scholarly journals Near-infrared broadband dual-frequency-comb spectroscopy with a resolution beyond the Fourier limit determined by the observation time window

2015 ◽  
Vol 23 (26) ◽  
pp. 33184 ◽  
Author(s):  
Sho Okubo ◽  
Yi-Da Hsieh ◽  
Hajime Inaba ◽  
Atsushi Onae ◽  
Mamoru Hashimoto ◽  
...  
Keyword(s):  
Near Infrared ◽  
Time Window ◽  
Frequency Comb ◽  
Observation Time ◽  
Dual Frequency ◽  
Fourier Limit

scholarly journals Intercomparison of Open-Path Trace Gas Measurements with Two Dual Frequency Comb Spectrometers

2017 ◽  
Author(s):  
Eleanor M. Waxman ◽  
Kevin C. Cossel ◽  
Gar-Wing Truong ◽  
Fabrizio R. Giorgetta ◽  
William C. Swann ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Near Infrared ◽  
Frequency Comb ◽  
Deuterated Water ◽  
Dual Frequency ◽  
Measurement Campaign ◽  
Diurnal Cycles ◽  
Open Path ◽  
Local Sources ◽  
Carbon Dioxide Co2

Abstract. We present the first quantitative intercomparison between two open-path dual comb spectroscopy (DCS) instruments which were operated across adjacent 2-km open-air paths over a two-week period. We used DCS to measure the atmospheric absorption spectrum in the near infrared from 6021 to 6388 cm−1 (1565 to 1661 nm), corresponding to a 367 cm−1 bandwidth, at 0.0067 cm−1 sample spacing. The measured absorption spectra agree with each other to within 5 × 10−4 without any external calibration of either instrument. The absorption spectra are fit to retrieve concentrations for carbon dioxide (CO2), methane (CH4), water (H2O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO2, 0.35 % (7 ppb) for CH4, and 0.40 % (36 ppm) for H2O over the two-week measurement campaign, which included 23 °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 WMO-calibrated cavity ringdown point sensor located along the path with good agreement. Short-term and long-term differences between the two systems are attributed, respectively, to spatial sampling discrepancies and to inaccuracies in the current spectral database used to fit the DCS data. Finally, the two-week measurement campaign yields diurnal cycles of CO2 and CH4 that are consistent with the presence of local sources of CO2 and absence of local sources of CH4.

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

2017 ◽  
Vol 10 (9) ◽  
pp. 3295-3311 ◽  
Author(s):  
Eleanor M. Waxman ◽  
Kevin C. Cossel ◽  
Gar-Wing Truong ◽  
Fabrizio R. Giorgetta ◽  
William C. Swann ◽  
...  
Keyword(s):  
Absorption Spectra ◽  
Near Infrared ◽  
Frequency Comb ◽  
Integration Time ◽  
Deuterated Water ◽  
Dual Frequency ◽  
Measurement Campaign ◽  
Diurnal Cycles ◽  
Open Path ◽  
Local Sources

Abstract. We present the first quantitative intercomparison between two open-path dual-comb spectroscopy (DCS) instruments which were operated across adjacent 2 km open-air 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 (CO2), methane (CH4), water (H2O), and deuterated water (HDO). The retrieved dry mole fractions agree to 0.14 % (0.57 ppm) for CO2, 0.35 % (7 ppb) for CH4, and 0.40 % (36 ppm) for H2O 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. Short-term 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 CO2 and CH4 that are consistent with the presence of local sources of CO2 and absence of local sources of CH4.

scholarly journals Real-time dual frequency comb spectroscopy in the near infrared

2013 ◽  
Vol 102 (12) ◽  
pp. 121116 ◽  
Author(s):  
F. Zhu ◽  
T. Mohamed ◽  
J. Strohaber ◽  
A. A. Kolomenskii ◽  
Th. Udem ◽  
...  
Keyword(s):  
Real Time ◽  
Near Infrared ◽  
Frequency Comb ◽  
Dual Frequency

A PORTABLE DUAL FREQUENCY COMB SPECTROMETER FOR ATMOSPHERIC APPLICATIONS

2016 ◽  
Author(s):  
Kevin Cossel ◽  
Nathan Newbury ◽  
Ian Coddington ◽  
Greg Rieker ◽  
Robert Wright ◽  
...  
Keyword(s):  
Frequency Comb ◽  
Dual Frequency

scholarly journals Near-infrared resonant photoacoustic gas measurement using simultaneous dual-frequency excitation

2010 ◽  
Vol 100 (1) ◽  
pp. 189-194 ◽  
Author(s):  
J. M. Rey ◽  
C. Romer ◽  
M. Gianella ◽  
M. W. Sigrist
Keyword(s):  
Near Infrared ◽  
Dual Frequency ◽  
Gas Measurement ◽  
Frequency Excitation

scholarly journals Direct Observation of Terahertz Frequency Comb Generation in Difference-Frequency Quantum Cascade Lasers

2021 ◽  
Vol 11 (4) ◽  
pp. 1416
Author(s):  
Luigi Consolino ◽  
Malik Nafa ◽  
Michele De Regis ◽  
Francesco Cappelli ◽  
Saverio Bartalini ◽  
...  
Keyword(s):  
Near Infrared ◽  
Quantum Cascade Lasers ◽  
Molecular Spectroscopy ◽  
Frequency Comb ◽  
Frequency Standard ◽  
Difference Frequency ◽  
Heterodyne Detection ◽  
Optical Rectification ◽  
Total Output ◽  
Quantum Cascade

Terahertz quantum cascade laser sources based on intra-cavity difference frequency generation from mid-IR devices are an important asset for applications in rotational molecular spectroscopy and sensing, being the only electrically pumped device able to operate in the 0.6–6 THz range without the need of bulky and expensive liquid helium cooling. Here we present comb operation obtained by intra-cavity mixing of a distributed feedback laser at λ = 6.5 μm and a Fabry–Pérot device at around λ = 6.9 μm. The resulting ultra-broadband THz emission extends from 1.8 to 3.3 THz, with a total output power of 8 μW at 78 K. The THz emission has been characterized by multi-heterodyne detection with a primary frequency standard referenced THz comb, obtained by optical rectification of near infrared pulses. The down-converted beatnotes, simultaneously acquired, confirm an equally spaced THz emission down to 1 MHz accuracy. In the future, this setup can be used for Fourier transform based evaluation of the phase relation among the emitted THz modes, paving the way to room-temperature, compact, and field-deployable metrological grade THz frequency combs.

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