Lyu Xiaodan, Kallioniemi Leevi, Cai Hongbing, An Liheng, Duan Ruihuan, Wu Shuin Jian, Tan Qinghai, Zhang Chusheng, He Ruihua, Miao Yansong, Liu Zheng, Ling Alexander, Zúñiga-Perez Jesus, Gao Weibo
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore, Singapore.
Majulab, International Research Laboratory IRL 3654, CNRS, Université Côte d'Azur, Sorbonne Université, National University of Singapore, Nanyang Technological University, Singapore, Singapore.
Nat Commun. 2025 May 29;16(1):4987. doi: 10.1038/s41467-025-58449-3.
Understanding and controlling nonlinear processes is crucial for engineering light-matter interaction and generating non-classical light. A significant challenge in ultra-thin nonlinear materials is the marked diminution of the nonlinear conversion efficiency due to the reduced light-matter interaction length and, in many cases, the centrosymmetric crystalline structures. Here we relax these limitations and report a giant boost of classical and quantum nonlinear processes in ultrathin van der Waals materials. Specifically, with a metal-nonlinear material heterostructure we enhance classical second-harmonic generation in h-BN flakes by two orders of magnitude. Moreover, we have engineered a metal-SiO-nonlinear material heterostructure resulting in a remarkable two orders of magnitude augmentation of the quantum spontaneous parametric down-conversion (SPDC) in NbOCl flakes. Notably, we demonstrate SPDC in a 16 nm-thick NbOCl flake integrated into the proposed structure. These findings simplify on-chip quantum state engineering and accelerate the use of van der Waals materials in nonlinear optoelectronics.
理解和控制非线性过程对于工程化光与物质的相互作用以及产生非经典光至关重要。超薄非线性材料面临的一个重大挑战是，由于光与物质相互作用长度的缩短，以及在许多情况下中心对称的晶体结构，非线性转换效率显著降低。在此，我们放宽了这些限制，并报告了超薄范德华材料中经典和量子非线性过程的巨大提升。具体而言，通过金属-非线性材料异质结构，我们将h-BN薄片中的经典二次谐波产生增强了两个数量级。此外，我们设计了一种金属-二氧化硅-非线性材料异质结构，使得NbOCl薄片中的量子自发参量下转换（SPDC）显著增强了两个数量级。值得注意的是，我们在集成到所提出结构中的16纳米厚的NbOCl薄片中演示了SPDC。这些发现简化了片上量子态工程，并加速了范德华材料在非线性光电子学中的应用。
