Planar nonlinear metasurface optics and their applications
Résumé
Metasurfaces are artificial two-dimensional (2D) planar surfaces that consist of subwavelength "meta-atoms" (i.e., metallic or dielectric nanostructures). They have been known for the capability to achieve better and more efficient light control in comparison to their traditional optical counterparts. Abrupt and sharp changes in the electromagnetic properties can be induced by the metasurfaces rather than the conventional gradual accumulation that requires more propagation distances. Based on this feature, planar optical components like mirrors, lenses, waveplates, isolators and even holograms with ultrasmall thicknesses have been developed. Most of the current metasurface studies focused on tailoring the linear optical effects for applications such as cloaking, lens imaging and three-dimensional holography. Recently, the uses of metasurfaces to enhance nonlinear optical effects have attracted significant attention from the research community. Benefiting from the resulted efficient nonlinear optical processes, the fabrication of integrated all-optical nano-devices with peculiar functionalities including broadband frequency conversions and ultrafast optical switching will become achievable. Plasmonic excitation is one of the most effective approaches to increase the nonlinear optical responses due to its induced strong local electromagnetic field enhancement. For instance, continuous phase control on the effective nonlinear polarizability of plasmonic metasurfaces has been demonstrated through spin-rotation light coupling. The phase of the nonlinear polarization can be continuously tuned by spatially changing the "meta-atoms" orientations during second and third harmonic generation (SHG/THG) processes, while the nonlinear metasurfaces also exhibit homogeneous linear properties. In addition, an ultrahigh second-order nonlinear susceptibility up to 10 4 pm/V has recently been reported by coupling the plasmonic modes of patterned metallic arrays with intersubband transition of multi-quantum-well layered substrate. In order to develop ultra-planar nonlinear plasmonic metasurfaces, two-dimensional materials such as graphene and transition metal dichalcogenides (TMDCs) have been extensively studied based on their unique nonlinear optical properties. The third-order nonlinear coefficient of graphene is 5 times as that of gold substrate, while TMDC materials also exhibit a strong second-order magnetic susceptibility. In this review, we first focus on the main principles of planar nonlinear plasmonics based on metasurfaces and 2D nonlinear materials. The advantages and challenges for incorporating 2D nonlinear materials into metasurfaces have been discussed, 2 followed by their potential applications including orbital angular momentum (OAM) manipulating, and quantum optics.
Domaines
Optique / photonique
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