Femtosecond laser system with optical parametric amplifier and wavelength tunability (VIS-MIR)

• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
• Term: Funded in 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 566741331

The femtosecond laser system consisting of a femtosecond laser and a connected optical parametric amplifier with a differential frequency stage will be used to investigate various nonlinear optical frequency conversion processes from the visible to the mid-infrared range. Its wavelength tunability will be used to specifically excite various resonances and to utilize the resulting resonant amplification of the nonlinear processes for analytical purposes or to increase the overall efficiency of frequency generation. The dependence of the dispersion of the nonlinear susceptibility of SiOx, SiNx on their exact chemical composition will be investigated in order to find optimal conditions for their use in nonlinear photonics. In particular, the electric field induced 2nd order nonlinear optical processes in these amorphous materials (e.g. field-induced sum and difference frequency generation) will be further investigated. Based on this, waveguides made of these materials and As2S3 will be produced in order to establish these active optical processes on a photonic chip. The aim is to demonstrate photon pair generation via field-induced spontaneous down-conversion in phase-matched waveguides made of these amorphous materials. By combining them with classical SOI waveguides, a platform for integrated hybrid Si photonics could be created in which both classical 3rd order frequency conversion processes (e.g. four-wave mixing) and 2nd order field-induced processes (sum/difference frequency generation) can take place on the same chip and which will gain importance as a source of photon pairs for experiments in quantum optics and quantum communication. In addition, the femtosecond laser system will be used to elucidate reaction mechanisms on electrode surfaces during electrochemical reactions. For this purpose, an experiment for surface sum frequency generation is established in which an MIR pulse of the femtosecond laser system is tuned to the oscillation frequency of the molecule of interest and hits the electrode surface together with a laser pulse of shorter wavelength. If the molecules are bound to the surface, this results in a resonant amplification of the generated sum frequency signal. In particular the intermediate products of the electrochemical reduction of CO2 to higher-value chemical compounds (such as green fuels) will be investigated using this method. Finally, the laser system will also be used for fast, single-shot material structuring via ablation and the generation of self-organized surface gratings (LIPSS). To this end, a whole series of desired periods are realized in a targeted manner using the wavelength tunability of the femtosecond laser system.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Femtosekundenlasersystem mit optisch parametrischem Verstärker zur Wellenlängenabstimmung (VIS-MIR)
• Instrumentation Group: 5700 Festkörper-Laser
• Applicant Institution: Martin-Luther-Universität Halle-Wittenberg
• Leader: Professor Dr. Jörg Schilling