Enhanced Smith-Purcell radiation from a bigrating surface through multiplasmon excitation

Abstract

A theory is presented of the Smith-Purcell diffraction radiation from a beam of point charges passing over a finitely conducting bigrating surface, with arbitrary orientation of the beam relative to the bigrating axes. The beam's field can resonantly excite one or more surface-plasmon polaritons, which the bigrating can then decouple into a single outward radiating wave at any given angle and frequency. This radiation, arising from the collective motion of the electrons in a surface plasmon, has been shown theoretically to enhance the radiated power by two or three orders of magnitude in the peak direction. Numerical implementation of the present theory has shown that there is an optimal grating height at which this surface-plasmon-enhanced radiation peak is at a maximum. This work has also shown that a sinusoidal bigrating, forming a rectangular lattice, can yield an added enhancement, through two-plasmon excitation, when compared to the radiation from a classical grating (periodic in one direction).