Nonreciprocal light propagation induced by a subwavelength spinning cylinder

TL;DR

This paper demonstrates how a subwavelength spinning dielectric cylinder can induce nonreciprocal light propagation in waveguides through chiral mode interactions, offering a magnetic-free approach for integrated photonic devices.

Contribution

It reveals the mechanism of nonreciprocal light transmission induced by a spinning cylinder's chiral modes and explores how system parameters influence optical isolation.

Findings

Higher-order chiral modes enhance nonreciprocity.

Increased spinning speed strengthens nonreciprocal effects.

Optimal coupling distance maximizes optical isolation.

Abstract

Nonreciprocal optical devices have broad applications in light manipulations for communications and sensing. Non-magnetic mechanisms of optical nonreciprocity are highly desired for high-frequency on-chip applications. Here, we investigate the nonreciprocal properties of light propagation in a dielectric waveguide induced by a subwavelength spinning cylinder. We find that the chiral modes of the cylinder can give rise to unidirectional coupling with the waveguide via the transverse spin-orbit interaction, leading to different transmissions for guided wave propagating in opposite directions and thus optical isolation. We reveal the dependence of the nonreciprocal properties on various system parameters including mode order, spinning speed, and coupling distance. The results show that higher-order chiral modes and larger spinning speed generally give rise to stronger nonreciprocity, and there exists an optimal cylinder-waveguide coupling distance where the optical isolation reaches the maximum. Our work contributes to the understanding of nonreciprocity in subwavelength moving structures and can find applications in integrated photonic circuits, topological photonics, and novel metasurfaces.