A novel simple humidity sensor is prepared by using a symmetric slab glass waveguide whose two surfaces are coated with nanoporous TiO2 thin films.The humidity-sensing principle of the device is that the propagation loss of light guided in the waveguide relies on the average refractive index of nanoprous TiO2 film,and the latter is a function of the amount of water adsorbed in the film.Owing to the strong dependence of the amount of adsorbed water on the ambient humidity,the relative humidity(RH...