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arXiv · 2412.16852

Enhanced third-harmonic generation empowered by doubly degenerate quasi-bound states in the continuum

Tingting Liu·Meibao Qin·Jumin Qiu·Xu Tu·Huifu Qiu·Feng Wu·Tianbao Yu·Qiegen Liu·Shuyuan Xiao
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Abstract

Recent advancements in nonlinear nanophotonics are driven by the exploration of sharp resonances within high-index dielectric metasurfaces. In this work, we leverage doubly degenerate quasi-bound states in the continuum (quasi-BICs) to demonstrate robust enhancement of third-harmonic generation (THG) in silicon metasurfaces. These quasi-BICs are governed by $C_{4v}$ symmetry and therefore can be equally excited with the pump light regardless of polarization. By tailoring the geometric parameters, we effectively control $Q$-factors and field confinement of quasi-BICs, and thus regulate their resonantly enhanced THG process. A maximum THG conversion efficiency up to $1.03\times10^{-5}$ is recorded under a pump intensity of 5.85 GW/cm$^{2}$. Polarization-independent THG profile is further confirmed by mapping its signal across the polarization directions. This work establishes foundational strategies for the ultracompact design of robust and high-efficiency photon upconversion systems.

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Tingting Liu, Meibao Qin, Jumin Qiu, Xu Tu, Huifu Qiu, Feng Wu, Tianbao Yu, Qiegen Liu, Shuyuan Xiao. 2024-12-22. Enhanced third-harmonic generation empowered by doubly degenerate quasi-bound states in the continuum. https://doi.org/10.1021/acs.nanolett.5c00146

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