Deng Junhong, Tang Yutao, Chen Shumei, Li Kingfai, Zayats Anatoly V, Li Guixin
Department of Materials Science and Engineering, Shenzhen Institute for Quantum Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
School of Science, Harbin Institute of Technology (Shenzhen), Shenzen 518055, China.
Nano Lett. 2020 Jul 8;20(7):5421-5427. doi: 10.1021/acs.nanolett.0c01810. Epub 2020 Jun 23.
Nonlinear frequency conversion at the nanoscale is important for many applications in free space and integrated photonics. In epsilon-near-zero (ENZ) materials, second-harmonic generation (SHG) is significantly enhanced but the oblique incidence is required to address nonlinearity. To circumvent this constraint, we design a hybrid metasurface consisting of plasmonic nanostructures on an ENZ nanofilm generating strongly enhanced SHG at normal incidence in transmission. We show that the Au meta-atoms on an indium-tin-oxide (ITO) layer provide an approximately 10-fold experimentally measured SHG enhancement at normal incidence at the fundamental wavelength near the ENZ condition of ITO. This giant enhancement stems from reshaping the vectorial properties of the incident light near the Au nanostructures and its increased coupling to the ENZ film. The proposed hybrid ENZ metasurface offers a promising platform for developing ultracompact and efficient nonlinear optical sources at the nanoscale.
纳米尺度的非线性频率转换对于自由空间和集成光子学中的许多应用都很重要。在近零介电常数（ENZ）材料中，二次谐波产生（SHG）得到显著增强，但需要斜入射来处理非线性问题。为了规避这一限制，我们设计了一种混合超表面，它由ENZ纳米薄膜上的等离子体纳米结构组成，在透射时垂直入射时能产生强烈增强的SHG。我们表明，在铟锡氧化物（ITO）层上的金超原子在接近ITO的ENZ条件的基波波长下垂直入射时，实验测量的SHG增强约10倍。这种巨大的增强源于在金纳米结构附近重塑入射光的矢量特性及其与ENZ薄膜增加的耦合。所提出的混合ENZ超表面为在纳米尺度上开发超紧凑和高效的非线性光源提供了一个有前景的平台。
