A novel composite model is put forward for humidity-sensitive material based on Maxwell-Garnett and effective medium theory. The analytical expression of the relation between effective refractive index and relative humidity is shown with different absorption factors and porosities. The larger the absorption factor is, the higher the refractive index is. The refractive index of humidity-sensitive SiO<sub>2</sub> film decreases with the increase of ceramic material porosity. The sensitivity of optical humidity sensor can reach the magnitude of 10<sup>?3</sup>. In comparison with the experimental humidity-sensing curve by the method of p-polarized reflectance and the analysis of mechanism, theoretical simulation is in agreement with experimental results. Therefore, this composite model is proved to be reasonable which lays new theoretical foundation in further research on optical humidity sensor.
© 2009 Chinese Optics Letters
(000.3860) General : Mathematical methods in physics
(010.7340) Atmospheric and oceanic optics : Water
(280.4788) Remote sensing and sensors : Optical sensing and sensors
(280.5715) Remote sensing and sensors : Refractivity profiles
Zhenyuan Wang and Zhengtian Gu, "Optical humidity-sensitive mechanism based on refractive index variation," Chin. Opt. Lett. 7, 756-759 (2009)