Description
We perform high-resolution optical spectroscopy of a laser-produced plasma during a highharmonic-generation (HHG) process. This technique allows for non-invasive, in-situ plasma characterization, providing crucial parameters of an HHG process. For example, exact plasma parameters such as degree of ionization, neutral-to-ion ratio and electron density play an important role during the phase-matching process of the generated XUV beam. In this work we demonstrate how these parameters can be measured by means of spectralline shifting and broadening of an HHG medium gas. Furthermore, we generate, fully characterize and apply external plasmas to alter and control an HHG process by discharge driven between two electrodes inserted in the HHG gaseous medium. Our approach of measuring plasma parameters during an HHG process opens the door for better understanding and control over crucial phase-matching parameters that drive generation of coherent XUV beams.
