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.

Journal/Review: PHYSICAL REVIEW LETTERS

Volume: 128 (1)      Pages from: 13901-1  to: 13901-6

More Information: The authors acknowledge financial support from EPSRC (UK Grant No. EP/P006078/2) and the European Union’s Horizon 2020 research and innovation program, Grant Agreement No. 820392. N. W. wishes to acknowledge support from the Royal Commission for the Exhibition of 1851. The authors would like to thank Bienvenu Ndagano for the fruitful discussions and valuable suggestions throughout this project.
KeyWords: Over-reflection; Instability; Sound; Waves
DOI: 10.1103/PhysRevLett.128.013901

Citations: 31
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