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  • 1.
    Axner, Ove
    et al.
    Umeå University, Sweden.
    Forssen, Clayton
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    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

  • 2.
    Axner, Ove
    et al.
    Umeå University, Sweden .
    Silander, Isak
    Umeå University, Sweden .
    Forssen, Clayton
    Umeå University, Sweden .
    Zakrisson, Johan
    Umeå University, Sweden .
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    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

  • 3.
    Axner, Ove
    et al.
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Forssén, Clayton
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    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 i tidskrift (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. © 2021 The Author(s)

  • 4.
    Battelier, Baptiste
    et al.
    Université de Bordeaux, France.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Exploring the foundations of the physical universe with space tests of the equivalence principle2021Ingår i: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 51, nr 3, s. 1695-1736Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present the scientific motivation for future space tests of the equivalence principle, and in particular the universality of free fall, at the 10− 17 level or better. Two possible mission scenarios, one based on quantum technologies, the other on electrostatic accelerometers, that could reach that goal are briefly discussed. This publication is a White Paper written in the context of the Voyage 2050 ESA Call for White Papers. © 2021, The Author(s).

  • 5.
    Ebenhag, Sven-Christian
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Zelan, Martin
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Hedekvist, Per Olof
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Karlsson, Magnus
    Chalmers University of Technology, Sweden.
    Implementation of an optical fiber frequency distribution via commercial DWDM2016Ingår i: 2016 IEEE International Frequency Control Symposium (IFCS), 2016, artikel-id 7563586Konferensbidrag (Refereegranskat)
    Abstract [en]

    The rapid development in communication infrastructure over the past decades entails an increasing dependence on time and frequency, as well as its redundant distribution. This places demands not only on already existing distribution methods, but also on the development of new ones to meet future needs. To meet these demands several research groups are working on high performance fiber-based frequency transfer techniques. The best achieved performance so far is the techniques using a single bi-directional fiber connection, with customized bi-directional optical amplifiers [1]. The objective of this project is to develop a method that is compatible with data communication in DWDM-systems, i.e. using the existing infrastructure, as well as to be complementary technique for time and frequency distribution. Even though it is likely to have worse performance than the bi-directional system in terms of frequency stability, it will allow for the impassable obligation to follow the deployed structure of telecom networks. The establishment and early results of the non-stabilized link has been previously presented [2, 3]. The ongoing evaluation and improvement will be aimed at finding relevant performance specifications for a connection using this technique. The work presented here is the most recent results of the frequency transfer and discusses the future plans for the fiber connection, including the added time transfer method. If proven successful, the long-term objective is to establish a distribution network for optical frequency references in Sweden.

  • 6.
    Forssen, Clayton
    et al.
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Szabo, David
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Jönsson, Gustav
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Bjerling, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Hausmaninger, Thomas
    VTT, Finland.
    Axner, Ove
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    A TRANSPORTABLE REFRACTOMETER FOR ASSESSMENT OF PRESSURE IN THE KPA RANGE WITH PPM LEVEL PRECISION2020Ingår i: Acta IMEKO, ISSN 2221-870X, 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 - 2.1ppm). This shows that the system can be disassembled, packed, transported, unpacked, and reassembled with virtually unchanged performance. 

  • 7.
    Forssén, C
    et al.
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Silander, I
    Umeå University, Sweden.
    Zakrisson, J.
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, O
    Umeå University, Sweden.
    An optical pascal in Sweden2022Ingår i: Journal of Optics, ISSN 2040-8978, E-ISSN 2040-8986, Vol. 24, nr 3, artikel-id 033002Artikel 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 where a laser is used to probe the frequency of a cavity mode, which is shifted in relation to the refractivity of the gas in the cavity. Recent activities have indicated that such systems can demonstrate an extended uncertainty in the 10 ppm (parts-per-million or 10-6) range. As a means to reduce the influence of various types of disturbances (primarily drifts and fluctuations) a methodology based on modulation, denoted gas modulation refractometry (GAMOR), has recently been developed. Systems based on this methodology are in general high-performance, e.g. they have demonstrated precision in the sub-ppm range, and they are sturdy. They can also be made autonomous, allowing for automated and unattended operation for virtually infinite periods of time. To a large degree, the development of such instruments depends on the access to modern photonic components, e.g. narrow line-width lasers, electro-and acousto-optic components, and various types of fiber components. This work highlights the role of such modern devices in GAMOR-based instrumentation and provides a review on the recent development of such instruments in Sweden that has been carried out in a close collaboration between a research institute and the Academy. It is shown that the use of state-of-the-art photonic devices allows sturdy, automated and miniaturized instrumentation that, for the benefit of industry, can serve as standards for pressure and provide fast, unattended, and calibration-free pressure assessments at a fraction of the present cost. © 2022 The Author(s).

  • 8.
    Forssén, Clayton
    et al.
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Silander, I.
    Umeå University, Sweden.
    Zakrisson, J.
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, O.
    Umeå University, Sweden.
    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. © 2021 Author(s).

  • 9.
    Forssén, Clayton
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Amer, Eynas
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Szabo, David
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Bock, Thomas
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Kussike, Andre
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Rubin, Tom
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Mari, Domenico
    INRiM Istituto Nazionale di Ricerca Metrologica, Italy.
    Pasqualin, Stefano
    INRiM Istituto Nazionale di Ricerca Metrologica, Italy.
    Silvestri, Zaccaria
    Conservatoire National des Arts et Métiers Laboratoire Commun de Métrologie, France.
    Bentouati, Djilali
    LNE Laboratoire National de Métrologie et d’Essais, France.
    Axner, Ove
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Demonstration of a Transportable Fabry–Pérot Refractometer by a Ring-Type Comparison of Dead-Weight Pressure Balances at Four European National Metrology Institutes2023Ingår i: Sensors, E-ISSN 1424-8220, Vol. 24, nr 1Artikel 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.

  • 10.
    Forssén, Clayton
    et al.
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Axner, Ove
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    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. © 2021 by the authors.

  • 11.
    Pendrill, Leslie
    et al.
    RISE - Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Zelan, Martin
    RISE - Research Institutes of Sweden, Säkerhet och transport.
    Det nya internationella måttsystemet: – tid för ett nytt måttsystem2017Rapport (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Idag kan alla måttenheter härledas från SI-systemets sju basenheter (meter, kilogram, sekund, kelvin, candela, ampere, mol). Genom nya forskningsframsteg planeras nu en reformering av SI-systemet. Förändringen förväntas att bli beslutad 2018, och forskare på alla länders olika Nationella Metrologiinstitut jobbar nu med förberedelserna för att införa det nya SI-systemet.

  • 12.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Durán, Vicente
    University Jaume I, Spain.
    Helgason, Óskar Bjarki
    Chalmers University of Technology, Sweden.
    Girardi, Marcello
    Chalmers University of Technology, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Thermal-Controlled Scanning of a Bright Soliton in a Photonic Molecule2023Ingår i: 2023 Conference on Lasers and Electro-Optics Europe and European Quantum Electronics Conference, CLEO/Europe-EQEC 2023, Institute of Electrical and Electronics Engineers Inc. , 2023Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Over the last few years, dissipative Kerr solitons (DKS) in microresonators have boosted the development of chip-scale frequency comb sources (microcombs) in a variety of applications, from coherent communications to ultrafast distance ranging [1]. However, the intrinsic large free spectral range (FSR) of microcombs (within the gigahertz regime) is still a drawback for applications such as molecular spectroscopy, in which the comb line spacing dictates the spectral sampling resolution. Overcoming spectral sparsity by scanning the comb modes across a full FSR is challenging for a DKS microcomb, since the soliton operation must be kept while the pump laser is continuously swept. So far, it has been accomplished for a single microresonator by combining a feedback control loop with the thermal tuning of the cavity resonances by means of a microheater [2]. Recently, the use of two linearly coupled cavities (a photonic molecule) has shown to be a promising alternative to generate soliton microcombs with high conversion efficiency and uniform power distribution [3]. In this contribution, we address the challenge of scanning the soliton comb modes of a photonic molecule by thermal tuning. Specifically, we implement a scheme to scan a bright soliton over 60 GHz by tuning simultaneously the pump laser and the resonances of two coupled cavities.

  • 13.
    Rebolledo-Salgado, Israel
    et al.
    Chalmers University of Technology, Sweden.
    Helgason, Oskar Bjarki
    Chalmers University of Technology, Sweden.
    Girardi, Marcello
    Chalmers University of Technology, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Active Feedback Stabilization of Super-efficient Microcombs2023Ingår i: 2023 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC), Institute of Electrical and Electronics Engineers (IEEE), 2023Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    In the past years, major scientific and technological progress has been made in the field of dissipative Kerr solitons (DKS) frequency combs on microresonators (microcombs) [1]. The generation of microcombs in $\text{Si}_{3}\mathrm{N}_{4}$ microresonators exhibit broad bandwidth, high repetition rate, and low power consumption. These capabilities have opened a venue for applications within optical communication [2]. However, continuous operation and high power per comb line are needed in order to address the demands of system-level applications. Recent works have demonstrated the generation of bright solitons with unprecedented high power conversion efficiency using photonic molecules [3]. In this work, we report the continuous operation of a super-efficient DKS microcomb over 25 hours using a packaged module. The soliton state is maintained by the stabilization of thermal drifts and the on-chip optical power in the cavity. Our photonic molecule is composed of two coupled cavities with heaters placed on top. The fabricated device has been robustly packaged into a fiber-connectorized module to prevent random variations of the power coupling (Fig. 1(a)). The experimental setup used for the feedback control is shown in Fig 1. (b). The comb is generated with 20 mW of on-chip optical power covering a bandwidth of $\sim 100$ nm, see Fig. 1(c). The power conversion efficiency of the bright soliton corresponds to 32 percent. The long-term operation is achieved by harnessing the thermal drifting of the main resonance via a feedback loop implemented on an FPGA board. The soliton power is used as a control parameter to maintain a fixed pump detuning. This indicates that the coupling between these parameters holds in the super-efficient configuration of the photonic molecule as in [4]. Fig. 1(d) shows the spectral envelope of the microcomb with constant power over 25 hours. Since the pump laser is free-running, the active control forces the cavity to follow in order to maintain a fixed pump detuning. As a result, the frequency of the repetition rate of the microcomb drifts over 800 kHz towards higher frequencies (Fig. 1(e)). The frequency drifting of the pump laser (Toptica CTL) was monitored over the last 5 hours of the soliton existence by beating versus a frequency comb (Menlo FC1500), see Fig. 1(f). During the first 100 minutes of recording the resulting beat note drifts, increasing the frequency until it leaves the set span window. As the drifting continues, the beating with a neighboring line of the frequency comb is observed. The soliton power is stabilized as the photo-detected converted power remains constant (Fig. 1(f)). Nevertheless, the drifts exhibited are very minor, and we expect increased stability by feeding back into the laser piezo-control.

  • 14.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Helgason, ÓB.
    Chalmers University of Technology, Sweden.
    Ye, Z.
    Chalmers University of Technology, Sweden.
    Schröder, J.
    Chalmers University of Technology, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Torres-Company, V.
    Chalmers University of Technology, Sweden.
    Photonic molecule microcombs at 50 GHz repetition rate2022Ingår i: Optics InfoBase Conference Papers, Optica Publishing Group (formerly OSA) , 2022, artikel-id SW4O.8Konferensbidrag (Refereegranskat)
    Abstract [en]

    We present a microcomb in a photonic molecule with 50 GHz repetition rate. The comb attains > 50% power conversion efficiency and displays a quiet point of operation in repetition rate with decreased phase noise. © 2022 The Author(s)

  • 15.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Quevedo-Galan, Clara
    Universidad Politécnica de Madrid, Spain.
    Helgason, Óskar Bjarki
    Chalmers University of Technology, Sweden.
    Lööf, Anton
    Chalmers University of Technology, Sweden.
    Ye, Zhichao
    Chalmers University of Technology, Sweden.
    Lei, Fuchuan
    Chalmers University of Technology, Sweden.
    Schröder, Jochen
    Chalmers University of Technology, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Platicon dynamics in photonic molecules2023Ingår i: Communications Physics, E-ISSN 2399-3650, Vol. 6, nr 1, artikel-id 303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Coherent dissipative structures known as platicons can be reliably generated in photonic molecules, resulting in deterministic and reproducible microcombs derived from a continuous-wave pump. However, the supermode spectrum of standard photonic molecules displays numerous avoided mode crossings, distorting the spectral envelope of platicon microcombs. Here, we obtain a platicon microcomb using a photonic molecule configuration based on two coupled microcavities, whose size differs by an order of magnitude. This results in an engineered microcomb spectrum that closely resembles the one generated in an ideal single microresonator with just one frequency mode shift. We observe the coupling between the repetition rate of the platicon microcomb with the frequency of the pump laser, an effect originating from the dispersive-wave recoil induced by mode crossings. Using two identical platicon microcombs, we make use of such coupling to realize dual-comb interferometry. These results contribute to understanding dissipative structures in normal-dispersion microresonators and offer an alternative to applications such as spectroscopy and metrology. 

  • 16.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Ye, Z.
    Chalmers University of Technology, Sweden.
    Christensen, S.
    DTU Technical University of Denmark, Denmark.
    Lei, F.
    Chalmers University of Technology, Sweden.
    Twayana, K.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Schröder, J.
    Chalmers University of Technology, Sweden.
    Torres-Company, V.
    Chalmers University of Technology, Sweden.
    Nonlinear broadening of electro-optic frequency combs in all-normal dispersion Si3N4 waveguides2021Ingår i: Optics InfoBase Conference Papers, The Optical Society , 2021Konferensbidrag (Refereegranskat)
  • 17.
    Rebolledo-Salgado, Israel
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Chalmers University of Technology, Sweden.
    Ye, Zhichao
    Chalmers University of Technology, Sweden.
    Christensen, Simon
    DTU Technical University of Denmark, Denmark.
    Lei, Fuchuan
    Chalmers University of Technology, Sweden.
    Twayana, Krishna
    Chalmers University of Technology, Sweden.
    Schröder, Jochen
    Chalmers University of Technology, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Torres-Company, Victor
    Chalmers University of Technology, Sweden.
    Coherent supercontinuum generation in all-normal dispersion Si3N4 waveguides2022Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 30, nr 6, s. 8641-8651Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Spectral broadening of optical frequency combs with high repetition rate is of significant interest in optical communications, radio-frequency photonics and spectroscopy. Silicon nitride waveguides (Si3N4) in the anomalous dispersion region have shown efficient supercontinuum generation spanning an octave-bandwidth. However, the broadening mechanism in this regime is usually attained with femtosecond pulses in order to maintain the coherence. Supercontinuum generation in the normal dispersion regime is more prone to longer (ps) pulses, but the implementation in normal dispersion silicon nitride waveguides is challenging as it possesses strong requirements in propagation length and losses. Here, we experimentally demonstrate the use of a Si3N4 waveguide to perform coherent spectral broadening using pulses in the picosecond regime with high repetition rate. Moreover, our work explores the formation of optical wave breaking using a higher energy pulse which enables the generation of a coherent octave spanning spectrum. These results offer a new prospect for coherent broadening using long duration pulses and replacing bulky optical components.

  • 18.
    Rubin, T.
    et al.
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Silander, I.
    Umeå University, Sweden.
    Zakrisson, J.
    Umeå University, Sweden.
    Hao, M.
    Northeastern University, China.
    Forssén, C
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Asbahr, P.
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Bernien, M.
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Kussicke, A.
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Liu, K.
    Northeastern University, China.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, O.
    Umeå University, Sweden.
    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. 

  • 19.
    Silander, I.
    et al.
    Umeå University, Sweden.
    Zakrisson, J
    RISE Research Institutes of Sweden. Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, O.
    Umeå University, Sweden.
    An Invar-based dual Fabry-Perot cavity refractometer for assessment of pressure with a pressure independent uncertainty in the sub-mPa region2023Ingår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 41, nr 6, artikel-id 064206Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An updated version of an Invar-based dual Fabry-Perot cavity refractometer utilizing the gas modulation methodology has been characterized with regard to its ability to assess gas pressure in the low pressure regime, defined as the regime in which the instrumentation is mainly limited by the constant term a in the [ ( a ) 2 + ( b × P ) 2 ] 1 / 2 expression for the uncertainty. It is first concluded that this ability is predominantly limited by three entities, viz., the empty cavity repeatability, the residual gas pressures in the evacuated (measurement) cavity, and the contamination of the gas residing in the measurement cavity that originates from leaks and outgassing. We then present and utilize methods to separately estimate the uncertainty of the updated refractometer from these entities. It was found that, when utilizing gas modulation cycles of 100 s and when addressing nitrogen, the system can assess pressure in the low pressure regime with an expanded uncertainty ( k = 2 ) of 0.75 mPa, mainly limited by the empty cavity repeatability and outgassing of hydrogen. This is more than 1 order of magnitude below the previously assessed low pressure performance of the instrumentation.

  • 20.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Forssen, Clayton
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Umeå University, Sweden.
    Zakrisson, J
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    AN INVAR-BASED FABRY-PEROT CAVITY REFRACTOMETER WITH AGALLIUM FIXED-POINT CELL FOR ASSESSMENT OF PRESSURE2020Ingår i: Acta IMEKO, nr 5, s. 293-298Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An Invar-based Fabry-Perot cavity refractometer equipped with an automated, miniaturized galliumfixed-point cell for assessment of pressure is presented. The use of an Invar cavity spacer has previously demonstrated pressure assessments with sub-0.1 ppm precision. The fixed-point cell, whose design and implementation are presented here, provides a reference for temperature assessment of the gas inside the cavity with an uncertainty of 4 ppm. This opens up for a self-contained system for realization of the Pascal with an accuracy in the low ppm range. This is an important step towards disseminating the Pascal through fundamental principles. 

  • 21.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Forssen, Clayton
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    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 104 s, a white noise response (for N2) of 3 mPa s1=2. At 4303 Pa, the system has a minimum Allan deviation of 0.34 mPa (0.08 ppm) and a long-term stability (24 h) of 0.7 mPa. This shows that the GAMOR methodology allows for the use of alternative cavity materials.

  • 22.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Forssén, Clayton
    Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    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-10−6) assessment of gas refractivity and pressure. In this work, two independent GAMOR-based refractometers are individually characterized, compared to each other, and finally compared to a calibrated dead weight piston gauge with respect to their abilities to assess pressure in the 4-25 kPa range. The first system, referred to as the stationary optical pascal (SOP), uses a miniature fixed point gallium cell to measure the temperature. The second system, denoted the transportable optical pascal (TOP), relies on calibrated Pt-100 sensors. The expanded uncertainty for assessment of pressure (k=2) was estimated to, for the SOP and TOP, [(10mPa)2+(10×10−6P)2]1/2 and [(16mPa)2+(28×10−6P)2]1/2, respectively. While the uncertainty of the SOP is mainly limited by the uncertainty in the molar polarizability of nitrogen (8 ppm), the uncertainty of the TOP is dominated by the temperature assessment (26 ppm). To verify the long-term stability, the systems were compared to each other over a period of 5 months. It was found that all measurements fell within the estimated expanded uncertainty (k=2) for comparative measurements (27 ppm). This verified that the estimated error budget for the uncorrelated errors holds over this extensive period of time. © 2021 Author(s).

  • 23.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Hausmaninger, Thomas
    Umeå University, Sweden; VTT, Finland.
    Forssén, Clayton
    Umeå University, Sweden.
    Zelan, Martin
    RISE - Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    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 1 mPa (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 0.15 mPa. 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. © 2019 Author(s).

  • 24.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Hausmaninger, Thomas
    Umeå University, Sweden.
    Zelan, Martin
    RISE - Research Institutes of Sweden (2017-2019), Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    Gas modulation refractometry for high-precision assessment of pressure under nonerature-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 3.2 N - 1 / 2 - 3.5 N - 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 (1 σ) 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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  • 25.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Zakrisson, Johan
    Umeå University, Sweden.
    Silva De Oliveira, Vinicius
    Umeå University, Sweden.
    Forssén, Clayton
    Umeå University, Sweden.
    Foltynowicz, Aleksandra
    Umeå University, Sweden.
    Rubin, Tom
    PTB Physikalisch-Technische Bundesanstalt, Germany.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    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).

  • 26.
    Silander, Isak
    et al.
    Umeå University, Sweden.
    Zelan, Martin
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Axner, Ove
    Umeå University, Sweden.
    Arrhén, Fredrik
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Pendrill, Leslie
    RISE., SP – Sveriges Tekniska Forskningsinstitut.
    Foltynowicz, Aleksandra
    Umeå University, Sweden.
    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, artikel-id 105207Artikel 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 × 10-6 mol m-3 is achieved in 3 s for nitrogen, which allows measurement of a relative gas density change of 3.4 × 10-8 at atmospheric pressure.

  • 27.
    Zakrisson, Johan
    et al.
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    de Oliveira, V. S.
    Umeå University, Sweden.
    Hjältén, Adrian
    Umeå University, Sweden.
    Rosina, Andrea
    Umeå University, Sweden.
    Rubin, Tom
    PTB, Germany.
    Foltynowicz, Aleksandra
    Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    Procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry2024Ingår i: Optics Express, E-ISSN 1094-4087, Vol. 32, nr 3, s. 3959-3973Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A procedure for automated low uncertainty assessment of empty cavity mode frequencies in Fabry-Pérot cavity based refractometry that does not require access to laser frequency measuring instrumentation is presented. It requires a previously well-characterized system regarding mirror phase shifts, Gouy phase, and mode number, and is based on the fact that the assessed refractivity should not change when mode jumps take place. It is demonstrated that the procedure is capable of assessing mode frequencies with an uncertainty of 30 MHz, which, when assessing pressure of nitrogen, corresponds to an uncertainty of 0.3 mPa. 

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  • 28.
    Zakrisson, Johan
    et al.
    Umeå University, Sweden.
    Silander, Isak
    Umeå University, Sweden.
    Forssén, Clayton
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Umeå University, Sweden.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Axner, Ove
    Umeå University, Sweden.
    Procedure for robust assessment of cavity deformation in Fabry-Pérot based refractometers2020Ingår i: Journal of Vacuum Science and Technology B: Nanotechnology and Microelectronics, ISSN 2166-2746, E-ISSN 2166-2754, Vol. 38, nr 5, artikel-id 054202Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A novel procedure for a robust assessment of cavity deformation in Fabry-Pérot (FP) refractometers is presented. It is based on scrutinizing the difference between two pressures: one assessed by the uncharacterized refractometer and the other provided by an external pressure reference system, at a series of set pressures for two gases with dissimilar refractivity (here, He and N 2). By fitting linear functions to these responses and extracting their slopes, it is possible to construct two physical entities of importance: one representing the cavity deformation and the other comprising a combination of the systematic errors of a multitude of physical entities, viz., those of the assessed temperature, the assessed or estimated penetration depth of the mirror, the molar polarizabilities, and the set pressure. This provides a robust assessment of cavity deformation with small amounts of uncertainties. A thorough mathematical description of the procedure is presented that serves as a basis for the evaluation of the basic properties and features of the procedure. The analysis indicates that the cavity deformation assessments are independent of systematic errors in both the reference pressure and the assessment of gas temperature and when the gas modulation refractometry methodology is used that they are insensitive to gas leakages and outgassing into the system. It also shows that when a high-precision (sub-ppm) refractometer is characterized according to the procedure, when high purity gases are used, the uncertainty in the deformation contributes to the uncertainty in the assessment of pressure of N 2 with solely a fraction (13%) of the uncertainty of its molar polarizability, presently to a level of a few ppm. This implies, in practice, that cavity deformation is no longer a limiting factor in FP-based refractometer assessments of pressure of N 2. © 2020 Author(s).

  • 29.
    Zelan, Martin
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Massa, kraft, längd och tryck.
    En ny sekunddefinition - en tidsfråga2014Ingår i: Fysikaktuellt, nr 3, s. 8-9Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
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  • 30.
    Zelan, Martin
    RISE - Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Gas Modulation Refractometry for High-Precision Assessment of Pressure under Non-Temperature-Stabilized Conditions2018Konferensbidrag (Övrigt vetenskapligt)
  • 31.
    Zelan, Martin
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Optisk tid – en pågående revolution inom tidsmätning2020Ingår i: Kosmos, s. 132-146Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

    Definitionen av en sekund spelar en grundläggande roll också för definitionerna av många av de andra grundenheterna. Inte minst gäller detta metern. Martin Zelan förklarar för oss att bakgrunden till detta är extremt noggranna klockor. Dessa beskrivs, liksom kopplingen till metern via ett fixt värde på ljushastigheten.

  • 32.
    Zelan, Martin
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Massa, kraft, längd och tryck.
    Arrhén, Fredrik
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Massa, kraft, längd och tryck.
    Jarlemark, Per
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Kommunikation.
    Mollmyr, Oscar
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Massa, kraft, längd och tryck.
    Johansson, Håkan
    Simea Optics AB, Sweden.
    Characterization of a fiber-optic pressure sensor in a shock tube system for dynamic calibrations2015Ingår i: Metrologia, ISSN 0026-1394, E-ISSN 1681-7575, Vol. 52, nr 1, s. 48-53Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Measurements of mechanical quantities such as pressure often take place under dynamic conditions, yet no traceable standards for the primary dynamic calibration of pressure sensors currently exist. In theory, shock tubes can provide a close to perfect step-function ideal for the calibration of pressure transducers. In this paper we investigate a system consisting of a shock tube and an ultra-fast fiber-optical sensor that is designed to be a future primary system for dynamic pressure calibrations. For reference, the fiber-optical sensor is compared to a piezoelectric sensor, and their corresponding frequency spectra are calculated. Furthermore, an investigation of the repeatability of the fiber-optical sensor, as well as a comparison with a second shock tube, is performed.

  • 33.
    Zelan, Martin
    et al.
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Massa, kraft, längd och tryck.
    Arrhén, Fredrik
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik, Massa, kraft, längd och tryck.
    Pendrill, Leslie
    RISE., SP – Sveriges Tekniska Forskningsinstitut, SP Mätteknik.
    Foltynowicz, Aleksandra
    Silander, Isak
    Axner, Ove
    Optical measurement of the gas number density in a Fabry–Perot cavity2013Ingår i: Meas. Sci. Technol., Vol. 24, s. art nr 105207-Artikel i tidskrift (Övrigt vetenskapligt)
    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 × 10-6 mol m-3 is achieved in 3 s for nitrogen, which allows measurement of a relative gas density change of 3.4 × 10-8 at atmospheric pressure.

  • 34.
    Zelan, Martin
    et al.
    RISE - Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Pendrill, Leslie
    RISE - Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Vikten av ett nytt kilogram2018Ingår i: Fysikaktuellt, nr 3, s. 16-17Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 35.
    Zelan, Martin
    et al.
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik.
    Silander, Isak
    Umeå University, Sweden.
    Forssen, Clayton
    RISE Research Institutes of Sweden, Säkerhet och transport, Mätteknik. Umeå University, Sweden.
    Zakrisson, J
    Umeå University, Sweden.
    Axner, Ove
    Umeå University, Sweden.
    RECENT ADVANCES IN FABRY-PEROT-BASED REFRACTOMETRYUTILIZING GAS MODULATION FOR ASSESSMENT OF PRESSURE2020Ingår i: Acta IMEKO, ISSN 2221-870X, Vol. 9, nr 5, s. 299-304Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Gas modulation refractometry (GAMOR) is a methodology that can mitigate the influence off luctuations and drifts in Fabry-Pérot cavity–based refractometry. This paper presents a thorough description of its principles, what it enables, and its applicability. An overview of the latest results is presented, including the realization of a system based upon a cavity spacer made of Invar that allows for detection of N2 with sub-ppm precision, and a characterization procedure that allows for assessment of N2 with an accuracy at low-ppm levels. 

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