Wavefront shaping with nonlinear four-wave mixing

Abstract

Wavefront manipulations have enabled wide applications across many interdisciplinary fields ranging from optics and microwaves to acoustics. However, the realizations of such functional surfaces heavily rely on micro/nanofabrication to define the structured surfaces, which are fixed and only work within a limited spectrum. To address these issues, previous attempts combining tunable materials like liquid crystal or phase-change ones onto the metasurfaces have permitted extra tunability and working spectra, however, these additional layers bring in inevitable loss and complicate the fabrication. Here we demonstrate a fabrication-free tunable flat slab using a nonlinear four-wave mixing process. By wavefront-shaping the pump onto the flat slab, we can successfully tune the effective nonlinear refraction angle of the emitting FWM beams according to the phase-matching condition. In this manner, a focusing and a defocusing nonlinear of FWM beam through the flat slab have been demonstrated with a converging and a diverging pump wavefronts, respectively. Furthermore, a beam steering scheme over a 20° angle has been realized through a non-degenerate four-wave mixing process by introducing a second pump. These features open up a door to manipulating light propagation in an all-optical manner, paving the way to more functional and tunable flat slab devices in the applications of imaging and all-optical information.

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“…Nonlinear wavefront shaping has attracted a great deal of research interest in the past two decades 1 – 3 It refers to the spatial reconfiguration of a beam at a new frequency and has been applied to generate non-diffracting beam, 4 vortex beams, 5 and mode conversion 6 . Nonlinear photonic crystal (NPC) is an excellent material for nonlinear wavefront shaping, and it has high frequency conversion efficiency and flexible design space.…”

Synergy between AI and Optical Metasurfaces: A Critical Overview of Recent Advances

“…Thus, such synergy between plasmonics and optical nonlinearity in hybrid metasurfaces enhances the metasurface performance and generates novel functionalities impossible to achieve with any of the mentioned components separately. Some of the nonlinear phenomena used for metasurface tuning include second harmonic generation [179], third harmonic generation [180], higher harmonic generation [181], optical-parametric oscillation [182], optical rectification [183], four-wave mixing in metasurfaces [184], etc. Related nonlinear phenomena also have great importance, like the optical Kerr effect (a third-order nonlinear process of refractive index changes with the light intensity) [185] and the effects related to it like, e.g., self-focusing, self-phase-modulation, soliton formation [186], two-photon photochromism [187] and many more.…”