Our research activities are dedicated towards the generation, control and application of ultrashort coherent soft X-ray pulses in “table-top” experiments.
The table-top coherent soft X-ray source in our laboratory is based on High Harmonic Generation from a gas target driven by a few-cycle, high repetition rate Ti:Sa laser amplifier. This is source is generating coherent radiation with individual pulses or pulse trains with attosecond (10-18 sec) to femtosecond (10-15) pulse duration in the Extreme Ultraviolet spectral range up to a photon energy of 100 eV (12.4 nm wavelength), but extendable to multi-100 eV in the future.
An important part of our research is focused on the development of dispersive multilayer mirror optics for spectral filtering, steering and phase control of attosecond soft X-ray pulses in a photon energy range from 30 eV to about 0.5 keV. This includes the development of a-periodic multilayer systems consisting of tens to hundreds of nano-layers of various metal and semiconductor materials as broad-band dispersive reflection coatings as well as the development of diffractive nano-focusing and nano-imaging optics.
Application experiments are utilizing the spectrally dispersed pulses for time, energy and spatially resolved Time-of-Flight Photoelectron Emission Microscopy on metallic nanostructures on surfaces. This 4D microscopy is capable of investigating collective electron dynamics in nanostructures commonly referred to as Surface Plasmon Dynamics, as well as localized near-field enhancements or localized charge transfers on surfaces.
The spatial coherence properties of the radiation are utilized in the development of a second application experiment on Scanning Transmission High Harmonic Microscopy (STHHM) aiming for sub-100 nm spatial soft X-ray imaging of transmissive samples.