Abstract: There is provided by this invention a laser cavity for producing a periodic output pulse and a passive Q-switch for use therein. The laser cavity is typically comprised of a lasing medium, a pair of reflecting elements, and a passive Q-switch. The Q-switch is composed of inorganic, solid-state materials which do not degrade through use. Exemplary materials include a Q-switch constructed from a host material having a tetrahedral site, such as GSAG (Gd.sub.3 Sc.sub.2 Al.sub.3 O.sub.12), GIGG (Gd.sub.3 In.sub.2 Ga.sub.3 O.sub.12), YAG (Y.sub.3 Al.sub.5 O.sub.12), or Mg.sub.2 SiO.sub.4 into which tetravalent chromium (Cr.sup.4+) is introduced as a dopant material. The passive Q-switch composed of such materials effectively modulates laser output having a wavelength within the range of 850 nanometers to 1250 nanometers.