Broadband Enhancement of Cherenkov Radiation Using Dispersionless Plasmons

Abstract

As one of leading technologies in detecting relativistic particles, Cherenkov radiation plays an essential role in modern high‐energy and particle physics. However, the limited photon yield in transparent dielectrics makes efficient Cherenkov radiation only possible with high‐energy particles (at least several MeV). This restriction hinders applications of Cherenkov radiation in free‐electron light source, bio‐imaging, medical therapy, etc. Broadband enhancement of Cherenkov radiation is highly desired for all these applications, but still widely acknowledged as a scientific challenge. To this end, a general approach is reported to enhance the photon yield of Cherenkov radiation using dispersionless plasmons. Broadband dispersionless plasmons can be realized by exploiting either the acoustic nature of terahertz plasmons in a graphene‐based heterostructure or the nonlocal property of optical plasmons in a metallodielectric structure. When coupled to moving electrons, such dispersionless plasmons give rise to a radiation enhancement rate more than two orders of magnitude (as compared with conventional Cherenkov radiation) over an ultrabroad frequency band. Moreover, since the phase velocity of dispersionless plasmons can be made as small as the Fermi velocity, giant radiation enhancements can be readily induced by ultralow‐energy free electrons (e.g., with a kinetic energy down to 3 eV), without resorting to relativistic particles.

2D Material Infrared Photonics and Plasmonics

“…As shown in Figure g, dispersionless phonon polariton is supported in a graphene-based heterostructure or non-local metallo­dielectric structure. It gives rise to a radiation enhancement rate of more than 2 orders of magnitude over an ultra-broad frequency band compared with conventional CR . The CR effect has also been theoretically predicted in some other 2D materials and hybrid systems, such as WSe 2 . , …”

“…It gives rise to a radiation enhancement rate of more than 2 orders of magnitude over an ultra-broad frequency band compared with conventional CR. 390 The CR effect has also been theoretically predicted in some other 2D materials and hybrid systems, such as WSe 2 . 391,392 Smith−Purcell Radiation.…”

“…Right: radiation spectrum per unit length of the electron path. Adapted with permission under a Creative Commons CC BY license from ref . Copyright 2022 Wiley-VCH.…”

Free-electron Brewster-transition radiation

“…The realization of such applications could boost the on-chip integration of free-electron light sources (e.g., in the terahertz/x-ray regimes) and to facilitate the direct detection of high-energy particles in outer space. Despite the long research history of free-electron radiation (24,(41)(42)(43)(44)(45)(46)(47)(48)(49)(50)(51), there remains a need for fundamentally different mechanisms to enhance the particle-matter interaction, especially for low-energy particles.…”

Recent advances of transition radiation: Fundamentals and applications

“…Due to the exotic particle-matter interactions, the free-electron radiation could occur under different scenarios. Correspondingly, there are various types of free-electron radiation, including Cherenkov radiation [16][17][18][19], transition radiation [20][21][22][23], Smith-Purcell radiation [24][25][26][27][28],…”