Compact, spherical mirror-based dense astigmatic-like pattern multipass cell design aided by a genetic algorithm.

Area of Science:

• Optical Engineering
• Gas Sensing Technology
• Spectroscopy

Background:

• Multipass cells (MPCs) are crucial for increasing optical path length in absorption spectroscopy.
• Traditional MPC designs often involve complex mirror arrangements or high costs.
• There is a need for cost-effective and efficient MPC designs for trace gas detection.

Purpose of the Study:

• To propose and demonstrate a novel, cost-efficient design for multipass cells.
• To achieve a high optical path length using a unique configuration of spherical mirrors.
• To validate the performance of the developed MPC for sensitive gas detection.

Main Methods:

• A new MPC design combining tilted spherical mirrors to achieve high optical density.
• Optimization of the cell configuration using a genetic algorithm (GA).
• Development and practical realization of 16 m and 23.8 m optical path length (OPL) MPCs.
• Experimental validation using time-of-flight (TOF) measurements.
• CO2 detection using wavelength modulation spectroscopy (WMS) at 2004 nm.

Main Results:

• Successfully designed and realized MPCs with 16 m and 23.8 m OPL.
• Demonstrated the principle of the novel MPC design through TOF experiments.
• Achieved a limit of detection (LOD) of 0.4 ppmv for CO2.
• Wavelength modulation spectroscopy (WMS) with 10 s averaging enabled sensitive detection.

Conclusions:

• The proposed MPC design offers a cost-efficient approach to achieving long optical path lengths.
• The developed MPC is suitable for high-sensitivity trace gas detection applications.
• This work presents a practical and validated method for enhancing gas sensing capabilities.