9B6 - Measurements of gain perpendicular to the junction in gallium arsenide laser structures

Gain measurements are reported for radiation of wavelength 8466Å propagating in a direction perpendicular to the junction of a GaAs injection laser operated at 80°K. These results, used in conjunction with measurements of spontaneous emission, show that a gain of 2.3 percent is achieved at 7000 A/cm². In thermal equilibrium, neglecting free carrier absorption, 0.78 percent of the transmitted radiation is absorbed in traversing the active region, 135 A/cm²being required to offset this loss. Allowance for free carrier absorption changes the above figures somewhat. The separation of the quasi-Fermi levels is also deduced from this data.