biostudies-literatureFujii SRIKENJapan Society for the Promotion of Science4209-4216https://www.ebi.ac.uk/biostudies/studies/S-EPMC11010230biostudies-literatureUnknown24(14)Optical nonlinear processes are indispensable in a wide range of applications, including ultrafast lasers, microscopy, and quantum information technologies. Among the diverse nonlinear processes, second-order effects usually overwhelm the higher-order ones, except in centrosymmetric systems, where the second-order susceptibility vanishes to allow the use of the third-order nonlinearity. Here we demonstrate a hybrid photonic platform whereby the balance between second- and third-order susceptibilities can be tuned flexibly. By decorating ultra-high-<i>Q</i> silica microcavities with atomically thin tungsten diselenide, we observe cavity-enhanced second-harmonic generation and sum-frequency generation with continuous-wave excitation at a power level of only a few hundred microwatts. We show Nano lettersvan der Waals Decoration of Ultra-High-<i>Q</i> Silica Microcavities for χ⁽²⁾-χ⁽³⁾ Hybrid Nonlinear Photonics.PMC11010230JP23H00262JP22K14624JP22K14625JP22H01893JP22K14623Kozawa DYamashita DFong CFFujii SKato YKFang Nfalsevan der Waals Decoration of Ultra-High-<i>Q</i> Silica Microcavities for χ⁽²⁾-χ⁽³⁾ Hybrid Nonlinear Photonics.Optical nonlinear processes are indispensable in a wide range of applications, including ultrafast lasers, microscopy, and quantum information technologies. Among the diverse nonlinear processes, second-order effects usually overwhelm the higher-order ones, except in centrosymmetric systems, where the second-order susceptibility vanishes to allow the use of the third-order nonlinearity. Here we demonstrate a hybrid photonic platform whereby the balance between second- and third-order susceptibilities can be tuned flexibly. By decorating ultra-high-<i>Q</i> silica microcavities with atomically thin tungsten diselenide, we observe cavity-enhanced second-harmonic generation and sum-frequency generation with continuous-wave excitation at a power level of only a few hundred microwatts. We show 2024-01-01T00:00:00Z2024 Apr2025-04-26T20:11:48.829Z2025-04-06T16:20:44.621ZS-EPMC110102303855720510.1021/acs.nanolett.4c00273