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Soliton Raman Self-Frequency Shifting of High-Power 1 μm, μJ-Level Femtosecond Pulses at Multi-Megahertz Repetition Rate

Ever shorter, more broadband and higher peak power laser sources at high repetition rates are in strong demand, as they can benefit researches such as nonlinear spectroscopy. The all-bulk spectral broadening approach, arranged for example as a multi-pass cell, has seen rapid development recently. The scheme involves self-phase modulation (SPM) and compression of high-power laser pulses, either emitted from MOPA-type systems [1] or oscillator devices [2]. In contrast to waveguides, the separation of nonlinear and dispersive elements allows extensive control over the net dispersion, making it particularly interesting for the realizing of different nonlinear effects, such as soliton Raman self-frequency shift (SRSFS) effect. In comparison to the symmetric broadening of SPM, SRSFS can generate a power-tunable, asymmetric red-shift [3]. This technique has frequently been applied in optical fibers at a nJ-level of pulse energy. Here we present, to the best of our knowledge, the first implementation of this process to high-energy (>1 μJ) pulses in a Herriott-type multi-pass cell (HC).