Rotation-induced Mode Coupling in Open Wavelength-scale Microcavities

TL;DR

This paper investigates how rotation and openness influence mode coupling in wavelength-scale microcavities, revealing complex behaviors like decay rate crossing, phase locking, and non-monotonic Sagnac effects, which are crucial for understanding microcavity dynamics.

Contribution

It introduces the concept of rotation-induced mode coupling in open microcavities and analyzes its effects on resonance behaviors and decay rates, highlighting the role of openness.

Findings

Decay rates of quasi-degenerate modes can cross or anti-cross with rotation.

Standing-wave resonances evolve into traveling-wave resonances at high rotation speeds.

Both CW and CCW traveling-wave resonances can have lower decay rates, contrary to expectations.

Abstract

We study the interplay between rotation and openness for mode coupling in wavelength-scale microcavities. In cavities deformed from a circular disk, the decay rates of a quasi-degenerate pair of resonances may cross or anti-cross with increasing rotation speed. The standing-wave resonances evolve to traveling-wave resonances at high rotation speed, however, both the clockwise (CW) and counter-clockwise (CCW) traveling-wave resonances can have a lower cavity decay rate, in contrary to the intuitive expectation from rotation-dependent effective index. With increasing rotation speed, a phase locking between the CW and CCW wave components in a resonance takes place. These phenomena result from the rotation-induced mode coupling, which is strongly influenced by the openness of the microcavity. The possibility of a non-monotonic Sagnac effect is also discussed.