We report a quantum ringlike toroidal cavity naturally formed in a vertical
-cavity-like active microdisk plane due to Rayleigh's band of whispering ga
llery modes. The root T-dependent redshift and a square-law property of mic
roampere-range threshold currents down to 2 mu A are consistent with a phot
onic quantum wire view, due to whispering gallery mode-induced dimensional
reduction. [S0031-9007(98)08230-1].