Improve the Performance of Integrated Diode Laser Beam Combining Through Grating Regrowth.

摘要

This project aims to improve the output power and coherence of monolithically combined broad-area diode lasers through grating regrowth. We have recently demonstrated coherent beam combining in a new, completely integrated approach to edge-emitting semiconductor lasers. Modal control has been achieved through angled transverse Bragg grating approach that creates 100 micron wide lasers with a single mode, and two such lasers have been combined (through two dimensional Bragg diffraction) in a "V" pattern to create a diffraction-limited beam. The coherence has been verified via double slit interference pattern created at the "V" side where the two separate lasers emit. The output power of the demonstrated lasers is currently limited by the deeply etched (1.2 um) surface gratings. We propose to create the grating near the active region so that the grating depth could be reduced to about 50nm. After the grating is etched, the P waveguide/cladding/contact layers will be re-grown on top of the grating. This regrowth process will greatly reduce the scattering loss and surface defects induced by the grating and result in uniform current injection, which will ultimately improve the performance of coherently combined broad area lasers.