Temperature dependent optical and dielectric properties of liquid water studied by terahertz time-domain spectroscopy

Terahertz waves have found wide applications in the biological and medical areas. Since water is one of the most important ingredients in the biological systems, it is necessary to investigate its optical and dielectric properties in the terahertz range. These fundamental physical parameters play an important role in many applications, such as biological imaging and hyperthermia applications, and are temperature dependent. In order to shed more light on the property of temperature dependence, we performed a systematic investigation by changing the temperature of the water sample and using a terahertz time-domain spectrometer. The experimental results show that when the temperature increases from 275 K to 340 K, the refractive index and the complex dielectric constant of water increase noticeable, with the absorption coefficient increased observably. A good agreement is found between experimental data and the double Debye model