Table of contents

A review is given of the literature on the principles of compatibility and on matching methods suitable for integrated-optics devices and fiber-optic communication lines. The general principles of compatibility of fiber and other waveguides are given. A detailed analysis is made of the main coupling methods, including the direct excitation of the end face and the optical tunneling method. Devices for matching single-mode and multimode waveguides to various types of fiber waveguides are discussed comprehensively. Methods and devices for matching planar and three-dimensional waveguides are considered as well as corresponding methods for matching radiation sources (semiconductor lasers and light-emitting diodes) to fiber and other waveguides. General trends and principal directions of further research are considered.

An analysis is made of the interaction of concurrent fields in nonlinear optical or holographic media in which the refractive index is modified directly during recording. The speckle mode theory is used to derive a system of equations for the amplitudes of perturbations of the medium and also for the amplitudes of the interacting fields dependent on z and t; the latter may be both plane and speckle-inhomogeneous. Analytic and numerical solutions of this system of equations are obtained for some cases. The results are used to calculate the diffraction efficiency of transmission holograms made of media of the Reoksan type. Potential advantages expected from the use of speckle-inhomogeneous fields in recording such holograms are pointed out.

An investigation was made of the action of low-intensity cw visible light of wavelengths in the range 313–860 nm on the rate of DNA synthesis in a culture of HeLa cells. It was found that the synthesis of DNA was stimulated in three spectral ranges: 313–450 nm, 600–650 nm, and 750–840 nm. For a fixed dose the stimulation effect was very sensitive to the irradiation time (radiation intensity). The maximum increase in the rate of DNA synthesis occurred in ≲15 min from the beginning of irradiation and the effect was retained for several hours. The stimulation effect was less in the case of two-wavelength (dichromatic) irradiation of the cells with red and wide-band visible light.

Conditions are found for the self-excitation of an adaptive resonator with four-wave hypersonic reversing mirrors. The threshold intensities of the pump waves of such mirrors are identified: when these values are exceeded, optical radiation is generated in a resonator of this kind. The threshold values of the pump wave intensities and the lasing frequencies are shown to depend periodically on the distance between reversing mirrors.

An increase was observed in the population inversion and laser output power of an active medium compressed by a shock wave. The thickness of the compression region in which lasing was observed was 8–10 nm, even after the pump pulse had terminated.

A method is suggested for finding the field distributions and the dispersion relationships describing the effective refractive index of anisotropic graded-index planar waveguides with arbitrary parameters of the waveguide layer and an arbitrary initial optical anisotropy. An analysis is made of the characteristics of leaky modes in three types of currently used inhomogeneous waveguides formed on the surfaces of anisotropic materials.

A description is given of a high-power pulse-periodic radiation source with an extended luminous body and a high brightness temperature (∼30×10³ K) in the visible and near infrared parts of the spectrum. It is designed for laser and photochemical studies. A plasma is heated by a dynamic method based on thermalization of the kinetic energy of high-velocity plasma streams formed by magnetoplasma compressors of the erosion type; shock deceleration is the thermalization process. The results are reported of an experimental investigation of the spectral, energy, and dynamic characteristics of various shock deceleration configurations for plasma streams in vacuum and in gases (air, xenon), together with the spectral luminescence and lasing characteristics of molecular iodine vapor subjected to pulsed photoexcitation with radiation from the new plasmadynamic source.

It is proposed to use three-boson stimulated scattering to search for hitherto unobserved effects that should occur when three laser beams of wavelengths λ_1–3 intersect at certain angles. For λ₁ = λ₂ = 1–10 nm and λ₃ ≥ 10 μ, the attainable power densities should make it possible in principle to construct a frequency doubler with an efficiency 10⁻¹⁰–1 %, whereas for λ₁ = λ₂ < 1 nm and λ₃ ≥ 1 cm the efficiency should be of the order of 100%.

A method and software were developed for self-consistent calculation of the energy parameters of solid-state lasers of arbitrary geometry pumped optically by sources with various metal and nonmetal gas fillings. Calculations were made for the free-running regime. It was found that the gain is distributed inhomogeneously over the cross section of the active element. Laser radiation transfer was modeled in three-dimensions by a discrete-ray method. Numerical investigations carried out with the aim of testing the mathematical model gave results in satisfactory agreement with the experimental data.

An experimental investigation was made of the action of pulsed CO laser radiation on metals in a power density range, averaged over the focal spot, of from 0.5 to 2.5 MW/cm². It was found that on restricting the radial expansion of the plasma jet a transition occurred from an evaporation interaction regime to an absorption wave in air. The experimentally determined parameters of the absorption wave were compared with those calculated on the basis of one-dimensional theories of a subsonic radiation wave and of optical detonation. Data are obtained on the thresholds for the formation of plasma near metal surfaces.

A method was developed for recording the motion of gas in the region of an optical discharge which is based on observing the transport of specially created optical inhomogeneities by the gas. It was used to confirm the existence of a cold gas ahead of the discharge front and to obtain quantitative data concerning its motion. The conditions were realized for the propagation of an optical discharge plasma completely immersed in a laser beam, the laser radiation being only weakly absorbed in the discharge. A sudden change in the discharge front velocity on reaching the lateral surface of the laser beam indicated that the gasdynamic regime of the propagation of the slow combustion optical discharge had changed.

It was found that the first laser emission peak and a breakdown wave traveled from the cathode to the anode at a velocity of ∼3×10⁹ cm/sec (voltage pulse amplitude 300 kV). The delay of the first laser emission peak behind the ionization wave front was 8–10 nsec. The second laser emission peak propagated from the anode to the cathode at a velocity of 5×10⁹ cm/sec, roughly equal to that of an electromagnetic signal traveling along a coaxial line with a water insulator and a discharge tube acting as the central conductor.

A discussion is given of the problems of realizing wave-driven self-circulation of a gas mixture through the discharge chamber of a pulse-periodic CO₂ laser. Details of an apparatus are given and preliminary experimental results are reported. The characteristic features of a gas discharge in a wave-driven self-circulation regime are indicated. The flow velocity in the discharge was ∼10 m/sec.

A study is made of the propagation of partly coherent high-power light beams in absorbing media. A report is given of the first experimental observation of a reduction in the correlation radius on increase in the radius of a random beam, caused by thermal self-defocusing. The results are given of a determination of the dependence of the correlation radius on the beam power and on the absorption coefficient of the medium traversed by the beam. A theoretical analysis of the self-interaction of random beams is made by the method of integration over beam paths, based on a new technique in which it is postulated that a random beam creates a randomly inhomogeneous channel in a nonlinear medium and travels along this channel. The results of this theory are in agreement with some experimental data.

An analysis is made of the problem of kinetics of the superradiance decay in the case of nonlinear quenching of excited centers in four-level active media. A method is proposed for estimating the initial axial gain and of the stimulated emission cross sections of active media: it is based on a simultaneous analysis of the normalized superradiant flux and integrated population of the active medium. The proposed method is not sensitive to nonlinear quenching. A qualitative analysis is made of the decay of excitation in neodymium pentaphosphate crystals after pulsed excitation with laser radiation of the 0.538 μ wavelength and stimulated emission cross sections are estimated for the ⁴F_3/2→⁴I_11/2 transition in Nd³⁺ resulting in lasing at 1.051 μ and at some other wavelengths of this transition.

Theoretical and experimental investigations are reported of the interaction of spectral modes in an injection laser, including the case of an external dispersive resonator. A theory is proposed of a nonlinear interaction between modes which does not disappear on reduction in the intraband relaxation time and it is shown that this interaction suppresses amplification at relatively small separations (∼1/τ, where τ is the carrier lifetime) from the frequency of a strong mode. Experimental observations are reported of selective self-stabilization of single-frequency emission within a band of width 1/τ. This stabilization effect facilitates generation of highly coherent radiation in injection lasers.

The method of resonant light absorption was used to investigate the time dependences of the concentrations of ²D_3/2 and ²D_5/2 metastable copper atoms in the afterglow of a CuI laser. The change from green to yellow emission, which occurred at high concentrations of the copper iodide molecules and for delays close to the maximum, was due to an increase in the relative population of the metastable ²D_5/2 level at the end of the afterglow. This was evidently caused by the electrons being heated as a result of the quenching of excited copper halide molecules formed by recombination of the copper and halogen atoms.

An interferometric study was made of the active medium of a photochemical Kr₂F laser operating in the bleaching wave regime. It was found that a discontinuity of the refractive index appeared in the lasing zone because of photochemical reactions occurring under the influence of the pump radiation. The method of compensation for the optical losses is suggested.

An analysis was made of a new configuration of a laser utilizing the ⁴I_11/2–⁴I_11/2 transition in the Er³⁺ ions in YAG with a high activator concentration (∼5×10²¹cm⁻³). It is shown that at a certain excitation rate the cross-relaxation processes increase considerably the lasing efficiency and make it possible to achieve cw emission as a result of transitions from a long-lived lower level.

Operation of an LiYF₄:Er laser at 0.85 μ was observed in the three-level lasing regime, which could be useful in tackling the problem of increasing the output energy characteristics of this laser.

An analysis is made of the feasibility of using chemical radiative collisions R+X₂hν→RX+X* for the establishment of a population inversion. It is shown that the gain for the Xe+Cl₂ system may be considerably greater than 0.1 m⁻¹ when a source with a brightness temperature of 3×10⁴ K is used. An analysis is made of the composition dependences of the gain.

An analysis is made of synchronous pumping of a dye laser by the second harmonic of a YAG:Nd laser (the second harmonic was generated in a resonator made of an LiIO₃ crystal). The pump radiation was focused cylindrically and the advantages of such focusing were established. When the average pump power was 1.2 W, the output power of the dye laser was 150 mW. Tuning of the emission frequency was achieved in the wavelength range 570–630 nm.

A theoretical investigation is made of the tuning charactenstics and of the spectrum of an optical parametric oscillator with a quadratically nonlinear medium. Anomalous behavior of these characteristics is reported for a number of nonlinear crystals and it is attributed to the dispersion properties of these crystals. The observed anomalies can be used to generate wide-band picosecond radiation (continuum) in the infrared range, and also to form light pulses of duration amounting to a few femtoseconds.

A description is given of an intracavity spectroscopic system based on a laser utilizing F₂^- color centers in a crystal of LiF and operating in the free-running regime emitting at wavelengths in the range 1.1–1.25 μ. The color-center laser was pumped by a neodymium laser. The absorption spectra of water vapor, methane, and ammonia were recorded.

An analysis is made of methods for lifting restrictions on pulse shortening imposed by the material characteristics of a laser medium. These methods involve a deliberate inhomogeneous broadening of the gain profile and superposition of partial pulses in free space. The methods are applicable also to nonlaser fields.

The emission frequency of an injection semiconductor laser was stabilized using a resonance of the transmission of a high-Q confocal interferometer. A relative frequency stability of ∼10⁻¹⁰ was achieved.

A description is given of a YAG:Nd³⁺ laser with an unstable confocal resonator operating in the mode-locked regime. The resonator was from a 100% reflecting 2-m radius of curvature convex mirror and a concave glass substrate having a 4-m radius of curvature, which served as an exit mirror. A solution of dye No. 3274u in dichlorethane was used as a saturable filter. The latter had an initial transmission of 30%. For an active medium volume of ∼5 m³ the energy of a train of ultrashort pulses was 150 mJ, that of the maximum pulse in the train being 50 mJ. The pulse duration was ∼40 psec. The radiation divergence was close to the diffraction limit, having a value of ∼0.3 mrad.

A description is given of a spatial and temporal light modulator based on a structure formed from a glassy chalcogenide semiconductor and a liquid crystal operating in reflected light. An investigation was made of the main characteristics of this modulator. It was found that the use of a glassy chalcogenide semiconductor as a photosensitive layer ensured a high sensitivity (10⁻⁷ W/cm²) of the modulator as well as a high resolution, which amounted to 50 pairs of lines/mm when an optical fiber plate was used and 90 pairs of lines/mm without such a plate. The modulator was used successfully to transfer data from the screen of an electronbeam device to a coherent-optical data processing system.

A description is given of a compact cw electric-discharge CO laser with an output power of about 1 W in one line. The laser was constructed by taking a tube from a CO₂ laser of the LG-74 type; the tube diameter was 4.8 mm and its length was 40 cm. The laser was operated in the many- and single-line regimes. A single line was obtained by placing a prism inside the resonator.

A numerical experiment confirmed a formula obtained earlier for calculating the correlation function of the complex amplitude of the field in an unstable resonator in the presence of small-scale perturbations.

An experimental determination was made of the direction of propagation of a reflected wave in the case of a quasidegenerate four-photon interaction. This direction was different from the exact retroreflection of the signal wave. Characteristics of the deviation from the exact retroreflection were determined and it was found that the magnitude of the deviation depended strongly on the angle of incidence of the signal wave on the boundary of a nonlinear interaction region.

An analysis is made of the possibility of using the CARS method for remote measurements by excitation of an intense return wave in stimulated Brillouin scattering in the medium which is being probed. The results are reported of a model (laboratory) experiment on such remote probing, carried out using a neodymium glass laser (second harmonic) and a dye laser pumped by the second harmonic.

A time-of-flight neutron spectrometer was developed for diagnostics of a laser plasma produced in the Del'fin facility. This spectrometer was capable of measurements in a wide range (10⁶–10¹⁰) of numbers of neutrons per shot with an energy resolution from a few percent to tenths of a percent.

Fiber waveguides were made from As–S and As–Se glasses. They were investigated and it was found that the minimum optical losses amounted to 0.58–0.71 dB/m in the wavelength range 3.4–4.7 μ.

A study was made of the operating regimes of a sealed copper vapor laser with a long service life. The average laser output power was doubled by shortening the excitation pulses. It was possible to achieve a further increase in the service life with a negligible reduction in the average power. A maximum average power of 18 W was obtained using a "Kristall" active element.

The problem of quasienergy states of a three-level system in a strong optical field is solved for the first time. The solution makes it possible to find, in particular, the spectrum of resonance lines of hydrogen-like ions in a strong optical field. It is shown how the resultant effects (appearance of laser satellites and shifts of spectral components) can be used in the diagnostics of a plasma created by a laser or a relativistic-electron beam.

Thin-film interference polarizers made of SiO₂ and ZrO₂ layers were made and investigated. The technology of deposition of the layers is described. The results are reported of an investigation of the optical strength of such polarizers and the mechanism of damage is considered. It is shown that the investigated polarizers are suitable for use in high-power laser systems.

A laser continuously tunable in the range 766–820 nm was constructed. It utilizes an electronic–vibrational transition in chromium in a gadolinium scandium gallium garnet crystal kept at room temperature and subjected to nonselective flashlamp pumping.

An investigation was made of the dependences of the energy characteristics of lasing and of the efficiency of conversion of pump radiation on the pump power density up to 200 MW/cm² supplied to LiF: lasers. It was established that the dependences in question had maxima. This made it possible to optimize the lasers in respect of their output parameters. The output energy of an LiF: laser with a nonselective resonator reached 0.225 J and the efficiency of conversion of the pump energy was 38%. Preliminary experiments were also made on tuning of high-energy (in excess of 0.1 J) radiation from an LiF: laser and of conversion of this radiation to the second harmonic.

It is shown that, in principle, it is possible to initiate a pulsed chemical HF laser by the evaporation of fine metal particles with the aid of infrared radiation. It follows from the reported calculations that the laser radiation energy may be 3–5 times greater than the initiation energy, which opens up the way for constructing purely chemical pulsed HF laser amplifiers.

An investigation was made of a cw waveguide CO laser with a selective resonator without circulation or water cooling. Diffraction gratings with 300 and 150 lines/mm were used as selectors. Lasing was observed due to 40 vibrational–rotational transitions in the CO molecule with an output power of 0.02–0.08 W for the strongest lines. The maximum range of continuous tuning of the emission frequency was 420 MHz for the P(17) transition in the 10–9 vibrational band.

A study was made of light emitted as a result of decay of surface plasma oscillations in metal–oxide–metal structures. An absolute increase in the intensity of this light and its control were achieved by using a medium external to the metal film. This medium was a liquid crystal forming a domain structure in a static electric field. The arrangement provided a convenient means for investigating the processes of radiative decay of surface plasmons.

A report is given of the construction of a CO₂ laser in which the exciting discharge was stabilized by adding readily ionized organic substances to the mixture. The temporal characteristics of the laser emission pulses were investigated for a wide range of active mixtures and pulse durations from 10 μ sec to 150 nsec. A discussion is given of improvements in the output energy distribution over the beam cross section.

An investigation was made of the processes of degradation of the excitation energy in an Xe–F₂ mixture subjected to monochromatic (Δλ =0.3 nm) radiation which produced XeF excimers (D and B). It was concluded that the formation of XeF excimers on excitation of an Xe–F₂ mixture in the region of the atomic absorption of xenon involved participation of excited Xe₂ molecules.

An analysis is made of the formation of an absorbing inhomogeneity in solid transparent insulators under the action of high-power optical radiation. The inhomogeneity appears because of a thermally activated chemical reaction and the analysis is carried out during the stage when the inhomogeneity is optically thin. A relationship is established between localization of the process and the degree of nonlinearity of the temperature dependence of the chemical reaction rate. A quasisteady thermal regime is considered when the delocalizing action of heat conduction is manifested most strongly.

Experimental and theoretical investigations were made of a spatial and temporal modulator of light made of a Bi₁₂SiO₂₀ crystal. It was found that the resolution of a modulator made of this photoconducting crystal was practically independent of the intensity of the light being modulated. The optimal dimensions of the modulator crystal were determined as a function of the diameter of the electron beam.

It is shown that even low-intensity ultraviolet laser radiation may be a hazard to man because of nonthermal effects. Estimates are obtained of the maximum permissible exposures to such radiation. In the wavelength range λ =230–300 nm the maximum permissible daily exposure should be within the range 10⁻⁷–10⁻⁹ J/cm².

Streamer semiconductor lasers can be used for optical pumping of certain laser materials, such as dyes and semiconductors, and also in studies of photoluminescence of various substances with a high temporal and spatial resolution. A report is given of the use of radiation from a CdS streamer laser for optical pumping of a CdS_0.5Se_0.5 laser

A new method is proposed for constructing a parallel digital adder based on a device with a periodic operating characteristic. The data patterns of digits of two numerical arrays reach successively an adding device and form at its output a data pattern of the result in a given digit and a "latent" data pattern of carry to the next digit. The data carry pattern is then reconstructed by feedback and is added to the arriving data patterns in the next digit. The principal characteristics of such an adder and the requirements that its components must satisfy are considered.

A theoretical investigation is made of the dynamics of generation of a single picosecond pulse in a "nontransmitting" resonator of a dye laser pumped synchronously with pulses. It is shown that the energy of a single picosecond pulse circulating inside such a resonator may exceed severalfold the energy of any pulse in a pump train. The results are given of an experimental investigation which confirmed the theoretical predictions.

Stimulated Raman scattering by longitudinal optical vibrations in crystals of the lithium niobate type was observed for the first time. The excitation thresholds of stimulated scattering by transverse and longitudinal vibrations were compared. Data on spontaneous Raman scattering were used to estimate the stimulated scattering thresholds for transverse and longitudinal vibrations and a theoretical explanation was proposed for the experimentally observed differences between lithium niobate and tantalate crystals.