Active mode locking of a microwave-pumped XeCl laser

A method for subnanosecond pulse generation in a long-pulse microwave-pumped XeCl laser using an acoustooptic modulator is demonstrated. A 32 cm long discharge region, confined in a 1 mm ID quartz tube, is excited by 450 kW, 3.5 microsec long pulses at 9.375 GHz, at a repetition rate of 10 Hz. It is shown that the mode-locked pulse width in the transient mode locking regime is dependent on the number of cavity roundtrips made by the developing pulse. The data indicate that the acoustooptic modulator has sufficient gain duration and modulation depth to produce high contrast mode locking with equivalent 300 ps pulse lengths, and that longer gain times from improved lasers should result in shorter pulses.