Superfluidity of Light and its Break-Down in Optical Mesh Lattices

TL;DR

This paper experimentally investigates superfluid-like behavior of light in a nonlinear optical mesh lattice, demonstrating the conditions under which superfluidity breaks down and highlighting the platform's potential for exploring complex fluid phenomena.

Contribution

It introduces a novel experimental setup using optical mesh lattices to study superfluidity and its breakdown in light, linking nonlinear optics with quantum fluid dynamics.

Findings

Identification of sound speed in the optical fluid.

Observation of a critical velocity for superfluidity.

Demonstration of superfluidity breakdown at high defect velocities.

Abstract

Hydrodynamic phenomena can be observed with light thanks to the analogy between quantum gases and nonlinear optics. In this Letter, we report an experimental study of the superfluid-like properties of light in a (1+1)-dimensional nonlinear optical mesh lattice, where the arrival time of optical pulses plays the role of a synthetic spatial dimension. A spatially narrow defect at rest is used to excite sound waves in the fluid of light and measure the sound speed. The critical velocity for superfluidity is probed by looking at the threshold in the deposited energy by a moving defect, above which the apparent superfluid behaviour breaks down. Our observations establish optical mesh lattices as a promising platform to study fluids of light in novel regimes of interdisciplinary interest, including non-Hermitian and/or topological physics.