Abnormal high-Q modes of coupled stadium-shaped microcavities

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 the whispering gallery mode.

Hybrid Microcavity Lasers: Principle, Design, and Practical Application

“…[20][21][22][23][24][25] Since the beginning of the revolution in optical microcavities, there have been a vast number of cavities, e.g., Fabry-Perot interferometers (F-P), [26][27][28][29][30] DOI: 10.1002/lpor.202300343 distributed Bragg reflectors (DFB), [31][32][33][34][35][36] distributed Bragg reflection (DBR) cavities, [37][38][39][40] whispering gallery mode (WGM) resonators, [41][42][43][44][45][46][47][48] scattering system (SS), [49][50][51][52][53] and deformation cavities. [54][55][56][57] These specific geometries endow these microcavities with, respectively, distinct lasing emission features in frequency, direction, mode, time, or angular momentum.…”