Imaging ultrafast dynamical diffraction wavefronts in strained Si with coherent X-rays

TL;DR

This paper demonstrates how small surface strains in silicon crystals can tune ultrafast X-ray diffraction echoes, advancing the development of strain-engineered X-ray optics for improved beam control.

Contribution

It presents the first coherent X-ray imaging measurement of diffraction echoes in strained silicon and shows how surface strain can control their temporal delay.

Findings

Small surface strain tunes diffraction echo delay

First coherent imaging of diffraction echoes in silicon

Potential for strain-engineered X-ray optics

Abstract

Dynamical diffraction effects in single crystals produce highly monochromatic parallel X-ray beams with a mutual separation of a few micrometer and a time-delay of a few fs -the so-called echoes. This ultrafast diffraction effect is used at X-ray Free Electron Lasers in self-seeding schemes to improve beam monochromaticity. Here, we present a coherent X-ray imaging measurement of echoes from Si crystals and demonstrate that a small surface strain can be used to tune their temporal delay. These results represent a first step towards the ambitious goal of strain-tailoring new X-ray optics.