| Dynamical tunneling is a transport process between regular and chaotic regions in a mixed phase space. Such transport is strictly forbidden in classical mechanics, but allowed in wave mechanics. Dynamical tunneling is of great current interest and has been studied intensively in various physical systems. But there is no direct experimental evidence of dynamical tunneling in optical microcavities, reflecting the experimental difficulty of probing such internal processes from the outside. By employing excitation spectroscopy, we experimentally investigated the dynamical tunneling phenomena in details in a quadrupole-deformed microcavity laser. We obtained both pump-coupling efficiency as high as 50% and an effective coupling constant responsible for the dynamical tunneling from the observed pumping efficiency by using the mode-mode coupling model. As a result, the lasing threshold could be lowered by two orders of magnitude due to the dynamical tunneling from that of the nonresonant pumping based on ray chaos. |
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