Computational coherent averaging for free-running dual-comb spectroscopy

Abstract

Dual-comb spectroscopy is a rapidly developing technique that enables moving parts-free, simultaneously broadband and high-resolution measurements with microseconds of acquisition time. However, for high sensitivity measurements and extended duration of operation, a coherent averaging procedure is essential. To date, most coherent averaging schemes require additional electro-optical components, which increase system complexity and cost. Instead, we propose an all-computational solution that is compatible with real-time architectures and allows for coherent averaging of spectra generated by free-running systems. The efficacy of the computational correction algorithm is demonstrated using spectra acquired with a THz quantum cascade laser-based dual-comb spectrometer. 2018-05-21

Photon-Driven Broadband Emission and Frequency Comb RF Injection Locking in THz Quantum Cascade Lasers

“…[6][7][8] The THz devices display several interesting features, as the optical resonator based on a double metal provides a cutoff-free waveguide with a weak frequency depended figure of merit, making these devices well suited for ultra-broadband operation and dual comb spectroscopy. [9][10][11] Latest developments in high temperature operation of THz QCLs 12 hold promise also for Peltier cooled operation of fundamental THz combs.…”

Computational Doppler-limited dual-comb spectroscopy with a free-running all-fiber laser

“…The accessible spectral range of our system exceeds 1.7 THz within 200 ms of coherent averaging, corresponding to a record-high number of corrected lines for purely-computational phase correction exceeding 11000 here. We prove the high-resolution spectroscopy capabilities of our system on a NIST standard reference material of low-pressure hydrogen cyanide H 13 C 14 N, which we measure in the 2ν 3 overtone band around 1.56 µm in more than 1 THz bandwidth enabled by leveraging a nontrivial computational phase correction algorithm addressing the previous issues of large computational complexity 35,36 with a potential for DCS-platform-independent character 37 . Finally, our single-cavity DCS system itself has been proven to operate in a dual-comb mode over unprecedentedly long timescale of a dozen of hours.…”

“…Next, we provide an additional phase shift 46 induced by the timing jitter jitter ( ), which is obtained by multiplying the complex resampled interferogram frame y r (t') by exp (i2π c jitter ( ′)), thus yielding y rc (t'). Now all the comb teeth share common frequency fluctuations, as visible in the spectrum of the digital difference frequency (DDFG) signal 37 (see Supplementary Note 7, Supp. Fig.…”

Broadband Time-Resolved Absorption and Dispersion Spectroscopy of Methane and Ethane in a Plasma Using a Mid-Infrared Dual-Comb Spectrometer

“…However, our spectrometer is not capable of time-domain coherent averaging of the interferograms due to the fee running f ceo of the combs, therefore the results are limited to single-shot and low SNR FIDs. It would be interesting to use computational coherent averaging [72,73] and/or digital correction [74] methods, to extend the coherence time of the spectrometer and realize a phase-stable dual-comb spectrometer. This will enable the time-domain averaging of the FID signal of the sample and new ways of dual-comb spectroscopy for plasma diagnostics.…”