Elizabeth Caroline, E.C.Nizar, S.M.Krishnan, P.2026-02-042022Silicon, 2022, 14, 18, pp. 12665-126741876990Xhttps://doi.org/10.1007/s12633-022-01982-3https://idr.nitk.ac.in/handle/123456789/22295Sulfur dioxide (SO<inf>2</inf>) is one of the most prevalent contaminants in the atmosphere. It is mostly generated as a byproduct of the burning of sulfur-containing coal and oils, as well as the smelting of various ores. SO<inf>2</inf> contributes to the development of major diseases such as asthma and chronic bronchitis. In this paper, we proposed a Wheel Structured circular air hole Photonic Crystal Fiber (WS-PCF) based gas sensor to detect SO<inf>2</inf> gas. The proposed WS-PCF gas sensor consists of a four-layer-thick circular cladding air hole. The diameter of the first layer varies throughout the optimization procedure, while the diameters of the succeeding three layers remain constant. The numerical investigation on the sensor parameters such as numerical aperture, effective area, non-linearity, confinement, loss and the relative sensitivity of the proposed sensor are extensively analyzed in a wavelength range of 0.9 µm to 1.2 µm. The proposed WS-PCF gas sensor offers the highest relative sensitivity of 83.64% and a lower confinement loss of 6.34 × 10 - 9dB/ km. The proposed sensor is simple and offers 14% high sensitivity and very low confinement loss (10-3reportedinliterature) compared with the exist literature. © 2022, The Author(s), under exclusive licence to Springer Nature B.V.Chemical sensorsCrystal whiskersGas detectorsGasesNonlinear opticsPhotonic crystal fibersChronic bronchitisCircular air-holesCircular claddingConfinement lossGas-sensorsNon-linearity and numerical apertureNumerical aperturePhotonic-crystal fiberRelative sensitivityWS-PCF gas sensorSulfur dioxide