Continuous chemical HF laser with a modified radially expanding nozzle unit

We have determined experimentally the energy and spectral characteristics of a supersonic continuous chemical HF laser (oscillator) with a modified radially expanding nozzle unit operating according to the “nozzle–injector–injector” scheme of mixing reactants based on a new method of obtaining oxidizing gas. The practical realization of measures to decrease the heat loss and the loss of fluorine atoms, as well as the optimization of the mode of operation of the modified laser, permitted a 30% increase in its radiation power compared to the base oscillator equipped with a nozzle unit operating according to the “nozzle–injector” mixing scheme. Ways of further enhancement of the energy characteristics of the HF laser radiation are proposed.     

Calculation of the characteristics of a mixing CO2 gasdynamic laser with a nozzle unit of honeycomb construction

A mathematical model of a gasdynamic laser with parallel supersonic mixing of the components and its applications to the choice of the geometrical characteristics of the nozzle unit of honeycomb construction are presented.Notation T static temperature - u velocity - P pressure - molecular weight - e_i average number of vibrational quanta - k amplification ratio for a weak signal - I radiation intensity - _i molar fraction of the component in the mixture - ^* displacement thickness - r, d current radius and diameter of the nozzle - angle of inclination of the generating profile of the nozzle and characteristic temperature - h enthalpy - G flow rate - L characteristic length - A/A* expansion ratio of the nozzle - T_w wall temperature - ¯T_w=¯T_w/T_o temperature factor - =E _a /E_* nozzle efficiency - E stored vibrational energy - X=X/(r_a1 + r_a2) dimensionless coordinate Indices 1 radiating gas stream - 2 exciting gas stream - 0 stagnation value - a, *, values at the cut of the nozzle, in its critical cross section, and beyond the compression shock in the cross section of the nozzle cut Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 47, No. 1, pp. 53–59, July, 1984.     

Thermal deformation of the active medium in a solid-state laser with natural cooling

An analytical expression is derived for the transient thermal deformation of the active medium in a periodic duty laser with natural cooling.Notation W thermooptical constant of the active medium - n refractive index of the active medium - k thermal expansivity of the active medium - thermal conductivity of the active medium - a thermal diffusivity of the active medium - L length of the active medium - 2R diameter of the active medium - H distance from axis of the pump lamp to the axis of the active medium - _i=t_i – t_a excess temperature - t_i temperature of the i-th element - t_a ambient temperature - P_i power of heat generation within the i-th element - C_i total thermal capacity of the i-th element - P_ij thermal flux from body i to body j (i, j=1, 2, 3) - _ij thermal conductance between body i and body j (i, j=1, 2, 3) - _ij heat-transfer coefficient from body i to body j (i, j=1, 2, 3) - P average pump power - time - 1 pump lamp - 2 active medium - 3 luminaire envelope Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 42, No. 1, pp. 85–91, January, 1982.     

Experiments with active phase matching of parallel-amplified Multiline HF laser beams by a phase-locked Mach-Zehnder interferometer

Active phase matching of multiline HF laser beams by means of a phase-locked Mach-Zehnder interferometer was demonstrated by locking the interferometer to the central interference fringe at zero optical path length difference. The central fringe could be found by varying the spectral content of the input beam. Laser amplification in one leg of the interferometer decreased fringe visibility without adversely affecting locking. Single-line fringe patterns produced by an array spectrometer (while the interferometer was operated in its scanning mode) were analyzed to show that no significant dispersion occurred in the amplifier. The techniques developed have potential for measuring dispersion mismatch between larger parallel amplifiers. These experiments demonstrated in principle that a number of multiline HF amplified beams can be recombined and phase-matched to produce a high beam quality output beam.     

Stabilized laser radiation frequency shift under perturbations of the active medium

Translated from Izmeritel'naya Tekhnika, No. 8, pp. 30–31, August, 1989.     

Discharge of a gaseous medium under high pressure through a nozzle with a small opening

It is shown experimentally that the nature of the discharge of gaseous nitrogen under a pressure of up to 12 kbar through a nozzle with a small opening with a ratio of the length of the cylindrical section of the channel to its diameter of about unity is close to isentropic.     

Modeling of the refraction of a laser sheet in transparent radially nonuniform media

The problem of the refraction of a laser sheet in a transparent spherical nonuniformity, for example, in the liquid of a thermal lens, is solved. Equations of the projection of the laser sheet, passing through the nonuniformity, are obtained. It is shown that by using projections of the laser sheet one can determine the sign of the nonuniformity gradient and its order of magnitude, and also establish the parameters of the specified model of the nonuniformity. __________ Translated from Izmeritel’naya Tekhnika, No. 10, pp. 49–52, October, 2006.     

Flow with convective acceleration through a porous medium

Summary The flow streaming into a porous and permeable medium with arbitrary but smooth wall surface is considered on the basis of the Euler equation (in the pure fluid region) and a generalized Darcy's law in which the convective acceleration is taken into account. The asymptotic behavior of the flow for small permeability of the medium is investigated. It is shown that the flow in the porous medium is irrotational except in the boundary layer next to the surface. The velocity distribution in the boundary layer is given in a universal form. Proper boundary conditions connecting the potential flow in the pure fluid region and the potential flow in the porous medium are obtained when the boundary layer is neglected.On leave from Department of Aeronautical Engineering, Kyoto University, Kyoto, Japan.     

Thermally stressed state and optical quality of a glass active medium of a powerful solid-state laser

Results of a comprehensive investigation of a thermally stressed state and optical quality of a cylindric active medium of a high-power solid-state laser are presented. A comparative analysis of the effects of the temperature-induced gradient of the refractive index, variation of the shape of the active medium, and induced birefringence is carried out. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 6, pp. 1020–1024, November–December, 1997.     

Flow of a liquid-gas mixture in a contoured nozzle with constant phase velocity difference

A one-dimensional approximation is used to examine simultaneous flow of a gas and of liquid drops in a shaped nozzle under conditions of constant velocity difference between the phases. The nozzle profile to achieve this flow is determined. The parameters of the gas-liquid mixture are obtained in explicit form as a function of the dimensionless gas velocity.     

Errors in reproducing the planar-angle unit with a ring laser

Translated from Izmeritel'naya Tekhnika, No. 12, pp. 11–12, December, 1989.     

Numerical simulation of an optically active medium of an OD-CO2 laser

A quasi-one-dimensional model of an optically active medium of a chemical OD-CO₂ laser with thermal initiation is proposed. Results of calculations are. in good agreement with the experiment. The maximal specific power of generation is 66 J/g.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 61, No. 6, pp. 885–894, December, 1991.     

Manifestation of active medium astigmatism at transverse mode locking in a diode end-pumped stable resonator laser

Transverse mode locking in a diode end-pumped Nd:YAG laser with up to approximately 140 cm resonator length was investigated. It was found that for each resonator degeneracy, there are two degenerate lengths where the fundamental mode is very different from the Gaussian mode. Fundamental mode intensity patterns for these lengths expand in directions perpendicular to each other. Experimental results are in a good agreement with numerical calculations, taking into account active medium (AM) astigmatism and inhomogeneous gain. Optical powers of astigmatic AM can be found directly from measurements of degenerate lengths without using numerical modeling.     

Flow of an anomalous viscous fluid in a centrifugal jet nozzle

The motion of twisted flows of an anomalous viscous fluid subject to an exponential law has been studied numerically.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 57, No. 6, pp. 900–906, December, 1989.     

Study of conjugate heat transfer in the nozzle grid of a gas-dynamic laser

The characteristics of the flow and heat transfer in the nozzle grid of a gas-dynamic laser in the presence and absence of cooling of the blades are studied numerically in a conjugate formulation.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 52, No. 5, pp. 736–743, May, 1987.     

Special features of the interferometry of radially loaded large glass laser matrices

We present the results of computational investigation of the loss in contrast of interference patterns of lateral shear with a reference beam. We consider the behavior of the degree of coherence over the active element cross-section and in time after starting the laser pumping system in operation, as well as the behavior of the integral degree of probing-radiation depolarization. D. F. Ustinov Baltic State Technical University, St. Petersburg, Russia. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 5, pp. 783–786, September–October, 1997.     

Photo-thermo-refractive glass co-doped with Nd as a new laser medium

Photo-thermo-refractive (PTR) glass demonstrates refractive index change after exposure to UV radiation followed by a thermal treatment that enables recording of high efficiency holographic optical elements. This work demonstrates feasibility of function of this material as a complex optical medium which posseses both photosensitive and luminescent properties and paves a way for creation of monolythic solid state lasers where resonator components can be holographically recorded inside of a laser medium. It was found, that incorporating of Nd³⁺ ions in PTR glass does not affect photosensitivity required for hologram recording. It was demonstrated that emission wavelength, spectral width, and cross section of Nd³⁺ luminescence in PTR glass are typical for silicate laser glasses and Nd-doped PTR glass can be considered as a promising laser medium for monolithic solid state lasers.