Portable ppb-level carbon dioxide sensor based on flexible hollow waveguide cell and mid-infrared spectroscopy

We demonstrated a mid-infrared (mid-IR) gas sensor based on a hollow waveguide (HWG) cell, which was fabricated with a flexible polycarbonate (PC) base tube. The HWG inner-coated with silver and silver iodide films achieves a low loss property at 4.26 mu m wavelength of carbon dioxide fingerprint absorption. The source and detector of the sensor were broad-spectrum light source and pyroelectric detector with Fabry-Pe ' rot (FP) filter. The HWG cell is butt-coupled with the light source and detector. No other optical elements are required to ensure the stability of the sensor. The performance of the sensor with HWGs at various lengths and inner diameters was tested and optimized. The sensor with a coiled HWG cell has a limit of detection (LOD) as low as 263 ppb. This scheme provided a simple, miniaturized, and cost-effective solution for trace gas sensing.

Automated summary

We have demonstrated a mid-infrared gas sensor based on a hollow waveguide cell. The waveguide inner-coated with silver and silver iodide films achieves low loss at 4.26 μm wavelength. The sensor uses a broad-spectrum light source and a pyroelectric detector, and the waveguide cell is butt-coupled with them. Various lengths and inner diameters of waveguide cells have been tested and optimized, with a coiled waveguide cell achieving a low detection limit of 263 ppb. This provides a simple, miniaturized, and cost-effective solution for trace gas sensing.