Spatial Distribution of Radiation from GaAs Lasers

The spatial distribution of the energy emitted by GaAs lasers having Fabry-Perot resonators was investigated. In general, the diodes emit several fan-shaped beams of comparable magnitude at angles up to 10° with respect to the normal of the mirrors in the junction plane. These beams have widths from ¾° to several degrees in the plane of the junction and about 10° in the plane perpendicular to the junction. The radiation patterns are usually asymmetric about the normal to the polished faces of the diode and this asymmetry is mirrored on the opposite side of the diode. We conclude that because our Fabry-Perot mirrors are not perfectly parallel, the most prevalent modes of our diodes illuminate the radiating surface with phase and intensity distributions which vary strongly along the junction. This variation is frequently nearly periodic.