Generation of high power ultrashort pulses in a lowtemperature ruby laser with a small active volume

A short train of up to three pulses with an energy of 1 J was obtained from a ruby laser operating at a low (100°K) temperature and consisting of a mode-locked oscillator and three amplifiers with an overall active length of 48 cm. The signal was amplified coherently, the pulse duration being shortened to 5–10 psec. The product of the spectral width and pulse duration (measured at half-height) was 0.2–0.8. The pulse duration was mesured using a large-aperture shutter with a saturable filter. An echelette was used to scatter the light so as to increase the overall transmission of the shutter.