A. Configurations The configuration

A. Configurations The configuration of the developed optical electric-field probe is shown in Fig. 2. The probe tip comprises just dielectric components, a CdTe crystal with a dielectric reflector, a Faraday rotator (FR), a lens, a glass ferrule, and an optical fiber. The size of the crystal is 1 x 1 x 1 mm3 which is smaller than the wavelength of the RF wave at the frequency of 300 GHz. Therefore, the optical probe can detect the electric field with less invasiveness for the RF wave. The diameter of the optical beam propagating in the crystal is 200 m which determines the spatial resolution for detecting the transversal electric field. The longitudinal resolution is determined by the interaction length between the optical beam and an RF wave propagating in the crystal, which is 1 mm in this probe. The optical electricfield probe is connected to a polarization controller through a 5-m long optical fiber, as shown in Fig. 2. Theoretically, the system should operate with stable sensitivity even if the optical fiber is extended to a length of 1 km [11].