Hawking radiation and mode conversion at optically induced horizons.

The scattering of electromagnetic radiation is an essential and fundamental tool by which we may study light-matter interaction. In usual conditions, the medium is considered as stationary and scattering is characterized by a change in the wavevector spectrum of the light beam. The frequency of the beam is not affected. In this thesis we study the problem of scattering from a moving dielectric perturbation (DP) induced by the nonlinear Kerr effect. Light is scattered and resonantly transferred to two output modes identified by distinct frequencies, one positive and the other negative in the comoving reference frame. Experiments confirm generation of negative resonant radiation in a variety of settings, ranging from optical fibers to bulk Kerr media. A first Born approximation analysis, verified by numerical simulations, predicts that the mixing of the positive and negative modes during the scattering process leads to amplification at the expense of the DP. This provides a link with the spontaneous emission of photons, known as “Hawking radiation”, excited at the event horizon of a gravitational black hole. The moving DP is thus described using the tools of transformation optics and general relativity, in terms of a flowing medium which curves the effective space-time metric as seen by the light rays. Our experimental results show evidences of spontaneous photon emission by the analogue horizon associated to the moving DP, which are in quantitative agreement with the Hawking model.