Break the electron speed limit to generate Cherenkov radiation on a chip

Cherenkov radiation (CR) is electromagnetic radiation emitted by a moving charge passing through a dielectric medium at a speed greater than the phase velocity of light in that medium. However, even with the help of these novel materials, there still exists a speed threshold of charged particle to generate CR and the electron energy is always larger than 20keV. Here we propose a new approach to eliminate the electron speed threshold to generate CR and report the first on-chip integrated CR ultraviolet source. Having electrons fly on the surface of hyperbolic metamaterial, it is predicted that CR could be obtained with no electron speed threshold. By integrating a planar electron emitter on multi-layer metamaterial, we simulated the CR generation from 70nm to 500nm even when electron energy is as low as 1kev. This work opens up the possibility of on-chip integrated optoelectronic devices by making use of CR and studying the interaction of flying electrons with artificial nanostructures on chip.