A swept-source dual-comb spectrometer on a chip
Abstract
Dual-comb spectroscopy (DCS) enables high-speed, high-resolution spectroscopy by down-converting optical spectra to the radio-frequency (RF) domain through the interference of two mutually detuned frequency combs. Accurately resolving narrow molecular absorption features requires closely spaced comb lines generated by large laser cavities with long round-trip times, thereby hindering the miniaturization of high-resolution spectrometers. Here, we circumvent this limitation by demonstrating a swept-source dual-comb spectrometer using two unidirectional racetrack semiconductor lasers integrated on the same chip. The traveling-wave frequency combs are generated by strong RF injection at the laser cavity round-trip frequency of 14.3~GHz---otherwise known as quantum walk combs---and are continuously tuned in frequency by varying the laser drive currents. This enables continuous spectral sampling over a 32~cm−1 range centered near 8~\textmu m, with an effective sampling interval of approximately 80~MHz. The outputs of both combs are coupled into the same monolithically integrated light coupler, providing automatic collinear alignment before the combined beam interrogates the sample. We benchmark the spectrometer against an external-cavity tunable laser and validate its performance using HITRAN simulations for 1.25\% nitrous oxide. Finally, the unidirectional comb architecture suppresses the detrimental effects of optical feedback, yielding comparable residuals even under deliberately introduced strong feedback. More broadly, the benefits of miniaturization extend beyond reduced footprint: chip-scale integration enables new forms of electrical and optical control that can fundamentally change how dual-comb spectrometers are operated.
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BibTeX
@misc{fuchsberger2026sweptsource,
title = {{A swept-source dual-comb spectrometer on a chip}},
author = {Johannes Fuchsberger and Theodore P. Letsou and Paul Chevalier and Marcus Ossiander and Dmitry Kazakov and Federico Capasso and Benedikt Schwarz},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2608.22827},
eprint = {2608.22827},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2608.22827},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - A swept-source dual-comb spectrometer on a chip
AU - Johannes Fuchsberger
AU - Theodore P. Letsou
AU - Paul Chevalier
AU - Marcus Ossiander
AU - Dmitry Kazakov
AU - Federico Capasso
AU - Benedikt Schwarz
PY - 2026
DA - 2026/10/27
PB - arXiv
DO - 10.48550/arxiv.2608.22827
UR - https://arxiv.org/abs/2608.22827
AB - Dual-comb spectroscopy (DCS) enables high-speed, high-resolution spectroscopy by down-converting optical spectra to the radio-frequency (RF) domain through the interference of two mutually detuned frequency combs. Accurately resolving narrow molecular absorption features requires closely spaced comb lines generated by large laser cavities with long round-trip times, thereby hindering the miniaturization of high-resolution spectrometers. Here, we circumvent this limitation by demonstrating a swept-source dual-comb spectrometer using two unidirectional racetrack semiconductor lasers integrated on the same chip. The traveling-wave frequency combs are generated by strong RF injection at the laser cavity round-trip frequency of 14.3~GHz---otherwise known as quantum walk combs---and are continuously tuned in frequency by varying the laser drive currents. This enables continuous spectral sampling over a 32~cm^−1 range centered near 8~\textmu m, with an effective sampling interval of approximately 80~MHz. The outputs of both combs are coupled into the same monolithically integrated light coupler, providing automatic collinear alignment before the combined beam interrogates the sample. We benchmark the spectrometer against an external-cavity tunable laser and validate its performance using HITRAN simulations for 1.25\% nitrous oxide. Finally, the unidirectional comb architecture suppresses the detrimental effects of optical feedback, yielding comparable residuals even under deliberately introduced strong feedback. More broadly, the benefits of miniaturization extend beyond reduced footprint: chip-scale integration enables new forms of electrical and optical control that can fundamentally change how dual-comb spectrometers are operated.
ER -