Copper boost to an atomic laser

Generating coherent X-rays with short-wavelength lasers has been a long-standing goal in X-ray science. Previously, an atomic laser based on neon atoms and pumped by an X-ray free-electron laser had been developed for soft X-rays. Hitoki Yoneda et al. use a solid copper target to achieve an atomic laser in the hard X-ray regime, at 1.54 Å. The target is ionized by SACLA, the SPring-8 Angstrom Compact Free Electron Laser, to achieve strong amplified spontaneous emission. The resulting atomic laser generates an X-ray beam that is superior to the pumping X-ray free-electron laser pulse. Its wavelength is almost ten times shorter than previously reported and will open many opportunities for ultrafast X-ray spectroscopy and quantum optics.