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Belgiorno, Cacciatori, Clerici, Gorini, Ortenzi, Rizzi and colleagues test the prediction that event horizons, real or analogue, excite the quantum vacuum and emit Hawking radiation. They use ultrashort laser pulse filaments, intense pulses in a transparent Kerr medium that travel apparently without diffraction. The filament creates a travelling refractive index perturbation in fused silica glass that acts as an analogue event horizon. Photons emitted at 90 degrees to the beam are collected and their spectra recorded. They observe spontaneous photon emission with the characteristics of Hawking radiation, distinct from other known emission mechanisms, confirming theoretical predictions.

Hawking Radiation from Ultrashort Laser Pulse Filaments