Temperature-Dependent Dielectric Characterization of Magneto-Optical Tb3Sc2Al3O12 Crystal Investigated by Terahertz Time-Domain Spectroscopy**Supported by the National Natural Science Foundation of China under Grant Nos 11604202, 11674213, 61735010 and 51572275, the Shanghai Rising-Star Program under Grant No 18QA1401700, the ‘Chen Guang’ Project under Grant No 16CG45, the Shanghai Municipal Education Commission, and the Shanghai Education Development Foundation.

Abstract

Terbium scandium aluminum garnet (TSAG) crystals have been widely used in magneto-optical systems. We investigate the complex refractive index of the TSAG crystal in the terahertz frequency range using terahertz (THz) time-domain spectroscopy in the temperature range 100–300 K. It is observed that the refractive index and the absorption coefficient increase with the THz frequency. The refractive index increases with the temperature. We measure the temperature coefficient of the refractive index of the TSAG crystal in the frequency range 0.4–1.4 THz. Furthermore, the loss tangent, i.e., the ratio of experimental values of the imaginary and real part of the dielectric permittivity, is found to be almost independent of frequency. TSAG is very promising for applications in THz optoelectronics because it has a high dielectric constant, low loss, and low thermal coefficient of the dielectric constant.