Compact laser spectroscopy-based sensor using a transformer-based model for analysis of multiple molecules

Interest in the development of compact sensors that consume low energy is increasing day by day. This study reports, to our knowledge, such a novel sensor system that can analyze multiple molecules simultaneously with high sensitivity under ambient conditions (900 mbar and 300 K). To quantify molecules, a distributed feedback quantum cascade laser (DFB QCL) was combined with a compact multi-pass absorption (mpass) cell without the need for vacuum components, lock-in amplifier, or any electric filters. By using a transformer-encoder-based model, the noise level was reduced and the pressure-broadened absorption lines of the molecules were separated, narrowed (resolved), and displayed one by one. In this way, molecules can be quantified using pressure-broadened overlapping absorption lines under ambient conditions. To test our sensor system, CO 2 and N 2 O molecules were used. Depending on the concentration values, SNR can be improved by up to 50 times. Better results are obtained at higher concentration values. Detection limits for N 2 O and CO 2 molecules were determined to be 30 ppb and 180 ppm, respectively. The analysis time of molecules is around 80 ms.