Smith-Purcell Radiation from Low-Energy Electrons

TL;DR

This paper reports the experimental observation of visible light emission from low-energy electrons interacting with nanoscale gold gratings via the Smith-Purcell effect, demonstrating potential for compact, tunable light sources and advanced spectroscopic techniques.

Contribution

It presents the first observation of visible Smith-Purcell radiation from low-energy electrons using nanoscale gratings, expanding the operational parameters for SP-based light sources.

Findings

Visible SP radiation observed with electrons as low as 1.5 keV

Emission wavelength depends on grating pitch and electron energy

Experimental results agree with theoretical predictions

Abstract

Recent advances in the fabrication of nanostructures and nanoscale features in metasurfaces offer a new prospect for generating visible, light emission from low energy electrons. In this paper, we present the experimental observation of visible light emission from low-energy free electrons interacting with nanoscale periodic surfaces through the Smith-Purcell (SP) effect. SP radiation is emitted when electrons pass in close proximity over a periodic structure, inducing collective charge motion or dipole excitations near the surface, thereby giving rise to electromagnetic radiation. We demonstrate a controlled emission of SP light from nanoscale gold gratings with periodicity as small as 50 nm, enabling the observation of visible SP radiation by low energy electrons (1.5 to 6 keV), an order of magnitude lower than previously reported. We study the emission wavelength and intensity dependence on the grating pitch and electron energy, showing agreement between experiment and theory. Further reduction of structure periodicity should enable the production of SP-based devices that operate with even slower electrons that allow an even smaller footprint and facilitate the investigation of quantum effects for light generation in nanoscale devices. A tunable light source integrated in an electron microscope would enable the development of novel electron-optical correlated spectroscopic techniques, with additional applications ranging from biological imaging to solid-state lighting.