Selection mechanisms of transverse modes in semiconductor injection lasers

A discussion of the transverse mode selection in the conventional double-heterostructure injection lasers is given. The mechanisms considered as responsible for mode selection are 1) the nonnormal incidence in the plane perpendicular to the junction of the EM waves at the end faces; and 2) an uneven gain distribution across the active region. By using a multilayer waveguide model, results are presented that show the regions of preference of each of the modes as determined by each mechanism both in isolation and simultaneously. Hence, the regions of dominance of each mechanism are determined.