Broadband polarization properties of photoconductive spiral antenna

The polarization property of a photoconductive spiral antenna in the terahertz (THz) region was studied using THz time-domain spectrometer. The emitted THz radiation showed a circular polarization, whose handedness agreed with the winding direction of the spiral. The sensitivity of the spiral antenna was also measured using circularly polarized THz waves. For the circular polarization with the same handedness of the spiral antenna, the detection sensitivity was 50 times larger than for the polarization with opposite handedness.