High-power, high-brightness Al-free active region tapered lasers at 915 nm

摘要

To achieve high power and high brightness, we have developed tapered diode lasers based on an Al-free active region at 915 nm. The material structure was grown by MOCVD (Metallorganic Chemical Vapor Deposition). It shows very low internal losses of only 0.5 cm~(-1), a very low transparency current density of 86 A/cm~2, an excellent internal quantum efficiency of 86%, and a high characteristic temperature T_0 of 171 K. Based on these good results, at first, we have realised index-guided tapered lasers (IG1) with a narrow output width and a narrow taper angle, which deliver 1 W CW, together with an M~2 beam quality parameter of 2.9 at 1/e~2, and a narrow divergence angle in the slow axis of 5.1° FWHM and 7.5° at 1/e~2. We have also fabricated new index-guided tapered lasers with a Clarinet shape, which were recently proposed to achieve high brightness together with a very narrow divergence angle. The Clarinet lasers deliver 0.6W CW, together with an excellent M~2 beam quality factor of 1.2 at 1/e~2, and a very narrow divergence angle in the slow axis of only 2.5° FWHM, and 3.9° at 1/e~2, which is stable with current. These very narrow divergences are very advantageous for the collective coupling of tapered bars into optical fibers. In this work we have also investigated the influence of taper length on the output power and beam quality.