title: High-sensitivity optical humidity sensor based on a thin dielectric waveguide.
abstract: 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.
authors.affiliation: Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil.
authors.forename: R A S
authors.initials: RA
authors.lastname: Ribeiro
authors.forename: J F M
authors.initials: JF
authors.lastname: Domenegueti
authors.forename: S C
authors.initials: SC
authors.lastname: Zilio