We report a method for the simultaneous measurement of carbon dioxide (CO2) and carbon monoxide (CO) absolute concentrations and temperature using fiber laser intracavity absorption spectroscopy (FLICAS). FLICAS uses an erbium-doped broadband laser capable of being tuned in the range 6350-6450 cm-1. The range 6390-6410 cm-1, which is emitted by the laser without tuning, allows for simultaneous observation of the CO, CO2, and methane (CH4) spectra. Truly simultaneous observation of these spectra is possible during one laser pulse with duration as short as 3.7 μs. The sensitivity of the CO measurement is about 20 times higher than that of CO2, a feature which is advantageous for several applications. The concentration of CO can be measured with a sensitivity of 400 ppm at room temperature, and this sensitivity can be improved by increasing the generation time. The experiments were performed in a temperature and flow-controlled cell in order to evaluate the accuracy of the concentration and temperature measurements from 296 to 1200 K. The measured spectra of CO and CO2 are well described by the HITRAN database, allowing for accurate and simultaneous determination of CO, CO2 and temperature. The temperature is evaluated using the CO2 spectrum, which includes many "hot" transitions. The CH4 HITRAN data are deficient at high temperatures, so this method only allows for the evaluation of methane concentrations at room temperature.
Bibliographical noteFunding Information:
The authors are grateful to V. Baev for providing fiber optics and very fruitful discussions. This work was supported in part by the Israel Science Foundation (Grant No. 1149/12 ), Israel Ministry of Energy and Water Resources (Grant No. 211-11-007/2011-7-10 ), and the Research Authority of The Open University of Israel (Grant No. 47324 ).
- Fiber laser intracavity absorption
- Temperature sensor