Graphene plasmonics : ultra-tunable graphene light source

Free-electron-based light sources have long attracted interest due to their continuous tunability that has been demonstrated to extend across the electromagnetic spectrum from millimetre waves and microwaves through the infrared and visible to ultraviolet and X-ray regions. However this intrinsic tunability, particularly at short wavelengths, usually involves sources that are large and costly. The prospect of a compact, continuously tunable light source with the capability to generate short-wavelength ultraviolet and even X-ray light is an exciting one for many scientific, medical and engineering applications

Cavity resonator free electron lasers as a source of stable attosecond pulses

High-gain Free Electron Laser amplifiers are a potential source of single X-ray attosecond pulses and Attosecond Pulse Trains. Single-pulse output from short electron bunches is prone to significant power and arrival-time fluctuations. A Mode Locked Optical Klystron configuration of the FEL amplifier predicts generation of a frequency comb that may be locked to give APT output. In this paper it is shown using numerical simulations that a low feedback (so-called Regenerative Amplifier) FEL cavity resonator configuration can significantly improve output stability for single-pulse operation. The MLOK configuration may also be used in a cavity resonator to generate a frequency comb with spacing much greater than those of the axial cavity modes. As with the MLOK amplifier case, these modes can lock to generate a stable pulse train, each of a few optical cycles