Abstract
The straight channel optical waveguide coated with the SnO2 nanoparticle is studied as an all-optical humidity sensor. The proposed sensor shows that the transmission loss of the waveguide increases with increasing relative humidity (RH) from 56% to 90% with very good repeatability. The sensitivity to changes in relative humidity is ∼2 dB/% RH. The response time of the humidity sensor is 2.5 s, and the recovery time is 3.5 s. The response to humidity can be divided into 3 different regions, which are correlated to the degree of water adsorption in the SnO2 nanoparticle layer. Compared with the previous all-optical humidity sensor based on SnO2, the proposed sensor exhibits more rapid response, simpler fabrication process, and higher sensitivity. The proposed sensor has a potential application in the long distance, remote agriculture, and biological humidity sensing.
Highlights
Aside from temperature, relative humidity (RH) is one of the most frequently measured physical qualities in advance applications such as material processing and manufacturing [1, 2]
The range of relative humidity measured by the planar slab optical waveguide based sensor (3% RH − 98% RH) is broader than the values reported by the optical fiber based sensors (20% RH − 90% RH)
We report an all-optical humidity sensor in the form of the SnO2 nanoparticle layer coated on a planar stripe optical waveguide
Summary
Aside from temperature, relative humidity (RH) is one of the most frequently measured physical qualities in advance applications such as material processing and manufacturing [1, 2]. A number of humidity sensors with response time of less than 1 s have been developed These sensors can be categorized into electrical, acoustic, and optical systems. Besides exhibiting the fastest response time, all-optical humidity sensors have advantages such as immunity to electromagnetic interference and nuclear radiation (for high-energy physics application), water and corrosion resistance, and ability to operate in low temperature environment. The range of relative humidity measured by the planar slab optical waveguide based sensor (3% RH − 98% RH) is broader than the values reported by the optical fiber based sensors (20% RH − 90% RH). All optical humidity sensors based on the SnO2 nanoparticles have a potential for being used in high-energy physics applications and long-distance humidity sensing that require the fast response time
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