Nonlinear wave dynamics on a chip.

Shallow-water waves are a notable example of nonlinear hydrodynamics, giving rise to phenomena such as tsunamis and undular waves. These dynamics are typically studied in hundreds-of-meters-long wave flumes. In this work, we demonstrate a chip-scale wave flume, which exploits nanometer-thick superfluid helium films and optomechanical interactions to achieve nonlinearities surpassing those of extreme terrestrial flows. Measurements reveal wave steepening, shock fronts, and solitary wave fission—nonlinear behaviors predicted in superfluid helium but never directly observed. Our approach enables lithography-defined wave flume geometries, optomechanical control of hydrodynamic properties, and orders-of-magnitude faster measurements than terrestrial flumes. This approach combining quantum fluids and nanophotonics provides a platform to explore complex wave dynamics at the microscale. Editor's summary: The nonlinear behavior of water waves, such as solitons, rogue waves, and tsunamis, can be modeled to some extent in large pool facilities, with flumes extending hundreds of meters. At a vastly smaller scale, Reeves et al. report an on-chip approach that uses a thin film of superfluid helium confined to a lithographically defined silicon surface onto which flumes can be patterned. The on-chip approach enables lithographically defined geometries and dispersion, optomechanical control of fluid properties, and measurement speeds six orders of magnitude faster than conventional flumes, providing access to exotic hydrodynamic regimes otherwise inaccessible in a laboratory environment. —Ian S. Osborne [ABSTRACT FROM AUTHOR]