Abstract

Tapered semiconductor amplifiers have successfully demonstrated efficient high-power diffraction-limited emission.^1-4 In order to get good performance, it is mandatory to reduce the possibility of oscillation in directions competing with the main axis of amplification. So far, two approaches have been used to achieve this. One approach involved making a pair of etched grooves through the whole epi layer at the narrow end of the tapered amplifier.^1,3,4 A second approach relied on proton implantation to make the surrounding regions very absorbing.² In this work, a novel approach to this problem is demonstrated. A self-aligned dissipating grid is fabricated on the unpumped region and is demonstrated to efficiently prevent oscillation in both longitudinal and lateral directions. 0.5 W pulsed diffraction-limited emission from a 1-mm-long tapered amplifier is achieved with a slope efficiency of 0.68 W/A at a bias current of 1 A. The central lobe contains over 85% of the total emitted power. The advantages of our approach include (1) a simple photolithographic step which do not involve implantation, (2) elimination of the alignment difficulty associated with centering the grooves with the index-guided gain region, and (3) a potential improvement in reliability since deeply etched grooves are not required. This approach can also be applied to broad-area amplifiers.

© 1994 Optical Society of America