Accurate frequency referencing for fieldable dual-comb spectroscopy

Truong, Gar-Wing; Waxman, E.; Cossel, Kevin C.; Baumann, Esther; Klose, A.; Giorgetta, Fabrizio R.; Swann, William C.; Newbury, Nathan R.; Coddington, Ian

doi:10.1364/oe.24.030495

Cited by 95 publications

(65 citation statements)

References 35 publications

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“…A compact, mobile DCS system such as this one has no moving parts, dense point spacing (200 MHz or 0.0067 cm −1 in this work), effectively no instrument line shape, and a calibration-free wavelength axis as described in Rieker et al (2014) and Truong et al (2016). As a result, it oversamples the 5 GHz wide (0.15 cm −1 ) pressure-broadened gas lines of carbon dioxide, methane, water, and other small molecules without distortion, which should suppress any instrument-specific systematics and allow comparison of DCS data between instruments and over time.…”

Section: Dual-comb Spectroscopymentioning

confidence: 99%

“…Mutual optical coherence between the combs is enforced by phase-locking an optical tooth of each to a common continuous-wave (cw) laser and the carrierenvelope offset frequency of each to a common quartz microwave oscillator. Absolute frequency accuracy is then enforced by a bootstrapped approach that effectively locks the common cw laser to the same quartz microwave oscillator (Truong et al, 2016). The result is sub-hertz mutual coherence, ∼ 120 kHz (4 × 10 −6 cm −1 ) absolute line widths, and 1.1 MHz (3.6 × 10 −5 cm −1 ) absolute frequency accuracy (Truong et al, 2016).…”

Section: Overview Of Experimentsmentioning

confidence: 99%

“…Absolute frequency accuracy is then enforced by a bootstrapped approach that effectively locks the common cw laser to the same quartz microwave oscillator (Truong et al, 2016). The result is sub-hertz mutual coherence, ∼ 120 kHz (4 × 10 −6 cm −1 ) absolute line widths, and 1.1 MHz (3.6 × 10 −5 cm −1 ) absolute frequency accuracy (Truong et al, 2016). The direct output of the combs is spectrally broadened in highly nonlinear fiber to cover 7140-5710 cm −1 (1.4-1.75 µm) and then filtered to isolate the spectral region of interest from 6023 to 6376 cm −1 (1568 to 1660 nm).…”

Section: Overview Of Experimentsmentioning

confidence: 99%

“…The separation of the two delta functions (comb teeth) is negligible compared to the ∼ 5 GHz wide absorption lines but can be exactly incorporated into the spectral model. The exact optical layout of DCS A is given in Truong et al (2016). While following the same basic design, DCS B differs in several technical details.…”

Section: Dual-comb Spectrometermentioning

confidence: 99%

“…Two completely independent open-path DCS instruments are operated over neighboring open-air paths during a 2-week measurement campaign. Although both DCS instruments use fully stabilized frequency combs, they are portable (Truong et al, 2016) and are operated nearly continuously during both day and night through laboratory temperature variations from 17 to 25 • C, strong atmospheric turbulence, and outdoor air temperature variations from 4.6 to 28.9 • C. The retrieved dry mole fractions for the two DCS instruments agree to better than 0.57 ppm 1 (0.14 %) for CO 2 and 7.0 ppb (0.35 %) for CH 4 . This agreement is achieved without any "bias correction" or calibration of either instrument for absolute wavelength or for absolute concentration.…”

Section: Introductionmentioning

confidence: 99%

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Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

et al. 2017

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Abstract. We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km openair paths over a 2-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6023 to 6376 cm −1 (1568 to 1660 nm), corresponding to a 355 cm −1 bandwidth, at 0.0067 cm −1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10 −4 in absorbance without any external calibration of either instrument. The absorption spectra are fit to retrieve path-integrated concentrations for carbon dioxide (CO 2 ), methane (CH 4 ), water (H 2 O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO 2 , 0.35 % (7 ppb) for CH 4 , and 0.40 % (36 ppm) for H 2 O at ∼ 30 s integration time over the 2-week measurement campaign, which included 24 • C outdoor temperature variations and periods of strong atmospheric turbulence. This agreement is at least an order of magnitude better than conventional active-source open-path instrument intercomparisons and is particularly relevant to future regional flux measurements as it allows accurate comparisons of open-path DCS data across locations and time. We additionally compare the open-path DCS retrievals to a World Meteorological Organization (WMO)-calibrated cavity ring-down point sensor located along the path with good agreement. Shortterm and long-term differences between the open-path DCS and point sensor are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the 2-week measurement campaign yields diurnal cycles of CO 2 and CH 4 that are consistent with the presence of local sources of CO 2 and absence of local sources of CH 4 .

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Section: Dual-comb Spectroscopymentioning

confidence: 99%

Section: Overview Of Experimentsmentioning

confidence: 99%

Section: Overview Of Experimentsmentioning

confidence: 99%

Section: Dual-comb Spectrometermentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

et al. 2017

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Phase‐Stable Multidimensional Coherent Spectroscopy Based on Dual‐Comb Interferometry

Zuo,

Gu,

Wang

et al. 2024

Advanced Optical Materials

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Multidimensional coherent spectroscopy (MDCS) is a highly intriguing field for the unique capacities to unravel quantum pathways of microscopic dynamics and discern different dipole–dipole interactions. These capabilities are not simultaneously accessible through any other techniques. The foundation of MDCS lies in the stable phase and accurate time information of the multi‐pulse sequences involved. Achieving the phase stability has traditionally relied on ingenious geometric optical designs and multiple feedback control systems, albeit at the cost of complexity. In this letter, a phase stability scheme for high‐resolution MDCS is proposed by replacing traditional laser sources with two highly coherent frequency combs. By employing dual‐comb interferometry, the phase distribution across a broad spectral range and the time information of all the excitation pulses are precisely measured, even in setups that lack phase stability. In the experiment, a rephasing MDCS of rubidium atoms is obtained by applying this approach, wherein the comb resolution is utilized to differentiate the couplings of hyperfine energy levels. This scheme simplifies the structure of MDCS and holds potential for applications in other MDCS systems involving many‐body interactions and non‐absorptive resonances.

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Stable Optical Frequency Comb Distribution Enabled by Hollow‐Core Fibers

Feng

Marra

Zhang

et al. 2022

Laser & Photonics Reviews

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Over the last two decades, optical frequency combs (OFCs) have enabled some of the most accurate measurements in physics. Distributing light from OFCs via optical fibers could make these high-accuracy measurement tools available more widely, from a few dedicated metrology laboratories to other laboratories and industry. However, the performance of distributed OFCs is strongly limited by impairments of standard single mode fiber (SMF), most notably its thermal sensitivity of chromatic dispersion, for which no compensation technique has been shown to date. To overcome this limitation, use of a new class of optical fiber is suggested here: a hollow core fiber (HCF), which offers more than an order of magnitude lesser such impairment. The measured OFC frequency stability of the optical mode and mode spacing reaches 1.8 × 10 −19 and 1.5 × 10 −17 at a few thousand seconds, respectively, after transmitting through 7.7 km of HCF. To the best of knowledge, this is the best ever performance for km-lengths of fiber-based OFC distribution. Besides, other HCF advantages over SMF in this application are discussed. Specifically, HCFs offer over an order of magnitude lower thermal sensitivity of propagation delay, several orders of magnitude lower optical nonlinearity, and almost ten times lower chromatic dispersion.

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Accurate frequency referencing for fieldable dual-comb spectroscopy

Cited by 95 publications

References 35 publications

Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

Intercomparison of open-path trace gas measurements with two dual-frequency-comb spectrometers

Phase‐Stable Multidimensional Coherent Spectroscopy Based on Dual‐Comb Interferometry

Stable Optical Frequency Comb Distribution Enabled by Hollow‐Core Fibers

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