Spontaneous Parity-Time Symmetry Breaking in Moving Media

TL;DR

This paper explores how moving media can cause spontaneous parity-time symmetry breaking in optical systems, leading to complex spectra and potential optical amplification, with implications for understanding instabilities in photonics.

Contribution

It demonstrates that electromagnetic wave evolution in moving media is governed by a non-Hermitian PT-symmetric operator, revealing conditions for symmetry breaking and optical amplification.

Findings

Complex frequency spectra with mirror symmetry in lossless systems

Optical amplification possible in the PT-broken regime

Spontaneous PT symmetry breaking linked to optical instabilities

Abstract

Optical instabilities in moving media are linked to a spontaneous parity-time symmetry breaking of the system. It is shown that in general the time evolution of the electromagnetic waves in moving media is determined by a non-Hermitian parity-time symmetric operator. For lossless systems the frequency spectrum of the time evolution operator may be complex valued, and has a mirror symmetry with respect to the real-frequency axis. The possibility of optical amplification of a light pulse in the broken parity-time symmetry regime is demonstrated.