  Quantum fluctuations on curved spacetimes cause the emission of pairs of
particles from the quantum vacuum, as in the Hawking effect from black holes.
We use an optical analogue to gravity to investigate the influence of the
curvature on quantum emission. Due to dispersion, the spacetime curvature
varies with frequency here. We analytically calculate for all frequencies the
particle flux, correlations and entanglement. We find that horizons increase
the flux with a characteristic spectral shape. The photon number correlations
transition from multi- to two-mode, with close to maximal entanglement. The
quantum state is a diagnostic for the mode conversion in laboratory tests of
quantum field theory on curved spacetimes.
