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Title:Towards Real-time Processing Of Dual-comb Spectroscopy Data With Quantum Cascade Lasers
Author(s):Gianella, Michele
Contributor(s):Emmenegger, Lukas; Faist, Jérôme; Beck, Mattias; Hillbrand, Johannes; Kapsalidis, Filippos; Jouy, Pierre; Mangold, Markus; Hugi, Andreas; Südmeyer, Thomas; Schilt, Stéphane; Komagata, Kenichi; Nataraj, Akshay; Tuzson, Béla; Vogel, Simon
Subject(s):Instrument/Technique Demonstration
Abstract:Dual-comb spectroscopy (DCS) with quantum cascade lasers (QCL) offers direct access to the mid-infrared region and, thus, to the strong and characteristic ro-vibrational absorption bands of many molecules of interest. In DCS, two frequency comb lasers with unequal repetition frequency produce an array of beat notes which carry the information about magnitude and phase of the optical frequency components that generate them. A large beat note spacing is a requisite if the two sources are free-running, since the beat notes will exhibit a width determined by the (uncorrelated) phase noise of the two lasers. This results in a relatively large acquisition bandwidth, and thus requires a correspondingly large sampling rate. Furthermore, since co-averaging of interferograms in free-running systems is not possible, data processing is computationally intensive, leading to a low duty cycle (time spent acquiring data versus total time) around 1\%. We have developed data processing routines that extract all the relevant spectroscopic information from the measured interferograms in less than the duration of the interferogram itself, paving the way for continuous acquisition with on-the-fly processing (100\% duty cycle). The algorithm can equally handle static measurements, where all the comb line frequencies are constant over time, \emph{step sweep} measurements, where the frequencies of the combs are shifted step-wise, and \emph{rapid sweep} measurements, where the frequencies of the combs are shifted in a continuous and periodic fashion. In the last two approaches, the various offset spectra are interleaved to produce a composite spectrum with smaller point spacing. This algorithm represents an important advance towards high-sensitivity, high-resolution DCS measurements with QCLs, especially when combined with continuous scans and spectral interleaving, which produce large amounts of raw data.
Issue Date:2021-06-22
Publisher:International Symposium on Molecular Spectroscopy
Genre:Conference Paper / Presentation
Date Available in IDEALS:2021-09-24

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