Showing papers in "Soviet Journal of Quantum Electronics in 1979"
TL;DR: In this paper, a study was made of wavefront reversal, accompanying stimulated Brillouin scattering in various media, and of the way it was affected by the geometrical, temporal, and polarization characteristics of the exciting radiation.
Abstract: A study was made of wavefront reversal, accompanying stimulated Brillouin scattering in various media, and of the way it was affected by the geometrical, temporal, and polarization characteristics of the exciting radiation. In an oscillator-amplifier system, practically complete compensation was achieved for phase distortions of the oscillator signal introduced by the amplifier components. The output energy of the light beam was then 3 J, its diameter was 4 mm, and its divergence (diffraction limited) was 0.3 mrad. The results of the experiments indicated a practical possibility of applying the wavefront reversal phenomenon in high-power multichannel lasers.
65 citations
TL;DR: In this article, a method for small-signal wavefront reversal during stimulated Brillouin scattering in an optical waveguide was proposed and implemented for nanosecond pulses, which may find applications in the wave-front reversal of nanoscond pulses.
Abstract: A method is proposed and implemented for small-signal wavefront reversal during stimulated Brillouin scattering in an optical waveguide. This method may find applications in the wavefront reversal of nanosecond pulses.
38 citations
TL;DR: In this paper, an analysis of the mode structure of a plane-parallel resonator with wavefront-reversing mirrors is made, and an integral equation is derived for the oscillation modes of the resonator.
Abstract: An analysis is made of the mode structure of a plane-parallel resonator with wavefront-reversing mirrors. An integral equation is derived for the oscillation modes of the resonator. It is shown that these modes are identical with those in a confocal resonator of the same length.
35 citations
TL;DR: In this article, an x-ray schlieren method is proposed for monitoring shell targets used in laser thermonuclear fusion experiments, based on a two-crystal diffractometer.
Abstract: An x-ray schlieren method is proposed for monitoring shell targets used in laser thermonuclear fusion experiments. This method is based on a two-crystal diffractometer. Magnified one-dimensional photographs of shell targets obtained by this method demonstrate the possibility of determining shell thicknesses of ≥3μ with an accuracy of ±0.15μ.
33 citations
TL;DR: In this article, a theoretical analysis of wavefront reversal of depolarized light in the four-photon interaction is made and methods for implementing full spatial-polarization reversal are suggested.
Abstract: A theoretical analysis is made of wavefront reversal of depolarized light in the four-photon interaction. Methods for implementing full spatial-polarization reversal are suggested.
32 citations
TL;DR: A review of experiments carried out to date on the generation of laser radiation frequency harmonics in a plasma on exposure to neodymium, ruby, and CO2 lasers is given in this paper.
Abstract: A review is given of experiments carried out to date on the generation of laser radiation frequency harmonics in a plasma on exposure to neodymium, ruby, and CO2 lasers. A physical picture of second harmonic generation in a laser plasma is developed on the basis of an analysis of theoretical and experimental investigations. Experiments involving the spherical irradiation of solid targets carried out in the Kal'mar laser system made it possible to identify for the first time the processes taking place in the critical-density plasma region under conditions as close as possible to "thermonuclear". New methods are proposed for ultrafast diagnostics of a transient superdense plasma using the second harmonic radiation spectrum.
28 citations
TL;DR: In this article, thermal strains in disk, cylindrical, and rectangular active elements made of KCl, LiF, and CaF2 crystals, used in color-center lasers, are analyzed.
Abstract: Analytic calculations are made of thermal strains in disk, cylindrical, and rectangular active elements made of KCl, LiF, and CaF2 crystals, used in color-center lasers. Expressions are obtained for the thermooptic characteristics and calculations are made of their numerical values.
27 citations
TL;DR: In this article, an experimental study was made of the heating of metal targets by CO2 laser pulses of intensity 1-100 MW/cm2 at various air pressures (10-5-1 atm).
Abstract: An experimental study was made of the heating of metal targets by CO2 laser pulses of intensity 1–100 MW/cm2 at various air pressures (10–5–1 atm). Initiation of breakdown in the vapor of the target material or of low-threshold breakdown in air increased considerably the deposition of the laser energy in the target. A size effect was then observed: the effective absorptivity of metal targets increased when the ratio of their radius to the radius of the illuminated spot was made larger. The results were explained by the contact of the breakdown plasma with the target surface in the course of the former's expansion into the ambient medium.
25 citations
TL;DR: In this paper, the C(3/2)-A( 3/2) transition in the XeF excimer pumped by vacuum ultraviolet radiation from open high-current discharges in mixtures containing XeFs, N2, and Ar was observed in the wavelength range 455-495 nm.
Abstract: Stimulated emission was observed in the wavelength range 455–495 nm due to the C(3/2)-A(3/2) transition in the XeF excimer pumped by vacuum ultraviolet radiation from open high-current discharges in mixtures containing XeF2, N2, and Ar. The duration of the stimulated emission pulses was 1.5μsec and their energy was 4 mJ.
24 citations
TL;DR: An efficient Raman laser utilizing stimulated Raman scattering by rotational levels in gaseous hydrogen was built and investigated in this article, where coherent summation of 50 neodymium laser beams into a single spatially coherent optical beam was achieved with an efficiency of 70% under conditions of saturated amplification of an external signal in the Raman amplifier.
Abstract: An efficient Raman laser utilizing stimulated Raman scattering by rotational levels in gaseous hydrogen was built and investigated. Coherent summation of 50 neodymium laser beams into a single spatially coherent optical beam at the frequency of the first Stokes component νs = 8856 cm–1 was achieved with an efficiency of 70% under conditions of saturated amplification of an external signal in the Raman amplifier.
23 citations
TL;DR: In this article, the excitation conditions for lasing in copper vapor were optimized and a maximum efficiency of 3% was obtained, which is the same as the maximum efficiency achieved in this paper.
Abstract: The excitation conditions for lasing in copper vapor were optimized and a maximum efficiency of 3% was obtained.
TL;DR: In this paper, the phase diagram of the Hgs-HgGa2S4 system was investigated and a phase-matching diagram was plotted for an o + o→e frequency mixing process.
Abstract: An investigation was made of the phase diagram of the Hgs–HgGa2S4 system. It was shown that there is a region of HgGa2S4-based solid solutions. Optically homogeneous mercury thiogallate single crystals were grown and used to measure the refractive indices in the 0.55–11 μ range. A phase-matching diagram was plotted for an o + o→e frequency mixing process. This diagram confirmed phase-matched interaction in the specified wave-length range.
TL;DR: Stimulated emission was observed when ZnTe, ZnSe, and CdS single crystals were exposed to two-photon excitation by a train of ruby laser picosecond pulses.
Abstract: Stimulated emission was observed when ZnTe, ZnSe, and CdS single crystals were exposed to two-photon excitation by a train of ruby laser picosecond pulses The lasing wavelengths for ZnTe, ZnSe, and CdS crystals were 530, 450, and 495 nm, respectively The angular divergence was 19–21° and the laser action occurred at peak exciting pulse intensities of around 1 GW/cm2
TL;DR: In this paper, the proportion of the spontaneous radiation energy transmitted by the passive GaAlAs layers and absorbed outside the active layer is calculated, which is required to calculate the temperature distribution inside a laser diode.
Abstract: Calculations of the parameter ƒ, which determines the proportion of the spontaneous radiation energy transmitted by the passive GaAlAs layers and absorbed outside the active layer, are presented. The value of ƒ is required to calculate the temperature distribution inside a laser diode. It is found that the value of ƒ for a typical GaAs–Al0.3Ga0.7As single-heterostructure laser diode (thickness of active layer d = 2μ and resonator length L = 400 μ) is approximately 0.335 and that for a symmetric double-heterostructure laser diode (d =0.2μ, L =400μ) is 0.671. In stripe-geometry laser diodes with a typical stripe width W = 10μ, the values of ƒ are reduced to 0.271 and 0.658 for similar single- and double-hererostructure lasers, respectively.
TL;DR: In this article, a study was made of the possibility of holographic recording of data in LiNbO3:Fe crystals and of their readout with light of different wavelengths so as to avoid optical erasure.
Abstract: A study was made of the possibility of holographic recording of data in LiNbO3:Fe crystals and of their readout with light of different wavelengths so as to avoid optical erasure. The holograms were recorded using light of wavelengths λ = 0.44 and 0.63 μ and read out with light of wavelengths λ = 0.69, 0.9, and 1.06 μ. There was no erasure when readout light of the wavelength λ = 1.06 μ and power density 30 W/cm2 was used for one hour. Measurements of the diffraction efficiency of the same hologram at different wavelengths indicated that the photorefraction effect was independent of the readout wavelength. An experimental study of the recording and readout of Fourier holograms of transparencies at different wavelengths demonstrated that all the recorded data could be recovered by varying the angle of incidence of the readout beam.
TL;DR: In this paper, an analysis is made of the problem of determination of the oscillation modes in a plane-parallel resonator with one wavefront-reversing mirror, where no restrictions are imposed on the dimensions of the mirrors forming the resonator.
Abstract: An analysis is made of the problem of determination of the oscillation modes in a plane-parallel resonator with one wavefront-reversing mirror. No restrictions are imposed on the dimensions of the mirrors forming the resonator. Expressions are obtained for the fields of the oscillation modes on the mirrors. It is shown that these fields are in the form of Gaussian-Hermitian beams with parameters depending on the ratio of the transverse dimensions of the mirrors.
TL;DR: In this article, an experimental investigation was made of stimulated Raman scattering (STRS) of single-mode and multimode optical beams and it was shown that under conditions of pumping by a singlemode beam at an excess over the parallel STRS threshold, the Stokes wave divergence increases rapidly and the contribution to the axial intensity of the radiation propagating in the far field zone is mainly governed by a comparatively small part of a laser pulse at subthreshold power.
Abstract: An experimental investigation was made of stimulated Raman scattering (STRS) of single-mode and multimode optical beams. It was found that under conditions of pumping by a single-mode beam at an excess over the parallel STRS threshold, the Stokes wave divergence increases rapidly and the contribution to the axial intensity of the radiation propagating in the far-field zone is mainly governed by a comparatively small part of a laser pulse at subthreshold power. Under conditions of pumping by a multimode beam, the divergence of a parallel STRS Stokes wave only increases with excess over the threshold for fairly large-scale or, conversely, for essentially small-scale modulation of the laser beam. In the intermediate case, the Stokes wave divergence is similar to that of the pump wave up to a twofold excess over the threshold. It is also shown that as the scale of the transverse modulation of the laser beam decreases, the relative importance of the four-photon interaction decreases. As a result, the relative intensity of the anti-Stokes radiation decreases and that of the Stokes component increases. In conclusion, data are presented on the amplification of an approximately single-mode Stokes wave in the field of a focused multimode pump beam. It is shown that there is an optimal laser beam power at which the coefficient of conversion of the energy into a Stokes wave with divergence close to the diffraction limit has a maximum.
TL;DR: In this article, an experimental investigation of the nonlinear perception of infrared radiation in the 800-1355 nm range with the unaided human eye was carried out, and it was shown that the mechanism for non-linear perception was localized in the retinal nerve layers.
Abstract: Results are presented of an experimental investigation of the nonlinear perception of infrared radiation in the 800–1355 nm range with the unaided human eye. In this range, the infrared radiation is perceived as visible radiation at a wavelength close to but not coinciding with the second harmonic wavelength. The eye sensitivity curve for infrared radiation has an irregular profile with the envelope maximum near the 1113 nm wavelength. It is shown that the mechanism for nonlinear perception of infrared radiation is apparently localized in the retinal nerve layers. A comparison of these results with established data on the vision mechanism of vertebrates suggests the existence of a new phenomenon — two-photon photoisomerization of the visual pigment molecules in the retinal cones, as the basis of the nonlinear perception of infrared radiation.
TL;DR: In this article, the authors investigated the relationship between the coefficients of the electrooptic effects and the tensors of the nonlinear electric susceptibilities and found that the form of the tensor K which describes the fourth-order nonlinear electro optic effect was found for crystals having 42m symmetry.
Abstract: An investigation is made of the relationship between the coefficients of the electrooptic effects and the tensors of the nonlinear electric susceptibilities. The form of the tensor K, which describes the fourth-order nonlinear electrooptic effect, is found for crystals having 42m symmetry. The results are given of polarization-optical measurements of the induced birefringence in single DKP and DKDP crystals for light polarized along the [100] axis and propagating along the [001] optic axis. The coefficients of the second-order electrooptic effect agree with the existing data but the coefficients of the fourth-order electrooptic effect differ from the published results by two orders of magnitude.
TL;DR: In this paper, a theoretical model is developed for the oxidation of metals by cw CO2 laser radiation allowing for interference effects in the oxide film, and an analysis is made of the heating kinetics from room temperature to the melting point of a thermally thin plate and a semi-infinite target.
Abstract: A theoretical model is developed for the oxidation of metals by cw laser radiation allowing for interference effects in the oxide film. The problem is resolved by jointly solving a parabolic equation for the metal oxidation kinetics, a heat conduction equation allowing for convective and radiative losses, and also an equation which relates the absorbtivity of the oxide-metal system to the thickness and optical constants of the oxide film and the cold absorptivity of the metal. An analysis is made of the heating kinetics from room temperature to the melting point of a thermally thin plate and a semi-infinite target. The results of the calculations show good agreement with the experimental data on the oxidation of copper by cw CO2 laser radiation.
TL;DR: In this paper, reversible optical bleaching of the induced absorption was observed and investigated in the range 0.5 − 1.3 μ for γ-irradiated glass fiber waveguides.
Abstract: Reversible optical bleaching of the induced absorption was observed and investigated in the range 0.5–1.3 μ for γ-irradiated glass fiber waveguides. The bleaching was produced by He-Ne laser radiation (γ = 0.63 μ). The effect was associated with an induced absorption band characterized by-a maximum in the range ~0.9 μ.
TL;DR: In this paper, the transfer functions and amplitude fluctuations of a multimode YAG:Nd/sup 3 +// laser with pump modulation and Q switching were analyzed. And the authors showed that this noise level is close to the limit of passive stability of a laser pumped by a krypton arc flashlamp.
Abstract: Calculations were made of the transfer functions and amplitude fluctuations of a multimode YAG:Nd/sup 3 +/ laser with pump modulation and Q switching. By allowing for the influence of energy redistribution between the modes on their spatial competition, it was possible to identify some characteristics of the transfer function and of the spectral distribution of the noise at low frequencies with unequal mode intensities. A YAG:Nd/sup 3 +/ laser with an output power of 2 W in the TEM/sub 00/ mode and a noise level of 0.1% in the frequency range 0.5 Hz--500 kHz was built. It was shown that this noise level is close to the limit of passive stability of a laser pumped by a krypton arc flashlamp.
TL;DR: In this article, a method for measuring the spectral distribution of the absolute quantum yield of O(1S) in the photolysis of oxygen-containing compounds (RO) was proposed.
Abstract: A method is proposed for measuring the spectral distribution of the absolute quantum yield of O(1S) in the photolysis of oxygen-containing compounds (RO). This involves investigating the luminescence excitation spectra of XeO* excimers formed in the O(1S)+Xe+XeXeO*+Xe reaction. The measurements were made in a following RO?Xe mixture of accurately known composition in a system with differential evacuation. The spectral dependences of the quantum yield of O(1S) in the photolysis of N2O (?=170?102 nm) and CO2 (?=128?102 nm) were obtained. The absorption spectra of these compounds and the excitation spectra of RO, corresponding to the transitions to states which dissociated forming O(1S), were determined. The mechanism for excitation and dissociation of CO2 and N2O in these spectral ranges was discussed in the light of the experimental results and the published data. Transfer of the excitation energy from the Xe atoms, formed by absorption of radiation in the spectral range ? < 120 nm, to N2O molecules was observed, resulting in the dissociation of N2O to give and O(1S) or in the formation of N2 and XeO*.
TL;DR: In this paper, the feasibility of achieving a high specific output energy and a high electrical efficiency in an H2?F2 chemical laser excited by a relativistic electron beam was investigated.
Abstract: An investigation was made of the feasibility of achieving a high specific output energy and a high electrical efficiency in an H2?F2 chemical laser excited by a relativistic electron beam. Using an H2:F2:O2:He = 6:15:1.2:50 mixture at a pressure of 1.3 atm, a specific output energy of 100 J/liter was achieved with an efficiency of ~ 900% with respect to the energy deposited in the active volume of the laser and a chemical efficiency of ~ 4%. The degree of initiation and the efficiency were estimated using the experimentally measured electron beam energy absorbed by the active volume of the laser. A high efficiency of utilization of the electron beam energy, ~ 200%, was obtained. It was found that the H(F)+O2+M?H(F)O2+M three-body recombination process was very undesirable in active mixtures at pressures of ~ 1 atm. The rate constants of this reaction for M = He, Xe, and SF6 were determined experimentally.
TL;DR: In this paper, a relationship between the diffraction efficiency of a hologram and the polarization of the object and reference waves is established. And the influence of the objects and reference wave polarizations on the hologram quality is analyzed.
Abstract: An analysis is made of the influence of the object and reference wave polarizations on the hologram quality. It is proposed to use a circularly polarized reference wave to record radiation with various polarizations. A relationship between the diffraction efficiency of a hologram and the polarization of the object and reference waves is established.
TL;DR: In this paper, the intensity of excimer emission bands in Ar-F2, Ar-KrF*, and Kr2F* excimers was investigated as a function of pressure and temperature.
Abstract: An investigation was made of the intensity of excimer emission bands in Ar–F2, Ar–Kr–F2, and Kr–Xe–F2 gas mixtures as a function of pressure and temperature. The observed increase in the spontaneous and stimulated emission intensities at the 248 nm wavelength with rising temperature in an Ar–Kr–F2 mixture is associated with energy redistribution between KrF*, ArKrF*, and Kr2F* excimers.
TL;DR: In this paper, the relaxation time of the level populations of the excited 2P1/2 state of atomic iodine was determined experimentally, subject to pumping by xenon flashlamps with flash durations of several hundred microseconds.
Abstract: Measurements were made of the amplification cross section at the frequency of the F' = 3→F = 4 transition. The luminescence line broadening and shift due to different buffer gases were determined. The magnitude and lifetime of the population inversion were investigated. The relaxation time of the level populations of the excited 2P1/2 state of atomic iodine was determined experimentally. An analysis was made of the amplifier energy characteristics. The conditions were determined for the generation of high-contrast nanosecond optical pulses having energies of approximately 10 J and a directionality close to the diffraction limit, subject to pumping by xenon flashlamps with flash durations of several hundred microseconds.
TL;DR: In this article, a theoretical analysis of the mode structure in unstable resonators with field rotation (URFRs) is presented, and the results of estimating the influence of the optical inhomogeneities of the active medium on the structure of the dominant URFR transverse mode are presented.
Abstract: A theoretical analysis is made of the characteristics of the mode structure in unstable resonators with field rotation (URFR's). The results of estimating the influence of the optical inhomogeneities of the active medium on the structure of the dominant URFR transverse mode are presented. It is concluded that URFR's are potentially useful for lasers with low gains per pass and active media with large transverse cross sections. Designs of URFR's and calculation methods are discussed.
TL;DR: In this article, the time, temperature, and impurity concentration dependences of the formation and relaxation of phase holograms in iron-doped lithium niobate were determined.
Abstract: The time, temperature, and impurity-concentration dependences of the formation and relaxation of phase holograms in iron-doped lithium niobate were determined. A volume phase holographic grating with a period of 0.69μ and a thickness of 14 mm was characterized by an angular selectivity of 22" and a spectral selectivity of 1.36 A.
TL;DR: In this paper, an analysis of the influence of aperture effects, divergence and non-monochromaticity of pump radiation, and self-interaction processes on the degree of compensation of the phase distortions in degenerate four-frequency interaction was made.
Abstract: An analysis is made of the influence of aperture effects, divergence and nonmonochromaticity of the pump radiation, and self-interaction processes on the degree of compensation of the phase distortions in degenerate four-frequency interaction. Experimental attainment of wavefront reconstruction with a conversion efficiency of 10–3 is reported. The resolution of 30 lines/mm achieved is in good agreement with the theoretical estimate.