Diode lasers are widely used in communication, computer and consumer electronics technology. These applications are based on systems, which provide power in the milliwatt range. However, in the mean time high power diode lasers have reached the kilowatt power range. This become possible by special cooling and mounting as well as beam combination and beam forming technologies. Such units are not only used as a new, efficient and highly reliable pumping source for solid-state lasers, but also as a direct source for materials processing. In this application high power diode lasers have entered the industrial manufacturing area. This article describes the diode laser technology and the applications. Ideas for future applications and for novel application concepts of high power diode lasers are intensively investigated in the five year German national research project Modulare Diodenlaser Strahlwerkzeuge - MDS. Besides improvement of beam quality flexible laser beam geometry, which is matched to the application in a modular concept, is the target of the project.

A new Optical Parametric Oscillator for the mid infrared wavelength region of 3-3.8 micrometer is developed with an idler output power of more than 1 Watt. The OPO is pumped with a 10 Watt, cw, Nd:YAG Laser and consists of a bowtie ring cavity (FSR 320 MHz) resonating at the signal wavelength. The wavelength is controlled with a fan-out PPLN crystal and a low finesse intracavity Fabry-Perot. The idler output could be tuned over more than 24 Ghz modehop-free, by tuning the pump laser and keep the OPO cavity fixed. Mode hop tuning over 100 Ghz could be obtained changing the length of the intracavity Fabry-Perot. This high power OPO is combined with photoacoustic spectroscopy in order to develop a sensitive trace gas detector for LifeScience applications.

An adaptive negative thermal lens that compensates for the power- dependent positive thermal lens in a transversally diode-pumped Nd:YAG laser rod is presented. The compensating (negative) lens is generated in a thin layer of liquid. We demonstrate that the proposed technique leads to a reduction of the thermal lens by more than an order of magnitude.

The role of gas-phase reactions during pulsed-laser ablation in low-pressure atmospheres has been investigated by time- and space- resolved spectroscopic measurements. Thus, excited species have been detected by optical emission spectroscopy. The population densities were determined in an absolute scale after calibration of the spectroscopic apparatus. Complementary information was obtained by detecting ground-state species using laser-induced fluorescence (LIF) spectroscopy. Therefore, a beam expander was used to transform the dye laser probe beam in a thin plane section of 0.2 x 40 mm² dimension. Using a fast intensified charged coupled device for photon detection, three-dimensional number density mapping of ground-state species was possible. The LIF measurements have been calibrated by additional absorption measurements. As a result, a detailed picture of the time- and space evolution of the plasma plume from the target towards the substrate was acquired making in evidence the formation of diatomic reaction products as result of interaction between the ablated material and the ambient gas. In order to outline the different reactivity of nitridation and oxidation processes, measurements have been performed during ablation of aluminum, graphite and titanium targets in either nitrogen or oxygen low-pressure atmospheres. The measured densities of atomic and molecular species were compared to those computed for local thermal equilibrium.

Silica, ITO, chalcogenide glass films and multilayers were deposited by excimer laser ablation deposition. Investigations show that good quality stoichiometric silica films can be deposited on substrates at room temperature by ArF laser ablation of SiO in O₂ atmosphere. Surface roughness can be kept low (approximately 5 nm). Low- absorbance and low resistivity (1.6x10^-6 (Omega) m, the lowest value in literature) ITO films were grown with XeCl laser pulses on substrates heated at 200 degree(s)C. Optical switches were realized with ultra-thin (6-9 nm) ITO films. Rare-earth-doped waveguides were efficiently deposited by ablating Pr³⁺ -doped chalcogenide glass (70%GeS₂-15%Ga₂S₃-15%CsI-2000 ppm Pr³⁺) targets in vacuum (1x10^{-5 Pa} by XeCl laser pulses.

Thermoelectric thin films have been prepared by pulsed laser deposition (PLD) from a Nd:YAG laser. Materials include bismuth (Bi), bismuth telluride (Bi₂Te₃), and lead telluride (PbTe). The influence of various deposition parameters (substrate temperature, substrate nature, ...) On the achievement of high quality stoichiometric films is discussed. Results of transport property measurements (electrical resistivity, thermoelectric power, Hall coefficient) are attempted to be correlated to the film microstructure. Some particular features relevant to each materials (problems of non-congruent transfer of stoichiometry, particular thickness profiles, ...) are highlighted.

Thin films deposited by pulsed laser deposition or reactive pulsed laser deposition are of interest in many key technological applications. However, the main shortcoming remains the presence on their surfaces and inside their volume of particles with various shapes and dimensions. We studied the possible formation and deposition mechanisms in different laser - target material - ambient gas configurations. Our experimental results as well as numerical simulations showed, that the origin of the particulates depends on the specific irradiation conditions, target and/or ambient gas nature and pressure. Therefore, the experimental conditions required for the decreasing of the particulates density or, if possible, for their complete elimination can be optimized for any particular case only. Nevertheless, a major conclusion of our investigations is that an important approach for the decrease of the particulates density, is to avoid the presence of liquid substance within the laser irradiation field.

Thermal stability and intermixing studies are of primary importance for diverse applications of layered structures and multilayers (MLs). Especially if the thickness of layers is in the nm range, MLs are of great interest for diffusion studies because of small diffusion distances and high number of interfaces. In the paper the intermixing measurements with pulsed excimer laser heat processing are discussed. As a representative example the intermixing studies in Co/Ag bilayers and trilayers for giant magnetoresistance structures are reported. The e-beam evaporated samples were heated by XeCl and KrF lasers and they were analyzed by RBS and grazing incidence XRD methods. Diffusion coefficients for different interfaces are characterized by the activation energy of diffusion, being 0.4 eV for a diffusion at solid- solid and 1.5 eV at solid-liquid interfaces, respectively. The effect of back-diffusion was observed in the Co/Ag immiscible combination of elements.

High density plasmas created near a solid surface by a femtosecond laser pulse emit 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 on a metal surface. The minimum pulse duration was < 5 ps. We achieved an approximately 20-fold enhancement of the soft x-ray emission by fabricating an array of nanocylinders on a gold surface. We measured the duration of the soft x-ray emitted from the laser produced plasma by the cross-correlation method using an optical field-induced ionization process in Kr gas. Utilizing a 10-ps soft x-ray pulse, we measured the time- resolved soft x-ray absorption of optically excited silicon near its L_II,III edge. We found that laser-pulse irradiation caused a more than 10% increase in the soft x- ray absorption near the edge, which recovered within 20 ps. From experimental results, we assume the origin of this absorption change to be the bandgap renormalization of Si. We also employed picosecond soft x-rays to measure the spatiotemporal evolution of ablated particles in Al plasma created by a 100-fs laser pulse.

Thin Y₂O₃ films were directly grown on (100) Si substrates by the pulsed laser deposition technique. It has been found by high resolution cross-section transmission electron microscopy, x-ray reflectometry and x-ray photoelectron spectroscopy (XPS) that at the interface between Si and the grown layer, an interfacial layer always formed. Depth-profiling and angle-resolved XPS investigations showed that this layer consists of a mixture of substoichiometric SiO_x(x<2) and the deposited Y₂O₃ layer, without forming an yttrium silicate. The thickness of this interfacial layer depended on the oxygen pressure and temperature used during the deposition. The main oxygen source for its formation is the physiosorbed oxygen which is trapped inside the grown layer during the laser ablation process. When the thickness of this low-k SiO_x was reduced by decreasing the oxygen pressure during laser ablation below the optimum value, a marked degradation of the electrical properties of the structure was noticed.

A number of delta-doped by Sn for a wide range of Sn doping densities structures on vicinal GaAs (001) substrates with a misorientation angle of 3 degree(s) have been prepared using molecular beam epitaxy growth technique. Because of the relatively high segregation ability, Sn, when deposited on the terraces, may accumulate at the step edges and form quasi-one dimensional channels. Magnetotransport, the Shubnikov de Haas (SdH) and the Hall effects, photoluminescence and photoconductivity have been investigated in the temperature range 0.4-300 K. The Hall resisitivity, SdH effect and the magnetoresistance were measured in magnetic fields up to 40 T directed perpendicular or parallel to the plane of the delta-layer. The photoconductivity has been investigated for wavelengths (lambda) equals650-1200nm in the temperature interval Tequals4.2-300 K.

Pulsed laser deposition has been used to prepare films in the Ti- Ni-Zr system. Morphology and structure of the obtained films have been studied as a function of substrate temperature being in the range 25 - 350 degree(s)C. Morphological and structural modifications have been followed by grazing incidence and (theta) -2(theta) X-ray diffraction, transmission, electron diffraction and imaging. Chemical composition has been analysed by electron probe micro- analysis. The in-depth variation of composition has been studied by secondary neutral mass spectroscopy. This study leads to the determination of the best growth temperature giving rise to the known quasicrystalline phase recently discovered in the Ti-Ni-Zr ternary system.

Nitrogen-rich carbon nitride films were prepared by pulse laser deposition (PLD) combined with additional r.f. and hollow cathode discharges on fused silica, stainless steel and silicon substrates. The properties of combination of laser plasma with concentrated r.f. or HC discharges were studied using an optical emission spectroscopy (OES). The composition of the films was measured by WDX method. The transmission spectra and plastic microhardnes of the films were also measured.

We study the processes of glass heating and melting by absorption of laser radiation using profilometry in reflected light and interferometric real time analysis. The sample irradiation is obtained by an argon ion laser and the interference pattern is generated by a He-Ne laser or by another argon ion laser. In the reflected beam we observe a change of the ring pattern caused by the increasing of pumping power. Above a certain level an additional ring pattern appears. We study the dependence of the structure of the ring patterns as function of the power of the pumping laser beam. From the diffraction pattern and the interference pattern given by a wedge shearing interferometer we estimate the shape and dimension of the mound and respectively the dimple generated for different pumping powers.

The results of the experiments the main objective of which was to determine the optimum conditions for the removal of different layers from metal surfaces by the use of CO₂-, Nd-, Cu-laser radiation are presented. Particular attention has been given to the coatings that are typical for nuclear energy plant equipment to be deactivated.

Tin oxide thin films based chemical sensors have been developed by means of laser induced chemical vapor deposition (L-CVD) and pulsed laser deposition (PLD) methods. The chemical composition of sensors was studied by XPS. By these two methods the tin oxide films were deposited at identical chemical chips and the sensitivity to hydrogen was measured and compared. An improvement of the sensitivity by using noble metal catalysts was observed. In addition, the possibility of detection Co, CH₄, SO₂, NO₂ and N₂O gasses on the films deposited by L-CVD technique and to alcohol vapor on the films deposed by PLD was studied.

This paper analyses the objective functions that define the dimensional accuracy in case of laser drilling. The initial experiments were made on a Nd:YAG laser with maximum impulse energy of 60 J, impulse length between 0,5-8 ms, impulse frequency between 1 and 100 Hz. These experiments were made on a sample of stainless F17T steel (0,005% C, 0,35% Si, 0,40% Mn, 16,5% Cr, 9,4 Ti), 2,5 mm thickness. As parametres of the laser drilling were considered the following: the energy of the laser impulse, the impulse length, the working gas, the focal spot position related to the processed object surface and the diameter of used midriff. The analysed objective function were: the deviation from the circularity at the upper surface level of the processed material and a note that testify the quality of the hole processed. Using the STATGRAPHICS program, were established the regression polynoms that define the objective function. A comparative analyse of results obtained by the mathematical model and experimental results is also presented. Using two dimensions and three dimensions graphics, the user can quickly find the optimum value of the required parametres for laser drilling.

Metal oxide thin films have been depositied by reactive pulsed laser ablation of metallic target (titanium, tungsten, zinc) in presence of a 13.5 MHz radio frequency (RF) plasma (10 Pa static atmosphere of O2) using a doubled frequency Nd:YAG laser. The gaseous species were collected in Si(100) substrates positioned in front of the target on a heatable holder (up to 1000 K). The deposited thin films were analyzed by x-ray diffraction (XRD) and scanning electron microscopy (SEM). A laser microprobe mass analyzer (LAMMA), based on a time of flight mass spectrometer, was employed in order to detect cluster ions resulting from the ablation process of some samples previously deposited on suitable quartz substrates. The comparison between conventional pulsed laser deposition (PLD) and the RF plasma-assisted PLD showed the RF plasma influence on the structural characteristics of the thin films.

A flash-lamp pumped Nd:YAG laser with confocal unstable resonator and super-Gaussian output mirror, multi-pulse passively Q- switched employing Cr⁴⁺:YAG and LiF:F₂ crystals with small-signal absorption in the 22-82% range, has been developed. At 49 J energy and 1 Hz repetition rate of the pump pulses, using a passive shutter with 37% initial transmission, a train of 12-13 pulses, separated by more than 8 microseconds, with average 52 mJ single pulse energy and 20 ns pulse-width, were measured. Under these conditions, the laser intensity at the optical fiber input face is under the fiber damage level, but output power density is high enough to reach the ablation threshold of various pollution layers deposited on the material surface.

The KGW thin films doped with Nd were prepared by pulsed laser deposition (PLD) on MgO, YAG and YAP substrates at substrate temperatures (T_s) varied from 400 degree(s)C to 800 degree(s)C in oxygen ambient atmosphere. The influence of the T_s and type of substrate on the film properties including the structure, luminescence and refractive index was studied. The best crystalline structure and strongest fluorescence signal was achieved at higher T_s on YAG substrate.

Experimental study of destructive effect of laser radiation upon rock samples has been carried out. Continuous wave CO₂-laser of LT-1 type with power up to 5 kW was used in experiments. The main objective of the study was to find parameters of rock -laser radiation system for the conditions close to real technological processes of cutting rock slits, removing rock blocks and drilling boreholes. The experiments resulted in quantitative indications for efficient destruction of the rocks (quartzite, sandstone, marble, etc) with powerful laser radiation beam as well as in those for processes of cutting and breaking these rocks. Experiments on surface treatment of different rocks (granite, marble, hassock etc) with laser radiation were also carried out.

In this work a compact electron beam source, a preionized controlled open-ended hollow cathode discharge, is used for the ablation of an anodic target. Time-resolved spectroscopic measurements of the optical emission of the filamentary and plume plasmas, both created by the electron beam, are presented and electron beam parameters are given. These latter are compared to preliminary measurements in a channel-spark.

This investigation deals with determination of optical parameters of thin PLZT films prepared by pulsed laser deposition on fused silica substrates at different oxygen pressure. Film composition and structure are investigated by WDX and XRD. Defects concentration in the films is studied using triboluminescence. Changes of film refractive index n((lambda) ), extinction k((lambda) ) with wavelength in the spectral region 0.3 - 1.1 micrometers and film thickness d are determined as a result of transmittance spectra processing. Waveguiding properties of the films are investigated.

In this paper is proposed a more precise mathematical analytical expression to the propagation solutions along an optical fiber with a dispersion profile adapted to the so called quasi-solitons introduced by Kumar and Hasegawa. An approximation based of variational methods has also been made by C. Pare. The propagation characteristic parameters of these pulses are described by the same propagation law. The concept of quasi-soliton has been recently introduced, as a chirped soliton adapted to a novel dispersion profile. By using a periodic amplification and a grating for chirp reconstruction, the transmission over a long distance is allowed. The mathematical expression of a such quasi-soliton is well defined except its envelope that is described by the eigenfunctions of the following non-linear differential equation: f_xx + (alpha) f³ -(a + bx²)f equals 0 Taking into account that the term (alpha) is much less the others one can try to solve out the following equation: f_xxequals(a+bx²)f.

In the small gain approximation and the unsaturated regime in this paper we report some original results concerning the evaluation of the spectral optical gain, spectral noise figure and signal to noise ratio on the dopant concentration in Er³⁺-doped LiNbO₃ straight waveguide pumped near 1484 nm using erfc, Gaussian and constant profile of the Er³⁺ ions in LiNbO₃ crystal. We used a quasi-two-level model to simulate the optical amplification of Er³⁺-doped LiNbO₃ straight waveguide amplifiers and we demonstrated that high gains (36,12 dB and 39,09 dB for erfc and Gaussian, respectively Er³⁺ - profiles in depth) and low noise figures (16.51 dB and 17.51dB) are achievable for 50 mW input pump power. The obtained results can be used for the design of the integrated optical devices.

The photopyroelectric calorimetry, in the front (inverse) configuration, was applied in order to measure the thermal effusivity of some Brazilianfats. The front configuration with thermally thick sensor and sample, and optically opaque sensor, was used for the first time for analysing the thermal properties of fat products. The information was obtained via a frequency scan of the phase of the pyroelectric signal; the measurement needs no calibration. The main advantage of this configuration on the other two front schemes proposed before is mainly technical: one has not to use very thin foils or expensive semitransparent sensors. On the other hand, the information is contained in the phase of the signal (and not in the amplitude - as usual) which is not dependent on the power fluctuations of the radiation source.

The surface morphology of single crystal (100) Si wafers irradiated by 266 nm and 1064 nm laser pulses emitted by a solid state Nd:YAG laser has been investigated. The morphology of the bottom of craters remained flat and almost featureless after 266 nm single or multipulse laser irradiation up to the maximum fluence of 18 J/cm² used in this study. The rims of the craters showed signs of radial liquid flow but it was apparent that the vaporization process was confined to the surface region. A different morphology was observed on the bottom of the craters formed by the 1064 nm wavelength laser pulses. Because this wavelength is absorbed in volume, (alpha) <10⁴cm^-1, a rather thick liquid Si pool formed at the surface. For laser fluences higher than 3-5 J/cm² evidence of boiling sites were observed on the bottom of the crater, especially for multipulse irradiation. An evolution of surface morphology, from waves towards deep cavity was observed with the increase of pulse number. By analyzing the cavity formation mechanisms, their density and shape, we suggest that they were induced by heterogeneous boiling and not homogeneous boiling.

Plume reflection has been studied as a possibility for depositing on a direction perpendicular to target, convenient for manipulation of big size substrates and for avoiding the presence of droplets on film surface. Plume behaviour during reflection on a 45 degree(s) oriented plane surface has been monitored by a high- speed camera. Thin film, deposited by reflected plume, has been analysed by scanning electron microscopy (SEM) and atomic forces microscopy (AFM). Comparing with a standard deposition a 1-2 order of magnitude improvement for film roughness (RMS) has been noticed at the expense of one order of magnitude diminuation of deposition rate. The results have shown significant dependencies of film thickness and surface quality on plume reflection angle. Some aspects of big particles movement in deposition process are also presented.

In referring to the damage in optical coated components for high power industrial lasers to major factors are important: the absorption coefficient of different layers and local defects acting as heat concentration. Serious damage may occur if overheat of the component develops during exposure to high laser radiation fields. By analyzing the heat diffusion is such structures one may predict the intensity of the laser beam close to the limit value where damages due to the overhead heat may occur. From the thermal point of view, the analysis of heat diffusion in thin films may be useful for using high thermal conductivity or high emissivity thin films for spreading out the heat. The thermal field inside a cylindrical optical component is shown into figure 1. The problem to be addressed at this point is that this analysis involves solving of the heat diffusion equation for the thin films and the substrate, the whole structure appearing as an inhomogeneous structure. The paper presents a new method to analyze the heat diffusion in coated materials by approximating the thermal parameters with constants both for the coating films and for the substrate, and by the first degree polynoms at the interface.

Maxwell-Bloch equations generalized for a dense medium of two- level atoms are used to describe the dynamics of the system under the action of an ultrafast optical pulse. Starting with an uninverted system, the final population is one of the two extreme cases, depending on the ratio of the Rabi frequency and the parameter describing the near dipole-dipole interactions. Based on numerical investigations for typical pulse shapes, the mechanism of switching is explained.

Due to the continuous technological development in microelectronics and generally in precise materials micromachining there is a continuous need to develop more effective techniques to clean impurities from the surface. Current cleaning techniques used in microelectric devices fabrication lines have an integrated action on the whole surface or on a great part of it, are polluting the ambient and are not efficient for submicron particles. Due to this needs we have studied laser cleaning of silicon wafers with regards to direct applications in semiconductor manufacturing. We have analyzed the ablation effect of laser radiation of 1.06 micrometers on different materials currently used in microelectronic industry and the cleaning effect on a silicon support.

The paper presents a syntheses of the last data concerning the optimal parameters of the deposition process to obtain the best dynamic quality of HTS thin films in connection with the most precise dynamic measurement method known to date. The paper makes a comparison between the performances achieved by the classical dynamical surface resistance nondestructive measurement techniques of the HTS laser ablated thin films and the quasi- optical high performances one.

We derive a quantum master equation for a system of femions coupled to the blackbody radiation field and to many other excitations of the surrounding particles. In comparison with other master equations for many-level systems, the new master equation depends on microscopic coefficients (as functions of physical constants, matrix elements, densitie of the environment states, and occupation probabilities of these states), and includes two additional terms: (1) a term depending on the selfconsistent field of the collective motion of the system or of other surrounding particles, and (2) a non-Markovian term.

We report on the reproducible growth of stoichiometric thin films of ferromagnetic intermetallic compound NiMnSb by pulsed laser deposition (PLD) on various substrates. The films are grown at moderate temperature (around 200 degree(s)C) using polycrystalline targets. Two different substrates were employed - single crystalline silicon and InAs polycrystalline - to investigate the influence of the thin layer/substrate lattice mismatch on the quality of the grown film. XRD and EDX analyses indicate that the layers are of high crystalline quality and their stoichiometry is very close to that of the corresponding targets, respectively. SEM images show that there are droplets on the surface of the films and their composition is similar to that of the targets. Magnetic measurements performed at both room temperature and 5K find that the investigated samples have small H_c values.

Laser vaporization (LV) is a remarkably versatile technique for the catalytically-aided synthesis of nanomaterials, such as single-wall carbon nanotubes (SWNT). SWNT show remarkable promise for future generations of electronics and structural materials, however their application and commercialization has been hampered by a lack of control over the synthesis process, and low production quantities. Time-resolved in situ spectroscopic investigations of the laser-vaporization SWNT-synthesis process are described which are yielding some of the first direction determinations of carbon nanotube growth mechanisms and rates necessary to evaluate strategies for controllable synthesis and large-scale production. Our measurements indicate that SWNT grow over extended annealing times during the LV process by the conversion of condensed phase nanoparticle feedstock. These measurements were extended to grow carbon nanotubes by CO₂- laser-annealing heat treatments of carbon and metal nanoparticle mixtures, offering an alternative synthesis approach to vapor- phase methods. These results present opportunities for scaled-up production of nanomaterials compatible with commercial high- power-laser technology.

This lecture gives a general overview ofnew possibilities offered by photonic crystals in nonlinear and ultrafast optics. The abilities of photonic band-gap (PBG) structures to guide and localize light, phase-match nonlinear interactions, and chirp, compress, and switch laser pulses are discussed. Several types of PBG structures allowing photonic band gaps to be produced in one and two dimensions are considered. In particular, the properties of a hollow corrugated planar waveguide formed by a diffraction grating and a mirror are examined, and possible applications ofsuch optical components combining the dispersion of a gas, a waveguide, and a PBG structure are discussed. Holey fibers are shown to substantially enhance nonlinear-optical interactions, increasing the efficiency of spectral broadening of short laser pulses and opening new horizons in optical frequency metrology.

Different laser spectroscopy methods have been utilized to investigate the optical and nonlinear optical properties of semiconductor (GaAs and CdSe) quantum wires with dielectric barriers and porous Si and InP. The results of the measurements have allowed to conclude that exciton transitions dominate in the absorption and luminescence spectra. The binding energy of excitons in these semiconductor-dielectric quantum wires exceeds 100 meE. The dielectric enhancement of the binding energy and oscillator strength of excitons may be explained by the increasing of electron-hole attraction due to the large difference of the semiconductor and dielectric permittivites.

Experimental results are presented related to the nonlinear optical response of silicon nanocomposities embedded in various media such as water, glycerol, polymer and covered by silver in glycerol. As shown, the free silicon nanocomposites exhibit saturable absorption and negative nonlinear refraction and one is covered by silver exhibit reverse saturation absorption.

Nonlinear optical interaction of first and second harmonies of YAG laser in thin layer of high density packed silicon nanocrystals have been investigated. The second harmonic was polarized perpendicular to first. In the experiment the tow color single beam Z-scan technique have been used. The interaction of optical beams with different wavelengths and polarization was observed. Action of first harmonic to the second and vice versa lead to changing the sign of the nonlinear susceptibility coefficients as for first and second harmonics.

The magnetoresistance measurements have been made on the bulk- grown GaAs-n sandwich structures and on Gunn diodes without magnetic cap. The magnetoresistance mobility has been determined by measuring the variation of the active layer resistance in a low magnetic field oriented perpendicular to the electric field direction. For this purpose the metal-semiconductor contact resistance, determined from the structure resistance vs. the magnetic field intensity and the angle between the magnetic field and the electric field, has been used. The resistivity has been obtained from the active layer resistance and the sample geometry. The concentration of charge carriers has been determined from the resistivity and the Hall mobility.

En-face optical coherence tomography (OCT) technology is employed to produce high resolution images from the retina, cornea, skin and teeth. Longitudinal (B-scan) and transversal (C-scan) images are demonstrated using en-face scanning method. The main advantage of the en-face imaging is that the C-scan images permit a straightforward comparison with the images produced by confocal microscopy. Other developments are also presented as the generation of 3D imaging of different tissue using stacks of en- face OCT images collected at different depths.

IMany trace gases can be found in the exhaled breath, some of them giving the possibility of a non invasive diagnosis of related diseases or allowing the monitoring of the disease in the course of its therapy. In the present lecture the principle of medical diagnosis based on the breath analysis will be introduced and the detection of trace gases in exhaled breath by high- resolution molecular spectroscopy in the IR spectral region will be discussed. A number of substrates and the optical systems for their laser detection will be reported. The following laser based experimental systems has been realised in the Molecular Spectroscopy Laboratory in ENEA in Frascati for the analysis of specific substances in the exhaled breath. A tuneable diode laser absorption spectroscopy (TDLAS) appartus for the measurement of ¹³C/¹²C isotopic ratio in carbon dioxide, a TDLAS apparatus for the detection of CH₄ and a CO₂ laser based photoacoustic system to detect trace ethylene at atmospheric pressure. The experimental set-up for each one of the a.m. optical systems will be shown and the related medical applications will be illustrated. The concluding remarks will be focuses on chemical species that are of major interest for medical people today and their diagnostic ability.

Ultra-short laser-radiation has initiated a new era for medical laser applications as well as for laser applications in high- precision material processing. Entirely new prospects, in particular, their use for surgical applications and nano- technology, can be envisioned with ultra-short laser pulses, which are now available from pico- and femto-second laser systems. The development of broadband solid-state gain media opened new possibilities for ultra-short pulse generation. In particular, the development of all-solid-state ultra-short pulse devices promise to make such devices rigged and reduce their cost. Ultra-short laser light offers many advantages, as for instance low thermal damage and the possibility of efficient interaction of light with long wavelengths. Extremely high peak laser intensities, which can be achieved even with commercially available systems (typical values are 10¹⁵w/CM² imply physical mechanisms, which reach beyond the classical model of (multi-) photon absorption as the principal energy transfer process. The consequences, as observed in, however still preliminary applications, result in many obvious advantages as for instance: efficient ablation; 2) minimization of collateral damage; 3) ablation thresholds and rates which are relatively insensitive to tissue type; 4) high control over ablation depth, achievable because only a small amount of tissue is ablated per pulse.

In this paper we report on the biological effects of XeCL laser irradiation on Staphylococcus epidermidis and Escherichia coli. UV interaction with cellular systems is responsible for photochemical, photothermal or photodecomposition processes. When short-wavelength UV radiation strikes biological material, the DNA is damaged causing cell killing, mutagenesis or carcinogenesis. We report on different effects of XeCl laser irradiation on two microbial systems; collection strain of Staphylococcus epidermidis (in suspension) and collection strains of Eschericha coli proficient or deficient in DNA recombination/repair pathways (irradiated on solid surfaces). In S epidermidis the 308 nm radiation can significantly enhanced the proliferation rates. In wild type E. coli cells the radiation did not stimulate the growth rates. Surprisingly, the 308 nm radiation elicited a very strong lethal effect on DNA recombination/repair-defective strains (harbouring the recA56 null mutation), even more pronounced than irradiation with a UV 254 nm germicidal lamp. The unknown mechanism responsible for this biological response is currently under investigation.

The biological effects of the laser radiation emitted by the Nd:YAG laser (second harmonic, wavelength 532 nm /fluence 32 mJ/cm²/pulse duration 6 ns) on the Mycoplasma agalactiae bacterium were studied. The radiation was found to intensify the multiplication of the bacteria irradiated in TRIS buffer (0.125 M), without however affecting the proteinic composition of the cell membrane. When the bacteria were irradiated in their growth medium (PPLO broth) being later cultivated on a solid medium (PPLO agar), the exclusive presence of the atypical colonies (granular and T-like ones) was noticed.

This paper presents a simulation program of the laser - tissue interaction, implemented in Matlab. The simulation is made using Monte Carlo techniques. The program allows the description and analysis of an arbitrary complex three-dimensional tissue structure, described using VRML (Virtual Reality Modeling Language).

The multiparametric physical method for diagnosing of widespread diseases including oncological disease based on Rayleigh light scattering is proposed. There was studied simultaneously dynamic and static parameters of blood plasma proteins. This method is the product of extensive research conducted on a molecular level on the indicative fields of the human body such as blood serum or lymph. Comprehensive measurements at molecular level and determinations of parameters related to these fluids, especially blood serum, have revealed significant differences in the values of certain parameters in patients with oncological diseases and for healthy individuals.

The influence of the cholesterol amount in mixtures with fatty acids, in balance with the action of different external perturbations, is the aim of this paper. Samples were investigated as cells containing thin films in the smectic C liquid crystal state, sandwiched between transparent electrodes. D.c. electric fields, weak laser beams, thermal neutrons flows were applied on the samples and their response was studied.

Here we use a blank recordable compact disk as a diffractive device. A simple model for the disk grating is proposed. After the disk is properly cut, small pieces of it are completely immersed in the liquid of interest. Such a small piece is in fact a single-use reflective grating and we call it removable compact disk grating. Because it's very cheap and, for this reason, easy to remove it, the compact disk grating is a suitable device for contaminating fluids and particularly for human serum. The principle of the method allows to calculate the refractive index of human serum by measuring the angular displacement of the diffracted maxima, or by fringe counting in a grating interferometer.

Several low power medical laser devices were studied. We focused on power, wavelength and beam characteristics (2D and 3D images, point stability, beam profile, gaussian fit and elliptical axis etc). The variation of laser parameters for different time intervals and room temperatures was studied.

The proposal of coherent electromagnetic processes as the engine for biological dynamics and biocommunications suggest that the quantum macroscopic coherent phenomena as Bose condensation and laser threshold could be present in living cells. A possible correlation between environmental primordial cosmic background radiation and Josephson experimental evidence is discussed.