Laser-Pumped Nanogap Generates Terahertz Radiation

Nanoscale vacuum channel devices (NVCDs) with an electrode gap ranging from hundreds of nanometers to a few nanometers expand the field of vacuum electronics. Since the nanogap is much smaller than the mean free path of electrons in a vacuum, electron transport approximates ballistic transport and is not affected by factors such as collisions and scattering. Therefore, NVCDs combine the advantages of both traditional vacuum electronics and solid-state electronics. However, existing research primarily focuses on optimizing the DC characteristics of the devices, with less emphasis on studying the ultrafast response of the devices. In this work, we simulate the field-induced emission and ultrafast transport of electrons in two-dimensional NVCDs using MAGIC, and calculate the far-field radiation. The simulation results indicate that a 25 nm nanogap can generate broadband terahertz signals spanning from 0 to 30 THz when excited by a biased electric field and an 800 nm laser pulse with a duration of 100 fs. Our work validates the potential of NVCDs as miniaturized, integrated, broadband, and high-frequency terahertz sources.