Sub-Diffraction Optical Confinement for Enhanced Second-Harmonic Generation in Suspended Thin-Film Lithium Niobate Nano-Cavity

Sub-Diffraction Optical Confinement for Enhanced Second-Harmonic Generation in Suspended Thin-Film Lithium Niobate Nano-Cavity | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article Sub-Diffraction Optical Confinement for Enhanced Second-Harmonic Generation in Suspended Thin-Film Lithium Niobate Nano-Cavity Yuanlin Zheng, Zengya Li, Zhuoran Hu, Weihao Wu, Guangfeng Wang, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7099338/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Confining light beyond diffraction limit is critical in a plethora of important applications, including nano-lasing, sensing, imaging, and particularly nonlinear optics, as it is essential for enhancing conversion efficiency. Plasmonic resonances can provide superior field confinement, but inherently suffer from ohmic losses and thermal damage. Implementing deep-subwavelength optical confinement in all-dielectric materials for enhanced light-matter interactions devoid of these drawbacks is appealing yet challenging. Here, we demonstrate significant enhancement of second-harmonic generation (SHG) in a bowtie nanostructure embedded within suspended thin-film lithium niobate (TFLN) circular Bragg grating (CBG) cavity. The ultrasmall mode volume reaches less than $0.001 (\lambda/n)^3$. The CBG nanocavity exhibits a high normalized conversion efficiency of $0.85 \times 10^{-2}\ \text{cm}^2/\text{GW}$ under the pump intensity of $1\ \text{MW}/\text{cm}^2$. An SHG enhancement factor of approximately 3,720 compared to bare TFLN is realized. This approach paves the way for nonlinear nanodevices for robust sub-diffraction light–matter interaction in an ultra-compact and lossless dielectric platform. Physical sciences/Physics/Optical physics/Nonlinear optics Physical sciences/Optics and photonics/Applied optics/Integrated optics Physical sciences/Physics/Optical physics/Nanophotonics and plasmonics Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryMovie.mp4 SHG signals measured from the bowtie structure embedded in the suspended CBG cavity. supplementary Movie 1 SupplementaryInformation.pdf Supplementary Information Cite Share Download PDF Status: Posted Version 1 posted You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7099338","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":486470390,"identity":"3d1b5e14-74a8-49c7-825c-7c24a02dead3","order_by":0,"name":"Yuanlin 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Plasmonic resonances can provide superior field confinement, but inherently suffer from ohmic losses and thermal damage. Implementing deep-subwavelength optical confinement in all-dielectric materials for enhanced light-matter interactions devoid of these drawbacks is appealing yet challenging. Here, we demonstrate significant enhancement of second-harmonic generation (SHG) in a bowtie nanostructure embedded within suspended thin-film lithium niobate (TFLN) circular Bragg grating (CBG) cavity. The ultrasmall mode volume reaches less than $0.001 (\\lambda/n)^3$. The CBG nanocavity exhibits a high normalized conversion efficiency of $0.85 \\times 10^{-2}\\ \\text{cm}^2/\\text{GW}$ under the pump intensity of $1\\ \\text{MW}/\\text{cm}^2$. An SHG enhancement factor of approximately 3,720 compared to bare TFLN is realized. 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