Passive Q switching of an Er:glass laser with the pulse width varying
between 14 and 80 ns has been demonstrated, using three resonator vana
dium-dioxide-coated (VO2) mirror samples with temperature-dependent re
flectivity and differing in the reflectivity contrast. The reflectivit
y changes because of a phase transition from a semiconductor to a meta
llic state. Broad band operating characteristics of VO2 mirrors provid
e Q switching over a wide range of wavelengths. In addition, mode-lock
ed pulses with much shorter time scales have been observed, due to exc
iton formation and recombination. A simple criterion is derived for th
e allowable ambient temperatures at which the Q switching operates eff
ectively, A simple relation has also been found relating the duration
of the Q-switched pulse to the contrast in reflectivities of the two m
irror phases. (C) 1995 American Institute of Physics.