A low-cost, high-sensitivity humidity sensor based on a low-loss dielectric thin film waveguide (WG) is presented. The guided mode is produced by coupling laser light into the film by optical tunneling through a solid gap deposited on the base of a semi-cylindrical lens. The light reflected from this optical system carries information about the refractive index of the medium neighboring the WG, and is detected by a low-cost CCD linear sensor and analyzed with a microcontroller or personal computer. The technique presents good sensitivity to relative humidity (RH) changes, especially below 10% RH, linear behavior between 20% and 80% RH, and a response time of a few seconds.
© 2013 Optical Society of America
Original Manuscript: February 22, 2013
Revised Manuscript: April 25, 2013
Manuscript Accepted: May 20, 2013
Published: June 18, 2013
R. A. S. Ribeiro, J. F. M. Domenegueti, and S. C. Zilio, "High-sensitivity optical humidity sensor based on a thin dielectric waveguide," Appl. Opt. 52, 4287-4293 (2013)