A near-infrared broadband cavity-enhanced
sensor system was demonstrated
for the first time using an energy-efficient light emitting diode
(LED) with a central emission wavelength at 1650 nm and a light power
of ∼16 mW. A portable absorption gas cell was designed for
realizing a compact and stable optical system for easy alignment.
An ultrashort 8-cm-long cavity was fabricated consisting of two mirrors
with a ∼99.35% reflectivity. Methane (CH4) measurement
was performed employing two detection schemes, i.e., NIRQuest InGaAs
spectrometer and scanning monochromator combined with phase-sensitive
detection. Retrieval of CH4 concentration was performed
using a least-squares fitting algorithm. Sensitivities (i.e., minimum
detectable absorption coefficient) were achieved of 1.25 × 10–6 cm–1 for an averaging time of 45
s using the NIRQuest InGaAs spectrometer and 1.85 × 10–6 cm–1 for an averaging time of 8 min using the
scanning spectrometer in combination with lock-in detection. Field
monitoring of CH4 gas leakage was performed using the NIRQuest
spectrometer. Multigas sensing of CH4 and acetylene (C2H2) was carried out simultaneously using the high-resolution
scanning spectrometer. A linear response of the retrieved concentration
level versus nominal value was observed with a large dynamic range,
demonstrating the reliability of the compact LED-based near-infrared
broadband cavity-enhanced absorption spectroscopy (NIR-IBBCEAS) for
multigas sensing applications.
A near-infrared C2H2/CH4 sensor was demonstrated utilizing a miniaturized high finesse cavity with high sensitivity and remarkable dynamic measurement performance.
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