Fig. 1. Schematic diagram of 45° optical bias THz-TDS by EOS. P, polarizer; WP, Wollaston polarizer; QWP, quarter-wave plate; HWP, half-wave plate; L1, L2, lenses; PM, off-axis parabolic mirror; ZnTe, (110) ZnTe crystal; BD, balanced detector.

Fig. 2. Setup of SS-THz-PD. ST, pulse stretcher; P1, P2, polarizers; QWP1, QWP2, quarter-wave-plates; L1, L2, lenses; PM, off-axis parabolic mirror; ZnTe, (110) ZnTe crystal; α-BBO, α-BaB2O4 crystal; SP, spectrometer.

Fig. 3. Illustration of the data process by simulation to extract the horizontal and vertical components of THz temporal waveforms.

Fig. 4. Comparison between the measured (blue lines) and the calculated (red lines) signals of the (a) horizontal and (b) vertical components from the THz temporal waveforms with circular polarization converted from the linearly polarized THz signal by using a 2.7 mm quartz plate.

Fig. 5. THz temporal signals measured by SS-THz-PD (red lines) and ICP-SI (blue lines) for three target polarizations: vertical linear polarization, −60° oriented linear polarization, and right-handed circular polarization, with (a), (b), and (c) for the horizontal and (d), (e), and (f) for the vertical components, and an insert on the top-left corner of (d) for the corresponding THz spectrum.

Fig. 6. THz polarization distribution characteristics measured by SS-THz-PD (red line) and ICP-SI (blue line) for the target THz polarization states: (a) vertical polarization, (b) −60° polarization, and (c) right circular polarization.

Fig. 7. 300 groups of measured THz temporal signals by using SS-THz-PD (red color zones) and ICP-SI (blue color zones) and their RMS averages (black lines in the zones) for three target polarizations: vertical linear polarization, −60° oriented linear polarization, and right-handed circular polarization, with (a), (b), and (c) for the horizontal components, and (d), (e), and (f) for the vertical components.

Fig. 8. 300 groups of measured THz temporal signals by using SS-THz-PD (red color zones) and traditional 45° optical bias THz-TDS by EOS (blue color zones) and their RMS averages (black lines in the zones): (a) horizontal components and (b) vertical components.