Fabrication issues and considerations for high performance grating-surface-emitting semiconductor lasers

Abstract

A sketch of a grating-surface-emitting (GSE) laser is shown. The gratings between the gain sections provide feedback for laser oscillation in second order and couple out the laser radiation perpendicular to the surface in both directions in first order. With proper choice of grating parameters, a portion of the light is passed completely through each grating section and serves to injection lock additional gain sections in the longitudinal direction. GSE laser array technology has experienced steady progress over the last two years. Improvements in material quality and uniformity have made it possible to coherently couple two dimensional GSE lasers over distances larger than 1 cm. Figure 2a shows a peak output of 32 W per surface with differential quantum efficiencies of 40 % per surface during pulsed operation. The same device provides a continuous power output of 3.4 W per surface, as shown in Fig. 2b. Variations on the basic GSE laser concept have resulted in Master Oscillator Power Amplifier (MOPA) GSE arrays and continuous grating (CG)-GSE laser arrays. GSE arrays with 10 elements per gain section and 20 gain sections have obtained cw threshold current densities of under 140 A/cm2 with cw differential quantum efficiencies of 20 to 30%more » per surface. Linewidths in the 40 to 100 MHz range have been obtained with output powers of 100 to 250 mW/surface.« less