Fabricating and testing of Bragg gratings for 1060nm α-DFB lasers

摘要

In contrast to Distributed Feedback (DFB) lasers for wavelengths of about 1060nm for α-DFB lasers the fabrication of Bragg gratings using conventional wafer stepper lithography is possible, due to the necessary larger grating period. The use of a wafer stepper enables us to study especially the influence of slant angle of the fabricated gratings and stripe width on optical properties of the fabricated lasers on the same wafer independent from fluctuations of the vertical structure. Best beam quality was achieved for 15°and 13.5°tilted gratings with a small period of 594nm and 658nm respectively. For optimised structures a nearly diffraction limited beam with an output power of more than 1W, a lateral far field divergence angle of θ = 0.3° a beam quality factor M~2 = 1.1 and 3.2 at 2.1W respectively, and a line width of 5.8 pm with 28dB side mode suppression rate was achieved.