Graphene Metamaterials for Intense, Tunable, and Compact Extreme Ultraviolet and X‐Ray Sources

Abstract

The interaction of electrons with strong electromagnetic fields is fundamental to the ability to design high‐quality radiation sources. At the core of all such sources is a tradeoff between compactness and higher output radiation intensities. Conventional photonic devices are limited in size by their operating wavelength, which helps compactness at the cost of a small interaction area. Here, plasmonic modes supported by multilayer graphene metamaterials are shown to provide a larger interaction area with the electron beam, while also tapping into the extreme confinement of graphene plasmons to generate high‐frequency photons with relatively low‐energy electrons available from tabletop sources. For 5 MeV electrons, a metamaterial of 50 layers and length 50 µm, and a beam current of 1.7 µA, it is, for instance, possible to generate X‐rays of intensity 1.5 × 107 photons sr−1 s−1 1%BW, 580 times more than for a single‐layer design. The frequency of the driving laser dynamically tunes the photon emission spectrum. This work demonstrates a unique free‐electron light source, wherein the electron mean free path in a given material is longer than the device length, relaxing the requirements of complex electron beam systems and potentially paving the way to high‐yield, compact, and tunable X‐ray sources.

Tunable free-electron X-ray radiation from van der Waals materials

“…Such smaller scale undulators enable reducing the levels of electron acceleration, while still resulting in tunable X-ray generation. More recent proposals rely on shrinking the undulating periodicity even further by leveraging the high electromagnetic confinement in graphene surface plasmons [34], metasurfaces [35], metamaterials [36] and nanophotonic vacuum fluctuations [37]. Our study explores different phenomena that lead to X-ray generation from free electrons, in which the electron undulation is done at the ultimate periodicity: that of the atomic crystal lattice.…”

Chiral Graphene Hybrid Materials: Structures, Properties, and Chiral Applications

“…Their use potentials in solar‐thermal energy conversion, wave absorption, and electromagnetic shielding also cause a lot of interest. [ 313–315 ] It is thus indicative that if graphene‐based metamaterials are combined with chirality, unprecedented materials with new phenomena and new utility may be highly anticipated. Graphene coupled with chirality provides huge opportunities for developing the newly emerging chiral metamaterials.…”

Free-Electron Radiation Engineering via Structured Environments

“…These unique features facilitate the research of free-electron radiation in the platform of graphene [35][36][37][38][39]. A recent theoretical work has revealed the dynamical generation process of surface plasmons by a free electron perpendicularly penetrating through the graphene as shown in Figure 1(a) [40,41].…”