Measurement of Penrose Superradiance in a Photon Superfluid

Maria Chiara Braidotti, Radivoje Prizia, Calum Maitland, Francesco Marino, Angus Prain, Ilya Starshynov, Niclas Westerberg, Ewan M. Wright, Daniele Faccio

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


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.

Original languageEnglish (US)
Article number013901
JournalPhysical review letters
Issue number1
StatePublished - Jan 7 2022

ASJC Scopus subject areas

  • General Physics and Astronomy


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