| 1. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Cavity-enhanced optical frequency combs spectroscopy in the near- and mid-infrared
- 2016
-
Ingår i: Imaging and applied optics 2016. - : OSA - The Optical Society. - 9781943580156
-
Konferensbidrag (refereegranskat)abstract
- We present the recent developments in high-resolution Fourier transform spectroscopy based on optical frequency combs for precision measurements and combustion diagnostics, and the first implementation of continuous-filtering Vernier spectroscopy in the mid-infrared wavelength range for fast multispecies detection.
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| 2. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Measurement and assignment of double-resonance transitions to the 8900-9100- cm-1 levels of methane
- 2021
-
Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information. - : American Physical Society. - 2469-9926 .- 2469-9934. ; 103:2
-
Tidskriftsartikel (refereegranskat)abstract
- Optical-optical double-resonance spectroscopy with a continuous wave pump and frequency comb probe allows measurement of sub-Doppler transitions to highly excited molecular states over a wide spectral range with high frequency accuracy. We report on assessment and characterization of sub-Doppler double-resonance transitions in methane measured using a 3.3-μm continuous wave optical parametric oscillator as a pump and a 1.67-μm frequency comb as a probe. The comb spectra were recorded using a Fourier transform spectrometer with comb-mode-limited resolution. With the pump tuned to nine different transitions in the ν3 fundamental band, we detected 36 ladder-type transitions to the 3ν3 overtone band region, and 18 V-type transitions to the 2ν3 overtone band. We describe in detail the experimental approach and the pump stabilization scheme, which currently limits the frequency accuracy of the measurement. We present the data analysis procedure used to extract the frequencies and intensities of the probe transitions for parallel and perpendicular relative pump-probe polarization. We compare the center frequencies and relative intensities of the ladder-type transitions to theoretical predictions from the TheoReTS and ExoMol line lists, demonstrating good agreement with TheoReTS.
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| 3. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Sub-Doppler Double-Resonance Spectroscopy of Methane Using a Frequency Comb Probe
- 2021
-
Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 126:6
-
Tidskriftsartikel (refereegranskat)abstract
- We report the first measurement of sub-Doppler molecular response using a frequency comb by employing the comb as a probe in optical-optical double-resonance spectroscopy. We use a 3.3 μm continuous wave pump and a 1.67 μm comb probe to detect sub-Doppler transitions to the 2ν3 and 3ν3 bands of methane with ∼1.7 MHz center frequency accuracy. These measurements provide the first verification of the accuracy of theoretical predictions from highly vibrationally excited states, needed to model the high-temperature spectra of exoplanets. Transition frequencies to the 3ν3 band show good agreement with the TheoReTS line list.
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| 4. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Sub-doppler double-resonance spectroscopy of methane using a frequency comb probe
- 2020
-
Ingår i: Conference on Lasers and Electro-Optics. - : Optica Publishing Group (formerly OSA). - 9781943580767 - 9781728144184
-
Konferensbidrag (refereegranskat)abstract
- We use a 3.3 µm continuous wave optical parametric oscillator as a pump and a 1.67 µm frequency comb as a probe to record 36 sub-Doppler double-resonance transitions in the 3v3 band of methane (including 26 previously unreported) with ~1.5 MHz center frequency accuracy.
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| 5. |
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| 6. |
- Hjältén, Adrian, 1988-, et al.
(författare)
-
Accurate measurement and assignment of high rotational energy levels of the 3v3 ← v3 band of methane
- 2023
-
Ingår i: 2023 conference on lasers and electro-optics, CLEO 2023. - : IEEE. - 9781957171258 - 9781665455688
-
Konferensbidrag (refereegranskat)abstract
- We use optical-optical double-resonance spectroscopy with a high-power continuous wave pump and a cavity-enhanced comb probe to expand sub-Doppler measurements of the 3v3 ← v3 band of CH4 to higher rotational levels. We assign the final states using combination differences, i.e., by reaching the same state using different pump/probe combinations.
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| 7. |
- Johansson, Alexandra C., et al.
(författare)
-
Broadband calibration-free cavity-enhanced complex refractive index spectroscopy using a frequency comb
- 2018
-
Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 26:16, s. 20633-20648
-
Tidskriftsartikel (refereegranskat)abstract
- We present broadband cavity-enhanced complex refractive index spectroscopy (CE-CRIS), a technique for calibration-free determination of the complex refractive index of entire molecular bands via direct measurement of transmission modes of a Fabry-Perot cavity filled with the sample. The measurement of the cavity transmission spectrum is done using an optical frequency comb and a mechanical Fourier transform spectrometer with sub-nominal resolution. Molecular absorption and dispersion spectra (corresponding to the imaginary and real parts of the refractive index) are obtained from the cavity mode broadening and shift retrieved from fits of Lorentzian profiles to the individual cavity modes. This method is calibration-free because the mode broadening and shift are independent of the cavity parameters such as the length and mirror reflectivity. In this first demonstration of broadband CE-CRIS we measure simultaneously the absorption and dispersion spectra of three combination bands of CO2 in the range between 1525 nm and 1620 nm and achieve good agreement with theoretical models. This opens up for precision spectroscopy of the complex refractive index of several molecular bands simultaneously.
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| 8. |
- Johansson, Alexandra C., 1987-, et al.
(författare)
-
Broadband Complex Refractive Index Spectroscopy via Measurement of Cavity Modes
- 2018
-
Ingår i: 2018 Conference on Lasers and Electro-Optics (CLEO). - : IEEE. - 9781943580422
-
Konferensbidrag (refereegranskat)abstract
- We retrieve high precision absorption and dispersion spectra of the 3v(1)+v(3) band of CO2 from direct measurement of cavity transmission modes using an optical frequency comb and a mechanical Fourier transfolin spectrometer with sub-nominal resolution.
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| 9. |
- Johansson, Alexandra C., 1987-, et al.
(författare)
-
Cavity-enhanced complex refractive index spectroscopy of entire molecular bands using a frequency comb
- 2018
-
Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781943580477
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate broadband calibration-free complex refractive index spectroscopy of entire molecular bands by direct measurement of transmission modes of a Fabry-Perot cavity using frequency comb-based Fourier transform spectrometer with sub-nominal resolution.
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| 10. |
|
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| 11. |
- Johansson, Alexandra C., et al.
(författare)
-
Faraday rotation spectroscopy using an optical frequency comb
- 2017
-
Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
-
Konferensbidrag (refereegranskat)abstract
- Summary form only given. The mid-infrared (MIR) part of the optical spectrum (3-12 μm) houses the fundamental absorption bands of a multitude of environmentally important molecules, but the abundance of water absorption often causes interference with the target species and makes concentration measurement inaccurate. The broad spectral coverage of optical frequency comb spectroscopy (OFCS) provides access to entire ro-vibrational bands and allows more accurate concentration quantification and retrieval of sample temperature. To further improve detection sensitivity of paramagnetic species in the presence of interfering species, we combine a MIR optical frequency comb with the Faraday rotation spectroscopy (FRS) technique [I], which is insensitive to interferences from diamagnetic molecules, such as H 2 O, CO 2 , and CO. In FRS, the rotation of the polarization induced by an external magnetic field in the vicinity of paramagnetic molecular transitions is translated to an intensity change by the use of a polarization analyzer, which effectively removes the influence of any non-paramagnetic species. In the proof of principle demonstration of OFC-FRS we detect nitric oxide (NO) in the presence of water at 5.3 μm using a Fourier transform spectrometer.
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| 12. |
- Johansson, Alexandra C., 1987-, et al.
(författare)
-
Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy
- 2016
-
Ingår i: Light, Energy and the Environment. - : Optica Publishing Group (formerly OSA). - 9781557528209
-
Konferensbidrag (refereegranskat)abstract
- We describe the principles and implementation of Fourier-transform-based cavityenhanced optical frequency comb spectroscopy that uses phase modulation at the cavity free spectral range frequency to achieve high sensitivity over broad spectral range.
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| 13. |
- Johansson, Alexandra C., 1987-, et al.
(författare)
-
Precise comb-based fourier transform spectroscopy for line parameter retrieval
- 2019
-
Ingår i: 2019 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference (CLEO/EUROPE-EQEC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781728104690
-
Konferensbidrag (refereegranskat)abstract
- Accurate parameters of molecular transitions are needed for data analysis in many applications, ranging from atmospheric research to astrophysics and determination of fundamental constants. Optical frequency comb Fourier transform spectroscopy (OFC-FTS) is particularly well-suited for high-precision measurements of broadband molecular spectra. From these spectra, the parameters of individual transitions - all measured simultaneously under the same experimental conditions - can be determined. We use a mechanical OFC-FTS spectrometer with sub-nominal resolution [1, 2] to perform precise broadband measurements of entire molecular bands of CO2 using either direct absorption spectroscopy or cavity-enhanced complex refractive index spectroscopy (CE-CRIS) [3] and we extract line parameters for line shapes beyond the Voigt profile.
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| 14. |
- Johansson, Alexandra C., et al.
(författare)
-
Signal line shapes of Fourier-transform cavity-enhanced frequency modulation spectroscopy with optical frequency combs
- 2017
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - 0740-3224 .- 1520-8540. ; 34:2, s. 358-365
-
Tidskriftsartikel (refereegranskat)abstract
- We present a thorough analysis of the signal line shapes of Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS). We discuss the signal dependence on the ratio of the modulation frequency, f(m), to the molecular linewidth, G. We compare a full model of the signals and a simplified absorption-like analytical model that has high accuracy for low f(m)/G ratios and is much faster to compute. We verify the theory experimentally by measuring and fitting the NICE-OFCS spectra of CO2 at 1575 nm using a system based on an Er: fiber femtosecond laser and a cavity with a finesse of similar to 11000.
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| 15. |
- Khodabakhsh, Amir, et al.
(författare)
-
Cavity-Enhanced Continuous-Filtering Vernier Spectroscopy at 3.3 mu m using a Femtosecond Optical Parametric Oscillator
- 2017
-
Ingår i: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS EUROPE & EUROPEAN QUANTUM ELECTRONICS CONFERENCE (CLEO/EUROPE-EQEC). - : IEEE. - 9781509067367 ; , s. CH_2_2-
-
Konferensbidrag (refereegranskat)abstract
- Optical frequency comb spectroscopy in the mid-infrared fingerprint region combines broad spectral bandwidth with high detection sensitivity and allows simultaneous detection of trace amounts of many molecular species. We have recently demonstrated a continuous-filtering Vernier spectrometer based on a mid-infrared optical frequency comb and an enhancement cavity for fast and sensitive detection of CH4 [1]. Here we present an improved, fully automatized and frequency calibrated continuous-filtering Vernier spectrometer, schematically shown in Fig. 1(a). The comb source is a doubly resonant optical parametric oscillator (DROPO) based on an orientation-patterned GaAs crystal synchronously pumped by a Tm:fiber femtosecond laser (125 MHz repetition rate, frep). The signal comb (3.1–3.4 µm, 30 mW) is mode matched to a 60-cm long Vernier enhancement cavity with a finesse of ~350 at 3.25 μm, placed in an enclosure that can be filled with the gas sample. The output mirror is attached to a PZT and mounted on a translation stage. When the cavity free spectral range is perfectly matched to twice the frep (250 MHz) every other signal comb mode is transmitted through the cavity. By detuning the cavity length from this perfect match position the cavity resonances act as a filter and transmit groups of comb modes called Vernier orders [2]. A diffraction grating mounted on a galvo-scanner separates these orders after the cavity and the chosen order is sent to the detection system. The Vernier order is tuned across the signal comb spectrum by scanning the cavity length (at 20 Hz) and the grating is rotated synchronously to fix the order in space and allow acquisition of the entire spectrum in 25 ms. Any residual mismatch between the cavity length scan and the grating rotation is compensated by a feedback loop acting on the frep of the pump laser and the PZT of the Vernier cavity [2]. A Fabry-Perot etalon is used for frequency calibration of the spectrometer. Figure 1(b) shows in black the normalized transmission spectrum of a sample containing 5.0 ppm CH4 and 160 ppm water. The red and blue curves show the corresponding fit of the Vernier spectrum [3] of CH4 and water, respectively, calculated using Voigt profiles, line parameters from the HITRAN database, and the experimentally determined cavity finesse. The figure of merit of the spectrometer is 1×10−9cm−1 Hz−1∕2 per spectral element and multiline fitting yields minimum detectable concentration of CH4 of 2 ppb in 25 ms, translating into 400 ppt Hz−1∕2 Since the spectrum of the signal comb covers the fundamental C-H stretch transitions we expect low detection limits for other hydrocarbons as well. In conclusion, mid-infrared comb-based continuous-filtering Vernier spectroscopy allows fast and highly sensitive measurement of broadband absorption spectra using a robust and compact detection system.
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| 16. |
|
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| 17. |
- Khodabakhsh, Amir, et al.
(författare)
-
Cavity-Enhanced Optical Frequency Comb Spectroscopy of High-Temperature Water in a Flame
- 2015
-
Ingår i: 2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - 9781557529688
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate detection of broadband high-temperature water spectra in a laminar, premixed methane/air flat flame using high-resolution near-infrared cavity-enhanced optical frequency comb spectroscopy incorporating a fast-scanning Fourier transform spectrometer.
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| 18. |
|
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| 19. |
- Khodabakhsh, Amir, et al.
(författare)
-
Fourier transform and Vernier spectroscopy using an optical frequency comb at 3-5.4 μm
- 2016
-
Ingår i: Optics Letters. - 0146-9592 .- 1539-4794. ; 41:11, s. 2541-2544
-
Tidskriftsartikel (refereegranskat)abstract
- We present a versatilemid-infrared frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable in the 3-5.4 mu m range and two detection methods: a Fourier transform spectrometer (FTS) and a continuous-filtering Vernier spectrometer (CF-VS). Using the FTS with a multipass cell, we measure high precision broadband absorption spectra of CH4 at 3.3 mu m and NO at 5.25 mu m, the latter for the first time with comb spectroscopy, and we detect atmospheric species (CH4, CO, CO2, and H2O) in air in the signal and idler ranges. Multiline fitting yields minimum detectable concentrations of 10-20 ppbHz-1/2 for CH4, NO, and CO. For the first time in the mid-infrared, we perform CF-VS using an enhancement cavity, a grating, and a single detector, and we measure the absorption spectrum of CH4 and H2O in ambient air at similar to 3.3 m mu, reaching a 40 ppb concentration detection limit for CH4 in 2 ms.
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| 20. |
- Khodabakhsh, Amir, et al.
(författare)
-
Fourier transform and vernier spectroscopy with a mid-infrared optical frequency comb
- 2016
-
Ingår i: Light, energy and the environment. - : Optica Publishing Group (formerly OSA). - 9780960038046
-
Konferensbidrag (refereegranskat)abstract
- We present a versatile frequency comb spectroscopy system based on a doubly resonant optical parametric oscillator tunable between 3-5.4 μm and two detection methods: a Fourier transform spectrometer and a continuous-filtering Vernier spectrometer.
|
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| 21. |
- Khodabakhsh, Amir, et al.
(författare)
-
Fourier-Transform-Based Noise-Immune Cavity-Enhanced Optical Frequency Comb Spectroscopy
- 2015
-
Ingår i: 2015 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - 9781557529688
-
Konferensbidrag (refereegranskat)abstract
- We achieve absorption sensitivity of 6.4 x 10(-11) cm(-1) Hz(-1/2) per spectral element with near-infrared Fourier-transform-based noise-immune cavity-enhanced optical frequency comb spectroscopy (NICE-OFCS), which allows detection of CO2 at ppb concentration levels.
|
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| 22. |
- Khodabakhsh, Amir, 1983-, et al.
(författare)
-
Mid-infrared continuous-filtering Vernier spectroscopy using a doubly resonant optical parametric oscillator
- 2017
-
Ingår i: Applied physics. B, Lasers and optics (Print). - : Springer. - 0946-2171 .- 1432-0649. ; 123
-
Tidskriftsartikel (refereegranskat)abstract
- We present a continuous-filtering Vernier spectrometer operating in the 3.15–3.4 µm range, based on a femtosecond doubly resonant optical parametric oscillator, a cavity with a finesse of 340, a grating mounted on a galvo scanner, and two photodiodes. The spectrometer allows acquisition of one spectrum spanning 250 nm of bandwidth in 25 ms with 8 GHz resolution, sufficient to detect molecular lines at atmospheric pressure. An active lock ensures good frequency and intensity stability of the consecutive spectra and enables continuous signal acquisition and efficient averaging. The relative frequency scale is calibrated using a Fabry–Perot etalon or, alternatively, the galvo scanner position signal. We measure spectra of a calibrated CH4 gas sample as well as dry and laboratory air and extract CH4 and H2O concentrations by multiline fitting of model spectra. The figure of merit of the spectrometer is 1.7 × 10−9 cm−1 Hz−1/2 per spectral element and the minimum detectable concentration of CH4 is 360 ppt Hz−1/2, averaging down to 90 ppt after 16 s.
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| 23. |
- Khodabakhsh, Amir, et al.
(författare)
-
Near-infrared Fourier transform cavity-enhanced optical frequency comb spectroscopy
- 2014
-
Ingår i: Fourier Transform Spectroscopy. - : OSA - The Optical Society. - 9780960038046 ; , s. 3-
-
Konferensbidrag (refereegranskat)abstract
- Using Fourier transform-based cavity-enhanced optical frequency comb spectroscopy around 1.57 μm we measure high precision low pressure spectra of the 3v1+ v3 band of CO2 and high temperature H2O and OH spectra in a premixed methane/air flat flame.
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| 24. |
|
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| 25. |
- Lu, Chuang, et al.
(författare)
-
Cavity-Enhanced Frequency Comb Vernier Spectroscopy
- 2022
-
Ingår i: Photonics. - : MDPI. - 2304-6732. ; 9:4
-
Forskningsöversikt (refereegranskat)abstract
- Vernier spectroscopy is a frequency comb-based technique employing optical cavities for filtering of the comb and for enhancement of the interaction length with the sample. Depending on the ratio of the cavity free spectral range and the comb repetition rate, the cavity transmits either widely spaced individual comb lines (comb-resolved Vernier spectroscopy) or groups of comb lines, called Vernier orders (continuous-filtering Vernier spectroscopy, CF-VS). The cavity filtering enables the use of low-resolution spectrometers to resolve the individual comb lines or Vernier orders. Vernier spectroscopy has been implemented using various near- and mid-infrared comb sources for applications ranging from trace gas detection to precision spectroscopy. Here, we present the principles of the technique and provide a review of previous demonstrations of comb-resolved and continuous-filtering Vernier spectroscopy. We also demonstrate two new implementations of CF-VS: one in the mid-infrared, based on a difference frequency generation comb source, with a new and more robust detection system design, and the other in the near-infrared, based on a Ti:sapphire laser, reaching high sensitivity and the fundamental resolution limit of the technique.
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| 26. |
- Maslowski, P., et al.
(författare)
-
Optical frequency comb spectroscopy for gas metrology and trace gas detection
- 2017
-
Ingår i: 2017 Conference on lasers and electro-optics (CLEO). - : IEEE. - 9781943580279 - 9781538620199
-
Konferensbidrag (refereegranskat)abstract
- We report recent developments of comb-based broadband absorption spectroscopy. The comb-line resolving approaches and Fourier transform spectroscopy with sub-nominal resolution overcome the frequency resolution limits of conventional techniques. Advantages for various applications will be discussed.
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| 27. |
- Maslowski, Piotr, et al.
(författare)
-
Surpassing the path-limited resolution of Fourier-transform spectrometry with frequency combs
- 2016
-
Ingår i: Physical Review A. - 2469-9926. ; 93:2
-
Tidskriftsartikel (refereegranskat)abstract
- We overcome the resolution limit of Fourier-transform spectrometry and measure instrumental line-shape-free broadband molecular spectra with lines narrower than the optical path-limited resolution. We do this by using an optical frequency comb and precisely matching the maximum delay range of the spectrometer to the comb line spacing to measure the intensities of the individual comb lines. This method allows measurements of undistorted high-resolution spectra with acquisition time and interferometer length reduced by orders of magnitude and with frequency scale accuracy given by the comb.
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| 28. |
- Rutkowski, Lucile, et al.
(författare)
-
An experimental water line list at 1950 K in the 6250–6670 cm−1 region
- 2018
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 205, s. 213-219
-
Tidskriftsartikel (refereegranskat)abstract
- An absorption spectrum of (H2O)-O-16 at 1950 K is recorded in a premixed methane/air flat flame using a cavity-enhanced optical frequency comb-based Fourier transform spectrometer. 2417 absorption lines are identified in the 6250-6670 cm(-1) region with an accuracy of about 0.01 cm(-1). Absolute line intensities are retrieved using temperature and concentration values obtained by tunable diode laser absorption spectroscopy. Line assignments are made using a combination of empirically known energy levels and predictions from the new POKAZATEL variational line list. 2030 of the observed lines are assigned to 2937 transitions, once blends are taken into account. 126 new energy levels of (H2O)-O-16 are identified. The assigned transitions belong to 136 bands and span rotational states up to J = 27.
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| 29. |
- Rutkowski, Lucile, et al.
(författare)
-
Broadband and high resolution direct measurement of cavity resonances
- 2017
-
Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
-
Konferensbidrag (refereegranskat)abstract
- Summary form only given. Optical frequency combs offer unprecedented combination of broad bandwidth and high resolution and their coupling to enhancement cavities provides high sensitivity for spectroscopic measurements. Here we use a frequency-comb-based Fourier transform spectrometer (FTS) to measure the narrow resonances of a high-finesse cavity over a bandwidth of 100 nm around 1.55 μm and derive the group delay dispersion (GDD) of the cavity mirrors with precision below 1 fs 2 from the cavity resonance frequencies. We do this using a method that allows precise sampling of the comb intensities using an FTS with nominal resolution matched to the comb repetition rate (f rep ) [1, 2], and we demonstrate that sub-MHz resolution is achieved.
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| 30. |
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| 31. |
- Rutkowski, Lucile, et al.
(författare)
-
Cavity-enhanced Fourier transform and Vernier spectroscopy with optical frequency combs
- 2014
-
Ingår i: Frontiers in Optics 2016. - : Optica Publishing Group (formerly OSA). - 9781943580194
-
Konferensbidrag (refereegranskat)abstract
- We present optical frequency comb Fourier transform spectroscopy in the near-infrared wavelength range for broadband high-resolution measurements of molecular spectra, and the first implementation of continuous-filtering Vernier spectroscopy in the mid-infrared range for fast multispecies detection.
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| 32. |
- Rutkowski, Lucile, et al.
(författare)
-
Continuous Vernier filtering of an optical frequency comb for broadband cavity-enhanced molecular spectroscopy
- 2017
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier BV. - 0022-4073 .- 1879-1352. ; 187, s. 204-214
-
Tidskriftsartikel (refereegranskat)abstract
- We have recently introduced the Vernier-based Direct Frequency Comb Cavity-Enhanced Spectroscopy technique which allows us to record broadband spectra at high sensitivity and GHz resolution (Rutkowski and Morville, 2014) [1]. We discuss here the effect of Vernier filtering on the observed lineshapes in the 3v+delta band of water vapor and the entire A-band of oxygen around 800 nm in ambient air. We derive expressions for the absorption profiles resulting from the continuous Vernier filtering method, testing them on spectra covering more than 2000 cm(-1) around 12,500 cm(-1). With 31,300 independent spectral elements acquired at the second time scale, an absorption baseline noise of 2 x 10(-8) cm(-1) is obtained, providing a figure of merit of 1.1 x 10(-10) cm(-1)/root Hz per spectral element with a cavity finesse of 3000 and a cavity round-trip length around 3.3 m.
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| 33. |
- Rutkowski, Lucile, et al.
(författare)
-
Detection of OH and H2O in an Atmospheric Flame by Near-Infrared Optical Frequency Comb Spectroscopy
- 2017
-
Ingår i: 2017 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC). - : IEEE. - 9781509067367
-
Konferensbidrag (refereegranskat)abstract
- Absorption spectroscopy is attractive for combustion diagnostics because it allows in-situ and calibration-free quantification of reactants/products and thermometry. However, spectra measured at atmospheric pressure in the near-infrared telecom range, where laser sources and optical components are readily available, suffer from strong water interference. Cavity-enhanced optical frequency comb spectroscopy (CE-OFCS) is well suited for detection of other species, as it provides broad bandwidth with high signal-to-noise ratio and resolution, and allows de-convolving the spectra hidden among water transitions. Here we report detection of OH in the presence of H2O in an atmospheric premixed methane/air flat flame by CE-OFCS at 1.57 μm. We demonstrate a new water line list that is more accurate than HITEMP [1] and we isolate the OH lines by dividing spectra taken at different heights above the burner (HABs) to retrieve OH concentration and flame temperature.
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| 34. |
- Rutkowski, Lucile, et al.
(författare)
-
Detection of OH in an atmospheric flame at 1.5 μm using optical frequency comb spectroscopy
- 2016
-
Ingår i: Photonics Letters of Poland. - : Photonics Society of Poland. - 2080-2242. ; 8:4, s. 110-112
-
Tidskriftsartikel (refereegranskat)abstract
- We report broadband detection of OH in a premixed CH4/air flat flame at atmospheric pressure using cavity-enhanced absorption spectroscopy based on an Er:fiber femtosecond laser and a Fourier transform spectrometer. By taking ratios of spectra measured at different heights above the burner we separate twenty OH transitions from the largely overlapping water background. We retrieve from fits to the OH lines the relative variation of OH concentration and flame temperature with a height above the burner and compare them with the 1D simulations of flame structure.
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| 35. |
- Rutkowski, Lucile, et al.
(författare)
-
Experimental 1.5-1.6 μm water line list at 1950 K
- 2018
-
Ingår i: Optics InfoBase Conference Papers. - : Optica Publishing Group. - 9781943580477
-
Konferensbidrag (refereegranskat)abstract
- We demonstrate a high-temperature water absorption spectrum measured in a flame using cavity-enhanced frequency comb-based Fourier transform spectroscopy. The retrieved transition intensities and frequencies are assigned using the POKAZATEL line list.
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| 36. |
- Rutkowski, Lucile, et al.
(författare)
-
Measurement of H2O and OH in a Flame by Optical Frequency Comb Spectroscopy
- 2016
-
Ingår i: Proceedings Conference on Lasers and Electro-Optics. - Washington, D.C. : IEEE. - 9781943580118
-
Konferensbidrag (refereegranskat)abstract
- We measure broadband H2O and OH spectra in a flame using near-infrared cavity-enhanced Fourier transform optical frequency comb spectroscopy, we retrieve temperature and OH concentration, and compare water spectra to an improved line list.
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| 37. |
- Rutkowski, Lucile, et al.
(författare)
-
Mechanical Fourier Transform Spectrometer with kHz Resolution
- 2017
-
Ingår i: 2017 conference on lasers and electro-optics (CLEO). - : IEEE. - 9781943580279
-
Konferensbidrag (refereegranskat)abstract
- We measure simultaneously 11000 resonances of a high-finesse cavity with kHz level resolution using optical frequency comb Fourier transform spectroscopy and retrieve the dispersion of the cavity mirrors from the cavity mode spacing.
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| 38. |
|
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| 39. |
- Rutkowski, Lucile, et al.
(författare)
-
Optical frequency comb Fourier transform spectroscopy with sub-nominal resolution and precision beyond the Voigt profile
- 2018
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 204, s. 63-73
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Tidskriftsartikel (refereegranskat)abstract
- Broadband precision spectroscopy is indispensable for providing high fidelity molecular parameters for spectroscopic databases. We have recently shown that mechanical Fourier transform spectrometers based on optical frequency combs can measure broadband high-resolution molecular spectra undistorted by the instrumental line shape (ILS) and with a highly precise frequency scale provided by the comb. The accurate measurement of the power of the comb modes interacting with the molecular sample was achieved by acquiring single-burst interferograms with nominal resolution matched to the comb mode spacing. Here we describe in detail the experimental and numerical steps needed to achieve sub-nominal resolution and retrieve ILS-free molecular spectra, i.e. with ILS-induced distortion below the noise level. We investigate the accuracy of the transition line centers retrieved by fitting to the absorption lines measured using this method. We verify the performance by measuring an ILS-free cavity-enhanced low-pressure spectrum of the 3ν1 + ν3 band of CO2 around 1575 nm with line widths narrower than the nominal resolution. We observe and quantify collisional narrowing of absorption line shape, for the first time with a comb-based spectroscopic technique. Thus retrieval of line shape parameters with accuracy not limited by the Voigt profile is now possible for entire absorption bands acquired simultaneously.
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| 40. |
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| 41. |
- Rutkowski, Lucile, et al.
(författare)
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Sensitive and broadband measurement of dispersion in a cavity using a Fourier transform spectrometer with kHz resolution
- 2017
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Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 25:18, s. 21711-21718
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Tidskriftsartikel (refereegranskat)abstract
- Optical cavities provide high sensitivity to dispersion since their resonance frequencies depend on the index of refraction. We present a direct, broadband, and accurate measurement of the modes of a high finesse cavity using an optical frequency comb and a mechanical Fourier transform spectrometer with a kHz-level resolution. We characterize 16000 longitudinal cavity modes spanning 16 THz of bandwidth in terms of center frequency, linewidth, and amplitude. Using the center frequencies we retrieve the group delay dispersion of the cavity mirror coatings and pure N2 with 0.1 fs2 precision and 1 fs2 accuracy, as well as the refractivity of the 3ν1 +ν3 absorption band of CO2 with 5 × 10‒12 precision. This opens up for broadband refractive index metrology and calibration-free spectroscopy of entire molecular bands.
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| 42. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Double-Resonance Spectroscopy of Methane Using a Comb Probe
- 2021
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Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021. - : IEEE Lasers and Electro-Optics Society. - 9781665418768
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Konferensbidrag (refereegranskat)abstract
- Optical-optical double resonance (OODR) spectroscopy is a powerful tool for the experimental assignment of highly-excited molecular states, which in turn is needed for verification of the accuracy of theoretical predictions of high-temperature spectra observed in exoplanets and in combustion environments. Previous implementations of OODR used either continuous wave (cw) lasers, which limit the number of transitions that can be detected, or pulsed lasers, which limit the spectral resolution. Recently, we demonstrated OODR with a cw pump and a frequency comb probe and applied it to the detection and assignment of methane transitions in the 3ν 3 ← ν 3 range with sub-Doppler resolution over 200 cm -1 of bandwidth [1]. The pump [see Fig. 1(a) ] was a 1 W 3.3m idler of a cw optical parametric oscillator (cw-OPO), stabilized to the Lamb dip in a selected CH 4 transition in the ν 3 band using a signal from a reference cell. The probe was an amplified fully-stabilized Er:fiber comb ( f rep = 250 MHz), whose center wavelength was shifted to 1.67m using a soliton self-frequency shift fiber (SSSF). The sample of pure CH 4 was contained in an 80-cm-long single-pass cell cooled by liquid nitrogen. The probe spectra were detected using a Fourier transform spectrometer (FTS) with comb-mode-limited resolution [2] , and the final interleaved spectra had 2 MHz sampling point spacing. Figure 1(b) shows the 3ν 3 ← ν 3 R(1) transition at 6046.36008(5) cm -1 , detected with the pump on the ν 3 R(0) line. We measured, fit and assigned 36 probe transitions with the pump tuned to 9 different transitions. Figure 1(d) shows a comparison of the probe transition wavenumbers to predictions from the TheoReTS database [3] , demonstrating agreement within 1 cm -1.
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| 43. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Measurement and Assignment of Hot-Band Methane Transitions with Sub-MHz Accuracy
- 2022
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Ingår i: CLEO: 2022. - : Optica Publishing Group. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We use double-resonance spectroscopy with cavity-enhanced comb probe to measure sub-Doppler transitions in the 3ν3←ν3 band of CH4. We assign the final states using different pump/probe combinations reaching the same state, and the dependence of line intensities on relative pump/probe polarization.
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| 44. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Optical-optical double-resonance spectroscopy of methane using a cavity-enhanced comb probe
- 2021
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Ingår i: OSA Technical Digest. - : Optical Society of America. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We implement a cavity to enhance the absorption of a frequency comb probe in a double-resonance measurement of sub-Doppler 3ν3 ← ν3 methane transitions. This yields two orders of magnitude better sensitivity in 15 times shorter acquisition time compared to previous work using a single-pass cell.
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| 45. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Sub-doppler optical-optical double-resonance spectroscopy of methane using a frequency comb probe
- 2021
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Ingår i: OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES). - : Optical Society of America. - 9781557528209
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Konferensbidrag (refereegranskat)abstract
- We use a 3.3 µm high-power continuous wave pump and a 1.67 µm comb probe to detect transitions in the 3ν3 ← ν3 range of methane with sub-Doppler resolution over 6 THz of bandwidth. We achieve high absorption sensitivity for the comb probe using an enhancement cavity and a Fourier transform spectrometer with auto-balanced detection.
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| 46. |
- Silva de Oliveira, Vinicius, et al.
(författare)
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Sub-Doppler optical-optical double-resonance spectroscopy using a cavity-enhanced frequency comb probe
- 2024
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
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Tidskriftsartikel (refereegranskat)abstract
- Accurate parameters of molecular hot-band transitions, i.e., those starting from vibrationally excited levels, are needed to accurately model high-temperature spectra in astrophysics and combustion, yet laboratory spectra measured at high temperatures are often unresolved and difficult to assign. Optical-optical double-resonance (OODR) spectroscopy allows the measurement and assignment of individual hot-band transitions from selectively pumped energy levels without the need to heat the sample. However, previous demonstrations lacked either sufficient resolution, spectral coverage, absorption sensitivity, or frequency accuracy. Here we demonstrate OODR spectroscopy using a cavity-enhanced frequency comb probe that combines all these advantages. We detect and assign sub-Doppler transitions in the spectral range of the 3ν3 ← ν3 resonance of methane with frequency precision and sensitivity more than an order of magnitude better than before. This technique will provide high-accuracy data about excited states of a wide range of molecules that is urgently needed for theoretical modeling of high-temperature data and cannot be obtained using other methods.
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| 47. |
- Sobon, Grzegorz, et al.
(författare)
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High-power frequency comb source tunable from 2.7 to 4.2 mu m based on difference frequency generation pumped by an Yb-doped fiber laser
- 2017
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Ingår i: Optics Letters. - : OPTICAL SOC AMER. - 0146-9592 .- 1539-4794. ; 42:9, s. 1748-1751
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a broadband mid-infrared (MIR) frequency comb source based on difference frequency generation (DFG) in periodically poled lithium niobate crystal. MIR radiation is obtained via mixing of the output of a 125 MHz repetition rate Yb-doped fiber laser with Raman-shifted solitons generated from the same source in a highly nonlinear fiber. The resulting idler is tunable in the range of 2.7-4.2 mu m, with average output power reaching 237 mW and pulses as short as 115 fs. The coherence of the MIR comb is confirmed by spectral interferometry and heterodyne beat measurements. Applicability of the developed DFG source for laser spectroscopy is demonstrated by measuring absorption spectrum of acetylene at 3.0-3.1 mu m. (C) 2017 Optical Society of America
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