High-coherence mid-infrared dual-comb spectroscopy spanning 2.6 to 5.2 μm


Mid-infrared dual-comb spectroscopy has the potential to supplant conventional Fourier-transform spectroscopy in applications requiring high resolution, accuracy, signal-to-noise ratio and speed. Until now, mid-infrared dual-comb spectroscopy has been limited to narrow optical bandwidths or low signal-to-noise ratios. Using digital signal processing and broadband frequency conversion in waveguides, we demonstrate a mid-infrared dual-comb spectrometer covering 2.6 to 5.2 µm with comb-tooth resolution, sub-MHz frequency precision and accuracy, and a spectral signal-to-noise ratio as high as 6,500. As a demonstration, we measure the highly structured, broadband cross-section of propane from 2,840 to 3,040 cm−1, the complex phase/amplitude spectra of carbonyl sulfide from 2,000 to 2,100 cm−1, and of a methane, acetylene and ethane mixture from 2,860 to 3,400 cm−1. The combination of broad bandwidth, comb-mode resolution and high brightness will enable accurate mid-infrared spectroscopy in precision laboratory experiments and non-laboratory applications including open-path atmospheric gas sensing, process monitoring and combustion.

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Fig. 1: Octave-spanning mid-infrared dual comb spectrometer.
Fig. 2: Dual-comb spectra.
Fig. 3: Propane spectrum and cross-section.
Fig. 4: Dispersive dual-comb spectrum of gas mixture.
Fig. 5: Measured spectrum of COS.
Fig. 6: Broadband dual-comb spectroscopy with light generated in PPLN waveguides.


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The authors acknowledge funding from the Defense Advanced Research Projects Agency Defense Sciences Office SCOUT program, discussions with F. Cruz regarding the design of the lithium niobate waveguides, and helpful comments from A. Fleisher and E. Waxman.

Author information

The experiments were conceived of by N.R.N., I.C., G.Y. and S.A.D. The mid-infrared systems were built by G.Y., E.B. and D.H. The digital signal processing was implemented by G.Y. and F.R.G. Data analysis was performed by F.R.G. and G.Y. The manuscript was written by G.Y., F.R.G., I.C. and N.R.N.

Correspondence to Gabriel Ycas.

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Ycas, G., Giorgetta, F.R., Baumann, E. et al. High-coherence mid-infrared dual-comb spectroscopy spanning 2.6 to 5.2 μm. Nature Photon 12, 202–208 (2018). https://doi.org/10.1038/s41566-018-0114-7

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