An atomic inner-shell laser that produces a stable, high-quality hard-x-ray beam at a 1.5 Å wavelength has been reported by a team of researchers from the University of Electro-Communications (Tokyo, Japan), RIKEN, (Hyogo, Japan), the Japan Synchrotron Radiation Research Institute (Hyogo, Japan), Osaka University (Osaka, Japan), the University of Tokyo (Tokyo, Japan), and Kyoto University (Kyoto, Japan). "Inner shell" refers to the fact that the laser transition occurs in an inner electron shell of the lasing material, leading to the very high-energy photons. The 1.5 Å wavelength is almost 10 times shorter than that of previously reported atomic lasers. As a result, the new laser can potentially be used to view single molecules.
The atomic laser, which is pumped by a free-electron laser at RIKEN of longer wavelength and far lower beam quality than the atomic laser, is based on copper atoms. The researchers exposed copper foil to two x-ray pulses with intensities of about 1019 W/cm2; one pulse was tuned to the copper K-absorption edge as a pump source and the other tuned as a seed for the main laser beam. The team found that using the pumped copper medium in combination with seeding greatly enhanced the coherence and energy-extraction efficiency of the short-wavelength beam. The team hopes to commercialize the laser, along with associated instrumentation, as a high-coherence, ultrahigh-resolution x-ray imaging system. Reference: H. Yoneda et al., Nature,524 (2015); doi:10.1038/nature14894.
