Spectral and spatial shaping of Smith Purcell Radiation

TL;DR

This paper introduces a method to control the spectral and spatial distribution of Smith Purcell radiation using complex gratings, enabling tailored electromagnetic sources and focusing capabilities in challenging spectral ranges.

Contribution

It presents a novel approach to shape Smith Purcell radiation spectra and spatial profiles using engineered gratings, both theoretically and experimentally.

Findings

Multiple peak spectra with controlled widths are achievable.

Spectral and spatial shaping is demonstrated experimentally.

The method enables focused radiation in spectral ranges lacking lenses.

Abstract

The Smith Purcell effect, observed when an electron beam passes in the vicinity of a periodic structure, is a promising platform for the generation of electromagnetic radiation in previously-unreachable spectral ranges. However, most of the studies of this radiation were performed on simple periodic gratings, whose radiation spectrum exhibits a single peak and its higher harmonics predicted by a well-established dispersion relation. Here, we propose a method to shape the spatial and spectral far-field distribution of the radiation using complex periodic and aperiodic gratings. We show, theoretically and experimentally, that engineering multiple peak spectra with controlled widths located at desired wavelengths is achievable using Smith-Purcell radiation. Our method opens the way to free-electron driven sources with tailored angular and spectral response, and gives rise to focusing functionality for spectral ranges where lenses are unavailable or inefficient.