{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,16]],"date-time":"2026-04-16T16:34:10Z","timestamp":1776357250409,"version":"3.51.2"},"reference-count":31,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2021,10,2]],"date-time":"2021-10-02T00:00:00Z","timestamp":1633132800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100001809","name":"National Natural Science Foundation of China","doi-asserted-by":"publisher","award":["11874122, 11474070, 61327008"],"award-info":[{"award-number":["11874122, 11474070, 61327008"]}],"id":[{"id":"10.13039\/501100001809","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>We report a novel Mach\u2212Zehnder interferometer (MZI) sensor that utilizes a weak one-dimensional field confinement silica waveguide (WCSW). The WCSW has a large horizontal and vertical aspect ratio and low refractive index difference, which features easy preparation and a large evanescent field for achieving high waveguide sensitivity. We experimentally achieved WCSW ultrahigh waveguide sensitivity of 0.94, MZI sensitivity of 44,364 \u03c0\/RIU and a low limit of detection (LOD) of 6.1 \u00d7 10\u22127 RIU.<\/jats:p>","DOI":"10.3390\/s21196600","type":"journal-article","created":{"date-parts":[[2021,10,10]],"date-time":"2021-10-10T21:37:49Z","timestamp":1633901869000},"page":"6600","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Ultrahigh Sensitivity Mach\u2212Zehnder Interferometer Sensor Based on a Weak One-Dimensional Field Confinement Silica Waveguide"],"prefix":"10.3390","volume":"21","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-3042-6526","authenticated-orcid":false,"given":"Chenming","family":"Zhao","sequence":"first","affiliation":[{"name":"Key Lab for Micro and Nanophotonic Structures (Ministry of Education) of Ultra Precision Optical Manufacturing, Shanghai Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China"}]},{"given":"Lei","family":"Xu","sequence":"additional","affiliation":[{"name":"Key Lab for Micro and Nanophotonic Structures (Ministry of Education) of Ultra Precision Optical Manufacturing, Shanghai Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-5131-2846","authenticated-orcid":false,"given":"Liying","family":"Liu","sequence":"additional","affiliation":[{"name":"Key Lab for Micro and Nanophotonic Structures (Ministry of Education) of Ultra Precision Optical Manufacturing, Shanghai Engineering Research Center, Department of Optical Science and Engineering, Fudan University, Shanghai 200433, China"}]}],"member":"1968","published-online":{"date-parts":[[2021,10,2]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"287","DOI":"10.1016\/j.bios.2014.02.049","article-title":"Integrated planar optical waveguide interferometer biosensors: A comparative review","volume":"58","author":"Kozma","year":"2014","journal-title":"Biosens. Bioelectron."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Fern\u00e1ndez Gavela, A., Grajales Garc\u00eda, D., Ramirez, J.C., and Lechuga, L.M. (2016). Last advances in silicon-based optical biosensors. Sensors, 16.","DOI":"10.3390\/s16030285"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"6313","DOI":"10.1109\/JSEN.2015.2455534","article-title":"Enhnaced figure of merit in Fano resonance-based plasmonic refractive index sensor","volume":"15","author":"Zafar","year":"2015","journal-title":"IEEE Sens. J."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"994","DOI":"10.1016\/j.snb.2012.10.008","article-title":"Ultra high sensitivity chemical photonic sensing by Mach\u2013Zehnder interferometer enhanced Vernier-effect","volume":"176","author":"Passaro","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Xie, Y., Zhang, M., and Dai, D. (2020). Design rule of Mach-Zehnder interferometer sensors for ultra-high sensitivity. Sensors, 20.","DOI":"10.3390\/s20092640"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"7","DOI":"10.1007\/s13320-019-0560-y","article-title":"Low-cost and highly sensitive liquid refractive index sensor based on polymer horizontal slot waveguide","volume":"10","author":"Ma","year":"2020","journal-title":"Photonic Sens."},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"1349","DOI":"10.1364\/OL.38.001349","article-title":"Cascaded silicon-on-insulator double-ring sensors operating in high sensitivity transverse-magnetic mode","volume":"38","author":"Jiang","year":"2013","journal-title":"Opt. Lett."},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1395","DOI":"10.1109\/JLT.2005.863333","article-title":"Design and optimization of microring resonators in biochemical sensing applications","volume":"24","author":"Chao","year":"2006","journal-title":"J. Lightwave Technol."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"596","DOI":"10.1364\/OL.33.000596","article-title":"Spiral-path high-sensitivity silicon photonic wire molecular sensor with temperature-independent response","volume":"33","author":"Densmore","year":"2008","journal-title":"Opt. Lett."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"2166","DOI":"10.1063\/1.1508814","article-title":"Demonstration of reverse symmetry waveguide sensing in aqueous solutions","volume":"81","author":"Pedersen","year":"2002","journal-title":"Appl. Phys. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"304","DOI":"10.1016\/S0925-4005(03)00460-X","article-title":"Small-volume refractive index and fluorescence sensor for micro total analytical system (\u00b5-TAS) applications","volume":"94","author":"Zourob","year":"2003","journal-title":"Sens. Actuators B Chem."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"681","DOI":"10.1016\/j.snb.2013.07.053","article-title":"Highly sensitive Mach-Zehnder interferometer biosensor based on silicon nitride slot waveguide","volume":"188","author":"Liu","year":"2013","journal-title":"Sens. Actuators B Chem."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"4442","DOI":"10.1364\/OL.39.004442","article-title":"Evanescent field waveguide sensing with subwavelength grating structures in silicon-on-insulator","volume":"39","author":"Cheben","year":"2014","journal-title":"Opt. Lett."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"9844","DOI":"10.1364\/OE.16.009844","article-title":"A semi-weakly confined erbium-doped waveguide amplifier with double-layered buffer\/cladding","volume":"16","author":"Tang","year":"2008","journal-title":"Opt. Express"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"2200511","DOI":"10.1109\/JPHOT.2020.3007721","article-title":"Weak one-dimensional field confinement silica waveguides","volume":"12","author":"Zhao","year":"2020","journal-title":"IEEE Photonics J."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"13010","DOI":"10.1039\/D0TC02700F","article-title":"Photo-bleaching of optical waveguide polymers with dipolar chromophores to improve their sensitivity for explosive vapor detection","volume":"8","author":"Zheng","year":"2020","journal-title":"J. Mater. Chem. C"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.snb.2018.09.070","article-title":"Design of on-chip hybrid plasmonic Mach-Zehnder interferometer for temperature and concentration detection of chemical solution","volume":"279","author":"Ghosh","year":"2019","journal-title":"Sens. Actuators B Chem."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"209","DOI":"10.1364\/JOSAB.6.000209","article-title":"Sensitivity of grating couplers as integrated-optical chemical sensors","volume":"6","author":"Tiefenthaler","year":"1989","journal-title":"J. Opt. Soc. Am. B"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1355","DOI":"10.1109\/JSEN.2019.2944391","article-title":"Sensitivity enhancement of silicon strip waveguide ring resonator by incorporating a thin metal film","volume":"20","author":"Butt","year":"2020","journal-title":"IEEE Sens. J."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"4228","DOI":"10.1063\/1.1604476","article-title":"Thermo-optic properties of sol-gel-fabricated organic\u2013inorganic hybrid waveguides","volume":"94","author":"Wang","year":"2003","journal-title":"J. Appl. Phys."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"3172","DOI":"10.1364\/OE.16.003172","article-title":"Low-loss channel waveguides and Y-splitter formed by ion-exchange in silica-on-silicon","volume":"16","author":"He","year":"2008","journal-title":"Opt. Express"},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"19488","DOI":"10.1364\/OE.21.019488","article-title":"Porous silicon integrated Mach-Zehnder interferometer waveguide for biological and chemical sensing","volume":"21","author":"Kim","year":"2013","journal-title":"Opt. Express"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"27910","DOI":"10.1364\/OE.22.027910","article-title":"Single-channel Mach-Zehnder interferometric biochemical sensor based on two-lateral-mode spiral waveguide","volume":"22","author":"Liu","year":"2014","journal-title":"Opt. Express"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"2640","DOI":"10.1364\/OE.20.002640","article-title":"Thermal independent silicon-nitride slot waveguide biosensor with high sensitivity","volume":"20","author":"Tu","year":"2012","journal-title":"Opt. Express"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"1124","DOI":"10.1364\/AO.55.001124","article-title":"Asymmetric Mach-Zehnder interferometers without an interaction window in polymer foils for refractive index sensing","volume":"55","author":"Hofmann","year":"2016","journal-title":"Appl. Opt."},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Bastos, A., Vicente, C., Oliveira-Silva, R., Silva, N., Tac\u00e3o, M., Costa, J., Lima, M., Andr\u00e9, P., Ferreira, R., and Bastos, A.R. (2018). Integrated optical Mach-Zehnder interferometer based on organic-inorganic hybrids for photonics-on-a-chip biosensing applications. Sensors, 18.","DOI":"10.3390\/s18030840"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"3700108","DOI":"10.1109\/JPHOT.2013.2251873","article-title":"Grating couplers integrated on Mach\u2013Zehnder interferometric biosensors operating in the visible range","volume":"5","author":"Duval","year":"2013","journal-title":"IEEE Photonics J."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"7195","DOI":"10.1364\/OE.20.007195","article-title":"All-optical phase modulation for integrated interferometric biosensors","volume":"20","author":"Dante","year":"2012","journal-title":"Opt. Express"},{"key":"ref_29","doi-asserted-by":"crossref","unstructured":"Chalyan, T., Guider, R., Pasquardini, L., Zanetti, M., Falke, F., Schreuder, E., Heideman, R., Pederzolli, C., and Pavesi, L. (2016). Asymmetric Mach\u2013Zehnder Interferometer Based Biosensors for Aflatoxin M1 Detection. Biosensors, 6.","DOI":"10.3390\/bios6010001"},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"3598","DOI":"10.1364\/OL.34.003598","article-title":"Silicon photonic wire biosensor array for multiplexed real-time and label-free molecular detection","volume":"34","author":"Densmore","year":"2009","journal-title":"Opt. Lett."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"2787","DOI":"10.1364\/OL.426787","article-title":"Ultra-sensitive silicon temperature sensor based on cascaded Mach-Zehnder interferometers","volume":"46","author":"Ding","year":"2021","journal-title":"Opt. Lett."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/19\/6600\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T07:08:58Z","timestamp":1760166538000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/21\/19\/6600"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2021,10,2]]},"references-count":31,"journal-issue":{"issue":"19","published-online":{"date-parts":[[2021,10]]}},"alternative-id":["s21196600"],"URL":"https:\/\/doi.org\/10.3390\/s21196600","relation":{},"ISSN":["1424-8220"],"issn-type":[{"value":"1424-8220","type":"electronic"}],"subject":[],"published":{"date-parts":[[2021,10,2]]}}}