Optimization of the spatial profile of a high-power optical beam in the amplifier channel of a neodymium-glass laser system

Photographic-film apodizing apertures were developed and used in a high-power laser system with neodymium-doped phosphate glass rods as the active elements, is reported. The aperture of the output amplifier state was 45 mm. The parameters of the optical system of the amplifier channel were taken into account in the development of the transmission profiles of the apodizing apertures. A method of estimating the Fresnel number of the channel was developed and the principles of building an amplifier channel with an optical repeater were considered. An experimental investigation was made of the gain of beams having an approximately rectangular spatial profile. An output beam had a peak power of 50 GW and suffered no appreciable loss of brightness as a result of small-scale self-focusing.