In conventional X-ray sources, the radiation is emitted from a large spot into all directions and over a broad energy range, leading to a relatively modest resolution. X-rays generated in synchrotrons provide much higher resolution. However, these devices are typically huge and highly expensive.

Laszlo Veisz, Max Planck Institute for Quantum Optics (MPQ), Garching, Germany, and colleagues have developed a laser-driven X-ray source generating X-rays of similar quality to synchroton radiation which can image structures of varying composition with a resolution of less than 10 µm. The wavelenght of the emitted light can also be tuned over a wide range. This opens up a range of promising perspectives for this new technique in materials science, biology, and medicine.

The techniques uses a laser pulse of 25 fs and 60 TW of power to accelerate electrons to very high energy. A second laser pulse forces the electrons into an undulating motion. Highly energetic electrons that are forced to oscillate emit radiation in the form of X-ray photons with wavelengths as short as 0.03 nm. In addition, in these experiments, the higher harmonics entrained on the electron motions by the light field could be detected directly in the X-ray spectrum – a feat that has been attempted many times on conventional particle accelerators without succes.

• Tunable All-Optical Quasimonochromatic Thomson X-Ray Source in the Nonlinear Regime,
  K. Khrennikov, J. Wenz, A. Buck, J. Xu, M. Heigoldt, L. Veisz, S. Karsch,
  Phys. Rev. Lett. 2015, 114, 195003.
  DOI: 10.1103/PhysRevLett.114.195003