Nonreciprocal Cavities and the Time-Bandwidth Limit

TL;DR

This paper investigates whether nonreciprocal cavities can surpass the fundamental time-bandwidth limit, concluding they do not offer advantages in this regard but may have other benefits for nanophotonics.

Contribution

The study derives general relations for nonreciprocal cavities based on microscopic reversibility, clarifying their limitations and potential in photonic systems.

Findings

Nonreciprocal cavities do not break the time-bandwidth limit.

Derived relations govern the dynamics of nonreciprocal resonators.

Nonreciprocity offers other attractive properties beyond the time-bandwidth constraint.

Abstract

The time-bandwidth limit inherently relates the lifetime of a resonance and its spectral bandwidth, with direct implications on the maximum storage time of a pulse versus its frequency content. It has been recently argued that nonreciprocal cavities may overcome this constraint, by breaking the strict equality of their incoupling and outcoupling coefficients. Here, we generally study the implications of nonreciprocity on resonant cavities and derive general relations, stemming from microscopic reversibility, that govern their dynamics. We show that nonreciprocal cavities do not provide specific advantages in terms of the time-bandwidth limit, but they may have other attractive properties for nanophotonic systems.