Investigation of self-focusing and its suppression by spatial filtering in neodymium-glass laser amplifiers

An experimental investigation was made of the change in the radiation brightness of subnanosecond pulses in neodymium-glass laser amplifiers. It was found that spatial filtering can increase substantially (by an order of magnitude or more) the brightness of laser radiation at intensities of 1.5 GW/cm². An investigation was made of the change in the brightness in amplifiers of different length with active elements made of different types of neodymium glass. A comparative experimental investigation was made of self-focusing in a rod and in a set of disks. The experimental data are used to propose a calculation technique for multistage amplifier systems. A criterion for estimating self-focusing in an amplifier system is discussed.