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Two semiconductor optical frequency combs, consuming less than 1 W of electrical power, are used to demonstrate high-sensitivity mid-infrared dual-comb spectroscopy in the important 3-4 μm spectral region. The devices are 4 mm long by 4 μm wide, and each emits 8 mW of average optical power. The spectroscopic sensing performance is demonstrated by measurements of methane and hydrogen chloride with optical multi-pass cell sensitivity enhancement. The system provides a spectral coverage of 33 cm (1 THz), 0.32 cm (9.7 GHz) frequency sampling interval, and peak signal-to-noise ratio of ∼100 at 100 μs integration time. The monolithic design, low drive power, and direct generation of mid-infrared radiation are highly attractive for portable broadband spectroscopic instrumentation in future terrestrial and space applications.
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http://dx.doi.org/10.1364/OL.44.002113 | DOI Listing |
APL Photonics
October 2024
Department of Electrical, Computer and Energy Engineering, University of Colorado at Boulder, Boulder, Colorado 80309, USA.
Mid-infrared microscopy is an important tool for biological analyses, allowing a direct probe of molecular bonds in their low energy landscape. In addition to the label-free extraction of spectroscopic information, the application of broadband sources can provide a third dimension of chemical specificity. However, to enable widespread deployment, mid-infrared microscopy platforms need to be compact and robust while offering high speed, broad bandwidth, and high signal-to-noise ratio.
View Article and Find Full Text PDFAn approach is described for spectrally parallel hyperspectral mid-infrared imaging with spatial resolution dictated by fluorescence imaging. Quantum cascade laser (QCL)-based dual-comb mid-infrared spectroscopy enables the acquisition of infrared spectra at high speed (<1 millisecond) through the generation of optical beat patterns and radio-frequency detection. The high-speed nature of the spectral acquisition is shown to support spectral mapping in microscopy measurements.
View Article and Find Full Text PDFPhys Chem Chem Phys
July 2025
Institute of Atomic and Molecular Sciences Academia Sinica, Taipei 106319, Taiwan.
The hydroperoxy radical (HO), a key species in atmospheric chemistry, necessitates accurate quantitative measurements and precise spectroscopic characterization, both of which are essential for laboratory investigations and field observations. Herein, we present precision measurements of the absolute line strengths of the HO radical in the ν and ν vibrational bands by utilizing synchronized two-color time-resolved dual-comb spectroscopy in the mid-infrared region. By simultaneously measuring the byproduct HCl near 3.
View Article and Find Full Text PDFWe present the design and implementation of a free-space broadband mid-infrared optical circulator, particularly suitable for applications involving quantum cascade laser (QCL) frequency combs (FCs). The circulator is based on a phase-retarding mirror (PRM) and achieves an isolation level of 29.7 dB with a single-mode QCL and 25.
View Article and Find Full Text PDFMid-infrared dual-comb spectroscopy offers significant advantages by combining the high sensitivity of mid-infrared spectroscopy with the high spectral resolution and rapid acquisition of the dual-comb method. However, its effective resolution, constrained by the inherent comb line spacing, hinders its ability to resolve narrow absorption features, common in critical applications such as sub-Doppler spectroscopy, low-pressure gas analysis, and construction of the atmospheric profile. To address this challenge, we present a synchronous offset frequency tuning method for the mid-infrared dual-comb system to improve effective resolution far beyond comb line spacing.
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