Near-field Probing of the Local Density of Optical States Enhanced by Bound States in the Continuum in Nonlocal Metasurfaces

Near-field Probing of the Local Density of Optical States Enhanced by Bound States in the Continuum in Nonlocal Metasurfaces | 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 Near-field Probing of the Local Density of Optical States Enhanced by Bound States in the Continuum in Nonlocal Metasurfaces Jie Ji, Jose Sanchez-Gil, Djero Peeters, Wouter Holman, Thanh Xuan Hoang, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6306367/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 24 Nov, 2025 Read the published version in Nature Communications → Version 1 posted You are reading this latest preprint version Abstract Bound States in the Continuum (BICs) are exotic optical modes that remain decoupled from free-space radiation. Symmetry-protected BICs in infinite metasurfaces provide unique opportunities to tailor light–matter interactions in extended photonic structures. One of the most important properties of these structures is the partial local density of optical states (PLDOS), which describes the number of electromagnetic modes available for a photon to occupy at a specific position, frequency, and polarization. It quantifies how the surrounding photonic environment modifies the ability of light to couple with matter at a given location. Here, we employ a terahertz near-field microscope with dual local probes to directly excite and detect quasi-BICs in finite metasurfaces with inversion symmetry, which support a symmetry-protected BIC in their infinite counterpart. Our results provide the first direct evidence of a large PLDOS enhancement associated with BICs and quasi-BICs in finite metasurfaces. As the metasurface size increases, the quasi-BIC evolves into the BIC, and the quality factor (Q) diverges while the PLDOS saturates at a finite value. This result reflects an upper limit for enhanced light-matter interaction by BICs. Our findings pave the way for next-generation on-chip metasurfaces with maximum light-matter interaction strengths. Physical sciences/Optics and photonics/Optical materials and structures/Microresonators Physical sciences/Optics and photonics/Optical materials and structures/Microresonators Physical sciences/Optics and photonics/Optical physics/Terahertz optics Physical sciences/Optics and photonics/Optical physics/Terahertz optics Physical sciences/Physics/Optical physics/Sub-wavelength optics Full Text Additional Declarations There is NO Competing Interest. Supplementary Files Supplementary.pdf Supplementary Cite Share Download PDF Status: Published Journal Publication published 24 Nov, 2025 Read the published version in Nature Communications → 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. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-6306367","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":531101409,"identity":"6d93e2c9-3d4c-442f-a13a-6e85cd306a25","order_by":0,"name":"Jie 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Symmetry-protected BICs in infinite metasurfaces provide unique opportunities to tailor light–matter interactions in extended photonic structures. One of the most important properties of these structures is the partial local density of optical states (PLDOS), which describes the number of electromagnetic modes available for a photon to occupy at a specific position, frequency, and polarization. It quantifies how the surrounding photonic environment modifies the ability of light to couple with matter at a given location. Here, we employ a terahertz near-field microscope with dual local probes to directly excite and detect quasi-BICs in finite metasurfaces with inversion symmetry, which support a symmetry-protected BIC in their infinite counterpart. Our results provide the first direct evidence of a large PLDOS enhancement associated with BICs and quasi-BICs in finite metasurfaces. As the metasurface size increases, the quasi-BIC evolves into the BIC, and the quality factor (Q) diverges while the PLDOS saturates at a finite value. This result reflects an upper limit for enhanced light-matter interaction by BICs. 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