Coherent Perfect Rotation

TL;DR

This paper demonstrates that only time-odd (Faraday) rotation enables coherent perfect rotation in linear, conservative optical media, highlighting the importance of time reversal symmetry and coherence in mode conversion.

Contribution

It introduces the concept that coherent perfect rotation requires time-odd Faraday rotation, contrasting with optical activity and expanding understanding of mode conversion in optics.

Findings

Only Faraday rotation achieves coherent perfect rotation.

Coherent perfect rotation involves complete polarization mode transfer.

Time reversal symmetry is essential for perfect mode conversion.

Abstract

Two classes of conservative, linear, optical rotary effects (optical activity and Faraday rotation) are distinguished by their behavior under time reversal. In analogy with coherent perfect absorption, where counterpropagating light fields are controllably converted into other degrees of freedom, we show that only time-odd (Faraday) rotation is capable of coherent perfect rotation in a linear and conservative medium, by which we mean the complete transfer of counterpropagating coherent light fields into their orthogonal polarization. This highlights the necessity of time reversal odd processes (not just absorption) and coherence in perfect mode conversion and may inform device design.