Zhong Hui, Song Liwei, Tian Ye
Opt Express. 2024 Oct 21;32(22):39017-39024. doi: 10.1364/OE.537982.
The compression and integration of nonlinear optical processes to the nanoscale are expected to have significant implications for quantum optics, biology, and medicine. In this work, a composite metasurface consisting of a hollow-bow-tie-shaped metal metasurface and a patterned amorphous silicon metasurface is proposed. An external terahertz (THz) electric field enhanced by the hollow-bow-tie structure is employed to break the centrosymmetry, which allows the generation of optical second harmonic. Meanwhile, the amorphous silicon nanocolumns inside the hollow-bow-tie-shaped structure enhance the optical laser field and improve the conversion efficiency of second and third harmonics. The numerical results indicate that at an incident optical laser intensity of 1.20 GW/cm and a y-component of the incident THz electric field of 10 kV/cm, the powers of the generated second and third harmonics are 3.96 × 10 W and 7.42 × 10 W, respectively, with conversion efficiencies of 3.93 × 10 and 7.18 × 10. The conversion efficiency of the third harmonic is increased by a factor of 700 compared to that of unpatterned silicon. The configuration proposed in this paper offers a solution for applications that need to take into account both high nonlinear efficiency and ultra-fast tunability.
非线性光学过程在纳米尺度上的压缩和集成有望对量子光学、生物学和医学产生重大影响。在这项工作中，提出了一种由中空蝴蝶结形金属超表面和图案化非晶硅超表面组成的复合超表面。利用中空蝴蝶结结构增强的外部太赫兹（THz）电场来打破中心对称性，从而实现光学二次谐波的产生。同时，中空蝴蝶结形结构内部的非晶硅纳米柱增强了光学激光场并提高了二次和三次谐波的转换效率。数值结果表明，在入射光学激光强度为1.20 GW/cm且入射THz电场的y分量为10 kV/cm时，产生的二次和三次谐波功率分别为3.96×10 W和7.42×10 W，转换效率分别为3.93×10和7.18×10。与未图案化的硅相比，三次谐波的转换效率提高了700倍。本文提出的配置为需要兼顾高非线性效率和超快可调性的应用提供了一种解决方案。
