High- Q Quasibound States in the Continuum for Nonlinear Metasurfaces

Abstract

Sharp electromagnetic resonances play an essential role in physics in general and optics in particular. The last decades have witnessed the successful developments of high-quality (Q) resonances in microcavities operating below the light line, which however is fundamentally challenging to access from free space. Alternatively, metasurface-based bound states in the continuum (BICs) offer a complementary solution of creating high-Q resonances in devices operating above the light line, yet the experimentally demonstrated Q factors under normal excitations are still limited. Here, we present the realizations of quasi-BIC under normal excitation with a record Q factor up to 18 511 by engineering the symmetry properties and the number of the unit cells in all-dielectric metasurface platforms. The high-Q quasi-BICs exhibit exceptionally high conversion efficiency for the third harmonic generation and even enable the second harmonic generation in Si metasurfaces. Such ultrasharp resonances achieved in this work may immediately boost the performances of BICs in a plethora of fundamental research and device applications, e.g., cavity QED, biosensing, nanolasing, and quantum light generations.

Dielectric Resonance-Based Optical Metasurfaces: From Fundamentals to Applications

“…By controlling the mirror symmetry of two zigzag hydrogenated amorphous silicon structures, Huygens' condition and BICs have been bridged, leading to a Huygens' BICs in the near-infrared waveband ( Liu and Choi, 2018 ). By engineering the symmetry properties and the number of the unit cells, quasi-BICs that can significantly boost the nonlinear generation have been realized with a Q factor of 18,511 ( Liu et al., 2019c ). The second-harmonic generation (SHG) can also be enhanced by more than 3 orders of magnitude by combining the BICs in silicon nanostructures and a WS 2 monolayer ( Bernhardt et al., 2020 ).…”

Nonlinear Bound States in the Continuum of Etchless Lithium Niobate Metasurfaces

“…As is recently reported, BICs have been employed in silicon-based resonant metasurfaces to enhance nonlinear optical effects, such as third-harmonic generation [55][56]. However, due to centrosymmetry of Si crystal, Si shows no second order nonlinearity without strain or applied electric field.…”

Clay‐Based Solid Acid Catalyst for the Alkylation of p‐Cresol with tert‐Butyl Alcohol

“…Literatures are available on the liquid phase alkylation of p ‐cresol with TBA using catalysts such as heteropoly acids supported on transition metal oxide, ionic liquids, 12‐Tungstophosphoric acid immobilized on modified macroporous phenol‐furfural sulphonic acid resin and sulphated zirconia . The reactions have also been carried out in vapour phase reactor using zirconia or titanium supported heteropoly acid ,.…”