Tuning Smith-Purcell radiation by rotating a metallic nanodisk array

Smith-Purcell radiation (SPR) refers to the far-field, strong, spike radiation generated by the interaction of the evanes-cent Coulomb field of the moving charged particles and the surrounding medium. In applying SPR for particle detection and nanoscale on-chip light sources, wavelength tunability is desired. Here we report on tunable SPR achieved by mov-ing an electron beam parallel to a two-dimensional (2D) metallic nanodisk array. By in-plane rotating the nanodisk array, the emission spectrum of the SPR splits into two peaks, with the shorter-wavelength peak blueshifted and the longer-wavelength one redshifted by increasing the tuning angle. This effect originates from the fact that the elec-trons fly effectively over a one-dimensional (1D) quasicrystal projected from the surrounding 2D lattice, and the wave-length of SPR is modulated by quasiperiodic characteristic lengths. The experimental data are in agreement with the simulated ones. We suggest that this tunable radiation pro-vides free-electron-driven tunable multiple photon sources at the nanoscale. (c) 2023 Optica Publishing Group

Automated summary

Smith-Purcell radiation (SPR) is the far-field, strong, spike radiation generated by the interaction of the evanes-cent Coulomb field of the moving charged particles and the surrounding medium. In this study, tunable SPR is achieved by moving an electron beam parallel to a 2D metallic nanodisk array. By rotating the nanodisk array, the emission spectrum of SPR splits into two peaks with different wavelengths, which can be tuned by increasing the tuning angle.