Abnormal high-$Q$ modes of coupled stadium-shaped microcavities

TL;DR

This paper demonstrates that coupling two chaotic stadium-shaped microcavities can produce abnormal high-Q modes, significantly enhancing the quality factor through specific mode patterns that minimize light leakage.

Contribution

It reveals how coupling and geometry can create high-Q modes in chaotic microcavities, a novel approach to controlling optical confinement.

Findings

Coupled stadium-shaped microcavities support modes with Q factors about 10 times higher than single cavities.

The high-Q modes follow a whispering-gallery-like pattern at the cavity ends.

Mode patterns minimize light leakage, enhancing cavity performance.

Abstract

It is well known that the strongly deformed microcavity with fully chaotic ray dynamics cannot support high-Q modes due to its fast chaotic diffusion to the critical line of refractive emission. Here, we investigate how the Q factor is modified when two chaotic cavities are coupled, and show that some modes, whose Q factor is about 10 times higher than that of the corresponding single cavity, can exist. These abnormal high-Q modes are the result of an optimal combination of coupling and cavity geometry. As an example, in the coupled stadium-shaped microcavities, the mode pattern extends over both cavities such that it follows a whispering-gallery-type mode at both ends, whereas a big coupling spot forms at the closest contact of the two microcavities. The pattern of such a 'rounded bow tie' mode allows the mode to have a high-Q factor. This mode pattern minimizes the leakage of light at both ends of the microcavities as the pattern at both ends is similar to whispering gallery mode.