Transformation optics enabled ultra-sharp bending for multimode micro-ring resonators

Transformation optics enabled ultra-sharp bending for multimode micro-ring resonators | 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 Transformation optics enabled ultra-sharp bending for multimode micro-ring resonators Yuan Yu, Shuai Cui, Zhao Pan, Jiayao Su, Lifeng Cai, Dingshan Gao, and 2 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-6139738/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 Achieving ultra-low propagation loss in optical waveguides is crucial for boosting the quality factor of micro-resonators and large-scale photonic integration. Much effort has been paid to design and fabricate multimode waveguides to reduce the scattering loss at waveguide surfaces. Although various adiabatic curves, including Euler bends, hyperbolic tangent functions, and Bezier curves have been proposed to ensure fundamental mode transmission and reduce bending radius, the footprint is still large because of large waveguide dimensions. In this study, transformation optics (TO) is proposed to obtain exceptionally sharp bending for multimode waveguide micro-ring resonators (MRRs) based on silicon. Results show that an intrinsic quality factor (Q) of 13 ± 1.5 million for the silicon-based MRR is obtained, which indicates that the propagation loss of fabricated silicon waveguide is only 3.8 ± 0.33 dB/m. Notably, only TE0 mode is excited and inter-mode crosstalk is effectively suppressed through adiabatic mode evolution. Thanks to the waveguide mode converter designed by TO, the bending radius of the MRR with 2-µm-wide waveguide is reduced to an unprecedented level of only 10 µm, which is comparable to that of single mode waveguide. The fabricated MRR is also employed in microwave photonics, achieving ultra-narrow microwave filtering with wideband tunability, thus enabling high resolution mode selection in optoelectronic oscillator (OEO) with high flexibility. Furthermore, we also propose a novel method of stabilizing the resonant wavelength of MRR by employing an OEO. Results show that the wavelength stability is improved by two orders of magnitude. This research provides a versatile design methodology for ultrahigh-Q multimode MRRs with ultra-compact size. These advances open new possibilities for applications in microwave photonics, nonlinear photonics, large-scale photonic integration, and quantum photonics. Physical sciences/Optics and photonics/Optical physics/Transformation optics Physical sciences/Optics and photonics/Optical materials and structures/Silicon photonics Full Text Additional Declarations There is NO Competing Interest. Supplementary Files SupplementaryMaterials.pdf Supplementary Info 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. 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-6139738","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":430739925,"identity":"0f5a99e0-3fde-43ed-aec3-0d95b5c42c44","order_by":0,"name":"Yuan 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