{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T02:12:23Z","timestamp":1760148743779,"version":"build-2065373602"},"reference-count":35,"publisher":"MDPI AG","issue":"11","license":[{"start":{"date-parts":[[2023,6,4]],"date-time":"2023-06-04T00:00:00Z","timestamp":1685836800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100002383","name":"King Saud University, Riyadh, Saudi Arabia","doi-asserted-by":"publisher","award":["RSPD2023R654"],"award-info":[{"award-number":["RSPD2023R654"]}],"id":[{"id":"10.13039\/501100002383","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>A novel refractive index-based sensor implemented within a silicon photonic integrated circuit (PIC) is reported. The design is based on a double-directional coupler (DC) integrated with a racetrack-type resonator (RR) to enhance the optical response to changes in the near-surface refractive index via the optical Vernier effect. Although this approach can give rise to an extremely large \u2018envelope\u2019 free spectral range (FSRVernier), we restrict the design geometry to ensure this is within the traditional silicon PIC operating wavelength range of 1400\u20131700 nm. As a result, the exemplar double DC-assisted RR (DCARR) device demonstrated here, with FSRVernier = 246 nm, has a spectral sensitivity SVernier = 5 \u00d7 104 nm\/RIU.<\/jats:p>","DOI":"10.3390\/s23115332","type":"journal-article","created":{"date-parts":[[2023,6,5]],"date-time":"2023-06-05T02:57:47Z","timestamp":1685933867000},"page":"5332","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["A Design of a Novel Silicon Photonics Sensor with Ultra-Large Free Spectral Range Based on a Directional Coupler-Assisted Racetrack Resonator (DCARR)"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0389-2716","authenticated-orcid":false,"given":"Osamah","family":"Alsalman","sequence":"first","affiliation":[{"name":"Department of Electrical Engineering, College of Engineering, King Saud University, P.O. Box 800, Riyadh 11421, Saudi Arabia"}]},{"given":"Iain","family":"Crowe","sequence":"additional","affiliation":[{"name":"Department of Electrical and Electronic Engineering, Photon Science Institute, The University of Manchester, Manchester M13 9PL, UK"}]}],"member":"1968","published-online":{"date-parts":[[2023,6,4]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Peng, C., Yang, C., Zhao, H., Liang, L., Zheng, C., Chen, C., Qin, L., and Tang, H. (2023). Optical Waveguide Refractive Index Sensor for Biochemical Sensing. Appl. Sci., 13.","DOI":"10.3390\/app13063829"},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Park, J.-H., Cho, Y.-W., and Kim, T.-H. (2022). Recent advances in surface plasmon resonance sensors for sensitive optical detection of pathogens. 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