A Simple Terahertz Polarization-Excitation-Based Method for Measuring Refractive Index of Planar Medium

In the present study, a simple Terahertz(THz) polar-ization-excitation-based method is proposed to examine the refractive index of planar medium. This method is devised for low THz band (i.e., 0.2 THz). Inspired by classical Fresnel formula, the method utilizes circularly polarized antenna to excite circularly polarized wave. Then, the reflected s-polarized wave and p-polarized wave are directly received through respective linearly polarized antenna. The refractive index thus can be easily obtained from the Brewster's angle of the object, which is the incident angle yielding the maximal s-component to p-component ratio. The overall measurement reliability is guaranteed from both the transmitting end and the receiving end. The transmitted THz wave is collimated and focused through the properly optical path for anti-interference, while the s-component and the p-component are received based on two balanced paths against the stimulation and disturbance. A high-resistance silicon is taken as a specimen, whose refractive index is estimated as 3.37 on average in 75 GHz-110 GHz band. This high agreement with the result measured by THz time domain spectroscopy verifies the effectiveness of the proposed method.