Improved Smith-Purcell radiation owing to field localization and reflection of surface plasmon polaritons in grating substrate

Abstract Study of Smith-Purcell radiation (SPR) shows that optimal grating depth (groove depth) increases as excitation electrons energy decreases. Difficulty in achieving oversized groove depth grating leads to weak radiation in low energy excitation condition. Due to field localization and reflection of surface plasmon polaritons (SPPs), which significantly decreases optimal groove depth, radiation performance is comprehensively improved in SPPs materials substrate grating. This research shows that the greater the confinement factor of SPPs materials substrate, the more the optimized groove depth decreases. Simulation results show that 10.5 keV (0.2c, c is light speed) electrons exciting the grating of 90 nm period 0.1 duty cycle and 27 nm groove depth, the radiation intensity in Au substrate grating is more than 400 times of PEC grating. Comparing with Au grating, radiation is point frequency enhancement by plasmon while in Au substrate grating it is broadband improvement. The results presented here are of great significance of developing miniature, integratable, broadband, high-power-density light radiation sources at room temperature.