Dynamical tunneling-assisted coupling of high-Q deformed microcavities using a free-space beam

We investigate the efficient free-space excitation of high-Q resonance modes in deformed microcavities via dynamical tunneling-assisted coupling. A quantum scattering theory is employed to study the free-space transmission properties, and it is found that the transmission includes the contribution from (1) the off-resonance background and (2) the on-resonance modulation, corresponding to the absence and presence of high-Q modes, respectively. The theory predicts asymmetric Fano-like resonances around high-Q modes in background transmission spectra, which are in good agreement with our recent experimental results. Dynamical tunneling across Kolmogorov-Arnold-Moser tori is further studied, which plays an essential role in the Fano-like resonance. This efficient free-space coupling holds potential advantages in simplifying experimental condition and exciting high-Q modes in higher-index-material microcavities.