Grazing-incidence-slab semiconductor laser (GRISSL) - art. no. 69090T

We report on a novel geometry for electrically driven semiconductor lasers called the GRISSL. The laser cavity is formed between two mirrors that are external to the semiconductor chip and the laser beam intercepts the quantum well QW) gain region at a grazing angle-of-incidence. In this first demonstration of the GRISSL, the laser structure was grown on an n-type GaAs substrate and the gain region comprises three InGaAs QWs. The external cavity consists of a pair of lenses, a flat high-reflectivity mirror, and a flat R = 70% out ut coupler. Lasers emit a power of 30 mW CW in a single- mode, 35-mu m-diameter beam at lambda similar to 0.98 mu m. Under pulsed conditions (1 mu sec, 1 kHz), a peak output power of 0.37 W was measured. The beam is single-mode near threshold but becomes multi-mode at the maximum drive currents. The slope efficiency of these devices is about 10 times lower than the design value of 1 W/A. This discrepancy can be accounted for by higher than anticipated losses in the substrate and a poor overlap of the laser beam with the pumped region. Methods for overcoming both of these factors to regain a high wall-plug efficiency are discussed.