Dual-comb spectroscopy has been proven beneficial in molecular characterization but remains challenging in the mid-infrared region due to difficulties in sources and efficient photodetection. Here we introduce cross-comb spectroscopy, in which a mid-infrared comb is upconverted via sum-frequency generation with a near-infrared comb of a shifted repetition rate and then interfered with a spectral extension of the near-infrared comb. We measure CO absorption around 4.25�����m with a 1-��m photodetector, exhibiting a 233-cm instantaneous bandwidth, 28000 comb lines, a single-shot signal-to-noise ratio of 167 and a figure of merit of 2.4 �� 10 Hz. We show that cross-comb spectroscopy can have superior signal-to-noise ratio, sensitivity, dynamic range, and detection efficiency compared to other dual-comb-based methods and mitigate the limits of the excitation background and detector saturation. This approach offers an adaptable and powerful spectroscopic method outside the well-developed near-IR region and opens new avenues to high-performance frequency-comb-based sensing with wavelength flexibility.
References
Opt Lett. 2014 Apr 15;39(8):2435-8
[PMID: 24979012]
Science. 2015 Oct 23;350(6259):420-3
[PMID: 26429882]
Opt Lett. 2010 May 1;35(9):1395-7
[PMID: 20436581]
Proc Natl Acad Sci U S A. 2019 Feb 26;116(9):3454-3459
[PMID: 30755528]
Opt Express. 2018 Jun 25;26(13):16813-16823
[PMID: 30119502]
Grants
FA9550-20-1-0040/United States Department of Defense | United States Air Force | AFMC | Air Force Office of Scientific Research (AF Office of Scientific Research)
