Atomic inner-shell X-ray laser at 1.46 nanometres pumped by an X-ray free-electron laser

Abstract

Since the invention of the laser more than 50 years ago, scientists have striven to achieve amplification on atomic transitions of increasingly shorter wavelength. The introduction of X-ray free-electron lasers makes it possible to pump new atomic X-ray lasers with ultrashort pulse duration, extreme spectral brightness and full temporal coherence. Here we describe the implementation of an X-ray laser in the kiloelectronvolt energy regime, based on atomic population inversion and driven by rapid K-shell photo-ionization using pulses from an X-ray free-electron laser. We established a population inversion of the Kα transition in singly ionized neon at 1.46 nanometres (corresponding to a photon energy of 849 electronvolts) in an elongated plasma column created by irradiation of a gas medium. We observed strong amplified spontaneous emission from the end of the excited plasma. This resulted in femtosecond-duration, high-intensity X-ray pulses of much shorter wavelength and greater brilliance than achieved with previous atomic X-ray lasers. Moreover, this scheme provides greatly increased wavelength stability, monochromaticity and improved temporal coherence by comparison with present-day X-ray free-electron lasers. The atomic X-ray lasers realized here may be useful for high-resolution spectroscopy and nonlinear X-ray studies.

Two-colour hard X-ray free-electron laser with wide tunability

“…For example, Vinko et al 4 reported creation of solid-density plasma with a temperature above 10 6 K, which has been pumped by 1.8 keV XFEL light and probed by Ka emission spectra spreading over 200 eV at photon energies around 1.6 keV. Rohringer et al 5 found an amplification of 849 eV Ka emission from neon atoms in population inverted conditions, which are generated with irradiation of intense 960 eV XFEL light. Although these experiments have been performed by using a single XFEL beam, a two-colour double-pulse (TCDP) XFEL with a wide photon energy range and precisely controlled delay is desirable for investigating phenomena in a time-energy domain.…”

“…These processes are mostly driven by ultrafast transition of inner-shell electrons with large energy transfers [3][4][5] . For example, Vinko et al 4 reported creation of solid-density plasma with a temperature above 10 6 K, which has been pumped by 1.8 keV XFEL light and probed by Ka emission spectra spreading over 200 eV at photon energies around 1.6 keV.…”

Atomic inner-shell radiation seeded free-electron lasers

“…The introduction of XFEL makes it possible to pump new atomic innershell XRL [32][33][34][35] with ultrashort pulse duration, extreme spectral brightness, and full temporal coherence. Experimentally, in 2012, An atomic laser based on neon atoms and pumped by a soft XFEL has been achieved at a wavelength of 14.6 ångströms in Linac Coherent Light Source [36]; in 2015, the SPring-8 Angstrom Compact Free Electron Laser use a copper target and report a hard X-ray atomic inner-shell laser operating at a wavelength of 1.5 ångströms [37]. Experimental results show that temporal coherence was greatly improved in the pumped neon (Ne) and copper (Cu) medium using XFEL.…”

Determination of multiwavelength anomalous diffraction coefficients at high x-ray intensity

“…X-ray free-electron lasers (XFELs) [1,2,3,4], which feature ultraintense and ultrashort x-ray pulses, have brought us a new way of thinking about x-ray-matter interaction and have an impact on various scientific fields, such as atomic and molecular physics [5,6,7], x-ray optics [8], material science [9], astrophysics [10], and molecular biology [11,12,13,14,15]. Many collections and reviews on scientific achievements with XFELs are available [16,17,18], including the current special issue on "Frontiers of FEL Science.…”