Silicon Subwavelength Grating Slot Waveguide based Optical Sensor for Label Free Detection of Fluoride Ion in Water

AbstractRecently, Subwavelength Grating Waveguides (SWG WG) attract a lot of attention for sensing applications because it offers better sensitivity than conventional WGs. The sensitivity of SWG WG is greatly improved due to the interaction between the analyte and guiding mode in the SWG segments. In this study, a highly sensitive sensor based on a silicon SWG slot waveguide (SWGSW) is proposed for detecting low-concentration fluoride contaminations in water. The gap called as "slot" between the silicon slab along with cladding and the spaces between the segmented silicon rail waveguide is filled with fluoride ion-contaminated water samples as analyte for strong light–matter interaction between guiding modes of the SWG structure, resulting in greater sensitivity of the proposed sensor. The sensitivity of the proposed structure is estimated by numerical simulations as S = 615.38 nm/RIU which is comparable to the existing reported optical sensor structures based on optical waveguide and optical fibre with a smaller footprint. Additionally, the effect of variation of geometrical parameters on the transmission resonances of the proposed structure is also analyzed for the optimization of a SWG WG structure. The obtained results will be helpful to realize and design highly sensitive sensors based on the SOI platform.KEYWORDS: Optical sensorPhotonic bandgap (PBG)Silicon photonicsSlot waveguideSubwavelength grating (SWG)SWG slot waveguide (SWGSW) ACKNOWLEDGEMENTSThe authors gratefully acknowledge the Indian Institute of Technology (Indian School of Mines) Dhanbad, Jharkhand, India for providing COMSOL Multiphysics simulation software, used in this simulation work.Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationNotes on contributorsKritika AwasthiKritika Awasthi received a BTech degree in electronics engineering from BBBNIIT, Lucknow, India in 2012 and an MTech degree in digital systems from MNNIT, Allahabad, India in 2017. She is currently pursuing PhD at the department of electronics, IITISM, Dhanbad, India in Silicon on insulator waveguides for on-chip communication. Her research interests are silicon photonics and the modelling of optical devices.Nishit MalviyaNishit Malviya received a BE degree in electronics and communication engineering from Patel College of Science and Technology, Bhopal, India in 2009, an MTech degree from Shri GS Institute of Technology and Science, and a PhD degree from the department of electronics, Indian Institute of Technology (Indian School of Mines), Dhanbad, in 2012 and 2018, respectively. He is currently an assistant professor at IIIT Ranchi. His research interests are optical communication, silicon photonics, and modelling of optical devices. Email: nishit.malviya@iiitranchi.ac.inAmitesh KumarAmitesh Kumar (Member, IEEE) received a BE degree in electronics and communication engineering from Magadh University, Bodh Gaya, Bihar, India, in 2008 and the MTech and PhD degrees from the department of electronics, Indian Institute of Technology (Indian School of Mines), Dhanbad, in 2010 and 2017, respectively. He is currently an assistant professor at IIT (ISM), Dhanbad. His research interests are fiber-optic sensing, microwave photonics, and optical communication. He is a member of SPIE and a senior member of OPTICA. Email: amitesh@iitism.ac.in