A nanoscale vacuum-tube diode triggered by few-cycle laser pulses

We propose and demonstrate a nanoscale vacuum-tube diode triggered by few-cycle near-infrared laser pulses. It represents an ultrafast electronic device based on light fields, exploiting near-field optical enhancement at surfaces of two metal nanotips. The sharper of the two tips displays a stronger field-enhancement, resulting in larger photoemission yields at its surface. One laser pulse with a peak intensity of $4.7\times 10^{11}$ W/cm$^2$ triggers photoemission of ${\sim }16$ electrons from the sharper cathode tip, while emission from the blunter anode tip is suppressed by $19$ dB to ${\sim }0.2$ electrons per pulse. Thus, the laser-triggered current between two tips exhibit a rectifying behavior, in analogy to classical vacuum-tube diodes. According to the kinetic energy of the emitted electrons and the distance between tips, the total operation time of this laser-triggered nanoscale diode is estimated to be below 1 ps.