We implement a stacking strategy in designing chiral metasurfaces with high rotational symmetry, enabling quasi-bound-in-the-continuum (quasi-BIC) resonances characterized by absolute chirality. The rotational symmetry allows a circularly polarized pump to be converted into a circularly polarized nonlinear signal. Meanwhile, our bilayered metasurface can be engineered to respond solely to one selected circular polarization. Consequently, integrating resonant chiral response and rotational symmetry endows a unique category of metasurfaces to upconvert any linear or unpolarized pump into a circularly polarized nonlinear signal. Our results reveal that when such a metasurface is subjected to a linearly polarized pump, the intensity ratio of the resultant circularly polarized signals varies with the order of the nonlinear process. Counterintuitively, this ratio scales as the fourth power of the local field enhancement in the second harmonic process and the second power in the third harmonic process. Our work offers a comprehensive theoretical description of the nonlinear processes in chiral structures with rotation and provides universal guidelines for designing nonlinear all-dielectric metasurfaces with a strong chiral response.
High-efficiency infrared upconversion imaging with nonlinear silicon metasurfaces empowered by quasi-bound states in the continuum
Nanchang University（南昌大学）；Institute for Advanced Study, Nanchang University（南昌大学高等研究院）；School of Education, Nanchang Institute of Science and Technology（南昌理工学院教育学院）；Guangdong Polytechnic Normal University（广东技术师范大学）
Nanchang University（南昌大学）；Nanchang Institute of Science and Technology（南昌理工学院）；The Key Laboratory of Weak-Light Nonlinear Photonics, Ministry of Education, School of Physics and TEDA Institute of Applied Physics, Nankai University（南开大学物理学院、泰达应用物理研究院（教育部弱光非线性光子学重点实验室））；Guangdong Polytechnic Normal University（广东技术师范大学）
Gold-polymer hybrid metasurface for polarization-independent enhanced third harmonic generation in the ultraviolet
Institute of Materials Science of Barcelona ICMAB – CSIC（巴塞罗那材料科学研究所）；Aviation and Missile Center, US Army CCDC（美国陆军CCDC航空与导弹中心）；University of Brescia（布雷西亚大学）
