Zinc oxide nanoparticle-doped nanoporous solgel fiber as a humidity sensor with enhanced sensitivity and large linear dynamic range.

An all-optical humidity sensor based on direct and exhaustive guided-mode attenuation in an in-house developed zinc oxide (ZnO) nanoparticle-immobilized bare solgel fiber is reported. The main objective of the present work is to enhance the sensitivity considerably while realizing a throughout linear response over a wide dynamic range. The developed sensor is characterized and performance characteristics of the sensor are compared with an optical fiber humidity sensor employing an evanescent wave absorption scheme in a straight and uniform probe, with ZnO nanoparticles-immobilized solgel film as humidity sensing cladding. Sensor response is observed to be linear over a wide dynamic range of 5%-95% relative humidity (RH). The observed linear sensitivity is 0.0103/% RH, which is ~9 times higher than the sensor employing the evanescent wave absorption scheme. In addition, sensor response is observed to be very fast, highly reversible, and repeatable.