Fig. 3.

Optical manipulation of the THz tunneling current. a Ultrafast THz tunneling current manipulation by optical pulse illumination on the ring-shaped quantum barriers. A femtosecond optical pulse generates an additional tunneling current at a specific position of the triangle. b Experimental measurement of the time-resolved ultrafast optical gating of the THz tunneling current as a function of the position and time delay of the optical pulse (triangle loop, side length of 70 μm, gap size of 2 nm). The optical pulse modulates the barrier potential spatiotemporally, thereby generating position-sensitive and time-dependent switching signals. Incident polarizations of THz and optical pulses are the same as in (a)