Creating disk-shaped cavity with a vertical side surface for an infrared whispering-gallery-mode laser ($\lambda$ $\approx$ 3 $\mu$m)

Disk-shaped cavities in the form of cylinders with diameters of 200, 100, and 50 $\mu$m and a mesa height of up to 30 m with the vertical part of the side surface reaching 10 m have been created for the first time for whispering gallery mode (WGM) semiconductor lasers based on InAs/InAsSb$_{0.11}$P$_{0.24}$ heterostructures. The cavities were formed by etching in a specially selected HBr/H$_2$Cr$_2$O$_7$/H$_3$PO$_4$ mixture, which ensured an increase in the length of the vertical part of the side surface at a decrease in the surface roughness. These improvements increased the stability of optical modes in the disk cavity of the WGM laser and ensured generation with a wavelength of $\lambda$ $\approx$ 3 $\mu$m in a continuous regime at 77 K.