Generation of above-terawatt 1.5-cycle visible pulses at 1 kHz by post-compression in a hollow fiber

Rouzee and colleagues at the Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy report on the generation of 6.1 mJ, 3.8 fs pulses by the compression of a kilohertz KMLabs Ti:sapphire laser in a large-aperture long hollow fiber. In order to find optimal conditions for spectral broadening at high pulse energies, different parameter ranges were explored, where ionization or the Kerr effect dominates. After identifying the optimum parameter settings, large spectral broadening at high waveguide transmission was obtained. The intense 1.5-cycle pulses were used for high-harmonic generation in argon and neon where the pulse energy was back calculated to be at least 260 nJ for all harmonics.  The authors also achieved intense XUV radiation, exhibiting continuous spectra in the cut-off region, which is a strong indication that an isolated attosecond pulse is generated.