Smith-Purcell Radiation from Rough Surfaces

TL;DR

This paper investigates Smith-Purcell radiation from both periodic and rough inhomogeneous surfaces, deriving new dispersion relations and showing how surface polaritons contribute to radiation, especially on rough surfaces where multiple scattering occurs.

Contribution

It introduces new formulas for dispersion and spectral-angular intensity for periodic surfaces and highlights the role of surface polaritons in radiation from rough surfaces.

Findings

Two wavelengths emitted instead of one in periodic gratings.

Surface polaritons dominate radiation from rough surfaces.

Multiple scattering of polaritons converts them into photons.

Abstract

Radiation of a charged particle moving parallel to a inhomogeneous surface is considered. Within a single formalism periodic and random gratings are examined. For the periodically inhomogeneous surface we derive new expressions for the dispersion relation and the spectral-angular intensity. In particular, for a given observation direction two wavelengths are emitted instead of one wavelength of the standard Smith-Purcell effect. For a rough surface we show that the main contribution to the radiation intensity is given by surface polaritons induced on the interface between two media. These polaritons are multiply scattered on the roughness of surface and convert into real photons. The spectral-angular intensity is calculated and its dependence on different parameters is revealed.