Nonlinear Bound States in the Continuum of Etchless Lithium Niobate Metasurfaces

IEEE Photonics Journal

Genquan Han¹  Qiyu Yang²  Xuetao Gan²  Yan Liu³  Cizhe Fang³  Yue Hao³ 

[1] MOE Key Laboratory of Material Physics and Chemistry under Extraordinary Conditions, and Shaanxi Key Laboratory of Optical Information Technology, School of Physical Science and Technology, Northwestern Polytechnical University, Xi&x0027;Wide Bandgap Semiconductor Technology Disciplines State Key Laboratory, School of Microelectronics, Xidian University, Xi&x0027;an, China;

关键词: Bound states in the continuum;    All-dielectric metasurface Second-harmonic generation;   

DOI  :  10.1109/JPHOT.2020.3024789

来源: DOAJ

【 摘 要 】

Optical bound states in the continuum (BICs) have recently been studied in a wide range of material systems, where light is perfectly confined in the continuous spectrum of radiating modes. In this paper, we reported periodic nonlinear metasurfaces on the etchless LiNbO₃ platform, realizing the enhancement of second-order generation (SHG). All-dielectric heterogeneous metasurfaces are constructed by patterning a low-refractive-index polymer on a high refractive-index LiNbO₃ film without etching. Due to BICs, light is localized in the LiNbO₃ film where the excellent optical second-order nonlinearity is exploited. We demonstrated that with normal incident waves, symmetry-protected BICs are formed at near-infrared wavelength showing a vanishing linewidth in the transmission spectrum. In addition, to manifest the invisible BICs to detectable supercavity resonances at normal incidence, asymmetry is introduced into the system, degrading the symmetry-protected BICs to sharp resonances with a high Q factor. Furthermore, the second harmonic generation (SHG) of the etchless lithium niobate metasurface is studied, predicting that the SHG efficiency can exceed 10^-3 with 30 MW/cm² of the pump intensity. The proposed strategy without facing the fabrication challenge of etching single-crystal LiNbO₃ film opens a new avenue for the utilization of BIC in nonlinear optics of all-dielectric heterogeneous metasurfaces.

【 授权许可】

Unknown