Optical hydrodynamics: A shock wave perspective
This dissertation presents experimental and theoretical studies of spatial dispersive shock waves. Inspired by the fluid analogy of wave dynamics, we made the first demonstration of a dispersive shock wave in spatial nonlinear optics. Richer phenomena are revealed with such dispersive waves’ interactions and dynamics under various initial configurations. The phenomenological observations here will enable a novel way of all-optical modeling of fluid-like experiments in optics. Implied applications can be extended into many fields, including novel optical broadband sources, signal processing, optoelectronic devices, imaging and microscopy.
Dispersive shock waves arise from nonlinear wave breaking and mode dispersion, and are a fundamental type of fluid behavior in systems with no or near-zero viscosity, such as inertia-dominated hydraulic bores, cold plasmas, and superfluids. At first, we experimentally exploit the well-known relation between superfluids and nonlinear optics to study the photonic equivalence of dispersive, dissipationless shock waves in the spatial regime. Basic interactions between them indicate a nonlinear version of Huygens’ Principle. Although viscosity is absent in our physical systems, we investigate other means to suppress the dispersive shock wave through non-locality and spatial incoherence of light. This spatially incoherent light enables us to experimentally demonstrate a new type shock wave with effective “negative pressure” under a nonlinear Fresnel diffraction configuration. Also, we study the associated problem of the wave nonlinearly scattered by a barrier potential. Our observations suggest nonlinear wave tunneling, dispersive shock wave formation and optical hydrodynamic flow. Finally, we develop a novel method to probe the wave evolution dynamics along the nonlinear distorted medium. This new holographic approach may eventually lead to a new type of super-resolution microscopy in the near future.