Two-Color Mid-IR Optical Parametric Amplifier for Attosecond Pulse Generation

The production of isolated attosecond pulses is nowadays based on the generation of high harmonics driven by ultrafast and intense laser sources in gases. The generation of such pulses requires the confinement of the harmonic emission within a single event, thus obtaining a continuous XUV spectrum. Here we report on the generation of continuous XUV spectra produced by an ultra-broadband optical parametric amplifier operating in the mid-IR and generating multi-cycle pulses, thus avoiding the use of few-cycle Ti:sapphire lasers and, thanks to the favorable cutoff scaling law for mid-IR drivers, paving the way to the production of isolated attosecond pulses well above the 100-eV photon energy.