Very Short Far Infrared Pulses from Optically Pumped CH3OH/D, Chooh and CH3F Lasers using an Eq-Switched CO2 Laser as a Pump Source

This paper describes the generation of far infrared pulses with a risetime of 10⁻⁸s from optically pumped CH3OH/D, CHOOH and CH3F lasers using a Q-switched current pulsed CO2 laser as a pump source. The pump source consists of a conventional tunable low pressure (20 Torr) CO2 laser which is Q-switched by a rotating mirror mounted on an air-driven spindle. Discharge current pulses up to 200 mA and 100-300 μs duration are produced and synchronized to the Q-switch by a trigger pulse from the rotating mirror. Due to the high discharge current, output powers are increased by at least a factor 5 with respect to Q-switched pulses from a d.c. current mode (20 mA). This leads to kW peak power pulses even at transitions such as 9P38, 9P6 and 9R6 which are especially important for pumping CH3OH and CH3OD. The pump pulses are focussed by an f = 50 cm mirror onto the 1 mm incoupling hole of the FIR cavity, which consists of a 1 m long 13 mm diameter quartz tube and two 25 mm diameter flat mirrors.