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 μm×142 μm 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° and the vertical far-field angle (FWHM) is 16.7° 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° and the vertical far-field angle is 36°, both worse than lasers with second-order metal surface gratings.