High Power Narrow far-field Broad-Stripe Semiconductor Lasers with Second-Order Metal Grating Feedback

In order to obtain high power semiconductor lasers with narrow far-field and improve the characteristics of the output beam, a broad-stripe distributed feedback semiconductor laser with second-order metal surface gratings emitting around 940 nm is fabricated, based on the holographic photolithography and wet etching technology. The second-order metal gratings are located at the metal/semiconductor interface in the p-Al0.2GaIn0.49P cladding layer, with 960 mu mx142 mu m grating area, and the metal gratings also act as ohmic contact of the p side. The grating period is 287nm, the grating depth is 120 nm, and the grating duty cycle is 0.5. For the laser with second-order metal gratings, the powers is 718 mW, spectral linewidth (FWHM) is less than 0.1 nm, lateral far field angle (FWHM) is 2.7 degrees and the vertical far-field angle (FWHM) is 16.7 degrees in the current of 1.5 A. For the laser without gratings in the current of 1.5 A, the spectral linewidth is 1.3 nm, the lateral far-field angle is 7.3 degrees and the vertical far-field angle is 36 degrees, both worse than lasers with second-order metal surface gratings.