| The evanescent waves which escape from whispering gallery modes and eventually lead to emission from dielectric cavities are important for a range of applications, including microlasers, wavelength filters and detectors of biomolecules, temperature, etc. It is well known that cavities sufficiently deformed that ray dynamics show a mixture of chaotic and regular behaviour are very interesting and capable of effects such as highly directional emission. It is argued here that even slightly deformed cavities, in which the ray dynamics looks entirely regular, are both theoretically challenging and produce surprisingly directional emission. Although natural boundaries prevent a straightforward implementation of conventional ray-based methods, a combination of canonical perturbation theory and semiclassical approximation is shown to be capable of explaining observed effects. |
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