High sensitivity Faraday rotation spectrometer for hydroxyl radical detection at 2.8 μm
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A distributed feedback diode laser based Faraday rotation spectroscopy (FRS) instrument was developed for detection of hydroxyl free radical (OH) at 2.8 μm. Fast wavelength sweeping method was implemented and the instrument performances were compared with point-by-point wavelength tuning method. The fast sweeping operation mode showed the same short-term minimum detection limit and improved immunity to baseline drift. The effects of strong diamagnetic H2O vapor absorption on FRS detection of paramagnetic OH were investigated. We demonstrated that in the case of strong H2O vapor absorption, the magnitude of the FRS signal for OH might be affected due to changes in the received optical power. The effects of higher laser intensity on the FRS detection sensitivity were also studied experimentally.
KeywordsRadical Detection Magnetic Field Modulation High Extinction Ratio Laser Noise Color Center Laser
This work is supported by the IRENI program of the Région Nord-Pas de Calais, the National Natural Science Foundation of China (41127001), and the Knowledge Innovation Foundation of the Chinese Academy of Sciences (KJCX2-YW-N24). W. Zhao thanks the IRENI program for the postdoctoral support. The support of the Groupement de Recherche International SAMIA between CNRS (France), RFBR (Russia) and CAS (China) is acknowledged. G. Wysocki acknowledges the invited professorship support from the Université du Littoral Côte d’Opale, the US NSF CAREER award CMMI-0954897 and a generous contribution by Lynn and Thomas Ou. The authors thank Leveugle Francis for prompt technical help.
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