Off-axial oscillation modes in longitudinally pumped semiconductor lasers

A semiclassical approximation is used in a calculation of the distributions of the fields and excitation thresholds of transverse modes generated in semiconductor lasers pumped longitudinally by an electron beam. Calculation allows for the effects associated with the influence of a thermal lens and with an inhomogeneity of the spatial distribution of the gain. It is shown that an increase in the pumping rate alters the mechanism of field localization: near the lasing threshold the properties of off-axial oscillation modes are governed by the focusing effect of the thermal lens, whereas at higher excitation rates they are determined by the nature of the spatial distribution of the gain in the active medium. The calculated results are compared with the experiments.