Figure 2.

Comparison of (a) incident THz electric field and (b) tip-enhanced THz voltage transient in the STM junction (U_DC = 8 V, d = 1 μm, E_p,STE = 0.6 μJ). (c) THz amplitude spectra of the waveforms of (a) and (b), revealing strong low-pass filtering from the tip, which is characterized by (d) the measured receiving antenna transfer function H(ω). The green line in (d) shows the response of the antenna model with R = 300 Ω, L = 0.32 nH, and C = 35 fF, yielding a resonance frequency of 0.05 THz and the RLC-filtered voltage transient plotted in b (dashed curve).