Optical constants of ice Ih crystal at terahertz frequencies

Terahertz time-domain spectroscopy was used to measure the refractive indic es of Ih crystalline ice in the frequency range of 0.25-1.0 THz. With incre asing frequency, the real part, n('), of the refractive index increases fro m 1.787 to 1.793 at 243 K, and the imaginary part, n('), increases from 0.0 05 to 0.020. The temperature dependence of n(') is less than 0.01%/K and th at of n" is similar to1%/K. Our results connect smoothly to the data of Mat suoka and co-workers [T. Matsuoka, S. Fujita, and S. Mae, J. Appl. Phys. 80 , 5884 (1996)] in the microwave range and the data in the far IR range, and can be well described by the existing theoretical models. (C) 2001 America n Institute of Physics.