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Li J, Zheng J, Pan S, Li K, Yu H, Zheng W. Metasurface-based optical system for miniaturization of atomic magnetometers. OPTICS EXPRESS 2024; 32:20538-20550. [PMID: 38859434 DOI: 10.1364/oe.523114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 05/09/2024] [Indexed: 06/12/2024]
Abstract
Recent research has focused on miniaturizing atomic devices like magnetometers and gyroscopes for quantum precision measurements, leading to energy savings and broader application. This paper presents the design and validation of metasurface-based optical elements for atomic magnetometers' optical paths. These include highly efficient half-wave plates, polarizers, circular polarization generators, polarization-preserving reflectors, and polarizing beam splitters. These components, compatible with semiconductor manufacturing, offer a promising solution for creating ultra-thin, compact atomic devices.
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2
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Dong H, Ye H, Hu M, Ma Z. Recent Developments in Fabrication Methods and Measurement Schemes for Optically Pumped Magnetic Gradiometers: A Comprehensive Review. MICROMACHINES 2023; 15:59. [PMID: 38258178 PMCID: PMC10819856 DOI: 10.3390/mi15010059] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2023] [Revised: 12/12/2023] [Accepted: 12/25/2023] [Indexed: 01/24/2024]
Abstract
Optically pumped gradiometers have long been utilized in measurement in the International Geomagnetic Reference Field (IGRF). With advancements in technologies such as laser diodes and microfabrication, integrated gradiometers with compact sizes have become available, enabling improvements in magnetoencephalography and fetal magnetocardiography within shielded spaces. Moreover, there is a growing interest in the potential of achieving biomagnetic source detection without shielding. This review focuses on recent developments in optically pumped magnetic field gradiometers, including various fabrication methods and measurement schemes. The strengths and weaknesses of different types of optically pumped gradiometers are also analyzed.
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Affiliation(s)
- Haifeng Dong
- School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China; (H.D.); (H.Y.); (M.H.)
| | - Hangfei Ye
- School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China; (H.D.); (H.Y.); (M.H.)
| | - Min Hu
- School of Instrumentation and Optoelectronic Engineering, Beihang University, Beijing 100191, China; (H.D.); (H.Y.); (M.H.)
| | - Zongmin Ma
- National Key Laboratory for Dynamic Measurement Technology and School of Semiconductor and Physics, North University of China, Taiyuan 030051, China
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3
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Hahl FA, Lindner L, Vidal X, Luo T, Ohshima T, Onoda S, Ishii S, Zaitsev AM, Capelli M, Gibson BC, Greentree AD, Jeske J. Magnetic-field-dependent stimulated emission from nitrogen-vacancy centers in diamond. SCIENCE ADVANCES 2022; 8:eabn7192. [PMID: 35658038 PMCID: PMC9166290 DOI: 10.1126/sciadv.abn7192] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/16/2021] [Accepted: 04/19/2022] [Indexed: 06/15/2023]
Abstract
Negatively charged nitrogen-vacancy (NV) centers in diamond are promising magnetic field quantum sensors. Laser threshold magnetometry theory predicts improved NV center ensemble sensitivity via increased signal strength and magnetic field contrast. Here, we experimentally demonstrate laser threshold magnetometry. We use a macroscopic high-finesse laser cavity containing a highly NV-doped and low absorbing diamond gain medium that is pumped at 532 nm and resonantly seeded at 710 nm. This enables a 64% signal power amplification by stimulated emission. We test the magnetic field dependency of the amplification and thus demonstrate magnetic field-dependent stimulated emission from an NV center ensemble. This emission shows an ultrahigh contrast of 33% and a maximum output power in the milliwatt regime. The coherent readout of NV centers pave the way for novel cavity and laser applications of quantum defects and diamond NV magnetic field sensors with substantially improved sensitivity for the health, research, and mining sectors.
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Affiliation(s)
- Felix A. Hahl
- Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany
| | - Lukas Lindner
- Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany
| | - Xavier Vidal
- Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany
| | - Tingpeng Luo
- Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany
| | - Takeshi Ohshima
- National Institutes for Quantum Science and Technology (QST), 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Shinobu Onoda
- National Institutes for Quantum Science and Technology (QST), 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Shuya Ishii
- National Institutes for Quantum Science and Technology (QST), 1233 Watanuki, Takasaki, Gunma 370-1292, Japan
| | - Alexander M. Zaitsev
- College of Staten Island, CUNY, 2800 Victory Blvd., Staten Island, NY 10312, USA
- Gemological Institute of America, 50 W 47th St. #800, New York, NY 10036, USA
| | - Marco Capelli
- School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Brant C. Gibson
- ARC Centre of Excellence for Nanoscale BioPhotonics, School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Andrew D. Greentree
- ARC Centre of Excellence for Nanoscale BioPhotonics, School of Science, RMIT University, Melbourne, VIC 3001, Australia
| | - Jan Jeske
- Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Tullastrasse 72, 79108 Freiburg, Germany
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4
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Bertrand F, Jager T, Boness A, Fourcault W, Le Gal G, Palacios-Laloy A, Paulet J, Léger JM. A 4He vector zero-field optically pumped magnetometer operated in the Earth-field. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2021; 92:105005. [PMID: 34717435 DOI: 10.1063/5.0062791] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2021] [Accepted: 09/25/2021] [Indexed: 06/13/2023]
Abstract
Low intrinsic noise, high bandwidth, and high accuracy vector magnetometers are key components for many ground or space geophysical applications. Here, we report the design and the test of a 4He vector optically pumped magnetometer specifically dedicated to these needs. It is based on a parametric resonance magnetometer architecture operated in the Earth magnetic field with closed-loop compensation of the three components of the magnetic field. It provides offset-free vector measurements in a ±70 μT range with a DC to 1 kHz bandwidth. We demonstrate a vector sensitivity up to 130 fT/√Hz, which is about ten times better than the best available fluxgate magnetometers currently available for the same targeted applications.
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Affiliation(s)
- F Bertrand
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
| | - T Jager
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
| | - A Boness
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
| | - W Fourcault
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
| | - G Le Gal
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
| | | | - J Paulet
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
| | - J M Léger
- University Grenoble Alpes, CEA, Leti, F-38000 Grenoble, France
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5
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Fourcault W, Romain R, Le Gal G, Bertrand F, Josselin V, Le Prado M, Labyt E, Palacios-Laloy A. Helium-4 magnetometers for room-temperature biomedical imaging: toward collective operation and photon-noise limited sensitivity. OPTICS EXPRESS 2021; 29:14467-14475. [PMID: 33985169 DOI: 10.1364/oe.420031] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Accepted: 03/15/2021] [Indexed: 06/12/2023]
Abstract
Optically-pumped magnetometers constitute a valuable tool for imaging biological magnetic signals without cryogenic cooling. Nowadays, numerous developments are being pursued using alkali-based magnetometers, which have demonstrated excellent sensitivities in the spin-exchange relaxation free (SERF) regime that requires heating to >100 °C. In contrast, metastable helium-4 based magnetometers work at any temperature, which allows a direct contact with the scalp, yielding larger signals and a better patient comfort. However former 4He magnetometers displayed large noises of >200 fT/Hz1/2 with 300-Hz bandwidth. We describe here an improved magnetometer reaching a sensitivity better than 50 fT/Hz1/2, nearly the photon shot noise limit, with a bandwidth of 2 kHz. Like other zero-field atomic magnetometers, these magnetometers can be operated in closed-loop architecture reaching several hundredths nT of dynamic range. A small array of 4 magnetometers operating in a closed loop has been tested with a successful correction of the cross-talks.
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6
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Yang Y, Xu M, Liang A, Yin Y, Ma X, Gao Y, Ning X. A new wearable multichannel magnetocardiogram system with a SERF atomic magnetometer array. Sci Rep 2021; 11:5564. [PMID: 33692397 PMCID: PMC7970947 DOI: 10.1038/s41598-021-84971-7] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 02/23/2021] [Indexed: 11/30/2022] Open
Abstract
In this study, a wearable multichannel human magnetocardiogram (MCG) system based on a spin exchange relaxation-free regime (SERF) magnetometer array is developed. The MCG system consists of a magnetically shielded device, a wearable SERF magnetometer array, and a computer for data acquisition and processing. Multichannel MCG signals from a healthy human are successfully recorded simultaneously. Independent component analysis (ICA) and empirical mode decomposition (EMD) are used to denoise MCG data. MCG imaging is realized to visualize the magnetic and current distribution around the heart. The validity of the MCG signals detected by the system is verified by electrocardiogram (ECG) signals obtained at the same position, and similar features and intervals of cardiac signal waveform appear on both MCG and ECG. Experiments show that our wearable MCG system is reliable for detecting MCG signals and can provide cardiac electromagnetic activity imaging.
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Affiliation(s)
- Yanfei Yang
- School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing, 100191, China
| | - Mingzhu Xu
- School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing, 100191, China
| | - Aimin Liang
- Department of Child Health Care Center, Beijing Children's Hospital, Capital Medical University, National Center for Children's Health, Beijing, 100045, China
| | - Yan Yin
- School of Instrumentation Science and Opto-Electronics Engineering, Beihang University, Beijing, 100191, China
| | - Xin Ma
- Hangzhou Innovation Institute, Beihang University, Hangzhou, 310051, China.,Research Institute for Frontier Science, Beihang University, Beijing, 100191, China
| | - Yang Gao
- Beijing Academy of Quantum Information Sciences, Beijing, 100193, China.,School of Physics, Beihang University, Beijing, 100191, China
| | - Xiaolin Ning
- Hangzhou Innovation Institute, Beihang University, Hangzhou, 310051, China. .,Research Institute for Frontier Science, Beihang University, Beijing, 100191, China.
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7
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Wang H, Wu T, Wang H, Liu Y, Mao X, Peng X, Guo H. All-optical self-oscillating 4He atomic mangnetometer with optical phase shift. OPTICS EXPRESS 2020; 28:15081-15089. [PMID: 32403541 DOI: 10.1364/oe.390375] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Accepted: 04/27/2020] [Indexed: 06/11/2023]
Abstract
An all-optical self-oscillating 4He atomic magnetometer with a large dynamic range of the magnetic field is demonstrated. This device has the advantage of the fast response of the self-oscillating magnetometer and is not affected by the systematic errors originated from the radio-frequency field. It is also free from the nonlinear Zeeman effect in large magnetic fields. We use a liquid crystal to adjust the phase shift, which is independent of frequency. Results show that our self-oscillating 4He magnetometer exhibits a response time of 0.2 ms for a step signal of 3600 nT, and the noise floor reaches 1.7 pT / Hz1/2 for frequencies from 2 Hz to 500 Hz. It can work stably in magnetic fields ranging from 2500 nT to 103000 nT. Compared with the commercial self-oscillating cesium atomic magnetometer (Scintrex, CS-3), the self-oscillating 4He atomic magnetometer has shown a better gradient tolerance in larger magnetic field. This magnetometer is ideally suited in magnetic observatories to monitor geomagnetic field requiring large dynamic range and high bandwidth.
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8
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Colombo S, Lebedev V, Tonyushkin A, Pengue S, Weis A. Imaging Magnetic Nanoparticle Distributions by Atomic Magnetometry-Based Susceptometry. IEEE TRANSACTIONS ON MEDICAL IMAGING 2020; 39:922-933. [PMID: 31478841 PMCID: PMC10536941 DOI: 10.1109/tmi.2019.2937670] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We introduce a Magnetic Particle Imaging Susceptometer (MPIS) that uses a high-sensitivity atomic magnetometer (AM) for recording the spatial distribution of fluid-suspended magnetic nanoparticles. We have evaluated the MPIS performance by one-dimensional scans of structured nanoparticle phantoms, demonstrating, in particular, resolutions of ≈2.5 mm prior to deconvolution and << 1 mm after deconvolution. Our instrument conceptually follows the general principle of Magnetic Particle Imaging (MPI) for encoding spatial distributions into magnetic flux density variations. Conversely to previously demonstrated MPI methods, MPIS works in time-space by recording time series of the sample's magnetic response including all Fourier components. The device deploys a specifically designed system of coils, a low-frequency excitation scheme, and a simple source localization algorithm. The difference of the AM's frequency response with respect to the conventional receive coil detection allows us to work at much lower driving frequencies. We demonstrate operation at frequencies on the order of 100 Hz, enabling the beneficial use of larger nanoparticles. The spatial distribution encoded into the particles' susceptibility needs a much lower excitation field amplitude compared to conventional MPI scanners. These two features make MPIS least harmful for biological samples and subjects compared to conventional MPI scanners. We also address performance characteristics and other possible applications of MPIS.
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9
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In-Situ Measurement of Electrical-Heating-Induced Magnetic Field for an Atomic Magnetometer. SENSORS 2020; 20:s20071826. [PMID: 32218349 PMCID: PMC7181036 DOI: 10.3390/s20071826] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/19/2020] [Revised: 03/20/2020] [Accepted: 03/24/2020] [Indexed: 11/17/2022]
Abstract
Electrical heating elements, which are widely used to heat the vapor cell of ultrasensitive atomic magnetometers, inevitably produce a magnetic field interference. In this paper, we propose a novel measurement method of the amplitude of electrical-heating-induced magnetic field for an atomic magnetometer. In contrast to conventional methods, this method can be implemented in the atomic magnetometer itself without the need for extra magnetometers. It can distinguish between different sources of magnetic fields sensed by the atomic magnetometer, and measure the three-axis components of the magnetic field generated by the electrical heater and the temperature sensor. The experimental results demonstrate that the measurement uncertainty of the heater’s magnetic field is less than 0.2 nT along the x-axis, 1.0 nT along the y-axis, and 0.4 nT along the z-axis. The measurement uncertainty of the temperature sensor’s magnetic field is less than 0.02 nT along all three axes. This method has the advantage of measuring the in-situ magnetic field, so it is especially suitable for miniaturized and chip-scale atomic magnetometers, where the cell is extremely small and in close proximity to the heater and the temperature sensor.
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10
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Zheng W, Su S, Zhang G, Bi X, Lin Q. Vector magnetocardiography measurement with a compact elliptically polarized laser-pumped magnetometer. BIOMEDICAL OPTICS EXPRESS 2020; 11:649-659. [PMID: 32206390 PMCID: PMC7041466 DOI: 10.1364/boe.380314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2019] [Revised: 12/17/2019] [Accepted: 12/27/2019] [Indexed: 06/10/2023]
Abstract
We report on a practical approach to vector biomagnetism measurement with an optically pumped magnetometer for measuring total magnetic field intensity. Its application to vector magnetocardiography is experimentally demonstrated with a compact elliptically polarized laser-pumped M x atomic magnetometer (EPMx OPM). The approach is proved to be effective and able to provide more complete cardiac magnetic information. The cardiac magnetic vectors are displayed in three-dimensional space in the form of magnetic vector loops. The sensor configuration and the image processing method here are expected to form further values, especially for multi-channel vector biomagnetism measurement, clinical diagnosis, and field source reconstruction.
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11
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Su S, Zhang G, Bi X, He X, Zheng W, Lin Q. Elliptically polarized laser-pumped Mx magnetometer towards applications at room temperature. OPTICS EXPRESS 2019; 27:33027-33039. [PMID: 31878377 DOI: 10.1364/oe.27.033027] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/04/2019] [Accepted: 10/14/2019] [Indexed: 06/10/2023]
Abstract
An atomic magnetometer operated with elliptically polarized light is investigated theoretically and experimentally. To explore the potential of this magnetometric configuration, the analytical form of the outgoing signal is derived. Parameters that significantly influence the performance are optimized, which lead to a sensitivity of 300 fT/Hz at 45 ∘C with a 2×2×2 cm uncoated Rb vapor cell. It is remarkable that a sensitivity of 690 fT/Hz is achieved at room temperature of 24 ∘C, which is improved by an order of magnitude compared with the conventional Mx magnetometer under its own optimized condition. The elliptically polarized approach offers attractive features for developing compact, low-power magnetometers, which are available without heating the uncoated vapor cell.
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12
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Borna A, Carter TR, DeRego P, James CD, Schwindt PDD. Magnetic Source Imaging Using a Pulsed Optically Pumped Magnetometer Array. IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT 2019; 68:493-501. [PMID: 31777404 PMCID: PMC6880808 DOI: 10.1109/tim.2018.2851458] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
We have developed a pulsed optically pumped magnetometer (OPM) array for detecting magnetic field maps originated from an arbitrary current distribution. The presented magnetic source imaging (MSI) system features 24 OPM channels, has a data rate of 500 S/s, a sensitivity of 0.8 p T / H z , and a dynamic range of 72 dB. We have employed our pulsed- OPM MSI system for measuring the magnetic field map of a test coil structure. The coils are moved across the array in an indexed fashion to measure the magnetic field over an area larger than the array. The captured magnetic field maps show excellent agreement with the simulation results. Assuming a 2D current distribution, we have solved the inverse problem, using the measured magnetic field maps, and the reconstructed current distribution image is compared to that of the simulation.
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Affiliation(s)
- Amir Borna
- Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185-1082, USA
| | - Tony R Carter
- Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185-1082, USA
| | - Paul DeRego
- Kansas City National Security Campus, 2450 Alamo Ave SE, Albuquerque, NM 87106
| | - Conrad D James
- Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185-1082, USA
| | - Peter D D Schwindt
- Sandia National Laboratories, PO Box 5800, Albuquerque, NM 87185-1082, USA
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13
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Magnetocardiography on an isolated animal heart with a room-temperature optically pumped magnetometer. Sci Rep 2018; 8:16218. [PMID: 30385784 PMCID: PMC6212485 DOI: 10.1038/s41598-018-34535-z] [Citation(s) in RCA: 32] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 10/12/2018] [Indexed: 11/08/2022] Open
Abstract
Optically pumped magnetometers are becoming a promising alternative to cryogenically-cooled superconducting magnetometers for detecting and imaging biomagnetic fields. Magnetic field detection is a completely non-invasive method, which allows one to study the function of excitable human organs with a sensor placed outside the human body. For instance, magnetometers can be used to detect brain activity or to study the activity of the heart. We have developed a highly sensitive miniature optically pumped magnetometer based on cesium atomic vapor kept in a paraffin-coated glass container. The magnetometer is optimized for detection of biological signals and has high temporal and spatial resolution. It is operated at room- or human body temperature and can be placed in contact with or at a mm-distance from a biological object. With this magnetometer, we detected the heartbeat of an isolated guinea-pig heart, which is an animal widely used in biomedical studies. In our recordings of the magnetocardiogram, we can detect the P-wave, QRS-complex and T-wave associated with the cardiac cycle in real time. We also demonstrate that our device is capable of measuring the cardiac electrographic intervals, such as the RR- and QT-interval, and detecting drug-induced prolongation of the QT-interval, which is important for medical diagnostics.
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14
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Gusev NA, Vetoshko PM, Kuzmichev AN, Chepurnova DA, Samoilova EV, Zvezdin AK, Korotaeva AA, Belotelov VI. Ultra-Sensitive Vector Magnetometer for Magnetocardiographic Mapping. BIOMEDICAL ENGINEERING-MEDITSINSKAYA TEKNIKA 2017. [DOI: 10.1007/s10527-017-9705-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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15
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Morales S, Corsi MC, Fourcault W, Bertrand F, Cauffet G, Gobbo C, Alcouffe F, Lenouvel F, Le Prado M, Berger F, Vanzetto G, Labyt E. Magnetocardiography measurements with 4He vector optically pumped magnetometers at room temperature. Phys Med Biol 2017; 62:7267-7279. [PMID: 28257003 DOI: 10.1088/1361-6560/aa6459] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
In this paper, we present a proof of concept study which demonstrates for the first time the possibility of recording magnetocardiography (MCG) signals with 4He vector optically pumped magnetometers (OPM) operated in a gradiometer mode. Resulting from a compromise between sensitivity, size and operability in a clinical environment, the developed magnetometers are based on the parametric resonance of helium in a zero magnetic field. Sensors are operated at room temperature and provide a tri-axis vector measurement of the magnetic field. Measured sensitivity is around 210 f T (√Hz)-1 in the bandwidth (2 Hz; 300 Hz). MCG signals from a phantom and two healthy subjects are successfully recorded. Human MCG data obtained with the OPMs are compared to reference electrocardiogram recordings: similar heart rates, shapes of the main patterns of the cardiac cycle (P/T waves, QRS complex) and QRS widths are obtained with both techniques.
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Affiliation(s)
- S Morales
- CEA, LETI, MINATEC Campus, F-38054 Grenoble, France
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16
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Rat Magnetocardiography Using a Flux-Gate Sensor Based on Iron Garnet Films. BIOMEDICAL ENGINEERING-MEDITSINSKAYA TEKNIKA 2016. [DOI: 10.1007/s10527-016-9628-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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17
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Ito Y, Sato D, Kamada K, Kobayashi T. Optimal densities of alkali metal atoms in an optically pumped K-Rb hybrid atomic magnetometer considering the spatial distribution of spin polarization. OPTICS EXPRESS 2016; 24:15391-15402. [PMID: 27410815 DOI: 10.1364/oe.24.015391] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
An optically pumped K-Rb hybrid atomic magnetometer can be a useful tool for biomagnetic measurements due to the high spatial homogeneity of its sensor property inside a cell. However, because the property varies depending on the densities of potassium and rubidium atoms, optimization of the densities is essential. In this study, by using the Bloch equations of K and Rb and considering the spatial distribution of the spin polarization, we confirmed that the calculation results of spin polarization behavior are in good agreement with the experimental data. Using our model, we calculated the spatial distribution of the spin polarization and found that the optimal density of K atoms is 3 × 1019 m-3 and the optimal density ratio is nK/nRb ~ 400 to maximize the output signal and enhance spatial homogeneity of the sensor property.
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18
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Colombo AP, Carter TR, Borna A, Jau YY, Johnson CN, Dagel AL, Schwindt PDD. Four-channel optically pumped atomic magnetometer for magnetoencephalography. OPTICS EXPRESS 2016; 24:15403-16. [PMID: 27410816 PMCID: PMC5025229 DOI: 10.1364/oe.24.015403] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
We have developed a four-channel optically pumped atomic magnetometer for magnetoencephalography (MEG) that incorporates a passive diffractive optical element (DOE). The DOE allows us to achieve a long, 18-mm gradiometer baseline in a compact footprint on the head. Using gradiometry, the sensitivities of the channels are < 5 fT/Hz1/2, and the 3-dB bandwidths are approximately 90 Hz, which are both sufficient to perform MEG. Additionally, the channels are highly uniform, which offers the possibility of employing standard MEG post-processing techniques. This module will serve as a building block of an array for magnetic source localization.
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Affiliation(s)
| | - Tony R. Carter
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185,
USA
| | - Amir Borna
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185,
USA
| | - Yuan-Yu Jau
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185,
USA
| | - Cort N. Johnson
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185,
USA
- Currently with the Charles Stark Draper Laboratory, 555 Technology Square, Cambridge, MA 02139,
USA
| | - Amber L. Dagel
- Sandia National Laboratories, P.O. Box 5800, Albuquerque, NM 87185,
USA
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19
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Lau S, Petković B, Haueisen J. Optimal Magnetic Sensor Vests for Cardiac Source Imaging. SENSORS (BASEL, SWITZERLAND) 2016; 16:E754. [PMID: 27231910 PMCID: PMC4934180 DOI: 10.3390/s16060754] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Revised: 05/18/2016] [Accepted: 05/18/2016] [Indexed: 12/02/2022]
Abstract
Magnetocardiography (MCG) non-invasively provides functional information about the heart. New room-temperature magnetic field sensors, specifically magnetoresistive and optically pumped magnetometers, have reached sensitivities in the ultra-low range of cardiac fields while allowing for free placement around the human torso. Our aim is to optimize positions and orientations of such magnetic sensors in a vest-like arrangement for robust reconstruction of the electric current distributions in the heart. We optimized a set of 32 sensors on the surface of a torso model with respect to a 13-dipole cardiac source model under noise-free conditions. The reconstruction robustness was estimated by the condition of the lead field matrix. Optimization improved the condition of the lead field matrix by approximately two orders of magnitude compared to a regular array at the front of the torso. Optimized setups exhibited distributions of sensors over the whole torso with denser sampling above the heart at the front and back of the torso. Sensors close to the heart were arranged predominantly tangential to the body surface. The optimized sensor setup could facilitate the definition of a standard for sensor placement in MCG and the development of a wearable MCG vest for clinical diagnostics.
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Affiliation(s)
- Stephan Lau
- Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, P.O. Box 100565, D-98684 Ilmenau, Germany.
- Biomagnetic Center, Department of Neurology, Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany.
- NeuroEngineering Laboratory, Department of Electrical and Electronic Engineering, The University of Melbourne, 3010 Parkville, Australia.
| | - Bojana Petković
- Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, P.O. Box 100565, D-98684 Ilmenau, Germany.
| | - Jens Haueisen
- Institute of Biomedical Engineering and Informatics, Ilmenau University of Technology, P.O. Box 100565, D-98684 Ilmenau, Germany.
- Biomagnetic Center, Department of Neurology, Jena University Hospital, Erlanger Allee 101, D-07747 Jena, Germany.
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Closed-Loop Control of a Neuroprosthetic Hand by Magnetoencephalographic Signals. PLoS One 2015; 10:e0131547. [PMID: 26134845 PMCID: PMC4489903 DOI: 10.1371/journal.pone.0131547] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2015] [Accepted: 06/03/2015] [Indexed: 11/24/2022] Open
Abstract
Objective A neuroprosthesis using a brain–machine interface (BMI) is a promising therapeutic option for severely paralyzed patients, but the ability to control it may vary among individual patients and needs to be evaluated before any invasive procedure is undertaken. We have developed a neuroprosthetic hand that can be controlled by magnetoencephalographic (MEG) signals to noninvasively evaluate subjects’ ability to control a neuroprosthesis. Method Six nonparalyzed subjects performed grasping or opening movements of their right hand while the slow components of the MEG signals (SMFs) were recorded in an open-loop condition. The SMFs were used to train two decoders to infer the timing and types of movement by support vector machine and Gaussian process regression. The SMFs were also used to calculate estimated slow cortical potentials (eSCPs) to identify the origin of motor information. Finally, using the trained decoders, the subjects controlled a neuroprosthetic hand in a closed-loop condition. Results The SMFs in the open-loop condition revealed movement-related cortical field characteristics and successfully inferred the movement type with an accuracy of 75.0 ± 12.9% (mean ± SD). In particular, the eSCPs in the sensorimotor cortex contralateral to the moved hand varied significantly enough among the movement types to be decoded with an accuracy of 76.5 ± 10.6%, which was significantly higher than the accuracy associated with eSCPs in the ipsilateral sensorimotor cortex (58.1 ± 13.7%; p = 0.0072, paired two-tailed Student’s t-test). Moreover, another decoder using SMFs successfully inferred when the accuracy was the greatest. Combining these two decoders allowed the neuroprosthetic hand to be controlled in a closed-loop condition. Conclusions Use of real-time MEG signals was shown to successfully control the neuroprosthetic hand. The developed system may be useful for evaluating movement-related slow cortical potentials of severely paralyzed patients to predict the efficacy of invasive BMI.
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Alem O, Sander TH, Mhaskar R, LeBlanc J, Eswaran H, Steinhoff U, Okada Y, Kitching J, Trahms L, Knappe S. Fetal magnetocardiography measurements with an array of microfabricated optically pumped magnetometers. Phys Med Biol 2015; 60:4797-811. [PMID: 26041047 DOI: 10.1088/0031-9155/60/12/4797] [Citation(s) in RCA: 51] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Following the rapid progress in the development of optically pumped magnetometer (OPM) technology for the measurement of magnetic fields in the femtotesla range, a successful assembly of individual sensors into an array of nearly identical sensors is within reach. Here, 25 microfabricated OPMs with footprints of 1 cm(3) were assembled into a conformal array. The individual sensors were inserted into three flexible belt-shaped holders and connected to their respective light sources and electronics, which reside outside a magnetically shielded room, through long optical and electrical cables. With this setup the fetal magnetocardiogram of a pregnant woman was measured by placing two sensor belts over her abdomen and one belt over her chest. The fetal magnetocardiogram recorded over the abdomen is usually dominated by contributions from the maternal magnetocardiogram, since the maternal heart generates a much stronger signal than the fetal heart. Therefore, signal processing methods have to be applied to obtain the pure fetal magnetocardiogram: orthogonal projection and independent component analysis. The resulting spatial distributions of fetal cardiac activity are in good agreement with each other. In a further exemplary step, the fetal heart rate was extracted from the fetal magnetocardiogram. Its variability suggests fetal activity. We conclude that microfabricated optically pumped magnetometers operating at room temperature are capable of complementing or in the future even replacing superconducting sensors for fetal magnetocardiography measurements.
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Affiliation(s)
- Orang Alem
- National Institute of Standards and Technology, 325 Broadway, Boulder, CO 80305, USA. University of Colorado, Boulder, CO 80309, USA
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Kamada K, Ito Y, Ichihara S, Mizutani N, Kobayashi T. Noise reduction and signal-to-noise ratio improvement of atomic magnetometers with optical gradiometer configurations. OPTICS EXPRESS 2015; 23:6976-87. [PMID: 25836917 DOI: 10.1364/oe.23.006976] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/08/2023]
Abstract
In the field of biomagnetic measurement, optically-pumped atomic magnetometers (OPAMs) have attracted significant attention. With the improvement of signal response and the reduction of sensor noise, the sensitivity of OPAMs is limited mainly by environmental magnetic noise. To reduce this magnetic noise, we developed the optical gradiometer, in which the differential output of two distinct measurement areas inside a glass cell was obtained directly via the magneto-optical rotation of one probe beam. When operating in appropriate conditions, the sensitivity was improved by the differential measurement of the optical gradiometer. In addition, measurements of the pseudo-magnetic noise and signal showed the improvement of the signal-to-noise ratio. These results demonstrate the feasibility of our optical gradiometer as an efficient method for reducing the magnetic noise.
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Xie KX, Cao SH, Liu Q, Cai WP, Huo SX, Watarai H, Li YQ. Modulation of surface plasmon coupled emission (SPCE) by a pulsed magnetic field. Chem Commun (Camb) 2015; 51:12320-3. [DOI: 10.1039/c5cc03400k] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The SPCE was modulated by a magnetic field through the interaction between plasmon and magnetic field.
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Affiliation(s)
- Kai-Xin Xie
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
- P. R. China
| | - Shuo-Hui Cao
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
- P. R. China
| | - Qian Liu
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
- P. R. China
| | - Wei-Peng Cai
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
- P. R. China
| | - Si-Xin Huo
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
- P. R. China
| | - Hitoshi Watarai
- Institute for NanoScience Design
- Osaka University
- Osaka 560-8531
- Japan
| | - Yao-Qun Li
- Department of Chemistry and the MOE Key Laboratory of Spectrochemical Analysis & Instrumentation
- College of Chemistry and Chemical Engineering
- Xiamen University
- Xiamen 361005
- P. R. China
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