A wide-range temperature sensor with simultaneous NO concentration measurement using three-line laser absorption spectroscopy at 5.3 μm

A three-line tunable diode laser absorption spectroscopy (TDLAS) temperature sensor was developed for simultaneous measurement of temperature and nitric oxide (NO) concentration over the range 1000–3500 K. The sensor employs a single mid‑infrared interband cascade laser (ICL) targeting fundamental‑band NO absorption lines near 5.3 μm. The performance of the proposed sensor was systematically validated in a shock tube through time-resolved, continuous measurements under transient high-temperature conditions. To improve diagnostic accuracy at elevated temperatures, dedicated shock-tube experiments were further conducted to calibrate temperature-dependent spectroscopic parameters, including line strengths and NO–Ar collisional broadening coefficients over wide temperature ranges. Across 1000–3500 K, temperature deviations remained below 2%, while relative errors in NO concentration were within 5%. At conditions around 3200 K, the sensor captured the thermal dissociation of NO behind the shock, and the measured NO evolution was compared with calculations based on the Glarborg mechanism. The proposed sensor is non‑intrusive, fast‑responding, and compact, and is suitable for in‑situ, wide‑temperature‑range NO diagnostics in both reactive and non‑reactive high‑temperature flow fields.