Analysis of spatial modes in half-disk lasers based on AlGaAsSb/InGaAsSb quantum well nanoheterostructures

Spectral and spatial distributions of the emission of whispering-gallery-mode (WGM) lasers with a half-disk cavity have been studied. Up to 13 broad lobes with different intensities, subdivided into order-of-magnitude narrower lobes, are distinguished in the spatial distribution. The emission spectrum is nearly single-mode. A mathematical model of the electromagnetic field distribution in a WGM laser is suggested, and the radiation pattern of the laser is calculated. It is shown that each lobe corresponds to its own stable radial spatial mode. The highest emission intensity is provided not by the peripheral mode itself, but by the next-closest mode, which presumably exhibits the lowest optical loss. The predominance of a single spatial mode results in a nearly single-mode emission spectrum being observed.