Table of contents

The results are given of theoretical and experimental investigations of "soft" apertures whose action is based on the dependence of the transmission of light by a three-layer medium on the thickness of the layer separating the surfaces on which light is incident at an angle exceeding the angle of total internal reflection. It is shown that such apertures can be used to form a beam with a specified radial intensity profile from beams with Gaussian and uniform profiles. The high optical strength of such apertures and the possibility of formation of a radial profile with a high spatial fill factor without formation of diffraction rings makes them suitable for use in high-power laser systems.

An investigation was made of the energy and time charactenstics of a jet dye laser pumped by a copper vapor laser. The average output power of tunable dye laser radiation was 0.2 W, the peak power was 1.8 kW, and the efficiency was ~12%.

The exact solution is obtained for the dynamics of a two-level system with unequal relaxation times subjected to the field of a pulse of arbitrary duration and amplitude. The shape of the pulse for which this exact solution can be obtained is found by the inverse problem method.

A method is proposed for the determination of the density, electron temperature, and ion temperature of a deuterium plasma in laser targets from neutron measurements in the case when the T(d, n)He⁴ reaction involves mainly fast tritons formed in the reaction D(d, p)T.

An investigation was made of the time characteristics of the longitudinal scattering of light in leadlanthanum zirconite-titanate ceramic of the 8/65/35 composition. The minimum duration of a single electrical pulse which switched a sample to a state with maximum contrast depended on the field intensity during the pulse and temperature. Dependences of this kind were determined. In particular, switching to a state with a maximum contrast of 20 at room temperature required a pulse of 500 μsec duration and 12.5 kV/cm intensity. The response time could be reduced by lowering the contrast. In the temperature range 20–76°C the investigated ceramic operated in the memory mode but above 76°C it operated in the nonmemory mode. The influence of the dimensions of the electrodes and sample on the time characteristics was investigated.

The results are given of experiments involving the use of a semiconductor converter in the pump system of a YAG:Nd³⁺ laser. This converter absorbs the radiation of a flashlamp distributed over a wide spectral range (0.44–0.08 μ) and transforms it with an efficiency up to 50% into a narrow spectral band in the region of 0.805 μ, which coincides with one of the absorption bands of YAG:Nd³⁺. It is shown that the use of such a converter reduces the laser threshold by a factor of 1.6–1.7 and increases the differential efficiency of the system by a factor of 2.4.

The results are reported of an experimental investigation of the fine structure of the ν₃ vibrational band of gaseous BCl₃.

The nonlinear fluctuation-dissipation theorem is used in an analysis of spontaneous Raman scattering of light by surface polaritons. The signal representing the light scattered at the exit from a nonlinear medium is several orders of magnitude stronger than the signal scattered at the entry into the medium. In each of these cases the ratio of the reflected to the transmitted signal is of the order of unity if the refractive indices of the media in contact differ considerably at the signal frequency.

A report is given of some characteristics of two types of long-service-life metal-oxide-metal (MOM) diodes suitable for conversion of microwave and infrared radiation to the visible range. It is suggested that it should be possible to mass-manufacture such MOM detectors

An experimental study was made of the possibility of efficient pumping of a cw dye laser with a freely flowing jet by the radiation emitted from a high-current argon laser with a large-diameter active region. The output power of the Ar⁺ laser was ~30 W in axial modes when a three-mirror V-shaped resonator was used and the output power of the dye laser was ~6 W. The dependence of the dye laser power was determined as a function of the pump intensity up to 27 W.

A brief review is given of papers on quantum electronics presented at the All-Union Conference on Modern Applied Optics and Optical Instruments, which was held on June 10–13, 1975 in Leningrad.

A review is given of the lunar laser-ranging investigations published in 1962–1975. The following principal subjects are considered: theoretical analysis of problems in geodesy, geophysics, and astrometry, which can be solved by lunar laser ranging; design, manufacturing, and delivery to the moon of corner-cube retroreflectors; laser ranging apparatus; laser measurements of the distance to the moon (the first scientific and practical results). It is shown that lunar laser ranging provides a promising method for studies of the earth-moon system. The main future developments in the technology of laser measurements of the distance to the moon are discussed briefly, particularly the possibility of increasing the energy efficiency and precision of laser ranging systems. It is concluded that in international organization for lunar laser ranging should be established.

The relationship between the laser action in organic dye solutions with an output energy of ~ 10² J and the pump source characteristics is discussed. It is shown that the specified conditions are satisfied best by a cavity electric-discharge pump source operating under a near-critical damped oscillatory regime. The most effective method for attaining this regime is a reduction in the active resistance of an electric-discharge plasma by lowering the gas pressure in the discharge cavity, which also ensures an increase in the mechanical strength of the source. A comparison is made of the calculated and experimental energy parameters of a laser utilizing a solution of rhodamine 6G in ethyl alcohol with an output energy of 130 J.

A Jamin-type interferometer was used in absolute calibration of a method for the determination of optical path fluctuations from measured temperature-induced fluctuations of the resistance of a thin tungsten wire. The calibration of the method corresponded to variations in the refractive index with temperature in accordance with the law Δ n = –10^–6Δ T(°C), representing dry air at constant pressure. Measurements were made of atmospheric fluctuations of the refractive index under laboratory conditions.

An analysis is made of the self-consistent problem of a steady-state thermal self-interaction of a two-dimensional laser beam traveling in an evaporating (under the action of tie beam) liquid-drop medium in the presence of a homogeneous wind field. A nonlinear geometric-optics equation is obtained for the paths of rays in a beam with an arbitrary initial intensity distribution and an arbitrary initial divergence. The method of successive approximations is used to find the angles of nonlinear refraction of ray trajectories and of the radiation intensity profile in the medium. It is shown that a redistribution of the intensity in the light beam due to ray refraction results in considerable changes compared with a case when the refraction is ignored.

A calculation was made of the intrinsic noise of metal-oxide-metal structures. This noise consisted of the shot noise resulting from the passage of tunnel currents across the barrier, and of the thermal noise due to the contact resistance. The noise of a point-contact detector (contact area ~1 μ²) was investigated. Measurements at 10 MHz gave the spectral density of the noise which was of the order of 10^–19 W/Hz. Allowance for mismatch of the detector contact relative to the incident radiation was made in a calculation of the responsivity, which was found to be 0.1 V/W. The ultimate sensitivity was of the order of 10^–6 W/Hz^1/2. The application of a bias voltage to the contact increased the ultimate sensitivity to 10^–7 W/Hz^1/2.

An investigation was made of the stimulated emission mechanism and energy characteristics of an He-Mn mixture. Inelastic collisions of manganese and helium atoms were found to have a considerable influence on stimulated emission. Mixing of the upper and lower laser levels resulted in the transfer of excitation from these to the neighboring levels, which maintained the stimulated emission in the collisional regime and gave rise to a strong competition between the stimulated emission lines. This made it possible to concentrate the major part of the output radiation energy (over 70%) in the 534.1 nm line. The total output power was 3.5 W when the repetition frequency was optimal (5 kHz); the efficiency of laser action was 0.17% in a selfheated tube whose diameter was 2 cm and volume was 145 cm³.

An analysis is made of the dynamics of formation of thermal lens in the exit window of a large-diameter (≤ 1 m) laser due to the passage of a high-power laser pulse of λ = 1 nsec to 10 μsec duration. Expressions are obtained for the optical power of a thermal lens and for the radiation intensity corresponding to the appearance of critical optical distortions in the lens. Numerical estimates, obtained for various exit-window materials in the wavelength range λ = 1.06–10.6 μ, show that optical distortions should be slight for pulses of about 1 nsec duration. When τ is increased, these distortions increase strongly. Catastrophic optical distortions in the exit window may be expected when the threshold of avalanche electron multiplication is exceeded.

An investigation was made of the temporal structure of pulses emitted from an electron-beam-controlled high-pressure CO₂ laser. These pulses were converted nonlinearly to the visible range in a proustite crystal. The temporal resolution of the method was 3 nsec and it was limited by the band width of the recording system. It was demonstrated experimentally that mode locking occurred when the gas pressure was 3 atm. The advantages and shortcomings of the investigation method were analyzed.

It is shown that the interaction of three standing-wave light beams with a low-pressure gas gives rise to a narrow absorption power resonance. The width of this resonance is related to the transit time of gas atoms between the beams. The weak-field case is analyzed. A formula for a Held of arbitrary intensity is obtained for the situation when the dimensions of the beams are much smaller than the distances between them. Numerical calculations are reported of the resonance amplitude and profile. Optimal (in respect of the field intensity) conditions for the observation of the effect are determined. If the distances between the beams are sufficiently large, it should be possible to observe resonances of width equal to the homogeneous width of atomic radiation lines in spite of the considerable field and transit broadening. The possibility of using this power resonance in stabilization of the emission frequency of gas lasers is considered.

An analysis is made of the kinetic model of an iodine photodissociation laser operating in the regime of accumulation of excited iodine atoms. It is shown that in the majority of cases of practical importance the population inversion is limited by the quenching caused by radicals. The degree of decomposition of the starting material is low and the thickness of the excited layer corresponds to one or two optical thicknesses. The inversion lifetime is governed by the accumulation of molecular iodine. Analytic expressions are obtained for concentrations of various components of the medium.

An analysis is made of the kinetic model of the iodine photodissociation laser operating under freeoscillation conditions. It is shown that the laser parameters are strongly influenced by the reactions of radicals with iodine atoms which depopulate the lower laser level and regenerate the original working substance. Analytic formulas are obtained for the time dependences of the output power and concentrations of various components of the working medium. The potentialities of the iodine laser are considered allowing for pyrolysis.

An analysis is made of the threshold conditions for the generation of stray oscillation modes in disk laser amplifiers and of amplified spontaneous radiation when the threshold is not reached. A comparison is made of the various methods for reducing the reflectivity of the disk surface. A calculation is made of the increase in the rate of decay of the population inversion in the prescence of amplified spontaneous radiation, which has a considerable influence on the energy characteristics of large-aperture disk amplifiers. The nature of the angular distribution of the amplified spontaneous radiation emerging for a disk amplifier is determined.

An analysis is made of the propagation of a frequency-modulated light pulse in a linearly amplifying medium with an inhomogeneously broadened gain profile. It is shown that a pulse can be compressed considerably during amplification. Conditions are established under which strong distortions of the pulse shape may result in its splitting. An analysis is made of the influence of the phase self-modulation of radiation on the shape of ultrashort light pulses in oscillators and amplifiers.

The results are reported of experimental investigations of the use of bismuth germanate single crystals in spatial and temporal modulation of light. Such modulation was employed in the visualization of an ultraviolet image.

An analysis is made of technical fluctuations of the emission frequency of a gas laser with an automatic frequency control (AFC) system. The minimum instability of the emission frequency in a time τ is found as a function of τ and of the spectral densities of fluctuations of the reference frequency and of the optical length of the resonator, photodetector and amplifier noise, and parameters of the forced frequency modulation of the output radiation. The transfer function is found for an optimal linear AFC system ensuring minimum instability. The experimental results are given of a determination of the spectral densities of perturbations and of the relative frequency instability. Practical recommendations are given on the design of optical resonators and AFC systems.

A description is given of a method for growing chromium-activated yttrium aluminum garnet crystals. The results are reported of an investigation of the influence of chromium concentration from 0.01 to 1.0 wt.% on the absorption and luminescence spectra of garnet crystals. Broadening and short-wavelength shift of the R lines are attributed to the expansion of the garnet lattice with increasing chromium concentration. The intensities of the wide Y and U bands and of R lines are linear functions of the chromium concentration. An optical method is suggested for the determination of the chromium concentration in Y₃Al₅O₁₂:Cr³⁺ crystals.

An investigation was made of the spectra and intensities of stimulated emission from naphthalene single crystals doped with ββ'-dinaphthylethylene and excited with giant ultraviolet pulses of various energies in the absorption band of the impurity. An increase in the impurity concentration gave rise to the appearance, in the stimulated emission spectrum, not only of a zero-phonon line but also of a band corresponding to the phonon wing frequencies. The intensity of the zero-phonon line reached saturation when the pump energy was increased but the intensity of the phonon wing grew proportionally to the pump energy. A study was made of the influence of temperature on the behavior of the stimulated emission lines. The results obtained were explained on the hypothesis of the phonon participation in the stimulated emission process.

Relationships are obtained for calculating the spatial distribution of the single-trip gain in a twocomponent molecular laser and amplifier pumped optically in the fundamental band. The threshold characteristics of the laser system are investigated for various pressures and compositions of the gas mixture and for various resonator lengths.

An investigation was made of some characteristics of simultaneous stimulated emission of two or three bands from a dye solution in a resonator with two tunable selective channels and one nonselective channel pumped by giant pulses from a solid laser. Three dyes of the rhodamine series and 3,6-tetramethyldiamino-N-methylphthalimide were investigated. Information was obtained on the competition between the band intensities, pulse durations, and changes in the band profiles as a function of their position relative to the gain curve and of the Q factors of the relevant resonator channels. A possible application of the method to studies of molecular relaxation was considered.

The method of delaying stimulated emission relative to the beginning of an initiating light pulse was used in the determination of the relaxation constants of vibrationally excited molecules interacting with chlorine fluorides. The following effective constants were obtained: , ; , ; , . The values obtained for the and molecules were of the same order of magnitude as the values found by thie luminescence decay method.