Dynamics of photon fluid flows driven by optical pistons

The piston problem, i.e. the dynamics of a uniform gas at rest under the action of a moving piston, is fundamental in shock wave physics. In conservative systems, shock waves are regularized by the formation, owing to dispersion, of rapidly oscillating non-stationary structures, called dispersive shock waves (DSWs). In this work, we investigate the analogous problem for a photon fluid. To mimic gas compression, we study the propagation, along a highly normal dispersive optical fi ber, of a chirped square pulse with an abrupt jump of instant frequency (velocity) at its center (Fig. 1(a)). During the propagation, the two parts of this dual -frequency pulse propagate at different velocities mimicking gas compression. The fast part plays the role of a moving piston while the slow part plays the role of the compressed gas. The internal collision and squeezing of these two parts lead to the generation of a pair of DSWs connected by an intermediate plateau of constant density.