Non-integer optical modes in a M\"obius-ring resonator

TL;DR

This paper demonstrates that in a M"obius-ring resonator, the geometric phase causes resonances with a fractional number of wavelengths, revealing topologically robust optical modes with potential fault-tolerance.

Contribution

It introduces the concept of non-integer optical modes in M"obius-ring resonators driven by topological geometric phases, a novel phenomenon in optical physics.

Findings

Fractional optical modes occur due to geometric phase variations.

Topological robustness of the geometric phase enhances fault-tolerance.

Continuous variation of the phase with light ellipticity influences resonance conditions.

Abstract

In-plane polarized light experiences a non-trivial topological evolution as it propagates resonantly in a M\"obius ring resonator. The resultant geometric phase varies continuously when changing the light ellipticity, which leads to constructive interference for a non-integer number of wavelengths, and therefore to the occurrence of an arbitrary fractional number of optical modes. The geometric phase in M\"obius-ring resonators is topologically robust and implies excellent intrinsic fault-tolerance.