Injection-Laser Far-Field Patterns with Gaussian Profiles in the Junction Plane

Far-field patterns from GaAs junction lasers with stripe contacts about 13 μ wide have been studied. At room temperature, more than 80% of the diodes have approximately Gaussian intensity profiles along the junction plane. Intensity measurements show that the profiles are stable for currents exceeding threshold by 60% in some diodes. These experimental results indicate that the lasers oscillate predominantly in the lowest-order mode. Previously, with 50 μ stripe widths it was impossible to predetermine the dominant mode or to insure its stability for current variations greater than about 5%. In contrast to the symmetric behavior along the junction plane the radiation patterns perpendicular to the plane are asymmetric. Infrared photographs show a major lobe along with several minor lobes, the latter always appearing on the n side of the junction plane. The main features of the asymmetry are essentially the same for similarly fabricated diodes. Differences are found in the intensity distributions or widths of the minor lobes.