Enhancement of the brightness of radiation from a highpower phosphate- glass Nd3+ laser by spatial filtering of the beam in an amplifying channel

An experimental investigation was made of the influence of spatial filtering on the brightness of the output beam from the amplifying channel of a high-power laser system in which the active elements were Nd³⁺-doped phosphate glass rods. It was found that the brightness of the output beam could be increased substantially by an appropriate choice of the parameters of a vacuum spatial filter. A beam 40 mm in diameter with a peak intensity of 3.4 GW/cm² was obtained. Small-scale self-focusing did not cause appreciable energy losses in an angle of 0.25 mrad. The possible criteria for estimating the influence of small-scale self-focusing on the brightness of the beam being amplified were considered. These criteria should be useful in the development of systems of amplifying channels with periodic spatial filtering.