Attosecond transient absorption spectroscopy is still a relatively young discipline of attosecond science. Even though femtosecond transient absorption spectroscopy is a well-known and established experimental technique, it required the creation of coherent XUV bursts of attosecond duration with higher-order harmonic generation (HHG) to extend the technique into the attosecond regime. As an all optical technique, it is based on the cross-correlation of pulsed XUV radiation with femtosecond infrared (IR) pulses in the sample under investigation and the subsequent detection of the transmitted radiation. Its high temporal resolution allows to explore electron dynamics on their natural time scale.
In this work, we examine the optical properties of He in the XUV spectral range in different experiments and with the help of numerical simulations. Moreover, we present attosecond solid-state transient absorption spectroscopy in a polycrystalline diamond membrane. Our experimental data reveal the fully reversible modification and control of the optical transmission of polycrystalline diamond in the XUV spectral range with the help of the femtosecond IR pulse.