Mid-infrared laser absorption spectrometers based upon all-diode laser difference frequency generation and a room temperature quantum cascade laser for the detection of CO, N2O and NO

Stability of widely tuneable, continuous wave external-cavity quantum cascade laser for absorption spectroscopy

“…6a cal power was about 15 W. NO measurements by means of the FTIR spectrometer connected directly to the output of the plasma reactor were slightly higher at high oxygen concentrations and this was explained by further oxidation reactions of NO in the 2.4 m long tube used to connect the FTIR multipass cell with the optical cell of the EC-QCL spectrometer. A NO LOD of 2 ppm in a 7 s single scan of 1892.4-1914.5 cm À1 is comparable to the LOD of 9 ppm achieved with single-frequency DFB QCL and averaging of 100 scans (1899.5-1901 cm À1 ) within 0.1 s at atmospheric pressure in a 21 cm long optical cell [21]. It is worth noting that the NO LOD demonstrated here with a path length of 41 cm is markedly higher than the NO LOD of 0.7 ppbv (1 s observation time) and 1 ppbv (3 s averaging time) achieved by use of longer optical path lengths and a cw DFB QCL with a cavity-enhanced technique (highfinesse cavity with an effective path length of 700 m) [28] and wavelength modulation spectroscopy (a 76 m long multiple-pass optical cell) [30], respectively.…”

“…These had an approximate spacing of $0.016 cm À1 . This effect was not observed in a fit to the same absorption line under similar experimental conditions around 1900 cm À1 using a tuneable single-frequency cw DFB QCL [21,22]. It is thought that these variations in the fit residual observed with the cw EC-QCL could arise from the transient frequency jitter during wavelength tuning over the absorption lines.…”

Mid- infrared semiconductor laser based trace gas sensor technologies for environmental monitoring and industrial process control

“…Quantitative measurements of CO in the ν 1 fundamental rotational-vibrational band were reported previously by several research groups [12,[15][16][17]. In Ref.…”

A Hyphenated Preconcentrator-Infrared-Hollow-Waveguide Sensor System for N2O Sensing

“…Among the optical sensors, the mid-infrared spectral region (MIR; 2.5–25 μm) has been widely utilized for N 2 O detection 11 , 16 , 17 utilizing IR-absorption phenomena 18 . To achieve the desired sensitivity, usually multi-pass gas cell providing extended absorption path lengths are applied.…”