Postcompression of high-energy terawatt-level femtosecond pulses and application to high-order harmonic generation

Abstract

We perform a postcompression of high-energy pulses by using optical-field ionization of low pressure helium gas in a guided geometry. We apply this approach to a terawatt (TW) chirped-pulse-amplification-based Ti:sapphire laser chain and show that spectral broadening can be controlled with both the input pulse energy and gas pressure. Under optimized conditions, we generate 10 fs pulses at the TW level directly under vacuum and demonstrate a high stability of the postcompressed pulse duration. These high-energy postcompressed pulses are thereafter used to perform high harmonic generation in a loose focusing geometry. The extreme ultraviolet (XUV) beam is characterized both spatially and spectrally on a single shot basis, and structured continuous XUV spectra are observed.