Few-Cycle $50\ \upmu\mathrm{J}$ Pulses at $11.2\ \mu\mathrm{m}$ from a Single-Stage OPCPA at 1 kHz

Abstract

An established technique for the study of structural dynamics at atomic time and length scales is ultrafast X-ray diffraction. Laser-driven table-top hard X-ray source at kHz repetition rate brought this technique to a laboratory scale [1]. The X-ray flux can be maximized by using long wavelength few-cycle pulses with energies of several millijoule which was impressively demonstrated with an $5-\mu\mathrm{m}$ optical parametric chirped pulse amplifier (OPCPA) driver at 1 kHz recently [2]. For time resolved investigations an X-ray pump-probe line was added to the system. The setup of our midwave-IR-OPCPA-driven $\text{Cu}-\mathrm{K}\alpha$ X-ray source is shown in Fig. 1(a). A small part of the $5-\mu\mathrm{m}$ driver pulses is currently used as pump for the X-ray pump-probe experiments. For the investigation of other samples of interest pump pulses beyond $10\ \mu\mathrm{m}$ are required. Here we report on the extension of the system by adding a single-stage OPCPA delivering high-energy ultrashort idler pulses at $11.2\ \mu\mathrm{m}$.