{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,12]],"date-time":"2025-10-12T04:17:58Z","timestamp":1760242678385,"version":"build-2065373602"},"reference-count":25,"publisher":"MDPI AG","issue":"3","license":[{"start":{"date-parts":[[2016,3,3]],"date-time":"2016-03-03T00:00:00Z","timestamp":1456963200000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A comparative study is given for the sensitivity of several typical Si nanophotonic waveguides, including SOI (silicon-on-insulator) nanowires, nanoslot waveguides, suspended Si nanowires, and nanofibers. The cases for gas sensing (ncl ~ 1.0) and liquid sensing (ncl ~ 1.33) are considered. When using SOI nanowires (with a SiO2 buffer layer), the sensitivity for liquid sensing (S ~ 0.55) is higher than that for gas sensing (S ~ 0.35) due to lower asymmetry in the vertical direction. By using SOI nanoslot waveguides, suspended Si nanowires, and Si nanofibers, one could achieve a higher sensitivity compared to sensing with a free-space beam (S = 1.0). The sensitivity for gas sensing is higher than that for liquid sensing due to the higher index-contrast. The waveguide sensitivity of an optimized suspended Si nanowire for gas sensing is as high as 1.5, which is much higher than that of a SOI nanoslot waveguide. Furthermore, the optimal design has very large tolerance to the core width variation due to the fabrication error (\u2206w ~ \u00b150 nm). In contrast, a Si nanofiber could also give a very high sensitivity (e.g., ~1.43) while the fabrication tolerance is very small (i.e., \u2206w &lt; \u00b15 nm). The comparative study shows that suspended Si nanowire is a good choice to achieve ultra-high waveguide sensitivity.<\/jats:p>","DOI":"10.3390\/s16030324","type":"journal-article","created":{"date-parts":[[2016,3,3]],"date-time":"2016-03-03T10:30:47Z","timestamp":1457001047000},"page":"324","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Sensitivity Enhancement in Si Nanophotonic Waveguides Used for Refractive Index Sensing"],"prefix":"10.3390","volume":"16","author":[{"given":"Yaocheng","family":"Shi","sequence":"first","affiliation":[{"name":"Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Zijingang Campus, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Ke","family":"Ma","sequence":"additional","affiliation":[{"name":"Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Zijingang Campus, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daoxin","family":"Dai","sequence":"additional","affiliation":[{"name":"Centre for Optical and Electromagnetic Research, State Key Laboratory for Modern Optical Instrumentation, Zhejiang Provincial Key Laboratory for Sensing Technologies, Zhejiang University, Zijingang Campus, Hangzhou 310058, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2016,3,3]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"2520","DOI":"10.1109\/LPT.2006.887374","article-title":"A silicon-on-insulator photonic wire based evanescent field sensor","volume":"18","author":"Densmore","year":"2006","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"15558","DOI":"10.3390\/s121115558","article-title":"Recent advances in integrated photonic sensors","volume":"12","author":"Passaro","year":"2012","journal-title":"Sensors"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"317","DOI":"10.1364\/OL.31.000317","article-title":"All-fiber multimode-interference-based refractometer sensor: Proposal and design","volume":"31","author":"Wang","year":"2006","journal-title":"Opt. Lett."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"842","DOI":"10.1109\/LPT.2011.2136430","article-title":"Cascaded-ring optical sensor with enhanced sensitivity by using suspended Si-nanowires","volume":"23","author":"Hu","year":"2011","journal-title":"IEEE Photonics Technol. Lett."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"16017","DOI":"10.3390\/s140916017","article-title":"Performance of SOI Bragg Grating Ring Resonator for Nonlinear Sensing Applications","volume":"14","author":"Campanella","year":"2014","journal-title":"Sensors"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"783","DOI":"10.1126\/science.1145002","article-title":"Label-free, single-molecule detection with optical microcavities","volume":"317","author":"Armani","year":"2007","journal-title":"Science"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"041001","DOI":"10.1117\/1.3527260","article-title":"Silicon nanophotonic devices based on resonance enhancement","volume":"4","author":"Zhou","year":"2010","journal-title":"J. Nanophotonics"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"578","DOI":"10.1007\/s10043-997-0578-z","article-title":"Coupling-wave structures for optical waveguide sensors","volume":"4","author":"Qing","year":"1997","journal-title":"Opt. Rev."},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"13548","DOI":"10.3390\/s150613548","article-title":"Design Procedure and Fabrication of Reproducible Silicon Vernier Devices for High-Performance Refractive Index Sensing","volume":"15","author":"Troia","year":"2015","journal-title":"Sensors"},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"4229","DOI":"10.1364\/OL.35.004229","article-title":"Highly sensitive Si nanowire-based optical sensor using a Mach\u2013Zehnder interferometer coupled microring","volume":"35","author":"Wang","year":"2010","journal-title":"Opt. Lett."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1395","DOI":"10.1109\/JLT.2005.863333","article-title":"Design and optimization of microring resonators in biochemical sensing application","volume":"24","author":"Chao","year":"2006","journal-title":"J. Lightwave Technol."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"23817","DOI":"10.1364\/OE.17.023817","article-title":"Highly sensitive digital optical sensor based on cascaded high-Q ring-resonators","volume":"17","author":"Dai","year":"2009","journal-title":"Opt. Express"},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"22747","DOI":"10.1364\/OE.18.022747","article-title":"Experimental characterization of a silicon photonic biosensor consisting of two cascaded ring resonators based on the Vernier-effect and introduction of a curve fitting method for an improved detection limit","volume":"18","author":"Claes","year":"2010","journal-title":"Opt. Express"},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"1128","DOI":"10.1364\/OL.36.001128","article-title":"Optical waveguide double-ring sensor using intensity interrogation with a low-cost broadband source","volume":"36","author":"Jin","year":"2011","journal-title":"Opt. Lett."},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"677","DOI":"10.1109\/50.842082","article-title":"Sensitivity enhancement in evanescent optical waveguide sensors","volume":"18","author":"Veldhuis","year":"2000","journal-title":"J. Lightwave Technol."},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"2039","DOI":"10.1109\/50.802992","article-title":"Guiding optical light in air using an all-dielectric structure","volume":"17","author":"Fink","year":"1999","journal-title":"J. Lightwave Technol."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"1209","DOI":"10.1364\/OL.29.001209","article-title":"Guiding and confining light in void nanostructure","volume":"29","author":"Almeida","year":"2004","journal-title":"Opt. Lett."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"3226","DOI":"10.1364\/OE.18.003226","article-title":"On-chip temperature compensation in an integrated slot-waveguide ring resonator refractive index sensor array","volume":"18","author":"Gylfason","year":"2010","journal-title":"Opt. Express"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"4977","DOI":"10.1364\/OE.15.004977","article-title":"Optical sensing by optimized silicon slot waveguides","volume":"15","author":"Passaro","year":"2007","journal-title":"Opt. Express"},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"596","DOI":"10.1364\/JOSAA.28.000596","article-title":"Design and optimization of waveguide sensitivity in slot microring sensors","volume":"28","author":"Kargar","year":"2011","journal-title":"J. Opt. Soc. Am. A"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"885","DOI":"10.1364\/OE.18.000885","article-title":"Enhanced electro-optic phase shifts in suspended waveguides","volume":"18","author":"Stievater","year":"2010","journal-title":"Opt. Express"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Yang, B., Sheng, Z., and Dai, D. (2009, January 2\u20136). Design of Suspended SU-8 Optical Waveguides for Ultrasmall Bendings. Proceedings of the 2009 Asia Communications and Photonics Conference and Exhibition (ACP), Shanghai, China.","DOI":"10.1364\/ACP.2009.ThE2"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"816","DOI":"10.1038\/nature02193","article-title":"Subwavelength-diameter silica wires for low-loss optical wave guiding","volume":"426","author":"Tong","year":"2003","journal-title":"Nature"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"6259","DOI":"10.1364\/OE.14.006259","article-title":"High confinement suspended micro-ring resonators in silicon-on-insulator","volume":"13","author":"Martinez","year":"2006","journal-title":"Opt. Express"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"5405","DOI":"10.1364\/OL.38.005405","article-title":"Suspended Submicron-disk Resonator on Silicon for Optical Sensing","volume":"38","author":"Wang","year":"2013","journal-title":"Opt. Lett."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/16\/3\/324\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:20:08Z","timestamp":1760210408000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/16\/3\/324"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2016,3,3]]},"references-count":25,"journal-issue":{"issue":"3","published-online":{"date-parts":[[2016,3]]}},"alternative-id":["s16030324"],"URL":"https:\/\/doi.org\/10.3390\/s16030324","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2016,3,3]]}}}