Plasma Window for intense few-cycle pulse generation and HHG

The generation and application of optical few-cycle pulses and coherent x-ray pulses are two of the most prominent technologies at the heart of strong-field physics, for which vacuum conditions and separate pressure-controlled gas media are generally required. In practice, the traditional solid window materials used for x-ray beamlines may introduce undesirable high attenuation, are subject to failure under high heat loads and, most importantly, for high laser intensities introduce strong spatio-temporal distortions to few-cycle pulses, which are prohibitive to any experimental scheme involving the transport of an intense few-cycle pulse from high to low pressure and vice verse. Plasma windows, an original concept developed by Ady Hershcovitch from Brookhaven National Laboratory for non-vacuum electron welding applications, are a promising alternative for the separation of the experimental vacuum environment from pressure-controlled gas media used for the generation of optical few-cycle pulses as well as coherent x-ray pulses. In this research project, the applicant Dr. Pu Zou together with the group of Prof. Andrius Baltuška at the Photonics Institute of the Vienna University of Technology (PI-VUT) propose to experimentally demonstrate the application of the "plasma window" for intense few-cycle pulse generation and coherent xuv emission. A Ti: Sa based laser amplifier delivering 30-fs pulses with ?2-mJ-@-3kHz at PI-VUT will be dedicated to this project. The basic design element of the "plasma window" is segmented wall-stabilized cascaded arc plasma, which could be used as a "dispersion-free" interface between the different pressure regions, since it exhibits a high viscosity to gas flow, resulting in the formation of a "plug" that can support a significant pressure difference. Such cascaded arcs have been constructed and extensively studied by the group of M.C.M. van de Sanden at Eindhoven University of Technology, from whom we will borrow an arc for this project. We will also work with Ady Hershcovitch, who will support the project with valuable advice and his experience from his applications of the plasma window in many fields. We plan to demonstrate the enabling nature of the plasma window for strong-field physics by using it to optimize out-coupling of an intense optical few-cycle pulse from a self-compressed filament in gases, showing high energy throughput and great simplicity as no down-stream post-compression step is required. In the same long interaction cell, these few-cycle pulses will drive high harmonic generation and theoretically predicted intensity spikes should even lead to the generation of isolated attosecond pulses in the filament. We plan to couple these from the interaction cell to a vacuum chamber using the plasma-window, thus demonstrating an astonishingly simple scheme for isolated-attosecond-pulse generation.