Observation of the rupture of a photon dam in an optical ber

We investigate the temporal photonic analogue of the dam breaking phenomenon of shallow water. We observe the decay of a steep input front, representing the photonic dam, into counter-propagating rarefaction and dispersive shock wave. Our measurement shows the clear evidence of a critical transition of the dispersive shock wave into a self-cavitating state, characterized by the presence of a null-intensity point into the shock fan. The precise measurements of the temporal waveform of the cavitating state dynamics allows for a fully quantitative test of the Whitham modulation theory applied to the defocusing nonlinear Schroedinger equation.