Extreme output sensitivity to subwavelength boundary deformation in microcavities
Li Ge, Qinghai Song, Brandon Redding, and Hui Cao
Accepted
We demonstrate a generic and robust mechanism that leads to an extreme output sensitivity to a deep subwavelength boundary perturbation in wavelength-scale microcavities. A deformation of the cavity boundary on the order of ten thousandth of a wavelength may flip the output directions by 180, corresponding to a variation of 0.1nm for a 1mm-radius cavity. Our analysis based on a perturbation theory reveals that such tiny structural change can cause a strong mixing of nearly degenerate cavity resonances with different angular momenta, and their interference is greatly enhanced to have a radical influence on the far-field pattern. Our finding opens the possibility of utilizing carefully-designed wavelength-scale microcavities for fast beam steering and high-resolution detection.