Free-space coupling enhancement of micro-resonators via self-accelerating beams

We study free-space coupling of optical fields to the whispering-gallery-mode resonators by employing self-accelerating beams orbiting a semicircle. The best coupling condition is obtained through theoretical analysis, in accord with the numerical results. Comparing with the conventional Gaussian-like beams, much enhanced coupling efficiency is achieved with such self-accelerating beams, particularly when a large numerical aperture of an optical system is used or a higher-order azimuthal mode is considered. Conditions with slight deviation from the ideal radius of self-accelerating beams are further discussed, aiming to realize an optimized high coupling efficiency.