The requirements for quality parameters in radiation of different wavelength (i.e. CO 2 lasers and fiber lasers) have been defined so as to perform efficient oxygen-free gas laser cutting of large-thickness samples.The main channels of consumption of radiation power in the cutting process have been considered. It is noted that focused beam divergence not only decreases the cutting speed, but also causes cutting quality deterioration.

The effects of CW laser radiation with a wavelength of λ = 532 nm on ethyl methacrylate copolymer films doped with the Ag(hfac)COD silver precursor were studied. Laser heating of the polymer composite (up to 150-170 °C), induced by the formation of highly absorbing silver nanoparticles (NPs), brings about an accelerated photo-thermochemical decomposition of the precursor, plastification of the polymer, local transition of the composite matrix to a colloidal state and intense thermocapillary convection in the dynamic active colloid formed. As a result, a directed transport of silver NPs from the center of the laser beam to its periphery takes place, leading to the formation of a ring structure with a very high concentration of silver NPs.

The papers dealing with multipass modes in open stable resonators are reviewed. A numerical model of an axially symmetric resonator is described that permits the properties of multipass modes to be studied in wave approximation. It is shown that for Fresnel numbers larger than unity, multiple reflections of radiation from the stable resonator mirrors lead to sustained quasi-stationary field oscillations in the resonator which are indicative of the essential contribution of multipass modes. The calculations in filling the resonator with the active medium have been performed for two types of lasers: with the on-axis and off-axis gain maxima. Resonator designs are suggested, trajectory selection techniques are considered to provide high-quality radiation at large Fresnel numbers. The confocal resonator properties are analyzed in the context of competition between single-pass and multipass modes. Relying on the results of calculations for multipass mode generation, a critical analysis of the experimental works is presented suggesting a logical explanation for the peculiarities which had not been physically interpreted in the original publications. An advanced understanding of the physics of multipass mode formations allowed us to put forward a special design of stable resonators for the generation of high quality radiation in high-power lasers.

Since nowadays the economy of the Russian Federation depends greatly on export of these mineral deposits, it is necessary to start development and exploitation of new deposits in a short space of time. Thereby, it is necessary to start rapidly development and sophistication of the technologies for reconditioning, repair and enhancement of performance characteristics of the drilling equipment used for extraction of mineral deposits, particularly, in the Arctic zone. The list of domestic manufacturers of drilling equipment is shown. Domestic laser installations for such technologies are described in the article.

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