Development of a Nitrogen Dioxide Gas Sensor Based on Mid-Infrared Absorption Spectroscopy

Abstract

We demonstrated a mid-IR optical NO₂ monitor based on a frequency-stabilized, Yb-fiber laser pumped difference frequency generation (DFG) in a periodically poled lithium niobate (PPLN) crystal. A high power Yb-fiber laser with a fiber Bragg grating (FBG) and a distributed feedback (DFB) laser diode were used as DFG pump and signal sources, respectively. The spectral characteristics of NO₂ were evaluated using a multipass absorption cell with an optical path length of 10 m. Continuous absorption spectra of NO₂ from 2886.5 cm^-1 (3.464 μm) to 2896.5 cm^-1 (3.452 μm) were demonstrated over 10 cm^-1 with a spectral resolution of approximately 60 MHz. We also demonstrate reproducibility and stability of NO₂ detection system with the mid-IR light sources were investigated, in addition to long-term monitoring of NO₂ concentrations over a three-day period.