Cavity quantum electrodynamic enhancement of stimulated emission in microdroplets.

Cavity-QED-enhanced stimulated visible emission was observed in 14-\ensuremath{\mu}m-diam rhodamine-6G--ethanol droplets pumped by cw 514.5-nm radiation. Use of droplets provides an excellent test of cavity QED theory for spherical geometries. The mode number and order of the spherical-cavity resonances responsible for the observed emission peaks were identified and their Q values calculated from Lorenz-Mie theory. By equating stimulated gain to calculated/measured cavity losses, it was determined that spherical-cavity Q's of only ${10}^{3--}$${10}^{4}$ lead to cavity QED enhancements in excess of 120 in the emission cross section of rhodamine 6G, consistent with theory.