Quality-factor and nonlinear properties of optical whispering-gallery modes

The properties of optical resonators with quality-factor Q⩾10 ⁸, effective volume of e.m. field localization V_eff≈10 ^-9 cm ³ and threshold power of optical bistability W_bist≈10 ^-5 W are described. The prospects to reduce V_eff and W_bist are discussed. With possible reduction of controlling energy of optical switching down to a single quantum and employment of the monophotonic states of light, the whispering-gallery microresonators can open the way to realize Feynman's quantum-mechanical computer.