Single-mode 2.4um InGaAsSb/AlGaAsSb distributed feedback lasers for gas sensing

Single-mode laser diodes on GaSb substrates were developed using InGaAsSb/AlGaAsSb triple quantum well active regions grown by molecular beam epitaxy. The devices were fabricated using lateral Cr gratings, with a grating pitch designed to coincide with a strong absorption feature of HF gas, deposited adjacent to a dry-etched narrow ridge waveguide. High sidemode suppression was achieved, and in 20 degrees C continuous-wave operation, devices with a 400 mu m-long cavity provided 4.5mW total output power at the 2396nm target wavelength. Anti-reflection and high-reflection facet coatings exhibited no deleterious effects on the laser tunability or mode quality, thus allowing the preferential extraction of output power from a single laser facet.