Table of contents

To put the development of the X-ray laser in historic context, this paper presents some of the motivation and history of the development of the X-ray laser from the perspective of a scientist at the Lawrence Livermore National Laboratory where the first X-ray laser was demonstrated in the early 1980s using a nuclear device as the driver.

The results of investigation of a capillary discharge plasma, used as a source of intense VUV radiation and soft X-rays, are presented. The plasma was generated during the discharge of low-inductance condensers in a gas-filled ceramic capillary. Intense line radiation was observed in a broad spectral range (30-400 Å) in various gases (CO₂, Ne, Ar, Kr, Xe). The absolute radiation yield for the xenon discharge was ~5 mJ (2π sr)^-1 pulse^-1 within a spectral band of width 9 Å at 135 Å. Such a radiation source can be used for various practical applications, such as EUV projection lithography, microscopy of biological objects in a 'water window', reflectometry, etc.

The paper is devoted to a 469-Å X-ray laser excited by a fast capillary discharge in neon. The basic characteristics of the active medium and laser beam are presented. Applications of the laser in the studies of plasmas with densities of up to 10²⁰ cm^-3, in interferometry, reflectometry, for analysis of materials, etc. are described. A brief historical review is presented and the current state of the art in the development of laboratory X-ray lasers is considered.

The possibility of polarising ³He and preserving the polarisation in an external magnetic field of 0.05 Oe is demonstrated experimentally. A neutron filter with an extremely weak guiding field is fabricated for obtaining polarised neutron beams. The degree of polarisation equal to 25% was obtained for 0.025-eV neutrons. Some fields of application of other polarised noble gases are considered. The cross section for cross-relaxation of nuclear polarisation in the ¹²⁹Xe — ¹³¹Xe mixture is estimated.

The problems involved in designing autonomous mobile laser systems based on high-power cw chemical DF lasers, whose mass and size parameters would make it possible to install them on various vehicles, are discussed. The need for mobility of such lasers necessitates special attention to be paid to the quest for ways and means of reducing the mass and size of the main laser systems. The optimisation of the parameters of such lasers is studied for various methods of scaling their systems. A complex approach to analysis of the optical scheme of the laser system is developed.

A simplified model of the propagation of intense laser beams in the turbulent Earth's atmosphere along horizontal and oblique paths is improved. The model takes into account the basic mechanisms of interaction of laser radiation with the Earth's atmosphere (molecular absorption, aerosol extinction, turbulence-induced beam spread and wander). The application of this model demonstrates a general approach to determining the optimal radiation wavelengths for attaining the maximum intensity of focused laser radiation at a stationary object depending on the path length, angle of the path inclination, weather conditions, and diameter of the laser output beam. A simple physical interpretation of the dependences obtained is presented. The efficiencies of propagation of various high-power laser beams through the turbulent Earth's atmosphere are compared. Specific features of the energy transfer from various lasers to moving objects are analysed. It is shown that, when weather conditions change over a wide range, it is expedient to use radiation from a cw chemical DF laser.

The characteristics of the first excimer laser and the history of its creation are presented. The threshold lasing conditions and the modern theory of active media are considered, and the prospects for the development of excimer lasers operating on condensed inert gases are discussed. It is shown that in experiments on pumping liquid xenon, lasing was obtained simultaneously on excimers of several types, including excimers in liquid and gas phases.

The history of the origin and development of the lunar laser ranging is described. The main results of lunar laser ranging are presented and fundamental problems solved by this technique are listed.

The main factors determining the lasing threshold and efficiency of a laser cathode-ray tube at room temperature are considered. Recent achievements obtained by using laser screens made of the II — VI compound single crystals are discussed. It is shown that multilayer heterostructures allow the reduction in the lasing threshold by several times.

A growth of fractal aggregates in laser plasma with a dispersion phase is discussed. The molecular compositions of saturated vapours produced by the effusion Knudsen method and by laser ablation are compared. A considerable attention is given to gas-like clusters. The formation of macroscopic structures during relaxation of the laser plasma and the role of dipole interaction in the aggregation of compact clusters are considered.

A change in the spectrum and the energy distribution of the light field of a high-power femtosecond laser pulse is studied numerically in a broad range of its spatial scales. It is shown that the effect of filamentation, the generation of a supercontinuum and conical emission, the formation of a ring structure in the distribution of the pulse energy and other effects observed during the propagation of the laser pulse in air are caused by the nonlinear-optical transformation of the light field in the region with dimensions exceeding substantially the transverse size of the filament. The pulse filamentation is accompanied by the redistribution of power in its cross section. The spatio — temporal characteristics of emission calculated for femtosecond laser systems are in quantitative agreement with the experimental data.

A problem of the four-wave interaction of radiation in a three-level medium, where the lower working level is a repulsive one, is solved. This situation is characteristic of UV-active excimer molecules. The solution to this problem is compared to the results obtained for a two-level model. The coefficient of reflection into a conjugate wave is measured as a function of the small-signal gain in an active XeCl excimer plasma. An influence of the four-wave interaction on the characteristics of optical amplifiers and master oscillators operating with narrow-band radiation is observed.

The possibility of excitation of convective motions of the Rayleigh — Benard and Marangoni type in isotropic liquids and nematic liquid crystals upon absorption of light with a spatially periodic intensity distribution is demonstrated theoretically and experimentally. It is shown that gravitational and thermocapillary surface hydrodynamic waves are observed in the case of a running interference pattern. The possibility of control and the stability of convective motions are investigated. Benard cells become unstable when the light intensity is high. These instabilities are of thermal origin because the Prandtl number for the medium under investigation is considerably larger than unity. The competition between the gravitational and thermocapillary mechanisms of photohydrodynamic reorientation of the nematic liquid crystal director is also studied. The effect of convective motions on the thermodynamic phase transition is observed and explained.

An optical fibre with low optical losses is manufactured from a sulphur-doped quartz glass. Optical absorption spectra are measured for various parts of the fibre core. Most of the bands of these spectra are assigned to oxygen-deficient centres and colour centres containing sulphur atoms. The photosensitivity of glasses exposed to laser radiation at wavelengths of 193 and 244 nm is investigated to estimate the possibility of their application for producing photorefracting devices. A Bragg grating of the refractive index with Δn = 7.8 × 10^-4 is written in a sulphur-doped silica fibre.