The production of thin films by pulsed laser deposition (PLD) has become a standard method, even though many of the basic processes are not known in detail. The key quantitites are the ablation rate (yield) and the angular distribution of the ablated particles. The starting point for this study is the comparatively simple case of one-component metals rather than metal oxides which in the past have been comprehensively studied. The ablation rate depends primarily on the thermal properties of the metal, in such a way that a low cohesive energy leads to a high ablation rate. The angular distribution of the ablated atoms is important for the uniformity of the film thickness as well as the deposition rate on a substrate. However, if the ablation takes place in a background gas, the angular distribution of collected ablated atoms becomes comparatively broad. Combined diagnostic measurements of dposition rates and ion time-of-flight (TOF) signals have been used to study the dynamics of a laser albation plume in backgound gases. The angluar distribution and the TOF signals exhibit three separate regimes with increasing pressure, a vacuum-like regime, a transition regime with increasing plume broadening and splitting of the ion signal, and at the highest pressures a diffusion-like regime with a broad angular distribution.

The characterization of a plasma plume is a key issue in laser ablation and deposition studies. Combined diagnostic measurements by Optical Emission Spectroscopy (OES), ion time-of-flight (TOF) and Atomic Force Microscopy (AFM) have been used to study the dynamics and composition of laser ablation plume produced during ultrashort laser irradiation of metals and semiconductors, in vacuum. Our results show that, in the laser intensity range of 10¹²-10¹³ W/cm², the process of matter removal results in a plasma plume which is mainly composed of two different populations: atoms and nanoparticles. The nanoparticles dynamics during expansion has been analyzed through their structureless continuum optical emission, while atomic species have been identified by their characterstic emission lines. Atomic force microscopy analysis of the material deposited at room temperature has allowed the characterization of the nanparticles size distribution. In the case of silicon, the presence of a fast ion component emitted non-thermally from the sample surface as a result of the supercritical state induced by the intense ultrashort laser pulse irradiation has been also observed.

We have demonstrated the nanostructure fabrication on the Si surface by a 150 fs, 800 nm femtosecond laser pulse. The nanohole size of about 100 nm can be formed presumably by a near-field optical enhancement effect induced by the particle illumination. The nanohole size is nearly independent of the irradiated pulse number. It is found that the optical enhancement factor was about 7 in this experiment. The hexagonally arrayed nanoholes were fabricated. The diameter of the fabricated nanohole was about 90 nm and the depth was about 9 nm. In addition, using the double pulse fs laser, we demonstrated a low-loss waveguide fabrication in fused silica. A low-optical-loss waveguide is fabricated under the conditions that the first pulse energy and teh second pulse energy in the double pulse mode are 30 jJ and 160 jJ, respectively, nad the pulse time interval is 3 ps. The weak first pulse would act as a pre-conditioner of the fused silica and then the second subsequent pulse effectively induces the uniform refractive index change. This new femtosecond double pulse fabrication technique will be very promising for low-loss photonic device fabrication for photonic networks.

Ion implantation of insulator surfaces offers opportunities to alter many surface properties, both from modifications of the pre-existing structures, to addition of new material and formation of thermodynamically metastable compounds. Optical applications have included production of waveguides, waveguide lasers, SHG waveguides, related devices and surface luminescence. Similarly, metallic implants have found considerable use in the generation of nanoparticles which are used in non-linear optics, or where the metallic nanoparticles are size and material selected to control the wavelength dependence of the reflectivity. In all these cases the initial results of the implantation generates variations in property which change with depth. The complex pattern of change is invariably accompanied by unwanted side effects. For example, for luminescence and laser signals derived from rare earth implants there is unwanted host lattice damage. This lattice damage cannot easily be thermally removed without unwanted clustering of the rare earth ions. Conversely, in metallic nanoparticle usage the clustering is desirable, but the implants form a depth dependent particle size distribution whereas a narrow sie distribution is preferred. Once again simple thermal treatments alone cannot establish the ideal conditions. A major value of laser pulsed annealing is that one can achieve controlled temperature excursions for a sufficiently short time duration that long term diffusion effects can be avoided. Wavelength selectivity can further allow treatment to initially couple energy either to the host or specific types of site. Examples variously include both the removal of damage and/or nanoparticles, and controlled particle growth or precipitation of new crystalline phases. These case studies show that pulse laser anneals can make major modifications in a wide range of properties. Some new experiments are proposed.

Thin films gas sensors based on resistive or optical m-line detection are studied. The focus is on butane detection. Potentially suitable materials for detection are summarized and discussed. Experimental results reached with inorganic and organic layer fabricated by pulsed laser deposition are presented.

Zinc oxide thin films were grown by pulsed laser deposition technique. The ZnO targets were irradiated by an UV KrF* (λ=248 nm, τ_FWHM≈20 ns, v=2 Hz) excimer laser, at 2 J/cm² incident fluence value. We used (001) SiO₂ wafers as substrates, heated during the thin films grown process at temperature values within the range (150-500) °C. The experiments were performed in oxygen pressure at fixed values between 1 and 12 Pa. We investigated the effect of substrate temperature and oxygen presssure on the thin films morphology, crystalline status and optical properties. The thin films surface morphology was investigated by scanning electron microscopy and atomic force microscopy. The crystalline state and chemical composition of the films were investigated by X-ray diffractometry. The optical transmittance measurements were performed with a double beam spectrometer in the 300-1500 nm range. Our results show that the films deposited at oxygen pressure values higher than 10 Pa and substrate temperatures above 300 °C are c-axis oriented. Their average transmission in the visible-infrared spectral region is about 85%, and the corresponding refractive indexes and extinction coefficients are very close to those of the tabulated reference values.

Thin indium oxide (In₂O₃) films were grown on (001) SiO₂ by pulsed laser deposition techniqe at oxygen pressure from 1 to 20 Pa and substrate temperature between 100 and 500 °C from ceramic targets. The structural and optical properties of the films were investigated as a function of the growth conditions: oxygen pressure and substrate temperature. Polycrystalline In₂)O₃ films with prefer3ential (111) orientation were produced at oxygen pressure higher than 5 Pa and temperature higher than 100 °C. The Raman spectra confirm the cubic structure of the films. The films have transparency between 85% and 92% in the 400-2400 nm spectral range. The lowest optical waveguide loss measured is 9 dB/cm for the film grown at the optimum conditions: P(O₂) = 10 Pa and T_s = 300 °C.

Thin TiO₂ films were grown on (001) SiO₂ substrates using excimer KrF laser ablation of ceramic targets. The influence of deposition temperatures at fixed oxygen pressure of 10 Pa on the crystal and optical properties of the films was investigated. Structural characterisation by X-ray diffraction and Raman spectroscopy shows preferential crystallization of the anatase TiO₂ films were obtained at high temperatures of 500 and 600 °C, respectively. Optical transmission as high as 92% in the visible spectral region was measured for films grown at temperatures higher than 400 °C. The refractive index and the thickness of the films measured by m-line spectroscopy shows the highest values of 2/41 and 250 nm, respectively, at deposition temperature of 600 °C.

The Bi₂Te₃ thin films with various thicknesses were prepared by laser ablation in vacuum using the KrF excimer laser. The energy density of laser was set at 5 J/cm² (resp. at 2 J/cm² in the second experiment). The substrate temperature was held at 410 °C. The influence of thickness on the Hall mobility and conductivity at room temperature is presented.

Nd:KGW [or Nd:KGd(WO₄)₂] films are grown using the nozzle-gas-assisted pulsed-laser deposition (NGA-PLD) method. A KrF excimer laser is used for the ablation of K-rich ceramic targets and films are deposited on r-cut sapphire substrates. The dependences of the oxygen nozzle gas on the film optical and crystallographic properties are investigated. The Nd:KGW film is colored if the mass flow is not sufficient. The origin of the color is attributed to the oxygen deficiency phase which is confirmed by the optical absorption and x-ray diffraction (XRD) measurements. Highly crystallized Nd:KGW films are grown by NGA-PLD under the optimized conditions. Comparing the films grown by conventional PLD (C-PLD) method, a dramatic improvement in the film surface morphology is chieved with NGA-PLD.

We report on the results of ultraviolet (UV)-assisted annealing of thin Y₂O₃ films produced by pulsed laser deposition. An excimer XeCl laser was used for ablation of Y₂O₃ ceramic target. The films were grown on (001) SiO₂ substrates at 500 °C and oxygen pressure of 0.05 mbar. The effect of UV-assisted laser annealing on the structure, morphology, and optical properties was investigated. The UV-assisted annealing was performed by the same laser. The beam was directed parallel or toward the surface of the as-deposited films. The influence of the ambient gas (O₂ or N₂O) is explored. The ambient atmosphere has an influence on the preferential (cubic or monoclinic) phase of gowth while it has no significant effect on the surface morphology. The absorption coefficient in the VIS range has a lower value for the films annealed with laser directed parallel to the surface independently on the gas environment. Annealing of the films with laser beam directed at the film surface slightly increases the refractive index, independently of the gas ambient.

Ablation of Fe, Al, Ni, and Cu by laser pulses at durations of 0.1, 1, and 5 ps is investigated experimentally. The laser fluence used vaires from below the ablation threshold up to 100 J/cm². The ablation rate depends on the laser pulse duration at laser fluences above several J/cm² as the shorter pulse produces higher ablation rate. A change of the ablation regime with the laser fluence increase is also observed. The presence of molten material is clearly expressed at fluences above 10 J/cm² for all pulse durations used. These effects can be referred to the contribution of the electron heat diffusion in the distribution of the absorbed energy. The traces of solidified molten material suggest for realizations of melt ejection mechanism of ablation.

The effect of laser cleaning on historical sandstone samples investigated by means of surface techniques SEM and EDX reveals surface damages such as scaling off, cracking of the grains, and even melting of the crust. Also differences in the binder quantities contained in the upper layers are observed. The presence of compounds containing C, Al and F in the dark coverage is confirmed by the EDX data and indicates that the encrustation originates from environmental pollution.

Polymer-dispersed liquid crystals (PDLC) provide the opportunity to achieve reliable, cheap and commercial elements for switchable holographic devices. In the present work holographic recording techniques are used to form switchable gratings in PDLCs. Depending on the initial reactivity of the mixture, Bragg and Raman-Nath gratings are obtained. The first ones show higher efficiency for s-polarization, which does not hold in the case of Raman-Nath gratings Different exposure power of the writing beams results in different diffraction efficiency. The switching characteristics of the recorded gratings are studied. The switch-off state is obtained at about 2V/μm for p-polarization in the first diffracted order in thin (Raman-Nath) gratings. The angular selectivity of these gratings is also investigated. The influence of the reconstructing wave polarization azimuth on the diffraction efficiency is studied.

Polarization multiplexing of holograms in azobenzene polymers has been investigated. The optimal conditions for multiplexing two holograms with teh same spatial frequency in the same volume of the polymer and the same linear polarization of the reference wave have been found. The first hologram is inscribed with two p-polarized waves and the second-with p-polarized reference wave and s-polarized subject wave. The two images can be read simultaneously or separately using a linear analyzer or a polarization beam splitter.

Two coupled nonlinear Schrodinger equations describing propagation of light pulses through nonlinear media with negative cross-phase modulation and different group-velocity dispersion regions for the two polarization modes are considered. Applying a Lie group technique, the most general Lie algebra and the corresponding Lie group of point symmetries permitted by the considered equations are derived. As a result, the optimal set of one-dimensional Lie algebras is obtained.

A set of couled nonlinear equations describing propagation of two polarization light modes inside optical fibers with stimulated Raman scattering are considered. Using a Lie group technique, the most general Lie algebra is derived for the two cases: with and without orthogonal Raman gain. The optimal set of reduced systems of ordinary differential equations for the case without orthogonal Raman gain is obtained.

The mechanism of hydroxyapatite (HA, Ca₁₀(PO₄)₆(OH)₂) growth on the surface of porous silicon (PS) was examined. PS layers were prepared by electrochemical or chemical etching of n-type Si with (111) orientation, and p-type Si with (100) orientation. HA growth was induced by two methods: a simple soaking process in a simulated body fluid (SBF) and a novel Laser-Liquid-Solid Interaction (LLSI) process which allowed interaction between a scanning laser beam and the PS substrate immersed in the SBF. The grown layers were investigated by light microscopy, electron microprobe analysis, Raman spectroscopy and X-ray diffraction. Differently doped Si substrates with different crystallographic orientation and electrical resistivity were used and their effect on the HA growth, as well as the effect of the laser energy were examined.

The role of the ratio of the two design periods for phase reversed QPM structure is theoretically investigated. It is found that the efficiency of third and fourth harmonic generation strongly depends on this ratio. The results for third harmoic generation and fourth harmonic generation in LiTaO3, LiNbO3 and KTP are shown in graphical form.

The emissivities of mixed classes formed by rocks are experimentally investigated and analyzed. In most cases isothermal mixing was registered. The problems arising when measuring the emissivity of mixed classes are discussed.

Experimental results on the micro-hole drilling, hole trepanning and micro-cutting in thin metal foils using both competing lasers: CuBr and Nd:YAG (532 nm) are presented in this paper. The micromachining were carried out in aluminium (150 μm), brass (150 μm), stainless-steel (200 μm) and copper (50 μm) foils. The experiment results shows, that the Nd:YAG laser is more reliable and stable than the CuBr laser when the precision processing of the materials is considered. However the CuBr quasi-tophat beam results in more accurate for material processing than the Nd:YAG laser Gaussian beam.

Streamers induced by a laser beam in DC positive corona discharges seem to be convenient for studying the temporal behaviour of the positive corona streamers, due to an easy controlling of the laser induced streamer onset. However, a question arises if the properties of the laser induced positive corona streamer are similar to those of the regular DC positive corona streamer. To answer that question, we compared images of the laser induced streamers to regular DC corona streamers generated in a nozzle-plane electrode geometry. The images of the laser induced streamers were examined for various laser beam geometries and positioning relative to the nozzle electrode. The results showed that the laser induced corona streamers are very similar to the regular DC corona streamers. This means that the time evolution studies of the laser induced corona streamers can be also representative for the regular DC corona streamers which are more difficult to be temporally resolved.

Storing and cooling simultaneously lithium and sodium atoms in a two-species magneto-optical trap, rate coefficients for collisions between these two atomic species were determined. The experiments were performed at different trap depths, thus for Li atoms the trap losses due to finestructure changing collisions could be distinguished from losses due to radiative escape. The rate coefficient for collisions between sodium and lithium atoms shows also a step when increasing the trap depth. The formation of cold heteronuclear molecules is claimed.

Laser-pumped cesium magnetometers allow highly sensitive small field magnetometry at room temperature. We report on applications of that technique in biomagnetic diagnostics and in a new experiment searching for a neutron electric dipole moment (nEDM) experiment. In the biomagnetic application the magnetiv field from the beating human heart is detected using a gradiometer which reaches an intrinsic sensitvity of 80 fT/Hz^1/2 with a spatial resolution of 28 mm. The device can record time-resolved magnetic field maps above the human body surface and its performance is comparable to devices based on Hi-T_c-SQUID (superconducting quantum interference device) technology. In the nEDM experiment laser-pumped cesium magnetometers will be used to measure and stabilize a DC magnetic field of 2μT and to generate the oscillating filed for the neutron Ramsey resonance. Those devices reach an intrinsic sensitivity of about 14 fT/Hz^1/2 with a measurement bandwidth of 1kHz. The general principle of operation and specific results are presented.

A simple set-up for observation of CPT effect at single hyperfine ground state excitation has been examined for application in measurements of non-vanishing magnetic fields. The CPT is prepared using low-frequency modulated (in the kHz range) diode laser. Magnetic field measurements down to 500 pT sensitivity and reproducibility were obtained for integration time of 30 ms. One of the important characteristics of the proposed methodology is a proper Cs excitation in order to overcome effectively the huperfine optical pumping effefct. This is possible working in narrow ranges of laser beam intensity, buffer gas pressures and Cs vapor densities. The best conditions have been experimentally determined and discussed.

We discuss the basic physical principles of laser optical pumping double-resonance spectroscopy, which form the basis of state-of-the-art vapour-cell atomic frequency standards using laser optical pumping of Rb atoms. The main effects limiting the frequency stability of Rb vapour-cell atomic clocks are identified, and their impact on the development of high-performance frequency standars and their transfer from research laboratories to industry and space is discussed. As examples, the impact of the AC stark effect and the realated issue of laser frequency stabilisation are dealt with in more detail. The main features of the present state-of-the-art Rb atomic frequency standards will be illustrated using the example of the development of atomic clocks for satellite navigation and positioning systems (GPS, GLONAS, GALILEO, etc.) as well as some directions for further improvements that could overcome present day limitations. Such compact Rb clocks find their applications in, for example, telecommunications, local timekeeping and synchronisation, and space applications like satellite navigation and science missions. An overview of other, alternative clock schemes is given and critical issues for future developments towards further performance improvement or device miniaturisation in the field of vapour-cell atomic clocks are discussed.

The purpose of this communication is to summarize and compare the results obtained under the project "New all-optical systems and methods for magnetic and electromagnetic field measurement", financed by EC (contract G6RD-CT-2001-000642). The main aim of the project is investigation of the potential of different approaches based on the effect of Coherent Population Trapping (CPT) for magnetic field measurement. The investigated approaches are: (i) CPT prepared by coupling pairs of non-degenerate Zeeman sublevels belonging to the two ground-state hyperfine components of alkali atoms by means of polychromatic laser field; (ii) CPT prepared by coupling degenerate Zeeman sublevels belonging to a single ground-state hyperfine component of alkali atoms by means of single-frequency laser field of appropriate polarization at zero magnetic field (MF); and (iii) polychromatic laser field coupls pairs of non-degenerate Zeeman sublevels belonging to a single ground-state hyperfine level of alkali atoms.

We have investigated some possibilities to use effect of Electromagnetically Induced Transparency (EIT), which is based on quantum interference, for measuring magnetic fields. Multi-frequency laser light is driving atomic transitions (e.g. in a Λ-type excitation scheme), and the atoms are decaying into a super positional dark state, in which the population is trapped, if the frequencies of the applied light fulfills certain conditions. Then the atomic medium becomes transparent for the exciting electromagnetic fields. The observed line width of this "transparency window" is not limited by the natural line width of the involved optical transitions and can be decreased down to a few hundredths of Hertz. As a consequence, this narrow feature can be used as a sensitive probe if the frequencies fulfill the required conditions, which are dependent on the energy positions of the involved atomic levels. These energy positions are influenced by external magnetic fields, thus the observation of EIT can be used to determine external magnetic fields strengths. In our approach a so called Hanle-configuration is used, where only one laser frequency is used to simultaneously excite σ⁺- and σ^--transitions within a single hyperfine transition of the Rb⁸⁷ D_l-line. In this configuration a resonant Λ-system is formed at zero magnetic field. The detuning from two-photon resonance is caused by a magnetic field scanned in laser propagation direction. Any additional probe magnetic field characteristically changes the width and shape of the EIT transparency window resonance; hence the probe magnetic field can be determined directly from the shape of this resonance.

Magnetic coherence resonance profiles, obtained at magetic field B = O in Hanle configuration were examined for Na and K atoms in different cells: evacuated glass cells and buffered, coated and uncoated. At low laser power for all cells the shape of the resonancees is Lorentzian. At power higher than about 100 mW/cm², some narrowing around the resonance peak is observed for the Na buffered cell, while for the vacuum one the resonance shape is even more complex. Theoretical explanation is proposed for the complex resonance shape evidenced in the vacuum cells. Large resonance contrast in the K absorption at B = 0 is observed, attributed to the low rate of hyperfine optical pumping in K. The detailed investigation of the resonance profiles and contrast is of very high importance for their application.

Electromagnetically induced transparency and absorption is observed in a transmission of the coupling laser, locked to transition between hyperfine levels of the ground and excited states of ⁸⁵Rb. The transmission was monitored in a V, Λ and N-type systems while the probe laser, with similar power as the coupling laser, scans across the hyperfine levels F' of the ²P_3/2. The measured width of the EIT resonance increases with a square-root dependence of laser intensity. The EIA was observed only for a cycling transition and for F' = F+1, where F and F' are the angluar momentum of the hyper-fine levels of the ²S_1/2 and ²P_3/2, respectively. We demonstrated the effect of a three-photon EIA in a four-level scheme that involves the Raman transitions via virtual level.

The investigation of the coherent population trapping (CPT) resonance on the degenerate two-level system of the (F_g=2→F_e=1) transition of the ⁸⁷Rb D₁ line by means of Hanle effect configuration in an uncoated vacuum cell (Opt. Lett. 28, 1817, 2003), has shown that the measured in fluorescence resonance has a complex shape: a very narrow (about 1mG) resonance superimposed on a broader one (about few tens mG). In this work the narrow and wide CPT resonances are registered in fluorescence, transmitted light and Faraday rotation. The dependence of the CPT resonances structures width and amplitude are measured at different laser power densities when the registration was in fluorescence and transmission. While the narrow resonance width doesn't change in the limits of the accuracy of our measurements, the wide resonance width dependence is complex and it is different in fluorescence and transmission. The origin of the observed dependencies and the differences between CPT signals observed in fluorescence and transmission are discussed.

The absorption and fluorescence spectra of a submicron Cs vapour layer under resonant excitation on the D₂ line are measured. Sub-Doppler features centered at the resonance frequency of the hyperfine (hf) transitions have been observed. Substantial changes in the amplitude and width of the sub-Doppler resonances for individual hf transitions were recorded in dependence on the intensity of the incident laser radiation. In the fluorescence spectra narrow dips due to the effects of saturation have been observed. We also report about the observation of coherence resonances in Hanle configuration obtained at cell thickness of the order of the wavelength of the laser light.

In this work we discuss Hanle absorption resonances obtained in a room temperature NO₂ cell, irradiated by a single mode Ar+ laser. The method used is based on measuring the changes of polarization of the transmitted laser beam crossing the NO₂ cell, placed in a transverse magnetic field. The resonant changes in the measured absorption signal, that occur in the magnetic field, could be explained as destruction of the alignment of the absorbing rotational state(s), belonging to the ground state (0,0,0) X²A₁. The observed signal is described as a sum, taken over all F'_u and F"_g values, for the chosen N",J"→N',J' transition. The numerical calculations show, that despite the contributions of terms with different signs, the total signal for all examined cases preserves its sign, the determining role being played by the most intensive hf components. Thus a confirmation of Chaika's hypothesis for creation of NO₂ ground state levels (self)alignment is obtained as well an estimation of the effective life time for coherences τ(2).

We experimentally generate optical vortices in the output beam of a Ti:sapphire laser emitting 20-fs pulses. Screw phase dislocations are imposed in each spectral component of the short pulses by aligning computer generated hologram within a 4f-setup. The analysis shows that phase dislocations can be generated also at the stage of femtosecond pluse compression.

In this work we present extended numerical simulation on the evolution and interaction of one-dimensional dark beams of finite length carrying mixed phase dislocations. In the linear regime of propagation two possible ways to control their transverse velocities are investigated and compared.

We analytically show the non-locality of cubic nonlinear media causes an increase of the critical power for self- and induced focusing and influences the condition for signal beam attraction/repulsion in an off-axis geometry.

Experimental transition probabilities for lines arising from 4d⁹ 6s, 4d⁹ 5d configurations of Ag II spectrum and from 3d⁹ 4d configuration of CuII spectrum were determined from measurements of emission-line intensities in a laser produced plasma. Theoretical calculations of the transition probabilities of these lines were made by HF method with relativistic effects and core polarization taking into account. Absolute transition probabilites were obtained by measured branching ratio and theoretical and data for radiative lifetimes. A comparison of the present results with the available theoretical and experimental values was made.

Laser Induced Breakdown Spectroscopy (LIBS) is a one of the successfully used technique for measuring experimental atomic and ionic transition probabilities. This is due to the excitation procedure easily provides highly ionised species and neutral atoms. Nevertheless, its range also extends to another applications such as the industry or in astrophysics. In this work, we explain a specific experimental set-up -consist of fomred by a Nd:YAG laser and grating monochromator coupled with a time-resolved optical multichannel analyser. The employment of the time and spatial spectroscopy in a laser produced plasma for obtaining transition probabilities is also described. From the laser produced plasmas it is also possible to determine some of their properties such as the temperature or the composition. Besides, due to the high emission and temperature, it can be proved the existence of Local Thermodynamic Equilibrium allows determination of absolute values for the transition probabilities and the evaluation of some characteristics such as the self-absorption. The experimental data treatment for obtaining the transition probabilities and the different plasma properties that can be derived was explained.

We describe a modification of the inverted perturbation approach method allowing to construct physically sensible potential energy curves for electronic states of diatomic molecules even when some parts of the potential are not adequately characterized by the experimental data. The method is based on a simple regularization procedure, imposing an additional constraint on the constructed potential curve. In the present work it is applied to the double minimum 4¹Σ⁺_u state of Na₂, observed experimentally by polarization labeling spectroscopy technique.

Transitions to near asymptotic levels of the a³Σ⁺ and the X¹Σ⁺ electronic states in NaRb were recorded by high resolution Fourier transform spectroscopy technique. The hyperfine splitting of the a³Σ⁺ state levels was analysed. The application of coupled channels calculations is discussed for determination of accurate potential energy curves of the a³Σ⁺ and the X¹Σ⁺ states capable for reliable description of cold collisions between a Na and a Rb atoms in their ground states.

The supersonic beam method combined with techniques of laser spectroscopy has been used for determination of the excited-state interatomic potentials of the heteronuclear CdRg (Rg=rare gas: Ar and Kr) and homonuclear Zn₂ van der Waals (vdW) molecules. In the experiments, the CdRg or Zn₂ molecules were produced in a free-jet supersonic beam. The dimers were excited with a dye-laser beam in a vacuum chamber and the resulting total fluorescence emitted perpendicularly to the direction of the molecular and laser beams was recorded with a photomultiplier. Unstructured bound-free profiles in the CdRg that were first-time detected in the excitation at D¹0⁺(¹Σ⁺)←X¹0⁺(¹Σ⁺) transition as well as well-resolved bound-bound vibrational transitions in the Zn₂ detected at the ³0⁺_u(³Π_u)←X¹0⁺_g(¹Σ⁺_g transition are presented. Analysis of the bound-free excitation spectra yielded information on the repulsive wall of the D¹0⁺-state potential in CdAr and CdKr, whereas analysis of the bound-bound excitation spectra lead to the determination of the ³0⁺_u-state potential parameters in Zn₂.

The high resolution Doppler-free resonance-enhanced two-photon ionization (R2PI) spectroscopy with mass selection of jet-cooled (2-12 K) molecular species is a powerful experimental method providing comprehensive information on both isolated molecules and molecular clusters. We have demonstrated for the first time that this technique can be applied to large molecules and provides detailed information on their conformational structure. It allows rotationally resolved (FWHM = 70 MHz) spectra of the vibronic bands of the S₁←S₀ electronic transition of the studied molecular systems to be measured. A specially designed computer-assisted fitting routine based on genetic algorithms is used to determine their rotational constants in the ground and excited electronic states, respectively, and the transition moment ratio. To interpret the experimental information and to discriminate and unambiguously assign the observed approach to the study of the neurotransmitter molecule, ephedrine. The results elucidate the role of the intramolecular hydrogen bonds stabilizing the respective conformations and affecting their intrinsic properties.

Previous studies of OH stretching band of aqueous solutions of short poly(oxyethylene)s POEs showed similarities between ratios R of the intensities of the component around 3200 cm^-1 (the collective in-phase OH stretching vibrations of hydrogen-bonded aggregates) and the component around 3400 cm^-1 (the out of phase OH stretches) in dependence on type and concentration of dissolved POEs. According to previous studies on C₁E_nE₁ (n=1-4) the intensity ratio R is characterized with two minima. We observed the same behavior in the case of C₂E₂C₂. In addition the perfect match of the spectra of C₂E₂C₂ and those of C₁E_nE₁ (n=1-4) at different concentration showed that the water structure is influenced in a similar way in the case of C₂E₂C₂ and of C₁E_nC₁.

Two different channels for He₂ excited molecule formation in a low temperature plasma are studied: recombinations of molecular ion He₂⁺ and collisions of excited Helium atom with two normal atoms. Rate constants for the second processes is estimated as k₃≈0.5 10^-30 cm⁶s^-1. Different role of two processes in the active phase of plasma excitation and in afterglow is shown.

For the first time, the process of charge exchange of Helium mucleus on the metastable Helium atom was observed. The process was detected by the analysis of HeII line afterglow excited in recombination of doubly ionized atoms with slow electrons in plasma formed by electron beam. The kinetic equations set for the most populated states of atom and ion was formulated. Solution of the set provides the satisfactory accuracy of the description of population dependence on time in the afterglow and permitted to determine the absolute value of the charge exchange rate constant. The measured value was compared with theoretical estimates and a good agreement between them was found.

Ground state copper vapour number density, sputtered from the cathode of an experimental pseudospark switch is measured in the main gap region, using laser-influenced fluorescence (LIF) from the copper transition 4²P_3/2-4²D_5/2 at 510.55 nm. The presented results are for pre-breakdown duration of 5 μs and lie in the range 4.5•10¹⁶-6•10¹⁷ m^-3. The density is determined from the LIF signal by using both its maximum and integral. This approach follows from an otherwise familiar LIF model, which is examined in detail to reveal an unnoticed feature, namely the possibility to obtain an estimate of the lifetime of the laser excited level. A comparison between this estimate and the lifetime, measured from the exponential decay of the LIF signal reveals a good agreement.

Ground state copper vapour number density is measured with laser-induced fluorescence (LIF) in an experimental pseudospark switch, which allows optical access in the main gap region. The densities for the four buffer gases-hydrogen, helium, neon and argon-are in the range 6•10¹⁶-2•10¹⁸ m^-3. The sputtering yield for the corresponding buffer gas ion with energy 50 eV is in the interval 0.1-0.7. Estimation of the power density, deposited to the cathode by ion bombardment in typical pseudospark conditions, using the measured number densities of the sputtered particle, as well as those of the buffer gas atoms at 20 Pa, indicates that the cathode heating is below the melting temperature. This fact leads to the conclusion, that the observed superemissive glow in pseudospark is due to an arc-like process with participation of multiple, homogenously distributed cathode spots, rather than a field enhanced thermionic emission, as previously thought.

We studied the extension of LIFT method to the deposition of Cr thin film in the nanosecond regime. The major objective was to perform high-speed visualisation of the different phenomena involved in LIFT process using a CCD camera. The Cr thin films (40 nm thickness), previously deposited on glass substrates by a conventional technique, were irradiated by a SPECTRA PHYSICS 2ω Nd:YAG laser (λ=532 nm, τ=7ns, 500mJ/pulse, 10Hz). The dynamics of the plume was monitored using a CCD camera. Photos were taken at different delay times after laser irradiation. The timing of both the laser pulse and the gate opening of the CCD camera was controlled by a programmable pulse generator. For plasma visualization we have set the gate width at 5 ns.

We have characterized teh spectral properties and wavelength tuning behaviour of different types of diode lasers in order to evaluate their potential for applications in atomic spectroscopy and precision instruments. Here we report on studies of recently developed distributed feedback (DFB) and Fabry-Perot laser diodes, emitting around 780 and 795 nm, in solitary operation as well as in an extended-cavity configuration. In solitary operation both types of laser studied show continuous tuning ranges beyond 40 GHz and single-mode emission linewidths around 6 MHz, which makes them interesting candidates for use in high-precision instruments based on atomic spectroscopy such as atomic frequency standards and atomic magnetometers.

We have demonstrated that the frequency of the laser radiation can be stabilized by controlling its coherence properties. Theoretical analysis of the laser radiation visibility function was performed and connection with the longitudinal mode structure was established. It was established that laser emission frequency could be stabilized by controlling the visibility of interference pattern. Calculations have shown that, in theory, stability around 4 kHz can be expected. As a proof-of-the-principle, a HeNe laser, stabilized by measurement of the interference pattern visibility in a modified Mechelson interferometer, was built. Stabilization was performed by temperature control of the laser tube in a digital feedback loop and total frequency variation of 3 MHz was obtained. Possible improvements of the experimental setup, together with some applications of multimode stabilized lasers are discussed.

By the method of saturation absorption of counterpropagating light waves, the gas-phase spectrum of SiF₄ is obtained without Doppler broadening of spectral lines. In the frequency range of the generation of a low-pressure CO₂ laser (the 9.4-μm band), multplets of the superfine structure (associated with tunneling transitions between the states of rotation about the equivalent symmetry axes of the SiF₄ molecule) of the spectrum were observed. Weak satellites were observed in the vicinity of the multiplets.

Information about atmospheric variables, such as presence and characteristics of supended particulates (aerosols), concentration of chemical species, humidity, temperature, etc., can be obtained remotely in an energetic-efficient manner from radiation produced by optical sources and backscattered by the atmosphere, drawing on the relatively strong interaction between electromagnetic radiation at optical wavelengths and particulates and molecules in the atmosphere. Atmospheric probing systems based on laser sources can provide information as a function of range and, being their operating principle essentially the same as that of radar (except for the fact that in atmospheric probing the target is by definiti8on the atmosphere zone illuminated by the laser, instead of a hard target), they are usually called laser radars or lidars (from Light Detection And Ranging). In addition to their ability to perform remote measurements- a characteristic that they share with other systems-lidars feature the availability of quasi-real-time data, high spatial resolution and a relative convenience to perform three-dimensional scans of the atmospheric volume under study. Basic lidar principles and capabilities are discussed in this work.

The application of the Raman lidar technique for the measurement of water vapor, temperature, and aerosols is described. The basic equations and system features are presented and measurement examples are shown.

We have explored a multi (dual))-wavelength Raman-lidar observation of tropospheric aerosols and clouds at Tokyo University of Marine Science and Technology (TUMST) in Tokyo, Japan since the February of 2002. Here we present the results on lofted Asian dust and Siberian forest-fire smoke plumes occured in the spring of 2003. The Asian-dust layer shows that the particle depolarization ratio (PDR) at 532 nm is higher than -20%, and the extinction-to-backscatter ratio (lidar ratio) at 355 nm is ~49 sr, which is close to that at 532 nm of ~43 sr. On the contrary, the smoke layers show that the PDR is lower than ~10% or less, and the lidar ratio at 355 nm is ~40 sr, which is considerably lower that that at 532 nm of ~65 sr. We also applied an inversion algorithm for the smoke case. The effective radius and the single-scattering albedo were found as ~0.22μm and ~0.95 at 532 nm. These microphysical results are consistent with the ones retrieved from the collocated skyradiometer analysis. We also estimated the aerosol radiative forcing for the smoke case using the radiative transfer code with these height-resolved microphysical properties.

A novel method for acquisition and preprocessing of intensive, highly dynamic lidar signals has been developed and tested with computer simulations. The method is based on the time-resolved counting of photon streams by convolving of photoevents into decayed oscillations, linear analog to digital sampling and deconvolution. It is effective simultaneously in analog, overlapped and photon counting regimes, saving the dynamics and the temporal resolution of lidar data for more than four orders (10⁴) of the illumination magnitude.

The influence is simulated of the atmospheric turbulent motion on the character and the accuracy of the radial velocity profiles recovered by using a high-range-resolution coherent-Doppler-lidar approach we have developed recently. The simulations are based on an original statistical spatio-temporal model of the turbulent radial-velocity fluctuations supposed to have a von-Karman-like spectrum that closely approximates the well-known Kolmogorov-Obulkhov spectrum. The results from the simulations confirm the basic conclusions we have analytically deduced formerly about the character of the recovered radial velocity profiles, depending on the duration of the lidar measurement procedure. In this way the model adequacy is also substantiated.

The observations were carried out on August 11, 1999, during the solar eclipse over Bulgaria, using a lidar, an ozone meter, and ground meteorological stations. The lidar was used to measure the height of the mixing layer, in particular, before, during and after the solar eclipse in the Sofia city. The ozonemeter measured the ground ozone concentration during the phenomenon. The ground meteorological stations took the meteorological parameters of the atmopsheric ground layer. The weather conditions in all the regions (Sofia, Shabla, Ahtopol, and Peak Rozhen) were favourable for observation. The data of the three types of measurements demonstrate with certainty that the solar eclipse affects the meteorological parameters of the atmosphere near the ground, the ozone concentration, and the height of the mixing layer. It was found out that a certain time delay exists of the solar eclipse impact on the meteorological parameters, the ozone concentration and the mixing layer height, which was different for the different parameters.

This paper presents a study of the role of direct O₃-rich stratospheric intrusions in the high ozone episodes observed near the ground. The close analysis of the experimental data and the criteria characterizing the intrusion events shows that stratsopheric air injections can contribute to the spring-time ozone maximum and that during summer time the peak surface ozone concentration can have not only a photochemical origin (which is usally associated with local or regional anthropogenic ozone precursor pollution) but also and a stratospheric origin.

We report the application of a pulsed distributed feedback (DFB) quantum cascade laser (QCL) for a 6 km long open path spectroscopic monitoring of ozone, ammonia, water vapor and carbon dioxide. The thermal chirp during a 200 ns long excitation pulse is used for fast wavelength scanning of about 1 cm^-1 in the spectral range 1043-1049 cm^-1. This tuning method has the advantage of not being affected by the atmospheric turbulence, which is essential for long open path measurements. The intrinsic haze immunity of mid IR laser sources is an additional important advantage of mid-IR open path spectroscopy, compared with standard UV-visible DOAS. The third major advantage of the method reported is the possibility to measure many more organic and inorganic atmospheric species compared to the UV-visible DOAS. The obtained sensitivity for ozone and ammonia of the order of 10 ppm.m retrieved from the absorption spectra for averaging times less than 1 min are comparable with teh UV DOAS values. The open path of 6 km is covered using average laser power of less than 0.2 mW, which shows much higher efficiency of spectroscopy using narrowband laser source, compared to broadband light as Xe lamp.

The LIDAR virtual system represents an interactive software instrument able to optimize the configuration process of a LIDAR installation, but also to represent a virtual environment for modeling studies of the (for) atmospherical processes. With a virtual LIDAR is chooses an optimal configuration before the LIDAR installaiton construction, which is very important if (it takes) the high costs of a functional LIDAR installation are taken into account. The paper describes the analytic model used to characterize the emission, propagation and reception processes, and a description concerning the system components programming and the graphic interface realization of a LIDAR virtual system.

The increasing use of lasers in biomedical research and clinical praxis leads to the development and application of new, non-invasive, therapeutic, surgical and diagnostic techniques. In laser surgery, the theory of ablation dictates that pulsed mid-infrared laser beams exhibit strong absorption by soft and hard tissues, restricting residual thermal damage to a minimum zone. Therefore, the development of high quality 3 μm lasers is considered to be an alternative for precise laser ablation of tissue. Among them are the high quality oscillator-two stages amplifier lasers developed, which will be described in this article. The beam quality delivered by these lasers to the biological tissue is of great importance in cutting and ablating operations. As the precision of the ablation is increased, the cutting laser interventions could well move to the microsurgery field. Recently, the combination of a laser scalpel with an optical trapping device, under microscopy control, is becoming increasingly important. Optical manipulation of microscopic particles by focused laser beams, is now widely used as a powerful tool for 'non-contact' micromanipulation of cells and organelles. Several laser sources are employed for trapping and varying laser powers are used in a broad range of applications of optical tweezers. For most of the lasers used, the focal spot of the trapping beam is of the order of a micron. As the trapped objects can vary in size from hundreds of nanometres to hundreds of microns, the technique has recently invaded in to the nanocosomos of genes and molecules. However, the use of optical trapping for quantitative research into biophysical processes requires accurate calculation of the optical forces and torques acting within the trap. The research and development efforts towards a mid-IR microbeam laser system, the design and realization efforts towards a visible laser trapping system and the first results obtained using a relatively new calibration method to calculate the forces experienced in the optical trap are discussed in detail in the following.

Optical tweezers use the gradient force created by tightly focused single laser beam to trap dielectric microparticles. While this technique has been used for over 20 years to manipulate particles without mechanical contact, it is only recently htat accurate and quantitative photonic forces measurements have been considered. Moreover of great relevance has resulted the monitoring of Brownian motion of particles confined in optical traps since that provides precious information on local visco-elastic properties of the surrounding fluid. In this work we consider the still open question concerning the calibration of an optical tweezers which represents the key point for any absolute measurements. In particular, we discuss a novel method to calibrate a quadrant photodiode used as sensor position in the forward scattering scheme. The voltage signals provided by the qudrant photodiode are converted in length units by comparing them with the absolute bead positions measured by means of a calibrated CCD camera. Finally we briefly discuss how calibrated optical tweezers, combined with thermal analysis of the Brownian motion, are potentially of great relevance for microrheological studies of complex fluids.

Phthalocyanines and porphyrins are 18 π-electron aromatic macrocycles that possess singular optical properties. They were shown to be extremely efficient organic compounds in the fields of photodynamic therapy and optical limiting. This short review intends to give a short overview from the basic principles to the newest findings of phthalocyanines and derivatives in these two health-related research fields.

We use the Support Vector Machine method to distinguish fluorescence spectra obtained from demineralized teeth from those obtained from healthy teeth. We find intervals of values for the various parameters of the algorithm, such as dimension, degree of smoothness, etc, as to achieve at least 90% diagnostic accuracy. We argue that the success of the methodology is determined by its multidimensional nature.

The goals of this work were investigation of pigmented skin lesions by the method of laser-induced fluorescence spectroscopy. Fluorescence spectra were obtained from malignant and benign skin lesions after excitation with nitrogen laser at 337 nm, namely: benign nevi, dysplastic nevi, malignant melanoma (MM), keratopapilloma, base-cell papilloma and base-cell carcinoma, as well as from healthy skin areas near to the lesion that were used posteriori to reveal changes between healthy and lesion skin spectra. Initially lesions were classified by ABCD-dermatscopic method. All suspicious lesions were excised and were investigated histologically. Spectrum of healthy skin consists of one main maximum at 470-500 nm spectral region and secondary maxima at in the regions round 400 and 440 nm. In the cases of nevi and melanoma significant decrease of fluorescence intensity, which correlated with the type of pigment lesion was observed. This reduction of the signal is related to the accumulation of melanin in the lesions that re-absorb strongly the fluorescence from native skin fluorophores in whole visible spectral region. In cases of papilloma and base-cell carcinoma an intensity decrease was also observed, related to accumulation of pigments in these cutaneous lesions. An relative increase of the fluorescence peak at 440 nm were registered in the case of base-cell carcinoma, and appearance of green fluorescence, related to increase of keratin content in benign papilloma lesions were detected. The results, obtained in this investigation of the different pigment lesions could be used for better comprehension of the skin optical properties. The fluorescence spectroscopy of the human skin are very prominent for early diagnosis and differentiation of cutaneous diseases and gives a wide range of possibilities related to real-time determination of existing pathological condition.

The easy and non-destructive fluorescence method for quantification of early changes in biological tissues improves the possibilities of the clinical research and diagnostics. Developments in this area are moving very rapidly in part because of advances in the technology and in part because of the numerous successful examples which are appearing. New family of photomultiplier tubes with a high detection sensitivity for near-infra red light (700-900 nm) were developed as a result of project IMPECABLE, which are valuable tools for early diagnosis of cutaneous pigmented melanoma using long-wave fluorescence dyes. Several phthalocyanines that are promising fluorophores for photodiagnosis of cutaneous malignant melanoma have been studied in different solvents for concentrations from 10^-5 to 10^-15 mol. Argon pumped dye laser as an excitation source was used. Three different wavelengths (613, 633 and 660 nm) in the red region, corresponding to first absorption peak, minimum of the absorption and near to the Q-band maximum of Pcs were applied. Fluorescence signals in the region of 700 to 800 nm were detected using spectrometric systems (Perkin-Elmer, UK-with conventional PMT as a detector, and PC2000, Ocean Optics, USA-with CCD-array as a detector) and a newly developed red-sensitive PMT. Detectable signal from other spectrometric systems was obtain up to 10^-8 mol concentrations, which could be used for significant reduction of concentrations applied for in vivo applications. Fluorescence is a highly sensitive method of distinguishing between healthy and unhealthy tissue. The results demonstrate that extremely low concentrations of photosensitizers could be used to determine initial stages of melanoma. This application of PMT detectors will reduce extremely the negative side effects of higher concentrations of these drugs applied in the skin tissue. One can achieve high accuracy in the determination of pigmented malignant melanoma lesions with wide clinical applications.

In this study we evaluate in vitro the cytotoxic activity of two newly synthesized phthalocyanines (metallo-complexes) with absorption bands in the red part of the spectrum: zinc-tri-sulphonated phthalocyanine (ZnS₄Pc). Two permanent animal tumor cell lines are used in the experiments: LSR-SF(SR)-transplantable sarcoma in rat induced by Rous sarcoma virus strain Schmidt-Ruppin and LSCC-SF(Mc29)-transplantable chicken hepatoma induced by the myelocytomatosis virus Mc29. Irradiation has been performed with a laser diode emitting at 672 nm in a wide range of radiant exposure (2-100 J/cm²) and irradiance of 120 mW/cm². The neutral red uptake cytotoxicity assay has been used to evaluate the effect of the photosensitizers on cell viability. The light dose-response curves and light exposures that ensure viability drop to 50% and 10% have been obtained for each cell line. The ability of the compounds to induce apoptosis has been determined by acridine orange dye staining.

One of the mechanisms of influence of laser radiation on the biological tissue is photodissociation of oxyhemoglobin with releasing of molecular oxygen, thus decreasing the degree of blood oxygen saturation. The experimental study of oxygen saturation of arterial blood under laser action is based on the registration of small variations of the saturation value on the background of the natural saturation oscillations. While the determination of the value of oxygen saturation allows to observe respiratory processes, the value of venous saturation allows to determine the dynamics and efficiency of the oxygen absorption in tissues, as well as the condition of venous vessels. The tissue and vein oxygen saturation have not been studied sufficiently so far. The simlutaneous control of arterial and tissue saturation values will give opportunity to study the oxygen supply processes. The aims of this work are experimental study of laser induced photodissociation of oxyhemoglobin and determination of the dependence between the saturation value and the laser parameters. This will allow to develop new methods of control, as well as to realized a feedback during laser therapy.

A new approach to carbon monoxide poisoning treatment based on laser-induced photodissociation of the carboxyhemoglobin is proposed. Using the simple model of laser tissue interaction the action spectra of laser radiation on carboxyhemoglobin of cutaneous blood vessels has been calculated. The results of the calculatoins indicate that there is a relatively narrow spectral range in the visible region where one could effectively irradiate carboxyhemoglobin through the tissue not in a deep distances. In the case of deeper penetration, the action spectra of laser radiation shifts toward the longer wavelength region. Despite the similarity of the carboxyhemoglobin and oxyhemoglobin action spectra, the significant difference in quantum yields of photodissociation makes possible to develop an effective method of carbon monoxide poisoning treatment.

Hydroxyapatite (HA) is present in the human body as a mineral constituent of the bones and teeth, as well as a major or minor component of kidney stones. HA deposited on different solid substrates can find applications including biomaterials and biosensors. This work deals with the kinetics of the HA growth by applying a novel method of laser-liquid-solid-interaction (LLSI) process on three types of materials (stainless stell, silicon and silica glass). The method allows interaction between a pulsed laser and a substrate immersed in a solution (simulated body fluid, SBF). By a scanning system, a design of seven squares at a distance of 200 μm was created at the end of each sample. In this way the center of the substrate (about 6x6 mm) was no irradiated. Following the LLSI process, the samples were left in the irradiated SBF for various intervals of time. Light microscopy (LM) showed surfaces seede with randomly distributed transparent and white particles. The surface seeding increased with the immersion time and was dependent on the substrate type. Fourier transform infrared (FTIR) spectrsocopy showed that in the first stage of soaking (up to 6 h) the observed white particles were calcium phosphate containing. Energy dispersive X-ray (EDX) spectrsocopy revealed that the transparent particles were NaCl. In the next stage (after 12 h) vibrational modes typical for HA were clearly observed. Detailed observation with scanning electron microscopy (SEM) after 12 h showed morphology of sphere-like aggregates, grouped in a porous network. Raman spectroscopy, X-ray diffraction (XRD) and EDX confirmed that after 12 h the grown layer was HA. It was found that in comparison to the traditionally empoyed prolonged soaking in SBF, the applied LLSI process yielded a synergistic effect due to the simultaneous use of the solid substrate, the aqueous solution and the laser energy.

This study discusses the possibility for a quantitative evaluation of pectin macromolecules bydratation, by measuring the refractive index (RI) of their solutions, using a differential laser refractometer and a laboratory-type interferometer, LI-3, Rayleigh-type. The results obtained have been discussed according to the theory of Ikegami for polyelectrolytes hydratation. Refractometer measurements of ethanol, methanol and water have been done. A theroretical link between the models of Selmeyerand Lorentz-Lorenz has been established, and by means of this link the number of electrons per volume unit of the alcohols indicated has been calculated.

This work reports on a systematic study of volumetric energy deposition in tissues for irradiation by a converging laser beam in the vicinity of the beam geometric focal point as a function of beam parameters (diameter, light cone angle) and tissue optical properties (scattering and absorption coefficients, anisotropy factor, refractive index). The task is solved by 3-D Monte-Carlo simulation using variance-reduction Monte-Carlo code and delta-scattering technique for the case of homogeneous and two-layered tissue models at typical for the low level laser therapy operating wavelengths. Efficiency of energy delivery is evaluated at increasing depth of teh focal point location under the tissue.

The process of medical unconventional diagnosis is started by the user through a search process of appearance of some possible areas of abnormal temperatures which can be seen on a suitable monitor and the comparison of these areas with the unaffected ones. To guarantee an increased successful of this search process is necessary that the system design to take into account those displaying modalities of thermal images in order to highlight critical areas. These areas are all the more so full of information as: calibration of the system is more strictly achieved; image is rather well-defined, both geometrical and thermal (through depth and colour conversions). The present paper is made up as a contribution to the existing methodologies in calibration process of such a system. The authors leave from the reason that the existence of a set of calibration filters can contribute with sufficient data which can compensate the inherent errors cam e out by the use of a blackbody source at different temperatures necessry to calibration. Starting from the reasons mentioned above can be demonstrated that is sufficient to have a source constant temperature for the assurance of a strictly calibration.

Cartilage is a specialized tissue, which serves as a load-bearing structure. Its main components are: 70% water, 10-20% collagen fibers, 5-10% proteoglycans, 5%-chondrocytes. When bent, cartilage exhibits its property of shape memorization. Laser radiation may be used to change the shape of cartilage by heating of mechanically deformed specimen. The high water percentage in the cartilage, which determines its mechanical properties, raises the question of whether the medium in which the sample is placed influences the process of relaxation, connected with cartilage water losses. Using Nd:YAG laser (λ=1.32 μm), cartilage samples were irradiated. The stress relaxation time, the surface temperature during irradiation and the time dependence of the backscattered light intensity (which is indication for changes in the internal stress), were compared. The shape retention was measured by comparing the curvature before and after irradiation. Overbending of specimens was done in order to achieve the required angle. The obtained data could be used for development of clinical methods for correction or transplantation of injured human cartilage due to trauma or certain diseases.

In this paper, thin films of some fatty acids and fatty acid-cholesterol mixtures were investigated as biological membrane simple models, in order to establish the thermal neutron irradiation influence on these systems, while in the smectic C liquid crystal state. Samples are nonlinear dielectrics with a weak conduction, and nonlinear optical media. They generally present some memore effects. Cholesterol modifies these properties depending on its percentage in mixture and saturated or unsaturated character of the acid. After exposed to a flow of thermal neutrons, texture and behavioral changes, in terms of content of cholesterol in mixtures, and depending on the number of carbon atoms, were emphasized.

The work presents a cosmetic CuBr laser system for treatment of various cutaneous vascular malformations and pigmented lesions with output power 3 W at 578.2 nm and 6 W at 511 nm. The system is provided with a fiberoptic delivery system and a hand-piece, which forms a convergent beam with a diameter of the laser spot 0.4 mm in the focal plane. A built-in CPU sets and controls all operational modes by using an intracavity polychromatic acousto-optic modulator or a mechanical shutter. The laser irradiation can be emitted within a preset temporal interval with variable duration from 15 to 950 ms. The controllable interval for thermal relaxation of the irradiated tissue can be varied from 20 to 1000 ms. The controllable radiant exposures vary from 5 to 100 J/cm² for the yellow light and from 10 to 100 J/cm² for the green light. A 3D Monte-Carlo modeling has been used to compare the volumetric energy deposition at 532, 578.c2 and 585 nm. The model simulates photon migration for the case of embedded cylindrical small blood vessels of varying size, which are randomly distributed within a skin layer at different depths. To simplify the task, the vessels were modelel as paralles to each other and to the tissue surface. Optical properties (absorption coefficient, scattering coefficient, anisotropy factor, and index of refraction) of epidermal tissue, dermis and blood were chosen from the literature.

The Nd:YAG solid state laser can be used in ophthalmologic microsurgery because of its specific wavelength of 1064 nm, which has the property to penetrate the transparent medium of the eye. We design a specific ophthalmic system, containing a Q-switch Nd:YAG laser, an optical stereomicroscope and an aiming system. This laser-stereomicroscope system is used for eye examination and for microsurgical proceedings like posterior capsulotomy and pupilar membranectomy. We had to design an optical scheme of the laser to settle the radiation route. In order to cover the medical domain of the energies, we calibrate eleven attenuation filters using ratiometric method. For a correct position of the place where the laser pulse strikes, we used an original system consisting of two red laser diodes mounted on each side of the binocular One of the advantages of this laser system is taht the output energies can be varied widely (0.8-15 mJ), making a great numbers of applications in clinical ophthalmology possible.

In this research the authors present a comparison of the influence of He-Ne laser 632 nm radiation and laser power density 0.1 mW/cm² [exposure time: 3 minutes] and polarized monochromatic light wave length 620-640 nm upon clinical, histological and electron microscopic changes in the fron epithelium and stroma of the cornea after chemical burning. The research involved 24 rabbits [48 eyes] divided into 3 groups of 8. The histologically and electron microscopic investigations was carried out on the 5th, 10th, 15th and 21st day. In the corneas treated with He-Ne laser there was noticed earlier coping of the inflammatory process in the conjuctiva, and disappearing of the perifocal oedema and faster transparency. The histologically and electron microscopic studies show that He-Ne irradiation after chemical burning of the cornea fastens the regenerative processes compared to those not irradiated and those irradiated with polarized monochromatic light. Furthermore, earlier vascularization of the stroma and filling of the defect with epithelium is noticed in the corneas irradiated with He-Ne laser.

In order to establish the long-term efficacy of selective laser trabeculoplasty for primary open-angle glaucoma [POAG], trabecular meshwork of 34 eyes (21 patients) with POAG was treated with Q-switched frequency doubled Nd-YAG laser with wavelength of 532 nm Coherent Selecta 7000 (SLT). The eyes were divided in two groups: group 1-18 eyes with pigmentation degree in the frontal chamber angle of 1 and 2; group 2-16 eyes with pigmentation degree of 3 and 4. An average of 104 spots on 360 degrees was applied stepwise to the trabecular meshwork of every eye. The treatment and follow up period lasted 6 years. The mean prepoerative intraocular pressure [IOP] in group 1 was 25,5±1,5 mmHg, and in group 2-26±1 mmHg. During the last visit 6 years after SLT, the mean IOP in group 1 was 18,7±1.4 mmHg. Statistically significant decrease of IOP [p<0.001] was observed after SLT by an average of 6,8 mmHg [26.7%]. During the last visit 6 years after SLT in group 2, the mean IOP was 18.8±1.2 mmHg. Statistically significant IOP decrase method for POAG treatment and that IOP decrase in treated eyes is preserved for several years.

The aim of the present work is to compare the photodynamic effect in vitro for permanent cell lines established from some of the most common and invasive human cancers (breast cancer and brain glioblastoma) as well as for animal cell lines obtained from virus-induced transplantable tumors. The cytotoxicity assessment was performed for human breast adenocarcinoma MCF-7, human glioblastoma 8-MG-BA, and two virus-induced animal tumor cell lines: a cell line LSCC-SF-Mc29, obtained from a transplantable chicken hepatoma induced by the myelocytomatosis virus Mc20, and a line LSR-SF- SR, obtained from a transplantable sarcoma in rat induced by Rous sarcoma virus strain Schmidt-Ruppin. We used in the experiments a PS produced by NIOPIK (Russia) [www.tech-db.ru/istc/db/inst.nsf/wu] with peak absorption around 670 nm. The photodynamic effect was assessed by a neutral red uptake cytotoxicity test. To activate the photosensitizer we used a semiconductor laser that emitted at 672 nm at irradiance of 120 mW/cm²; the latter value had been chosen after comparison of the photodynamic effect at 12, 60 and 120 mW/cm².

The investigation of mechanism of ultra-short laser ablation process of biological tissue represents one of the challenging subjects over the last couple of years. The femtosecond laser pulses are very well suited for high precision surgery, due to its low thermal and mechanical stress. The current research was emphasized on the examination of the interaction mechanism of high intensity ultra-short femtosecond and nanosecond laser pulses with hard biological tissue material (tooth, bones). It was established that femtosecond ablation works well for ablation of complex biological molecule systems. A more detailed view was taken by investigating the ablation dynamics at several wavelengths. The precise examination of the mass spectra of laser ablation with 193 nm and 800 nm introduces the way of altering the chemical composition of the ablated tissue. In general, it was found that ablation with ultra-short (femtosecond) pulses at 800 nm radiation yields the highest number of characteristic ions. To better understand the interaction mechanism we have performed post-ionization experiments. It was of main importance to succeed to establish efficient ionization of the organic molecules with minimal fragmentation. This work demonstrates sensitivity of the time-of-flight (TOF) technique and the great potential of the laser ablation/ultra-short laser secondary neutrals mass spectroscopy (LA/US-LSNMA) method in increasing the information content of biomolecular mass spectra.

Progress in optics led to the point when scientists and engineers operate the pulses of the electromagnetic energy containing only a few (in fact, sometime less than one, see examples in [1]) oscillations of the field instead of monochrome or quasimonochrome waves. Even omitting physical problems of interaction between field and matter, including those associated with essential nonlinearity due to extremely high amplitudes of the field, one encounters a lot of problems caused by extraordinary large homogeneous spectral bandwidth of ultrashort pulses. Linear optics of ultrashort pulses essentially differs from that of monochrome waves; hence, the development of appropriate methods for description of such pulses propagation through an optical system is necessary. It is common to our perception to deal with monochrome wave transformation, not wide-spectrum signal one, because in the traditional optics there is the set of solutions for the typical problems. The purpose of this presentation is to show that the equivalent set may be developed also for the optics of ultrashort pulses. As a result, the qualitative study of the diffraction and interference ofultrashort pulses becomes as simple as the ray optics. There are different methods of the analysis of diffraction and interference phenomena. The first possible approach is based on Huygens representation of the diffraction phenomena. Traditional procedure involves Fourier transform of the initial pulse process to get a set of monochrome waves. Then one analyzes the diffraction of each of those waves and finally the resulting monochrome diffraction fields sum back to form a scattered pulse. Rather widely used [2, 3, 4], this method implies reconsideration of developed solutions of classical diffraction problems to take into account some second-order components. Thrown away in the conventional theory as contributing only small phase correction for rather law frequencies, they become significant for high frequency components of the field. Another method suggests decomposition of the initial pulse into a set of wavelets [5]. Being convenient to those researchers who operate with an equal ease with this class of functions and with monochrome waves, this method does not possess the clearness of first one. Moreover, some of them does not meet the causality principle. At the same time, there is another group of methods based on one of principal results of general theory of diffraction [6]. Their formulation is closer to Young interpretation of diffraction and considers the interaction of waves scattered by the edge of aperture and through-passing one [7]. In acoustics and electro-engineering, the method based on the formalism of Green function for the wave equation [8, 9] is used. The fact that this method performs well for linear system analysis in electronics supported us in our attempt. In optics, it was successfully used by J. Connes [10] and L. Mertz [1 1], for example. Both of them studied the propagation of pulses through some most simple devices. Moreover, their analysis was based only on intuitive concepts that led to some mistakes, as it becomes clear today. Nevertheless, the general conclusion on the possibility of using the Dirac transform for the description of the waveform conversion in the process of propagation through the linear optical system became obvious. The technique based on 8-wave ideas proposed in our previous publications [12, 13, 14]. Those papers demonstrated the simplicity of interpretation of spatial and temporal form of the diffracted wave transformation using the pulse approach. The present paper extends this concept and demonstrates complete agreement of its results with classical theory for monochrome waves; the method opens a way to the development of specific software for the analysis of propagation of ultrashort pulses. All methods mentioned above give identical results. To our knowledge, the S -wave approach was not used directly for the solution of diffraction problems in the Kirchhoff approximation. However, it seems to be handy for the description of short pulses propagation. Moreover, it was shown in [12, 14] that the method can clarify some features of diffracted wave that can give a key to a fine experiment realization

This work presents the applications of the method of the disappearing diffraction pattern for refractometric measurements and analysis of scattering media. The behavior of the refractive indices of different aqueous dispersions containing metal and polymer particles is studied theoretically and experimentally. Both metallic and latex solutions exhibit linear dependence of the refractive index on the concentration of particles. Values of the specific refractive index increment dn/dc for Co, Fe and Ag nano-dispersions are calculated. Poly(2-ethylhexyl) acrylate and poly(vinyl acetate) latexes with size of particles between 50 and 1300 nm and concentration up to the maximum possible are systematically studied with respect to the properties of the particles-concentration, diameter and refractive index. Empirical relationships are derived for the investigated latexes, describing the dependence of the refractive index of latexes on their properties and on the light wavelength. Such approach could be used to solve the inverse problem of calculating the concentration or the size of particles, measuring the refractive index. It is shown that the refractometry provides a simple, easy and accurate way to study and analyze properties of dense nano- and micro-dispersions.

Recently, using an aopposite injection we have introduced a novel laser injection-locking approach for high gain (~10⁴-10⁸) and linear amplification of modulated low power (~μW-mW) laser radiation. In this work we report the investigation of the noise characteristics of such amplifier at the example of high repetition rate pulse pumped linear dye lasers. The background emission of the laser at the laser modes outside the signal and counter injection wavelengths is considered as a main source of the noise. By modeling the laser action with adapted system of differential equations and numerical analysis, solving this system for the cavity modes, we have obtained the total noise and its spectral distribution. The results show that for suitably chosen conditions the intracavity noise is very low or acceptable (~10^-2 with respect to the signal output). The essential dependencies of noise characteristics from the system parameters are carried out.

We report a simple technique for generation of tunable subnanosecond pulses (0.1-0.3 ns) based on single spike selection from the relaxation oscillations in a dye laser by use of an active mirror. The selection is in original two-wavelength cavity with competitive generations at two wavelengths, the second of which is forced in appropriate moment by the quickly included amplification of the active mirror to suppress the initially started lasing in the first channel. To produce such switching we form the pump pulse by temporal division of a 15-50 ns standard pump laser pulse using a Pockel's cell with a 1-2 ns switching time and an optical delay line. We have shown that in addition, such formation increases essentially the selected spike power. The proposed technique widens the choice of suitable lasers in which the single spike selection technique may be applied to include dye lasers excited by a Q-switched solid-state laser or a Cu-vapor laser. The other advantages in comparison with the given in the literature single-spike selection techniques is the improved reproducibility of the selection for high (~100-200%) pump pulse power fluctuations, shorter pulse duration and pulse shape improvement. Both theoretical consideration and experimental verification are carried out.

The generation of a temporary stable, TerraW, spectrally broadened laser beam with uniform wavefront is carried out through self-phase modulation in 3-mm Sa plate. The set-up for compression of the obtained spectrally broadened pulse is provided by 2x128 pixels Spatial Light Modulator (SLM) controlled by a genetic algorithm. The obtained ultrashort laser pulses have been characterized by an APE pulse measuring system SPIDER. The measurements show that the pulse length decreases more than 2 times: from 62 fs up to 28 fs. The new pulse shape is close to linear.

A He-Ne laser device has been used for refractometric measuring of a number of optical plastic (OP) specimens. We applied an ellipsometric laser system for the index of refraction initial determination. A table of the experimentally obtained refractive indices of various types of the principal and some new developmental OPs at the laser wavelength λ=632.8 nm is illustrated. The dispersion coefficients of ten American, Japanese and German OP samples were computed using a modified Cauchy's dispersive equation. A table of OP's refractive indices calculated at twenty laser wavelengths in the spectral area from 405 nm (GaN LD) to 1064 nm (YAG devices) is presented.

Results of the experimental tests concerning the wavefront sensor designed for control of the laser beam transformed by the deformable multichannel bimorph mirror are presented in the paper. The sensor developed on the base of the curvature sensing method consists of the vibrating mirror of a membrane type and a multi-element detector for the beam intensity measurements. The characteristics of the sensor are analysed versus the controlled deformation introduced to the tested beam by a deformable mirror. The measurements prove that the curvature signal measured by the detector is proportional to the local distortions of the wavefront of the laser beam.

A new conept for the generation of a gas discharge plasma is under investigation. This new gas discharge is based on a high frequency plasma which is a electrode less configuration. To achieve a high density, the plasma is confined by a magnetic quadrupole field. The energy deposition into the plasma was performed by cw-inductive coupling per antenna. The plasma is protected from the tube wall and is relatively independent of the tube size. A tuneable high frequency amplifier with a maximum power of 300 W is used in a frequency range between 10-45 MHz. During operation a bright plasma with pronounced edges was observed in the center of the magnetic quadrupole. For this configuration an electron temperature between 1.1 to 1.2 eV has been measured.

The plasma in the hollow cathode discharge exhibits well-expressed axial inhomogeneity at dimensions typical for laser oscillation, which may affect the operation of the laser. To optimise the cathode dimensions for a sputtering metal vapour laser, we have measured the axial variation of cathode current and emission intensity of a number of He, Ne, Cu and Ar atom and ion lines, at different discharge conditions optimal for laser oscillation in He(He&Ar)-Cu and in Ne-Cu discharges. The observed axial excitation profiles are compared and the length of the cathode segments at which a nearly uniform discharge can be expected in He(He&Ar)-Cu and in Ne-Cu discharge is determined. Based on the results of the experiments we have demonstrated that the most efficient laser oscillation can be achieved when the laser active volume comprises a series of anodes and cathodes, each cathode with a length of ~1÷2 cm for IR and 2÷5 cm for UV laser oscillation.

A comparative investigation on the output characteristics and the electrical parameters of the UV Cu⁺ Ne-CuBr laser excited by the Blumlein and IC excitation schemes is reported. An optimization of the UV multiline average output power with respect to the discharge conditions is carried out for both excitation schemes. It is obtained that the use of the IC excitation scheme leads to a 30% increase of the average output power at a simultaneous lasing on the five Cu⁺ lines- 248.6, 252.9, 259.7, 260.0 and 270.3 nm, in comparison with the Blumlein scheme. A two-longitudinal-mode oscillation (TEM₀₀ and TEM₁₀ is obtained on the 248.6-nm Cu⁺ laser line with an average output power of 25 mW. When a Ne/He gas mixture (He pressure - 8 Torr and total pressure - 21.7 Torr) is used, a simultaneous laser osciallation on the 248.6-nm and 780.1-nm Cu⁺ laser lines is also obtained with equal average laser powers of about 30 mW.

We present experimental results on Microstructured Optical Fibre (MOF) coupling with standard Single Mode Fibre (SMF) using a simple and reliable set-up. An electric-arc splicing system is used to demonstrate its effectiveness in splicing SMF with MOFs. The measurements of the additional loss induced by transverse and longitudinal offsets at connections between SMF and MOF are reported and discussed. The influence of mode size mismatch is emphasized.

We report on the application of a pulse distributed feedback (DFB) quantum cascade laser (QCL) for open path data transmission. A not cryogenically cooled, pulse QCL in the 1046 cm^-1 range is used. The pulse repetition rate is 100 kHz. In the experiments, the current pulses, driving the laser, are modulated with a low frequency signal. Data transmission over 460 m and 6 km open path were successfully performed. Pulse frequency modulation technique instead of the usual amplitude modulation was chosen because of its high immunity against amplitude noise and signal amplitude changes caused by atmospheric turbulence and aerosols. The demodulated signal is characterized by low distortion, low noise, high dynamic range and wide frequency bandwidth, even for detected laser power variation of more than a thousand times. The haze immunity of the Mid Ir communication channel was studied. Despite the high aerosol optical density, siffucient to suppress completely a probe 20 mW 532 nm beam at a 5 cm distance, no distortion in the IR transmission was observed. In that way the high haze immunity of the mid IR data transmission was demonstrated.

A refractometric structure consisting of a side-polished single-mode optical fiber covered with a thin film of hydrogenated amorphous silicon (a-Si:H) has been studied. a-Si:H films have been deposited by plasma-enhanced chemical vapour decomposition of silane. The sensors elements working with zero and first order optical modes of the amorphous silicon waveguide have been demonstrated. A high sensitivity of 5300 nm per unit refractive index has been obtained for the low values of superstrate refractive indices in the range of 1.33-1.38 by using a-Si:H film with a thickness of about 14 nm, i.e. the interaction with TE₀ mode of the PWG. Despite of the very low thickness of the a-Si:H film there is no need of any additional layer protecting the structure from the analyzed medium. The mechanical and optical stability of the film and its very good adhesion to fused silica eliminate the possibility of the film damaging and makes the structure reliable in use.

The nonlinear dynamics of an erbium-doped fiber laser is explained based on a simple model of the ion pairs present in heavily doped fibers. The single-mode laser dynamics is reductible to four nonlinear differential equations. Depending on the ion pair concentration, the pumping level and the photon lifetime in the laser cavity, numerical calculations predicts cw, self-pulsing and sinusoidal dynamics. The regions of these dynamics in the space of the laser parameters are determined.

The results of test for radiation resistance of high purity crystals (MgF₂, CaF₂, BaF₂Al₂O₃, SiO₂) and quartz glasses (QU-1, KS-4V, Corning 7940) under action of e-beam are submitted. Energy density of e-beam for a pulse duration 80 ns was within the limits of 0,2-2 J/cm². More than 10⁴ pulses has been made on samples within one year. Changes of transmission spectra of samples in a range of 100-1000 nm were traced during an irradiation.

A new high power laser diode driver has been developed and tested. The possibilities for driving high power laser diode bars and stacks at high frequencies has been shown. The driver is with 0.05% noise and ripples at DC, and can be modulated with 15 ns rise/fall times at 100 A, with maximum frequency for square wave modulation up to 1 MHz. The spikes for the optical output at switching on/off are not exceeding 5%. The limitation of the used scheme with the existing commercial components allows frequencies up to 25 MHz and currents to 400 A to be reached. The driver opens new applications for high rate data transmission at long range, fast scanning designators, materials processing, etc. with laser diodes with more than 100 W output power.