Role of geometry in the superfluid flow of nonlocal photon fluids

Abstract

Recent work has unveiled a new class of optical systems that can exhibit the characteristic features of superfluidity. One such system relies on the repulsive photon-photon interaction that is mediated by a thermal optical nonlinearity and is therefore inherently nonlocal due to thermal diffusion. Here we investigate how such a nonlocal interaction, which at a first inspection would not be expected to lead to superfluid behavior, may be tailored by acting upon the geometry of the photon fluid itself. Our models and measurements show that restricting the laser profile and hence the photon fluid to a strongly elliptical geometry modifies thermal diffusion along the major beam axis and reduces the effective nonlocal interaction length by two orders of magnitude. This in turn enables the system to display a characteristic trait of superfluid flow: the nucleation of quantized vortices in the flow past an extended physical obstacle. These results are general and apply to other nonlocal fluids, such as dipolar Bose-Einstein condensates, and show that "thermal" photon superfluids provide an exciting and novel experimental environment for probing the nature of superfluidity, with applications to the study of quantum turbulence and analog gravity.

Thermo-optical interactions in a dye-microcavity photon Bose–Einstein condensate

“…In a propagating configuration in stationary conditions, the temporal delay of the thermooptic effect does not play a role. The signatures of superfluidity and non-local effects from the associated thermo-optic nonlinearity have been experimentally observed in this configuration [19,20]. In another work, Strinati and Conti have theoretically studied the stationary state of dye microcavity photon condensate subject to a non-local thermo-optic nonlinearity [21].…”

Superradiant scattering in fluids of light

“…In completely unrelated developments, a new approach to quantum fluids has emerged in the form of quantum fluids of light, where effective photon-photon interactions of a monochromatic laser beam propagating in a nonlinear medium lead to a collective behaviour of the many photon system, leading to a superfluid behaviour [16][17][18][19]. Such photon fluids have been shown to be suitable candidates for the simulation of analogue curved spacetimes [20,21], having received recent experimental attention [22].…”

Liquid Light with a Whirl

“…Room-temperature nonlocal photon fluids in a propagating geometry have also displayed signatures of superfluid behavior in the dispersion relation. Specifically, the phononlike linear dispersion of the long-wavelength collective modes was measured experimentally for coherent light propagation in a thermo-optical medium [15] along with nucleation of quantized vortices in the flow past an extended physical obstacle [16].…”