Tabletop attosecond X-rays in the water window

Abstract In recent years, a new generation of attosecond driving lasers centered at ~ 1.7 μm based on carrier-envelope phase stabilized Optical Parametric Amplification have enabled the generation of X-ray pulses reaching the water window (282–533 eV), which is of great interest given their applications in the study of electron dynamics in atoms, molecules and condensed matter containing carbon, nitrogen, oxygen and other important elements. Various gating methods emanated isolated attosecond pulses for pump-probe experiments. Atto-chirp compensation has made the X-ray pulses at the carbon K-edge as short as 53 attoseconds. Novel spectral phase retrieval schemes such as neural network have been implemented to attosecond streaking techniques for faster and more reliable characterization of X-ray pulses. The water window X-ray sources have been applied to ultrafast measurements, such as attosecond transient absorption spectroscopy and photoelectron spectroscopy with element specificity and sub-optical-cycle temporal resolution.