For a group of 40 optical elements the output beam of the amplifier coincides with the input beam from the master laser, this coincidence being diffraction limited. There is a detailed description of these experiments. Very important and very similar to the SPS problem in terms of scale is an experiment which we recently carried out. It was a large scale experiment, based on phase conjugation phenomenon. The main purpose of this experiment was to study laser energy transportation through the highly turbulent atmosphere by large aperture laser beams. The principal topics of this study were: • The self-pointing of the main amplifier onto the source reference beam; • The compensation for optical imperfections in the atmosphere; • The phasing of a large scale, complex multielement optical system. The optics had a diameter of about 2 m, and the optical properties of the atmosphere could be described by an additional divergency of a laser beam of about 10 arc seconds as a result of the first passage through this atmosphere. Diffraction limited restoration of the laser beam, having such divergency after the first passage, has been achieved as a result of phase conjugation and of the second passage through this atmosphere in precisely the opposite direction. Equivalent beam divergence was about 0.3 arc second (this value really defines the angular diameter of a laser spot in the vicinity of source of reference beam, where the amplified beam is concentrated by 2m - diameter complex optics through such turbulence). On the basis of these experimental results, in the case of a full-scale L-SPS experiment, in GEO, laser-solar satellite optics of 2m diameter, irradiated by the reference beam from the ground-based station would allow us, by means of PCM, to concentrate laser radiation onto a ground-based converter with a 50 m diameter. For lower orbits, this diameter decreases (down to only 5 m for an altitude of 4,000 km). The total experiment results include laser energy transportation through a turbulent atmosphere, the phasing of large-scale, complex optics, the study of remote laser “request” by a weak reference beam, different lasers with PCM, as well as different PCM design and some new schemes for phase conjugation, which show that the conception of diffraction-limited laser beams is not only postulated, but has been strongly confirmed by experiments, some of them large-scale. It would be useful to carry out the integrating experiment for detailed investigation of energy transportation from orbit to surface, using PCM (this experiment could be based on present launchers. The main purpose of these experiments would be to obtain concrete data for optical cooperation of on board and ground based
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