Coherent terahertz Smith–Purcell radiation from Dirac semimetals grating with very deep and narrow slits

Abstract

We demonstrate a physical mechanism of multicolor coherent terahertz (THz) Smith–Purcell radiation from surface plasmon polaritons (SPPs). In Dirac semimetals gratings with very deep and narrow slits, two types of SPP modes, the cavity and ordinary SPP modes, can be excited by fast electrons under different excitation conditions and then diffracted into radiation in specific directions. The radiation intensity is remarkably enhanced when SPPs are excited, and frequencies can be widely tuned by adjusting the parameters of grating and electrons. Our findings could provide a promising way for developing room temperature, coherent, tunable, directional, and intense THz radiation sources.

Manipulating Cherenkov Radiation and Smith–Purcell Radiation by Artificial Structures

“…In addition to the superradiant Smith–Purcell emission arising from the coherent interference, the radiation intensity can also be enhanced by the resonance effect. Several studies have shown that for a metallic grating, the Smith–Purcell radiation can be enhanced at the resonant frequency of the grating . By designing the geometry parameter of the groove of the grating, we can adjust the resonance frequency of Smith–Purcell radiation.…”

Chiral Plasmons Enable Coherent Vortex Smith–Purcell Radiation

“…[33] Whereafter, several studies demonstrated that coherent SPR could be generated from the graphene SPPs. [34,35] Yet, in the microwave and THz regimes, it necessitates structural surfaces to support the spoof surface plasmons (SSPs) behaving like SPPs with enhanced field intensity. [36] Based on various artificial structures, SSPs possess capabilities of flexible customization and are utilized to improve the performance of SPR, whereas the chiral ones carrying OAM have not been fully exploited to cast V-SPR.…”