Fig. 4: Temporal imaging of a propagating THz gap excitation.
From: Ultrafast imaging of terahertz electric waveforms using quantum dots
a Launching of a THz waveguide excitation in a micro-slit driven at normal incidence (2 µm gap). b 2D representation (x, Δτ) of the normalized QFIM waveforms along the slit temporally disentangles the spatially homogeneous direct response of the slit (direct field enhancement) and a THz gap excitation propagating along the waveguide. The peak electric field inside the waveguide propagates with a velocity below c0 (dashed line) as quantitatively predicted by time-domain electromagnetic simulation (cprop, solid line). c The reversed propagation direction is observed via QFIM for excitation at the opposite side of the waveguide. d Simulated electric field distributions for two temporal delays illustrate the homogeneous direct enhancement (Δτ1 = 0 ps) and the propagating THz excitation (Δτ2 = 1 ps). e 2D representation (x, Δτ) of the simulated electric field evolution along the gap in correspondence to (b, c)
