Table of contents

A new electric-discharge CO₂ laser with a peak power of up to 45 MW and a half-height pulse duration of 50 ns is developed. The short laser pulse was formed using a generator with a semiconductor opening switch. The maximum laser radiation energy reached 6.2 J and the efficiency with respect to the stored energy was 15%. The first peak contained 70% of the energy, and the pulse duration at the base did not exceed 1 μs.

The energy levels, wave functions, and matrix elements of optical dipole transitions are calculated numerically for superlattice quantum-cascade structures. The effect of spectral broadening on the shape of emission spectra is estimated and semiphenomenological asymmetric profiles of emission line broadening are proposed. It is shown that the electroluminescence spectra well agree with the calculated spontaneous recombination spectra.

The dependence of the frequency of self-modulation oscillations of the first kind in a solid-state ring laser on its parameters is studied theoretically and experimentally. It is shown that the nonisochronism takes place: the self-modulation oscillation frequency depends on the intracavity field intensity. The influence of the amplitude — phase coupling on the nonlinear frequency shift of self-modulation oscillations, depending on the excess of the pump over the threshold, is studied. Comparison of the experimental results with theoretical data made it possible to determine the amplitude—phase coupling coefficient.

The radiation amplification and oscillation are obtained in an electron-beam-pumped Berdysh laser with an active volume of 10 L in the visible range from 430 to 470 nm at the broadband 4²Γ → 1,2²Γ transition in the triatomic Kr₂F molecule of interest for amplification of ultrashort laser pulses. It is shown that, along with absorption of laser radiation in the active medium, the amplification dynamics is considerably determined by short-lived absorption induced in the amplifier windows by bremsstrahlung X-rays. For the specific pump power 0.6 — 0.7 MW cm^-3, the gain, corrected for nonstationary absorption, was ∼10^-3 cm^-1. A scheme of a Kr₂F amplifier is proposed for amplification of ultrashort pulses up to multiterawatt peak powers in the active volume ∼10 L.

A new method involving the expansion of the field coherence function in partially coherent modes — the eigensolutions of the problem for the second-order coherence function in a stable resonator — is proposed for the theoretical description of the process of multimode laser beam formation. The method for solving the problem for arbitrary partially coherent modes is formulated and the expressions for these modes are derived in the general form. The characteristics of the fundamental partially coherent mode, which coincides with the coherence function of a Gaussian partially coherent beam, are analysed in detail. The partially coherent modes are shown to possess two spatial scales — the effective radius and the coherence radius, which makes them a convenient tool for solving the problem of generation of a partially coherent beam. It is found that the unambiguous relation between the characteristics of partially coherent modes and the stable-resonator parameters is achieved by involving into consideration not only the process of the beam formation by the resonator mirrors but also the process of interaction of radiation with the active laser medium.

The physical difference between the concepts 'Fabry—Perot interferometer' and 'open resonator' is discussed. It is shown that the use of the term 'Fabry—Perot resonator' for open laser resonators is incorrect both from the historical viewpoint and from the viewpoint of the physical meaning of the processes occurring in these resonators.

It is shown that under the degenerate conditions (SHG and type-I degenerate parametric generation), the increase in the order of a system of truncated wave equations reduces the initial problem to the solution of two independent nonlinear Schrödinger equations, which allows one to write down the analytic solutions of the corresponding problems by using the standard methods for constructing the searched-for solutions in the form of cnoidal waves. It is established that in realising of cascade processes (quasi-synchronism), one of which is degenerate, this approach based on the introduction of the concept of the effective cascade cubic nonlinearity is not very convenient because the latter in the general case is no longer the Kerr one.

The quantum dynamics of a system consisting of a moving two-level atom and a single-mode electromagnetic field in the standing-wave resonator is studied by using the stationary phase approximation. The conditions resulting in the emergence of the collapse — revival effect of Doppler — Rabi oscillations are analysed for the initial coherent state of the electromagnetic field in the resonator. It is shown that both the character and the possibility of this effect emergence directly depend on the initial parameters of the system: the rate of the atomic centre-of-mass motion, coupling constants of the atom with the field, the mean number of photons in the resonator. Under conditions when the collapse — revival effect is absent, the system dynamics qualitatively depends on the intial electronic state of the atom.

The possibility of producing self-similar frequency-modulated (FM) optical wave packets in length-inhomogeneous active fibres is studied for optical pulses with the initial Gaussian, hyperbolic-secant or parabolic shape. The conditions for converting these pulses into stable parabolic-type pulses with a constant frequency-modulation rate are considered. It is shown that the use of FM pulses of parabolic shape in active and length-inhomogeneous fibres can ensure the creation of an all-fibre generator—amplifier—compressor system with peak powers up to 1 MW and higher in the generated pulses.

Results of investigation of high-pressure argon plasma excited by a high-current pulsed volume discharge are presented. The plasma diagnostics employs spatiotemporal dependences of the emission intensity in the VUV — visible range. A homogenous discharge is observed at pressures up to 10 atm. It is found that the spectrum of the UV — visible photorecombination continuum is sensitive to the discharge constriction. Change in the shape of the spectrum is caused bythe change of the type of positive charge carriers upon passing of the discharge from the uniform phase (molecular Ar₂⁺ ions) to the arc phase (atomic Ar⁺ ions). Experimental data and model calculations show that the electron heating after the main excitation pulse is a highly undesirable process. It slows down the recombination flow in the plasma, which results in stretching of all the kinetic processes for all excited components in time, and hence in a decrease in the peak values of their concentrations. Electron collision-induced mixing effi-ciently converts the reservoir of long-lived Ar₂* molecules in the triplet state into rapidly emitting singlet excimers. It is this mechanism that dominates the production of singlet Ar₂* excimer molecules. The threshold concentration needed to obtain lasing at a wavelength of 127 nm on Ar₂* excimers (¹Σ⁺_u(v=0)) was, according to calculations, about 5×10¹⁵ cm^-3 for the gain 0.05 cm^-1. This concentration can be achieved in the case of homogeneous pulsed discharge pumping with the peak electron concentration 2.×10¹⁶ cm^-3 at the argon pressure 10 atm.

Plasma emission of a pulsed diffuse discharge produced at increased pressures due to the preionisation of the gap by runaway electrons is studied in argon, krypton, and xenon. Nanosecond voltage pulses with the amplitude ∼220 kV were applied to the discharge gap. It is shown that the presence of xenon (∼0.01%) in argon and krypton leads to the emergence of high-power narrowband radiation at awavelength of 147 nm. It is assumed that this radiation belongs to the bands of heteronuclear molecules Xe*Ar and Xe*Kr.

We report experimental and theoretical studies of the optical properties of composite nanoparticles consisting of a noble-metal (Ag or Au) core and a cyanine dye J-aggregate shell. Using transmission electron microscopy, the particles have been shown to be spherical in shape and 4 — 10 nm in size. The crystal structure of their core has been determined by 1-keV electron diffraction. The absorption spectra of such nanoparticles in aqueous suspension show two peaks, one dueto the plasmon resonance in the metallic core, and the other to electronic excitations in the J-aggregate shell. These results are interpreted in a model based on the expression for the absorption cross section of small particles, using polarisability calculations for two concentric spheres with allowance for the size effect on the dielectric function of the metallic core. The dielectric function of the J-aggregates is derived from experimental data using Kramers — Kronig relations. The shape and position of the peaks in the absorption spectra of the hybrid nanoparticles are strongly dependent ontheir geometry and the optical properties of the core and shell materials. This offers the possibility of controlling the optical properties of composite materials based on such nanoparticles.

This paper presents detailed experimental and theoretical studies of the mode composition of light propagating along microstructured fibres having a solid core formed by 7 or 19 missing holes and differing in geometric parameters. The results are used to derive conditions for single fundamental mode operation of the fibres.

The possibility of apodization of fibre Bragg gratings (FBGs) recorded in the region of interference of the two parts of a Gaussian beam in a Lloyd interferometer is considered. The reflection spectra of FBGs are numerically simulated for different parameters of the recording beam and its displacement with respect to the dividing axis in the interferometer. Aconsiderable suppression of sidelobe resonances in the FBG spectrum during the displacement of the beam centre with respect to the dividing axis by half the beam radius is predicted and experimentally demonstrated. It is shown that this is caused by the equating of the mean value of the refractive index in the FBG region.

The photoinduced growth of the refractive index of phosphosilicate glass during Bragg grating inscription and the thermal decay of the grating have a number of unusual features. The observed index variations are interpreted in terms of a new model for photoinduced glass network rearrangement. The model assumes the formation of photoinduced voids (nanopores) in the glass network near point defects. The nanopores may migrate through the network via bond switching when the network is in a 'soft' state. The photoinduced variations in network density lead to index variations.

A fast bolometer built in a plate of diamond grown at high pressure by the gradient growth method is developed and fabricated. The parameters of this structure are compared with these of the structures investigated earlier, which were fabricated based on chemical vapour deposited (CVD) diamond and natural type IIa diamond.

This paper presents novel pyroelectric sensor design concepts for laser output measurements using a pyroelectric response induced in quartz. The proposed sensor design strategy relies on the relationship between the electric field configuration in a thermodynamically nonequilibrium crystal and the purpose-designed electrode geometry for light flux measurements. We describe various classes of pyroelectric sensors based on polarisation effects.

A Faraday isolator is described in which thermal effects are suppressed by cooling down to liquid nitrogen temperatures. The principal scheme, main characteristics and modifications of the isolator are presented. The isolation degree is studied experimentally for the subkilowatt average laser radiation power. It is shown that the isolator can be used at radiation powers up to tens of kilowatts.

An outstanding Russian scientist Zhores Ivanovich Alferov was 80 on 15 March 2010. The contribution of Zhores Ivanovich to modern solid-state physics cannot be overstimated - his name is among classics of this science. Many works of Zh.I.Alferov initiated new directions in the development of semiconductor physics. First of all these are his efforts devoted to the development and investigation of semiconductor heterostructures and devices based on them.

It is shown for the first time by the method of four-photon coherent scattering by rotational molecular resonances that the cavitation action on water changes its chemical composition, resulting in the formation of hydrogen peroxide. It is found that the concentration of hydrogen peroxide during cavitation grows by several times and depends on the cavitation process technology.