Table of contents

An analysis is made of the physical principles of stimulated emission of laser pulses with extremely high power (up to 10¹⁵ W) and of very short duration (less than 1 ps). Relationships governing the interaction of such pulses with matter are discussed. It is shown that the phenomena that occur on exposure of transparent media and condensed targets to high-power ultrashort laser pulses are different in kind. Qualitatively new physical effects, whose appearance is related to nonlinear (including relativistic) effects in the laser-beam electric field are given special attention. The results of recent experiments and studies planned for the future are considered in conjunction with a theoretical analysis.

An analysis is made of the operating principle of all-optical waveguide switches in which data are encoded by orthogonal polarizations.

An interferometer utilizing a nonlinear polarization-conserving optical fiber was considered as an all-optical switch. This interferometer could process optical logic signals arriving at a high rate.

An investigation was made of the influence of the Ag⁺ diffusion conditions on the parameters of planar glass waveguides. The diffusion process had more than one stage, creating two regions with different characteristic dependences of the refractive index on depth (a quasitwo-layer waveguide). Industrial waveguide fabrication conditions were determined for ensuring not only a weak dependence of the effective refractive index of a mode on the waveguide depth, but also low insertion losses.

The influence of forbidden transitions on the structure and profile of the B–X gain band of XeCl molecules was investigated. The band calculated taking into account forbidden transitions showed better agreement with the experimentally determined lasing wavelengths of an XeCl laser than the band calculated assuming only allowed transitions.

A theoretical analysis of the operation of lasers utilizing vibrational-rotational transitions in diatomic anharmonic molecules was made taking into account the finite nature of the rotational relaxation rate. The conditions of validity of the equivalent two-level model describing these lasers were identified. Expressions for the populations of the upper and lower states participating in the lasing transition were derived using this model. Numerical calculations were made of the characteristics of an H₂–F₂ chemical laser using multilevel and two-level models and the results of the calculations were compared.

An analysis was made of the concentration dependence of the up-conversion energy transfer parameter ω₂. This dependence was quadratic at low excitation densities.

A method was developed for directly recovering the optical phase profile of a surface from measurements made with a differential phase optical microscope. A study was made of how the parameters of the differential phase optical microscope and experimental errors influenced the measurement accuracy and resolution of the microscope in the object plane. The refractive index profile of ion-exchange channel waveguides in glass and the surface profile in a Y coupler made by diffusing titanium into lithium niobate were recovered from the results of measurements with a differential phase optical microscope. A resolution of 0.5 μm was obtained in the object plane.

Photoinduced dichroism was observed and studied in optical fibers made of As₂S₃ semiconductor chalcogenide glass. It was found that the photoinduced dichroism exhibited optical reversibility and dark relaxation, and was accompanied by depolarization of light. The mechanism of the photoinduced dichroism was associated with the interaction between polarized radiation, whose photon energy was less than the band gap, and defect states of the As₂S₃ semiconductor glass oriented by this radiation.

A fiber-optic spectrum analyzer of the Michelson echelon type was investigated. Sections of a fiber-optic waveguide served as analogs of the plates of a classical Michelson echelon. The lengths of the waveguide sections were successively increased by a given amount. By virtue of the exceptionally low losses in fiber-optic waveguides, the resolving power of a fiber-optic spectrum analyzer can exceed greatly that of classical Michelson echelons. A prototype fiber-optic spectrum analyzer was built to demonstrate the resolution of longitudinal modes of a helium–neon laser with a 0.8-pm intermode separation.

An approach to analysis of wave propagation in a system of distributed-coupled nonlinear waveguides is proposed: a resonator is assigned to each waveguide and the behavior of a system of coupled nonlinear resonators is considered. Some effects in waveguide systems are studied with the aim of utilizing these to develop all-optical logic elements for supercomputers based on the thoroughly studied corresponding effects in nonlinear oscillating systems.

An analysis was made of the behavior of waveguide systems, operating in different excitation regimes, based on the concept of the similarity between processes occurring in coupled nonlinear waveguide systems and in coupled nonlinear resonators. The results obtained were used to develop a new optical logic element which corresponds to a nonlinear Fabry–Perot resonator.

A frequency converter for ultrashort pulses, based on a leucosapphire cell in which atomic barium vapor, is formed was realized for the first time. This converter makes it possible to generate picosecond and femtosecond pulses in the infrared, visible, ultraviolet, and vacuum ultraviolet spectral regions with a high efficiency. A method is given for determining the gain G for stimulated Raman scattering in a single laser shot. In the case of stimulated electronic Raman scattering in barium vapor with a 30 cm⁻¹ detuning, at a pressure of 0.1 Torr, and for a pump pulse duration of ~ 20 ps, a value of G = (0.2)I_p cm/MW was obtained (where I_p is the pump intensity) while the threshold pump energy was below 1 μJ. Other possible applications of a leucosapphire cell containing atomic barium vapor are also described.

It is shown that the propagation of a light pulse in an optical fiber is accurately described using the proposed simplified equation containing only one parametric constant denned by the relationship between the phase self-modulation and the group velocity dispersion. The results of a numerical solution of this equation in its range of validity bounded by the Raman lasing threshold showed good quantitative agreement with the experimental data obtained for the propagation of a 100-ps YAG laser pulse in an optical fiber.

An experimental investigation was made of intracavity second harmonic generation in a pulsed oxygen–iodine chemical laser. Lithium iodate was used as the nonlinear crystal. The efficiency of conversion of the radiation to the second harmonic was 8%. A comparison was made between the experimental results and the results of the numerical simulation. The results indicate that in a resonator with a total transmission of 1 % at the fundamental frequency the conversion efficiency may exceed 35% if the intracavity losses are low (less than 1 %).

The surface of a recording medium was illuminated with a nonuniformity of less than 10% using second-harmonic radiation from a neodymium laser and the characteristic features of the illumination were considered. A laboratory technology was developed for fabricating 10-cm diameter holographic optical elements. This was based on optimizing the characteristics of a dichromated gelatin film, while obtaining a surface relief by recording with a 0.53-μm radiation pulse. The high image quality formed by a holographic optical element, with a low light scattering level, provides grounds for predicting extensive use of solid-state lasers in the fabrication of holographic optical elements.