Towards the experimental observation of turbulent regimes and the associated energy cascades with paraxial fluids of light

Abstract

The propagation of light in nonlinear optical media has been widely used as a tabletop platform for emulating quantum-like phenomena due to their similar theoretical description to quantum fluids. These fluids of light are often used to study 2-dimensional phenomena involving superfluid-like flows, yet turbulent regimes still remain underexplored. In this work, we study the possibility of creating 2-dimensional turbulent phenomena and probing their signatures in the kinetic energy spectrum. To that end, we emulate and disturb a fluid of light with an all-optical defect using the propagation of two beams in a photorefractive crystal. Our experimental results show that the superfluid regime of the fluid of light breaks down at a critical velocity at which the defect starts to exert a drag force on the fluid, in accordance with the theoretical and numerical predictions. Furthermore, in this dissipative regime, nonlinear perturbations are excited on the fluid that can decay into vortex structures and thus precede a turbulent state. Using the off-axis digital holographic method, we reconstructed the complex description of the output fluids and calculated the incompressible component of the kinetic energy. With these states, we observed the expected power law that characterizes the generated turbulent vortex dipole structures. The findings enclosed in this manuscript align with the theoretical predictions for the vortex structures of 2-dimensional quantum fluids and thus may pave the way to the observation of other distinct hallmarks of turbulent phenomena, such as distinct turbulent regimes and their associated power laws and energy cascades.

Exploring new phenomena in analogue physical simulations through an optical feedback loop in paraxial light fluids

“…In a previous work, 26 we demonstrated the capability of the current experimental setup to produce arbitrary states in both amplitude and phase. Specifically, we successfully generated experimentally complex states with a mean absolute percentage error below 7%.…”

“…The initial case study conducted in this work explored the collision between three flat-top states, similar to the investigation detailed in. 26 For this work, we considered an initial superposition between the profiles of the flat-tops and higher powers. The results are presented in Figure 2 for 6 passages through the crystal, and following the procedure in, 26 the input power is adjusted at each passage to account for the crystal absorption.…”

“…26 For this work, we considered an initial superposition between the profiles of the flat-tops and higher powers. The results are presented in Figure 2 for 6 passages through the crystal, and following the procedure in, 26 the input power is adjusted at each passage to account for the crystal absorption. The interplay between these two modifications results in a more chaotic dynamics, deviating from the symmetry observed in, 26 thereby facilitating the observation of the merging of vortices with opposite signs, followed by the emission of sound waves.…”

“…In recent years, there have been notable advances in the field of analogue physical simulators employing optical systems, with tabletop experiments starting to become very common. [1][2][3][4][5] In particular, these simulations have focused on emulating quantum fluids, leveraging on the nonlinear Schrodinger equation (NSE). This equation provides a formal mathematical equivalence for phenomena such as Bose-Einstein Condensates (BECs) 6 and the behavior of electromagnetic fields in nonlinear optical media [7][8][9] .…”

“…7,8 This means that the analogue fluid of light is two-dimensional, and each slice along the propagation direction represents the fluid of light at different moments in time. Over the past years, many experimental efforts have observed a range of quantum-like effects with these paraxial configurations, including superfluidity of light, 1,17 Bogoliubov dispersion relation measurements, 18,19 vortex turbulence, 1, 4, 20 analogue cosmological particle creation, 21 or superradiance-like signatures, 22 to name a few. Usually, these experimental implementations use hot atomic vapors, 23 thermo-optical media, 24,25 or photorefractive crystals 1, 3 as the nonlinear optical material.…”