Low-temperature emission from a ruby laser with a passive switch

An investigation was made of the output characteristics recorded at –180° C for a ruby laser with a saturable filter. The initial transmission of the filter was varied from 25 to 0.03%. Giant pulses of up to 2.2 nsec duration were generated. The width of the output spectrum was about 0.05 cm^–1. Stable mode locking was obtained for transmission exceeding 1%. Fast depopulation in the presence of dense filters sometimes made it possible to select a single pulse from a mode-locked train. The duration of such a pulse was less than 0.5 nsec and the peak power was of the order of 6 GW/cm².