PassiveQswitching 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 VO2mirrors provideQswitching 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 theQswitching operates effectively. A simple relation has also been found relating the duration of theQ‐switched pulse to the contrast in reflectivities of the two mirror phases. ©1995 American Institute of Physics.