A theory of Stimulated and Spontaneous Axion Scattering

TL;DR

This paper develops a nonlinear theory describing how dynamical axions can be resonantly excited and amplified by electromagnetic waves in certain materials, with potential applications in optoelectronics.

Contribution

It introduces a novel theoretical framework for stimulated and spontaneous axion scattering, highlighting enhanced amplification over traditional scattering processes.

Findings

Axion-mediated exponential growth of Stokes beams.

Spontaneous generation of counter-propagating modes.

Amplification can be controlled with external magnetic fields.

Abstract

We present a theory for nonlinear, resonant excitation of dynamical axions by counter-propagating electromagnetic waves in materials that break both $\mathcal{P}$ and $\mathcal{T}$ symmetries. We show that dynamical axions can mediate an exponential growth in the amplitude of the lower frequency (Stokes) beam. We also discuss spontaneous generation of a counter-propagating Stokes mode, enabled by resonant amplification of quantum and thermal fluctuations in the presence of a single pump laser. Remarkably, the amplification can be orders of magnitude larger than that obtained via stimulated Brillouin and Raman scattering processes, and can be modulated with the application of external magnetic fields, making stimulated axion scattering promising for optoelectronics applications.