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 indepeadently.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 minor the image is formed by a multicolor point-like object. The system includes an unit wich compensates for the hologram dispersion. The aberration correction of a six-segmented primary mirror of 1 50 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 (AX=O.12 tim). The experiments on observation an extended object of continuous spectrum (&=O.35 tm) with a single primary mirror of 1 50 mm diameter have been also made.All these experiments indicate an efficient compensation for distortions ofthe primary mirror by the hologram.
Silicon-doped InSb films of 100 nm thickness were grown by molecular-beam epitaxy on undoped low-temperature InSb buffer layers on GaAs(100) substrates. For a set of samples grown with the same Si flux, the free carrier concentration also increased with buffer thickness, and an analysis which included an estimate of the donor-doping properties of the dislocations suggests that a fraction of the silicon may also be trapped at the dislocations, where it acts as an acceptor. Hall effect measurements, corrected for the effects of parallel conduction in the buffer layer, and surface depletion in the doped region, showed that the mobility of the Si-doped region improved as the buffer layer thickness increased, and reached corrected values as high as 15 000 cm 2 V −1 s −1 , approaching that of lightly compensated material. These mobility dependences are quantitatively consistent with the incorporation model.
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