TRANSITION METAL-DOPED ZINC CHALCOGENIDES - SPECTROSCOPY AND LASER DEMONSTRATION OF A NEW CLASS OF GAIN MEDIA

The absorption and emission properties of transition metal (TM)-doped zinc chalcogenides have been investigated to understand their potentia l application as room-temperature, midinfrared tunable laser media, Cr ystals of ZnS, ZnSe, and ZnTe, individually doped with Cr2+, Co2+, Ni2 +, or Fe,(2+) have been evaluated, The absorption and emission propert ies are presented and discussed in terms of the energy levels from whi ch they arise. The absorption spectra of the crystals studied exhibit strong bands between 1.4 and 2.0 mu m which overlap with the output of strained-layer InGaAs diodes. The room-temperature emission spectra r eveal wide-band emissions from 2-3 mu m for Cr and from 2.8-4.0 mu m f or Co. Cr luminesces strongly at room temperature; Co exhibits signifi cant losses from nonradiative decay at temperatures above 200 K, and N i and Fe only luminesce at low temperatures, Cr2+ is estimated to have the highest quantum yield at room temperature among the media investi gated with values of similar to 75-100%. Laser demonstrations of Cr:Zn S and Cr:ZnSe have been performed in a laser-pumped laser cavity with a Co:MgF2 pump laser, The output of both lasers were determined to pea k at wavelengths near 2.35 mu m, and both lasers demonstrated a maximu m slope efficiency of approximately 20%, Based on these initial result s, the Cr2+ ion is predicted to be a highly favorable laser ion for th e mid-IR when doped into the zinc chalogenides; Co2+ may also serve us efully, but laser demonstrations yet remain to be performed.