Water Monolayers: An Overlooked Loss Mechanism in Mid-Infrared Photonics

Water Monolayers: An Overlooked Loss Mechanism in Mid-Infrared Photonics | 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 Water Monolayers: An Overlooked Loss Mechanism in Mid-Infrared Photonics Jana Jágerská, Antonia Torres-Cubillo, Martin Feiler, Roman Zakoldaev, and 4 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9284522/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 Mid-infrared (MIR) photonics promises transformative advances in environmental monitoring, chemical sensing and molecular spectroscopy, yet its practical deployment remains hindered by the persistently high propagation losses. Here we identify and quantify a previously underappreciated but dominant loss mechanism in air-clad MIR photonic devices: light absorption in water monolayers formed on the device surface from ambient humidity. Although only a few molecular layers thick, such layers become an appreciable source of loss as adsorbed water exhibits absorption coefficients in the MIR that are orders of magnitude larger than in the visible and near-infrared, where most photonic platforms were originally developed. We show that the formation of merely one to several monolayers is sufficient to induce propagation losses of tens of decibels per centimeter in sensing-optimized waveguides, in some cases completely suppressing transmission. Using silicon-on-insulator slot waveguides and suspended silicon nitride waveguides operating near 3.27 µm and 4.35 µm, we correlate relative humidity, surface chemistry, and waveguide geometry with measured propagation losses. The effect is strongly wavelength- and geometry-dependent and is amplified in sensing-optimized structures with enhanced modal overlap at air interfaces. We further demonstrate that the observed behaviour can be accurately captured by incorporating nanometre-scale water/ice layers into standard electromagnetic band-structure models, providing a predictive design tool. Physical sciences/Optics and photonics/Applied optics/Mid-infrared photonics Physical sciences/Optics and photonics/Optical materials and structures Full Text Additional Declarations There is NO Competing Interest. Supplementary Files Watermonolayersupplementsubmission.pdf Water Monolayers: An Overlooked Loss Mechanism in Mid-Infrared Photonics - Supplement 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. 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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-9284522","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":615527750,"identity":"d6bc7309-e37f-48df-8043-1f4dfd3318a4","order_by":0,"name":"Jana Jágerská","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA5klEQVRIiWNgGAWjYBACxgYQyQNmMzMwVECZJGg5w8BDWA8SYGZgbGMgbA1z+9mDHxhk7Oz6pY8/Nvg577CMPQPvwQd4HdaTlyzBwJOcPLMvxzixd9thoMP4kg3wamnIMQBqYU42OMPDfIAXrIXHTAKvlv43xj8YeOqT7c+wPz74dw4xWmbkABXwHLYz4GEwTuZtIErLGzOLBJ7jCRJneIyNZY6l8/Ac5jHG6xfD/hzjGx97qu35e9gfS76psbZnb+8xfIBXSwOQSOxhSGyACzHjUw8E8mDyB4M9AXWjYBSMglEwkgEAIok9q9NZH1cAAAAASUVORK5CYII=","orcid":"https://orcid.org/0000-0003-4330-9596","institution":"UiT The Arctic University of Norway","correspondingAuthor":true,"prefix":"","firstName":"Jana","middleName":"","lastName":"Jágerská","suffix":""},{"id":615527751,"identity":"d89fca30-75a5-48d6-a136-3eefb799829a","order_by":1,"name":"Antonia Torres-Cubillo","email":"","orcid":"","institution":"UiT The Arctic University of Norway / University of Málaga","correspondingAuthor":false,"prefix":"","firstName":"Antonia","middleName":"","lastName":"Torres-Cubillo","suffix":""},{"id":615527752,"identity":"9d175abb-55b7-4752-acdb-a67e6a45b80b","order_by":2,"name":"Martin Feiler","email":"","orcid":"","institution":"UiT The Arctic University of Norway / Slovak University of Technology in Bratislava","correspondingAuthor":false,"prefix":"","firstName":"Martin","middleName":"","lastName":"Feiler","suffix":""},{"id":615527753,"identity":"013767ba-d85a-4281-be1c-25041a23c89b","order_by":3,"name":"Roman Zakoldaev","email":"","orcid":"","institution":"UiT The Arctic University of Norway","correspondingAuthor":false,"prefix":"","firstName":"Roman","middleName":"","lastName":"Zakoldaev","suffix":""},{"id":615527754,"identity":"9641b5f8-dc70-40db-b6c3-dbff6cc23513","order_by":4,"name":"Jehona Salaj","email":"","orcid":"","institution":"UiT The Arctic University of Norway","correspondingAuthor":false,"prefix":"","firstName":"Jehona","middleName":"","lastName":"Salaj","suffix":""},{"id":615527755,"identity":"32ee008e-f77c-4044-8b3f-2360f16a6be0","order_by":5,"name":"Noémie Mestre","email":"","orcid":"","institution":"UiT The Arctic University of Norway","correspondingAuthor":false,"prefix":"","firstName":"Noémie","middleName":"","lastName":"Mestre","suffix":""},{"id":615527756,"identity":"bb6fb4ec-4018-46bf-8b0c-c9c8d34ceaf8","order_by":6,"name":"Sebastian Alberti","email":"","orcid":"","institution":"The Arctic University of Norway","correspondingAuthor":false,"prefix":"","firstName":"Sebastian","middleName":"","lastName":"Alberti","suffix":""},{"id":615527757,"identity":"39156afe-3b0d-4a3e-96a4-904c809b4105","order_by":7,"name":"Henock Yallew","email":"","orcid":"","institution":"The Arctic University of Norway","correspondingAuthor":false,"prefix":"","firstName":"Henock","middleName":"","lastName":"Yallew","suffix":""}],"badges":[],"createdAt":"2026-03-31 22:05:50","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9284522/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9284522/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":106093766,"identity":"3ea4724c-29d2-4972-bc62-ad9742721eec","added_by":"auto","created_at":"2026-04-03 11:39:02","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1570005,"visible":true,"origin":"","legend":"Article File","description":"","filename":"Watermonolayermanuscriptsubmission.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9284522/v1_covered_9789e9a5-d99b-45dd-99cf-2b15f46d6d41.pdf"},{"id":105970111,"identity":"529cee51-04df-4570-ad51-9ea716acca33","added_by":"auto","created_at":"2026-04-02 03:19:23","extension":"pdf","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":1270819,"visible":true,"origin":"","legend":"Water Monolayers: An Overlooked Loss Mechanism in Mid-Infrared Photonics - 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