Table of contents

We have prepared ²⁸Si, ²⁹Si and ³⁰Si single crystals with enrichments above 99.9 at % and a silicon single crystal of natural isotopic composition. The oxygen and carbon concentrations in all the crystals are within 5×10¹⁵ cm^-3, and the content of metal impurities is 0.01 — 0.1 ppma. The refractive index of the crystals has been determined in the range 1.05–25.5 μm using interference refractometry, and its dispersion and material dispersion have been determined.

The classic examples of optical phenomena resulting in the appearance of solitons are self-focusing, self-induced transparency, and parametric three-wave interaction. To date, the list of the fields of nonlinear optics and models where solitons play an important role has significantly expanded. Now long-lived or stable solitary waves are called solitons, including, for example, dissipative, gap, parametric, and topological solitons. This review considers nonlinear optics models giving rise to the appearance of solitons in a narrow sense: solitary waves corresponding to the solutions of completely integrable systems of equations basic for the models being discussed.

The performed numerical simulation shows that the main parameter determining the performance of an optical amplifier/modulator is the stimulated-emission cross section (differential gain) in the active region. A cross section of ∼3×10^-15 cm², which is quite realistic for modern heterostructures with quantum-well active regions, may provide an amplifier/modulator performance sufficient for data transfer at a rate of ∼20 Gbit s^-1.

Transition from generation of the fundamental mode to generation of the fundamental and first modes is studied numerically under the action of nonstationary asymmetric perturbations of pump rate and loss distributions in the active medium layer. It is shown that emergence of perturbations directly leads to excitation of the first mode with significant amplitude. The regime of two-mode lasing in the presence of perturbations is shown to appear at a pump rate that is smaller than the threshold one for two-mode lasing in the absence of perturbations. It is found that the first-mode amplitude has a maximum at a frequency of intermode beatings of an unfilled Fabry—Perot resonator. It is also determined that emergence of nonstationary asymmetric perturbations leads to an increase in the average intensity of the fundamental mode. Various transition regimes to two-mode lasing are compared in different types and periods of perturbations. The operability of the scheme controlling the mode composition of laser radiation is considered.

The concentrations of electron-excited particles have been determined by measuring the absolute spectral irradiance in the range of 600 — 800 nm of O₂ — O₂(¹Δ) — H₂O gas mixture at the output of a chemical singlet-oxygen generator (SOG). A nonequilibrium population of the first vibrational level of O₂(¹Σ) molecules has been clearly observed and found to depend on the water vapour content. In correspondence with the results of these measurements and according to the analysis of kinetics processes in the O₂ — O₂(¹Δ) — H₂O mixture, the maximum number of vibrational quanta generated in the O₂(¹Δ) + O₂(¹Δ) → O₂(¹Σ) + O₂(³Σ) reaction is 0.05 ± 0.03. It is concluded that the vibrational population of O₂(¹Δ) at the output of the SOG used in a chemical oxygen—iodine laser is close to thermal equilibrium value.

The self-quenching kinetics of O₂(¹Δ) molecules in the O₂ — O₂(¹Δ) — H₂O gas mixture produced by a chemical singlet-oxygen generator for an oxygen—iodine laser is investigated. The rate of change in the O₂(¹Δ) concentration in continuous-flow tube is determined by measuring the absolute spectral irradiance of the O₂ — O₂(¹Δ) — H₂O gas mixture in the ranges of 600 — 800 nm and 1210 — 1330 nm. The effective rate constant of O₂(¹Δ) deactivation in all possible channels of the O₂(¹Δ) + O₂(¹Δ) → products reaction is found to be (8±1.2)×10^-17 cm³ s^-1.

Annealing of individual bands of electron-beam-induced absorption (IA) in the region of 150 — 400 nm in KS-4V, KU-1, and Corning 7980 (ArF Grade) quartz glasses by ArF laser radiation is studied. It is shown that the phototransformation of the IA spectra occurs mainly due to a significant decrease in the amplitudes of bands at λ = 183.5, 213, and 260 nm. The role played by interstitial oxygen, hydrogen, and chlorine in the formation and relaxation of glass defects is considered.

The results of computing experiments are presented, which allow estimating the parameters of the laser foreplasma used to initiate a discharge in a laser-plasma diode. The resultant plasma is a material medium which carries a high-power discharge current. This opens a possibility to make a compact source of hard X-ray radiation and fast-ion streams. Proceeding from our numerical simulations we derive similarity relations, which enable determining the fluxes of plasma mass and charge as functions of laser pulse parameters.

The frequency shift Δv of the fine structure components of Rayleigh light scattering in 4-methylpyridine water solutions is studied in the ranges of 1 — 0.1 mole fraction concentrations and temperature 10 — 80 °C. The laws of Δv variation at different light scattering angles are discussed from the viewpoint of solution structural reorganisation under the varying temperature and concentration of nonelectrolyte in water. Existence of a continuous hydrogen-bond net in the solutions is experimentally proved in a certain range of temperatures and concentrations.

It is shown that the angular phase-matching bandwidths in biaxial nonlinear crystals in the general case must be calculated in the coordinate system in which the angular deviations of the crystal and the laser beam divergence are determined consistently. The angular phase-matching bandwidths in this coordinate system may considerably differ from the conventionally determined values. The optimum orientation of the coordinate system for determining the angular phase-matching bandwidths is found. It is established that, in the general case in biaxial crystals, as in uniaxial ones, phase matching is always angle-critical along one coordinate and noncritical along the other and that it is possible to realise angle-noncritical phase matching of the fourth order.

Optical fibres have been fabricated for the first time from As₂S₃ glass containing chromium-doped ZnS and ZnSe crystals, and their optical loss and luminescence spectra have been measured in the mid-IR. In the spectral range 2 — 3 μm, the optical loss in the fibres is 2 — 4 dB m^-1. The fibres have a broad luminescence band in the range 1.8 — 3 μm, with a maximum near 1.9 μm, which is due to Cr²⁺⁵E — ⁵T₂ intracentre transitions in the II - VI host.

Propagation of a guided mode (eigenmode) through an integrated optical generalised waveguide Luneburg lens is numerically simulated for the first time in terms of the previously obtained analytical solution of the vector electrodynamic problem in a smoothly irregular four-layer integrated optical 3D waveguide. The dispersion relation for a four-layer continuously irregular integrated optical 3D waveguide is calculated within the approximations of the asymptotic method of comparison waveguides and the method of adiabatic modes, in particular, taking into account the shift of the propagation constants of quasi-TE and quasi-TM modes. A generalised waveguide Luneburg lens with a full aperture is synthesised in the zero-order approximation. The results of numerical simulation demonstrate, on the one hand, a very good coincidence of the solution to the stated problem obtained in the approximation of the method of comparison waveguides with the previous results, and, on the other hand, advantages of our method: more rigorous solution of the problem, more complete consideration of its physical peculiarities, and higher accuracy of calculations. Another undoubted advantage of the analytical method proposed here is that it can be used to analyse similar structures fabricated of dielectrics, magnetics, and metamaterials, including nonlinear materials, in a wide range of electromagnetic wavelengths.

The problem of diffraction of divergent image-transfer light beams by an acoustic wave is considered. Expressions that describe the transfer function as a function of spectral and angular coordinates and are valid for any birefringence are obtained for the first time. The main characteristics of wide-angle acousto-optic tunable filters (angular and spectral bandwidths) are calculated and compared with the experimental data. The dependence of the transfer function on the angle of light incidence is investigated and a fundamental change in its topology is shown.

The method of fluorescent microscopy is developed based on employment of a single-mode fibreoptic channel to provide high spatial resolution 3D images of large cleared biological specimens using the 488-nm excitation laser line. The transverse and axial resolution of the setup is 5 and 13 μm, respectively. The transversal sample size under investigation is up to 10 mm. The in-depth scanning range depends on the sample transparency and reaches 4 mm in the experiment. The 3D images of whole mouse organs (heart, lungs, brain) and mouse embryos obtained using autofluorescence or fluorescence of exogenous markers demonstrate a high contrast and cellular-level resolution.