Chaotic Light: a Theory of Asymmetric Resonant Cavities

Spherical and cylindrical dielectric cavities support high Q whispering gallery modes due to total internal reflection of the trapped light. When such a cavity is deformed smoothly the ray dynamics of these modes becomes chaotic in a manner determined by the KAM theory of classical hamiltonian dynamics. The universal properties of the ray dynamics predicted by KAM theory allow a general understanding of the whispering gallery modes of such asymmetric resonant cavities (ARCs). This theory combined with simulations of the non-linear map describing the ray motion provides the basis for a ray-optics model of the Q-spoiling of these whispering gallery modes for large deformations (greater than 1% of the radius). The model predicts a sharp onset as a function of deformation for significant Q-spoiling of these modes and highly directional emission above this threshold. Solution of the wave equation for typical whispering gallery modes confirms the qualitative behavior predicted by the ray-optics model even when the cavity is only a few times the resonant wavelength. The model explains for the first time the lasing intensity profile of highly deformed lasing droplets. Current address: Department of Physics, University of Oregon, 1371 E 13th Avenue, Eugene, OR 97403 2 Published in Optical Processes in Microcavities, edited by R.K.Chang and A.J.Campillo (World Scientific Publishers, 1996)