Dispersive 2D Cherenkov radiation on a dielectric nano-film

We report a modified two-dimensional Cherenkov radiation, which occurs on a high-index dielectric nano-film driven by uniformly moving electron-beam. It is essentially different from the ordinary Cherenkov radiation in that, in the nondispersive medium, it shows unique dispersion characteristics—the waves with higher frequencies radiate at larger Cherenkov angles. Its radiation frequency and direction are essentially determined by structure parameters as well as the beam-velocity. By means of fully electromagnetic simulations and theoretical analyses, we explored the mechanism and requirements of this radiation. This new Cherenkov radiation may lead to promising applications in a broad range of fields.