Showing papers in "Journal of Russian Laser Research in 1991"
49 citations
TL;DR: In this article, a general approach is formulated for analyzing algebraic models of quantum composite systems with an internal symmetry described by group G. The case G = SU(2) is examined in detail as applied to the analysis of polarization invariance in quantum optics.
Abstract: A general approach is formulated for analyzing algebraic models of quantum composite systems with an internal symmetry described by group G. The case G = SU(2) is examined in detail as applied to the analysis of polarization invariance in quantum optics. A new class of fully depolarizable quantum states of light (scalar biphotons) is defined and investigated. Certain interactions of scalar biphoton light with material media are considered in the context of Dicke and Jaynes-Cummings models.
17 citations
TL;DR: In this article, the authors considered a cavity filled with a uniform medium having a time-varying dielectric constant and in a cavity with a moving wall, and the possible limits of the squeezing and correlation coefficients were indicated.
Abstract: Quantization of an electromagnetic field in a cavity filled with a uniform medium having a time-varying dielectric constant and in a cavity with a moving wall is considered. It is shown that squeezed and correlated states of the field can be generated. The possible limits of the squeezing and correlation coefficients are indicated. Two methods of parametric buildup of field modes, by variation of the dielectric constant and by vibrating the cavity wall at double the frequency, are compared.
13 citations
TL;DR: A review of recent results obtained with application of the Hermitian phase formalism of Pegg and Barnett is given in this paper, where various states of the field obtained in nonlinear optical processes are discussed from the point of view of their phase properties.
Abstract: A review of recent results obtained with application of the Hermitian phase formalism of Pegg and Barnett is given. Various states of the field obtained in nonlinear optical processes are discussed from the point of view of their phase properties.
7 citations
TL;DR: In this article, it was shown that the stable evolution equations for the squeezed and correlated states (SS and CorS) in the form of Hw × SU (l.l)-coherent states with maximal symmetry are classical Hamiltonian equations with a Kaehler symplectic 2-form of Onofri type.
Abstract: It is shown that the stable evolution equations for the squeezed and correlated states (SS and CorS) in the form of Hw × SU (l.l)-coherent states with maximal symmetry are classical Hamiltonian equations with a Kaehler symplectic 2-form of Onofri type. The evolution of the second momenta of the Hermitian quadratures of the boson operator is described by canonical equations. The general form of the Hamiltonian which correlates without squeezing is found and the connection of the stable evolution of SS and CorS with the existence of linear integrals of motion is pointed out.
7 citations
7 citations
TL;DR: In this paper, a new classification of polarization states of quantum light fields is given using the concept of the polarization (P) spin due to the polarization gauge SUp(2) invariance of free light fields.
Abstract: A new classification of polarization states of quantum light fields is given using the concept of the polarization (P) spin due to the polarization gauge SUp(2) invariance of free light fields [I] Generalized coherent states (GCS) asNociated with P-scalar biphotons are discussed We also point out some applications of the results in the optical communication theory
4 citations
4 citations
TL;DR: A large optical nonlinearity of thermal origin has been observed in acetone solutions of a series of tetraphenylporphin, TPPH2, MnTPP(CH3CO2−), FeTTPCI-, CoTPP, NiTPP, and CuTPP as discussed by the authors.
Abstract: A large optical nonlinearity of thermal origin has been observed in acetone solutions of a series of tetraphenylporphin, TPPH2, MnTPP(CH3CO2−), FeTTPCI-, CoTPP, NiTPP, and CuTPP. The nonlinear Kerr coefficient is sensitively dependent on the nature of central metals in the compounds. The Mn compound exhibits the largest coefficient, ≅6 × 10−5 esu, for 514 nm laser wavelength. The use of prophins offers increased flexibility in the preparation of different Kerr media.
3 citations
3 citations
TL;DR: In this article, the authors present a review of the most general and rigorous mathematical models for the calculation of the magnetic field in a cavity and, for an active medium, the Navier-Stokes system of equations with allowance for physicochemical kinetics.
Abstract: Solution of the general problem of producing high-efficiency laser systems calls for research into the choice of the optimal cavity design, aimed also at studying the influence of the spatial inhomogeneity of the active medium on the character of the laser emission [9-18]. Understandably, in the general case it is more effective to carry out the investigation by numerical means. This reduces in essence to the self-consistent problem of the mutual influence of the field in the cavity and the physicochemical processes that form the active medium. In the case of a cw chemical HF laser, the pertinent calculations are made complicated by the multilevel character of the excitation of the working molecules, and also of the substantial role of the effects of mixing of a large number of chemically active jets. Undoubtedly the most general and rigorous mathematical model for the calculation of the magnetic field in a cavity should be taken to be the system of Maxwell equations and, for an active medium, the Navier-Stokes system of equations with allowance for physicochemical kinetics. This method, however, is too complicated and laborious in practice. We must therefore choose simplified approaches by starting from the specific features of the problem. The scientific literature has described by now a wide spectrum of computation methods that have become classical and are contained in textbooks and monographs [i, 2, 19-27]. The choice of the method must therefore be justified on the basis of the aims pursued and the problems to be solved. An advantage of analytic methods [i, 2, 28-43] is that they make it possible to obtain the solution in the most general form and to understand its physical meaning. Final analytic solutions, however, are frequently attainable only in some particular or limiting cases. Therefore, if specific numerical results are needed, computer methods turn out to be more useful. The known published numerous geometric-optics [i, 2, 20, 25, 44-56], ray-matrix [i, 23, 57-64], opticogeometric [65-70], etc., methods, including the eikonal method [21, 24, 71-72], while relatively simple and sufficiently effective for the solution of a definite group of problems, can nevertheless not represent in the general case completely the phase structure of the radiation field in a cavity with a free-flowing optically inhomogeneous medium. Principal attention is therefore paid in this review to the description and mutual comparison of various methods of wave optics [73-163] and also to methods of calculating active-medium characteristics [164-198], aimed at choosing a working method of solving complex comprehensive problems of the ratio of the parameters of a cw HF chemical laser with an unstable telescopic cavity, so as to improve the directivity pattern of its radiation.
TL;DR: In this article, the dynamics of laser-supported detonation waves (LSDW) in focused laser beams were investigated using a self-consistent numerical model that takes account of the gas-dynamic motion of the plasma and the refraction and absorption of the radiation in the plasma, with allowance for its real equation of state.
Abstract: Results are reported of a computational—theoretical analysis of the dynamics (propagation and decay) of laser-supported detonation waves (LSDW) in focused laser beams. The investigations were carried out using a self-consistent numerical model that takes account of the gasdynamic motion of the plasma and the refraction and absorption of the radiation in the plasma, with allowance for its real equation of state. An analysis is presented of the influence of the radial structure of the radiation on the propagation and decay of the LSDW, and of the conditions of the radiation transformation. Results on the dynamics of two-dimensional LSDW in the beam of an excimer laser are presented.
TL;DR: In this article, a regular procedure for finding the solutions of the Schrodinger and Bloch matrix equations is developed, based on their dynamic symmetries and on the calculations of the respective group parameters that determine the dynamics of the atoms in modulated laser fields.
Abstract: Solutions of the Schrodinger equations are obtained, in terms of Bessel, Legendre, and hypergeometric functions, for the transition amplitudes of two-, three-, four- and N-level atoms in amplitude- and frequency-modulated laser fields. Exact solutions for the atom evolution parameters are obtained in those cases when the Hamiltonian of the interaction of the quantum system with the classical fields has exact symmetries such as dynamic so2 and so3,1 Lie algebras and isomorphic ones. In the case of broken symmetry the solutions take the form of series in terms of a small dimensionless quantity and can be obtained in principle in arbitrary order of smallness in the variable. A regular procedure for finding the solutions of the Schrodinger and Bloch matrix equations is developed, based on their dynamic symmetries and on the calculations of the respective group parameters that determine the dynamics of the atoms in modulated laser fields.
TL;DR: In this paper, the results of application to different laser installations of soft or apodized apertures (AA) with smooth transmission profiles decreasing from center to edges were presented.
Abstract: This paper presents the results of application to different laser installations of soft or apodized apertures (AA) [1–3] with smooth transmission profiles decreasing from center to edges. Two types of AA, which were made of CaF2:Pr crystals, have been used: induced absorption (IA) AA and photooxidation (PhO) AA. The ∼3–45-mm-diameter IA and PhO AA with smooth monotonic flat-top profiles have been used in 1.06-μm laser amplifier systems to suppress hard-edge Fresnel diffraction rings in beam cross section and to increase the second harmonic conversion efficiency. The ∼3–4-mm-diameter PhO AA with bell-like transmission profiles were placed inside the 2.94-μm and 1.06-μm resonators of master oscillators. The tendency of the output energy to increase by 1.3–1.8 times and the decrease in beam divergence in single-mode lasing as compared with a hard-edge aperture have been observed in the experiments described below.
TL;DR: In this paper, the influence of laser treatment on the formation of residual stresses relative to the changing structure-phase composition in the surface layers of high-chromium cast iron with 16% chromium was investigated.
Abstract: We investigate the influence of laser treatment on the formation of residual stresses relative to the changing structure-phase composition in the surface layers of high-chromium cast iron with 16% chromium. We show that appreciable tensile stresses are produced in the region of the laser action and that their distribution depends on whether the laser treatment was or was not accompanied by surface melting. The produced residual stresses are responsible for the formation of a large number of cracks. Preheating to 400°C lowers the level of the tensile residual stresses and prevents crack formation. A pellet stream acting on the surface produces cold-work hardening layers in which the tensile stresses change into compressive ones. The depth, hardness, and magnitude of the compressive residual stresses depend on the method used to work harden the cast iron and on the angle of attack of the pellet as it acts on the surface.
TL;DR: In this article, the conditions for gas breakdown above an Ni−Zn (M4OONN) ferrite surface were investigated under the assumption that the discharge is initiated by a thermal explosion of a surface layer of the ferrite modified by current flowing through it.
Abstract: The conditions are investigated for gas breakdown above an Ni−Zn (M4OONN) ferrite surface. The assumption that the discharge is initiated by a thermal explosion of a surface layer of the ferrite modified by current flowing through it is verified experimentally and theoretically. The electric and thermophysical properties of the (ferrite+annealed layer) system are determined. The experimentally observed temporal characteristics of the prebreakdown phase of the discharge and the dependences of the breakdown voltage on the discharge-circuit parameters are described within the framework of a single model.
TL;DR: In this article, a modification that simplifies the measurement procedure is presented for a microscopic method of measuring the astigmatic distance of laser diodes, and results are presented of measurements of the ASTD of the commercial laser Diodes of type ILPN-102, ILPNs-205, and ILPNS-210, as well as of laboratory specimens with ridge waveguides.
Abstract: A modification that simplifies the measurement procedure is presented for a microscopic method of measuring the astigmatic distance of laser diodes. The errors of the proposed method are estimated and results are presented of measurements of the astigmatic distance of the commercial laser diodes of type ILPN-102, ILPN-205, and ILPN-210, as well as of laboratory specimens with ridge waveguides.
TL;DR: In this paper, the influence of short-lived color centers on the lasing properties of a high-power neodymium silicate glass spoke-waveguide laser was investigated.
Abstract: Results are presented of an investigation of the lasing characteristics of a high-power neodymium silicate glass spoke-waveguide laser. The influence of short-lived color centers on the lasing properties is investigated. It is shown that short-lived color centers lead to generation of regular giant pulses with repetition frequency up to 30 kHz, to a substantial lengthening of the decay time of the neodymium-ion metastable level (via a decrease of the superluminescence background) and by the same token to an increase of the lasing efficiency. A high-power technological waveguide laser with spokelike active elements, emitting a train of regular giant pulses with total emission energy up to 20 J and high homogeneity of the emission-field distribution is developed on the basis of the reported investigations.
TL;DR: In this paper, a method for reconstructing an optical field is developed based on special shaping of the structure of the information on the amplitude and phase pattern of the recording field, and the phase information is recorded after visualization on a phase sensitive material.
Abstract: A method for reconstructing an optical field is developed. It is based on special shaping of the structure of the information on the amplitude and phase pattern of the recording field. The amplitude information is recorded by a standard method, such as photography. The phase information is recorded after visualization on a phase-sensitive material. The field structure is reconstructed by passing a quasimonochromatic space-coherent plane wave through the obtained transparencies. The method was implemented experimentally for phase-modulated fields with the phase information visualized by the Zernike method.
TL;DR: In this paper, a two-photon state was generated by optical parametric down conversion, where pairs of light quanta with degenerate frequency but divergent directions of propagation were sent to two independent Michelson interferometers.
Abstract: After a very brief review of the historical EPR experiments, this paper reports a new two-photon interference type EPR experiment. A two-photon state was generated by optical parametric down conversion. Pairs of light quanta with degenerate frequency but divergent directions of propagation were sent to two independent Michelson interferometers. First- and second-order interference effects were studied. Different from other reports, we observed that the second-order interference visibility vanished when the optical path difference of the interferometers were much less than the coherence length of the pumping laser beam. However, we also observed that the second-order interference behaved differently depending on whether the interferometers were set at equal or different optical path differences.
TL;DR: In this article, the influence of laser radiation on the formation of an austenitic grain and on the alloying ability of a solid solution of high-speed cutting steels is investigated using as an example the steel R18 subjected beforehand to various bulk heat treatments.
Abstract: The influence of laser radiation on the formation of an austenitic grain and on the alloying ability of a solid solution of high-speed cutting steels is investigated using as an example the steel R18 subjected beforehand to various bulk heat treatments. Notice is taken of the role of laser tempering during the initial stage of heating to the temperature at which an austenitic transformation with release of secondary carbides takes place, accompanied by laser action of plastic de formation with formation of a corresponding structurally stressed state. The content, in the solid solution, of the main alloying element tungsten in the R18 high-speed steel is determined from Mossbauer measurements and from x-ray phase analysis data on the degree of the dissolution of the carbide phase in laser-action zone. Determination of the carbon content in the solid solution of the zones of laser action, yields data on the degree of the carbide-phase solution and on the displacement of the diffraction α-lines; these data can be attributed to anomalous diffusion of the carbon as the laser heating is accelerated.
TL;DR: In this paper, the friction wear of surfaces of 40Cr structural steel and 12Cr18Ni10Ti (12Kh18N10T) stainless steel was investigated and the dependence of the rate of wear on the surface microhardness was obtained.
Abstract: The friction wear of surfaces of 40Cr (40Khr) structural steel and 12Cr18Ni10Ti (12Kh18N10T) stainless steel is investigated. It is established, by comparison of the wear of initially annealed 40Cr steel after hardening by radiation from a CO2 laser to various degrees of surface microhardness and separately after volume heat treatment, that the wear is due to fatigue in the entire range of microhardness, regardless of the dispersive properties of the structures. It is shown that the resistance to wear tends to increase with increase of the microhardness of the bearing surfaces. The dependence of the rate of wear on the surface microhardness is obtained. It is found that the wear process is accompanied by formation of a special structurally stressed state in the Saint-Venant region; this state is characterized by a constant hardness level independently of the preceding state of the material.
TL;DR: In this paper, a physical model for macroparticle acceleration in an expanding laser plasma was proposed, based on the absolutely inelastic interaction of the laser-plasma ions with the macroparticles surface.
Abstract: A physical model is proposed for macroparticle acceleration in an expanding laser plasma. Two acceleration mechanisms are considered, based on absolutely inelastic interaction of the laser-plasma ions with the macroparticle surface: acceleration due to the ion momentum and reactive acceleration due to evaporation of the surface layer. The processes are mathematically described with the aid of the gasdynamics equations with thermal conductivity. Approximate analytic expressions are obtained and permit an estimate of the laser-plasma energy as well as of the quasiparticle momentum as functions of the parameters of the laser pulse, of the target, and of the macroparticle. The analytic solutions are compared with numerical computations using the RAPID program; the comparison confirms that the results agree qualitatively and quantitatively.
TL;DR: In this article, the electrodynamic theory developed for the laser as a nonstationary nonlinear oscillating system with spatially distributed parameters was applied to specific laser types, and the subject of part 3 is designated in the title.
Abstract: In parts 1 and 2, the electrodynamic theory developed for the laser as a nonstationary nonlinear oscillating system with spatially distributed parameters was applied to specific laser types. The subject of part 3 is designated in the title.
TL;DR: In this paper, the dependence of the generation efficiency of a pulsed electroionization CO laser on the excitation duration is investigated experimentally, and a criterion is established for the choice of excitation-pulse duration.
Abstract: The dependence of the generation efficiency of a pulsed electroionization CO laser on the excitation duration is investigated experimentally. A criterion is established for the choice of the excitation-pulse duration. Satisfaction of this criterion ensures operation of an electroionization CO laser in the freerunning regime, with an efficiency that is maximal under the given experimental conditions.
TL;DR: In this paper, the basic act of lattice-restructuring in first-order phase transitions constitutes a transition of a cluster of ions from one phase into another, based on a microscopic analysis, a procedure is proposed for determining the cluster parameters from the properties of the material and from the thermodynamic parameters of the phase transformation.
Abstract: The premise is developed that the elementary act of lattice-restructuring in first-order phase transitions constitutes a transition of a cluster of ions from one phase into another. Based on a microscopic analysis, a procedure is proposed for determining the cluster parameters from the properties of the material and from the thermodynamic parameters of the phase transformation. The concept of lattice-restructuring rate is introduced. Starting from the cluster model of the lattice-restructuring, expressions are obtained for the activation energy of the growth of the new phase. The results are used to calculate numerically α-γ transformations in rapidly heated iron. The results are in satisfactory agreement with experiment.
TL;DR: In this article, a new algorithm based on the use of the stationary phase method was proposed to calculate (in the diffraction approximation) fields in optical cavities with shaded axial zone and large mirror aperture, in a cylindrical coordinate frame.
Abstract: It is proposed to calculate (in the diffraction approximation) fields in optical cavities with shaded axial zone and large mirror aperture, in a cylindrical coordinate frame, using a new algorithm based on the use of the stationaryphase method. Unlike the already known ones, the method has high efficiency in the region of large Fresnel numbers, and is close in speed to the method of fast Fourier transformation. The procedure is described and specific calculation results that illustrate the proposed method are presented.