Nonlinear pulse compression in solid-core fibers for high-average power few-cycle pulses in the MIR

Summary form only given. High-average-power ultrashort-pulse laser systems in the mid-infrared (MIR) molecular fingerprint region (2-25 μm) are of great interest for environmental applications, defense and fundamental research, in particular for studies of molecular dynamics on the femtosecond scale, chemical reactions and dynamics of photo-excited charge carriers in semiconductors [1-3]. High-sensitivity spectroscopic applications require excellent laser stability as well as high average powers enabling a high dynamic range and good signal to noise ratio. In addition, few-cycle pulse duration and the control over the carrier envelope phase (CEP) opens the possibility for MIR dual-comb spectroscopy, which allows for significantly shorter measurement times and improved stability [3]. Emitting at around 2 μm wavelength, high-power ultrafast Thulium-based fiber lasers are an ideal frontend for optical parametric frequency down-conversion towards the MIR. Few-cycle pulse durations can be readily achieved at 2 μm wavelength with nonlinear self-compression in solid-core glass-fibers [4], which is an average power-scalable approach providing diffraction-limited output and good pulse quality even for large compression factors. This work comprises the experimental demonstration as well as the discussion of design rules of the nonlinear compression stage for optimum pulse quality, short pulse duration and high stability of the compressed laser output. We report on a laser source with excellent long-term stability delivering pulses with sub-25 fs duration, 0.7 μJ pulse energy and 50 MHz pulse repetition rate, representing an ideal source for MIR generation