High-Energy Pulse Compression in the Mid-Wave Infrared

Currently much effort is invested in the development of ultrafast, high-energy, high-power solid-state lasers in the near- and midwave-infrared (mid-IR) spectral range. Thanks to the thin-disk and slab technologies neodymium and ytterbium-based systems emitting at ~1 µm became the main workhorse in numerous laboratories. Meanwhile, thulium and holmium-doped systems emitting around 2 µm wavelength also deliver ultrashort multi-mJ pulses at tens of watts average power [1] , [2] . However, scaling of the pulse energy in amplified systems to the multi-mJ level is accompanied by spectral gain narrowing and hence an increase of the transform-limited pulse duration. In fact, the pulse duration of amplified 2 µm systems with pulse energy larger than 10 mJ, so far only Ho-based, is well beyond a picosecond [1] , [2] . This is optimal for pumping mid-IR OPCPAs [3] but much too long for many other applications. Thanks to the recent developments of post compression techniques [4] , especially those of stretched flexible hollow fibers (SF-HCF) and multi-pass cells the compression of high-energy ps pulses has become feasible. Here we present the compression of few-ps pulses at 2.05 µm wavelength with >40 mJ energy to a sub-100 fs duration using a combination of pre-compression in air and subsequent compression in a noble gas-filled hollow core fiber.