The optical and dielectric properties of opals with different water contents were investigated using terahertz time-domain spectroscopy. The refractive indices and absorption coefficients showed different trends due to the different water contents. The effective medium theory was used to extract the intrinsic dielectric permittivity of opal from opal-polytetrafluoroethylene mixtures. The extracted dielectric permittivities were fitted using a double Debye model to analyze the microscopic relaxation mechanism.
Keywords: Debye model; THz; Terahertz spectroscopy; dielectric permittivity; effective medium theory; opal.