Abstract
We present a novel design for an ultracompact, passive light source capable of generating ultraviolet and X-ray radiation, based on the interaction of free electrons with the magnetic near-field of a ferromagnet. Our design is motivated by recent advances in the fabrication of nanostructures, which allow the confinement of large magnetic fields at the surface of ferromagnetic nanogratings. Using ab initio simulations and a complementary analytical theory, we show that highly directional, tunable, monochromatic radiation at high frequencies could be produced from relatively low-energy electrons within a tabletop design. The output frequency is tunable in the extreme ultraviolet to hard X-ray range via electron kinetic energies from 1 keV to 5 MeV and nanograting periods from 1 μm to 5 nm. The proposed radiation source can achieve the tunability and monochromaticity of current free-electron-driven sources (free-electron lasers, synchrotrons, and laser-driven undulators), yet with a significantly reduced scale, cost, and complexity. Our design could help realize the next generation of tabletop or on-chip X-ray sources.
Highlights
We present a novel design for an ultracompact, passive light source capable of generating ultraviolet and X-ray radiation, based on the interaction of free electrons with the magnetic near-field of a ferromagnet
T abletop sources of extreme-ultraviolet and X-ray radiation are potentially useful for a wide variety of applications in medicine, engineering, and the natural sciences, ranging from medical therapy and diagnostics to X-ray imaging and spectroscopy, particle detection, and photolithography.[1−4] Free-electron-driven light sources are promising schemes for realizing this goal
There have been a number of proposals for compact free-electron sources relying on various spontaneous emission effects, such as Cherenkov and transition radiation sources[7] and SmithPurcell emitters,[8−13] but these are limited to frequencies around the extreme ultraviolet, where the material response becomes insubstantial
Summary
Sophie Fisher − Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States; orcid.org/0000-0002-7276-7257; Email: sefisher@ mit.edu. Charles Roques-Carmes − Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States. Nicholas Rivera − Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States; orcid.org/0000-0002-8298-1468. Marin Soljacǐ ć − Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States. Recent progress has been made in high-energy on-chip accelerators,[29,30] which, when combined with our design, could enable an ultracompact, fully on-chip X-ray light source. An interesting topic for future research is the possibility of a nanoscale free-electron laser, in which electrons bunch coherently via self-amplified spontaneous emission, allowing. Derivation of the spectral angular power of emitted radiation from a single electron, spectral angular power of emitted radiation from a bunched electron beam, and radiation due to brehmsstrahlung (PDF)
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