Sergei I. Kliment'ev

Features of application of elastic membrane primaries in observing telescopes with nonlinear optical correction of images

Some last ten years the problem of compensation for dynamic distortions of primary mirrors in low-weight large-size imaging telescopes by methods of dynamic holography is actively being investigated. Today the performance of such systems has been experimentally proved. Thus, the idea to use in such a telescopic system a low-weight-film primary mirror, which can, in principle, be of large diameter in an unfolded mode, is very attractive one. In this paper the problems are considered related to integration of a thin- film primary mirror in a telescope with a non-linear corrector for an object image. Namely, there will be discussed the architecture of the telescope with the thin- film primary, optical quality of the mirror, requirements on the non-linear corrector, the telescopes field of view, and quality of the image of an object.

Powerful Nd:YAG laser of two active elements with improved divergence of output beam

An unstable resonator for a laser based on two Nd:YAG active elements with induced thermal lenses is proposed and investigated. The output beam divergence greater by factor 2 than the diffraction limit is achieved. The radiation power of the laser with the resonator proposed has been obtained 20% below but with the 30 times greater on-axis intensity as compared to the ordinarily used resonator in a commercial laser of a similar type.

Compensation for distortions of a telescope's primary mirror by means of a volume dynamic hologram

We describe a number of experiments devoted to compensation for aberrations in the primary mirror of a telescope using a volume dynamic holography technique, where the writing and reading of the hologram are carried out independently. Three sets of experiments demonstrating holographic aberration correction have been performed. In all cases transmitting holograms were formed in photorefractive crystals such as BSO and SBN. In experiments with a small diameter primary mirror the image is formed by a multicolor point-like object. The system includes a unit which compensates for the hologram dispersion. The aberration correction of a six- segmented primary mirror of 150 mm in diameter is demonstrated in conditions where there is a pronounced difference in the wavelengths of the recording beams and that of the source observed (Δλ=0.12 μm). The experiments on observation an extended object of continuous spectrum (Δλ=0.35 μm) with a single primary mirror of 150 diameter have been also made. All these experiments indicate an efficient compensation of distortions of the primary mirror by the hologram.

Electrically controlled preshaped membrane mirror for systems with wavefront correction

The paper is devoted to investigating the ways of development of the lightweight mirrors with imperfect optical quality but still suitable for being used in the telescopes with the primary mirrors aberration correction. The work involves the studies aimed at creation of the lightweight membrane mirrors with satisfactory optical quality and a suitable value of the F-number of around 1. As the first step, we demonstrate the possibility to control parameters of a pre-shaped membrane mirror by means of electrostatic field. It is shown that both the spherical component of the shape of the membrane mirror and its astigmatism can be controlled using the proposed approach.