| 1. |
- Axner, Ove, et al.
(författare)
-
Ability of gas modulation to reduce the pickup of drifts in refractometry
- 2021
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Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optical Society of America. - 0740-3224 .- 1520-8540. ; 38:8, s. 2419-2436
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology for assessment of gas refractivity, molar density, and pressure that, by a rapid gas modulation, exhibits a reduced susceptibility to various types of disturbances. Although previously demonstrated experimentally, no detailed analysis of its ability to reduce the pickup of drifts has yet been given. This work provides an explication of to what extent modulated refractometry in general, and GAMOR in particular, can reduce drifts, predominantly those of the cavity lengths, gas leakages, and outgassing. It is indicated that the methodology is insensitive to the linear parts of so-called campaign-persistent drifts and that it has a significantly reduced susceptibility to others. This makes the methodology suitable for high-accuracy assessments and out-of-laboratory applications.
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| 2. |
- Axner, Ove, et al.
(författare)
-
Ability of gas modulation to reduce the pickup of drifts in refractometry
- 2021
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : Optica Publishing Group. - 0740-3224 .- 1520-8540. ; 38:8, s. 2419-2436
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology for assessment of gas refractivity, molar density, and pressure that, by a rapid gas modulation, exhibits a reduced susceptibility to various types of disturbances. Although previously demonstrated experimentally, no detailed analysis of its ability to reduce the pickup of drifts has yet been given. This work provides an explication of to what extent modulated refractometry in general, and GAMOR in particular, can reduce drifts, predominantly those of the cavity lengths, gas leakages, and outgassing. It is indicated that the methodology is insensitive to the linear parts of so-called campaign-persistent drifts and that it has a significantly reduced susceptibility to others. This makes the methodology suitable for high-accuracy assessments and out-of-laboratory applications
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| 3. |
- Axner, Ove, et al.
(författare)
-
Ability of gas modulation to reduce the pickup of fluctuations in refractometry
- 2020
-
Ingår i: Journal of the Optical Society of America. B, Optical physics. - : OSA - The Optical Society. - 0740-3224 .- 1520-8540. ; 37:7, s. 1956-1965
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Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry is a technique for assessment of gas refractivity, density, and pressure that, by a rapid modulation of the gas, provides a means to significantly reduce the pickup of fluctuations. Although its unique feature has previously been demonstrated, no detailed explication or analysis of this ability has yet been given. This work provides a theoretical explanation, in terms of the length of the modulation cycle, of the extent to which gas modulation can reduce the pickup of fluctuations. It is indicated that a rapid modulation can significantly reduce the influence of fluctuations with Fourier frequencies lower than the inverse of the modulation cycle length, which often are those that dominate. The predictions are confirmed experimentally
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| 4. |
- Axner, Ove, et al.
(författare)
-
Assessment of gas molar density by gas modulation refractometry : A review of its basic operating principles and extraordinary performance
- 2021
-
Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy. - : Elsevier B.V.. - 0584-8547 .- 1873-3565. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- A technique for high-precision and high-accuracy assessment of both gas molar (and number) density and pressure, Gas Modulation Refractometry (GAMOR), is presented. The technique achieves its properties by assessing refractivity as a shift of a directly measurable beat frequency by use of Fabry-Perot cavity (FPC) based refractometry utilizing the Pound-Drever-Hall laser locking technique. Conventional FPC-based refractometry is, however, often limited by fluctuations and drifts of the FPC. GAMOR remedies this by an additional utilization of a gas modulation methodology, built upon a repeated filling and evacuation of the measurement cavity together with an interpolation of the empty cavity responses. The procedure has demonstrated an ability to reduce the influence of drifts in a non-temperature stabilized dual-FPC (DFPC)-based refractometry system, when assessing pressure, by more than three orders of magnitude. When applied to a DFPC system with active temperature stabilization, it has demonstrated, for assessment of pressure of N2 at 4304 Pa at room temperature, which corresponds to a gas molar density of 1.7 × 10−6 mol/cm3, a sub-0.1 ppm precision (i.e. a resolution of 0.34 mPa). It is claimed that the ability to assess gas molar density is at least as good as so far has been demonstrated for pressure (i.e. for the molar density addressed, a resolution of at least 1.2 × 10−13 mol/cm3). It has recently been argued that the methodology should be capable of providing an accuracy that is in the low ppm range. These levels of precision and accuracy are unprecedented among laser-based techniques for detection of atomic and molecular species. Since the molar polarizability of He can be calculated by ab initio quantum mechanical calculations with sub-ppm accuracy, it can also be used as a primary or semi-primary standard of both gas molar (and number) density and pressure. © 2021 The Author(s)
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| 5. |
- 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
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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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| 6. |
- Foltynowicz, Aleksandra, 1981-, et al.
(författare)
-
Sub-Doppler Double-Resonance Spectroscopy of Methane Using a Frequency Comb Probe
- 2021
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 126:6
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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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| 7. |
- 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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| 8. |
- Forssén, Clayton, et al.
(författare)
-
A transportable refractometer for assessment of pressure in the kPa range with ppm level precision
- 2020
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Ingår i: Acta IMEKO. - : International Measurement Confederation (IMEKO). - 0237-028X .- 2221-870X. ; 9:5, s. 287-292
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Tidskriftsartikel (refereegranskat)abstract
- A transportable refractometer for assessment of kPa pressures with ppm level precision is presented. It is based on the GAs MOdulation Refractometry (GAMOR) methodology, making it resistant to fluctuations and drifts. At the National Metrology Institute at RISE, Sweden, the system assessed pressures in the 4.3 - 8.7 kPa range with sub-ppm precision (0.5 - 0.9 ppm). The system was thereafter disassembled, packed, and transported 1040 km to Umeå University, where it, after unpacking and reassembling, demonstrated a similar precision (0.8 - 2.1 ppm). This shows that the system can be disassembled, packed, transported, unpacked, and reassembled with virtually unchanged performance.
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| 9. |
- Forssén, Clayton, et al.
(författare)
-
An optical pascal in Sweden
- 2022
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Ingår i: Journal of Optics. - : IOP Publishing Ltd. - 2040-8978 .- 2040-8986. ; 24:3
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Tidskriftsartikel (refereegranskat)abstract
- By measuring the refractivity and the temperature of a gas, its pressure can be assessed from fundamental principles. The highest performing instruments are based on Fabry-Perot cavities where a laser is used to probe the frequency of a cavity mode, which is shifted in relation to the refractivity of the gas in the cavity. Recent activities have indicated that such systems can demonstrate an extended uncertainty in the 10 ppm (parts-per-million or 10-6) range. As a means to reduce the influence of various types of disturbances (primarily drifts and fluctuations) a methodology based on modulation, denoted gas modulation refractometry (GAMOR), has recently been developed. Systems based on this methodology are in general high-performance, e.g. they have demonstrated precision in the sub-ppm range, and they are sturdy. They can also be made autonomous, allowing for automated and unattended operation for virtually infinite periods of time. To a large degree, the development of such instruments depends on the access to modern photonic components, e.g. narrow line-width lasers, electro-and acousto-optic components, and various types of fiber components. This work highlights the role of such modern devices in GAMOR-based instrumentation and provides a review on the recent development of such instruments in Sweden that has been carried out in a close collaboration between a research institute and the Academy. It is shown that the use of state-of-the-art photonic devices allows sturdy, automated and miniaturized instrumentation that, for the benefit of industry, can serve as standards for pressure and provide fast, unattended, and calibration-free pressure assessments at a fraction of the present cost. © 2022 The Author(s).
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| 10. |
- Forssén, Clayton, et al.
(författare)
-
Circular comparison of conventional pressure standards using a transportable optical refractometer : preparation and transportation
- 2022
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Ingår i: 6th TC16 Conference on Pressure and Vacuum Measurement 2022, Together with the 24th TC3 Conference on the Measurement of Force, Mass and Torque, the 14th TC5 Conference on the Measurement of Hardness, and the 5th TC22 Conference on Vibration Measurement. - Budapest : International Measurement Confederation (IMEKO). - 9781713870227
-
Konferensbidrag (refereegranskat)abstract
- Using a transportable Fabry-Pérot cavity refractometer, a circular comparison of existing primary standards at several national metrology institutes is currently underway. This paper provides information about the refractometer, the preparation for the comparison, and the transportation procedure.
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| 11. |
- Forssén, Clayton, et al.
(författare)
-
Demonstration of a transportable Fabry–Pérot refractometer by a ring-type comparison of dead-weight pressure balances at four European national metrology institutes
- 2024
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 24:1
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Tidskriftsartikel (refereegranskat)abstract
- Fabry–Pérot-based refractometry has demonstrated the ability to assess gas pressure with high accuracy and has been prophesized to be able to realize the SI unit for pressure, the pascal, based on quantum calculations of the molar polarizabilities of gases. So far, the technology has mostly been limited to well-controlled laboratories. However, recently, an easy-to-use transportable refractometer has been constructed. Although its performance has previously been assessed under well-controlled laboratory conditions, to assess its ability to serve as an actually transportable system, a ring-type comparison addressing various well-characterized pressure balances in the 10–90 kPa range at several European national metrology institutes is presented in this work. It was found that the transportable refractometer is capable of being transported and swiftly set up to be operational with retained performance in a variety of environments. The system could also verify that the pressure balances used within the ring-type comparison agree with each other. These results constitute an important step toward broadening the application areas of FP-based refractometry technology and bringing it within reach of various types of stakeholders, not least within industry.
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| 12. |
- Forssén, Clayton, 1991-
(författare)
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Fabry-Pérot based refractometry : development of a transportable refractometer for assessment of gas pressure
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A unified description of physical phenomena through measurement science is one of the foundational pillars in a global society. The International System of Units (SI) is the most widely used system of units and since its redefinition in 2019, all units encompassed by it are based on fundamental physical constants. The units of the SI, such as the second, metre, and kilogram, are realized by the use of primary standards which are used, through calibration chains, to certify the accuracy of measuring devices in our society. Its redefinition enabled the realization of the SI-unit for pressure (pascal) in a novel way; instead of force per area (N/m2), it can alternatively be defined as an energy density (J/m3). Subsequently, this opened up for the use of optical realizations of the pascal (Pa). It has been prophesied that a possible means to do this is by assessing refractivity through the use of Fabry-Pérot (FP) refractometry. Although such instrumentation indeed can assess refractivity, it has unfortunately been found that they in practice are affected by various types of disturbances that aggravate assessments with the required uncertainty.This thesis describes the development of FP-based refractometers utilizing a novel measurement methodology, denoted gas modulation refractometry (GAMOR). By the use of rapid gas modulation and baseline interpolation, GAMOR has the ability to significantly reduce the influence of various types of disturbances, not least drifts and fluctuations. From this, two FP-based refractometers have been developed; one stationary, denoted the SOP, capable of assessing pressure with an uncertainty of [(10 mPa)2 + (10 × 10−6·P)2]1/2, and one transportable, denoted the TOP, with an uncertainty of [(16 mPa)2 + (28 × 10−6·P)2]1/2. Furthermore, it was shown that their mutual short-term precision is excellent, with a deviation of only 0.04 ppm when simultaneously assessing a pressure of 16 kPa.A major part of this thesis was devoted to the construction of the TOP and an investigation of its transportability and performance. It was used in a ring comparison with various pressure standards at four European national metrology institutes. It was concluded that, despite being transported, the performance remained virtually unchanged, and that, in the 10 – 90 kPa range, all the standards agreed within their uncertainties.These results indicate that FP-based refractometers utilizing the GAMOR methodology have the potential to act as transportable standards based on fundamental physical constants and paves the way for future research within the field.
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| 13. |
- Forssén, Clayton, et al.
(författare)
-
Fabry-Perot-cavity-based refractometry without influence of mirror penetration depth
- 2021
-
Ingår i: Journal of Vacuum Science and Technology B. - : AVS Science and Technology Society. - 2166-2746 .- 2166-2754. ; 39:6
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Tidskriftsartikel (refereegranskat)abstract
- Assessments of refractivity in a Fabry-Perot (FP) cavity by refractometry often encompass a step in which the penetration depth of the light into the mirrors is estimated to correct for the fraction of the cavity length into which no gas can penetrate. However, as it is currently carried out, this procedure is not always coherently performed. Here, we discuss a common pitfall that can be a reason for this and provide a recipe on how to perform FP-cavity-based refractometry without any influence of mirror penetration depth. © 2021 Author(s).
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| 14. |
- Forssén, Clayton, et al.
(författare)
-
The short-term performances of two independent gas modulated refractometers for pressure assessments
- 2021
-
Ingår i: Sensors. - : MDPI. - 1424-8220. ; 21:18
-
Tidskriftsartikel (refereegranskat)abstract
- Refractometry is a powerful technique for pressure assessments that, due to the recent redefinition of the SI system, also offers a new route to realizing the SI unit of pressure, the Pascal. Gas modulation refractometry (GAMOR) is a methodology that has demonstrated an outstanding ability to mitigate the influences of drifts and fluctuations, leading to long-term precision in the 10−7 region. However, its short-term performance, which is of importance for a variety of applications, has not yet been scrutinized. To assess this, we investigated the short-term performance (in terms of precision) of two similar, but independent, dual Fabry–Perot cavity refractometers utilizing the GAMOR methodology. Both systems assessed the same pressure produced by a dead weight piston gauge. That way, their short-term responses were assessed without being compromised by any pressure fluctuations produced by the piston gauge or the gas delivery system. We found that the two refractometer systems have a significantly higher degree of concordance (in the 10−8 range at 1 s) than what either of them has with the piston gauge. This shows that the refractometry systems under scrutiny are capable of assessing rapidly varying pressures (with bandwidths up to 2 Hz) with precision in the 10−8 range. © 2021 by the authors.
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| 15. |
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| 16. |
- Germann, Matthias, et al.
(författare)
-
Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range : experimental line list and improved MARVEL analysis
- 2024
-
Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer. - : Elsevier. - 0022-4073 .- 1879-1352. ; 312
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Tidskriftsartikel (refereegranskat)abstract
- We use optical frequency comb Fourier transform spectroscopy to record high-resolution, low-pressure, room-temperature spectra of formaldehyde (H212C16O) in the range of 1250 to 1390 cm−1. Through line-by-line fitting, we retrieve line positions and intensities of 747 rovibrational transitions: 558 from the ν6 band, 129 from the ν4 band, and 14 from the ν3 band, as well as 46 from four different hot bands. We incorporate the accurate and precise line positions (0.4 MHz median uncertainty) into the MARVEL (measured active vibration-rotation energy levels) analysis of the H2CO spectrum. This increases the number of MARVEL-predicted energy levels by 82 and of rovibrational transitions by 5382, and substantially reduces uncertainties of MARVEL-derived H2CO energy levels over a large range: from pure rotational levels below 200 cm−1 up to multiply excited vibrational levels at 6000 cm−1. This work is an important step toward filling the gaps in formaldehyde data in the HITRAN database.
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| 17. |
- Germann, Matthias, et al.
(författare)
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Precision frequency comb spectroscopy in the 8 µm range
- 2023
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Ingår i: CLEO 2023. - : Optical Society of America. - 9781957171258
-
Konferensbidrag (refereegranskat)abstract
- We use Fourier transform spectroscopy based on a compact difference frequency generation comb source emitting around 8 μm to record broadband high-resolution spectra of molecules relevant to astrophysics and environmental monitoring. From the spectra we obtain line lists with sub-MHz accuracy, an order of magnitude better than previously available, and use them to refine theoretical models of these molecules. Here we report results for formaldehyde, for which the 8 μm range is missing in HITRAN.
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| 18. |
- Hjältén, Adrian, 1988-, et al.
(författare)
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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
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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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| 19. |
- Lu, Chuang, et al.
(författare)
-
Robust and High-Speed Cavity-Enhanced Vernier Spectrometer
- 2021
-
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
-
Konferensbidrag (refereegranskat)abstract
- Sensitive in situ detection of multiple atmospheric species at fast acquisition rates is needed for environmental monitoring. For field applications, robust and compact design is also demanded. Continuous-filtering Vernier spectroscopy (CF-VS) [1] is a cavity-enhanced frequency-comb-based technique that provides broad spectral bandwidth and high absorption sensitivity in short acquisition times. In CF-VS, groups of comb lines (Vernier orders, VOs) are transmitted through the cavity when its free spectral range (FSR) is slightly detuned from the comb repetition rate ( f rep ) and continuously swept across the broadband laser spectrum (by scanning the FSR). In previous implementations [1] - [3] , a diffraction grating rotating on a galvo scanner was used to image one VO on the detector during the spectral scan, limiting the acquisition rates to 20 Hz. Moreover, high-bandwidth stabilization was needed to synchronize the scans of the galvo and the cavity FSR. Here we present an improved design of CF-VS based on a compact Er:fiber laser and a moving aperture that follows and selects one VO. This removes the requirement of tight active stabilization and enables faster acquisition rates.
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| 20. |
- Lu, Chuang, et al.
(författare)
-
Robust, fast and sensitive near-infrared continuous-filtering Vernier spectrometer
- 2021
-
Ingår i: Optics Express. - : The Optical Society. - 1094-4087. ; 29:19, s. 30155-30167
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new design of a robust cavity-enhanced frequency comb-based spectrometer operating under the continuous-filtering Vernier principle. The spectrometer is based on a compact femtosecond Er-doped fiber laser, a medium finesse cavity, a diffraction grating, a custom-made moving aperture, and two photodetectors. The new design removes the requirement for high-bandwidth active stabilization present in the previous implementations of the technique, and allows scan rates up to 100 Hz. We demonstrate the spectrometer performance over a wide spectral range by detecting CO2 around 1575 nm (1.7 THz bandwidth and 6 GHz resolution) and CH4 around 1650 nm (2.7 THz bandwidth and 13 GHz resolution). We achieve absorption sensitivity of 5 × 10−9 cm-1 Hz-1/2 at 1575 nm, and 1 × 10−7 cm-1 Hz-1/2 cm-1 at 1650 nm. We discuss the influence of the scanning speed above the adiabatic limit on the amplitude of the absorption signal.
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| 21. |
- Rubin, T., et al.
(författare)
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'Quantum-based realizations of the pascal' status and progress of the empir-project: quantumpascal
- 2022
-
Ingår i: 6th TC16 Conference on Pressure and Vacuum Measurement 2022, Together with the 24th TC3 Conference on the Measurement of Force, Mass and Torque, the 14th TC5 Conference on the Measurement of Hardness, and the 5th TC22 Conference on Vibration Measurement. - : International Measurement Confederation (IMEKO). - 9781713870227
-
Konferensbidrag (refereegranskat)abstract
- The QuantumPascal (QP) project combines the capabilities of 12 European institutions to enable traceable pressure measurements utilizing quantum-based methods that evaluate the number density instead of force per area to target the wide pressure range between 1 Pa and 3 MPa. This article summarizes the goals and results since the project start in June 2019.
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| 22. |
- Rubin, T., et al.
(författare)
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Thermodynamic effects in a gas modulated Invar-based dual Fabry-Pérot cavity refractometer
- 2022
-
Ingår i: Metrologia. - : IOP Publishing Ltd. - 0026-1394 .- 1681-7575. ; 59:3
-
Tidskriftsartikel (refereegranskat)abstract
- By measuring the refractivity and the temperature of a gas, its pressure can be assessed from fundamental principles. The highest performing instruments are based on Fabry-Perot cavities (FPC). Gas modulation refractometry (GAMOR) is a methodology that has the ability to reduce the influence of disturbances to such an extent that high-precision (sub-parts-per-million) assessments of pressure can be made by the use of FPCs of Invar. To allow for high accuracy assessments, it is of importance to assess the uncertainty contribution from the thermodynamic effects that are associated with the gas filling and emptying of the cavity (pV-work). This paper presents a detailed scrutiny of the influence of the gas exchange process on the assessment of gas temperature on an Invar-based dual-FPC (DFPC) instrumentation. It is shown that by virtue of a combination of a number of carefully selected design entities (a small cavity volume with a bore radius of 3 mm, a spacer material with high heat capacitance, large thermal conductivity, and no regions that are connected with low thermal conductance, i.e. no heat islands, and a continuous assessment of temperature of the cavity spacer) the system is not significantly affected by pV-work. Simulations show that 10 s after the filling all temperature gradients in the system are well into the sub-mK range. Experiments support that refractivity assessments initiated after 40 s are not significantly affected by the pV-work. The analysis given in this work indicates that an upper limit for the influence of pV-work on the Invar-based DFPC system using 100 s long gas modulation cycles is 0.5 mK/100 kPa (or 1.8 ppm/100 kPa). Consequently, thermodynamic effects will not be a limiting factor when the Invar-based DFPC GAMOR system is used for assessments of pressure or as a primary pressure standard up to atmospheric pressures.
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| 23. |
- Rubin, T., et al.
(författare)
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Thermodynamic effects in a gas modulated Invar-based dual Fabry-Pérot cavity refractometer addressing 100 kpa of nitrogen
- 2022
-
Ingår i: 6th TC16 Conference on Pressure and Vacuum Measurement 2022, Together with the 24th TC3 Conference on the Measurement of Force, Mass and Torque, the 14th TC5 Conference on the Measurement of Hardness, and the 5th TC22 Conference on Vibration Measurement. - : International Measurement Confederation (IMEKO). - 9781713870227
-
Konferensbidrag (refereegranskat)abstract
- An Invar-based dual Fabry-Pérot cavity refractometer used for assessments of pressure by the gas modulation refractometry (GAMOR) methodology has been scrutinized with respect to the influence of thermodynamic effects (pV-work) that originates from the gas exchange process when 100 kPa of nitrogen is addressed. It is shown that the actual temperature variation of the cavity spacer solely is a fraction of the previously assessed upper limits (0.5 mK/100 kPa), limited to sub-parts-per-million (ppm) levels. This finding additionally supports the conclusion that the thermodynamic effects will not be a limiting factor when the system is used for assessments of pressure.
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| 24. |
- Silander, Isak, 1980-, et al.
(författare)
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An invar-based fabry-perot cavity refractometer with a gallium fixed-point cell for assessment of pressure
- 2020
-
Ingår i: Acta IMEKO. - : International Measurement Confederation (IMEKO). - 0237-028X .- 2221-870X. ; 9:5, s. 293-298
-
Tidskriftsartikel (refereegranskat)abstract
- An Invar-based Fabry-Perot cavity refractometer equipped with an automated, miniaturized gallium fixed-point cell for assessment of pressure is presented. The use of an Invar cavity spacer has previously demonstrated pressure assessments with sub-0.1 ppm precision. The fixed-point cell, whose design and implementation are presented here, provides a reference for temperature assessment of the gas inside the cavity with an uncertainty of 4 ppm. This opens up for a self-contained system for realization of the Pascal with an accuracy in the low ppm range. This is an important step towards disseminating the Pascal through fundamental principles.
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| 25. |
- Silander, Isak, et al.
(författare)
-
AN INVAR-BASED FABRY-PEROT CAVITY REFRACTOMETER WITH AGALLIUM FIXED-POINT CELL FOR ASSESSMENT OF PRESSURE
- 2020
-
Ingår i: Acta IMEKO. - : IMEKO International Measurement Confederation. - 2221-870X. ; :5, s. 293-298
-
Tidskriftsartikel (refereegranskat)abstract
- An Invar-based Fabry-Perot cavity refractometer equipped with an automated, miniaturized galliumfixed-point cell for assessment of pressure is presented. The use of an Invar cavity spacer has previously demonstrated pressure assessments with sub-0.1 ppm precision. The fixed-point cell, whose design and implementation are presented here, provides a reference for temperature assessment of the gas inside the cavity with an uncertainty of 4 ppm. This opens up for a self-contained system for realization of the Pascal with an accuracy in the low ppm range. This is an important step towards disseminating the Pascal through fundamental principles.
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| 26. |
- Silander, Isak, 1980-, et al.
(författare)
-
In situ determination of the penetration depth of mirrors in Fabry-Perot refractometers and its influence on assessment of refractivity and pressure
- 2022
-
Ingår i: Optics Express. - : Optica Publishing Group (formerly OSA). - 1094-4087. ; 30:14, s. 25891-25906
-
Tidskriftsartikel (refereegranskat)abstract
- A procedure is presented for in situ determination of the frequency penetration depth of coated mirrors in Fabry-Perot (FP) based refractometers and its influence on the assessment of refractivity and pressure. It is based on assessments of the absolute frequency of the laser and the free spectral range of the cavity. The procedure is demonstrated on an Invar-based FP cavity system with high-reflection mirrors working at 1.55 µm. The influence was assessed with such a low uncertainty that it does not significantly contribute to the uncertainties (k = 2) in the assessment of refractivity (<8 × 10−13) or pressure of nitrogen (<0.3 mPa).
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| 27. |
- Silander, Isak, 1980-, et al.
(författare)
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Invar-based refractometer for pressure assessments
- 2020
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Ingår i: Optics Letters. - : OSA - The Optical Society. - 0146-9592 .- 1539-4794. ; 45:9, s. 2652-2655
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology that can mitigate fluctuations and drifts in refractometry. This can open up for the use of non-conventional cavity spacer materials. In this paper, we report a dual-cavity system based on Invar that shows better precision for assessment of pressure than a similar system based on Zerodur. This refractometer shows for empty cavity measurements, up to 104 s, a white noise response (for N2) of 3 mPa s1=2. At 4303 Pa, the system has a minimum Allan deviation of 0.34 mPa (0.08 ppm) and a long-term stability (24 h) of 0.7 mPa. This shows that the GAMOR methodology allows for the use of alternative cavity materials.
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| 28. |
- Silander, Isak, 1980-, et al.
(författare)
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Optical realization of the pascal—Characterization of two gas modulated refractometers
- 2021
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Ingår i: Journal of Vacuum Science and Technology B. - : AVS Science and Technology Society. - 2166-2746 .- 2166-2754. ; 39:4
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Tidskriftsartikel (refereegranskat)abstract
- By measuring the refractivity and the temperature of a gas, its pressure can be calculated from fundamental principles. The most sensitive instruments are currently based on Fabry-Perot cavities where a laser is used to probe the frequency of a cavity mode. However, for best accuracy, the realization of such systems requires exceptional mechanical stability. Gas modulation refractometry (GAMOR) has previously demonstrated an impressive ability to mitigate the influence of fluctuations and drifts whereby it can provide high-precision (sub-ppm, i.e., sub-parts-per-million or sub-10−6) assessment of gas refractivity and pressure. In this work, two independent GAMOR-based refractometers are individually characterized, compared to each other, and finally compared to a calibrated dead weight piston gauge with respect to their abilities to assess pressure in the 4-25 kPa range. The first system, referred to as the stationary optical pascal (SOP), uses a miniature fixed point gallium cell to measure the temperature. The second system, denoted the transportable optical pascal (TOP), relies on calibrated Pt-100 sensors. The expanded uncertainty for assessment of pressure (k=2) was estimated to, for the SOP and TOP, [(10mPa)2+(10×10−6P)2]1/2 and [(16mPa)2+(28×10−6P)2]1/2, respectively. While the uncertainty of the SOP is mainly limited by the uncertainty in the molar polarizability of nitrogen (8 ppm), the uncertainty of the TOP is dominated by the temperature assessment (26 ppm). To verify the long-term stability, the systems were compared to each other over a period of 5 months. It was found that all measurements fell within the estimated expanded uncertainty (k=2) for comparative measurements (27 ppm). This verified that the estimated error budget for the uncorrelated errors holds over this extensive period of time. © 2021 Author(s).
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| 29. |
- Silander, Isak, et al.
(författare)
-
Realization of the pascal based on argon using a Fabry–Perot refractometer
- 2024
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Ingår i: Optics Letters. - : Optica Publishing Group (formerly OSA). - 0146-9592 .- 1539-4794. ; 49:12, s. 3296-3299
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Tidskriftsartikel (refereegranskat)abstract
- Based on a recent experimental determination of the static polarizability and a first-principle calculation of the frequency-dependent dipole polarizability of argon, this work presents, by using a Fabry–Perot refractometer operated at 1550 nm, a realization of the SI unit of pressure, the pascal, for pressures up to 100 kPa, with an uncertainty of [(1.0 mPa)2 + (5.8 × 10−6 P)2 + (26 × 10−12P2)2]1/2. The work also presents a value of the molar polarizability of N2 at 1550 nm and 302.9146 K of 4.396572(26) × 10−6 m3/mol, which agrees well with previously determined ones.
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| 30. |
- 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
-
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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| 31. |
- 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
-
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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| 32. |
- Silva de Oliveira, Vinicius, et al.
(författare)
-
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
-
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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| 33. |
- Silva de Oliveira, Vinicius, et al.
(författare)
-
Sub-doppler optical-optical double-resonance spectroscopy of methane using a frequency comb probe
- 2021
-
Ingår i: OSA Optical Sensors and Sensing Congress 2021 (AIS, FTS, HISE, SENSORS, ES). - : Optical Society of America. - 9781557528209
-
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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| 34. |
- Silva de Oliveira, Vinicius, et al.
(författare)
-
Sub-Doppler optical-optical double-resonance spectroscopy using a cavity-enhanced frequency comb probe
- 2024
-
Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 15:1
-
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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| 35. |
- Vieira, Francisco Senna, et al.
(författare)
-
Continuous-filtering Vernier spectrometer with improved design and performance
- 2020
-
Ingår i: Optics InfoBase Conference Papers. - : The Optical Society. - 9781557528209
-
Konferensbidrag (refereegranskat)abstract
- We present a robust cavity-enhanced comb-based spectrometer with a 6.6 GHz resolution and 60 Hz acquisition rate, based on the continuous-filtering Vernier principle, a fixed diffraction grating, a custom-made chopper wheel, and a low-bandwidth comb-cavity stabilization scheme. We measure a CO2 spectrum with 5 x 10-8 cm-1 sensitivity in 17 ms.
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| 36. |
- Vieira, Francisco Senna, et al.
(författare)
-
Robust, Fast and Sensitive Near-Infrared Continuous-Filtering Vernier Spectrometer
- 2020
-
Ingår i: 2020 Conference on Lasers and Electro-Optics (CLEO). - : IEEE. - 9781943580767 ; , s. 1-2
-
Konferensbidrag (refereegranskat)abstract
- We present a new robust approach to cavity-enhanced comb spectroscopy based on Vernier filtering, a fixed diffraction grating, custom-made chopper wheel, and a low bandwidth comb-cavity stabilization scheme. We measure a CO2 spectrum with a few GHz resolution and 5 x 10-8 cm-1 sensitivity in 9.4 ms.
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| 37. |
- Zakrisson, Johan, et al.
(författare)
-
Effect of absorption of laser light in mirrors on Fabry-Pérot based refractometry
- 2024
-
Ingår i: Optics Express. - : Optical Society of America. - 1094-4087. ; 32:14, s. 24656-24678
-
Tidskriftsartikel (refereegranskat)abstract
- This work models and experimentally assesses the influence of absorption of laser light in mirrors in Fabry-Pérot based refractometers used for realization of pressure. Model parameters are assessed by experimental characterizations. Characterizations of two refractometers agree well with the predictions of the model. It is shown that, when pressures are assessed in the viscous region, the absorption of laser light in mirrors will give rise to a small alteration in the proportional response and a pressure-independent offset, where the latter is significant for He but considerably smaller for Ar and N2.
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| 38. |
- Zakrisson, Johan, et al.
(författare)
-
Effect of absorption of laser light in mirrors on Fabry-Pérot based refractometry
- 2024
-
Ingår i: Optics Express. - : Optica Publishing Group (formerly OSA). - 1094-4087. ; 32:14, s. 24656-24678
-
Tidskriftsartikel (refereegranskat)abstract
- This work models and experimentally assesses the influence of absorption of laser light in mirrors in Fabry-Pérot based refractometers used for realization of pressure. Model parameters are assessed by experimental characterizations. Characterizations of two refractometers agree well with the predictions of the model. It is shown that, when pressures are assessed in the viscous region, the absorption of laser light in mirrors will give rise to a small alteration in the proportional response and a pressure-independent offset, where the latter is significant for He but considerably smaller for Ar and N2
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| 39. |
- Zakrisson, Johan, et al.
(författare)
-
Procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry
- 2024
-
Ingår i: Optics Express. - : Optica Publishing Group (formerly OSA). - 1094-4087. ; 32:3, s. 3959-3973
-
Tidskriftsartikel (refereegranskat)abstract
- A procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry that does not require access to laser frequency measuring instrumentation is presented. It requires a previously well-characterized system regarding mirror phase shifts, Gouy phase, and mode number, and is based on the fact that the assessed refractivity should not change when mode jumps take place. It is demonstrated that the procedure is capable of assessing mode frequencies with an uncertainty of 30 MHz, which, when assessing pressure of nitrogen, corresponds to an uncertainty of 0.3 mPa.
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| 40. |
- Zakrisson, Johan, et al.
(författare)
-
Procedure for robust assessment of cavity deformation in Fabry-Pérot based refractometers
- 2020
-
Ingår i: Journal of Vacuum Science and Technology B. - : AVS Science and Technology Society. - 2166-2746 .- 2166-2754. ; 38:5
-
Tidskriftsartikel (refereegranskat)abstract
- A novel procedure for a robust assessment of cavity deformation in Fabry-Pérot (FP) refractometers is presented. It is based on scrutinizing the difference between two pressures: one assessed by the uncharacterized refractometer and the other provided by an external pressure reference system, at a series of set pressures for two gases with dissimilar refractivity (here, He and N 2). By fitting linear functions to these responses and extracting their slopes, it is possible to construct two physical entities of importance: one representing the cavity deformation and the other comprising a combination of the systematic errors of a multitude of physical entities, viz., those of the assessed temperature, the assessed or estimated penetration depth of the mirror, the molar polarizabilities, and the set pressure. This provides a robust assessment of cavity deformation with small amounts of uncertainties. A thorough mathematical description of the procedure is presented that serves as a basis for the evaluation of the basic properties and features of the procedure. The analysis indicates that the cavity deformation assessments are independent of systematic errors in both the reference pressure and the assessment of gas temperature and when the gas modulation refractometry methodology is used that they are insensitive to gas leakages and outgassing into the system. It also shows that when a high-precision (sub-ppm) refractometer is characterized according to the procedure, when high purity gases are used, the uncertainty in the deformation contributes to the uncertainty in the assessment of pressure of N 2 with solely a fraction (13%) of the uncertainty of its molar polarizability, presently to a level of a few ppm. This implies, in practice, that cavity deformation is no longer a limiting factor in FP-based refractometer assessments of pressure of N 2. © 2020 Author(s).
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| 41. |
- Zakrisson, Johan, et al.
(författare)
-
Simulation of pressure-induced cavity deformation : the 18SIB04 Quantumpascal EMPIR project
- 2020
-
Ingår i: Acta IMEKO. - 0237-028X .- 2221-870X. ; 9:5, s. 281-286
-
Tidskriftsartikel (refereegranskat)abstract
- The 18SIB04 QuantumPascal EMPIR project aims for development of photon-based standards that can replace primary standards of the SI unit of pressure, the Pascal. In this project, four partners simulated the pressure-induced deformation of a given Fabry-Pérot cavity, using various versions of two types of software, COMSOL Multiphysics® and ANSYS Workbench. It was demonstrated that, for a given geometry and set of material parameters, simulations of the deformation could be performed by the various partners with such small discrepancies that methodological mistakes of the simulation procedures will solely contribute to a sub-ppm uncertainty in the assessments of refractivity of N2.
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| 42. |
- Zelan, Martin, et al.
(författare)
-
Recent advances in Fabry-Péro-based refractometry utilizing gas modulation for assessment of pressure
- 2020
-
Ingår i: Acta IMEKO. - : International Measurement Confederation (IMEKO). - 0237-028X .- 2221-870X. ; 9:5, s. 299-304
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology that can mitigate the influence of fluctuations and drifts in Fabry-Pérot cavity–based refractometry. This paper presents a thorough description of its principles, what it enables, and its applicability. An overview of the latest results is presented, including the realization of a system based upon a cavity spacer made of Invar that allows for detection of N2 with sub-ppm precision, and a characterization procedure that allows for assessment of N2 with an accuracy at low-ppm levels.
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| 43. |
- Zelan, Martin, et al.
(författare)
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RECENT ADVANCES IN FABRY-PEROT-BASED REFRACTOMETRYUTILIZING GAS MODULATION FOR ASSESSMENT OF PRESSURE
- 2020
-
Ingår i: Acta IMEKO. - : IMEKO International Measurement Confederation. - 2221-870X. ; 9:5, s. 299-304
-
Tidskriftsartikel (refereegranskat)abstract
- Gas modulation refractometry (GAMOR) is a methodology that can mitigate the influence off luctuations and drifts in Fabry-Pérot cavity–based refractometry. This paper presents a thorough description of its principles, what it enables, and its applicability. An overview of the latest results is presented, including the realization of a system based upon a cavity spacer made of Invar that allows for detection of N2 with sub-ppm precision, and a characterization procedure that allows for assessment of N2 with an accuracy at low-ppm levels.
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