Maria Chiara Braidotti (University of Glasgow) gives a webinar on “Amplification of waves from rotating media.”
Superradiance is the amplification of waves scattered by a rapidly rotating object, first proposed by Roger Penrose as a way to extract energy from rotating black holes. Despite being a fundamental process in wave physics, astrophysical superradiance has not been observed yet due to the large distances involved. However, proposal based on analogue gravity studies have demonstrated their versatility providing the first measurement of superradiance in a hydrodynamic experiment.
In this talk I will report the first measurement of Penrose superradiance in nonlinear optical systems, especially in a 2D photon fluid. Our system has access to the inner part of the analogue black hole, allowing to unveil the key role of the negative norm modes in the amplification process. I will also show a novel proposal to measure the 50 year old Zel’dovich prediction: the amplification of electromagnetic waves with angular momentum scattering by a spinning metallic sphere. The setup proposed consists in a superconducting circuit generating a magnetic field with angular momentum. I will explain the details of the proposed setup and measurement showing that it can be used also at the quantum level.
