical fiber sensors that exploit light intensity modulation in optical fibers. One of them is constructed in a typical reflection-sensing configuration but it sues the backscattering effect on particles in suspension. The other one is lens deflecting the light away from incident beam. Furthermore, we have presented the theoretical framework concerning the light scattering on dielectric spheres and colloidal aggregates. The relevant experimental data are also shown in order to prove the sensors reliability.

This study present the reslut of the application of remote sensing techniques to the seismic are analysis and monitoring. Remote sensing methodology and field studies of active faults can provide a geologic history that overcomes many of the shortcomings of instrumental and historic records. We present the result of comparing ERS-1 and optical data, and we analyze if the structural inventory can be traced more accurately, by the help of ERS-1 data. First results show that lineaments in Landsat-TM images appear denser in shorter distances whereas ERS-1 images are dominated by the principal structures.

In digital imagery, picture elements which contain two or more land cover classes are called mixed pixels. Small strips or patches of woody vegetation, typical landscape features in many farming areas, are frequently not detected by standard computer-assisted classification of digital imagery because such landscape features are smaller than the pixel size of the image and are mixed with other classes. Development of advanced techniques for improving remote sensing image classification accuracy is essential for deriving reliable land cover information for natural resource applications. Artificial neural networks ar among the optical tools for this type of application. Neural network techniques were developed for processing two dates of Landsat TM data, and measure of image texture for the purpose of deriving more accurate land use and land cover information. Classification results derive from the neural network approach overall were nearly 10 percent more accurate than those derived previously using a conventional maximum likelihood approach.

The quality audit of a product serves to evaluate the accordance of its quality characteristics with customer's requirements or specified in references documents. On this occasion the reference documents are verified, in order to establish if these are prosper to achieve the stipulated objectives in the domain of products quality. The audit is not a simple examination of product's quality, but it is an effective quality measure concerning the respective product. Based on the results of quality audit it can settle necessary improvement measures. The process quality audit serves to evalute the accordance of the process with customer's requirements or with specified requirements in the references documents. In order to establish if the reference documents are proper to achieve the stipulated objectives, these documents are verified, just like in the case of the quality audit of product. The quality audit of a process present also the effective measures to ensure the quality of the process, establishing the necessary corrective and improvement measure. In order to perform the quality audit of the product/process, the procedures of quality system, the specification of the product, the documents, the manufacture and inspection means, the documents concerning the development, supervision and inspection of the process and also the requirements which refer to the qualification of the involved personal are verified.

This report relates to a mobile system for tracking and protection of vehicles owned by some banking organizations, security institutions or by some social service for fire, medical rescue or taxicabs, by an operator placed also aboard of a vehicle in which he has at his disposal all the necessary means for precise determination of the position and the state of each vehicle from the fleet that is under his surveying. Therefore in contrast to the operating mode of the localization systems known in present and which have in its composition a stable center for permanent surveying, the operator of the system presented in this report can intervene personally and in an efficient mode in the aid of the vehicle in distress.

A method for local thermodynamic equilibrium plasma diagnostics by vibrational structure of diatomic molecule electronic states is elaborated. On this purpose is adopted a model of plasma temperature determination from the relative intensities of the molecular vibrational band head incompletely spectrally resolved. The relative intensities were determined using the temporal integrated profile instead of peak or integrated spectral profile of a band head. This more accurate method of vibrational temperature determination allows obtained new data about the plasma internal processes.