Shu Jia

Dispersive superfluid-like shock waves in nonlinear optics

We experimentally demonstrate dispersive optical shock waves in ID and 21), characterize their nonlinear properties, and observe the complex interactions when two such shocks collide.

Forward four-wave mixing with defocusing nonlinearity

We experimentally demonstrate degenerate, forward four-wave mixing effects in a self-defocusing photorefractive medium, in both one and two transverse dimensions. We observe the nonlinear evolution of new modes as a function of propagation distance, in both the near-field and far-field (Fourier space) regions.

Forward Four-Wave Mixing with Defocusing Nonlinearity

We experimentally demonstrate degenerate, forward four-wave mixing in a self-defocusing photorefractive medium, in both one and two transverse dimensions. The cascaded evolution of new modes and potential asymptotic behavior are discussed.

Rayleigh–Taylor instability in nonlinear Schrödinger flow

The Rayleigh–Taylor instability (RTI) is a fundamental fluid instability that occurs when a light fluid is accelerated into a heavier one. While techniques for observing the RTI in classical fluids continue to improve, the instability has not been demonstrated in quantum fluids. Here, we exploit the formal equivalence between condensed matter and coherent nonlinear optics to observe the superfluid-like instability directly in the optical system. For the RTI, an initial refractive index gradient sets the acceleration, while self-induced nonlinear interactions lead to velocity differences and shear. The experimental observations show that density fingering is always accompanied by vortex generation, with perturbation modes following a hybrid dynamics: horizontal modes (along the interface) propagate as an incompressible fluid, but the vertical length scale (mixing length) is set by compressible shock dynamics. The growth rate, obtained analytically, shows that inhibition due to diffraction has the same spectral form as viscosity and diffusion, despite the fact that the system is dispersive rather than dissipative. This gives rigorous support for the observation that turbulence in quantum fluids has the same scaling as turbulence in normal fluids. The results hold for any Schrodinger flow, e.g. superfluids and quantum plasma, and introduce a new class of fluid-inspired instabilities in nonlinear optics.

Spatially Dispersive Shock Waves in Nonlinear Optics

We discuss recent experimental work demonstrating spatial dispersive shock waves (DSWs). These structures occur whenever nonlinearity enhances diffraction so that wave spreading becomes intensity-dependent. The mechanism of this spreading follows naturally from a hydrodynamic description of light flow, in which wave steepening from phase gradients allows faster parts of a beam to overtake slower parts. Scaling relationships are developed for this spreading and experimentally observed, in both local and nonlocal media.

Observation of the condensation of classical waves

We report a theoretical, numerical and experimental study of condensation of classical optical waves. The condensation of observed directly, as a function of nonlinearity and wave kinetic energy, in a self-defocusing photorefractive crystal.

Dispersive, superfluid-like shock waves in nonlinear optics: Properties & interactions

We experimentally demonstrate dispersive optical shock waves in ID and 21), characterize their nonlinear properties, and observe the complex interactions when two such shocks collide.

Richtmyer-Meshkov instability in nonlinear optics

We experimentally demonstrate an all-optical Richtmyer-Meshkov instability, in which a shock wave is incident on an intensity interface. Intensity fingering and shear-generated vortices are observed for both 1D and 2D shock-wave impulses.

Observation of Classical Optical Wave Condensation

We demonstrate the nonlinear condensation of classical optical waves. The condensation is observed directly, as a function of nonlinearity and wave kinetic energy, in a self-defocusing photorefractive crystal.

Condensation of classical optical waves

We demonstrate the nonlinear condensation of classical optical waves. The condensation is observed directly, as a function of nonlinearity and wave kinetic energy, in a self-defocusing photorefractive crystal.