Compact neodymium-glass amplifier for amplification of weak coherent radiation signals

An investigation was made of the feasibility of using cavity flashlamps to develop neodymium glass amplifiers with a high gain M per pass for amplification of weak signals. Active elements made of GLS22P glass of varying diameter were inserted alternately in the internal cavity of INK-22 and INK-12 flashlamps. It was found that an increase in the density of packing the optical pumping system with the cavity flashlamps (an increase in the ratio of the radii of the active elements to the radius or the reflector) did not increase the pumping efficiency. Monitoring the effective lifetime of the excited particles established that the main reason for the fall in the amplifier efficiency with increasing pump energy (the greater the active element diameter, the steeper the fall) was the influence of superradiance processes. A gain M = 10³ was achieved in an amplifier excited by an INK-22 cavity flashlamp with an active element 6 mm in diameter and 300 mm long (the excited part was 200 mm long) when the ratio of the stored excitation energy to the pump energy was ~ 0.015.