Coexistence of local and nonlocal shock waves in nanomaterials

Plasmonic resonances in metal nanoparticles allow the transduction of energy from a light beam into the heating of the hosting material. This has enabled new solutions for advanced photonics sensing, medical and biological applications, but, at the fundamental level, extreme events such as optical shock waves have received little investigation. In this work, we provide experimental evidence on the formation and interaction of two dispersive optical shock waves by illuminating a suspension of gold nanorods with a pulsed laser beam. This shock profile exhibits the usual nonlocal profile at long times, but we have also registered a distinct behaviour with a local contribution at short times. We can attribute both to the thermal response of the medium, with the different time scales being related to the efficient heating mechanism from the nanorods. This paves the way to using nanomaterials as a platform for studying fundamental nonlinear phenomena and developing novel solutions for sensing and control.