PASSIVE-Q SWITCHING AND MODE-LOCKING OF ER-GLASS LASERS USING VO2 MIRRORS

Passive Q switching of an Er:glass laser with the pulse width varying between 14 and 80 ns has been demonstrated, using three resonator vanadium-dioxide-coated (VO2) mirror samples with temperature-dependent reflectivity and differing in the reflectivity contrast. The reflectivity changes because of a phase transition from a semiconductor to a metallic state. Broad band operating characteristics of VO2 mirrors provide Q switching over a wide range of wavelengths. In addition, mode-locked pulses with much shorter time scales have been observed, due to exciton formation and recombination. A simple criterion is derived for the allowable ambient temperatures at which the Q switching operates effectively, A simple relation has also been found relating the duration of the Q-switched pulse to the contrast in reflectivities of the two mirror phases. (C) 1995 American Institute of Physics.