Smith Purcell Radiation Generation from the VUV to the Near IR: Tunable Emission from Nanophotonic Structures in a Modified SEM*

The conventional Smith-Purcell effect describes light emission due to collective excitation induced by free electrons coupling to the electromagnetic modes of a periodic structure. We present experimental results on a range of samples from sub 100 nm pitch gratings to periodic high aspect ratio silicon nanowire structures to engineered metasurfaces using low-energy electrons (2.5 -40 keV) in a modified scanning electron microscope. We show that samples not commonly thought to be appropriate for Smith Purcell emission (because of theoretical and experimental misbeliefs), namely non-electrically conductive structures, can be strong emitters. This is observed experimentally and now also predicted theoretically. The possibility of producing tunable short wavelength emission from relatively low-energy electrons (accessible with regular scanning or transmission electron microscopes) is a promising field of research, because of its numerous applications and the potential emergence of recoil physics in table-top experiments.