Abstract: | A new concept for shortening hard X‐ray pulses emitted from a third‐generation synchrotron source down to few picoseconds is presented. The device, called the PicoSwitch, exploits the dynamics of coherent acoustic phonons in a photo‐excited thin film. A characterization of the structure demonstrates switching times of ≤ 5 ps and a peak reflectivity of ~10?3. The device is tested in a real synchrotron‐based pump–probe experiment and reveals features of coherent phonon propagation in a second thin film sample, thus demonstrating the potential to significantly improve the temporal resolution at existing synchrotron facilities. |