A semiconductor whispering-gallery-mode laser with ring cavity operating at room temperature

Whispering gallery mode (WGM) semiconductor lasers with ring and disk cavities (outside diameters 300, 200, and 100 $\mu$m) operating in a pulsed regime at room temperature on a $\lambda$ = 2.4 $\mu$m wavelength have been created. A comparative study of the spectral and threshold characteristics of these lasers showed that ring lasers operate, like those with the disk cavities, on WGMs. The level of spontaneous emission in the ring lasers is lower by almost an order of magnitude than that in the disk lasers, which is due to the absence of recombination in the central part of the cavity. The threshold current density in ring lasers is slightly greater than that in the disk lasers, which is related to an increase in the current density at the edges of both cavities and to the appearance of surface leak currents on the inner surface of the ring-shaped cavity.