High amplitude, ultrashort, longitudinal strain solitons in sapphire

We demonstrate the development of high-amplitude picosecond strain pulses in a sapphire single crystal into an ultrafast compressional soliton train. For this purpose, large-intensity light pulses were used to excite a metal film, yielding a 2 orders of magnitude higher strain than that achieved in earlier studies. Propagation of the packets is monitored over a distance of several millimeters by means of Brillouin light scattering. A one-parameter model, based on the Korteweg-de Vries-Burgers equation, simultaneously explains the observed behavior at all strains and temperatures under study. We predict up to 11 solitons in the train, reaching pressures as high as 40 kbar and 0.5 ps temporal widths.