CE30 - Physique de la matière condensée et de la matière diluée

Superfluid and turbulent light in complex media – STLight

Submission summary

The STLight project focuses on the experimental study of photonic fluids in disordered environments. Superfluidity, the ability of a fluid to move without friction along a pipe or past an obstacle, is one of the most spectacular features of quantum fluids. In nonlinear optics, it manifests as light propagating without being altered by an inhomogeneous environment. The exact opposite happens in the linear case, where light undergoes spatial localisation in disordered media. The main ambition of the STLight project is to study the transition from spatial localisation to superfluidity in complex, but fully controlled, environments, positioning the project at the edge between quantum hydrodynamics and waves in nonlinear complex media. Strong turbulence in complex media will naturally arise in the system and will be investigated. It will, besides addressing transport in disordered optical systems, significantly benefit in both the nonlinear optics and quantum hydrodynamics communities.

The project STLight relies on the main research hypothesis that the paraxial propagation of an optical field in a nonlinear transparent medium is formally analogous to the evolution of a two-dimensional quantum fluid. In this analogy, the spatial evolution of the optical field along the propagation direction is analogous to the temporal evolution of the wavefunction of a quantum gas. Simply put, each transverse plane in the nonlinear medium is equivalent to a “snapshot” of the temporal dynamics of a two-dimensional quantum fluid. To realise this analogy, photons need to acquire an effective mass and be in a fully controlled effective (repulsive) interaction – two features that are allowed in properly engineered photonic systems. For instance, a photorefractive crystal in which the optical index can be structured in an arbitrary and reconfigurable way, is a perfect candidate for studying fluids of light, notably in disordered environments, and is at the heart of our experimental apparatus.

The project is outlined along 3 work packages organised following a progressive increase of the system’s complexity, from the simpler quasi-homogeneous case toward a completely disordered case; In particular, we will study:
1/ Turbulence in a nonlinear crystal with few obstacles
--> Objective – Study the interplay between vortices and obstacles in simple configurations, through vortex generation in the wake of a 1D set of obstacles and the dynamics of vortices in the vicinity of obstacles.
2/ Fluids of light in complex media, through the robustness of superfluidity in a disordered system, as well as the robustness of localised states in a nonlinear medium.
--> Objective – i) Design, implement and control the photo-induction of disordered patterns in the crystal in a 2D, z-independent configuration, ii) Study the extreme regimes of spatial localisation and superfluidity, iii) Study the intermediate turbulent regime.
3/ Towards fluids of light in “time-dependant” systems
--> Objective – In this much more exploratory part, we will study time-dependant dynamics of the fluid of light with i) a time-dependant disorder and ii) a full 3D fluid of light.

The main technical breakthrough to tackle is the control the creation of the disordered environment in a nonlinear system. This implementation is made possible in the experimental system that as the potential to overcome this technical barrier.

The results are expected to strengthen the fundamental knowledge and experimental developments related to fluids of light and quantum turbulence and to open new perspectives on the spatial localisation of light in nonlinear environments.

Project coordination

Claire Michel (Institut de Physique de Nice)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.

Partner

INPHYNI Institut de Physique de Nice

Help of the ANR 230,815 euros
Beginning and duration of the scientific project: December 2021 - 48 Months

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