Semiconductor laser with a distributed feedback

Stimulated emission was obtained from an optically pumped gallium arsenide laser with a distributed feedback. The feedback was produced by a diffraction grating formed on the surface of a p –type GaAs layer prepared by the diffusion of zinc into an n –type substrate. The grating was in optical contact with the active layer and its period satisfied the Bragg condition for a guided mode within the gain band of the laser. For the selected Bragg scattering order, the radiation was extracted at right angles to the grating surface. The far-field distribution consisted of a single lobe with a divergence of 5–20', which corresponded to the emission from one to five randomly distributed modes whose frequencies depended on the position of the excited region in the laser.