Photons and polaritons in a time-reversal-broken non-planar resonator

TL;DR

This paper demonstrates a novel low-loss, time-reversal symmetry-breaking optical resonator using non-planar geometry and atomic Faraday rotation, achieving significant optical isolation and enabling advanced photonic materials and devices.

Contribution

It introduces a new method for breaking time-reversal symmetry in optical resonators via non-planarity and atomic Faraday rotation, with experimental validation and potential applications.

Findings

Achieved 20.1 dB optical isolation.

Observed 6.3 linewidth splitting between modes.

Demonstrated impact on Rydberg polaritons and topological photonics.

Abstract

From generation of backscatter-free transmission lines, to optical isolators, to chiral Hamiltonian dynamics, breaking time-reversal symmetry is a key tool for development of next-generation photonic devices and materials. Of particular importance is the development of time-reversal-broken devices in the low-loss regime, where they can be harnessed for quantum materials and information processors. In this work, we experimentally demonstrate the isolation of a single, time-reversal broken running-wave mode of a moderate-finesse optical resonator. Non-planarity of the optical path produces a round-trip geometrical (Pancharatnam) polarization rotation, breaking the inversion symmetry of the photonic modes. The residual time-reversal symmetry between forward-$\sigma^+$/ backwards-$\sigma^-$ modes is broken through an atomic Faraday rotation induced by an optically pumped ensemble of $^{87}$Rb atoms residing in the resonator. We observe a splitting of 6.3 linewidths between time-reversal partners and a corresponding optical isolation of $\sim$ 20.1(4) dB, with 83(1)% relative forward cavity transmission. Finally, we explore the impact of twisted resonators on T-breaking of intra-cavity Rydberg polaritons, a crucial ingredient of photonic materials and specifically topological optical matter. As a highly coherent approach to time-reversal breaking, this work will find immediate application in creation of photonic materials and also in switchable narrow-band optical isolators.