Steady-state ultrashort pulses generated by passive mode locking of a solid-state laser with an active feedback

Reproducible generation of steady-state ultrashort pulses (of ~7.4 psec duration) was achieved for the first time in a pulsed ruby laser with passive mode locking. The lasing was stabilized by a slow-response negative feedback established by an electrooptic switch. An experimental study was made of the formation of steady-state ultrashort pulses from initial radiation fluctuations. The proposed method should be suitable for the generation of reproducible pulses of ~100 fsec duration in wide-band amplifying media.