Fig. 1. Experimental setup for the generation and detection of THz pulses with the LN and their detection by EO sampling. BS, beam splitter; M1, plane mirror reflecting the pump beam to the stair-step echelon mirror. The beam reflected by the echelon passes over M1; d1, 550 mm; d2, 125 mm; θLN, LN cut angle of 63°; L1, 100 mm focal length lens; L2, 300 mm focal length lens; L3, 50 mm focal length lens; L4, 75 mm focal length lens; L5, 100 mm focal length lens; L6, 150 mm focal length lens; OAEM1, OAEM with 83.82 mm image distance and 33.02 mm object distance; OAPM2, 100 mm reflected focal length off-axis parabolic mirror; OAPM3, 50 mm reflected focal length off-axis parabolic mirror; g1 and g2, transmissive diffracting gratings with 300 grooves/mm; λ/2, half-wave plate; λ/4, quarter-wave plate; WP, Wollaston prism; P, polarizer.

Fig. 2. Measured characteristics of the probe pulse after temporal compression. (a) Spectral amplitude and spectral phase distribution with the image of the probe spot in the inset; (b) temporal intensity and temporal phase distribution.

Fig. 3. Pump spot image. (a) 1 mm before the image plan position; (b) at the image plan position; and (c) 1 mm after the image plan position; (d) horizontal profile of the pump spot at the focus position; (e) normalized pump spectra at the entrance and the exit of the LN crystal after OR process.

Fig. 4. THz beam radius at several locations along its propagation path (a) at the LN crystal exit facet; (b) along the focus of the OAEM; (c) along the focus of the third off-axis mirror, which corresponds to the positions Z1, Z2, and Z3 in Fig. 1, respectively.

Fig. 5. (a) Temporal evolution of the generated THz pulse detected by EO sampling in an unpurged environment, with the zoom view of the temporal evolution of the THz pulse in a purged environment in the inset; (b) normalized spectrum of the generated THz pulse in an unpurged environment, with the normalized spectrum at logarithmic scale in the inset.

Fig. 6. Normalized THz transmission through the InGaAs sample as a function of z position, similar to Ref. [43]. Inset, experimental setup for the Z-scan measurement with InGaAs sample: OAPM3 of 50 mm reflected focal length; OAPM4 of 50 mm reflected focal length; OAPM5 of 100 mm reflected focal length.