Ultraviolet ZnS semiconductor laser pumped longitudinally by an electron beam

A semiconductor (ZnS) was examined experimentally in a longitudinally pumped laser. The materials were high resistivity single crystal ZnS plates with alternating hexagonal and cubic phases. Laser screens were prepared by mirror-coating the semiconductor plates on both sides and fastening them to sapphire disks. Cathodoluminescence data were taken on the ZnS plates, revealing a low interband luminescence yield. Edge luminescences of 343 and 335 nm were observed, together with electron radiative recombination lines at 370 and 430-440 nm. High temperature annealing in liquid Zn for 70-100 hr and electron beam excitation produced lasing in the hexagonal phase at 330 nm with an 1.5 nm width. Annealing in sulfur vapor inhibited lasing. It was concluded that the nonequilibrium carrier density is augmented by greater fractions of the hexagonal phase, thus allowing for lower excitation rates due to recombination in a degenerate nonequilibrium electron-hole plasma.