Fig. 2: Proof-of-concept experiments for THz optical waveform measurement.

a Simple layout of the experimental setup. As the incident optical signal for the proof-of-concept experiment, a vertically polarized THz wave was focused on the thin copper slit by a single spherical lens. A wire-grid polarizer pair was utilized to control the electric field strength of the input THz signal. The fabricated copper slit with a gap size of 30 μm is shown in the inset image with a scale bar of 100 μm. b THz waveform measured by the EMCCD. The white box represents a single-shot time window (W) for L = 3.78 mm at the gap. By adjusting the optical delay between the input signal and the electron bunch, the region of interest in the time ___domain can be easily changed. c The experimental results on the detection linearity of our oscilloscope. The positive maximum values of the deflected electron array in the left image are plotted in the graph as a function of the relative angle (θ) of the wire-grid polarizer pair (orange dots). The blue solid curve is the quadratic sinusoidal fit to the experimental data. d Time-varying \({{{{{{\boldsymbol{E}}}}}}}_{{{{{{\bf{i}}}}}}{{{{{\bf{n}}}}}}-{{{{{\bf{g}}}}}}{{{{{\bf{a}}}}}}{{{{{\bf{p}}}}}}}\) from the single-shot data in the white box of (b). e, f Magnified plots of green and red boxes in (d) for presenting the accuracy of the vertical field amplitude (e) and temporal step per pixel of EMCCD camera (f).