2 August 2010 Spectroscopy with a coherent dual frequency comb interferometer at 3.4 μm
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A coherent dual fiber-comb spectrometer centered at 1.5 μm wavelengths is transferred to 3.4 μm by differencefrequency generation with a 1064 nm cw laser. It is shown that the residual linewidth between the comb teeth at 3.4 μm is resolution-limited to 200 mHz; such narrow linewidths can enable coherent dual-comb spectroscopy at high-precision and signal-to-noise ratio. We then discuss different interferometric configurations for coherent dual-comb spectroscopy. We find that a two-branch interferometric setup is appropriate to measure both the magnitude and phase spectrum of purely Doppler-broadened absorption lines. An initial measurement of methane lines in the υ3 band P-branch with a resolution of 114 MHz is demonstrated.
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Esther Baumann, Fabrizio R. Giorgetta, Ian Coddington, William C. Swann, Nathan R. Newbury, "Spectroscopy with a coherent dual frequency comb interferometer at 3.4 μm", Proc. SPIE 7790, Interferometry XV: Techniques and Analysis, 77900X (2 August 2010); doi: 10.1117/12.859730; https://doi.org/10.1117/12.859730

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