With durations approaching the timescales of fundamental atomic and molecular processes, ultrafast optical pulse generation is revolutionising biology, physics and chemistry in laboratories around the world. With the help of pulsed lasers, time-resolved spectroscopy makes it possible to view highly dynamic processes of molecular motion and electron transfer between atoms. Incorporating suitable DOEs with high temporal coherence in the optical field of a laser beam is the basis for further progress in spectroscopic techniques. Within the EU-funded project 3D RZP (The advanced instrumentation on the basis of 3D RZP for modern UV and X-ray sources), scientists developed high-quality optical components for time-resolved spectroscopy covering the entire ultraviolet (UV) and X-ray regions. DOEs at total external reflection are the only optical components that can be used for focusing high-intensive radiation. Spatial energy dispersion was achieved by the use of Fresnel zone plates. Femtoslicing facilities at synchrotron radiation storage rings are one of the few sources of sub-picosecond pulsed X-rays covering the entire X-ray science photon energy range. In particular, BESSY's femtoslicing facility in Germany is the only set-up allowing studies of ultrafast dynamics with soft X-ray pulses down to approximately 100 fs pulse duration and variable linear and circular polarisation. The increase of coherence length, however, comes at the expense of the photon flux per pulse. To address this, the 3D RZP team successfully built and commissioned a novel type of a high-flux femtoslicing beamline that proved at least 20 times more efficient. The unique set-up was based on the use of an array of off-axis reflection zone plates (RZPs) that covered a large bandwidth. The newly developed RZPs also found use in time-resolved X-ray absorption spectroscopy of biological materials using free electron lasers. The spectrometer consisted of up to 100 RZPs on a silicon substrate. Scientists also reviewed and modified existing microfabrication technology with respect to accuracy, uniformity and reproducibility of DOEs. A process of precise plasma etching of silicon was developed for the first time. The team elaborated innovative techniques based on the application of milling ion etching for profiling DOE fine structures with lateral periods down to 100 nm. DOEs are essential components for investigations with synchrotron, free electron laser and high harmonic generator radiation. Covering high energies of the X-ray photons up to 20 keV, the newly developed DOEs will aid in the design of customised optical systems.
Chemical reactions, diffractive optical elements, time-resolved spectroscopy, 3D RZP, reflection zone plates