Mid-Infrared Cross-Comb Spectroscopy

Abstract

Dual-comb spectroscopy has been proven a powerful tool in molecular characterization, which remains challenging to implement in the mid-infrared region due to difficulties in the realization of two mutually locked comb sources and efficient photodetection. Moreover, the detection capability of dual-comb spectroscopy is fundamentally limited by the strong excitation background and detector saturation. Here we introduce a variant of dual-comb spectroscopy called 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 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 avoid the limits of the background excitation and detector saturation. We experimentally demonstrate a proof-of-concept measurement of atmospheric CO2 around 4.25 $\mu$m, with a 233-$c{m}^{-1}$ instantaneous bandwidth, 28000 comb lines, a single-shot SNR of 167, and a figure of merit of $2.4\times 10^{6}H{z}^{1/2}$. Cross-comb spectroscopy can be realized using up- or down-conversion and offers an adaptable and powerful spectroscopic method outside the well-developed near-IR region. This approach opens new avenues to high-performance molecular sensing with wavelength flexibility, which can impact a wide swath of applications.

arXiv comment12 pages, 5 figures (main text); 34 pages, 14 figures (supplementary materials)

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Cited by in corpus (5)

• Room-temperature waveguide-integrated photodetector using bolometric effect for mid-infrared spectroscopy applications
• Broadband spectroscopy and interferometry with undetected photons at strong parametric amplification
• Room-temperature mid-infrared detection using metasurface-absorber-integrated phononic crystal oscillator
• Mid-infrared temporal ghost imaging via two-photon structured encoding
• Optical-parametric-amplification-enhanced background-free spectroscopy