Abstract
A surface plasmon resonance (SPR) sensor based on a side-polished single mode fiber coated with polyvinyl alcohol (PVA) is demonstrated for relative humidity (RH) sensing. The SPR sensor exhibits a resonant dip in the transmission spectrum in ambient air after PVA film coating, and the resonant wavelength shifts to longer wavelengths as the thickness of the PVA film increases. When RH changes, the resonant dip of the sensor with different film-thicknesses exhibits interesting characteristics for optical spectrum evolution. For sensors with initial wavelengths between 550 nm and 750 nm, the resonant dip shifts to longer wavelengths with increasing RH. The averaged sensitivity increases firstly and then drops, and shows a maximal sensitivity of 1.01 nm/RH%. Once the initial wavelength of the SPR sensor exceeds 850 nm, an inflection point of the resonant wavelength shift can be observed with RH increasing, and the resonant dip shifts to shorter wavelengths for RH values exceeding this point, and sensitivity as high as −4.97 nm/RH% can be obtained in the experiment. The sensor is expected to have potential applications in highly sensitive and cost effective humidity sensing.
Highlights
The monitoring of relative humidity (RH) of the environment around the analyte is critical in a variety of situations such as food fabrication, medical research, agricultural production, weather prediction, and air quality monitoring
Compared to a traditional electric RH sensor, optical fiber-based sensors exhibit a great number of advantages, such as security to the human body, miniaturization for integration, and good resistance to electromagnetic interference
Miao et al have demonstrated a RH sensor based on a polyvinyl alcohol (PVA)
Summary
The monitoring of relative humidity (RH) of the environment around the analyte is critical in a variety of situations such as food fabrication, medical research, agricultural production, weather prediction, and air quality monitoring. A variety of fiber devices have been implemented in to the design of optical fiber RH sensors, configurations including interferometers [1,2,3,4,5,6,7], long period fiber gratings [8,9], tapered fibers [10,11,12,13], fiber Bragg gratings (FBGs) [14,15,16,17,18], mode couplers [19,20], ZnO nanostructures [21,22], evanescent wave absorption structures [23,24], and so on. Miao et al have demonstrated a RH sensor based on a polyvinyl alcohol (PVA)
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