Penrose Superradiance in Nonlinear Optics

TL;DR

This paper demonstrates theoretically that Penrose superradiance, originally from black hole physics, can occur in nonlinear optics through vortex pump beams, leading to signal amplification via negative norm mode trapping.

Contribution

It introduces a novel regime of nonlinear optics where ergoregion concepts enable signal amplification through superradiance mechanisms.

Findings

Penrose superradiance can occur in nonlinear optical media.

Signal gain results from negative norm mode trapping in vortex cores.

The study provides a new perspective on nonlinear optical processes involving ergoregions.

Abstract

Particles or waves scattered from a rotating black hole can be amplified through the process of Penrose superradiance, though this cannot currently be observed in an astrophysical setting. However, analogue gravity studies can create generic rotating geometries exhibiting an ergoregion, and this led to the first observation of Penrose superradiance as the over-reflection of water waves from a rotating fluid vortex. Here we theoretically demonstrate that Penrose superradiance arises naturally in the field of nonlinear optics. In particular, we elucidate the mechanism by which a signal beam can experience gain or amplification as it glances off a strong vortex pump beam in a nonlinear defocusing medium. This involves the trapping of negative norm modes in the core of the pump vortex, as predicted by Penrose, which in turn provides a gain mechanism for the signal beam. Our results elucidate a new regime of nonlinear optics involving the notion of an ergoregion, and provide further insight into the processes involved in Penrose superradiance.