  The life times of optical modes in whispering-gallery cavities crucially
depend on the underlying classical ray dynamics and may be spoiled by the
presence of classical nonlinear resonances due to resonance--assisted
tunneling. Here we present an intuitive semiclassical picture which allows for
an accurate prediction of decay rates of optical modes in systems with a mixed
phase space. We also extend the perturbative description from near-integrable
systems to systems with a mixed phase space and find equally good agreement.
Both approaches are based on the approximation of the actual ray dynamics by an
integrable Hamiltonian, which enables us to perform a semiclassical
quantization of the system and to introduce a ray-based description of the
decay of optical modes. The coupling between them is determined either
perturbatively or semiclassically in terms of complex paths.
