Giant enhancement of optical nonlinearity in two-dimensional materials by multiphoton-excitation resonance energy transfer from quantum dots

Funding Information: This work was supported by the National Natural Science Foundation of China (52025023, 51991342, 52021006, 51722204, 51972041, 51972042, 51672007, 11974023, 12025407 and 11934003), the National Key R&D Program of China (2016YFA0300903 and 2016YFA0300804), Beijing Natural Science Foundation (JQ19004), Beijing Excellent Talents Training Support (2017000026833ZK11), the Strategic Priority Research Program of the Chinese Academy of Sciences (XDB33000000), Beijing Municipal Science & Technology Commission (Z191100007219005), Beijing Graphene Innovation Program (Z181100004818003), Key-Area Research and Development Program of GuangDong Province (2020B010189001, 2019B010931001 and 2018B030327001), the Science, Technology and Innovation Commission of Shenzhen Municipality (KYTDPT20181011104202253), Bureau of Industry and Information Technology of Shenzhen (Graphene platform 201901161512), The Pearl River Talent Recruitment Program of Guangdong Province (2019ZT08C321), National Equipment Program of China (ZDYZ2015-1) and the China Postdoctoral Science Foundation (2020M680177). Publisher Copyright: © 2021, The Author(s), under exclusive licence to Springer Nature Limited. Copyright: Copyright 2021 Elsevier B.V., All rights reserved. Colloidal quantum dots are promising photoactive materials that enable plentiful photonic and optoelectronic applications ranging from lasers, displays and photodetectors to solar cells1–9. However, these applications mainly utilize the linear optical properties of quantum dots, and their great potential in the broad nonlinear optical regime is still waiting for full exploration10–12. Here, we demonstrate that a simple coating of a sub-200-nm-thick quantum dot film on two-dimensional materials can significantly enhance their nonlinear optical responses (second, third and fourth harmonic generation) by more than three orders of magnitude. Systematic experimental results indicate that this enhancement is driven by a non-trivial mechanism of multiphoton-excitation resonance energy transfer, where the quantum dots directly deliver their strongly absorbed multiphoton energy to the adjacent two-dimensional materials by a remote dipole–dipole coupling. Our findings could expand the applications of quantum dots in many exciting areas beyond linear optics, such as nonlinear optical signal processing, multiphoton imaging and ultracompact nonlinear optical elements.