Time-resolved Pendellosung oscillations from impulsively strained crystals

Summary form only given. We have recently demonstrated coherent control of X-ray pulses in the Laue geometry. In the Laue geometry, two mutually coherent diffracted beams are excited simultaneously. These experiments demonstrate a (sub)nanosecond X-ray switch in which the distribution of energy from the input beam into and between the two diffracted beams is controlled by a coherent acoustic phonon pulse (excited by an ultrafast laser). In those experiments, the diffracting geometry was asymmetric, resulting in the LA phonons being partially polarized along the reciprocal lattice vector. In this case strong coupling is expected between the phonons and the diffracted beams. Here we extend this work by reporting on the similar experiments in the symmetric Laue geometry. In this case the LA phonons are polarized perpendicular to the reciprocal lattice vector; nonetheless, strong coupling between the phonon and the lattice is observed. Oscillations in the diffracted beams (Pendellosung) are consistent with the coherent acoustic phonons acting as a localized interface which modifies the populations of the two wave-solutions. These results may be scalable to subpicosecond time-scales using coherent optical phonons.