A central challenge in several scientific disciplines is the invention of novel concepts for radiation generation in spectral ranges beyond those currently accessible by existing technologies, particularly in terahertz, hard-ultraviolet, and x-ray.

Current technology allows us to generate and detect electromagnetic signals, in wide spectral ranges from radio waves and microwaves, through infrared and visible light, to X-ray radiation. Around each of these spectral ranges entire industries have emerged: radio communication, cellular phones, optical communication, display screens and lighting; medical imaging (respectively). Each of these innovations have been made possible by groundbreaking discoveries in fundamental physics.

Nonetheless, given the unparalleled importance of these spectral bands, it is astounding that entire sectors of the electromagnetic spectrum remain practically out of technological and scientific reach. Chief among these sectors are the terahertz, hard-UV, and soft xray ranges. Unlocking the exceptional scientific and industrial potential of these spectral ranges requires non-trivial progress in several fundamental areas of physics and material science.

Tunable X-ray emission from free-electrons in designer atomic crystals

Relevant papers

M. Shentcis, A. K. Budniak, X. Shi, R. Dahan, Y. Kurman, M. Kalina, H. Herzig Sheinfux, M. Blei, M. K. Svendsen, Y. Amouyal, F. Koppens, S. Tongay, K. S. Thygesen, E. Lifshitz, F. J. García de Abajo, L. J. Wong, and I. KaminerTunable free-electron X-ray radiation from van der Waals materials,  Nature Photonics 14, 686–692 (2020) (Supplementary materials)   §  Selected for News & Views in Nature Photonics.  Highlighted on the Phys.Org.
L. J. Wong, N. Rivera, C. Murdia, T. Christensen, J. D. Joannopoulos, M. Soljačić, and I. KaminerCoherent control of quantum electrodynamical processes with shaped electron wavepackets,  Nature Commun. 12, 1700 (2021) (Supplementary materialsPeer review file)
S. Fisher, C. Roques-Carmes, N. Rivera, L. J. Wong, I. Kaminer, M. Soljačić, Monochromatic X-ray source based on scattering from a magnetic nanoundulatorACS Photonics 7, 1096 (2020)
N. Rivera, L. J. Wong, J. D. Joannopoulos, M. Soljačić & I. Kaminer, Light emission based on nanophotonic vacuum forces, Nature Physics,  (2019).
(Supplementary materials).§ Highlighted in physicsworld
A. Pizzi, G. Rosolen, L. J. Wong, R. Ischebeck, M. Soljačić, T. Feurer, and I. Kaminer, Graphene Metamaterials for Intense, Tunable, and Compact Extreme Ultraviolet and X-Ray SourcesAdv. Sci., 1901609 (2019).
(Supplementary materials)
G. Rosolen, L. J. Wong, N. Rivera, B. Maes, M. Soljačić and I. KaminerVersatile metasurface-based free electron multi-harmonic light source, Light Sci. Appl., 7,  64 (2018).
(Supplementary materials)
L. J. Wong†, I. Kaminer†, O. Ilic, J. D. Joannopoulos, and M. Soljačić, Towards Graphene Plasmon-Based Free-Electron IR to X-ray Sources, Nature Photonics, 10, 46 (2016).
(Supplementary materials)
§ Featured on the MIT front page, and was also selected for News & Views in Nature Photonics.
§ Featured on A*STAR Research Highlight.