Power and spectral characteristics of Fabry-Perot semiconductor lasers based on at high excitation levels in pulsed lasing mode (200 A, 100 ns, 10 kHz) are investigated and double-band lasing is reached.

Investigations of stimulated recombination processes and reasons of output optical power saturation at superhigh pump levels (up to 0.1 MA/cm²) of semiconductor lasers based on wide variety of quantum well heterostructures (&lgr;=980- 1900 nm) are presented for the first time.

The simplified model for electric-discharge XeCl-laser is presented. Although there are many reports on the models of XeCl-laser, for an analysis having clear physical sense it is useful to have a simplified kinetic model. The model enables to calculate an electrons concentration, density of excimer XeCl* molecules, specific energy deposition in active medium and generation energy. The quasi-steady mode of discharge in XeCl-lasers is analyzed. The influence of E/P on generation energy of quasi-steady mode of electro-discharge XeCl-lasers operation is discussed.

Laser national standards of Belarus, identical to the international standards, are prepared and accepted. Techniques for laser radiation measurements and measuring instruments calibration are worked out. Measuring systems for metrological maintenance of laser technical equipment have been created.

Reactively co-sputtered amorphous Al₂O₃ waveguide layers with low propagation losses have been deposited. In order to define channel waveguides in such Al₂O₃ films, the etching behaviour of Al₂O₃ has been investigated using an inductively coupled reactive ion etch system. The etch rate of Al₂O₃ and possible mask materials was studied by applying various common process gases and combinations of these gases, including CF₄/O₂, BCl₃, BCl₃/HBr and Cl₂. Based on a comparison of the etch rates and patterning feasibility of the different mask materials, a BCl₃/HBr plasma and and standard resist mask were used to fabricate channel waveguide structures. The etched structures exhibit straight sidewalls with minimal roughness and etch depths of up to 530 nm, sufficient for defining waveguides with strong optical confinement and low bending losses. Low additional propagation losses were measured in single-mode Al₂O₃ ridge waveguides defined using the developed etch process. In initial investigations, Al₂O₃:Er layers fabricated using the same deposition method applied for the undoped layers show typical emission cross-sections, low green upconversion luminescence and lifetimes up to 7 ms.

Integrated computational model for operation of co-doped Tm,Ho solid-state lasers is developed coupling (i) 8-level rate equations with (ii) TEM00 laser beam distribution, and (iii) complex heat dissipation model. Simulations done for Q-switched ≈0.1 J giant pulse generation by Tm,Ho:YLF laser show that ≈43 % of the 780 nm light diode side-pumped energy is directly transformed into the heat inside the crystal, whereas ≈45 % is the spontaneously emitted radiation from ³F₄, ⁵I₇ , ³H₄ and ³H₅ levels. In water-cooled operation this radiation is absorbed inside the thermal boundary layer where the heat transfer is dominated by heat conduction. In high-power operation the resulting temperature increase is shown to lead to (i) significant decrease in giant pulse energy and (ii) thermal lensing.

Progress in the development of efficient and reliable diode-pumped femtosecond laser systems based on both Kerr-lens and saturable-absorber mode locking is reported. Efficient Kerr-lens mode locking in diode pumped ytterbium-doped lasers, namely Yb:KY(WO₄)₂ (Yb:KYW) and Yb:YVO₄, is demonstrated with average output powers in excess of 1W, pulse durations around 100fs and electrical-to-optical efficiencies that exceed 15%. Novel semiconductor saturable absorbers based on InAs/InGaAs quantum dots are described and their applicability for efficient femtosecond pulse generation from near-infrared solid-state lasers is discussed. Efficient passive mode locking in the spectral regions around 1.3&mgr;m and 1.55&mgr;m in Cr:forsterite and the more recently developed Er, Yb:YAl₃(BO₄)₃ crystalline lasers has been demonstrated using low-loss InGaNAs saturable absorbers. A few examples of applications for this category of robust and efficient femtosecond lasers have been included. Specifically, the characteristics of a femtosecond visible light source producing pulses as short as 200fs at 520nm are outlined.

We present the design of an OPCPA (Optical Parametric Chirped Pulse Amplification) pre-amplifier incorporated in a visible (475 nm) high-contrast multiterawatt femtosecond laser chain based on hybrid (solid/gas) technology.

The results of experimental spectroscopic and laser investigations of ytterbium-doped partially (mixed) disordered tetragonal gadolinium-yttrium vanadate crystals at 5-300 K temperature range under laser diode pumping are presented and compared with yttrium vanadate crystals. The Yb:Gd_xY_1-xVO₄ (x=0.64) partially (mixed) disordered crystals demonstrate large stimulated emission cross-section compared with the values of Yb:YVO₄ crystals. Polarized absorption and fluorescence spectra in the 5-300 K temperature range are investigated and gain cross-sections are deduced at room and liquid nitrogen temperatures. The amplitudes of emission cross-sections are increased almost fourfold at liquid nitrogen temperature in comparison with the same at room temperature at wavelength near 1006 nm. The CW and ultrashort pulses generation with additional SESAM structure have been investigated in the folded resonator at 975 nm laser diode pumping at room temperature. At low temperature the estimations for different inversion population ratios show that duration of pulses are somewhat varied.

A powerful Yb-doped fiber laser with intra-cavity frequency doubling in KTP nonlinear crystal has been realized. Green output power of 1 W level has been achieved at ~ 11W of multimode laser diode pump power.

We report measurements of beat and birefringence correlation lengths, and the PMD value on a long single mode fiber. The proposed technique is based on the analysis of maximum and minimum polarization dependent gain in a fiber Raman amplifier. Results are consistent with a standard technique based on differential group delay measurements.

Glass doped with PbS quantum dots is presented as a saturable absorber for passive Q-switching of diode-pumped Tm:KYW laser. Output pulses with energy of 43 μJ at the repetition rate of 2.5 kHz were obtained. The slope efficiency with respect to the absorbed pump power was ~20%. Being compared in the same laser, PbS-doped glass saturable absorber outperforms Cr:ZnSe one in output power, pulse energy and slope efficiency.

New laser transition for 5.5 μm wavelength range was discovered in the moisture-resistant Dy³⁺:RbPb₂Cl₅ crystal. Pulse oscillation in free running mode was obtained under YAG:Nd laser pumping at 1.3 μm. Lasing slope efficiency was as high as 1% at room temperature. In line with our knowledge it is the longest laser wavelength for a rare earth doped crystal which does not require any special precautions to be survived.

High-repetition-pulse-rate nanosecond laser system is developed. It is based on Raman lasers with barium nitrate and KGW crystals. The minimum Raman threshold of laser generation corresponds to only 0.2-0.4 kW of peak pumping power. The laser system generates the radiation at 22 wavelengths in the 280-1600 nm spectral range with average powers from several mW to 1.4 W. The maximum Raman conversion efficiency reaches 40 %. The minimum spectral width of the generated radiation is equal to 0.1 cm^-1. This laser system can be used for spectroscopy studies, medicine, and for other applications.

New methods for precise control of main parameters of LD-pumped solid-state lasers assigned for spectroscopic applications have been developed. Tunable lasing in wide range has been achieved. Active elements on the base of crystals (Nd³⁺:YAG, Nd³⁺:YVO₄) and glasses (Er,Yb doped boro-silico-phosphate glass) were used. The active crystals with uniform and non-uniform distribution of the activator ions were studied. Output beams with high quality and polarization degree have been realized.

Our recent results on planar and channel waveguide fabrication and lasers in the dielectric oxide materials Ti:sapphire and rare-earth-ion-doped potassium yttrium double tungstate (KYW) are reviewed. We have employed waveguide fabrication methods such as liquid phase epitaxy and reactive ion etching as well as ion beam implantation and femtosecond laser writing. We have obtained surface and buried channel waveguide lasers in Ti:sapphire near 800 nm and planar waveguide lasers in KYW:Yb near 1 μm and KYW:Tm near 2 μm.

We demonstrate high-efficient CW thin disk 15%Tm:KYW laser pumped by a 20W CW laser diode bar at 803nm. Three 15%Tm:KYW b-cut disks of 200, 250 and 300&mgr;m thickness are tested, with the maximal laser output being of 4.9W at ~1.9&mgr;m. Slope and optical-to-optical conversion efficiencies are reported as well.

A brief overview of currently available methods applied in laser synthesis of 3D parts is presented, which range from stereolithography making use of liquid photopolymers to selective laser sintering of metal powders aimed at production of the parts of complex topology.

The properties of several Tm doped crystals regarding application in Q-switched tunable laser were analyzed theoretically. The acousto-optically Q-switched Tm:YLF laser is described in experimental part. The fiber coupled (0.4-mm core diameter) laser diode bar at 792-nm wavelength was deployed for pumping. The uncoated, with 3.5% dopant of thulium YLF rod of &slasho;3x8mm size wrapped with indium foil was mounted in copper heat-sink maintaining 293 K temperature of coolant water. Above 6 W of output power and near 50% slope efficiency with respect to absorbed pump power was demonstrated in free-running mode for a short, 40-mm long resonator. The quartz acousto-optic modulator with above 80% diffraction efficiency for 25-W power of RF was taken as the Q-switch for such a laser. In the best case of Q-switching mode up to 2-mJ output energy with 15-ns pulse duration corresponding to 100-kW peak power was demonstrated for rep. rate of a few Hz. Emission wavelength was around 1904 nm for both free-running and Q-switching regimes

The amplification of small signals was investigated both experimentally and theoretically. The theoretical analysis was provided in terms of unsaturated regime. It is shown, that it is necessary to take into account the temporal shapes of interacting waves. When pump pulse duration is of the order of hupersound phonons lifetime, the Stokes pulse has duration in two times lower then pump. It is necessary to have time delay between input Stokes pulse and pumping pulse of the order of life time of hupersound phonons to have amplification maximum. Energy amplification ~ 2•10⁹ was obtained experimentally when the energy of input signal was about 10^-11 J. The affect of the active medium SBS - amplifier parameters on SBS threshold is investigated. The universality of expression for a threshold increment of amplification, valid in a big range of change of parameters is shown. The threshold increment of amplification in the light guide in which spontaneous noise can amplify in big solid angle is experimentally confirmed. Experiments on SBS amplification in the light guide of small signal images are carried out. Amplification coefficient ~10⁶ is obtained without essential change of picture quality.

The results of the experimental investigations of the energy, temporal and spectral characteristics of the atomic fluorine laser radiation at 703, 713 and 731 nm wavelength pumped by pulsed cylindrical inductive discharge (PCID) are presented. The investigations of pulsed inductively coupled plasma radiation intensity under various pumping conditions have been performed. In the experiments a gas mixture He:F₂ - 100:1 as active medium was used. Total pressure was varied in the range of 0.1 - 300 torr. Maximum laser output radiation energy of 1.3 mJ in He:F₂ - 100:1 gas mixture under the pressure of 25 Torr was achieved. At the pressure of 25 Torr the lasing was observed on two lines (703 nm and 713 nm) with the stronger line at 703 nm and two times weaker line at 713 nm. With the pressure increasing higher than 30 Torr the generation energy was reduced due to the decreasing the 703 nm line intensity and the 731 nm line was appeared in the generation spectrum. The pulse duration was 40 ns (FWHM) that correspond to the peak pulse power of 30 kW. The laser beam had a ring form with outer diameter of 32 mm and thickness of 1.5-2.0 mm, and divergence of 0.4 mrad.

We present some results obtained by numerical modeling of the propagation of vortex beams with a spiral phase through a randomly inhomogeneous medium being presented by a phase screen placed in the beginning of the propagation path. Such beams, if propagated under conditions of weak turbulence, also experience distortions, like Gaussian beams. However, the statistically averaged vortex beams conserve the central intensity dip with a nonzero intensity on the beam axis. The greater the beam vortex charge, the longer the beam propagation distance, at which the central dip is not smeared. The vortex beams being the Laguerre-Gaussian modes are found to have the same broadening properties while propagated through a randomly inhomogeneous medium as the Gaussian beams. The broadening of averaged vortex beams does not depend on the vortex charge and coincides with the broadening of a Gaussian beam.

A method has been suggested for description of the azimuthally and radially polarized modes that excludes any inherent contradictions and unjustified approximations. The solutions are in accordance with Maxwell equation ∇E=0, and the wave equation. This allowed the analytical calculation of the field components for these modes, including the longitudinal one. The formulae of field distribution at sharp focusing are presented for the arbitrary-order IPM. Generation of high power (up to 2 kW) beams with axial-symmetric polarization (ASP) in stable resonator of industrial CO₂-laser with diffraction gratings or V-axicon have been realized. The transformation of azimuthally polarized mode to radially polarized mode was demonstrated.

Lasing on electronic transitions of molecular nitrogen in pulsed inductively coupled plasma with radiation wavelength of 337 nm in the UV range of a spectrum is reported. The results of experimental investigations of the dependence of molecular nitrogen radiation intensity in the inductive discharge on the excitation parameters are presented. In the experiments pure nitrogen and its mixtures with He, Ne, Ar and CF₂Cl₂ have been used. The maximal output radiation energy of 1.2 mJ has been achieved at the excitation of pure nitrogen under the pressure of 0.3-0.4 Torr. The pulse duration (FWHM) was of 12 ± 1 ns and the peak pulse power was of 100 kW. The laser beam had a ring form with the divergence of 0.3 mrad. The instability of laser radiation pulses was of ±2%, at the stability of voltage amplitude in electric excitation system equal of ±2%.

The kinetic model of fast-flow CO₂-laser is represented. The dependences of the output power and the efficiency of such CO₂-laser on the pumping power are considered. The role of the active medium temperature and its fast flow in obtaining the maximal laser efficiency are discussed. The selectivity of pumping and excitation rate of the upper laser level are the main parameters defining the efficiency of the fast-flow CO₂-lasers is shown.

Information capacity for unsaturated gain regime is proposed as new figure of merit for host glasses for Er-doped fiber amplifiers that are considered as components of optical communication systems. Silicate and phosphate glasses are proved to have the highest total information capacity over the S-, C- and L-bands. In wideband communication systems tellurite glasses are shown to have the maximum capacity.

Numerical simulation of broadband fiber Raman amplifiers with multiple pumps is carried out. Rayleigh scattering, amplified spontaneous emission and signal-to-signal, pump-to-pump and signal-to-pump conversions are taken into account. Special emphasis is placed on the noise performance of the amplifiers. Calculation of ultimate spectral efficiency of information transmission and capacity of fiber Raman amplifiers is fulfilled.

The results of spectroscopy of disordered Tm-doped calcium-niobium- gallium garnets (CNGG) are displayed. Based on the Judd-Ofelt theory, three intensity parameters were obtained. Gain cross-section for laser transition ³F₄→³H₆ of Tm³⁺ ions was obtained using absorption and emission cross-data for transition ³H₆→³F₄ and ³F₄→³H₆ respectively. The laser emission is reported in Tm:CNGG (transition ³F₄→³H₆) at room temperature with laser diode pumping.

Early observed peculiarities of ZnO random laser spectra are analyzed. By simplified simulation of lasing time behavior it is shown that plausible origin of lasing spectra variations from shot to shot can be the fluctuations of the number of spontaneous photons that can serve as a "seed" for laser effect creation in a certain mode. Such fluctuations are very significant for spatially overlapping modes. Analysis of a statistics of different line appearance in the lasing spectra showed that the number of lasing modes in monodisperse sample is less than in polydisperse ones. This finding can explain why lasing spectra variations are more pronounced in polydisperse samples. We associate observed large line widths with the existence of several lasing acts during every pumping shot and with the slight changes of some modes frequencies in the course of each lasing act. Preliminary experimental result confirms such supposition.

High quality mixed vanadate monocrystals Nd:Gd _0.7Y_0.3 VO₄ with dimensions up to Ø 25x70 mm and Nd ions concentration of 0.5% were grown. Diode pumped laser based on this crystal demonstrates lasing with output power up to 9.8 W at wavelength 1063.6 nm with slope and total efficiencies 66% and 64%, respectively. Thermooptical characteristics of this mixed vanadate crystal and Nd:GdVO₄ crystal were directly measured and compared.

The growth conditions of single crystals of the new double tungstate of sodium and aluminum, NaAl(WO₄)₂ have been investigated. Data have been obtained on the concentration and temperature regions of crystallization of this compound in the system Na₂O-Al₂O₃-WO₃. Nontsoichiometric high-temperature solutions with very low crystallization temperatures, low viscosity and absence of volatility have been found and used for growing pure and differently Cr³⁺- doped single crystals of NaAl(WO₄)₂ by the top seeded solution growth (TSSG) slow cooling. technique. The main defects of the crystals obtained have been established, the reasons for their appearance analysed and single crystals free from inclusions were grown. Measurements of the optical characteristics of samples with chromium concentrations in the range 1.4x 10¹⁹-1.3x 10²⁰ atoms/cm³ were carried out. Absorption and luminescence spectra of Cr³⁺ : NaAl(WO₄)₂ were obtained at temperatures between 6 and 300 K and the temperature dependence of the Cr³⁺ luminescence lifetime was established. The Dq/B value found indicates that Cr³⁺:NaAl(WO₄)₂ belongs to the intermediate field site crystals. The results show that the new crystal is a good candidate for broadband laser applications.

Pump conditions optimization is performed for erbium-doped fiber amplifier with dual wavelength bidirectional quasi-two- level pumping to obtain low noise figure, high efficiency of pump power conversion and sufficiently wide and flat gain spectrum in L-band.

We propose and study both numerically and experimentally a laser system controlled by the combination of positive and negative feedbacks capable to generate a long picosecond pulse train of stable amplitude as well as regular pulsation with sub-microsecond period. The proper combination of feedbacks is realized in a Nd:YAG laser with millisecond pumping by means of a single optoelectronic negative feedback which utilizes signal reflected from an intracavity Pockels cell polarizer. Regular pulsation (microgroups of picosecond pulses) with controlled period from 25 to 75 resonator round trips is obtained. The development of chaotic dynamics displayed by the system at higher pumping level differs from the Feigenbaum scenario. The regular pulsation regime has a great potential in a laser-electron X-ray generator design and other applications.

New results on the influence of the composition of a silica gel-matrix and the process of its production on the spectral, lasing and photochemical properties of embedded luminophores: rhodamine, phenalemine, oxazole, coumarine and other dyes series, which have lasing in the UV, blue-green and red spectral regions under excitation by poweful laser radiation of various wavelength (308 and 532 nm) and intensity (from 0,1 to 100 MW/cm²) have been obtained. The shortest-wavelength lasing is achieved for silica solid matrices with para-terphenyl (342 nm). Optimal conditions have been selected and the lasing of thin silica solid films doped with aminocoumarine (457 nm) with resource exceeding that in solutions has been obtained. It is established, that organic luminophores are fixed in nanodimensional pores of silica and hybrid matrices by specific interactions, that compete with the association of dyes.

The modeling of erbium-doped fiber amplifier with three-level forward pumping and quasi-two-level backward pumping has been performed. The optimal pumping conditions for achievement of the flattest gain spectrum have been found by means of genetic algorithm.

The improved method for calculating the Lyot filter parameters has been developed. The two-plate and three-plate Lyot filters transmission spectra for the low threshold lasers tuned in the 1100-1300 nm spectral region are computed.

The terawatt picosecond CO₂-laser design is considered in the paper. The CO₂-laser system includes itself the following units: a) master oscillator with variable pulse width of 100 ps, and b) laser pre-amplifier being developed on a basis of a ring optical scheme and operating under the gas pressure of 3 atm. Both experimental and theoretical analysis of the CO₂-laser system is carried out.

To control the process parameter settings and to visually inspect the process quality, a monitoring system for the sintering process was designed. The monitoring of the sintering process is based on measurements of the maximum surface temperature and the temperature distribution at the sintering zone by the spectral ratio method. Software and hardware for adaptive process control of powder solids SLS were developed.

In this work we have performed the experimental researches of features for the generation of supercontinuum in laser materials with identical chemical composition: Yb:YAG crystal and Yb:YAG laser nanoceramics. Dependence of width of supercontinuum spectrum in 515-1100 nm spectral range on femtosecond radiation intensity was investigated. At laser intensity ~1.2•10¹⁴ W/cm² the short-wave wing of a spectrum for nanoceramics has greater intensity and more flat shape in comparison with crystal. Experiments were made at lens focusing of the Ti:Sapphire femtosecond laser system radiation with energy up to 0.5 mJ in explored sample that was inside of integrating optical sphere. Also we investigated the interaction of femtosecond laser pulses and the generation of supercontinuum in Nd:Y₂O₃ nanoceramics. The maximum value of laser intensity in experiments was restricted by optical breakdown on target output surface, i.e. was below threshold of ablation of sample substance.

Results of farther investigation of three mirror diode lasers operated at active mode-locking are presented in this paper. The maximum value of intermode frequency stability is 5.92×10^-14 (average time 10 sec.) at stability of pumping microwave oscillator equals to 4×10^-14. It was obtained that main factor has affected intermode beat stability is frequency pulling effect.

The elastic and thermo-optical properties of chrysoberyl, beryllium hexaaluminate and beryllium-lanthanum hexaaluminate crystals have been experimentally studied. The velocities of elastic-wave propagation in the crystals are measured by acousto-optic interference method. The values of all the independent components of elastic-constant tensor are determined and used to calculate a number of important dynamic parameters of the crystals such as the Young's and shear moduli, the modulus of volume elasticity, Poisson's ratio, the Debye temperature. Also measurements of refractive indices in 25 - 75 C temperature range in VIS spectral region were performed. Using experimental data the dispersion of thermal optical coefficients (dn/dT) was calculated, these data were employed to evaluate the thermal lens in beryllium containing laser crystals. The experimental and calculated data are compared with similar parameters for well-known laser hosts. Some of beryllium containing oxide crystals was shown to be candidates for master oscillator and amplifying stages of high power femtosecond laser systems.

The application of a single-pulse position modulation (SPPM) and a new concatenated single-pulse position modulation (CPPM) for data transmission in optical indoor channels is shown. The numerical analysis of the extended multi-pulse position modulation (MPPM) and CPPM for information transmission done in aspects of bandwidth, power efficiency and symbol error probability (SER) has shown the better performance of CPPM and MPPM than SPPM at the cost of increased bandwidth. The obtained simulation results of SER for modulation schemes are close to theoretical SER evaluation and have shown the increase of power spectral density (PSD) of MPPM in comparison with SPPM.

Operation of Nd:YAG triangle slab laser side pumped by 600 W quasiicontinuous laser diode passively mode locked using semiconductor saturable absorber is reported. Pulse trains with energy up to 2 mJ and pulse duration of 65 ps were generated and pulse shortening by passive negative feedback introduced due to the beam defocusing in GaAs saturable absorber substrate was measured.

In the report building and application questions of picosecond terawatt CO₂ laser installations are presented. The design and the description of the basic components of middle-infrared picosecond laser facility (MIRPLF) with terawatt power of 10 &mgr;m laser radiation manufacturing by efforts of institutes NIIKIOEP and NIIEFA are presented. The main attention is paid to questions of design of the master oscillator with pulse with 10÷100 ps and the final laser CO₂ high pressure amplifier (HPA) with the intermediate water capacitor integrated in to the gas-discharge chamber. The main results of experimental investigations of characteristics of MIRPLF components are presented and prospects of MIRPLF projected peak power increasing are analyzed.

Semi-classical theory of Q-switched microchip - lasers with transient and quasi-stationary intracavity Raman conversion has been developed. Rate wave equations describing generation of Stokes pulses of different orders and their multiwave mixing have been written and discussed in detail. Theoretical results agree well with experiments for passively Q-switched microchip - lasers with intracavity Raman conversion in crystals of Ba(NO₃)₂ and CaMoO₄. It is shown, that intracavity Raman conversion in microchip - lasers represents a simple and effective method of generation of short Stokes pulses with duration as short as 100 ps, energy in the &mgr;J-range and peak power of up to several tens of kW.

Holographic characteristics of a thick self-developing photosensitive medium - dye-doped jelly-like gelatin are investigated by means of pulsed laser exposure. The experiments were performed using aqueous gelatin solutions of Rhodamin 6G with a layer thickness of 1 mm. The slanted holographic gratings were written with two crossed beams from a frequency-doubled (λ = 532 nm) and Q-switched YAG:Nd laser (τ_0.5 ≈ 17 ns, f ≤ 50 Hz). In the course of recording the hologram was read with the beam from a single-mode He-Ne laser (λ = 632.8 nm) which was not absorbed by the photosensitive medium. The real-time evolution of the grating diffraction efficiency was studied in dependence of the dye and gelatin concentration as well as the writing pulse fluence. It is shown that under appropriate choice of the medium composition and parameters of the recording radiation, it is possible to obtain phase volume holographic gratings with a diffraction efficiency of ~ 87 % and an angular selectivity of ~ 20'.

The dynamics of pulse trains formation in a cavity of Nd:YAG laser with passive dye-activated thin film and nonlinear negative feedback was studied. The maximum duration of extended pulse trains (6.5 &mgr;s) was experimentally achieved.

In the present work, a new approach to long-term stabilisation of radiation frequency generated by single-frequency lasers has been experimentally demonstrated. The essence of this approach is in the use of high-precision radiation wavelength meter as a spectral reference. For the first time the method was experimentally demonstrated for reduction of long-term radiation line drift of single-frequency CW Ti:Sapphire / Dye lasers. Generation line drift of lasers was reduced approximately by an order of magnitude down to 40 MHz/hour, which corresponds to the residual drift in readings of the wavelength meter itself. The implemented automatic frequency control system allows to locks the laser generation frequency to a specified absolute value. This approach may be used in single-frequency lasers of different types (solid-state, fibre, diode, dye lasers, etc.) and allows reduction by an order of magnitude or more of the long-term generation line drift in lasers which are not equipped with other systems for long-term stabilisation of output radiation frequency.

A single-frequency continuous wave diode-pumped Nd:YVO₄ laser emitting high-quality polarized beam at 914 nm is presented. An intracavity etalon with a free spectral range of 500 GHz was used to obtain single-mode operation in a short linear cavity. Smooth frequency tuning over a range of 5GHz was demonstrated. A laser output of 300 mW was obtained at the half frequency of the ¹S₀→³P₁ transition of Mg²⁴ atoms (327.830 THz). The second harmonic of this laser can be used for high-resolution spectroscopy of magnesium atoms.

1 mJ pulse energy with a pulse duration less 300 ps was achieved in Nd⁺³:YAG/Cr⁺⁴:YAG microchip laser. To overcome the polarization instability an output coupler sensitive to polarization was designed, using a multilayer dielectric mirror evaporated on a substrate made of a birefringent calcite crystal. Reflection coefficients for ordinary and extraordinary beams R_o = 53% and R_e = 57% were obtained. Subnanosecond laser operating at 1064 nm, 532 nm and 355 nm wavelengths with high output brightness and intensity was constructed.

We report on dual active element Yb:KGW regenerative amplifier that provides ultrashort pulses in the 0.3 mJ range at high repetition rates. Each active element was pumped by two 50 W diode pump modules at 980 nm. 30W average power was obtained at 100 kHz repetition rate. Measured spectrum width of 5,4 nm allows for compression of amplified pulses to sub-300 fs pulse duration. As output power increases above 15 W nearly symmetrical Gaussian profile beam becomes slightly elliptical, although remains Gaussian in transverse directions. The measured beam quality parameter M² is below 1,5 even at maximum output power.

We report on high beam quality diode end-pumped Q-switched Yb:YAG laser with elliptical cavity mode configuration operating at 1÷100 kHz repetition rates. Laser coupler transmittance optimization in CW is carried out. Measurements of thermal lens in laser active element by means of Shack-Hartmann wavefront sensor are presented. It is shown that thermal lens in such laser is highly astigmatic. We have also measured laser beam quality parameter M², which does not exceed 1.2 value at the highest pump power.

Quantum statistical theory of radiation-balanced laser is constructed within method of nonequilibrium statistical operator. System of equations is derived for number of phonons and collective population difference. Their numerical solutions are obtained and discussed.

Total gain exceeding 10² and a small-signal gain of 2x10^-3 cm^-1 are observed in a photolytically driven femtosecond XeF(C-A) amplifier in the regime of a homogeneous gain distribution over the active volume. These values, being compared with the results of measurements of the pumping radiation power, show that the spectral quantum efficiency of the XeF(B) formation as a result of the XeF₂ photodissociation (related to an absorbed photon) approaches unity in the VUV spectral range.

We show that a two-level active sample of one-dimensional photonic crystal can generate chaotic sequence of extremely short pulses in the absence of mirrors. Numerical analysis and optimization of this promising superradiant laser is presented.

The theoretical analysis of the influence of a volume electron-ionic recombination on energy and spatial characteristics of the glow discharge plasma of the positive column in gases is developed taking into account the equation for a longitudinal electric field and Ohm's low for a full electrical current. It is shown, that under certain conditions, even in the diffusion mode of glow discharge, this influence reduces to essential modifications of the internal discharge parameters (electron temperature, electron concentration at the tube axis and longitudinal electric field). Dependences of the internal gas discharge plasma parameters on the external ones, such as gas pressure, the discharge current, the radius of working capillary are considered for the narrow gas discharge tubes.

The optimum conditions of excitation in a two-spool laser are determined, in which the pumping of a solid laser on the basis of nanoporous glass - polymer composite with the inserted dyes is made by a laser on dyes emission with a lamp pumping of microsecond duration, which provides overlapping of a broad spectral range with laser momentums with energy up to 500 mJ at the duration of 1 mcs and the divergence of 1 millirad and the increase of the radiance in 140-700 times.

This PDF file containes the front matter associated with SPIE Proceedings Volume 6711, including Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.