Sub-Second Humidity Sensing Based on Nanostructured Narrow-Bandpass Optical Filters

摘要

An optical-based humidity sensor with a sub-second response time was fabricated from a nanostructured titanium dioxide thin film. A refractive index profile designed to yield a narrow-bandpass optical interference filter was obtained through nanoscale porosity variations produced by glancing angle deposition (GLAD). Under varying humidity conditions the transmittance spectrum of the filter shifts due to effective index changes of the porous structure resulting from adsorption/desorption of water vapor. In the following we will show that this device is highly sensitive, exhibits minimal hysteresis, and is extremely fast. The adsorption and desorption response times were measured to be 270 ms and 160 ms, respectively.