An atomic laser operating at the shortest wavelength yet achieved has been created by bombarding a copper foil with two X-ray pulses tuned to slightly different energies. The results may lead to ultrastable X-ray laser.
The technology is not yet ready for primetime, Young, notes, the laser did not achieve saturation and some tests, such as angular divergence were not performed. Still, she notes, the work done by the team and others suggests that researchers will very soon be able to make use of very-short wavelength based lasers, offering perhaps, unprecedented resolution and atomic measurement capabilities.
Since the invention of the first lasers in the visible-light region, research has aimed to produce short-wavelength lasers that generate coherent X-rays; the shorter the wavelength, the better the imaging resolution of the laser and the shorter the pulse duration, leading to better temporal resolution in probe measurements. Recently, free-electron lasers based on self-amplified spontaneous emission have made it possible to generate a hard-X-ray laser (that is, the photon energy is of the order of ten kiloelectronvolts) in an ångström-wavelength regime, enabling advances in fields from ultrafast X-ray spectrosopy to X-ray quantum optics. An atomic laser based on neon atoms and pumped by a soft-X-ray (that is, a photon energy of less than one kiloelectronvolt) free-electron laser has been achieved at a wavelength of 14 nanometers. Here, we use a copper target and report a hard-X-ray inner-shell atomic laser operating at a wavelength of 1.5 ångströms. X-ray free-electron laser pulses with an intensity of about 10^19 watts per square centimeter tuned to the copper K-absorption edge produced sufficient population inversion to generate strong amplified spontaneous emission on the copper Kα lines. Furthermore, we operated the X-ray free-electron laser source in a two-colour mode9, with one colour tuned for pumping and the other for the seed (starting) light for the laser.
XFEL pulses are generated with undulators in single-color mode (the ASE experiment) (a) or two-color mode (the seeding experiment) (b). The two-stage focusing system generates, on average, a 120-nm focusing spot
SOURCES – Physorg, Nature,