Ultrafast manipulation of hard x-rays by efficient Bragg switches

We experimentally demonstrate efficient switching of the hard x-ray Bragg reflectivity of a SrRuO(3) /SrTiO(3) superlattice by optical excitation of large-amplitude coherent acoustic superlattice phonons. The rocking curve changes drastically on a 1 ps timescale. The (0 0 116) reflection is almost extinguished (Delta R/R(0)=-0.91), while the (0 0 118) reflection increases by more than an order of magnitude (Delta R/R(0)=24.1). The change of the x-ray structure factor depends nonlinearly on the phonon amplitude, allowing manipulation of the x-ray response on a timescale considerably shorter than the phonon period. Numerical simulations for a superlattice with slightly changed geometry and realistic parameters predict a switching-contrast ratio Delta R/R(0) of 700 with high reflectivity. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3402773]