CR2-DOPED ZINC CHALCOGENIDES AS EFFICIENT, WIDELY TUNABLE MIDINFRAREDLASERS()

Transition-metal-doped zinc chalcogenide crystals have recently been i nvestigated as potential mid-infrared lasers. Tetrahedrally coordinate d Cr2+ ions are especially attractive as lasants on account of high lu minescence quantum yields for emission in the 2000-3000-nm range. Radi ative lifetimes and emission cross sections of the upper (5)E state ar e respectively similar to 10 mu s and similar to 10(-18) cm(2). The as sociated absorption band peaked at similar to 1800 nm enables laser-di ode pumping of the Cr2+ systems. Laser demonstrations with ZnS:Cr and ZnSe:Cr (using a MgF2:Co2+ laser pump source) gave slope efficiencies up to 30%. Excited-state-absorption losses appear small, and passive l osses dominate at present, Tuning experiments with a diffraction grati ng produce a tuning range covering at least 2150-2800 nm. Laser crysta ls can be produced by Bridgman growth, seeded physical vapor transport , or diffusion doping, Zinc chalcogenide thermomechanical properties o f interest for medium-to-high-power operation compare favorably with t hose of other host materials, except for the larger refractive-index d erivative dn/dT.