Dual-carrier Floquet circulator with time-modulated optical resonators

TL;DR

This paper proposes a novel Floquet circulator using time-modulated optical resonators, achieving broadband, frequency-independent nonreciprocal transmission at a wavelength scale without relying on traditional symmetry constraints.

Contribution

It introduces a new Floquet circulator design leveraging time-modulated resonators and sideband-selective waveguides for broadband, miniaturized nonreciprocal optical devices.

Findings

Supports broadband nonreciprocal transmission

Achieves frequency-independent forward transmission

Enables wavelength-scale circulators

Abstract

Spatio-temporal modulation has shown great promise as a strong time-reversal symmetry breaking mechanism that enables integrated nonreciprocal devices and topological materials at optical frequencies. However, optical modulation has its own constraints in terms of modulation index and frequency, which limit the bandwidth and miniaturization of circulators and isolators, not unlike the magneto-optical schemes that it promises to replace. Here we propose and numerically demonstrate a Floquet circulator that leverages the untapped degrees of freedom unique to time-modulated resonators. Excited by sideband-selective waveguides, the system supports broadband nonreciprocal transmission without relying on the mirror or rotational symmetries required in conventional circulators. Cascading two resonators, we create a linear three-port circulator that exhibits complete and frequency-independent forward transmission between two of the ports. This approach enables wavelength-scale circulators that can rely on a variety of modulation mechanisms.