Ultra-high-precision mid-IR spectrometer II: system description and spectroscopic performance |
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Authors: | P. Weibring D. Richter A. Fried J.G. Walega C. Dyroff |
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Affiliation: | 1. Earth Observing Laboratory, National Center for Atmospheric Research, 3450 Mitchell Lane, Boulder, CO, 80301, USA
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Abstract: | The development and spectroscopic performance evaluation of an ultra-sensitive, mid-IR spectrometer is reported. The laser system is based upon difference-frequency generation (DFG) at ~3.5 μm by mixing a DFB diode laser at 1562 nm and a DFB fiber laser at 1083 nm using a periodically poled LiNbO3 crystal. DFG radiation was coupled to a 100?m optical path length astigmatic Herriott cell. Sensitive and selective spectroscopic detection of formaldehyde was performed with second-harmonic detection using Peltier-cooled HgCdTe detectors. By applying computer lock-ins, dual-beam optical noise subtraction, focus matching, thermal stabilization, active wavelength control, and advanced signal processing a sensitivity corresponding to an absorbance ~1.6×10-7 is achieved for 260 s of averaging. |
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