Two-color Laser apparatus for ultrafast imaging and spectroscopy (LAPIS)

• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 576719161

We are applying for a pump-probe two-color laser apparatus to advance the frontiers of ultrafast photoelectron and photon imaging. The proposed setup is designed to combine ultrashort (few-femtosecond) laser pulses in the ultraviolet (UV), vacuum-ultraviolet (VUV), and extreme-ultraviolet (XUV) spectral ranges with synchronized infrared (IR) pulses. The core concept is to initiate a light–matter interaction using the UV–XUV pulses and subsequently modulate or perturb this interaction with an ultrashort IR field. This two-color pump-probe scheme offers several key advantages: i) Enhanced nonlinear optical effects in the target, such as increased high-harmonic generation [6,7]; ii) Access to new regimes of photoelectron imaging, including two-color laser-induced electron diffraction ([4]); iii) Advanced material characterization with high spatial and temporal resolution across a broad spectral range, e.g., investigating optics degradation under few-femtosecond UV exposure; iv) Exploration of novel metaoptical elements, such as XUV metalenses and waveplates. Specifically, a driving ytterbium (Yb) laser with tunable repetition rate and pulse energy seeds a pump-probe interferometric setup. One arm of the interferometer includes a two-stage compressor and two modules for the generation of high-order harmonics or UV pulses in gas [8]. The second arm contains an optical parametric amplifier (OPA) to generate IR pulses with wavelengths up to 4 μm, along with a multipass cell compressor for pulse compression. The imaging and spectroscopy experiments are conducted at a specially designed interaction point, where the VUV/XUV and IR pulses are recombined and synchronized. At the interaction point, dedicated instruments are used to detect the experimental observables, including: a VUV/XUV spectrometer, an XUV CCD camera, a velocity map imaging (VMI) spectrometer. A large part of the setup is housed in vacuum chambers, a necessary requirement for the propagation and use of VUV/XUV radiation. The system is intended for experiments primarily in the following four research areas: 1. Novel methods to generate vacuum ultraviolet (VUV) and extreme ultraviolet light (XUV). Examples: New regimes of two-color driven high-harmonic generation. 2. Ultrafast molecular and condensed-phase imaging and spectroscopy. Examples: two-color laser-induced electron diffraction and two-color high-harmonic generation. Generation of secondary x-ray light for coherent/incoherent diffraction imaging. 3. VUV/XUV metaoptics. Examples: Diffraction-limited imaging at extreme ultraviolet photon energies. Advanced polarisation control of XUV light for spectroscopy of chiral molecules or spin dynamics in materials. 4. Material characterisation. Examples: investigation of degradation of XUV-optics. Full-bandwidth characterisation of fluoride-based UV optical coatings. Investigation of low-roughness diamond membranes.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Zwei-Farben Lasersystem für ultraschnelle Bildgebung und Spektroskopie (LAPIS)
• Instrumentation Group: 5720 Farbstoff-Laser
• Applicant Institution: Gottfried Wilhelm Leibniz Universität Hannover
• Leader: Professor Dr. Andrea Trabattoni