Nonlinear optics of surface plasmon toy black holes

Nonlinear optical behavior of recently introduced surface plasmon toy black hole models has been considered. Physical realization of these models involves droplets of liquid on a metal surface, which supports propagation of surface plasmons. Such droplets are shown to exhibit strongly enhanced nonlinear optical behavior in the frequency range near the surface plasmon resonance of a metal-liquid interface. This enhancement may be responsible for the missing orders of magnitude of field enhancement in the surface enhanced Raman scattering effect. In addition, experimental observation of the recently predicted optical second harmonic generation near the toy event horizon is reported. Finally, the possibility of toy Hawking radiation observation is discussed, and the expression for the effective Hawking temperature of a toy surface plasmon black hole is derived. The effective Hawking temperature appears to be in the range of a few hundreds Kelvin for the realistic droplet shapes, which may lead to a surprising conclusion that the shapes of the liquid droplets on metal substrates are to some degree determined by the Hawking radiation.