Rayleigh scattering in high-Q microspheres

The Rayleigh scattering has to be largely suppressed in high-Q whispering-g allery modes in microspheres because of restrictions imposed on scattering angles by cavity confinement. Earlier estimates of the fundamental limit fo r the quality factor in fused-silica microspheres are revisited, and Q simi lar or equal to 10(12) is predicted in few-millimeter-size fused-silica sph eres, if the surface hydration problem is ovecome. Particular effects of su rface scattering losses are analyzed, and the manifestation of scattering i n the form of intermode coupling is calculated. The predominant effect of c ounterpropagating mode coupling (intracavity backscattering) is analyzed in the presence of a mode-matched traveling-wave coupler. As much as 100% res onance reflection regime is shown to be feasible. (C) 2000 Optical Society of America.