{"paper_id":"0faccb31-41f2-4570-8d5f-3b15c2161eaf","body_text":"An Ultrasensitive and Broadband Micro-Ring based Optomechanical Ultrasound Sensor for Photoacoustic Imaging | 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 An Ultrasensitive and Broadband Micro-Ring based Optomechanical Ultrasound Sensor for Photoacoustic Imaging Yan Cai, Chao Xu, Zijie Zhao, Xu Chen, Shuxiao Wang, Wei Wang, and 5 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7670036/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 Recent advances in ultrasonography and photoacoustic tomography call for ultrasound sensors with high sensitivity, broad bandwidth, miniaturized footprint, and scalability. Conventional piezoelectric transducer is fundamentally constrained by limited sensitivity, element density, and system integration complexity. In this work, we introduce a micro-ring based optomechanical ultrasound sensor using a novel SiN/Si hybrid waveguide structure with a 30 nm air gap engineered within the sensing region. The micro-ring resonator exhibits a high-quality factor of 4.8×10⁴ and a free spectral range (FSR) of 18 nm at the wavelength of 1580 nm. With a compact diameter of 18 µm, the sensor achieves a record-low noise-equivalent pressure below 0.64 mPa Hz⁻¹/² over a frequency range of 2–30 MHz, which is three orders of magnitude better than piezoelectric devices of the same size. Furthermore, the device enables photoacoustic signal detection at the depth up to 10 cm and offers a wide acceptance angle of ± 20° for frequencies up to 20 MHz. High-resolution photoacoustic tomography of a graphite pencil lead is demonstrated, revealing sub-millimetric structural details. We also show an 8-element sensor array employing wavelength-division multiplexing that allows parallel readout through a single optical fiber, effectively overcoming the wiring-density bottleneck inherent in conventional piezoelectric arrays. With its exceptional sensitivity, broad bandwidth, and inherent compatibility with chip-scale multiplexing, this platform offers a transformative solution for minimally invasive photoacoustic endoscopy, high-resolution imaging systems, and highly dense ultrasound sensor networks. Physical sciences/Optics and photonics/Optical physics/Micro-optics Physical sciences/Optics and photonics/Applied optics/Optical sensors Full Text Additional Declarations There is no conflict of interest Supplementary Files MicroRingbasedOptomechanicalUltrasoundSensorMINEsupplementary.docx Micro-Ring based Optomechanical Ultrasound Sensor_MINE_supplementary 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-7670036\",\"acceptedTermsAndConditions\":true,\"allowDirectSubmit\":true,\"archivedVersions\":[],\"articleType\":\"Article\",\"associatedPublications\":[],\"authors\":[{\"id\":539640298,\"identity\":\"1d68a0c1-3710-4b2e-a7c2-b78ec910ef0c\",\"order_by\":0,\"name\":\"Yan 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Conventional piezoelectric transducer is fundamentally constrained by limited sensitivity, element density, and system integration complexity. In this work, we introduce a micro-ring based optomechanical ultrasound sensor using a novel SiN/Si hybrid waveguide structure with a 30 nm air gap engineered within the sensing region. The micro-ring resonator exhibits a high-quality factor of 4.8\\u0026times;10⁴ and a free spectral range (FSR) of 18 nm at the wavelength of 1580 nm. With a compact diameter of 18 \\u0026micro;m, the sensor achieves a record-low noise-equivalent pressure below 0.64 mPa Hz⁻\\u0026sup1;/\\u0026sup2; over a frequency range of 2\\u0026ndash;30 MHz, which is three orders of magnitude better than piezoelectric devices of the same size. Furthermore, the device enables photoacoustic signal detection at the depth up to 10 cm and offers a wide acceptance angle of \\u0026plusmn;\\u0026thinsp;20\\u0026deg; for frequencies up to 20 MHz. High-resolution photoacoustic tomography of a graphite pencil lead is demonstrated, revealing sub-millimetric structural details. We also show an 8-element sensor array employing wavelength-division multiplexing that allows parallel readout through a single optical fiber, effectively overcoming the wiring-density bottleneck inherent in conventional piezoelectric arrays. With its exceptional sensitivity, broad bandwidth, and inherent compatibility with chip-scale multiplexing, this platform offers a transformative solution for minimally invasive photoacoustic endoscopy, high-resolution imaging systems, and highly dense ultrasound sensor networks.\\u003c/p\\u003e\",\"manuscriptTitle\":\"An Ultrasensitive and Broadband Micro-Ring based Optomechanical Ultrasound Sensor for Photoacoustic Imaging\",\"msid\":\"\",\"msnumber\":\"\",\"nonDraftVersions\":[{\"code\":1,\"date\":\"2025-11-13 16:43:47\",\"doi\":\"10.21203/rs.3.rs-7670036/v1\",\"editorialEvents\":[{\"type\":\"communityComments\",\"content\":0}],\"status\":\"published\",\"journal\":{\"display\":true,\"email\":\"info@researchsquare.com\",\"identity\":\"researchsquare\",\"isNatureJournal\":false,\"hasQc\":true,\"allowDirectSubmit\":true,\"externalIdentity\":\"\",\"sideBox\":\"\",\"snPcode\":\"\",\"submissionUrl\":\"/submission\",\"title\":\"Research Square\",\"twitterHandle\":\"researchsquare\",\"acdcEnabled\":true,\"dfaEnabled\":false,\"editorialSystem\":\"\",\"reportingPortfolio\":\"\",\"inReviewEnabled\":false,\"inReviewRevisionsEnabled\":true}}],\"origin\":\"\",\"ownerIdentity\":\"174e8fb4-bc54-4c0e-915c-a7ca6364e02c\",\"owner\":[],\"postedDate\":\"November 13th, 2025\",\"published\":true,\"recentEditorialEvents\":[],\"rejectedJournal\":[],\"revision\":\"\",\"amendment\":\"\",\"status\":\"posted\",\"subjectAreas\":[{\"id\":57392158,\"name\":\"Physical sciences/Optics and photonics/Optical physics/Micro-optics\"},{\"id\":57392159,\"name\":\"Physical sciences/Optics and photonics/Applied optics/Optical sensors\"}],\"tags\":[],\"updatedAt\":\"2025-12-10T01:05:25+00:00\",\"versionOfRecord\":[],\"versionCreatedAt\":\"2025-11-13 16:43:47\",\"video\":\"\",\"vorDoi\":\"\",\"vorDoiUrl\":\"\",\"workflowStages\":[]},\"version\":\"v1\",\"identity\":\"rs-7670036\",\"journalConfig\":\"researchsquare\"},\"__N_SSP\":true},\"page\":\"/article/[identity]/[[...version]]\",\"query\":{\"redirect\":\"/article/rs-7670036\",\"identity\":\"rs-7670036\",\"version\":[\"v1\"]},\"buildId\":\"8U1c8b4HqxoKbykW_rLl7\",\"isFallback\":false,\"isExperimentalCompile\":false,\"dynamicIds\":[84888],\"gssp\":true,\"scriptLoader\":[]}","source_license":"CC-BY-4.0","license_restricted":false}