AMPLIFIED SPONTANEOUS EMISSION IN ELECTRON-BEAM-PUMPED SURFACE-EMITTING SEMICONDUCTOR-LASERS

The deterioration of gain in electron-beam-pumped semiconductor lasers with increase in the diameter of the pumped region has been attribute d to a reduction in the degree of inversion caused by amplified sponta neous emission. Theories of amplified spontaneous emission in such sur face-emitting lasers are advanced in which spatial and spectral inhomo geneities of gain are taken into account. Experiments to determine the dependence of laser threshold and differential efficiency on the diam eter of an excited circular region demonstrate good agreement with the threshold predictions of the linear theory; however, the lack of agre ement in differential efficiency suggest that a nonlinear phenomenolog ical theory be considered. Data for such calculations are provided fro m experiments on saturation of spontaneous emission. The resultant non linear theory is shown to account well for the observed dependence of differential efficiency on the diameter of the excited region.