Asymmetric Al-free active region laser structure for high-brightness tapered lasers at 975 nm

摘要

We have realized an asymmetric laser structure at 975 nm, based on an Al-free active region. The quantum wells are located near the p-cladding, so that most of the waveguide is n-type, which allows for reduced optical losses and series resistance. On uncoated broad-area lasers, we have obtained very low optical losses of 0.4 cm~(-1), together with a high internal quantum efficiency of close to 100%. Based on this structure, we have realized index-guided tapered lasers delivering 1.3W CW, with a narrow far-field angle of 2.5° (FWHM) and 5.8° (at 1/e~2) in the slow axis, and a good beam propagation ratio M~2 = 1.6. The lasers reach a high maximum wall-plug efficiency of 56%. These tapered lasers deliver a maximum power of 1.5W CW with M~2 < 3. The results on the asymmetric structure are compared with those of a symmetric laser structure.