Broadband enhancement of cherenkov radiation using dispersionless plasmons

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, we report a general approach 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 electronvolts), without resorting to relativistic particles.Ministry of Education (MOE)National Research Foundation (NRF)Published versionThe work at Zhejiang University was sponsored in part by the National Natural Science Foundation of China (NNSFC) (Nos. 61625502, 11961141010, 61975176, and 62175212), the Top-Notch Young Talents Program of China, the National Natural Science Fund for Excellent Young Scientists Fund Program (Overseas) of China, Zhejiang University Global Partnership Fund, and the Fundamental Research Funds for the Central Universities (No. 2021FZZX001- 19). The work at Nanyang Technological University was sponsored in part by Singapore Ministry of Education (Nos. MOE2018-T2-2-189 (S), MOE2018-T2-1-022 (S), and MOE2016-T3-1-006), A*Star Advanced Manufacturing and Engineering Individual Research Grant (No. A20E5c0095) and Programmatic Funds (No. A18A7b0058), National Research Foundation Singapore Competitive Research Program (Nos. NRF-CRP22-2019- 0006 and NRF-CRP23-2019-0007)