High sensitivity Faraday rotation spectrometer for hydroxyl radical detection at 2.8 μm
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- Zhao, W., Wysocki, G., Chen, W. et al. Appl. Phys. B (2012) 109: 511. doi:10.1007/s00340-012-5089-3
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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.