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Sensors, Vol. 16, Pages 1544: Intensity-Stabilized Fast-Scanned Direct Absorption Spectroscopy Instrumentation Based on a Distributed Feedback Laser with Detection Sensitivity down to 4 × 10−6

Research paper by Gang Zhao, Wei Tan, Mengyuan Jia, Jiajuan Hou, Weiguang Ma, Lei Dong, Lei Zhang, Xiaoxia Feng, Xuechun Wu, Wangbao Yin, Liantuan Xiao, Ove Axner, Suotang Jia

Indexed on: 25 Sep '16Published on: 21 Sep '16Published in: Sensors (Basel, Switzerland)



Abstract

A novel, intensity-stabilized, fast-scanned, direct absorption spectroscopy (IS-FS-DAS) instrumentation, based on a distributed feedback (DFB) diode laser, is developed. A fiber-coupled polarization rotator and a fiber-coupled polarizer are used to stabilize the intensity of the laser, which significantly reduces its relative intensity noise (RIN). The influence of white noise is reduced by fast scanning over the spectral feature (at 1 kHz), followed by averaging. By combining these two noise-reducing techniques, it is demonstrated that direct absorption spectroscopy (DAS) can be swiftly performed down to a limit of detection (LOD) (1σ) of 4 × 10−6, which opens up a number of new applications.