Highly efficient nonlinear spectral broadening of mJ pulses at 2µm wavelength in a gas multipass cell and compression sub-30 fs (Conference Presentation)

Abstract

Within this work we demonstrate the efficient nonlinear temporal compression of mJ pulses emitted by an ultrafast thulium-doped fiber laser system. For spectral broadening, a krypton and helium filled Herriott-type multi-pass cell with broadband dielectric mirrors is employed. The input pulses with 1,78 mJ and 85 fs are spectrally broadened and subsequently compressed utilizing fused silica plates revealing a pulse duration below 29 fs while featuring an overall transmission of 91%. In addition to the preservation of the input beam quality, the system exhibits a shot-to-shot noise ratio of less than 1.2% as well as an excellent long-term power stability with fluctuations below 1% over a time span of 2 hours. The presented results demonstrate the advantageous properties of the multi-pass cell approach: High efficiency and high transversal beam quality at high average power, not only for conventional ultrafast ytterbium-based laser systems at 1 µm wavelength, but also in the mid-infrared regime. We believe that this system, delivering an average power above 162 W and sub-5-cycle pulse duration, provides a promising working point for following secondary source experiments like THz- or high harmonic generation.