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  • 1.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ehlers, Patrick
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Junyang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    NICE-OHMS – frequency modulation cavity-enhanced spectroscopy: principles and performance2014Ingår i: Cavity-Enhanced Spectroscopy and Sensing / [ed] Gianluca Gagliardi and Hans-Peter Loock, Berlin: Springer Berlin/Heidelberg, 2014, s. 221-251Kapitel i bok, del av antologi (Refereegranskat)
    Abstract [en]

    Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a sensitive technique for detection of molecular species in gas phase. It is based on a combination of frequency modulation for reduction of noise and cavity enhancement for prolongation of the interaction length between the light and a sample. It is capable of both Doppler-broadened and sub-Doppler detection with absorption sensitivity down to the 10−12 and 10−14 Hz−1/2 cm−1 range, respectively. This chapter provides a thorough description of the basic principles and the performance of the technique.

  • 2.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ehlers, Patrick
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz-Matyba, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Junyang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    NICE-OHMS – Frequency modulation cavity-enhanced spectroscopy: principles and performanceManuskript (preprint) (Övrigt vetenskapligt)
  • 3.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ehlers, Patrick
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ma, Weiguang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Noise-immune cavity-enhanced analytical atomic spectrometry — NICE-AAS: a technique for detection of elements down to zeptogram amounts2014Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy, ISSN 0584-8547, E-ISSN 1873-3565, Vol. 100, s. 211-235Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is a powerful technique for detection of molecular compounds in gas phase that is based on a combination of two important concepts: frequency modulation spectroscopy (FMS) for reduction of noise, and cavity enhancement, for prolongation of the interaction length between the light and the sample. Due to its unique properties, it has demonstrated unparalleled detection sensitivity when it comes to detection of molecular constituents in the gas phase. However, despite these, it has so far not been used for detection of atoms, i.e. for elemental analysis. The present work presents an assessment of the expected performance of Doppler-broadened (Db) NICE-OHMS for analytical atomic spectrometry, then referred to as noise-immune cavity-enhanced analytical atomic spectrometry (NICE-AAS). After a description of the basic principles of Db-NICE-OHMS, the modulation and detection conditions for optimum performance are identified. Based on a previous demonstrated detection sensitivity of Db-NICE-OHMS of 5×10−12 cm−1 Hz−1∕2 (corresponding to a single-pass absorbance of 7×10−11 over 10 s), the expected limits of detection (LODs) of Hg and Na by NICE-AAS are estimated. Hg is assumed to be detected in gas phase directly while Na is considered to be atomized in a graphite furnace (GF) prior to detection. It is shown that in the absence of spectral interferences, contaminated sample compartments, and optical saturation, it should be feasible to detect Hg down to 10 zg/cm3 (10 fg/m3 or 10-5 ng/m3), which corresponds to 25 atoms/cm3, and Na down to 0.5 zg (zg = zeptogram = 10-21 g), representing 50 zg/mL (parts-per-sextillion, pps, 1:1021) in liquid solution (assuming a sample of 10 µL) or solely 15 atoms injected into the GF, respectively. These LODs are several orders of magnitude lower (better) than any previous laser-based absorption technique previously has demonstrated under atmospheric pressure conditions. It is prophesied that NICE-AAS could provide such high detection sensitivity that the instrumentation should not, by itself, be the limiting factor of an assessment of elemental abundance; the accuracy of an assessment would then instead be limited by concomitant species, e.g. originating from the handling procedures of the sample or the environment.

  • 4.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Ability of gas modulation to reduce the pickup of drifts in refractometry2021Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 38, nr 8, s. 2419-2436Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 5.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Ability of gas modulation to reduce the pickup of fluctuations in refractometry2020Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 37, nr 7, s. 1956-1965Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

  • 6.
    Axner, Ove
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Assessment of gas molar density by gas modulation refractometry: A review of its basic operating principles and extraordinary performance2021Ingår i: Spectrochimica Acta Part B - Atomic Spectroscopy, ISSN 0584-8547, E-ISSN 1873-3565, Vol. 179, artikel-id 106121Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    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.

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  • 7.
    Ehlers, Patrick
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Use of etalon-immune distances to reduce the influence of background signals in frequency-modulation spectroscopy and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy2014Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 31, nr 12, s. 2938-2945Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The detection sensitivity of phase-modulated techniques such as frequency-modulation spectroscopy (FMS) and noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) is often limited by etalon background signals. It has previously been shown that the impact of etalons can be reduced by the use of etalon-immune distances (EIDs), i.e., by separating the surfaces that give rise to etalons by a distance of q. L-m, where L-m is given by c/2n nu(m), where, in turn, n and nu(m) are the index of refraction between the components that make up the etalon (thus most often that of air) and the modulation frequency, respectively, and where q is an integer (i.e., 1, 2, 3,.) or half-integer (i.e., 1/2, 1, 3/2,.) for the dispersion and absorption modes of detection, respectively. An etalon created by surfaces separated by an EID will evade detection and thereby not contribute to any background signal. The concept of EIDs in FMS and NICE-OHMS is in this work demonstrated, scrutinized, and discussed in some detail. It is shown that the influence of EIDs on the absorption and dispersion modes of detection is significantly different; signals detected at the dispersion phase are considerably less sensitive to deviations from exact EID conditions than those detected at the absorption phase. For example, the FM background signal from an etalon whose length deviates from an EID by 2.5% of L-m (e.g., by 1 cm for an L-m of 40 cm), detected in dispersion, is only 9% of that in absorption. This makes the former mode of detection the preferred one whenever a sturdy immunity against etalons is needed or when optical components with parallel surfaces (e.g., lenses, polarizers, or beam splitters) are used. The impact of the concept of EIDs on NICE-OHMS is demonstrated by the use of Allan-Werle plots.

  • 8.
    Ehlers, Patrick
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry: optimum modulation and demodulation conditions, cavity length, and modulation order2014Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 31, nr 9, s. 2051-2060Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (Db-NICE-OHMS) has been scrutinized with respect to modulation and demodulation conditions (encompassing the modulation frequency,nu(m), the modulation index, beta, and the detection phase, theta), the cavity length, L, and the modulation order, k (defined as nu(m)/nu(FSR), where nu(FSR) is the free-spectral range of the cavity), primarily in the Doppler limit but also for two specific situations in the Voigt regime (for equal Doppler and homogeneous width and for purely Lorentzian broadened transitions), both in the absence and presence of optical saturation (the latter for the case in which the homogeneous broadening is smaller than the modulation frequency). It is found that, for a system with a given cavity length, the optimum conditions (i.e., those that produce the largest NICE-OHMS signal) for an unsaturated transition in the Doppler limit comprise nu(m)/Gamma(D) = 1.6 (where Gamma(D) is the half-width at half-maximum of the Doppler width of the transition), beta = 1.3, and theta = 0.78 pi. It is also found that the maximum is rather broad; the signal takes 95% of its maximum value for modulation frequencies in the entire 0.4 less than or similar to nu(m)/Gamma(D) less than or similar to 2.4 range. When optical saturation sets in, theta shifts toward the dispersion phase. The optimum conditions encompass k > 1 whenever L > 0.35L(D) and 2.6L(D) for the dispersion and absorption modes of detection, respectively [where L-D is a characteristic length given by c/(2 Gamma(D))]. Similar conditions are found under pressure broadened conditions. 

  • 9.
    Ehlers, Patrick
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Junyang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrumentation for Doppler-broadened detection in the 10-12 cm-1 Hz-1/2 region2012Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 29, nr 6, s. 1305-1315Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry (FL-NICE-OHMS) system for white-noise-limited Doppler-broadened detection down to 5.6 x 10(-12) cm(-1) Hz(-1/2) is demonstrated. The system is based on a previous FL-NICE-OHMS instrumentation in which the locking of the laser frequency to a cavity mode has been improved by the use of an acousto-optic modulator (AOM) and provision of a more stable environment by the employment of a noise-isolating enclosed double-layer table, a temperature regulation of the laboratory, and an ultra-high-vacuum (UHV) gas system. White-noise behavior up to 10 s provides the instrument with a minimum detectable on-resonance absorbance per unit length of 1.8 x 10(-12) cm(-1) and a relative single-pass absorption (Delta I/I) of 7.2 x 10(-11). The system was applied to detection of acetylene on a transition at 1531.588 nm, yielding a detection sensitivity of C2H2 in atmospheric pressure gas of 4 ppt (measured over 10 s). (C) 2012 Optical Society of America

  • 10.
    Ehlers, Patrick
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Junyang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry incorporating an optical circulator2014Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 39, nr 2, s. 279-282Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To reduce the complexity of fiber-laser-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry, a system incorporating a fiber-coupled optical circulator to deflect the cavity-reflected light for laser stabilization has been realized. Detection near the shot-noise limit has been demonstrated for both Doppler-broadened and sub-Doppler signals, yielding a lowest detectable absorption and optical phase shift of 2.2 x 10(-12) cm(-1) and 4.0 x 10(-12) cm(-1), respectively, both for a 10 s integration time, where the former corresponds to a detection limit of C2H2 of 5 ppt. (C) 2014 Optical Society of America

  • 11.
    Ehlers, Patrick
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Junyang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler broadened NICE-OHMS beyond the triplet formalism: assessment of optimum modulation index2014Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 31, nr 7, s. 1499-1507Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The dependence of Doppler broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) on the modulation index, beta, has been investigated experimentally on C2H2 and CO2, both in the absence and the presence of optical saturation. It is shown that the maximum signals are obtained for beta that produce more than one pair of sidebands: in the Doppler limit and for the prevailing conditions (unsaturated transition and the pertinent modulation frequency and Doppler widths) around 1 and 1.4 for the dispersion and absorption detection phases, respectively. The results verify predictions given in an accompanying work. It is also shown that there is no substantial broadening of the NICE-OHMS signal for beta < 1. The use of beta of unity has yielded a Db-NICE-OHMS detection sensitivity of 4.9 x 10(-12) cm(-1) Hz(-1/2), which is the lowest (best) value so far achieved for NICE-OHMS based on a tunable laser. The number of sidebands that needs to be included in fits of the line-shape function to obtain good accuracy has been assessed. It is concluded that it is enough to consider three pairs of sidebands whenever the systematic errors in a concentration assessment should be below 1% when beta < 2 are used and <1 parts per thousand for beta < 1.5.

  • 12.
    Foltynowicz, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Université de Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251, Rennes, France.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboń, Grzegorz
    Laser and Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Martynkien, Tadeusz
    Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wroclaw, Poland.
    Mergo, Paweł
    Laboratory of Optical Fiber Technology, Maria Curie-Sklodowska University, Lublin, Poland.
    Lehmann, Kevin K.
    Departments of Chemistry and Physics, University of Virginia, VA, Charlottesville, United States.
    Measurement and assignment of double-resonance transitions to the 8900-9100- cm-1 levels of methane2021Ingår i: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 103, nr 2, artikel-id 022810Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 13.
    Foltynowicz, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Université de Rennes, CNRS, IPR (Institut de Physique de Rennes)-UMR 6251, Rennes, France.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboń, Grzegorz
    Laser and Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Martynkien, Tadeusz
    Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wroclaw, Poland.
    Mergo, Paweł
    Laboratory of Optical Fiber Technology, Maria Curie-Sklodowska University, Lublin, Poland.
    Lehmann, Kevin K.
    Departments of Chemistry and Physics, University of Virginia, VA, Charlottesville, United States.
    Sub-Doppler Double-Resonance Spectroscopy of Methane Using a Frequency Comb Probe2021Ingår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 126, nr 6, artikel-id 063001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 14.
    Foltynowicz, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Univ Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251, Rennes, France.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboń, Grzegorz
    Laser and Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wroclaw, Poland.
    Martynkien, Tadeusz
    Faculty of Fundamental Problems of Technology, Wrocław University of Science and Technology, Wroclaw, Poland.
    Mergo, Paweł
    Laboratory of Optical Fiber Technology, Maria Curie-Sklodowska University, pl. M. Curie-Sklodowskiej 3, Lublin, Poland.
    Lehmann, Kevin K.
    Departments of Chemistry and Physics, University of Virginia, VA, Charlottesville, United States.
    Sub-doppler double-resonance spectroscopy of methane using a frequency comb probe2020Ingår i: Conference on Lasers and Electro-Optics, Optica Publishing Group (formerly OSA) , 2020, artikel-id STu4N.1Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 15.
    Foltynowicz, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Univ Rennes, Cnrs, Ipr Institut de Physique de Rennes-UMR 6251, Rennes, France.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Johansson, Alexandra C.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboń, Grzegorz
    Laser AND Fiber Electronics Group, Faculty of Electronics, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Martynkien, Tadeusz
    Faculty of Fundamental Problems of Technology, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Mergo, Paweł
    Laboratory of Optical Fiber Technology, Maria Curie-Sklodowska University, pl. M. Curie-Sklodowskiej 3, Lublin, Poland.
    Lehmann, Kevin K.
    Departments of Chemistry AND Physics, University of Virginia, VA, Charlottesville, United States.
    Sub-doppler double-resonance spectroscopy of methane using a frequency comb probe2020Ingår i: 2020 conference on lasers and electro-optics (CLEO): proceedings, IEEE conference proceedings, 2020, artikel-id 9192344Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 16.
    Foltynowicz-Matyba, Aleksandra
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Reduction of background signals in fiber-based NICE-OHMS2011Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 28, nr 11, s. 2797-2805Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Noise-immune cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) based on a fiber-coupled electro-optic modulator (EOM) provides a compact and versatile experimental setup. It has, however, been limited by background signals originating from an imbalance of the phase modulated triplet created by a cross-coupling between the principal axes of the polarization maintaining fibers and the extraordinary axis of the EOM. Two strategies for reducing these background signals are investigated: (i) using an EOM with a titanium diffused waveguide, in which the balance of the triplet is controlled by active feedback, and (ii) using an EOM with a proton exchanged waveguide that does not support light propagation along the ordinary axis. It is shown that both approaches significantly reduce drifts and noise in the system. Using a cavity with a finesse of 5700, an absorption sensitivity of 3: 2 x 10(-12) cm(-1) in 1 min of integration time (i.e., 1: 8 x 10(-11) cm(-1) Hz(-1/2)) is demonstrated for Doppler-broadened detection, the lowest reported so far for Doppler-broadened NICE-OHMS. For sub-Doppler detection, a minimum detectable optical phase shift of 1: 3 x 10(-12) cm(-1) in 400s of integration time is obtained. (C) 2011 Optical Society of America

  • 17.
    Forssén, Clayton
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Szabo, David
    Measurement Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Jönsson, Gustav
    Measurement Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Bjerling, Martin
    Measurement Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Hausmaninger, Thomas
    National Metrology Institute VTT MIKES, Tekniikantie, Finland.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    A transportable refractometer for assessment of pressure in the kPa range with ppm level precision2020Ingår i: Acta IMEKO, ISSN 0237-028X, Vol. 9, nr 5, s. 287-292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 18.
    Forssén, Clayton
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Amer, E.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Szabo, D.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Bock, T.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Kussicke, A.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Rubin, T.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Mari, D.
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Pasqualin, S.
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Silvestri, Z.
    LNE-Cnam, Paris, France.
    Bentouati, D.
    Laboratoire National de Métrologie et d'Essais, (LNE), Paris, France.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, M.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Circular comparison of conventional pressure standards using a transportable optical refractometer: preparation and transportation2022Ingår 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) , 2022Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 19.
    Forssén, Clayton
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Amer, Eynas
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Szabo, David
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Bock, Thomas
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Kussicke, André
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Rubin, Tom
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Mari, Domenico
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Pasqualin, Stefano
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Silvestri, Zaccaria
    Conservatoire national des arts et métiers (CNAM), LNE-CNAM, Paris, France.
    Bentouati, Djilali
    Laboratoire National de Métrologie et d'Essais, (LNE), Paris, France.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Demonstration of a transportable Fabry–Pérot refractometer by a ring-type comparison of dead-weight pressure balances at four European national metrology institutes2024Ingår i: Sensors, E-ISSN 1424-8220, Vol. 24, nr 1, artikel-id 7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 20.
    Forssén, Clayton
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    The short-term performances of two independent gas modulated refractometers for pressure assessments2021Ingår i: Sensors, E-ISSN 1424-8220, Vol. 21, nr 18, artikel-id 6272Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

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  • 21.
    Forssén, Clayton
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, Rise Research Institutes of Sweden, Borås, Sweden.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, M.
    Measurement Science and Technology, Rise Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    An optical pascal in Sweden2022Ingår i: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 24, nr 3, artikel-id 033002Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    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.

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  • 22.
    Forssén, Clayton
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, M.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Fabry-Perot-cavity-based refractometry without influence of mirror penetration depth2021Ingår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 39, nr 6, artikel-id 065001Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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.

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  • 23.
    Germann, Matthias
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hjältén, Adrian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boudon, Vincent
    Laboratoire ICB, UMR 6303, CNRS, Université Bourgogne Franche-Comté, Dijon, France.
    Richard, Cyril
    Laboratoire ICB, UMR 6303, CNRS, Université Bourgogne Franche-Comté, Dijon, France.
    Tennyson, Jonathan
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Yurchenko, Sergey
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Gordon, Iouli E.
    Center for Astrophysics, Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Pett, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Krzempek, Karol
    Faculty of Electronics Photonics and Microsystems, Wrocław University of Science and Technology, Wroclaw, Poland.
    Hudzikowski, Arkadiusz
    Faculty of Electronics Photonics and Microsystems, Wrocław University of Science and Technology, Wroclaw, Poland.
    Głuszek, Aleksander
    Faculty of Electronics Photonics and Microsystems, Wrocław University of Science and Technology, Wroclaw, Poland.
    Soboń, Grzegorz
    Faculty of Electronics Photonics and Microsystems, Wrocław University of Science and Technology, Wroclaw, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    High accuracy line lists of CH4 and H2CO in the 8 µm range from optical frequency comb fourier transform spectroscopy2023Ingår i: 2023 conference on lasers and electro-optics Europe & European quantum electronics conference (CLEO/Europe-EQEC), IEEE, 2023, artikel-id 10232703Konferensbidrag (Refereegranskat)
  • 24.
    Germann, Matthias
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hjältén, Adrian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gordon, Iouli E.
    Center for Astrophysics, Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Tennyson, Jonathan
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Yurchenko, Sergey
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Krzempek, Karol
    Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Hudzikowski, Arkadiusz
    Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Gluszek, Aleksander
    Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Pett, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Soboii, Grzegorz
    Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Precision frequency comb spectroscopy in the 8 µm range2023Ingår i: CLEO 2023: Proceedings, Optical Society of America, 2023, artikel-id AW4E.1Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 25.
    Germann, Matthias
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hjältén, Adrian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tennyson, Jonathan
    Department of Physics and Astronomy, University College London, Gower Street, London, United Kingdom.
    Yurchenko, Sergei N.
    Department of Physics and Astronomy, University College London, Gower Street, London, United Kingdom.
    Gordon, Iouli E.
    Center for Astrophysics, Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Pett, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Krzempek, Karol
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Hudzikowski, Arkadiusz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Soboń, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical frequency comb Fourier transform spectroscopy of formaldehyde in the 1250 to 1390 cm−1 range: experimental line list and improved MARVEL analysis2024Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 312, artikel-id 108782Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 26.
    Hausmaninger, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened mid-infrared NICE-OHMS system based on an optical parametric oscillator2016Ingår i: Laser Applications to Chemical, Security and Environmental Analysis, Optica Publishing Group (formerly OSA) , 2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    An OPO-based NICE-OHMS instrument for trace gas detection addressing fundamental vibration transitions in the mid-IR (3.2-3.9 µm) range has been developed. It shows a detection sensitivity for CH4 of 2.4×10−10cm−1Hz−1∕2 (corresponding to low ppt concentrations).

  • 27.
    Hausmaninger, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry in the mid-IR region down to 10−10 cm−1 Hz−1/2Manuskript (preprint) (Övrigt vetenskapligt)
  • 28.
    Hausmaninger, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Narrowing of the linewidth of an optical parametric oscillator by an acousto-optic modulator for the realization of mid-IR noise-immune cavity-enhanced optical heterodyne molecular spectrometry down to 10(-10) cm(-1) Hz(-1/2)2015Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 23, nr 26, s. 33641-33655, artikel-id UNSP 252446Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The linewidth of a singly resonant optical parametric oscillator (OPO) has been narrowed with respect to an external cavity by the use of an acousto-optic modulator (AOM). This made possible an improvement of the sensitivity of a previously realized OPO-based noise-immune cavity-enhanced optical heterodyne molecular spectrometry instrument for the 3.2 - 3.9 mu m mid-infrared region by one order of magnitude. The resulting system shows a detection sensitivity for methane of 2.4 x 10(-10) cm(-1) Hz(-1/2) and 1.3 x 10(-10) cm(-1) at 20 s, which allows for detection of both the environmentally important (CH4)-C-13 and CH3D isotopologues in atmospheric samples. (C) 2015 Optical Society of America

  • 29.
    Hausmaninger, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ma, Weiguang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Shanxi University, Taiyuan 030006, China.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – II: experimental verification2016Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 168, s. 245-256Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is normally described by an expression, here termed the conventional (CONV) description, that is restricted to the conventional cavity-limited weak absorption condition (CCLWA), i.e. when the single pass absorbance is significantly smaller than the empty cavity losses, i.e. when α0L<<π/F. To describe NICE-OHMS signals beyond this limit two simplified extended descriptions (termed the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT), which are assumed to be valid under the relaxed cavity-limited weak absorption condition (RCLWA), i.e. when α0L<π/Fα0L<π/F, and a full description (denoted FULL), presumed to be valid also when the α0L<π/Fα0L<π/F condition does not hold, have recently been derived in an accompanying work (Ma W, et al. Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition - I. Theoretical Description. J Quant Spectrosc Radiat Transfer, 2015, http://dx.doi.org/10.1016/j.jqsrt.2015.09.007, this issue). The present work constitutes an experimental verification and assessment of the validity of these, performed in the Doppler limit for a set of Fα0L/πFα0L/π values (up to 3.5); it is shown under which conditions the various descriptions are valid. It is concluded that for samples with Fα0L/πFα0L/π up to 0.01, all descriptions replicate the data well. It is shown that the CONV description is adequate and provides accurate assessments of the signal strength (and thereby the analyte concentration) up to Fα0L/πFα0L/π of around 0.1, while the ELET is accurate for Fα0L/πFα0L/π up to around 0.3. The ELFT description mimics the Db NICE-OHMS signal well for Fα0L/πFα0L/π up to around unity, while the FULL description is adequate for all Fα0L/πFα0L/π values investigated. Access to these descriptions both increases considerably the dynamic range of the technique and facilitates calibration using certified reference gases, which thereby significantly broadens the applicability of the Db NICE-OHMS technique.

  • 30.
    Hjältén, Adrian
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rosina, Andrea
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Université de Rennes, CNRS, IPR (Institut de Physique de Rennes)-UMR 6251, Rennes, France..
    Soboń, Grzegorz
    Laser and Fiber Electronics Group, Faculty of Electronics, Photonics and Microsystems, Wrocław University of Science and Technology, Wroclaw, Poland..
    Lehmann, Kevin
    Departments of Chemistry and Physics, University of Virginia, VA, Charlottesville, United States..
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Accurate measurement and assignment of high rotational energy levels in the 9150 - 9370 cm−1 range of methane using optical frequency comb double-resonance spectroscopyManuskript (preprint) (Övrigt vetenskapligt)
  • 31.
    Hjältén, Adrian
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rosina, Andrea
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rutkowski, Lucile
    Univ Rennes, CNRS, IPR (Institut de Physique de Rennes), UMR 6251, Rennes, France.
    Sobon, Grzegorz
    Faculty of Electronics, Photonics and Microsystems, Wroclaw University of Science and Technology, Wroclaw, Poland.
    Lehmann, Kevin K.
    Department of Chemistry & Physics, University of Virginia, VA, Charlottesville, United States.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Accurate measurement and assignment of high rotational energy levels of the 3v3 ← v3 band of methane2023Ingår i: 2023 conference on lasers and electro-optics, CLEO 2023, IEEE, 2023, artikel-id STh4L.4Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 32.
    Lu, Chuang
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Vieira, Francisco Senna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gluszek, Aleksander
    Wrocław University of Science and Technology, Laser Fiber Electronics Group, Faculty of Electronics, Wroclaw, Poland.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sobon, Grzegorz
    Wrocław University of Science and Technology, Laser Fiber Electronics Group, Faculty of Electronics, Wroclaw, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Robust and High-Speed Cavity-Enhanced Vernier Spectrometer2021Ingår i: 2021 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2021, IEEE Lasers and Electro-Optics Society, 2021, artikel-id ch_10_5Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 33.
    Lu, Chuang
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Vieira, Francisco Senna
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Głuszek, Aleksander
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wybrzeze Wyspianskiego 27, Wrocław, Poland.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sobon, Grzegorz
    Laser & Fiber Electronics Group, Faculty of Electronics, Wrocław University of Science and Technology, Wybrzeze Wyspianskiego 27, Wrocław, Poland.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Robust, fast and sensitive near-infrared continuous-filtering Vernier spectrometer2021Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 29, nr 19, s. 30155-30167Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 34.
    Ma, Weiguang
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. State Key Laboratory of Quantum Optics and Quantum Optics Devices, Institute of Laser Spectroscopy, Shanxi University, Taiyuan 030006, China.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened NICE-OHMS beyond the cavity-limited weak absorption condition – I. Theoretical Description2016Ingår i: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 168, s. 217-244Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) is conventionally described by an expression (here referred to as the CONV expression) that is restricted to the case when the single-pass absorbance, α0L, is much smaller than the empty cavity losses, π/F [here termed the conventional cavity-limited weak absorption (CCLWA) condition]. This limits the applicability of the technique, primarily its dynamic range and calibration capability. To remedy this, this work derives extended descriptions of Db NICEOHMS that are not restricted to the CCLWA condition. First, the general principles of Db NICEOHMS are scrutinized in some detail. Based solely upon a set of general assumptions, predominantly that it is appropriate to linearize the Beer–Lambert law, that the light is modulated to a triplet, and that the Pound–Drever–Hall sidebands are fully reflected, a general description of Db NICE-OHMS that is not limited to any specific restriction on α0L vs. π/F, here referred to as the FULL description, is derived. However, this description constitutes a set of equations to which no closed form solution has been found. Hence, it needs to be solved numerically (by iterations), which is inconvenient. To circumvent this, for the cases when α0Loπ/F but without the requirement that the stronger CCLWA condition needs to be fulfilled, a couple of simplified extended expressions that are expressible in closed analytical form, referred to as the extended locking and extended transmission description, ELET, and the extended locking and full transmission description, ELFT, have been derived. An analysis based on simulations validates the various descriptions and assesses to which extent they agree. It is shown that in the CCLWA limit, all extended descriptions revert to the CONV expression. The latter one deviates though from the extended ones for α0L around and above 0.1π/F. The two simplified extended descriptions agree with the FULL description for a larger range of α0L than the CONV expression, viz. for the ELET description for α0L up to 0.3π/F and for ELFT for α0L up to 0.6 or 1.0 π/F (depending on the mode of detection). It is then demonstrated that the conventional view of Db NICE-OHMS, which states that the out-of-phase and the in-phase signals can be referred to as a pure absorption and dispersion signal, respectively, breaks down when the CCLWA condition does not hold. In this case, the out-of-phase signal is additionally affected by the phase shifts of the laser components (i.e. dispersion) while the in-phase signal is also influenced by their attenuation. Access to new descriptions broadens considerably the dynamic range of Db NICE-OHMS and facilitates calibration using standard references samples, and thereby its applicability

  • 35.
    Rubin, T.
    et al.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Amer, E.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Szabo, D.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Bock, T.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Kussicke, A.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Günz, C.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Mari, D.
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Gavioso, R.M.
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Pisani, M.
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Ripa, D. Madonna
    Istituto Nazionale di Ricerca Metrologica (INRiM), Torino, Italy.
    Silvestri, Z.
    Laboratoire National de Métrologie et d'Essais (LNE), Conservatoire National des Arts et Métiers (CNAM), Paris, France.
    Gambette, P.
    Laboratoire National de Métrologie et d'Essais (LNE), Conservatoire National des Arts et Métiers (CNAM), Paris, France.
    Bentouati, D.
    Laboratoire National de Métrologie et d'Essais (LNE), Conservatoire National des Arts et Métiers (CNAM), Paris, France.
    Garberoglio, G.
    European Centre for Theoretical Studies in Nuclear Physics and Related Areas (FBK-ECT*), Trento Institute for Fundamental Physics and Applications (TIFPA-INFN), Trento, Italy.
    Lesiuk, M.
    Faculty of Chemistry, University of Warsaw and Pasteura 1, Warsaw, Poland.
    Przybytek, M.
    Faculty of Chemistry, University of Warsaw and Pasteura 1, Warsaw, Poland.
    Jeziorski, B.
    Faculty of Chemistry, University of Warsaw and Pasteura 1, Warsaw, Poland.
    Setina, J.
    IMT Institute of Metals and Technology, Lepi Pot, Ljubljana, Slovenia.
    Zelan, M.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    'Quantum-based realizations of the pascal' status and progress of the empir-project: quantumpascal2022Ingår 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) , 2022Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 36.
    Rubin, T.
    et al.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hao, M.
    School of Mechanical Engineering and Automation, Northeastern University, Shenyang, China.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Asbahr, P.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Bernien, M.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Kussicke, A.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Liu, K.
    School of Mechanical Engineering and Automation, Northeastern University, Shenyang, China.
    Zelan, M.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Thermodynamic effects in a gas modulated Invar-based dual Fabry-Pérot cavity refractometer2022Ingår i: Metrologia, ISSN 0026-1394, E-ISSN 1681-7575, Vol. 59, nr 3, artikel-id 035003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 37.
    Rubin, T.
    et al.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hao, M.
    School of Mechanical Engineering and Automation, Northeastern University, Shenyang, China.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Asbahr, P.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Bernien, M.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Kussicke, A.
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Liu, K.
    School of Mechanical Engineering and Automation, Northeastern University, Shenyang, China.
    Zelan, M.
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Thermodynamic effects in a gas modulated Invar-based dual Fabry-Pérot cavity refractometer addressing 100 kpa of nitrogen2022Ingår 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) , 2022Konferensbidrag (Refereegranskat)
    Abstract [en]

    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.

  • 38.
    Silander, Isak
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Cavity enhanced optical sensing2015Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    An optical cavity comprises a set of mirrors between which light can be reflected a number of times. The selectivity and stability of optical cavities make them extremely useful as frequency references or discri­mi­nators. With light coupled into the cavity, a sample placed inside a cavity will experience a significantly increased interaction length. Hence, they can be used also as amplifiers for sensing purposes. In the field of laser spectroscopy, some of the most sensitive techniques are therefore built upon optical cavities. In this work optical cavities are used to measure properties of gas samples, i.e. absorption, dispersion, and refractivity, with unprecedented precision.

    The most sensitive detection technique of all, Doppler-broadened noise-immune cavity enhanced optical heterodyne molecular spectrometry (Db NICE-OHMS), has in this work been developed to an ultra-sensitive spectroscopic technique with unprecedented detection sensitivity. By identifying limiting factors, realizing new experimental setups, and deter­mining optimal detection conditions, the sensitivity of the technique has been improved several orders of magnitude, from 8 × 10-11 to 9 × 10-14 cm-1. The pressure interval in which NICE-OHMS can be applied has been extended by deri­vation and verification of dispersions equations for so-called Dicke narrowing and speed dependent broadening effects. The theoretical description of NICE-OHMS has been expanded through the development of a formalism that can be applied to the situations when the cavity absorption cannot be considered to be small, which has expanded the dynamic range of the technique. In order to enable analysis of a large number of molecules at their most sensitive transitions (mainly their funda­mental CH vibrational transitions) NICE-OHMS instrumentation has also been developed for measurements in the mid-infrared (MIR) region. While it has been difficult to realize this in the past due to a lack of optical modulators in the MIR range, the system has been based on an optical para­metric oscillator, which can be modulated in the near-infrared (NIR) range.

    As the index of refraction can be related to density, it is possible to retrieve gas density from measurements of the index of refraction. Two such instru­men­tations have been realized. The first one is based on a laser locked to a measure­ment cavity whose frequency is measured by compassion with an optical frequency comb. The second one is based on two lasers locked to a dual-cavity (i.e. one reference and one measurement cavity). By these methods changes in gas density down to 1 × 10-9 kg/m3 can be detected.

    All instrumentations presented in this work have pushed forward the limits of what previously has been considered measurable. The knowledge acquired will be of great use for future ultrasensitive cavity-based detection methods.

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    Cavity enhanced optical sensing
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  • 39.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ehlers, Patrick
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Junyang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Frequency modulation background signals from fiber-based electro optic modulators are caused by crosstalk2012Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 29, nr 5, s. 916-923Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Frequency modulated spectroscopy (FMS) performed by the use of fiber-coupled electro optic modulators (FC-EOMs) is often plagued by background signals that bring in noise and, by their temperature dependence, cause severe drifts. These signals cannot be zeroed out by the conventional technique of using a carefully adjusted polarizer that can be applied to free space electro optic modulators (EOMs). This can limit the use of FC-EOMs in high performance detection techniques. Here we provide an explanation to these background signals that is based upon crosstalk between various polarization directions of light in the fixed mounted polarization-maintaining fibers and the electro optic crystal. The description provides a basis for the previously demonstrated technique that utilizes an EOM regulated simultaneously by temperature and DC voltage to eliminate background signals from systems encompassing FC-EOMs. (C) 2012 Optical Society of America

  • 40.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    An invar-based fabry-perot cavity refractometer with a gallium fixed-point cell for assessment of pressure2020Ingår i: Acta IMEKO, ISSN 0237-028X, Vol. 9, nr 5, s. 293-298Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 41.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Invar-based refractometer for pressure assessments2020Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 45, nr 9, s. 2652-2655Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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 10(4) s, a white noise response (for N-2) of 3 mPa s(1/2). 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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  • 42.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical realization of the pascal—Characterization of two gas modulated refractometers2021Ingår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 39, nr 4, artikel-id 044201Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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-) 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 () was estimated to, for the SOP and TOP, and , 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 () for comparative measurements (27 ppm). This verified that the estimated error budget for the uncorrelated errors holds over this extensive period of time.

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  • 43.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Model for in-coupling of etalons into signal strengths extracted from spectral line shape fitting and methodology for predicting the optimum scanning range: demonstration of Doppler-broadened, noise-immune, cavity-enhanced optical heterodyne molecular spectroscopy down to 9  ×  10−14 cm−12015Ingår i: Journal of the Optical Society of America. B, Optical physics, ISSN 0740-3224, E-ISSN 1520-8540, Vol. 32, nr 10, s. 2104-2114Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Expressions for the in-coupling of white noise and etalons into fitted signal strengths are derived. These show that the amount of noise picked up is affected by the scanning range. A methodology for finding the optimum scanning range from a single set of measurements has been developed. This was used to estimate the optimum conditions of a noise-immune, cavity-enhanced optical heterodyne molecular spectroscopy (NICE-OHMS) setup. The methodology was validated by measurements. This resulted in a spectral noise equivalent absorption per unit length of 2.6 × 10−13 cm−1 Hz−1∕2 and a minimum Allan deviation of 9 × 10−14 cm−1 at 30 s, which are, to our knowledge, the lowest reported for Doppler-broadened NICE-OHMS

  • 44.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. National Metrology Institute VTT MIKES, Finland.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gas equilibration gas modulation refractometry for assessment of pressure with sub-ppm precision2019Ingår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 37, nr 4, artikel-id 042901Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gas modulation refractometry (GAMOR) is a methodology that, by performing repeated reference assessments with the measurement cavity being evacuated while the reference cavity is held at a constant pressure, can mitigate drifts in dual Fabry-Perot cavity based refractometry. A novel realization of GAMOR, referred to as gas equilibration GAMOR, that outperforms the original realization of GAMOR, here referred to as single cavity modulated GAMOR (SCM-GAMOR), is presented. In this, the reference measurements are carried out by equalizing the pressures in the two cavities, whereby the time it takes to reach adequate conditions for the reference measurements has been reduced. This implies that a larger fraction of the measurement cycle can be devoted to data acquisition, which reduces white noise and improves on its short-term characteristics. The presented realization also encompasses a new cavity design with improved temperature stabilization and assessment. This has contributed to improved long-term characteristics of the GAMOR methodology. The system was characterized with respect to a dead weight pressure balance. It was found that the system shows a significantly improved precision with respect to SCM-GAMOR for all integration times. For a pressure of 4303 Pa, it can provide a response for short integration times (up to 10 min) of 1.5 mPa (cycle)1/2, while for longer integration times (up to 18 h), it shows an integration time-independent Allan deviation of 1mPa (corresponding to a precision, defined as twice the Allan deviation, of 0.5 ppm), exceeding the original SCM-GAMOR system by a factor of 2 and 8, respectively. When used for low pressures, it can provide a precision in the sub-mPa region; for the case with an evacuated measurement cavity, the system provided, for up to 40 measurement cycles (ca. 1.5 h), a white noise of 0.7 mPa (cycle)1/2, and a minimum Allan deviation of 0.15mPa. It shows a purely linear response in the 2.8-10.1 kPa range. This implies that the system can be used for the transfer of calibration over large pressure ranges with exceptional low uncertainty.

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  • 45.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ma, Weiguang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ehlers, Patrick
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry down to 4 x 10-13 cm-1 Hz-1/2: implementation of a 50,000 finesse cavity2015Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, nr 9, s. 2004-2007Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We report on the realization of a Doppler-broadened noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) instrumentation based on a high-finesse (50,000) cavity with a detection sensitivity of 4 x 10(-13) cm(-1) Hz(-1/2). For the P-e(11) transition targeted at 1.5316 mu m, this corresponds to a C2H2 concentration of 240 ppq (parts-per-quadrillion) detected at 100 Torr. The setup was originally affected by recurrent dips in the cavity transmission, which were attributed to excitation of high-order transverse mode by scattering from the mirrors. The effect of these was reduced by insertion of a small pinhole in the cavity.

  • 46.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Ma, Weiguang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Harren, Frans J. M.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doppler-broadened mid-infrared noise-immune cavity-enhanced optical heterodyne molecular spectrometry based on an optical parametric oscillator for trace gas detection2015Ingår i: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 40, nr 4, s. 439-442Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An optical parametric oscillator based Doppler-broadened (Db) noise-immune cavity-enhanced optical heterodyne molecular spectrometry (NICE-OHMS) system suitable for addressing fundamental vibrational transitions in the 3.2-3.9 mu m mid-infrared (MIR) region has been realized. An Allan-Werle analysis provides a detection sensitivity of methane of 1.5 x 10-9 cm(-1) with a 20 s integration time, which corresponds to 90 ppt of CH4 if detected at the strongest transition addressed at 40 Torr. This supersedes that of previous Db MIR NICE-OHMS demonstrations and suggests that the technique can be suitable for detection of both the environmentally important (CH4)-C-13 and CH3D isotopologues. It also opens up for detection of many other molecular species at ppt and sub-ppt concentration levels.

  • 47.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Gas modulation refractometry for high-precision assessment of pressure under non-temperature-stabilized conditions2018Ingår i: Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films, ISSN 0734-2101, E-ISSN 1520-8559, Vol. 36, nr 3, artikel-id 03E105Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The authors report on the realization of a novel methodology for refractometry-GAs modulation refractometry (GAMOR)-that decreases the influence of drifts in Fabry Perot cavity refractometry. The instrumentation is based on a dual Fabry-Perot cavity refractometer in which the beat frequency between the light fields locked to two different cavities, one measurement and one reference cavity, is measured. The GAMOR methodology comprises a process in which the measurement cavity sequentially is filled and evacuated while the reference cavity is constantly evacuated. By performing beat frequency measurements both before and after the finite-pressure measurement, zero point references are periodically created. This opens up for high precision refractometry under nontemperature-stabilized conditions. A first version of an instrumentation based on the GAMOR methodology has been realized and its basic performance has been scrutinized. The refractometer consists of a Zerodur cavity-block and tunable narrow linewidth fiber lasers operating within the C34 communication channel (i.e., around 1.55 μm) at which there are a multitude of fiber coupled off-the-shelf optical, electro-optic, and acousto-optic components. The system is fully computer controlled, which implies it can perform unattended gas assessments over any foreseeable length of time. When applied to a system with no active temperature stabilization, the GAMOR methodology has demonstrated a 3 orders of magnitude improvement of the precision with respect to conventional static detection. When referenced to a dead weight pressure scale the instrumentation has demonstrated assessment of pressures in the kilo-Pascal range (4303 and 7226 Pa) limited by white noise with standard deviations in the 3.2N-1/2-3.5N-1/2 mPa range, where N is the number of measurement cycles (each being 100 s long). For short measurement times (up to around 103 s), the system exhibits a (1σ) total relative precision of 0.7 (0.5) ppm for assessment of pressures in the 4 kPa region and 0.5 (0.4) ppm for pressures around 7 kPa, where the numbers in parentheses represent the part of the total noise that has been attributed to the refractometer. As long as the measurement procedure is performed over short time scales, the inherent properties of the GAMOR methodology allow for high precision assessments by the use of instrumentation that is not actively temperature stabilized or systems that are affected by outgassing or leaks. They also open up for a variety of applications within metrology; e.g., transfer of calibration and characterization of pressure gauges, including piston gauges.

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  • 48.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hausmaninger, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    A dual Fabry-Perot cavity for fast assessments of gasnumber densityManuskript (preprint) (Övrigt vetenskapligt)
  • 49.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Silva de Oliveira, Vinicius
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forssén, Clayton
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Rubin, Tom
    Physikalisch-Technische Bundesanstalt (PTB), Berlin, Germany.
    Zelan, Martin
    Measurement Science and Technology, RISE Research Institutes of Sweden, Borås, Sweden.
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    In situ determination of the penetration depth of mirrors in Fabry-Perot refractometers and its influence on assessment of refractivity and pressure2022Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 30, nr 14, s. 25891-25906Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    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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  • 50.
    Silander, Isak
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zelan, Martin
    Axner, Ove
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Arrhen, Fredrik
    Pendrill, Leslie
    Foltynowicz, Aleksandra
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Optical measurement of the gas number density in a Fabry-Perot cavity2013Ingår i: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 24, nr 10, s. 105207-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An optical method for measuring the gas density by monitoring the refractive index inside a high-finesse Fabry-Perot cavity is presented. The frequency of a narrow linewidth Er:fiber laser, locked to a mode of the cavity, is measured with the help of an optical frequency comb while the gas density inside the cavity changes. A resolution of 1.4 x 10(-6) mol m(-3) is achieved in 3 s for nitrogen, which allows measurement of a relative gas density change of 3.4 x 10(-8) at atmospheric pressure.

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