Measurement of penrose superradiance in a photon superfluid

Year: 2022

Authors: Braidotti M.C., Prizia R, Maitland C., Marino F., Prain A., Starshynov I., Westerberg N., Wright E.M., Faccio D.

Autors Affiliation: School of Physics and Astronomy, University of Glasgow, G12 8QQ Glasgow, United Kingdom.
Institute of Photonics and Quantum Sciences, Heriot-Watt University, EH14 4AS Edinburgh, United Kingdom.
CNR-Istituto Nazionale di Ottica, Largo Enrico Fermi 6, I-50125 Firenze, Italy.
INFN, Sezione di Firenze, Via Sansone 1, I-50019 Sesto Fiorentino (FI), Italy.
Wyant College of Optical Sciences, University of Arizona, Tucson, Arizona 85721, USA.

Abstract: The superradiant amplification in the scattering from a rotating medium was first elucidated by Sir Roger Penrose over 50 years ago as a means by which particles could gain energy from rotating black holes. Despite this fundamental process being ubiquitous also in wave physics, it has only been observed once experimentally, in a water tank. Here, we measure this amplification for a nonlinear optics experiment in the superfluid regime. In particular, by focusing a weak optical beam carrying orbital angular momentum onto the core of a strong pump vortex beam, negative norm modes are generated and trapped inside the vortex core, allowing for amplification of a reflected beam. Our experiment demonstrates amplified reflection due to a novel form of nonlinear optical four-wave mixing, whose phase-relation coincides with the Zel’dovich-Misner condition for Penrose superradiance in our photon superfluid, and unveil the role played by negative frequency modes in the process.


Volume: 128      Pages from: 013901-1  to: 013901-6

KeyWords: Analogue-gravity, quantum fluids of light
DOI: 10.1103/PhysRevLett.128.013901