In this paper several detection techniques of laser spectroscopy are presented which are illustrated by some examples. They are either based on modified absorption spectroscopy with frequency- or wavelength modulation, on opto-acoustic and opto-thermal spectroscopy, on laser-induced fluorescence or on resonant two-photon ionization. Their advantages and limitations are discussed and possible further improvements are proposed. They are illustrated by several examples, such as overtone spectroscopy of ozone O₃, carbon disulfid CS₂, opto-acoustic spectroscopy of carbonyl sulfid OCS, by Doppler-free opto-thermal spectroscopy of ethylen C₂H₄ and by Doppler-free laser spectroscopy of the small alkali trimers Li₃ and Na₃ detected by resonant two photon ionization.

Laser cooling and trapping techniques made possible during the last two decades important achievements in the atomic physics and quantum mechanics fields. These same techniques can be usefully applied to radioactive atoms by opening new fields of investigations. Nuclear processes can be studied with the atomic physics tools. We focused our attention on Francium radioactive atoms. A magneto-optical trap has been set up at the INFN Legnaro laboratories. Preliminary tests with other stable alkali atoms aimed at an improvement of the MOT collection efficiency are reported. Fast and efficient trap loading of rubidium has been obtained through the light-induced atomic desorption from an organic coating. A larger number of sodium atoms, as compared to monochromatic trapping laser, has been trapped by using a broad-band laser.

Precision laser spectroscopy at λ = 657 nm based on cold neutral Ca atoms released from a magneto-optical trap (MOT) is described. Systematic contributions to the uncertainty resulting from the residual velocity of the atoms and the acceleration in the gravitational field are determined and their influence is reduced by using a combination of different atom interferometers. The results are applied to an optical frequency standard based on Ca atoms. A fractional uncertainty in the measured clock frequency 2 • 10^-14 is observed. The application of a novel method for producing ultra-cold atoms showed in first atom interferometric measurements the potential to further reduce the uncertainty to below 10^-15.

Conventional solid state laser pumping cavities has been used, after proper modification, in order to achieve efficient laser action by Cr:LiSAF crystals. The crystal samples were placed in the laser head, properly supported for efficient pumping to achieve satisfactory laser action. It has been proved that for a successful result a strong flash pumping source and a low output coupling is needed to help the low overall gain of the small Cr:LiSAF samples.

We present a 100 kHz femtosecond amplifier system delivering pulses with a duration of 35 fs and an energy of 7 μJ at 800 nm. The system does not include a stretcher, since the large amount of dispersion accumulated during the amplification process is sufficient to prevent self-focusing. Compensation in all orders is achieved through a combination of a special prism compressor, chirped mirrors, and a liquid-crystal modulator.

Spectral and spatial parameters of the UV Cu⁺ Ne-CuBr laser radiation are calculated and experimentally measured. The estimated width of the laser oscillation band (248.6-nm Cu⁺ line) is about 1.5 GHz (0.3 pm). At a multimode UV laser oscillation a divergence of 0.7 mrad is measured for a curvature radius of the high reflector 3 m. For a laser cavity formed by two flat mirrors the calculated divergence θ_½ is 44 μrad. A comparative investigation on the temporal behavior of the average output power of the UV Cu⁺ laser with inserts made of a quartz and a ceramic tube is reported. The spectral measurements of the discharge are also made. The results show that the quartz tube is metallized and some impurity admixtures are released into the gas mixture. That leads to an average output power reduction from 500 mW to 30 mW at multiline output for an UV laser operation of approximately 25 hours. The using of cermaic tubes results in an absence of the tube metalization, a maintaining of the gas mixture composition, and a relatively constant average output power -- about 300 mW, for an UV lasing of 100 hours.

It is demonstrated experimentally that for copper ion lines laser excitation in a longitudinal hollow cathode discharge (HCD) an optimum current density (approximately 1 A/cm²) exists. Above this value a saturation and even decrease of the laser power is observed. Due to the axial inhomogeneity of the longitudinal discharge the possibility to increase the laser power by increasing the cathode length is also limited. To determine the proper cathode length for a sputtering copper ion laser, the axial current and spectral lines intensity distribution at conditions typical for laser oscillation are measured, showing a maximum at the anode ends of the cathode. Numerical modeling for exactly the same discharge conditions and tube design is also performed. The results are compared with the measured data and reasonable agreement is reached. Based on the results of the experiments and calculations we have demonstrated that the most efficient laser oscillation is achieved whenthe laser active volume comprises a series of anodes and cathodes, each cathode with a length of approximately 1 ÷ 2 cm.

We present new solutions of a diode-pumped, cw Yb:YAG laser that is of interest for applications in spectroscopy and metrology. The proposed schemes permit producing of the emission in a single pumped volume at two independently tunable wavelengths, including single-mode regime. A passively self-injection (PSIL) controlled operation that ensures low threshold and high output is presented. The peculiarities of the two-wavelength operation of the considered laser are carried out. The laser operates in the range 1028 - 1035 nmw with a total output power of 0.4 - 0.7 W.

We propose a simple interferometer-type-device that permits to produce a variable length (1 - 15 ns) rectangular laser pulses, starting from a long (approximately 10 - 50 ns) conventional pulse that is emitted by Q-switched Nd³⁺-doped laser. The system uses an one time switched electro-optical pulse division at the input laser pulse and cutting all-optically a rectangular part of one of the formed partial pulses by appropriate bleaching of interferometer (Fabry-Perot, Fizeau) which gap is an Cr⁴⁺:YAG plate. The precisely controlled bleaching is produced in reliable manner using the second partial pulses and an optical delay line. The length of the obtained rectangular pulse can be precisely varied between 1 and 15 ns. The technique proposed can be applied also for the other lasers.

A new approach for design of resonators of diode-pumped solid state lasers is presented. The required beam waist radii in both the active medium and the passive mode-locking element as well as the operational point on the resonator stability diagram are the initial parameters of our analysis. Analytical formulae are derived for calculation of 3- and 4-mirror resonators.

Recently we have proposed an injection-locking technique for all-optical and high gain (approximately 10³ - 10⁶) amplification of a periodically modulated (PM) intensity low power (approximately μW) laser radiation. The amplification is based on the injection locking control in linear laser schemes with homogeneously broadened active medium. The problem that limits use of such type of optical amplifier is to obtain a linear response to the PM injection. This is solved using a competitive CW injection. We have introduced a few different solutions of such laser amplifier -- with pulse pumping and with CW pumping, using the high repetition rate intracavity laser generation chopping. Here we report the detailed comparative study of such different realization of the proposed by us technique. The theoretical study is based on adapted rate equations system. The main results concerned the optimal case with the lowest nonlinear distortion and the condition of its elimination.

In our work, we develop a numerical model for a fiber ZBLAN host Er³⁺ laser system at 3 μm. The performed simulation concerning the output power thresholds and efficiencies, for different pumping conditions, as well as time dependencies in a stable cw output power region for the output power and population densities, for a suitable range of parameters variation provide a general method to study the EDFA devices.

Different rate equation systems were used to analyze quantum-well (QW) lasers characteristics. Numerical simulations based on solving the nonlinear differential equations which describe the behavior of this kind of devices are done for each of these models using MATHCAD data analysis software which has the advantage of solving complicated systems starting from the familiar mathematical form. Another possibility is using SPICE as a nonlinear equations solver but finding the electrical model of the QW laser is sometimes difficult.

The semiconductor optical amplifiers (SOA) are a base component in the fiber-optic transmission lines. We investigate the interaction with optical pulses of the Traveling Wave (TW) SOA having a typical parameters originated from a semi-classical model of two-level systems. An application of TW SOA as in-line amplifier for an optical pulses sequence and received "pattern" effect is shown.

Stable pulse propagation in optical fiber transmission systems with periodically inserted on the line semiconductor optical amplifiers (SOA) is considered. For describing the properties of SOA, in our work we take account of a semiclassical model, based on interaction of the light with a two-level quantum system. The general parameters of this model are the small-signal gain, the linewidth enhancement factor, the carrier lifetime and the saturation energy. The pulse propagation in fiber is described with Nonlinear Schrodinger Equation which we solve numerically considering the losses in optical fiber and the periodical restoration of the amplitude in SOA.

A power supply for a CO₂ laser used in the tissue ablation capable to control the laser emission in the superpulse operation having a well established waveform was designed. The minimal configuration of the apparatus has four blocks: the DC/DC converter having an improper transfer factor, the electronic commutator for laser pulses control, the network for pulse forming and the controller. The DC/DC converter of the resonant type, having the pulse width modulation (PWM) uses the forced commutator to control the voltage and the current in the transfer process of the power and the stabilization of the laser. It is composed of a resonant half-bridge inverter with serial resonant circuit and an AC/DC class E converter. The commutator of saturable inductor type is based on the B-H characteristics of a ferromagnetic material. The magnetic compression of pulses is realized by a LC elements network, every element being realized by a saturable inductor and one shunt capacitor. A pulse forming network of π type composed of saturable inductor and capacitor is used to match the high voltage supply and the laser tube impedance. For dc operation this circuit represents a LC low pass filter but for pulse operation it is a charge transfer circuit. The controller supervises the inverter and commutator operation, by specific signals from operator (microprocessor), having a structure suited for programmable operation of the CO₂ lasers. Two different error amplifier digitally controlled are used in the feedback loop circuits for the current and the voltage, respectively. By optimization of this modular structure of the power supply, three modes of operation of the power supply (dc, repetitive pulses and super pulses) are ensured in the ablation experiments of the tissues.

Fluorescence emission of the efficient dye laser compound 3,6-dihydroxyphthalimide in dichloroethane solution has been investigated as a function of the concentration of the added strong proton acceptor triethylamine by both steady-state and time-resolved (time-correlated single-photon counting) techniques. Complex decay behavior has been observed. The dominating portion of the emission of the molecules follows the Stern-Volmer quenching. The other part of emission, clearly observed at high concentrations of triethylamine, is assigned to hydrogen-bonded complexes. The fully ionized 3,6-dihydroxyphthalimide is detected as a product of the irreversible excited-state proton-transfer reaction. In solution of neat triethylamine an excited ion pair is formed upon excitation of the hydrogen-bonded 3,6-dihydroxyphthalimide molecules.

Square and hexagonal lattices of optical vortices are generated in a saturable nonlinear medium. If the topological charges of the vortices are of the same sign the lattice exhibit rotation, while if alternative, stable propagation of the structures is observed. In a nonlinear medium vortex lattices induce periodic modulation of the refractive index. Diffraction of a probe beam by this optically-induced phase grating is observed.

The crystal field environment of the Ce⁺³ dopant in LiSrAlF₆ (LiSAF) crystals has been studied by the Electron Spin Resonance (ESR) spectroscopic technique. Ce was found in a highly anisotropic trigonal environment which suggests that it substitutes for the Sr site. Na⁺ ions operate as charge compensators to Ce⁺³ possessing nearby to Ce, Sr sites. The ground state electronic wavefunction and the energy diagram of Ce are discussed in view of our ESR results.

The problem for phase matching (PM) of several nonlinear processes is one of the main in nonlinear optics and in optical switching technology. We propose a novel scheme for dual channel third harmonic (TH) generation using a single two dimensional nonlinear photonic crystal (2DNPC). The proposed interaction at low input intensities is four times more efficient than the conventional schemes.

Generation of fifth harmonic by cascading of two phase-matched or two near phase-matched third order processes in single cubic nonlinear medium with focused fundamental beam is investigated theoretically. With the help of analytical and numerical investigations the optimized conditions for maximum conversion into fifth harmonic are found. In general the optimal position of focusing depends on the values of the mismatches Δk₁ and Δk₂ for both "steps" of the third order cascading (ω+ω+ω=3ω; 3ω+ω+ω=5ω). It is shown that for best efficiency this method of fifth harmonic generation requires specially chosen Δk_1,opt and Δk_2,opt and focusing in the center of the nonlinear media. If the phase matching parameters are fixed and they deviate from the optimal values, then the optimal strength of focusing and position of the focus spot should be calculated according the analysis presented here.

In the present communication we report on the study of the locking position of the frequency of a diode laser on different external parameters like the temperature of the reference cell, external magnetic field and the intensity of the pump and probe beams preparing saturation absorption. This study is important in view of applications of frequency stabilized diode lasers for atomic clocks istead of discharge lamps.

Temperature dependences of coherent resonances in Na and Cs atoms prepared by two coherent laser frequencies or two polarizations of single frequency laser field are presented. It is shown that the temperature dependence of the amplitude or contrast of the resonances in most cases exhibits a maximum. For both types of coherent resonances, a reason for the contrast reduction at higher temperature is the increased absorption of the laser light along the gas cell due to the optical thickness of the medium. Spin-exchange collisions lead to resonance contrast reduction more effectively in a cell with pure alkali atoms.

Coherent population trapping (CPT) resonances in the degenerate two-level system of the F_g = 2 → F_e = 1) transition of the ⁸⁷Rb D₁ line were investigated in an uncoated vacuum cell by means of Hanle effect configuration. CPT signals with complex shape (narrow resonance approximately 2 mG superimposed on the wide one approximately 150 mG) were observed. The influence of weak transverse magnetic fields (0-1.2 G) on the amplitude and width of the two components was measured. The observed narrow resonances are interesting for application in high resolution spectroscopy and magnetometry.

A theoretical model describing magnetic resonance in a strong laser field was proposed. The exact solution of the well known system of equations was solved for the transition between a ground state with Jφ = 1 and an exited state with J_f = 0. It was shown that in the spontaneous emission intensity from the level with J_f = 0 resonant changes will be observed when the frequency ω of the altering magnetic field becomes equal to the Larmor-frequency determined by the constant magnetic field H_o.

The lower level of laser transition on 632.8 nm (2p₄) has been investigated using Hanle absorption resonance method. Advantages of the approach are discussed. Radiation width and collision (pressure and discharge current broadening are determined.

The opto-galvanic signals from oriented and aligned ensemble of atoms are detected and compared. A Ne/Ca hollow cathode discharge (HCD) lamp is used as a plasma medium illuminated with He-NE laser. The measurements are performed at low gas pressure 4 Torr in range 0,3 ÷ 8 mA discharge current. The established differences in signals are ascribed to proper coherent conductivity corresponding to oriented and aligned ensembles. Another kind of comparison is made depending on working I-V point.

The optogalvanic signals (OGS) at 667.728 nm (the 1s₄-2p₁) Ar transition in pure Ar and He:Ar=1:1 mixture have been investigated with a low power diode laser in a longitudinal hollow cathode discharge. Qualitative explanation of the formation of the 667.7 nm Ar OGS is proposed. A simple model for explanation of the dependence of the 667.728 nm Ar OGS amplitude and sign along the cross-section of the discharge tube is applied. The OGS in pure Ar and HE:Ar = 1:1 mixture gas discharge are compared.

A more detailed investigation of optogalvanic signals, induced by resonant laser excitation of Se, Ne and Ar ions in a hollow cathode discharge, is carried out in the present work. An immediate goal was to analyze and verify some hypothesis about the mechanisms, responsible for the formation of such signals, taking into account their dependence on the current characteristics, the kind and pressure of the buffer gas, as well as their radial distribution.

Radiative lifetimes of n¹P₁ excited states (n = 9, 10) of netural mercury have been determined. Two techniques have been used -- time-resolved laser-induced fluorescence spectroscopy in a laser-produced mercury plasma and multichannel delayed coincidence method wth pulse electron excitation. Measured lifetimes are compared with previous results. The influence of the radiation trapping on the effective lifetimes has been investigated. The electron configuration interaction beween the 5d¹⁰6s np ¹P₁ and 5d⁹6_s²np ¹P₁ (Beutler) series has been studied.

The quenching cross sections of ⁴He(2¹S, 2¹P) and ³He(2¹S, 2¹P) states by collisions with Ne (¹S₀) atoms are investigated by a time resolved method. The influence of different processes involved in population or depopulation of these states was evaluated. The quenching cross section for ³He(2¹P) and ³He(2¹S) states by Ne(¹S₀) atoms are σ_2'p = (2.91 ± 0.61)x10^-15cm² and σ_2's = (1.03 ± 0.04)x10^-15 cm² respectively and for ⁴He(2¹P) and ⁴He(2¹S) states - σ_2'p = (1.84 ± 0.45)x10^-15 cm² and σ_2's = (8.62 ± 0.3)x10^-16 cm² respectively.

Previous studies of OH stretching band of aqueous solutions of short poly(oxyethylene)s POEs showed a 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. In this paper we checked how the hydration structure of water molecules around four types of short POE - C₁E_iC₁ (i=1,2,3,4) aqueous solutions depends on the length and the type of the dissolved POE.

Applying continuous model, about network of hydrogen bonds, and free energy of water founded by the model, we calculate the concentration of strong hydrogen bonds in liquid normal H₂O and heavy D₂O water in dependence on temperature in a range of 240 K to 400 K.

The comparison between two-wavelength and two-spacing projection phase-stepping interferometry for real object contouring is presented. Single exposure reflection hologram with two-frequency generating temperature stabilized diode laser is realized. Theoretical approach, experimental results as well as the assessment of sensitivity and uncertainty of the measurements are discussed.

For all kinds of laser applications it's important to know the refractive indices of materials for the corresponding wavelength. However, most commercial refractometers are equipped with sodium lamp and measure refractive index for a wavelength λ = 589.3 nm. Lack of refractometric data and laser refractometers becomes more grave problem outside the visible region, especially in IR, interesting because of the fast development of fiber and biomedical optics and telecommunications. In this work visible-IR refractometric measurements are performed with a simple diode laser microrefractometer. The device is based on the method of the disappearing diffraction pattern. The refractometer consists of a simple rotary table (1 arcmin resolution), total internal reflection prism, diffraction grating and set of diode lasers, emitting in the red (633 nm) and near IR (796 and 840 nm) region. Results are presented for a set of liquids and are compared with the corresponding values from the literature. The experimental error is estimated of 5.10^-4.

For all kinds of laser applications is important to know the refractive indices of materials for the corresponding wavelength. Accurately measured RI value can be used for structural analysis, in many branches of the science and industry. However, commercial refractometers usually measure refractive index at the wavelength of one lamp's discrete line. That's why investigators sometimes have to design new or to modify standard refractometers to perform adequate experiment on the desired wavelength. This work reports the design of a simple automatic laser refractometer. The method of the disappearing diffraction pattern is used for the measurements. The device uses diode laser placed in a socket, which allows easy replacement of lasers and performing measurements at different wavelengths. The apparatus can measure RI of liquids with accuracy better than 1.10^-3 in a range from 1.33 to 1.40.

Three new side-chain cyan-azopolymers have been synthesized for the purposes of optical storage and processing of information. A very large birefringence (> 0.05) is induced in them on illumination with linearly polarized Ar laser beam (λ = 488 nm). It has been shown that the vaue of the photoinduced birefringence depends on the length of the side chains of the polymers. The effect has long memory time -- more than six months. We have used the self-induced rotation of the polarization ellipse in photobirefringent materials to induce chiral structures in the polymers. Total twist angles of the photoinduced spirals more than 90° have been achieved. The new polymers are suitable for the fabrication of light-controlled polarization switches.

An improved sensitivity in speckle-shear interferometry for out-of-plane displacements measurement using 2D folding shear is obtained. A triple prism as a shearing device is utilized. The sensitivity of measurement is up to two times higher in comparison with the one-dimensional folding shear at the same loading of the object. The same approach was feasible to be applied for deformation investigation of microstructures with magnification. The proposed method is especially suitable for symmetrical field deformation measurement, residual stress detection, continuous monitoring of object subjected to risk and other tasks of non-destructive testing.

An electronic speckle pattern interferometry (ESPI) system for detection of cracks and defects is presented. In the first stage a holographic optical element (HOE) is recorded using a photopolymer material. Since the polymerization process occurs during recording, the holograms are produced without any development/processing. In the second stage the HOE is used in an ESPI configuration for detection of cracks and defects. Due to the introduction of the HOE in the ESPI set-up, precise alignment of the optical elements is not necessary. For this reason the system is well suited for industrial applications.

The use of electronic speckle pattern interferometry (ESPI) for non-destructive characterization of unplasticized polyvinylchloride (uPVC) pipes is presented. When pipes are inflated slightly by internal pressurization ESPI may then be used to measure the resulting displacement over the area imaged by the video camera. The interferometric method used is non-contact and gives high-confidence results for strain and Young's modulus of thick PVC pipes. As a step towards using ESPI in dynamic rather than static applications, the ESPI data were recorded during the application of pressure increase. At the same time the change in pressure in the pipe was monitored using a pressure transducer and a specially written Labview Program so that the deformation caused could be modelled using Finite Element Analysis. A finite element model was developed for prediction of the mechanical behavior of the pipes undergoing transient pressure change. The model data have been used here for comparison with ESPI results for slow dynamic deformation of the pipe under test. Demonstration of the possibility of carrying out similar analyses in a dynamic system will greatly expand the applications for this technique.

Visible photoluminescence (PL) in anodized porous Si (PS) at room temperature has opened the way to realize different types of quantum electronics devices based on silicon technology. Such devices require a strong PL intensity and a controlled shift of the PL peak on the energy scale. Porous silicon is produced by electrochemical etching of either p- or n-type crystalline silicon. Illumination is one of the most complicated parameters in PS formation, because it changes the properties of microporous as well as macroporous layers. It is necessary to illuminate the wafer during the anodization in order to create the holes required by the chemical reaction to form the PS. In this paper we present the results of the effects of illumination level during fabrication on the PL properties of p-type PS and it time degradation dynamics.

Mie scattering lidar methods for measuring aerosols and clouds are described. The concepts of Mie scattering lidars, depolarization measurements, and bistatic lidar methods will be described. High-spectral-resolution lidar (HSRL) method for measuring optical characteristics of aerosols and clouds will be also described. Lidar systems and recent applications of Mie scattering lidars will be then introduced. These include development of a compact automated two-wavelength polarization lidar, network observations of Asian dust (Yellow Sand) using automated compact Mie lidars, measurements of the lidar ratio of Asian dust and ice clouds with a HSRL, and observations of water cloud particle size with a bistatic lidar.

An overview of optical techniques for environmental monitoring is presented. Range-resolved measurements of atmospheric pollutants can be performed using the differential absorption lidar technique. Fluorescence lidar allows assessment of vegetation status and also the conditions of the facades of historical buildings. Diode lasers provide particularly realistic schemes for atmospheric gas analysis, where certain wavelength ranges, which are not easily directly assessed, can be reached by sum- and difference frequency generation. Finally, the gas correlation principle can be used for real-time imaging of hydrocarbons. Several types of such optical environmental monitoring are illustrated with examples from research at the Lund Institute of Technology, Sweden.

The propagation of ultrashort, ultra-intense laser pulses gives rise to strongly nonlinear processes. In particular, filamentation is observed, yielding an ionized, conducting plasma channel where white-light supercontinuum due to self-phase modulation occurs. This supercontinuum, extending from the UV to the IR, is a suitable "white laser" source for atmospheric remote sensing, and especially Lidar (Light Detection and Ranging). Recent significant results in this regard are presented, as well as lightning control using ultrashort laser pulses. The application of ultrashort-pulse lidar to aerosol monitoring is also discussed.

We review the basic theory of coherent Doppler Lidar for wind measurements and compare the new 1.55 μm technology with the traditional 10.6 μm (CO₂ laser) system. There is now a huge selection of reasonably priced laser sources and optical components operating at 1.55 μm. The combination of a distributed feed-back diode laser oscillator and an erbium-doped fiber amplifier can provide 1 W or more of optical power over a linewidth much less than the Doppler shift of the return signal. Although the quantum efficiency is smaller at 1.55 μm than for a CO₂ system, atmospheric scattering is stronger. Overall, the SNR should be significantly less than at 10.6 μm, but clear-air wind measurements should still be possible in most atmospheric conditions at eyesafe power densities. We will illustrate this technology using a system being developed and tested at UMIST. This is a bistatic, unfocussed system which uses fiber-optic delay lines to define a range of target distances. Preliminary measurements have been encouraging. The components used in our system were mostly available off the shelf to a total value of $k60-65. Of this, nearly $k40 represented the cost of the optical amplifier. The wider application of this technology will await these devices falling in price.

A novel method for high-resolution measurements of photon arrivals and and time profiling has been developed. It is acting as a TOF method, but is effective at higher (up to 100 times) count rates. The minimal tolerable interval between the adjacent pulses is determined by pulse count duration and the discriminator dead time. The method is based on ADC sampling of counts and their software processing. It provides a time accuracy comparable with the accuracy of well-known TOF-techniques as well as restoring (zooming) lidar profiles of varible resolutions after the receiving. The final resolution can be quite better than the sampling step of raw data (δT ≥ 1 ns has been demonstrated).

In the paper methods and experimental techniques for study of various types of clouds in the PBL (St, Sc, Cu, Stfr, fair weather clouds, etc.) accompanied by the obtained related information are presented and discussed. The abilities of different methods for determination of the cloud base height and its dynamics are also considered. The possibility for determination of the clouds phase composition through analysis of the lidar signal polarization characteristics is shown. The basic physical mechanisms grounding the lidar study of cloud formations and the limits of their applicability are discussed. The algorithms of data processing and desired information extraction are described as well. The studies presented in the paper were carried out using a backscatter aerosol lidar system with a polarization unit and module for the viewing angle variation. The results obtained employing the methods and techniques, subject of the paper, could be summarized as follows: (1) following of the base height of various types of clouds and its dynamics in different atmospheric situations and synoptic conditions, including atmospheric fronts passage; (2) determination of crystal (ice) phase within the volume of different types of clouds; (3) estimation of the density of cloud formations; (4) determination of some microphysical characteristics of the clouds, such as droplets mean size, water content, etc.

The observation of the processes taking place in the entire planetary boundary layer of the atmosphere in the case of stable stratification and during the development of a convective boundary layer correspond thoroughly to the capabilities of a scanning aerosol lidar (SAL) and polarization aerosol lidar (PAL). Recently methods are used allowing automated determination of the maxing layer height, e.g., through the first derivative of the signal, the maximum of its standard deviation, in certain cases through the depolarization ratio (δ) of the signal, etc.

The Solar X-ray Imager (SXI) is a complimentary, add-on instrument designed for use on the next generation of Geostationary Orbiting Environmental Satellites (GOES). Its primary mission is to continuously observe the full solar disc at X-ray wavelengths; including coronal holes, active regions, flares, and coronal mass ejections. For wide-field imaging applications, there is little merit in an optical design exhibiting stigmatic imaging on-axis; we therefore departed from the classical Wolter Type I design in favor of a hyperboloid-hyperboloid design that balances not only defocus with field curvature but also third-order spherical aberration and astigmatism with oblique spherical aberration. A detailed system engineering analysis including the substantial surface scattering and detector effects indicates that the resulting hyperboloid-hyperboloid design will achieve an 80% increase (over the baseline design) in the number of spatial resolution elements (and hence in total information content in the image) over an 18 arc min radius field-of-view. A comparison of performance predictions with X-ray test data for the SXI Engineering Model is included.

The statistical properties of cloud base height (CBH) time series have been studied in our previous works. Our interest here is focused on the investigation of their changes in time, reflecting changes in the evolution of the physical processes. Therefore in this study we use methods, describing qualitative time variations of the signal in terms of associated quantifiers. Their application gives us the type and the ranges of the signal correlations, reveals periodicity, assesses the predictability (on the basis of chosen long-term averaging time period T₂) and detects deterministic regimes in the studied CBH time evolution. The data used in this study are recorded during the Southern Great Plains (SGP) (Oklahoma, USA) site of the Atmospheric Radiation Measurement Program of the Department of Energy.

Ozone is one of the main air pollutants. Now it is suggested that a positive trend of tropospheric ozone concentrations takes place. The question concerning the quality of ozone data, from which O₃ trend is evaluated, is very important because on base of this trend are accepted the political and economical decisions directed at ozone pollution reduction. Two methods (ultra-violet optical absorption and chemiluminescence) for surface ozone measurements have been analyzed with respect to the quality of O₃ data. The review shows that the ultra-violet (UV) optical absorption method may be influenced by positive interferences from other atmospheric components. It appears that the chemiluminescence method is more interference free.

High-power pulsed laser diodes are employed for determining atmospheric humidity and methane. The proposed DIAL method optimizes the spectral properties of laser radiation within the molecular absorption bands of 0.86 - 0.9 μm of these major greenhouse gases. The explicit absorption spectrum is explored by computational convolution method based on reference data on spectral linestrengths modulated by the characteristic broad laser line of the selected laser diodes. The lidar scheme is ultimately compact, of low-energy consumption and suggests a large potential for ecological monitoring.

The paper refers to novel aspects of application of the laser radar (LIDAR) to differential absorption spectroscopy and atmospheric gas monitoring, accenting on the advantages of the class of powerful pulsed laser diodes. The implementation of the task for determination of atmospheric humidity, which is a major green house gas, and the set demands of measurement match well the potential of the acquisition system. The projected system is designed by transmission of the operations to Digital Signal Processing (DSP) module allowing preservation of the informative part of the signal by real-time pre-processing and following post-processing by personal computer.

The influence is investigated quantitatively of the velocity fluctuations in turbulent atmosphere on the formation of the autocovariance of coherent heterodyne aerosol lidar signals. A multishot, high pulse repetition rate lidar operation is supposed. The limit cases of long-term and short-term averaging are especially considered, when the observation (data accumulation) time is respectively much larger or much less than the correlation time of the fluctuation process. As a result, the intuitive conception is proved and illustrated quatitatively that a long-term averaging, under stationary conditions, allows one to obtain (on the basis of the autocovariance) a range-resolved estimate of the parent population mean Doppler-velocity profile; a short-term averaging allows one to determine a (near) instantaneous range-resolved Doppler-velocity profile.

A novel high-precision pulsed ranging method is developed. It involves preliminary transformation of photon detector signals (convolution), analog-to-digital sampling, software processing by deconvolution, digital filtering, pulse shape retrieving and pulse center determination. The method is effective for arbitrary pulse durations (shorter or larger than the sampling step) and is low sensitive to the shapes of the reflected pulses. Using 20 MHz/8bits ADC, an experimental timing accuracy is achieved of approximately 600 ps (approximately 10^-2 times the ADC-sampling step) for single measurements and of approximately 30 - 50 ps (approximately 10^-3 - 10^-4 times the sampling step) in averaging regime.

The main purpose of the study is to estimate the root-mean-square signal-to-noise ratio (rmsSNR) characterizing the coherent heterodyne detection of aerosol-backscattered lidar returns influenced by the turbulent fluctuations of the refrative index in the atmosphere. A general expression is obtained heuristically that describes the rmsSNR as depending on (generally turbulence-affected) the return-intensity relative variance and the ratio of the coherence area of the lidar return to the receiving-aperture area. On the basis of the expression obtained, the rmsSNR is estimated as a function of the distance (of the scattering volume) along the line of sight at different values of the wavelength of the sensing radiation, the receiving-aperture radius, the transmitted beam-pulse radius, and the refractive-index turbulent parameter C_n². It is shown that the rmsSNR values obtained at different distances under different experimental conditions are mostly near the unity, and the coherent heterodyne lidar signal should have correspondingly circular complex Gaussian statistics.

We have developed an automatic pulsewidth tunable femtosecond Ti:sapphire laser system that can generate an output of 50fs - 1ps and sub-mJ/pulse at a repetition rate of 1 kpps. The automatic pulse compressor enables one to control the pulsewidth in the range of 50fs - 1ps by use of a personal computer (PC). We describe our recent results of tailored ablation processing of advanced functional materials such as GaN, BN, and hydroxyapatite. By use of the femtosecond laser pulse tailored for a specific material, we have demonstrate precise material procesing without chemical composition change and heat affected zone. The fabrication of optical waveguide in fused silica is also described.

Pulsed laser deposition of thin films has besides numerous advantages a major shortcoming which is the presence of particulates of various shapes and dimensions both on surface and inside obtained structures. Indeed, in many key technological applications the use of completely particulates free films is mandatory. We demonstrated that the origin of size and density of particulates depend on specific experimental conditions. Nevertheless, the proper choice of deposition conditions (i.e. ablating laser wavelength and fluence, target-collector separation distance, growing temperature, ambient gas nature and pressure) allows for the decrease under a certain extent of pollution with particulates, but not for their complete elimination. This lecture reports our successful attempts to obtain completely particulates free deposited structures using two synchronized pulsed laser sources. The first, UV laser source was used to ablate the target material. The second, IR laser system was directed parallel to the target surface. The role of the second laser was to heat and vaporize the particulates present in the tail of the plasma ablated by the pulsed UV laser source.

Overview of some recent works on waveguide lasers and laser deposited waveguiding films is given. Published results and parameters are summarized. Activities of laser deposition laboratory of the IP, Prague, in fabrication of waveguiding films, are presented.

Laser ablation of iron by femtosecond and picosecond pulses is investigated using molecular dynamics (MD). The electron heat conduction is taken into account in the simulations. Several stages of the ejection of the particles is determined. The compression and the subsequent relaxation of the pressure into the bulk lead to removal of large amount of the material. These processes are also accompanied with the formation of voids in the material. Two different regimes of the ablation are observed depending on the laser fluence. The estimated threshold of ablation is in good agreement with the experimental data found in the literature. The dynamics of the shock wave and the temperature distribution in the material are also obtained.

We report the successful deposition of films containing CrO₂ by pulsed laser deposition from various chromium oxide targets. The incorporation of CrO₂ inside structures was possible only under precise deposition conditions in respect with target nature, collector nature, temperature and ambient gas pressure.

Yttrium iron garnet (YIG) thin films were grown on (0001) sapphire substrates using pulsed laser deposition (PLD) technique with a XeCl excimer laser. The as-deposited films were amorphous and diamagnetic. Two kind of annealing procedures were carried out to modify the properties of garnet films. The structural, morphological, and magnetic behavior of YIG films treated by laser-magnetic field or annealed at temperature close to the melting point for 24 h were studied and compared. Polycrystalline films with flat surface, small grain size, and low droplet contamination were produced. The films exhibit soft magnetic properties, where easy axis of magnetization lies in the film plane. The high values of perpendicular magnetic anisotropy were registered.

High chromium martensitic stainless steel has been surfacely treated by pulsed Nd:Glass laser. The temperature fields at the surface and in the bulk during the laser pulse and following cooling stage have been estimated with a numerical simulation. The modification of structure parameters has been analyzed by X-ray diffraction both in standard Bragg-Brentano and grazing incidence beam geometries. It has been found that the laser treatment modifies the surface parameters as follows: introduces residual macro-stresses, vacancies and dislocations, increases significantly (with 90%) Vickers micro-hardness at the surface and causes formation of a very thin oxide film.

This contribution examines the basic concepts and results of two laser ablation models based on commercially available hydrodynamical codes. In both cases the different material phases are described continuously by a single numerical algorithm. The first approach uses a finite-element model for the simultaneous description of solid and melt. It is thereby particularly suited for the description of melt formation and ejection. The results indicate a slow acceleration of the melt during the laser pulse up to velocities of some 10m/s followed by a rather steady-going ejection which is finally cut off by the resolidification. Although it was possible to examine this expulsion process, the model showed considerable numerical stability problems for higher intensities and the ultrasonic vapor expansion cannot be included. To overcome these shortages another model is proposed which is based on an equation of state for the target material in combination with a special pressure-based solver. Besides the continuous description of the material states, it also includes a continuous treatment of the beam propagation and energy coupling by solving Maxwell's equations. Although the work on this model is still going on, some of its basic prospects and limitations can already be discussed.

In the present paper the possibility of the Copper Bromide (CuBr) laser as an attractive tool in the micromachining of different materials has been demonstrated. High-quality percussion drilling, trepanning, scribing, and precision cutting were demonstrated on metals and ceramics with a negligible heat affected zone (HAZ). These good results were achieved with the combination of high power, short pulses, visible radiation and close to the diffraction-limited beam quality.

The direct laser cladding process is applied for production of the cobalt-based stellite SF6 coatings on the chromium steel substrates of a composition designed for the steam turbine blades. A cw 1.2 kW CO₂ laser stand equipped with a multi-stream nozzle mounted co-axially with the focusing optics is applied. Experiments are performed for the non-preheated as well as preheated base material. Differences in microstructure, chemical composition, and in the cracking susceptibility between coatings produced on preheated (780 - 1000 K) and non-preheated substrates are analyzed by means of scanning electron microscopy (SEM) and the Energy Dispersive X-ray Spectroscopy (XEDS). Results indicate a significant improvement of the clad quality and decrease of the micro-cracking susceptibility with the increase of preheating temperature. The presence of Fe in the coatings is ascribed to migration from substrate due to preheating.

The effect of a Q-switched Nd:YAG laser irradiation applied for ablative cleaning of the surface contaminants on cellulose samples and aimed on conservation of historical paper documents is investigated. The removal effectiveness of an artificial graphite contamination from model samples is investigated in dependence on the laser wavelength (532, 355 and 266 nm) and fluence (0.3 to 0.9J/cm²) and also the surface color changes are measured. Damages of cellulose fibers due to laser interaction are examined by means of the SEM technique. For irradiation at 266 nm only partial removal of the contamination and a distinct cellulose degradation, and also the yellowing of paper surface are observed. For the 355 nm wavelength and energy fluence below 0.6 J/cm² the degradation of cellulose fibers does not occur. However, a slight yellowness of the surface is observed. The optimal cleaning wavelength of 532 nm and safe energy fluence below 0.6 J/cm² found experimentally agree with literature.

Laser-induced fluorescence is a technique for optical tissue characterization. It has a real-time capability and as the excitation light and the fluorescence emission are transmitted through optical fibers the technique is compatible to various kinds of endoscopes for hollow organ investigation. The tissue fluorescence itself with the emission from the endogenous chromophores or enhanced with exogenously administered tumor seeking agents are employed. Contrast functions are being developed for optimal tumor demarcation. Photodynamic therapy is a selective therapy for certain types of malignancies. In particular the topical application of a sensitizing agent has been employed for human skin malignancies. Clinical examples are both from the detection and the treatment side.

Hard dental tissue laser applications, such as preventive treatment, laser diagnosis of caries, laser etching of enamel, laser decay removal and cavity preparation, and more recently use of the laser light to enlarge the root canal during the endodontic therapy, have been investigated for in vitro and in vivo applications. Post-ablative surface characteristics, e.g. degree of charring, cracks and other surface deformation, can be evaluated using scanning electron microscopy. The experimental data are discussed in relevance with the laser beam characteristics, e.g. pulse duration, beam profile, and the beam delivery systems employed. Techniques based on the laser illumination of the dental tissues and the subsequent evaluation of the scattered fluorescent light will be a valuable tool in early diagnosis of tooth diseases, as carious dentin or enamel. The laser induced autofluorescence signal of healthy dentin is much stronger than that of the carious dentin. However, a better understanding of the transmission patterns of laser light in teeth, for both diagnosis and therapy is needed, before the laser procedures can be used in a clinical environment.

In this study, the Nd:YAG laser (1.06 μm and 1.32 μm) beam-skin tissue interaction is simulated by the MC method. Two-layer skin model-epidermis and dermis is used. The goal of the study is to explain the causes for obtaining of qualitatively different macro-effects in clinical applications of near situated IR wavelengths. The possibility to use the Nd:YAG laser in the cosmetics for skin rejuvenation by the thermal influence to collagen without any damaging effects to the surrounding tissues is shown.

Most of the latest achievements concerning laser energy transfer through tissues is based on transport theory instead of Maxwell equations, due to the biological tissue inhomogeneities. The diffusion model we have described takes into account several tissue layers, with different optical properties, different refractive indices at their boundaries and anisotropic scattering. The algorithm has been implemented as a function which uses as parameters the simulation data (number of photons, maximal depth, analysis radius, depth and radius resolution) and also the optical characteristics of tissue layers. Our results refer to the simulation of light propagation through a single tissue layer. We have studied the optical properties of two tissue samples, of half-infinite surface, 1 cm in depth, which were irradiated with a very thin and uniform laser beam. We computed the average values of six simulations of 1000000 photons package each, for a vertical and horizontal resolution of 100 points. For a distance from the laser beam greater than 0.1 cm, the reflectances are approximately the same, while the transmittances are significantly identical at high depths inside the tissue. Our results are in good agreement with the experimental measurements, thus showing the utility of the method for several tissue layers studies.

The aim of this study was to apply a laser refractometer based on a total internal reflection for measurement of refractive indices of thin tissue samples. The tissue slices with thickness from 5 to 15 μm and cross-sectional area of about 1 - 1.5 cm were cut with a freezing microtome and mounted on microscope glass slides. The samples from a liver, kidney, myocardium and skin were taken post mortem from 3 male patients (50, 52 and 75 years old) with some pathological tissue changes as well as from 3 dead fetuses 24-48 hours after the death. To indicate the morphological changes, the samples were stained with hemolown-eosin (HE) and studied microscopically. Using a two-beam UV-Vis-NIR-spectrophotometer Cary-5E (Variant), on-axis transmittance of the samples was measured over the 350 - 2000 nm range and the spectra of the extinction coefficient, in cm^-1, were calculated. The measured refractive indices correspond to dehydrated tissue samples.

Although the low-level laser therapy (LLLT) has been accepted in the clinical practice, its efficiency is still questionable because of the unclear mechanisms of LLLT action. This work presents the results of LLLT applied to volunteers who need recovery from trauma or suffer from rheumatic diseases, inflammatory disorders, etc. The control group we used for comparison consisted of patients being treated by conventional therapy that included massage and acupuncture needles. The effectiveness of the LLLT was graded under four categories. Short-term and long-term side effects as well as conditions responding only to LLLT were recorded. The successful treatments were up to 70%, which coincided with the result of the control group. The LLLT was performed with a GaAs laser system provided with additional set of six light CW emitting diodes to scan a larger area of a tissue surface. To evaluate the light delivery inside the tissue, the spatial energy distribution within the laser beam was measured with a CCD camera. On its basis, the light dose absorbed in the tissue was calculated both in the boundary layer under the surface and in depth using a reduced variance Monte-Carlo code.

Photodynamic therapy (PDT) is a treatment modality that uses a drug and light to kill tumor cells. A large number of photosensitizing agents have been tested in PDT exeperiments. The aim of the present study was to evaluate an effect of 5, 10, 15, 20-tetra (4-sulfophenyl) porphyrin (TS₄PP) on viability of tumor (LSR-SF-SR, LSCC-SF-Mc29) and non-tumor (EBTr, L929) cell lines in vitro. The experiments were performed using neutral red uptake cytotoxicity test. Different concentrations -- 10, 100, 250 and 500 μg/ml, were tested. Light at 514 nm was applied using Ar-ion laser. The light doses delivered varied from 0.2 up to 2 J/cm². The effect of the compound without irradiation was also examined.

The goal of our study was to investigate the natural intrinsic fluorescence in carious human teeth and different stages of demineralization and any correspondence of such autofluorescence to the aminerl and organic distribution within the lesions. Fluorescence spectra of teeth, illuminated with 337 nm nitrogen laser were recorded. There was observed a significant decrease of the intensity of the autofluorescence signal in the case of caries. The fluorescence of the initial carious lesions had a lower intensity and a "red" shift compared to the intact teeth. Spectra, obtained from the enamel consisted of one intensive peak on the 480 - 500 nm and one secondary peak on 430 - 450 nm. In the dentine this secondary component had intensity, compared to the value of the 490 nm peak intensity. In process of the demineralization of the teeth we observed "blue" shift of the fluorescence spectra, obtained from the lesion's area -- spectral forms of the tooth strive for those of dentine. Undoubtedly, these results are one useful tool for differentiation between demineralization and initial caries.

The goal of our study was to investigate the natural intrinsic fluorescence in human enamel and dentine and any correspondence of such autofluorescence to the results from electron scanning microscope studies about mineral and organic distribution in different tooth structures. Fluorescence spectra of sound enamel and dentin, illuminated with 337 nm nitrogen laser were recorded. The spectrum of sound tooth enamel consists of a broad band -- 490 nm maximum of fluorescence with one secondary maximum at 400 - 440 nm. The spectrum of the sound dentine has a maximum at 490 nm, like enamel spectrum but the peak at the 400 - 440 nm has intensity, comparable with the peak intensity at 490 nm. Distributions of elements -- Ca and P in area and line were obtained by the method of X-ray microanalysis. The images of the investigated surfaces as well as distribution of basic elements in the area were obtained.

In this work the results of adaptation of impartial methods for color determination aimed at developing of techniques for estimation of human teeth whiteness degree, sufficiently handy for common use in clinical practice are presented. For approbation and by the way of illustration of the techniques, standards of teeth colors were used as well as model and naturally discolored human teeth treated by two bleaching chemical compositions activated by three light sources each: Ar⁺ and CuBr lasers, and a standard halogen photopolymerization lamp. Typical reflection and fluorescence spectra of some samples are presented; the samples colors were estimated by a standard computer processing in RGB and B coordinates. The results of the applied spectral and colorimetric techniques are in a good agreement with those of the standard computer processing of the corresponding digital photographs and complies with the visually estimated degree of the teeth whiteness judged according to the standard reference scale commonly used in the aesthetic dentistry.

This paper presents the effect of thermal neutrons irradiation on some properties of one of the most common long-chain fatty acids, found in combined form in natural animal and vegetable fats, the stearic acid, with role in the biological membrane. Microscopic aspect, electric current and optical properties under laser beam change by irradiation. These changes can offer information both for biology and technique.