Reduction of GaAs diode laser spontaneous emission

Abstract

Spontaneous emission from GaAs lasers is substantially reduced by fabricating a high‐reflection dielectric stack coating for the rear facet and apertured coatings of highly absorbing Te for the front (output) facet. After deposition the Te is ablated by the laser mode itself and the aperture is stabilized by Al₂O₃ overcoating. The stimulated emission at mode center passes through the aperture unattenuated, whereas the spontaneous emission at the edges of the mode is strongly absorbed. Since spontaneous emission at mode center saturates above threshold we estimate that the ratio of stimulated to spontaneous power will approach 100 at near‐10‐mW output levels.