Full-color enhanced second harmonic generation using rainbow trapping in ultrathin hyperbolic metamaterials

• Published in: Nature communications Vol. 12; no. 1; p. 6425
• Main Authors: Li, Junhao, Hu, Guangwei, Shi, Lina, He, Nan, Li, Daqian, Shang, Qiuyu, Zhang, Qing, Fu, Huange, Zhou, Linlin, Xiong, Wei, Guan, Jianguo, Wang, Jian, He, Sailing, Chen, Lin
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 05.11.2021; Nature Publishing Group; Nature Portfolio
• Subjects: 147/135; 639/624/399/1015; 639/624/400/385; Arrays; Bandwidths; Broadband; Color; Computer engineering; Humanities and Social Sciences; Laboratories; Light; Localization; Luminous intensity; Metamaterials; multidisciplinary; Multilayers; Nanopatterning; Nonlinear systems; Nonlinearity; Optics; Rainbows; Science; Science (multidisciplinary); Second harmonic generation; Trapping; Wavelength; Zinc oxide
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-26818-3

Metasurfaces have provided a promising approach to enhance the nonlinearity at subwavelength scale, but usually suffer from a narrow bandwidth as imposed by sharp resonant features. Here, we counterintuitively report a broadband, enhanced second-harmonic generation, in nanopatterned hyperbolic metamaterials. The nanopatterning allows the direct access of the mode with large momentum, rendering the rainbow light trapping, i.e. slow light in a broad frequency, and thus enhancing the local field intensity for boosted nonlinear light-matter interactions. For a proof-of-concept demonstration, we fabricated a nanostructured Au/ZnO multilayer, and enhanced second harmonic generation can be observed within the visible wavelength range (400-650 nm). The enhancement factor is over 50 within the wavelength range of 470-650 nm, and a maximum conversion efficiency of 1.13×10 −6 is obtained with a pump power of only 8.80 mW. Our results herein offer an effective and robust approach towards the broadband metasurface-based nonlinear devices for various important technologies. Though metamaterials enhance nonlinear light-matter interactions due to their resonant features, these materials typically show a narrow spectral bandwidth. Here, the authors report broadband enhanced second-harmonic generation in patterned multilayer hyperbolic metamaterial arrays.