Mainz 2026 – wissenschaftliches Programm

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MO: Fachverband Molekülphysik

MO 30: Poster – Molecular Spectroscopy

MO 30.11: Poster

Donnerstag, 5. März 2026, 17:00–19:00, Philo 1. OG

Development of an ns-OPO/OPA Mid-Infrared Source for Molecule Detection by THG Spectroscopy — •Noah Dornhecker and Thomas Halfmann — TU Darmstadt Institut für Angewandte Physik, Darmstadt, Germany

We report on progress towards a nanosecond mid-infrared laser source based on a compact, all-solid-state OPO-OPA architecture, developed to provide narrowband, tunable mid-infrared (MIR) pulses and pulse energies at the mJ level, e.g., for nonlinear spectroscopy of molecular samples. In particular, we aim at a wavelength of 4.3 µm for the detection of CO₂ via resonantly enhanced THG spectroscopy. The system employs an injection-seeded, frequency-doubled Nd:YAG pump at 532 nm to drive an OPO stage, generating a signal wave at 853 nm and an idler wave at 1412 nm. The latter seeds an OPA stage, pumped by the fundamental wave at 1064 nm of the Nd:YAG laser, allowing efficient difference-frequency generation towards the MIR. Initial results demonstrate stable operation of the OPO stage with idler pulse energies above 190 µJ, distinctly narrowed spectra under injection seeding, and spatial beam profiles close to Gaussian. As first results from the OPA stage, we meanwhile achieved output pulse energies of 13 µJ at a wavelength of 4.3 µm, which are subject now to further improvement. From simulations, we confirmed that with a seed pulse energy of 190 µJ, we can reach the mJ regime from the OPA stage. These characteristics provide a robust seed for high-gain MIR amplification targeting mJ-level pulse energies. We demonstrate the applicability of the system for molecule detection via nonlinear spectroscopy.

Keywords: MIR; Laser System; CO2; ns-OPO