Table of contents

A seed of ∼5×5×5 mm dimensions was used to grow ADP crystals of ∼10×10×10 cm size by crystallization from a solution at a rate 10–20 times higher than usual. The anomalous biaxiality of the crystals did not exceed ∼20', which was of the same order of magnitude as the value reported for good-quality crystals prepared by slow growth. A growth rate of ∼1 cm/day should make it possible to prepare nonlinear crystals with large cross sections of the kind needed in laser thermonuclear fusion research.

An image converter with a silver–oxygen–cesium photocathode (the red edge of the photoelectric effect was ∼1.3 μ) was used to determine the time characteristics of single picosecond pulses emitted by an erbium laser at the fundamental frequency (2.94 μ) and at the second harmonic (1.47 μ). The duration of the photoresponse in the case of the fundamental-frequency pulses was 45 psec and the threshold sensitivity of the system was 10⁸ W/cm². It was found that the photoresponse of the image converter was strongly nonlinear.

A review is given of the radiation-optical properties of glass fiber-optic waveguides. Particular attention is paid to an analysis of radiation-induced absorption in multimode fiber-optic waveguides having pure and doped quartz glass cores. Dependences of the induced absorption on the dose, power, and type of radiation, on the temperature, the concentration of dopants and hydroxyl groups in the core, and on the wavelength and power of the probe radiation are discussed. An analysis is made of the kinetic curves of the changes in the induced absorption both during and after exposure to the radiation. Some models describing the effects of radiation bleaching and optical bleaching are analyzed. The propagation of a bleaching pulse through a radiation-darkened waveguide is examined.

The results of measurements of the transmission of radiation emitted from a tunable CO₂ laser by the water vapor continuum in the range 9–11 μ are reported. The results for 23 laser lines are used to derive an approximate expression for the calculation of the continuous absorption of radiation by water vapor as a function of its temperature and pressure, as well as a function of the radiation wavelength and the pressure of the broadening gas. It is shown that this expression can be used to calculate the absorption of CO₂ laser radiation propagating in the atmosphere.

Measurements were made of the dependences of the stimulated Brillouin scattering (STBS) threshold and of the gain g (cm/MW) on the pressure of argon. The influence of the focusing geometry on the process of competition between STBS and optical breakdown was studied. The influence of breakdown on STBS was described by introducing effective nonlinear losses proportional to the intensity of the pump radiation. Within the framework of this approach a good agreement was obtained between the experimental and theoretical results.

An analysis is made of the hydrodynamics and ionization of matter in the process of interaction of laser radiation with targets made of heavy elements. An approximate method is developed to allow for the effects of ionization and a study is made of the influence of ionization on the hydrodynamic parameters of a plasma. Distributions of the electron density and temperature, and of the charge composition of a laser plasma are obtained.

Calculations are made of the gain in a multiply charged homogeneous stationary plasma due to transitions in neon-like ions in the 100–1000 Å wavelength range. The range of electron temperatures and densities for which the maximum gain is observed in the selected element is determined.

An experimental and theoretical study is reported of a spontaneous magnetic field which appears as a result of interaction of laser radiation with a target. The attention is concentrated on the early component of the field which appears simultaneously with the laser pulse and persists until a laser plasma arrives at the point of measurement. A theoretical analysis is made of the mechanism of the appearance of this early component of a spontaneous magnetic field because of the formation of a current system in which the source is in the form of fast photoelectrons generated by photoionization of the background media by the radiation emitted from a laser plasma. This theoretical model is used to calculate the intensity of a spontaneous magnetic field in a wide range of pressures of the background medium and laser radiation powers. The experimental results obtained using an external magnetic field indicate the existence of an internal source of the current responsible for the appearance of the early component of a spontaneous magnetic field and confirm the proposed theoretical model.

An investigation is made of the ionization of air by x rays emitted from a high-temperature region of the interaction between a laser pulse and a target. The role of the various ionization mechanisms is determined and it is found that at a distance of several centimeters from the target the degree of ionization of air reaches its maximum value when the pressure in the chamber is ∼0.1 Torr and the laser radiation intensity is ∼10¹³ W/cm².

An investigation was made of the influence of inhomogeneity of the gas density in the pulse-periodic regime on the average power of an excimer laser. The experimental results agreed qualitatively with the proposed model. An average power of ∼130 W was obtained from a pulse-periodic XeCl excimer laser at a repetition frequency of ∼500 Hz.

A theory is developed of intracavity second harmonic generation in multimode continuously pumped lasers with a homogeneously broadened gain profile. An analysis is made of the amplitude distribution and phase relationships between the generated modes. A theoretical and experimental study is reported of the spontaneous establishment of frequency modulation of the output radiation of a YAG laser with self-locking of longitudinal oscillation modes and intracavity frequency doubling. The conditions for the occurrence of this effect are determined. Spectral and time characteristics are given for the fundamental frequency radiation and for the second harmonic emitted by the YAG laser.

Radiative transitions from states located above the ⁴F_3/2 metastable state were observed in a γ-La₂S₃:Nd³⁺ semiconductor single crystal. An analysis of the temperature dependences of the radiation spectra using timeresolution spectroscopy, an analysis of the excited-state decay curves, and a comparison of the emission and absorption spectra were used to identify the intermultiplet transitions observed in the emission spectrum. It was found that neodymium ions could be excited in the fundamental absorption band of the host.

A study was made of the fine structure of the excitation of the lower vibrational levels in SF₆ molecules gasdynamically cooled to temperatures of the order of 30 K. A two-frequency infrared–infrared laser excitation method was employed. A continuously tunable CO₂ laser was used for the first stage. At a frequency of 944.39 cm⁻¹ a contrast absorption peak was detected, having a width of less than 0.1 cm⁻¹ and corresponding to the A_1g two-photon resonance.

An investigation is made of processes of population and relaxation of the ⁴F_3/2 neodymium upper active level in a γ-La₂S₃ semiconductor single crystal and the energy transfer microparameters are determined. Nonradiative transfer of energy from a continuous set of traps to the ⁴F_3/2 upper active level of neodymium was observed when the sample was excited with λ = 0.53 μ radiation and cross relaxation from excited states located above the ⁴F_3/2 upper active level was identified.

Experiments are described on multiplying the frequency (7.4×10¹⁰ Hz) of a klystron and mixing the multiplied frequency with radiation of frequency 3.6×10¹² Hz from a D₂O laser. The nonlinearity of superconducting point contacts and the experimental method employed made it possible to multiply and mix at frequencies exceeding several times the ultimate frequency, and to investigate the mixing mechanism. The amplitude of the beat signal between the laser radiation and the multiplied klystron frequency was proportional to the differential resistance of the contact. Over a wide range of contact bias voltages, the frequency of the beat signal was independent of the Josephson emission frequency. No substantial difference was discovered between the nonlinear properties of the contacts at frequencies of 10¹⁰ and 3.6×10¹² Hz. It was found that superconducting point contacts enabled a considerable simplification to be made in the frequency synthesis chain of an He–Ne laser by excluding several klystrons, metal–oxide–metal diodes, and a bulky submillimeter HCN laser.

A theoretical analysis is made of the problem of the emission of light from a strip waveguide, formed inside a planar waveguide, into the latter waveguide and into the media surrounding it. A calculation is made of the spectral and angular characteristics of the process of emission of light into the planar waveguide. Estimates are obtained of the fraction of the power of light emitted into the planar waveguide. It is shown that a corrugated strip waveguide may be used in integrated-optics devices for demultiplexing of wavelength-division multiplexed optical communication channels.

A study was made of the energy characteristics and spectral composition of the radiation emitted by self-heating manganese vapor lasers as a function of their active-medium parameters and excitation conditions in discharge tubes of various diameters. The dependences obtained were used as a basis for discussing the lasing mechanism. The relationship was considered between the elementary processes occurring in the pulsed plasma discharge and the parameters of the emitted radiation. A total laser output power of 12 W, at an efficiency of 0.3%, was obtained in a 2-cm diameter tube of 200 cm³ volume.

An experimental investigation was made of the gain profile of an injection heterolaser and a satisfactory generalization of this profile was obtained in the form of expressions analogous to those that follow from the usual model of heavily doped gallium arsenide in which transitions take place between the density-of-states tail at the bottom of the conduction band and a local level, violating the selection rules on the quasimomentum.

Continuous frequency tuning was achieved for an NH₃ laser mixture above atmospheric pressure over a range of ∼0.25 cm⁻¹ in the vicinity of the frequency ν_L = 868 cm⁻¹. Measurements were made of the fine structure of the laser emission line due to the sP(5,k) transition and of the widths of the NH₃ laser lines due to the sP(5,k) and aP(5,3) transitions at various active-medium pressures.

A method was developed for the determination of the vibrational-translational (VT) relaxation time of gases, based on the dependence of the sensitivity of an optoacoustic detector on the pressure of the investigated gas in a cell under pulse excitation conditions. An optoacoustic spectrometer and a pulsed ruby laser were used to determine the relaxation time of the 103 vibration in H₂O vapor. The value obtained, τ_VT(103) = (2.1±0.4)×10⁻⁷ sec·atm, was in qualitative agreement with the results of an experimental determination of the VT relaxation time of the lower H₂O vibration modes (010, 100, 001, 020).

It is shown that the distribution of surface electromagnetic waves in the far-field zone has distinct maxima and minima. It is shown that interference in a surface electromagnetic wave, which becomes detached from the edge of a metallized substrate, with a wave which is scattered by a device used to excite the surface wave and which propagates along the substrate, can account satisfactorily for the nature of the resultant distribution of radiation.

Experimental and theoretical studies were made of the characteristics of an instability of beams with regular spatial spectra in the presence of small-scale self-focusing. The process differed qualitatively from small-scale self-focusing of a plane wave and the difference was due to the possibility of simultaneous growth of perturbations, of various spatial spectral components in the field of several pump components in the case of spatial phase matching between the interacting waves. The growth increments of the instabilities were calculated for different types of spatial spectra of pump beams.

An experimental investigation was made of some characteristics of the operation of Soviet K–Rb pump lamps designed for YAG:Nd³⁺ lasers. It was found that at low pumping rates these K–Rb lamps are efficient pump sources for YAG:Nd³⁺ lasers.

An investigation was made of the energy characteristics of a YAG:Nd³⁺ laser subjected to pulse-periodic pumping and to passive Q switching of a resonator by an LiF crystal containing color centers. A comparison was made of the energy of giant laser pulses obtained using passive and electrooptic switches when the pump pulse repetition frequency was up to 50 Hz. The use of a passive switch made of an LiF: crystal under optimal lasing conditions did not reduce the energy of the output pulses of the laser compared with that attainable using an electrooptic Q switch.

An investigation was made of the energy characteristics of stimulated Raman scattering (STRS) and of stimulated scattering in the Rayleigh wing (STSRW) of YAG laser pulses of 25 psec duration in benzene, carbon disulfide, and toluene. It was established that when the active-layer thickness was of the order of the spatial length of the laser pulses, the forward and backward STRS and STSRW processes were in the form of an amplified spontaneous noise of intensity which varied stochastically from one shot to another. The STRS and STSRW thresholds were governed by the relaxation times of the molecules in the active medium. When the thickness of the scattering layer was much greater than the spatial length of the laser pulses, the nature of the energy dependence of the forward STRS approached the energy dependence of the STRS excited by pulses of nanosecond duration.

An experimental investigation was made of the conversion of the second harmonic of the radiation of a dye laser of wavelengths 545—760 nm into ultraviolet radiation of wavelengths 217–280 nm by the method of sumfrequency generation. The use of a KDP crystal with phase matching by angular adjustment ensured that the conversion efficiency was 35%.

Temperature dependences of some polarization characteristics were determined for polymer Selfoc-type fibers. It was found that when plane-polarized light passed through a fiber of this kind, it emerged with elliptic polarization. The effective direction of the polarization of light emerging from a fiber was shifted by an angle Δφ from the plane of polarization of the incident wave. The temperature dependence of Δφ was studied. It was found that the investigated graded-index fibers were optically biaxial.

A method is proposed for the optimization of metal vapor lasers on the basis of a universal numerical calculation program and simultaneous application of an algorithm for multifactor optimization of the output parameters based on the complex Boks method and the Gel'fand–Tsetlin ravine function method. The results are given of a three-parameter optimization of a transverse-discharge copper vapor laser.

An investigation was made of the influence of single-mode radiation from an injection laser on the magnetic resonance signal as a function of the laser radiation frequency. It was found that the amplitude, phase, and rate of decay of the free precession signal depended on the tuning of the laser radiation frequency within the Doppler profile of the line representing the hyperfine levels of the ground state of cesium.

An investigation was made of the efficiency of coupling—into fiber waveguides—of 1.2–1.6 μ radiation emitted by a buried mesastripe InGaPAs–InP heterojunction laser. The maximum power of the radiation coupled into a fiber waveguide was 16 mW in the cw regime at room temperature. The coupling efficiency was 90% in the case of a multimode fiber waveguide and 36% in the case of a single-mode waveguide when matching was provided by a microlens with a radius of ∼10 μ

An investigation was made of the luminescence and lasing characteristics of 3-methoxybenzanthrone solutions of different acidity. It was established that at a certain acidity of a solution the transfer of molecules of this dye to an excited state produced a new ionic form resulting from the attachment of a hydrogen ion. When a solution with the optimal acidity was pumped with the second harmonic of a ruby laser, stimulated emission was observed for both ionic forms and continuous wavelength tuning was attained in the range 540–660 nm.

A study was made of the polarization characteristics of the radiation emitted by double-heterostructure AlGaAs injection lasers and of the influence of these characteristics on the efficiency of scattering of laser radiation by volume acoustic waves in a crystal of paratellurite. The efficiency of the acoustooptic interaction increased linearly on increase in the degree of linear polarization of the incident radiation. When the plane of polarization of this radiation was rotated relative to the scattering plane by 90° from the optimal position, the efficiency of this interaction was more than halved. The central frequency of an ultrasonic cell for the interaction with radiation of wavelength λ = 0.9 μ was 50 MHz and the efficiency of the interaction was ∼50%.

The relationship between the physical damage mechanisms in the case of single and multiple interaction is discussed. The results are reported of an experimental investigation of the process of bulk damage to optical materials as a result of repeated interaction with pulsed laser radiation (λ = 1.06 μ, τ ∼15 nsec).

An investigation was made of the energy, spectral, and time characteristics of an XeCI* discharge laser stabilized by an electron beam. The electron-beam current density could be reduced to 0.1 mA/cm². The maximum output energy of ∼10 J/liter was obtained for a mixture of the HCl:Xe:Ne = 1:10:500 composition at p = 4 atm. The absorption in the region of 500 nm within the emission band of Xe₂Cl was due to the absorption by Xe in lower metastable states.

The coefficient representing utilization of the electron beam energy (K ∼2.3×10⁻³) in dissociation of XeF₂ vapor was determined. This dissociation occurred under the action of selective radiation emitted from electron-beam-excited Xe₂^* dimers. Lasing was observed as a result of the C–A transition in the XeF* molecule (λ = 480 nm) and the output energy was 3.1 mJ.

A description is given of a relatively simple method for determining imperfections of the shape and microdefects on the reflecting surfaces of solids of revolution (balls and rollers). It is shown that the method is characterized by an interference sensitivity to surface geometry defects and by a relatively high immunity to errors.

An investigation was made of inhomogeneously pumped injection lasers in the form of Al_xGa_1-xAs–GaAs double heterostnictures. Bistable operation of such lasers was demonstrated and the switching time between the two states was less than 2×10⁻¹⁰ sec. A study was made of regular pulsations of the output radiation resulting from inhomogeneous pumping. The pulsation frequency was tunable up to 2 GHz and the duration of each pulsation (spike) was less than 2.5×10⁻¹ sec. It was found that the pulsation frequency obeyed f ∝ (I–I_th)^1/2, where I and I_th are the current through the heterodiode and the threshold value of this current, respectively.

Apparatus was constructed for investigating fast photophysical and photochemical processes resulting from selective excitation of vibronic molecular states. A single laser pulse emitted from a YAG:Nd mode-locked laser was amplified in a two-stage amplifier, frequency converted in a parametric oscillator, and used to excite molecules. A pulse of the continuum was used as the test pulse. A time resolution of ±3 psec and a precision of ±3×10⁻³ optical density units were attained in the absorption measurements carried out in a study of primary processes of conversion of the energy of light in photosynthetic reaction centers.

Eight laser transitions were observed in the range 0.8–1.25 mm when CF₃I vapor was pumped by radiation from a low-pressure CO₂ laser. The observed infrared and millimeter transitions were identified.

The threshold of stimulated Raman scattering was lowered by filling an optical delay line with hydrogen. Pumping was by a tunable neodymium laser. Lens–prism combinations were used as phase correctors in the delay line. The dependences of the energy of the Stokes component on the pump energy determined experimentally for different numbers of transits through the delay line were compared with the results of a calculation allowing for the losses in the components of this line. When the frequency conversion was by a factor of at least 2 and the tuning range was wide (tens of percent), the optimal performance was obtained from the optical delay line when total-internal-reflection prisms and lenses were combined in a single component and oriented at the Brewster angle.

A quantum efficiency of 65% (corresponding to a power efficiency of 2640%) was achieved in up-conversion of λ = 10.8 μ CO₂ laser radiation by resonant parametric mixing in sodium vapor.

A derivation is given of the second-order coherence function for the propagation of laser radiation in a moving delayed-response nonlinear medium. A solution of this equation is used in an asymptotic analysis of fluctuations of the radiation in the case of propagation over long distances.

An analysis is made of variants of systems which can extend the range of conditions under which the CARS method can be used. An analysis is made of the efficiency of such systems from the point of view of the condition for spatial phase-matching in four-wave interactions.