Analysis of Smith-Purcell radiation in optical region

Smith-Purcell radiation (SPR), emitted when an electron beam is traveling above a metallic grating, has attracted a lot of attention as a source of electromagnetic (EM) radiation in the millimeter to visible spectrum. We conducted a theoretical investigation of SPR in the optical region using a two-dimensional finite-difference time-domain (FDTD) method. The permittivity of metal was represented using the Drude model. During the simulation, we observed three types of EM radiations when an electron bunch passes above a metal grating. We think these three types of EM radiation were basic SPR, original surface plasmon polariton (SPP), and mimic-SPP, caused by the periodic grating structure. Our observations were in accordance with analytical models of original SPP and mimic-SPP EM radiation.