Second‐Harmonic Generation in Strained Silicon Metasurfaces

Abstract

Dielectric metasurfaces supporting Mie resonances can allow significantly boosted and tailored nonlinear light–matter interactions at the nanoscale. However, nonlinear dielectric metasurfaces typically only have odd‐order nonlinearities, unless resorting to material systems such as GaAs, GaP, or LiNbO3, each with unique challenges in device fabrication and integration. As the most widely adopted constituent material of metasurfaces, silicon (Si) does not possess an intrinsic second‐order nonlinear susceptibility. Herein, second‐harmonic generation (SHG) in a Si metasurface strained by a silicon nitride (SiN x ) cladding layer is demonstrated. Utilizing the stress caused by the SiN x layer to break the inversion symmetry of the bulk Si crystal, greatly enhanced SHG in the strained Si metasurface compared with that from an unpatterned Si film with the SiN x cladding layer, with an experimentally measured conversion efficiency as high as 4.2 × 10−5 W−1, is observed. Experiments are further performed and it is concluded that the enhanced SHG is most likely due to the applied stress instead of charged defects in the SiN x cladding. This work opens a new route to realizing dielectric metasurfaces with second‐order nonlinearity in a complementary metal–oxide–semiconductor (CMOS)‐compatible platform.

Metasurfaces toward Optical Manipulation Technologies for Quantum Precision Measurement

“…Alldielectric resonant structural units are capable of producing electromagnetic resonant modes in the optical band, such as Mie resonance, [130] while bringing many advantages: low energy dissipation into heat and stronger nonlinear effects, the ability to excite strong electric and magnetic dipole and multipole modes simultaneously, opening up a simpler and more versatile resonant pathway. [131][132][133] High refractive index dielectric materials such as Si, [134,135] SiN x , [136][137][138] TiO 2 , [139,140] and GaN [141][142][143] are commonly used to prepare dielectric metasurfaces, and phase and amplitude modulation frequently depends on the optimal design of the shape and geometric parameters of the unit structure, which typically has only a very narrow operating bandwidth, [144][145][146] while placing high demands on the processing technology.…”

Efficient Second- and Third-Harmonic Generations in Er3+/Fe2+-Doped Lithium Niobate Single Crystal with Engineered Surficial Cylindrical Hole Arrays

“…SHG and THG in individual AlGaAs nanoantennas using far-field mapping with radially and azimuthally polarized cylindrical vector beams were achieved by Camacho-Morales and coworkers [ 24 ]. SHG in a Si metasurface strained by a SiN x overlayer was demonstrated by Zhao and coworkers [ 25 ], where the SiN x overlayer was used to break the inversion symmetry of crystalline Si.…”

Giant Second Harmonic Generation from Membrane Metasurfaces

“…Alternatively, structural resonances have been used to boost the nonlinear light–matter interactions by strongly localizing the electromagnetic fields within the nanostructures. Various resonance mechanisms were proposed, including Fano resonances, , Mie resonances, , anapoles, − and bound states in the continuum (BIC). − …”