Active mode locking of a high pressure CW waveguide CO2 laser

A technique for active mode locking of lasers is proposed and evaluated experimentally. The experimental apparatus which consists of a CO2 waveguide amplifier, an output mirror, and an acoustic optical modulator is described. The technique has an acoustooptical frequency shifter set up in the cavity of a homogeneously pressure broadened CO2 waveguide laser making it possible to couple the laser cavity to two secondary cavities. A train of pulses and a frequency spectrum of the train of pulses obtained with this technique are presented and analyzed. It is noted that when this apparatus is properly adjusted it generates new waves and frequencies which correspond to the longitudinal laser modes leading to short-pulse synthesis; FWHM pulses as short as 2 ns have been obtained and with adjustment of the configuration of the cavities subns pulses are possible.