Ultrathin quantum light source with van der Waals NbOCl2 crystal · SciRah

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Ultrathin quantum light source with van der Waals NbOCl2 crystal

Qiangbing Guo^{a b c d}✉, Xiao‐Zhuo Qi^{e f}, Lishu Zhang^g, Meng Gao^h, Sanlue Huⁱ, Wenju Zhou^{h j k}, Wenjie Zang^d, Xiaoxu Zhao^l, Junyong Wang^{g m}, Bingmin Yan^k, Mingquan Xu^h, Yunkun Wu

Nature Nature Portfolio2023-01-04 328 citations52 references

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Abstract

A van der Waals crystal, niobium oxide dichloride, with vanishing interlayer electronic coupling and considerable monolayer-like excitonic behaviour in the bulk, as well as strong and scalable second-order optical nonlinearity, is discovered, which enables a high-performance quantum light source. Interlayer electronic coupling in two-dimensional materials enables tunable and emergent properties by stacking engineering. However, it also results in significant evolution of electronic structures and attenuation of excitonic effects in two-dimensional semiconductors as exemplified by quickly degrading excitonic photoluminescence and optical nonlinearities in transition metal dichalcogenides when monolayers are stacked into van der Waals structures. Here we report a van der Waals crystal, niobium oxide dichloride (NbOCl_2), featuring vanishing interlayer electronic coupling and monolayer-like excitonic behaviour in the bulk form, along with a scalable second-harmonic generation intensity of up to three orders higher than that in monolayer WS_2. Notably, the strong second-order nonlinearity enables correlated parametric photon pair generation, through a spontaneous parametric down-conversion (SPDC) process, in flakes as thin as about 46 nm. To our knowledge, this is the first SPDC source unambiguously demonstrated in two-dimensional layered materials, and the thinnest SPDC source ever reported. Our work opens an avenue towards developing van der Waals material-based ultracompact on-chip SPDC sources as well as high-performance photon modulators in both classical and quantum optical technologies^ 1 – 4 .

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^aCentre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore. qbguo90@hotmail.com
^bDepartment of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore. qbguo90@hotmail.com
^cDepartment of Materials Science and Engineering, National University of Singapore, Singapore, Singapore. qbguo90@hotmail.com
^dDepartment of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore
^eCAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, China
^fCAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, China
^gDepartment of Physics, National University of Singapore, Singapore, Singapore
^hSchool of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, China
ⁱWuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan, China
^jCAS Center for Excellence in Topological Quantum Computation, University of Chinese Academy of Sciences, Beijing, China
^kCenter for High Pressure Science and Technology Advanced Research, Beijing, China
^lSchool of Materials Science and Engineering, Peking University, Beijing, China
^mCentre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore
ⁿResearch Laboratory for Quantum Materials, Singapore University of Technology and Design, Singapore, Singapore
^oHefei National Laboratory, University of Science and Technology of China, Hefei, China
^pCAS Center for Excellence in Quantum Information and Quantum Physics, University of Science and Technology of China, Hefei, China. renxf@ustc.edu.cn
^qCAS Key Laboratory of Quantum Information, University of Science and Technology of China, Hefei, China. renxf@ustc.edu.cn
^rHefei National Laboratory, University of Science and Technology of China, Hefei, China. renxf@ustc.edu.cn
^sCentre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore. chengwei.qiu@nus.edu.sg
^tDepartment of Electrical and Computer Engineering, National University of Singapore, Singapore, Singapore. chengwei.qiu@nus.edu.sg
^uDepartment of Materials Science and Engineering, National University of Singapore, Singapore, Singapore. stephen.pennycook@cantab.net
^vSchool of Physical Sciences and CAS Key Laboratory of Vacuum Physics, University of Chinese Academy of Sciences, Beijing, China. stephen.pennycook@cantab.net
^wCentre for Advanced 2D Materials and Graphene Research Centre, National University of Singapore, Singapore, Singapore. phyweets@nus.edu.sg
^xDepartment of Physics, National University of Singapore, Singapore, Singapore. phyweets@nus.edu.sg
✉Corresponding author