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Q: Fachverband Quantenoptik und Photonik
Q 44: Laser Technology and Applications
Q 44.4: Vortrag
Donnerstag, 5. März 2026, 11:45–12:00, P 2
Development of dynamic time over threshold method for signal processing in cavity ring-down spectroscopy — Konrad Kleineidam1,2, Hideki Tomita1, Takumi Mochizuki1, Ryohei Terabayashi1, •Erik Thiel2, Klaus Wendt2, Kenji Shimazoe3, Hisashi Abe4, and Norihiko Nishizawa1 — 1Department of Applied Energy, Nagoya University, Japan — 2Institut für Physik, Johannes Gutenberg-Universität Mainz, Germany — 3The University of Tokyo, Japan — 4National Metrology Institute of Japan (NMIJ/AIST), Japan
Cavity ring-down spectroscopy (CRDS) is a highly sensitive technique for detecting elements and isotopes in gas samples by measuring the decay rate (i. e. ring-down rate) of transmitted laser light in a high-finesse optical cavity. Typically, a high-resolution data acquisition system is used to record the time-dependent change in signal and calculate the ring-down decay rate through exponential fitting, in order to measure the molecular number density inside the cavity. By injecting photons of different wavelengths, multiple molecules can be measured simultaneously by recording their respective ring-down rates. This study explores a simplified method for acquiring decay rates using dynamic time over threshold (dToT) analysis. This method relies on the discrete recordings of timing over two dynamically changing threshold voltages instead of the full curve recording by conventional ADCs. Preliminary results suggest that this approach can effectively determine the ring-down decay rate, offering a potentially lower-cost, faster and simpler alternative to the post exponential fitting process in CRDS measurements.
Keywords: laser spectroscopy; cavity ring-down spectroscopy; multiple molecular analysis