Refractive index and absorption coefficient of blue phase liquid crystal in terahertz band

The refractive index and absorption coefficient of blue phase liquid crystals are investigated by terahertz time-domain spectroscopy system. Four phases, including isotropic phase, BPII, BPI, and cholesteric phase are investigated. The refractive index of liquid crystal sample is dependent on the temperature, which is related to the different phases. In our experiment, in the frequency range of 0.2-1.2THz, the refractive index of BPII and BPI is about 1.620 and 1.625, respectively. For BPII and BPI, the measured absorption coefficients increase with the increase of frequency, with absorption peak appearing at 1.11 and 1.05THz, respectively. These properties of BPLC provide useful information for BPLC-based terahertz components such as phase shifter, wave-plates and so on.