The Pump-Probe Laser at the Small Quantum Systems (SQS) Instrument at European XFEL.

The Pump-Probe Laser (PPL) at the SQS experimental instrument is used to initiate chemical reactions and other ultrafast processes that are to be probed with the X-ray Free- Electron Laser (FEL). The main laser source is maintained and delivered by the LAS team and provides ultrashort pulses of optical light of either 15-50 fs with a center wavelength of 800 nm or alternatively around 800 fs centered at 1030 nm (which can be compressed to ~50 fs following spectral broadening in a Heriot Multi-Pass Cell (HMPC)). With suitable feedbacks, the typical jitter between the PPL and the FEL is sub-10 fs. These fundamental wavelengths can be converted to Harmonics as well as down-converted light from an Optical Parametric (Chirped-Pulse) Amplifiers, to act as additional triggers for X-ray-probe experiments. More recently, intense infra-red (IR) fields have been utilized for angular-streaking experiments that allow for measuring and quantifying the duration of attosecond X-ray pulses from the FEL Future installations will also include gas-filled Hollow-Core Fiber (HCF) set-ups to allow for sub-10 fs pulses synchronized to the FEL to be produced, as well as a tunable UV source.