Spatiotemporal characteristics of laser emission. II

The electrodynamic laser theory of a nonstationary nonlinear oscillatory system with spatially distributed parameters, constructed in the first part, and applied there to semiconductor lasers (electron-beam pumped injection lasers) is used in this second part to investigate the spatiotemporal characteristics of emission in the near and far zones and for giant laser light pulse generation in Q-switched lasers (Chap. 1) and the electrodynamics of a laser with planar open cavities, particularly at high pump levels (Chap. 2). In the third chapter is set forth a procedure for the investigation of the wavefront deformation in laser amplifiers. We consider also the possibility of improving the laser divergence by using mirrors comprising systems of inverting prisms—triple prisms or corner reflector (Chap. 4). The fifth chapter is devoted to a procedure for the investigation of the spatiotemporal characteristics of laser radiation with spherical mirrors. In the sixth chapter the spatial structure of propagating Bessel beams, is determined and a comparison is made with other laser beams.Quantum Radiophysics Division, Lebedev Physics Institute. Translated from Preprint No. 51 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

Contribution to the theory of optical constants in the vacuum ultraviolet and soft x-ray bands

A consistent exposition is presented of the theory of the dynamic response of an atom in the Thomas—Fermi model. The approach proposed is based on a system of Vlasov equations with a self-consistent field. These equations, supplemented by appropriate boundary conditions, describe the dynamic polarizability and photoabsorption of complex many-electron atoms.Theoretical Radiophysics Sector, Lebedev Physics Institute. Translated from Preprint No. 139 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

Lasers operating on cascade transitions of triatomic molecules

The general conditions necessary for the operation of gas lasers based on cascade vibrational-rotational transitions of molecules in the pulse-periodic regime are formulated. The features of such triatomic-molecule lasers with arbitrary excitation are discussed. A computation model is proposed for determining the energy characteristics (maximum attainable efficiency, average and relative lasing power, specific energy output) of free-flow cascade lasers. Systems are analyzed with various excitation methods: gasdynamic (including those with optical feedback), electric-discharge, and chemical (with the DF-CO₂ laser as the example). Practical recommendations with respect to the choice of mixture composition, optimum cavity lengths along the gas stream, and Q-switching frequency are made for the cascade lasers. A molecular gasdynamic laser emitting three wavelengths simultaneously is proposed.Quantum Radiophysics and Optics Division, Lebedev Physics Institute. Translated from Preprint No. 177 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989     

Study of electromagnetic field surface states in photonic crystals using the finite-difference method

Bulletin of the Lebedev Physics Institute - The properties of electromagnetic field surface states in globular photonic crystals are analyzed using numerical solution of Maxwell equations by the...     

Amplification in a semibounded free-electron laser

A self-consistent analytic expression for the complex gain of a free-electron laser is obtained on the basis of the single-particle equations with realistic boundary conditions. The results are presented in the form of amplitude-frequency and phase-frequency characteristics of a free-electron laser.New-Accelerator Problems Laboratory, Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Preprint No. 240 of the Lebedev Physics Institute, Academy of Sciences of the USSR, 1988.     

Anisotropy of Isobaric Instability in a Partially Ionized Plasma in a Magnetic Field

Bulletin of the Lebedev Physics Institute - Linear equations describing the dynamics of small perturbations in partially ionized heat-releasing plasma in an external magnetic field with an...     

Coherent effects in two-level amplifying and SRS-active media

Some results are reported on coherent propagation of optical pulses. In particular, a solution is presented of the Maxwell-Bloch equations for the case of amplification of high-power pulses with varying carrier frequency but with constant number of photons in the pulse.Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow. Translated from Preprint No. 211 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1988.     

Spatiotemporal characteristics of laser emission. III. Propagation of electromagnetic radiation beam in laser installations with allowance for large-angle diffraction and spatial self-focusing

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.Division of Quantum Radiophysics, Lebedev Physics Institute. Translated from Preprint No. 86 of the Lebedev Physics Institute, Moscow, 1990.     

Generalized coherent states of multimode light,and biphotons

Generalized coherent states of a multimode field are analyzed within the framework of the dynamic-symmetry approach and with allowance for polarization. A new class of unpolarized two-photon states is defined. The uncertainty relations and statistical and other properties of optical fields in these states are calculated and analyzed. The relations between the considered states and squeezed states of light are discussed.Optics Laboratory, Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Preprint No. 254 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow. 1988.     

Ultrashort light pulse generation under coherent interaction of a field with a medium

We consider the dynamics of propagation and compression of ultrashort electromagnetic-wave pulses in a multicomponent two-level field, one component of which emits or absorbs light in a regime of coherent interaction of the radiation with the substance. We consider also the question of the dynamics of the field in planar superconducting structures (such as, e.g., layered high-temperature superconductors of the YBa₂Cu₃O_7=x type). With Josephson tunneling of the electrons between the layers it becomes possible here to describe the field-induced current in a model using Bloch equations for particles with near-zero frequency of the transition between levels and with infinite relaxation times, i.e., to reduce the problem to that of the dynamics of a field coherently interacting with a two-level medium.Lebedev Physics Institute, Academy of Sciences of the USSR. University Center for Laser Research, Oklahoma State University. translated from Preprint No. 69, Lebedev Physics Institute, Moscow, 1991.     

Chemical generator of electron-excited nitrogen N2 (A,B). Possibility of developing an exchange N2 (A)-IF visible-band (λ=625 nm) laser

The feasibility is investigated of chemical generation of electron-excited molecular nitrogen N₂(A, B) and of its use as a donor for the development of short-wave chemical lasers. The spectroscopic and kinetic properties of the molecules as potential acceptors of the excited-nitrogen energy are discussed. The feasibility of producing a chemical N₂(A)-IF laser for the visible band ( = 625 nm) is investigated analytically and numerically. The amplification properties of the active medium are analyzed and the energy characteristics of the laser are calculated.Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow. Translated from Preprint No. 136 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1988.     

Phase problem in optics

The problem of reconstructing a coherent monochromatic field from its energy characteristics is considered. A comparative analysis is made of one- and two-dimensional phase problems. It is shown that a substantial role is played in the two-dimensional case by the vortical properties of the optical-energy flux vector. The results of computer and physical experiments are reported.Optics and Spectroscopy Division, Lebedev Physics Institute. Translated from Preprint No. 93 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

Kinetics of transition through lasing threshold

The paper is devoted to an investigation of laser-radiation statistics. The dynamics of establishment of an equilibrium photon distribution in frequency is analyzed and the results are compared with numerical experiments. The spectral density of the radiation-intensity fluctuations is obtained in analytic form in the quasiclassical laser theory. An equation that generalizes the earlier calculations is obtained for the lasing linewidth in the framework of the Scully-Lamb theory.Optics Division, Lebedev Physics Institute. Translated from Preprint No. 79, Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

Analogy between mechanics and optics

Division of Theoretical Physics, Lebedev Physics Institute. Translated from Preprint 114, Lebedev Physics Institute, Moscow, 1990.     

Macroparticle acceleration by a laser-plasma stream

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.Quantum Radiophysics Division, Lebedev Physics Institute. Translated from Preprint No. 209 of the Lebedev Physics Institute, Academy of Sciences USSR, Moscow, 1990.     

Theory of spatiotemporal characteristics of laser emission. IV. Methods of controlling the spatial structures of laser beams in linear and nonlinear media

Part IV of the study continues the treatment of the theory of formation of laser beams with smooth spatial distribution, and of their conservation as they are transported in linear and nonlinear media. An exact solution is obtained for the problem of development of a small perturbation with an arbitrary amplitudephase distribution against the background of a plane wave with cubic nonlinearity. Self-consistent (waveguide) solutions of the nonlinear parabolic equation are obtained. The solutions demonstrate the effectiveness of suppression of small-scale self-focusing of diverging beams. The project of a high-aperture single-lens objective with aberration correction is developed and the relevant calculations are made.Quantum Radiophysics Division, Lebedev Physics Institute. Translated from Preprint No. 94 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1990.     

Waveguide gas lasers with frequency-selective cavities

Frequency-selective cavities of waveguide gas lasers are investigated theoretically and experimentally. The problem of finding the field distribution and the radiation loss in a cavity with a diffraction grating is solved theoretically in general form. Frequency-selective properties are determined experimentally for certain particular configurations of waveguide (single-mode, with flat reflectors near the ends, nonselective) and open cavities. The calculations and experimental results agree. It is shown that the selectivity of a waveguide cavity has a nonmonotonic dependence on the length and diameter of the waveguide channel, so that the selectivity can be made several times better. The influence of the capillary wall material and of the location of the reflectors on the frequency properties of the cavity is analyzed. For the case with EH11 mode filtration, a method of accuracy not worse than 1.5% is developed for the analytic calculation of the losses. A cavity with a reflecting interferometer made up of a diffraction selector and a diffraction grating is proposed. It is shown experimentally and theoretically that its use permits separation of any (including sequential) transition from the emission spectrum of a CO₂ laser and of longitudinal cavity modes.Lebedev Physics Institute, Academy of Sciences of the USSR. Translated from Preprint No. 251 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1988.     

Methods of estimating the angular and energy characteristics of generated laser emission

The physical models used to estimate the angular and energy characteristics of laser emission generated in the kinetic and coherent regime of emission interaction with an active medium are critically analyzed and systematized.Quantum Radiophysics and Optics Division, Lebedev Physics Institute. Translated from Preprint No. 176 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.     

Stability and bistability of stationary states in four-wave interaction in a photorefractive medium

The stability of stationary states is investigated analytically and numerically for various four-wave mixing schemes in a photorefractive medium with nonlocal nonlinear response when recorded with a translucent grating. Bistability is indicated for a number of four-wave-mixing schemes and the conditions for its existence are indicated.Quantum-Radiophysics Division, Plasma-Phenomena-Theory Sector, Lebedev Physics Institute. Translated from Preprint No. 138 of the Lebedev Physics Institute, Academy of Sciences of the USSR, Moscow, 1989.