Exotic radiation from a photonic crystal excited by an ultra-relativistic electron beam

TL;DR

This paper reports the observation of unconventional Smith-Purcell radiation from a photonic crystal excited by an ultra-relativistic electron beam, revealing direct photonic band excitation with unique spectral features.

Contribution

It demonstrates the direct excitation of photonic bands by an ultra-relativistic electron beam, leading to exotic radiation with distinct spectral properties.

Findings

Exotic radiation spectrum follows photonic band structure.

Contrast with conventional Smith-Purcell radiation.

Identification of radiation origin through experiment and theory.

Abstract

We report the observation of an exotic radiation (unconventional Smith-Purcell radiation) from a one-dimensional photonic crystal. The physical origin of the exotic radiation is direct excitation of the photonic bands by an ultra-relativistic electron beam. The spectrum of the exotic radiation follows photonic bands of a certain parity, in striking contrast to the conventional Smith-Purcell radiation, which shows solely a linear dispersion. Key ingredients for the observation are the facts that the electron beam is in an ultra-relativistic region and that the photonic crystal is finite. The origin of the radiation was identified by comparison of experimental and theoretical results.