Broadband high-resolution X-ray frequency combs

• DOI: 10.1038/nphoton.2014.113
• Publication Date: 2014-05-30T11:18:42Z
• Authors: Stefano M. Cavaletto; Zoltán Harman; Christian Ott; Christian Buth; Thomas Pfeifer; Christoph H. Keitel
• Keywords: 0301 basic medicine; 03 medical and health sciences; Atomic Physics (physics.atom-ph); Research group Z. Harman – Division C. H. Keitel; 0103 physical sciences; FOS: Physical sciences; 01 natural sciences; 7. Clean energy; Physics - Atomic Physics

Optical frequency combs have had a remarkable impact on precision spectroscopy. Enabling this technology in the x-ray domain is expected to result in wide-ranging applications, such as stringent tests of astrophysical models and quantum electrodynamics, a more sensitive search for the variability of fundamental constants, and precision studies of nuclear structure. Ultraprecise x-ray atomic clocks may also be envisaged. In this work, an x-ray pulse-shaping method is put forward to generate a comb in the absorption spectrum of an ultrashort high-frequency pulse. The method employs an optical-frequency-comb laser, manipulating the system's dipole response to imprint a comb on an excited transition with a high photon energy. The described scheme provides higher comb frequencies and requires lower optical-comb peak intensities than currently explored methods, preserves the overall width of the optical comb, and may be implemented by presently available x-ray technology.