Coherent control of pulsed X-ray beams

• Published in: Nature (London) 2001-10, Vol.413 (6858), p.825-828
• Main Authors: DeCamp, M. F, Reis, D. A, Bucksbaum, P. H, Adams, B, Caraher, J. M, Clarke, R, Conover, C. W. S, Dufresne, E. M, Merlin, R, Stoica, V, Wahlstrand, J. K
• Format: Article
• Language: English
• Subjects: Crystals; Humanities and Social Sciences; letter; multidisciplinary; Physics; Science; X-ray diffraction; X-rays
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/35101560

Synchrotrons produce continuous trains of closely spaced X-ray pulses. Application of such sources to the study of atomic-scale motion requires efficient modulation of these beams on timescales ranging from nanoseconds to femtoseconds. However, ultrafast X-ray modulators are not generally available. Here we report efficient subnanosecond coherent switching of synchrotron beams by using acoustic pulses in a crystal to modulate the anomalous low-loss transmission of X-ray pulses. The acoustic excitation transfers energy between two X-ray beams in a time shorter than the synchrotron pulse width of about 100 ps. Gigahertz modulation of the diffracted X-rays is also observed. We report different geometric arrangements, such as a switch based on the collision of two counter-propagating acoustic pulses: this doubles the X-ray modulation frequency, and also provides a means of observing a localized transient strain inside an opaque material. We expect that these techniques could be scaled to produce subpicosecond pulses, through laser-generated coherent optical phonon modulation of X-ray diffraction in crystals. Such ultrafast capabilities have been demonstrated thus far only in laser-generated X-ray sources, or through the use of X-ray streak cameras.