GW-Scale Pulse Compression at Multi-MHz-Rate via All-Bulk Quasi-Waveguide Spectral Broadening

The recent advent of coherent precision spectroscopy techniques has intensified the need for broadband, waveform-controlled radiation with high brilliance in the mid-infrared (IR) spectral range [1]. Such radiation is conventionally generated via parametric down-conversion processes. To boost the intrinsically low conversion efficiencies in the ultra-thin nonlinear media—required for maintaining a broad spectral coverage—it is of vital importance to develope driving sources providing high-power few-cycle laser pulses at MHz repetition rates and with excellent spatial and temporal properties in the near-IR. To date, such pulses can efficiently be generated by thin-disk oscillators with extra-cavity pulse compression, e.g. in Herriott-type multi-pass cells (MPCs). However, the achievable pulse durations in all-bulk-based systems have so far been restricted to > 15 fs, mostly due to the limited flexibility in controlling MPC dispersion and nonlinearity. Here we present a new approach for few-cycle pulse-compression that preserves the homogenization benefits of the quasi -waveguide nature of Herriott-cells but allows a tailoring of the nonlinearity and dispersion—achieved by distributing and modularizing each pass [2].