Table of contents

Sum-frequency waves were generated when a microscopic optically nonlinear waveguide made of lithium niobate was excited with neodymium (λ=1.06 μ) and helium-neon (λ=1.152 μ) lasers. Moreover, the second harmonic of the neodymium laser radiation was generated. A study was made of two waveguides, which were 0.98 and 2.36-μ thick. The wave-delay coefficients and the conversion efficiency were determined.

The efficiency of the coupling of semiconductor laser radiation into a fiber is analyzed as a function of the laser operating conditions. It is shown that the change in the angular distribution of the laser radiation as a result of modulation distorts the shape of the optical pulses coupled into a fiber. The calculated values of the coupling coefficient are compared with the experimental results. A method for determining distortions is described.

An investigation was made of the influence of the gas filling of prototype pulse-discharge lamps on the efficiency of a neodymium-doped yttrium aluminum garnet laser. The lamps were filled with xenon, krypton, and their mixtures and they were operated for a long time. It was found that the best results were obtained using a 50-50% xenon-krypton mixture.

A frequency-selection method was developed for a dye laser. In this method the selection was performed by a nonlinear mirror induced in an absorbing medium inside the resonator by the laser radiation field. The absorbing substance was bromine vapor. The experimental estimate of the likely reflection coefficient of the induced nonlinear mirror was in good agreement with the results of calculations.

The working frequency range and the maximum scanning angle of an acousto-optic deflector depend on the width of the acoustic beam, i.e., on the width of the transducer. The proposed construction of a Bragg-type deflector makes it possible to increase the scanning angle severalfold without altering the transducer geometry or its .construction. A quantitative calculation is made for the proposed deflector. Optimal acousto-optic materials for this deflector are suggested.

A solution is given of the heat conduction equation for a two-coordinate Bragg cell handling large optical powers. The boundary conditions are determined. An analytic relationship is obtained for the dependence of the average temperature of the active element of deflectors of different geometries on the intensity of the controlled laser radiation and on the consumption of the electrical power.

Spark discharges on both sides of the main gap were used for the preionization of the gas in a 0.4-liter pulsed CO₂ laser. The gap was formed by two monolithic metal electrodes. An output energy of 9 J was obtained at a pressure of 600 mm Hg for a CO₂:N₂:He =1:1:2 mixture.

It is shown that the use of a narrow-band noise-like Gaussian pump wave in the Raman amplifier makes it possible to perform efficient mode locking at the frequency of the first Stokes component. This locking is accompanied by a considerable broadening of the spectrum of the amplified signal and the signal exhibits pure amplitude modulation. The degree of mode locking and of the broadening of the spectrum is a function of the shape of the correlation function of the pump envelope.

An argon laser was bulit using a beryllium oxide capillary. The output power of the laser was 500 mW. The laser emitted pulses at a high repetition frequency. The advantages of the laser was freedom from the shot noise in the output radiation, high efficiency, and natural cooling.

Stimulated emission from Nd³⁺ ions in a crystal of CaSc₂O₄ was observed at 77 and 300°K. The emission was in the form of lines due to two transitions ⁴F_3/2–⁴I_11/2 and ⁴F_3/2–⁴I_13/2 with low excitation thresholds. Some spectroscopic parameters of this new laser medium were determined.

Two methods for the dynamic correction of laser wave fronts are considered. The first method is based on a redistribution of the energy between two coherent beams interacting with an induced (by the beams themselves) three-dimensional phase hologram. An efficient redistribution occurs if the phase grating is shifted by one quarter of its period relative to the interference pattern. In the second method a dynamic holographic method is used to form a wave of such a shape that it becomes plane after passing through a laser amplifier. The possibility of experimental realization of the proposed methods is considered.

Various materials suitable for the reversible recording of information are discussed. Attention is concentrated on magnetic media, ferroelectrics combined with photoconducting films, photochromic materials, amorphous semiconductors, and metal-insulator-semiconductor multilayer structures. The suitability of each material is judged by the recording energy resolution, reading efficiency, response, and other parameters.

A theoretical investigation is made of the Stark structure of the stimulated Raman scattering lines of a gas, which appears in the field of high-power pump radiation. The cases of different polarizations of the pump and Stokes waves are considered. Allowance for the nuclear contribution to the Stark shifts is made. It is shown that the Stark effect should be observed at pump radiation intensities which can be achieved using currently available lasers.

A theoretical analysis is made of a laser system based on a regenerative amplifier and capable of generating trains of pulses of variable amplitude. The time dependence of the gain is obtained for the rise of energy required to achieve a very strong compression (implosion) of a target by laser radiation. An analysis is made of a combined method for varying the gain by an electro-optic switch and a saturable filter. Numerical estimates are obtained for regenerative amplifiers with unstable and plane-parallel resonators in which the active element is made of neodymium-doped glass or yttrium aluminum garnet (YAG:Ne). This method may be useful in those cases when a train of pulses with a specified energy variation has to be generated.

A general method is proposed for finding the extremal directions of the electro-optic effect. The optimal directions are calculated for crystals belonging to the classes 2m, 422, 4mm, 4, 6, , 6mm, m2, and 622.

A theoretical analysis is made of the influence of interference on the emission of surface light waves from a corrugated part of a thin-film waveguide. It is shown that the interference effects are strongest when the film is corrugated on the substrate side. A strong dependence of the attenuation coefficient of a wave on the film thickness and its modulation period is confirmed experimentally. Recommendations are made on the efficient coupling of light into the film.

The Boltzman transport equation is solved numerically for the distribution function of the energies of electrons in working mixtures of electron-beam-controlled CO₂ gas-discharge lasers. The solution is obtained allowing for 27 elementary processes involving electron collisions with neutral particles. The calculated distribution functions are used in a study of the energy balance in discharges. The excitation efficiencies of various molecular levels are found as a function of the ratio of the electric field E to the gas pressure p and as a function of the partial concentrations of components of N₂+CO₂+He mixtures. The velocity of the drift of electrons in an electric field is calculated. The rates of ionization of easily ionizable impurities and of the attachment of electrons to these impurities are evaluated. The results are presented in graphical form.

A theoretical analysis is made of the self-diffraction of short light pulses in an induced amplitude-phase grating in a thin layer of resonant medium. Expressions describing the amplitudes (intensities) of the diffracted beams are derived and analyzed. It is shown that the nature of the amplitude modulation of the light diffracted into small angles depends strongly on the amplitudes of the input pulses. It is demonstrated that transient self-diffraction of short pulses can be used in estimating the dipole moment of a saturable transition.

A three-channel neodymium-glass laser system was developed. This system emitted quasicontinuous pulses of

10^–3

sec duration. The output energy of the system was ~10 kJ and the radiation power density on a target zone of over 0.5 cm in size was 10⁶–10⁸ W/cm². A high-power single-channel laser with a high directionality of the radiation was constructed using a telescopic resonator and a resonator with a confocal lens system. The output energy of this laser was ~ 4 kJ and the duration of the output pulses was 0.8×10^–3 sec. The angular divergence of the output radiation was 3×10^–4 rad. When this radiation was focused by a system composed of long-focus and short-focus lenses, the average (during a pulse) radiation power density in the focal plane was ~10¹¹ W/cm².

An investigation was made of the spectrum of the radiation emitted by a ClF₃+D₂ chemical laser. The time characteristics of the vibration-rotational transitions in the DF* and DCl* molecules were used in an analysis of the main elementary processes occuring in the laser. The laser emission from DCl* occurred 20 μsec after the initiation and this indicated that it was due to not only the F+D₂→DF*+D stage but also to secondary elementary stages of a chain process.

A theoretical analysis is made of the spontaneous emission from an excited atom or a molecule in a one-dimensional periodic structure formed by a screened two-conductor line filled with periodically distributed dielectric disks. It is shown that when the transition frequency lies within or close to the forbidden band of the periodic structure, the decay of an excited state of an atom or a molecule produces a characteristic long-lived dynamic state. This dynamic state is a superposition of the excited and ground states with an admixture of a photon "cloud," which surrounds the atom or molecule. A study is made of the distribution of the electromagnetic energy of the dynamic state. The energy and the decay law of the excited state are obtained and the spectrum of the emission which accompanies this decay is obtained. It is shown that the spontaneous emission can be suppressed strongly in volumes much greater than the wavelength. The possibility of the suppression of spontaneous emission from lasers is discussed.

A thin-film optical waveguide with a sinusoidally corrugated surface is considered. This waveguide acts as a phase diffraction grating. The relationships between the waveguide parameters and the parameters of the exciting beam, ensuring the most effective coupling of the radiation into a specified waveguide mode, are determined for an arbitrary ratio of the grating period to the wavelength of light and for a relatively weak depth of modulation of the film thickness (i.e., for relatively weak coupling conditions).

The kinetics of nonresonant vibration-vibrational (v-v) exchange in binary mixtures is considered in the presence of a laser field using the harmonic oscillator model and the approximation of single-quantum transitions. An integral representation is obtained for the distributions over the vibrational levels of each component making allowance for the v-v exchange, vibration-translational (v-T) relaxation, and influence of an infrared radiation source. A closed system of equations for the relaxation of the vibrational energy in the modes is derived ignoring the decay processes. The nonequilibrium distribution functions are obtained for the steady-state and quasisteady-state conditions. It is shown that if v₁>v₂ (v₁ is the frequency of the mode excited by the laser field and v₂ is the frequency of the mode to which the energy is transferred), the vibrational kinetics of a binary mixture may differ considerably from the kinetics of a single-component medium provided that the strong laser, field acts on the first component and the rate of exchange of the quanta between the modes under consideration is sufficiently rapid. This circumstance makes it possible to utilize a directional v-v exchange for the purpose of efficient "heating" of a mode with a lower vibrational energy. The conditions under which this occurs are determined.

A theoretical analysis is made of the influence of the temperature gradients on the operation of Bragg-type modulators and deflectors for the control of high-power light fluxes. Isotherms are obtained for various sections through the active element by solving the heat conduction equation. The directions of the maximum temperature gradients in the active element are found for devices of this type. Some recommendations are made on future experimental investigations.

An investigation was made of an acousto-optic light deflector in the form of a water container and a lithium niobate piezoelectric transducer. This deflector had 50 resolvable positions for a laser beam of λ=0.63μ wavelength and the switching time was ~6 μsec. The intensity of the light deflected into a side maximum was 20% of the total intensity and the power consumption in the transducer was ~1.7 W.

A theoretical analysis is made of the amplification in a γ-ray laser excited with a radiofrequency signal. It is shown that an additional splitting of a line does not reduce the gain.

The problem of reflection of an electron from an impermeable wall in the presence of a strong monochromatic electromagnetic wave is formulated and solved numerically. It is shown that the probability of the excitation of a state corresponding to the absorption of n photons has threshold features and that radiation is absorbed on reflection of an electron from a wall.

An analysis is made of the transport of energy by charged particles in a high-temperature laser plasma, with particular attention to α particles produced by the deuterium-tritium reaction. The distribution function of the α particles is obtained by solving the transport equation for a spatially inhomogeneous plasma. An approximate method is developed for the calculation of the distribution function and other quantities of physical interest. A satisfactory agreement is obtained between the exact and approximate solutions.

Equations are derived for determining the optimal orientation and calculating the efficiency of an electro-optic crystal deflector with a controlled angle of internal reflection. The equations apply to crystals of any suitable class.

An optimization procedure is applied to the gain of a carbon dioxide gas-dynamic laser with a planar wedge-shaped nozzle. A one-dimensional steady-state flow of the gas without a change in its chemical composition is assumed. The rate equations are formulated and an analysis of the range of variation of the parameters being optimized is given. The optimization is performed by varying the initial temperature, pressure, composition of the mixture (carbon dioxide, nitrogen, helium, and water vapor), and nozzle geometry. The relief of the surface representing the solution in a multidimensional space of the optimized parameters is determined and the nature of variaiton of these parameters near the optimal points is analyzed.