The variation of the optical properties of porous Vycor glass (Corning, Model 7930) under different relative-humidity conditions was studied. The adsorption of water into the glass pores was investigated with spectroscopic ellipsometry. The change of the refractive index was Δ<i>n</i> ~ 0.04 between 5% and 90% relative humidity. A linear relation between the ellipsometer parameter tan Ψ, the amount of water adsorbed in the glass pores, and information about the pore-size distributions was established. The results are in accord with the values obtained from N<sub>2</sub> isotherms, transmission electron microscope micrographs, and the manufacturer’s specifications (radius of ~20 Å). The possibility of using this material as a transducer for implementation in a fiber-optic sensor to measure humidity was evaluated.
© 2001 Optical Society of America
(010.7340) Atmospheric and oceanic optics : Water
(120.2130) Instrumentation, measurement, and metrology : Ellipsometry and polarimetry
(160.4760) Materials : Optical properties
(160.6030) Materials : Silica
Alberto Álvarez-Herrero, Raquel L. Heredero, Eusebio Bernabeu, and David Levy, "Adsorption of Water on Porous Vycor Glass Studied by Ellipsometry," Appl. Opt. 40, 527-532 (2001)