title: Agarose gel-coated LPG based on two sensing mechanisms for relative humidity measurement.
abstract: A relative humidity (RH) sensor based on long-period grating (LPG) with different responses is proposed by utilizing agarose gel as the sensitive cladding film. The spectral characteristic is discussed as the ambient humidity level ranges from 25% to 95% RH. Since increment of RH will result in volume expansion and refractive index increment of the agarose gel, the LPG is sensitive to applied strain and ambient refractive index; both the resonance wavelength and coupling intensity present particular responses to RH within two different RH ranges (25%-65% RH and 65%-96% RH). The coupling intensity decreases within a lower RH range while it increases throughout a higher RH range. The resonance wavelength is sensitive to the higher RH levels, and the highest sensitivity reaches 114.7 pm/% RH, and shares the same RH turning point with coupling intensity response. From a practical perspective, the proposed RH sensor would find its potential applications in high humidity level, temperature-independent RH sensing and multiparameter sensing based on wavelength/power hybrid demodulation and even static RH alarm for automatic monitoring of a particular RH value owing to the nonmonotonic RH dependence of the transmission power within the whole tested RH range.
authors.affiliation: Tianjin Key Laboratory of Film Electronic & Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384, China. kikosi@126.com
authors.forename: Yinping
authors.initials: Y
authors.lastname: Miao
authors.forename: Kaikiang
authors.initials: K
authors.lastname: Zhang
authors.forename: Yujie
authors.initials: Y
authors.lastname: Yuam
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.forename: Hao
authors.initials: H
authors.lastname: Zhang
authors.forename: Yan
authors.initials: Y
authors.lastname: Liu
authors.forename: Jianquan
authors.initials: J
authors.lastname: Yao
mesh_terms: D000388:Air / Q000032:analysis*; D055119:Elastic Modulus; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005782:Gels / Q000737:chemistry / Q000528:radiation effects; D006813:Humidity; D008027:Light; D012031:Refractometry / Q000295:instrumentation*; D012685:Sepharose / Q000737:chemistry* / Q000528:radiation effects*; D013227:Steam / Q000032:analysis*; D020349:Surface Plasmon Resonance / Q000295:instrumentation*; D014159:Transducers
chemical_list: D005782:Gels; D013227:Steam; D012685:Sepharose