Thin-film /spl lambda//spl sim/3.7 /spl mu/m 'W' laser released from InAs substrate

A mid-infrared type-II 'W' laser fabricated by releasing the epitaxial film from its original InAs substrate is reported. The process exploits the extreme selectivity between GaSb and InAs when etched by hydrochloric acid. The detached film is coated with an Si/sub 3/N/sub 4/ optical cladding layer, grafted to a foreign GaAs substrate, and cleaved into laser bars. For epitaxial-side-up mounting, the device operates to 70 K, with a low threshold (/spl sime/150 W/cm/sup 2/) when pumped with the maximum available CW power of 320 mW from a 980 nm laser diode.