Fig. 1. Full experimental setup consisting of the driving laser, MPC, and THz-TDS parts. The inset shows the spectrum and temporal profile of the pump laser retrieved from the FROG trace. BPD, balanced photodetector; DAQ, data acquisition; WP, Wollaston prism.

Fig. 2. (a) THz refractive index [23] and pump group refractive index for MNA [26]. The dashed line indicates the pump wavelength of 1030 nm for the corresponding group index. (b) Calculated coherence length versus generated THz frequency and pump wavelength for MNA.

Fig. 3. THz power characterization using a power meter. (a) THz average power versus pump power. (b) Corresponding conversion efficiency. The inset demonstrates the THz profile captured with the camera.

Fig. 4. EOS. (a) THz trace in time domain. The inset shows the maximum amplitude of the EOS traces recorded for 10 min for 5 days in row. (b) Corresponding spectrum in the orange line and dark measurement in gray line. The blue shaded area indicates the simulation results.

Fig. 5. The refractive index and absorption coefficient of a GaP wafer with a thickness of 475 μm placed in the first focus of THz beam. The results are compared to Refs. [31,37,38].

Fig. 6. The refractive index and absorption coefficient of an NMBA crystal with a thickness of 490 μm placed in the first focus of THz beam. The results are compared to Ref. [39].

Fig. 7. Long-term laser measurement of MNA at 5 W of laser pump power.

Fig. 8. Picture of the crystal pumped with 5 W of power at three different times.

Fig. 9. Peak dynamic range versus cumulative averaged traces.

Fig. 10. Extracted complex refractive index of PTFE up to 8 THz.