Diamond sensor

Abstract

A diamond sensor includes: a diamond having a color center with an electron spin; an excitation light irradiation section that irradiates the diamond with excitation light; a transmission antenna that transmits an electromagnetic wave; a reception antenna that receives the electromagnetic wave transmitted from the transmission antenna; an electromagnetic wave irradiation section that irradiates the diamond with the electromagnetic wave received by the reception antenna; a detection section that detects emission light emitted from the color center of the diamond after the excitation light and the electromagnetic wave are irradiated to the diamond; and a composite body having a conductive member and a dielectric member, the composite body being disposed between the transmission antenna and the reception antenna and transmitting the electromagnetic wave.

Description

Technical Field

[0001] This disclosure relates to diamond sensors. This application claims priority based on Japanese Application No. 2023-178584, filed on October 17, 2023. The entire contents of that application are incorporated herein by reference. Background Technology

[0002] Diamond sensors using NV centers (hereinafter referred to as NV centers) are known. When the NV center, which contains nitrogen (i.e., N) at the substitution site of carbon (i.e., C) entering the diamond and a vacancy (i.e., V: Vacancy) adjacent to the nitrogen, becomes negatively charged, its ground state becomes a triplet state (i.e., spin S = 1). The negatively charged NV center is denoted as NV. - Center. The following records from the NV center are also from NV. - The term "NV center" is an abbreviation for "center." In its application as a sensor, a diamond containing a charged NV center is irradiated with green light and microwaves to excite the NV center, and the fluorescence emitted from the NV center is detected. A coaxial cable is used to transmit microwaves from the microwave generating device to the diamond. When a coaxial cable is used for microwave transmission, the metal conductor of the coaxial cable conducts heat while conducting electricity. This heat conduction to the object being measured affects the measurement, contributing to reduced measurement accuracy.

[0003] Non-Patent Document 1 discloses a method for transmitting microwaves via optical transmission to avoid heat intrusion into the extremely low-temperature environment of a cryostat. According to the Wiedermann-Franz law, the ratio of thermal conductivity to electrical conductivity is proportional to temperature T; therefore, it is impossible to reduce thermal conductivity while maintaining a high level of conductivity in a metallic conductor. Consequently, there is a limit to the reduction of heat intrusion as long as a metallic conductor is used. Therefore, Non-Patent Document 1 discloses the following: microwaves are electro-optically converted, transmitted via optical fiber, and then photoelectrically converted after transmission, thereby further reducing the amount of heat intrusion compared to its limit, reducing noise associated with heat intrusion, and improving the performance of a quantum computer.

[0004] Existing technical documents Non-patent literature Non-patent literature 1: F. Lecocq et al., “Control and readout of asuperconducting qubit using a photonic link”, Nature, Vol. 591, 25 March 2021, 575. Summary of the Invention

[0005] One aspect of this disclosure relates to a diamond sensor comprising: a diamond having a color center with electron spin; an excitation light irradiation unit for irradiating the diamond with excitation light; a transmitting antenna for transmitting electromagnetic waves; a receiving antenna for receiving electromagnetic waves transmitted from the transmitting antenna; an electromagnetic wave irradiation unit for irradiating the diamond with electromagnetic waves received by the receiving antenna; a detection unit for detecting emitted light from the color center of the diamond after the excitation light and electromagnetic waves have been irradiated onto the diamond; and a composite having a conductive member and a dielectric member, the composite being disposed between the transmitting antenna and the receiving antenna for transmitting electromagnetic waves. Attached Figure Description

[0006] Figure 1 This is a schematic diagram illustrating the general configuration of the diamond sensor according to an embodiment of the present disclosure.

[0007] Figure 2 It means Figure 1 The diagram shows the composition of the complex.

[0008] Figure 3 It is a three-dimensional diagram representing a flat conductive component.

[0009] Figure 4A This is a front view showing a patch antenna for receiving microwaves.

[0010] Figure 4B This is a right view showing a patch antenna for receiving microwaves.

[0011] Figure 5 It means that it was used. Figure 1 The diagram shows the timing of the excitation light and electromagnetic wave irradiation, as well as the timing of the emission light measurement, during the measurement of the diamond sensor.

[0012] Figure 6 It is a graph that schematically shows the relationship between the observed signal strength (i.e., the intensity of emitted light) and the frequency of electromagnetic waves (i.e., microwaves).

[0013] Figure 7 This is a three-dimensional diagram representing a horn antenna that transmits microwaves.

[0014] Figure 8 It is a cross-sectional view showing the configuration of the composite material arranged inside the insulator.

[0015] Figure 9 It is a three-dimensional diagram showing the structure of the microwave transmission path used in the experiment.

[0016] Figure 10A This is a front view showing the composition of the complex used in the experiment.

[0017] Figure 10B This is a right-hand view showing the composition of the complex used in the experiment.

[0018] Figure 11 It is a graph showing the results of experiments conducted by changing the spacing of multiple conductive components.

[0019] Figure 12 It is a graph showing the results of experiments conducted by changing the length of the conductive component. Detailed Implementation

[0020] [The problem this disclosure aims to solve] As disclosed in Non-Patent Document 1, when transmitting microwaves via optical transmission, an electrical-to-optical conversion device and an optical-to-electrical conversion device are required. Furthermore, both coaxial cable-based and optical-based microwave transmission are difficult to use in high-voltage environments. That is, the coaxial cable and conversion device may be damaged due to the instantaneous high voltage and large current generated by discharge, and also due to the strong electromagnetic waves generated along with it. As a countermeasure, spatial transmission of microwaves via antennas is considered. However, in spatial microwave transmission, the microwaves extend beyond their wavelength, thus resulting in significant transmission loss.

[0021] Therefore, the purpose of this disclosure is to provide a diamond sensor capable of spatial transmission of electromagnetic waves with reduced transmission loss.

[0022] [The Effects of This Disclosure] According to this disclosure, a diamond sensor capable of spatial transmission of electromagnetic waves with reduced transmission loss can be provided.

[0023] [Description of embodiments of this disclosure] Embodiments of this disclosure are described below. At least some of the embodiments described below may be combined arbitrarily.

[0024] (1) The diamond sensor according to the first aspect of this disclosure includes: a diamond having a color center with electron spin; an excitation light irradiation unit for irradiating the diamond with excitation light; a transmitting antenna for transmitting electromagnetic waves; a receiving antenna for receiving electromagnetic waves transmitted from the transmitting antenna; an electromagnetic wave irradiation unit for irradiating the diamond with electromagnetic waves received by the receiving antenna; a detection unit for detecting the emitted light from the color center of the diamond after the excitation light and electromagnetic waves are irradiated onto the diamond; and a composite having a conductive member and a dielectric member, the composite being disposed between the transmitting antenna and the receiving antenna to transmit electromagnetic waves. Thus, spatial transmission of electromagnetic waves (e.g., microwaves) with reduced transmission loss is possible. Furthermore, it is not damaged even under high voltage conditions, and can measure magnetic fields and electric fields with high precision.

[0025] (2) Alternatively, in (1) above, the conductive member is a line whose length in the first direction is longer than the length in any direction orthogonal to the first direction, and is arranged such that the first direction is along the electric field direction of the electromagnetic wave. The wavelength of the electromagnetic wave is set to λ, and the electrical length of the conductive member in the first direction is more than 0.7 times and less than 1.1 times λ / 2. This suppresses the transmission of electromagnetic waves beyond their wavelength. Therefore, transmission loss is reduced, and electromagnetic waves are transmitted efficiently. Furthermore, electrical length refers to the length obtained by converting the physical length to take into account the transmission speed of the electromagnetic wave. The transmission speed of electromagnetic waves is slower in matter than in a vacuum (the wavelength becomes shorter), therefore the electrical length is longer than the physical length.

[0026] (3) Alternatively, in (1) or (2) above, multiple conductive components are arranged in the direction of electromagnetic wave propagation, the wavelength of the electromagnetic wave is set as λ, and the electrical length between two adjacent conductive components is more than 0.1 times and less than 1.7 times λ / 4. This further suppresses the propagation of the transmitted electromagnetic wave. Consequently, transmission loss can be further reduced, and electromagnetic waves can be transmitted more efficiently.

[0027] (4) Alternatively, in any of (1) to (3) above, the dielectric component may include a heat-insulating component or an electrically insulating component. This can suppress heat conduction to the diamond.

[0028] (5) Alternatively, in any of (1) to (4) above, the dielectric component may include air and a dielectric material other than air. This further suppresses heat conduction to diamond.

[0029] (6) Alternatively, in any of (1) to (5) above, the dielectric component may include a porous component. This makes it possible to reduce the weight of the electromagnetic wave transmission path.

[0030] (7) Alternatively, in any of (1) to (6) above, the dielectric component comprises polyimide, polypropylene, or alumina. This simplifies the fabrication of the composite and further suppresses heat conduction to the diamond. Furthermore, it facilitates the adjustment of the dielectric constant of the dielectric component.

[0031] (8) Alternatively, in (6) or (7) above, the dielectric component includes a dielectric with independent air bubbles. Thus, moisture (i.e., water vapor) will not penetrate into the air bubbles, which can suppress the change of the dielectric constant of the dielectric component and enable stable transmission of electromagnetic waves.

[0032] (9) Alternatively, in (8) above, the wavelength of the electromagnetic wave can be set to λ, and the size of the independent bubble can be greater than λ / 200 and less than λ / 50. This can improve the transmittance of the electromagnetic wave and reduce transmission loss.

[0033] (10) Alternatively, in any of (1) to (9) above, the composite is disposed inside the insulator. As a result, the configuration of the electromagnetic wave transmission path becomes easier.

[0034] (11) Alternatively, in (10) above, the dielectric component is air. Therefore, it is not necessary to provide a dielectric component other than air, and the formation of the electromagnetic wave transmission path becomes easier.

[0035] (12) Alternatively, in any of (1) to (11) above, the receiving antenna is a patch antenna. As a result, the design freedom of the electromagnetic wave receiving antenna increases.

[0036] (13) Alternatively, in any of (1) to (12) above, the transmitting antenna can be a horn antenna or a patch antenna. This allows for the transmission of electromagnetic waves with good directionality, thereby improving the detection accuracy of the diamond sensor.

[0037] (14) Alternatively, in any of (1) to (13) above, the electromagnetic wave transmitted from the transmitting antenna is a microwave, millimeter wave, or submillimeter wave. Thus, it is possible to transmit electromagnetic waves of frequencies corresponding to the type of color center used, not limited to NV centers, and to realize sensors using Si-V centers, Ge-V centers, or Sn-V centers, etc.

[0038] [Details of the embodiments disclosed herein] In the following embodiments, the same reference numerals are used to refer to the same parts. Their names and functions are also the same. Therefore, detailed descriptions of them will not be repeated.

[0039] Reference Figure 1 The diamond sensor 100 disclosed herein includes a diamond element 102, an excitation light generating unit 108, a filter 110, a focusing element 112, an optical waveguide 114, an LPF (Long Pass Filter) 116, and a light detection unit 118. The diamond sensor 100 also includes a transmitting unit 120, a composite unit 122, a receiving unit 124, and an electromagnetic wave irradiation unit 126. A control unit 130 and an electromagnetic wave generating unit 132 are disposed externally on the diamond sensor 100.

[0040] The control unit 130 includes a CPU (Central Processing Unit) and a storage unit (neither shown). The processing performed by the control unit 130, which will be described later, is achieved by the CPU reading and executing programs pre-stored in the storage unit.

[0041] The excitation light generating unit 108 is controlled by the control unit 130 to generate NV centers (i.e., NV) for exciting diamond, which will be described later.- The excitation light 104 is emitted from the center. The control unit 130 supplies a voltage to the excitation light generating unit 108 at a predetermined time to cause the excitation light generating unit 108 to emit light. The excitation light is green light (wavelength approximately 490 nm to 560 nm). The excitation light is, for example, a laser. The excitation light generating unit 108 is, for example, a semiconductor laser (e.g., emitting light with a wavelength of 532 nm).

[0042] Filter 110 is an element used to separate the excitation light 104 incident from the excitation light generating section 108 from the light emitted from the diamond element 102 (i.e., fluorescence 106), as described later. For example, filter 110 may be a short-pass filter that allows light with wavelengths below a predetermined wavelength to pass through while blocking (i.e., reflecting) light with wavelengths larger than the predetermined wavelength, or a band-pass filter that allows light with wavelengths within a predetermined wavelength range to pass through while blocking (i.e., reflecting) light with wavelengths outside the predetermined wavelength range. Generally, the wavelength of the excitation light is shorter than that of the fluorescence, therefore such a filter is used. Filter 110 may be, for example, a dichroic mirror.

[0043] The focusing element 112 focuses the excitation light 104 incident from the filter 110. The focusing element 112 is used to input as much of the excitation light 104, which is diffused and output from the filter 110, into the light input end of the optical waveguide 114 as possible.

[0044] The optical waveguide 114 includes a medium for transmitting light and transmits light bidirectionally. That is, excitation light incident on the first end disposed on the excitation light generating section 108 side is transmitted to the second end disposed on the diamond element 102 side. In addition, the emitted light (i.e., fluorescence 106) incident on the diamond element 102 at the second end is transmitted to the first end. The optical waveguide 114 is, for example, an optical fiber.

[0045] The diamond element 102 includes an NV center. Excitation light 104 transmitted through the optical waveguide 114 irradiates the diamond element 102.

[0046] The electromagnetic wave irradiation unit 126 irradiates electromagnetic waves (e.g., microwaves) onto the diamond element 102. The electromagnetic wave irradiation unit 126 is, for example, a coil containing an electrical conductor. The source of the electromagnetic waves irradiated from the electromagnetic wave irradiation unit 126 onto the diamond element 102 is the electromagnetic wave generating unit 132. That is, the electromagnetic waves output from the electromagnetic wave generating unit 132 are radiated into the air as electromagnetic waves via the transmitting unit 120. The radiated electromagnetic waves are transmitted through the composite 122, which functions as a transmission path, and are received by the receiving unit 124 and transmitted to the electromagnetic wave irradiation unit 126.

[0047] Reference Figure 2 The composite 122 includes a plurality of conductive members 200 and a plurality of dielectric members 202, and is disposed between the transmitting unit 120 and the receiving unit 124. For convenience, in Figure 2 The orthogonal axes (XYZ axes) are shown. Dielectric members 202 are arranged between adjacent conductive members 200, between the transmitting section 120 and its nearest conductive member 200, and between the receiving section 124 and its nearest conductive member 200. The conductive member 200 is, for example, a linear conductor (i.e., an electrical conductor) of length L1. The conductive member 200 is, for example, a copper wire. Each conductive member 200 is arranged with its length direction aligned with the electric field direction of the electromagnetic wave emitted from the transmitting section 120. The spacing D1 between adjacent conductive members 200 is constant. Figure 2 In this context, the direction of electromagnetic wave propagation is defined as the Y-axis, and the direction of the electric field, orthogonal to the propagation direction, is defined as the X-axis. Furthermore, "linear" refers to the length of the first direction (in...). Figure 2 The shape (with the X-axis as the center) is longer than the length of any direction orthogonal to the first direction (e.g., the Y-axis and Z-axis). For example, the diameter φ of the conductive member 200 is 0.05 mm or more and 1.0 mm or less, and φ / L1 < 1. Thus, the composite 122 is able to transmit electromagnetic waves (e.g., microwaves) with reduced transmission losses.

[0048] By setting the wavelength of the electromagnetic wave to be transmitted as λ, the electrical length of the conductive member 200 in the direction L1 (X-axis direction) is, for example, more than 0.7 times and less than 1.1 times λ / 2. This suppresses the possibility of the electromagnetic wave transmitted by the composite 122 extending beyond its wavelength. Therefore, as described below, transmission loss of the electromagnetic wave can be reduced, and the electromagnetic wave can be transmitted efficiently.

[0049] The electrical length of the spacing D1 between adjacent conductive members 200 is, for example, more than 0.1 times and less than 1.7 times λ / 4. This further suppresses the propagation of electromagnetic waves transmitted by the composite 122. Consequently, transmission loss of electromagnetic waves can be further reduced, and electromagnetic waves can be transmitted more efficiently.

[0050] The electrical length of the conductive member 200 in the length L1 direction can be more than 0.8 times and less than 1.0 times λ / 2, or more than 0.8 times and less than 0.95 times λ / 2. The electrical length of the interval D1 between adjacent conductive members 200 can be more than 0.3 times and less than 1.3 times λ / 4, or more than 0.5 times and less than 1.0 times λ / 4. This further reduces electromagnetic wave transmission loss.

[0051] The dielectric component 202 includes, for example, a heat-insulating component or an electrically insulating component. This suppresses heat conduction from the transmitting unit 120 to the receiving unit 124, i.e., heat conduction to the diamond element 102. Therefore, the diamond sensor 100 can detect magnetic fields and electric fields with high precision.

[0052] The dielectric component 202 may, for example, include air and dielectrics other than air. This further suppresses heat conduction from the transmitting section 120 to the diamond element 102.

[0053] The dielectric component 202 may also comprise a porous component such as a sponge with multiple fine pores. This allows the composite 122, which functions as a transmission path for electromagnetic waves, to be lightweight. The porous component may also be a foamed component in which gas is finely dispersed in a synthetic resin and bubbles are formed through foaming. Examples of synthetic resins include polyethylene, polystyrene, polypropylene, or polyurethane.

[0054] The bubbles in the foamed component can be either independent or continuous. Continuous bubbles refer to bubbles (pores) connected to other bubbles, while independent bubbles are those not connected to other bubbles. The dielectric component 202 can also contain dielectrics with independent bubbles. This prevents moisture (i.e., water vapor) from penetrating the bubbles, suppressing changes in the dielectric constant of the dielectric component and enabling stable transmission of electromagnetic waves. If the wavelength of the transmitted electromagnetic wave is λ, the size of the independent bubble can be λ / 200 or more and λ / 50 or less. This improves the transmittance of the electromagnetic wave and reduces transmission loss. Alternatively, the size of the independent bubble can be λ / 160 or more and λ / 80 or less, or λ / 130 or more and λ / 100 or less.

[0055] The dielectric component 202 may also comprise polyimide, polypropylene, or aluminum oxide (Al2O3). This simplifies the fabrication of the composite 122 and further suppresses heat conduction from the transmitting section 120 to the diamond element 102. Furthermore, adjusting the dielectric constant of the dielectric component 202 becomes easier.

[0056] The above description focuses on the case where the conductive member 200 is linear, but it is not limited to this. The conductive member 200 can also be plate-shaped. (See reference...) Figure 3 The conductive component 200 can be, for example, a rectangle (including a square with L2 = L3) or a circular plate (with a thickness length of L4) with lengths L2 and L3 on both sides. Figure 3 It shows the relationship with Figure 2 Orthogonal axes with the same configuration. For example, L4 is above 0.1 μm and below 500 μm.

[0057] The wavelength of the electromagnetic wave to be transmitted is set to λ. The electrical length L2 in the X-axis direction (electric field direction) is, for example, more than 0.7 times and less than 1.1 times λ / 2. The length L3 can be at least as large as the length L2 (i.e., L3 / L2≤1). This suppresses the electromagnetic wave transmitted by the composite 122 from extending beyond its wavelength. Therefore, as described below, transmission loss of the electromagnetic wave can be reduced, and the electromagnetic wave can be transmitted efficiently. The electrical length L2 in the X-axis direction (electric field direction) can be more than 0.8 times and less than 1.0 times λ / 2, or more than 0.8 times and less than 0.95 times λ / 2.

[0058] The transmitting unit 120 and the receiving unit 124 are, for example, Figure 4A as well as Figure 4B The patch antenna shown is a microstrip antenna. This patch antenna includes a first conductive plate 220 and a second conductive plate 222. The first conductive plate 220 and the second conductive plate 222 are each formed into a flat plate shape from a conductive component such as copper. For example, the first conductive plate 220 is a square with one side of length L5, and the second conductive plate 222 is a square with one side of length L6. The first conductive plate 220 and the second conductive plate 222 are arranged separately from each other (spaced D2) with their corresponding sides parallel to each other and aligned with their central axes perpendicular to their respective faces. The second conductive plate 222 serves as ground, and the first conductive plate 220 functions as a radiating or receiving element for electromagnetic waves. That is, the front surface of the patch antenna is the side of the first conductive plate 220, and the back (inside) side is the side of the second conductive plate 222. The wavelength of the transmitted or received electromagnetic wave is set as λ, and one side of the first conductive plate 220 is formed with L5 = λ / 2. A dielectric material (substrate, etc.) may also be disposed between the first conductive plate 220 and the second conductive plate 222.

[0059] In Figure 4A as well as Figure 4B When the patch antenna shown is used as a transmitting antenna, for example, a signal is supplied from power point A to the first conductive plate 220. Figure 4A as well as Figure 4B The orthogonal axes shown are Figure 2 The orthogonal axes shown correspond to each other, indicating Figure 4A as well as Figure 4B The patch antenna shown is used as Figure 2The patch antenna configuration (i.e., orientation) in the case of the transmitting unit 120 is shown. Power supply point A is a point on the surface (inside) of the first conductive plate 220 that faces the second conductive plate 222. For example, a through-hole (not shown) is formed in the second conductive plate 222 so that a signal line can be connected at power supply point A through the through-hole without contacting the second conductive plate 222. For example, an SMA (Sub Miniature Type A) coaxial connector (not shown) is disposed in the through-hole of the second conductive plate 222, and the signal pins of the connector are connected to power supply point A. The ground of the connector is connected to the second conductive plate 222. Thus, the first conductive plate 220 functions as a radiating element for electromagnetic waves. Figure 4A The power supply point A shown is displaced from the center point O in the X-axis direction, therefore the electric field direction of the electromagnetic wave emitted from the first conductive plate 220 is in the X-axis direction. By adjusting the length L7 between the power supply point A and the center point O of the first conductive plate 220, the impedance of the patch antenna can be matched with the impedance (e.g., 50Ω) of the power supply path (coaxial cable, etc.).

[0060] In Figure 4A as well as Figure 4B When the patch antenna shown is used as a receiving antenna, a wire for extracting the signal is connected at power supply point A, and this wire is then connected to a signal detector. Figure 4A as well as Figure 4B The patch antenna shown is used as Figure 2 In the case of the receiving unit 124 shown, the first conductive plate 220 is configured to be opposite the transmitting unit 120.

[0061] By using Figure 4A as well as Figure 4B The patch antenna shown serves as the receiver 124 (receiving antenna), increasing the design freedom of the electromagnetic wave receiving antenna. As the transmitter 120 (transmitting antenna), by using... Figure 4A as well as Figure 4B The patch antenna shown can transmit electromagnetic waves with good directionality, which can improve detection accuracy.

[0062] The excitation light and electromagnetic wave irradiation of the diamond element 102 are controlled by the control unit 130, for example, in Figure 5The timing is shown. The horizontal axis represents the common time t. That is, the control unit 130 controls the excitation light generating unit 108 to output excitation light at a predetermined time (e.g., time t1) at a predetermined time. The control unit 130 controls the electromagnetic wave generating unit 132 to output electromagnetic waves at a predetermined time (e.g., time t2) at a predetermined time. The pulse sequence at time t2 can be adjusted according to the diamond used (e.g., the alignment of the orientation of multiple NV centers) and the observed signal (i.e., the signal affected by the spin state of the NV centers). Thus, the excitation light and electromagnetic waves are combined in time and space to irradiate the diamond element 102. The control unit 130 takes in the output signal of the light detection unit 118 input from the light detection unit 118 at a predetermined time (e.g., within period t3) and stores it in the storage unit inside the control unit 130.

[0063] The NV center has a diamond crystal structure where carbon (C) atoms are replaced by nitrogen (N) atoms, and no adjacent carbon atoms are present (i.e., vacancies (V)). The NV center transitions from the ground state to an excited state due to green light (e.g., a 532 nm laser) with wavelengths of approximately 490 nm to 560 nm, emitting red light (e.g., 637 nm fluorescence) with wavelengths of approximately 630 nm to 800 nm, and then returns to the ground state. The NV center in the state of trapping one electron (i.e., NV...) - Under these conditions, the magnetic quantum number m is formed. s Given a spin triplet state with -1, 0, and +1, if a magnetic field exists, then m s The energy levels of the ±1 states separate according to the magnetic field strength (i.e., Zeeman separation). Irradiating the center of NV with microwaves of approximately 2.87 GHz causes m... s The state transition from 0 to m is... s After reaching a state of ±1 (i.e., electron spin resonance), it is excited by irradiation with green light. Consequently, the transition back to the ground state includes a non-emissive transition (i.e., fluorescence), thus the observed intensity of the emitted light decreases. Therefore, a valley (i.e., a decrease in signal intensity) is observed in the ESR (Electron Spin Resonance) spectrum. As described above, the control unit 130 controls the excitation light generation unit 108 and the electromagnetic wave generation unit 132, for example, by measuring... Figure 6 The spectrum is as shown. The observed valley spacing, i.e., the frequency difference Δf, depends on the magnetic field strength at the location of the diamond element 102.

[0064] The specific spectral measurement is performed as follows: Light (i.e., fluorescence) diffused from the diamond element 102 is incident on the second end of the optical waveguide 114. The light (i.e., fluorescence) incident on the optical waveguide 114 propagates within the optical waveguide 114 and is output from the first end of the optical waveguide 114. The light (i.e., fluorescence) output from the first end of the optical waveguide 114 is parallelized by the focusing element 112, passes through the filter 110 and the LPF 116, and is incident on the photodetector 118. The photodetector 118 then detects light with a frequency corresponding to the magnetic field at the location where the diamond element 102 is positioned. The photodetector 118 generates and outputs an electrical signal corresponding to the incident light. As described above, the output signal of the photodetector 118 is acquired by the control unit 130.

[0065] Through the above, the control unit 130 irradiates the diamond element 102 with excitation light, scans the frequency of electromagnetic waves to irradiate the diamond element 102, and can acquire the light (i.e., fluorescence) emitted from the diamond element 102 as an electrical signal output from the photodetector 118. Based on the observed frequency difference Δf, the magnetic field strength at the location of the diamond element 102 can be calculated. That is, the diamond sensor 100 functions as a magnetic sensor. Furthermore, the diamond sensor 100 is not limited to magnetic fields, and can also be used as a sensor for detecting physical quantities related to magnetic fields, such as magnetization, electric field, voltage, current, temperature, and pressure.

[0066] Electromagnetic waves irradiated onto the diamond element 102 propagate through space via the transmitting unit 120, the composite 122, and the receiving unit 124, and are transmitted to the electromagnetic wave irradiation unit 126. Therefore, even in high-voltage devices or the like equipped with the transmitting unit 120, the composite 122, and the receiving unit 124, if high voltage and large current are generated due to discharge, the device for transmitting electromagnetic waves (i.e., the electromagnetic wave generating unit 132 and the control unit 130) will not be damaged.

[0067] Furthermore, if optical fiber is used in the optical waveguide 114, the diamond element 102 and the focusing element 112, which are the main components of the sensor, are formed of electrical insulators. Therefore, even if they are placed in high-voltage equipment, damage caused by discharge or the like can be suppressed. Additionally, the excitation light generating unit 108 and the light detection unit 118 can be positioned away from the high-voltage environment via the optical waveguide 114. Thus, the diamond sensor 100 enables the safe measurement of magnetic fields and the like in high-voltage environments.

[0068] The above description describes the use of a patch antenna in the transmitting unit 120, but it is not limited to this. The transmitting unit 120 may, for example, be... Figure 7The waveguide horn antenna shown is a horn antenna (hereinafter simply referred to as a horn antenna). The horn antenna includes an adapter section 300, a horn section 302, and a connector 304. The connector 304 is an SMA-type coaxial connector that supplies externally supplied electromagnetic waves (i.e., microwaves) to the adapter section 300. The adapter section 300 is a waveguide formed of a conductive material (e.g., aluminum alloy), and its cross-section (hereinafter referred to as the cut) perpendicular to the transmission direction of the electromagnetic wave has a constant shape. The electromagnetic waves supplied to the adapter section 300 are transmitted to the horn section 302. The horn section 302 is formed of a conductive material (e.g., aluminum alloy) and is shaped as a tapered section with a gradually widening cut in order to match free space and suppress reflections. The horn antenna is directional in the direction of its central axis 306. Figure 7 The horn antenna shown is a rectangle with an opening of length L8 and a height of length L9 in the horn section 302, and the adapter section 300 and the horn section 302 together have a total length of length L10. By using a horn antenna in the transmitting section 120, electromagnetic waves can be transmitted directionally to the receiving section 124 (e.g., a patch antenna). Therefore, the detection accuracy of the diamond sensor can be improved.

[0069] Furthermore, the shape of the flared portion 302 can be any cone shape with a gradually widening cut, and is not limited to any particular shape. Figure 7 The shape shown is arbitrary. For example, the shape of the horn part 302 can also be conical, pyramidal with the same height (L9) as the adapter part 300, or pyramidal with the same height (L8) as the adapter part 300, etc.

[0070] Composite 122 can also be configured within the insulator. (See reference...) Figure 8 Inside insulator 260, with Figure 2 Similarly, multiple conductive members 250 are arranged. For example, each conductive member 250 is a line of the same length, and the spacing between adjacent conductive members 250 is constant. Each conductive member 250 is fixed to the inner wall surface of the insulator 260 by a support member (not shown). A dielectric member 252 (specifically, air) exists between adjacent conductive members 250. Figure 8 The insulator shown is 260 on the left and right, and Figure 2 It is similarly configured with a transmitting unit and a receiving unit. Figure 8 In, with Figure 2 Similarly, the orthogonal axes are shown. Each conductive member 250 is arranged with its length direction along the X-axis (the direction of the electric field of the electromagnetic wave).

[0071] Electromagnetic waves (e.g., microwaves) emitted from the transmitting unit are transmitted by a composite comprising a conductive member 250 and a dielectric member 252, and received by a receiving unit. The length of the conductive member 250 is... Figure 2The conductive member 200 shown is similarly formed, thereby suppressing the diffusion of electromagnetic waves emitted from the transmitting part, reducing transmission loss, and transmitting electromagnetic waves more efficiently. Furthermore, by configuring insulators in electrical equipment, the transmission path of electromagnetic waves can be easily configured. By using air as the dielectric member 252 between adjacent conductive members 250, it is not necessary to provide additional dielectric members other than air, making the formation of the electromagnetic wave transmission path easier.

[0072] The above description focuses on the use of diamond NV centers, but is not limited to this. Any diamond element possessing a color center with electron spin is acceptable. A color center with electron spin is a center that forms a spin triplet state and emits light upon excitation. Besides NV centers, color centers with electron spin are also known to exist in silicon-vacancy centers (i.e., Si-V centers), germanium-vacancy centers (i.e., Ge-V centers), and tin-vacancy centers (i.e., Sn-V centers). Therefore, diamond elements containing these can be used instead of diamond elements containing NV centers to form diamond sensors.

[0073] Depending on the energy level of the color center, the wavelengths of the excitation light and emitted light (i.e., fluorescence), as well as the frequency of the resonantly excited electromagnetic waves, vary. As mentioned above, microwaves are used for NV centers. In the cases of Si-V, Ge-V, and Sn-V centers, millimeter waves (e.g., 30 GHz to 300 GHz) or submillimeter waves (e.g., 300 GHz to 3 THz) with frequencies higher than microwaves (e.g., 1 GHz to 30 GHz) are used for irradiation. For example, millimeter waves of approximately 48 GHz are used for Si-V centers, and submillimeter waves of approximately 850 GHz are used for Sn-V centers.

[0074] That is, the electromagnetic waves transmitted from the transmitting unit 120 (transmitting antenna) can be microwaves, millimeter waves, or submillimeter waves. Thus, by transmitting electromagnetic waves at frequencies corresponding to the type of color center used, it is possible to realize sensors that use Si-V centers, Ge-V centers, or Sn-V centers, etc., which are not limited to NV centers.

[0075] In the above description, the conductive member 200 is described as being linear or rectangular flat, but it is not limited to this. For example, the conductive member 200 can be loop-shaped or circular plate-shaped. Their perimeter (electrical length) only needs to be at least 0.7 times and less than 1.0 times the wavelength λ of the microwave in the conductive member 200.

[0076] In the above description, the case where dielectric members 202 are arranged between adjacent conductive members 200 has been explained, but this is not a limitation. For example, insulating gas can be arranged around multiple conductive members 200, and a support structure for each conductive member 200 can be provided to electrically insulate adjacent conductive members 200. Furthermore, in microwave transmission between extreme environments where it is difficult to utilize coaxial cable through-terminals (through connectors) and environments where measuring instruments are installed, Figure 2 In the configuration shown, the dielectric member 202 may also be, for example, a ceramic sheet or an FRP (Fiber Reinforced Plastics) sheet.

[0077] Example 1 The effectiveness of the electromagnetic wave transmission path of this disclosure is illustrated below through examples. (Refer to...) Figure 9 ,like Figure 2 As shown, this forms the microwave transmission path. Figure 9 In the middle, the transmitting unit 400 and the receiving unit 402 are Figure 4A as well as Figure 4B The patch antenna shown corresponds to the transmitting unit 120 and the receiving unit 124, respectively. Multiple conductive members 406 correspond to multiple conductive members 200. Multiple conductive members 406 are held at equal intervals by support members 404. The support members 404 are made of a 0.5 mm thick sheet of polypropylene.

[0078] The conductive member 406 is a wire with a diameter of 0.45 mm. The frequency of the transmitted and received microwaves is set to approximately 2.87 GHz, which is the magnetic resonance frequency of the NV center of the diamond. The length of each conductive member 406 is set to 45 mm, and the spacing between adjacent conductive members 406 is set to 25 mm. With these values, air exists between adjacent conductive members 406 as a dielectric element. Therefore, the wavelength of the microwave is set to λ, the electrical length of the conductive member 406 is approximately λ / 2, and the electrical length of the spacing between adjacent conductive members 406 is approximately λ / 4.

[0079] Reference Figure 4A as well as Figure 4B The transmitting unit 400 and the receiving unit 402 use a first conductive plate 220 and a second conductive plate 222, respectively. Copper foil with a thickness of 0.05 mm is used, with L5 = 40 mm, L6 = 80 mm, and D2 = 5 mm. The position of the power supply point A is set to L7 = 6 mm. The distance between the transmitting unit 400 and the receiving unit 402 is set to 1 m.

[0080] exist Figure 9In the configuration shown, microwaves with a frequency of 2.87 GHz are emitted from the transmitting unit 400, and the signal received by the receiving unit 402 is measured using a vector network analyzer (NanoVNA). The result is that the microwave transmission loss is 8 dB. Furthermore, as a comparative example, without the conductive member 406 disposed between the transmitting unit 400 and the receiving unit 402, microwaves with a frequency of 2.87 GHz are emitted from the transmitting unit 400, and the signal received by the receiving unit 402 is measured using a vector network analyzer. The result is that the microwave transmission loss is 26 dB. Based on this result, by distributing the conductive member 406 between the transmitting unit 400 and the receiving unit 402, the microwave transmission loss can be reduced by 18 (=26-8) dB (reduced to approximately 1 / 63). That is, microwave transmission efficiency can be increased by approximately 63 times. Therefore, microwave diffusion is suppressed.

[0081] Example 2 A dielectric component for heat insulation was placed between the transmitting and receiving sections, and experiments were conducted. (Refer to...) Figure 10A as well as Figure 10B A conductive member 420 of length L11 is used, and a dielectric member 422 is disposed between adjacent conductive members 420. Figure 10B The microwave transmission path shown has left and right configurations. Figure 9 The transmitting unit 400 and receiving unit 402 are shown. The conductive member 420 uses copper wire with a length L11 of 40 mm and a diameter of 0.45 mm. The dielectric member 422 uses foamed polyethylene with a thickness Th of 25 mm. That is, the spacing between adjacent conductive members 420 is approximately 30 mm. The distance between the transmitting unit 400 and the receiving unit 402 is approximately 0.2 m.

[0082] Microwaves radiated from the transmitting patch antenna at a frequency of 2.87 GHz were measured by a vector network analyzer, and the signal received by the receiving patch antenna was also measured. The result showed that the microwave transmission loss was 8 dB. As a comparative example, only a dielectric member 422 was placed between the transmitting and receiving patch antennas, without the conductive member 420, and measurements were similarly performed using a vector network analyzer. The result showed that the microwave transmission loss was 15 dB. Based on this result, by placing both the conductive member 420 and the dielectric member 422 between the transmitting unit 400 and the receiving unit 402, the microwave transmission loss could be reduced by 7 (=15-8) dB (reduced to approximately 1 / 5). That is, microwave transmission efficiency was approximately 5 times higher. Therefore, microwave spread was suppressed.

[0083] Example 3 Experiments were conducted by varying the spacing of multiple conductive components. Specifically, in Figure 10A as well as Figure 10BIn the configuration shown, the number of conductive members 420 has been changed. The dielectric member 422 uses the aforementioned foamed polyethylene (Th = 25 mm). Depending on the number of conductive members 420, the spacing may differ from an integer multiple of 25 mm; therefore, the foamed polyethylene is appropriately cut into half-thickness pieces for use. The distance between the transmitting patch antenna and the receiving patch antenna is 0.2 m. Microwaves at a frequency of 2.87 GHz are emitted from the transmitting patch antenna, and the signal received by the receiving patch antenna is measured using a vector network analyzer. The results are shown below. Figure 11 .

[0084] exist Figure 11 In the diagram, the vertical axis represents transmission loss (dB units), and the horizontal axis represents the spacing between conductive components (m units). Figure 11 In this context, the wavelength of microwaves with a frequency of 2.87 GHz is denoted as λ, and arrows are used to indicate the intervals corresponding to λ, λ / 2, and λ / 4. Figure 11 In the diagram, the rightmost point represents the measurement results without conductive component 420. The points from the second point from the right to the left represent the measurement results with 1, 5, 6, 9, and 17 conductive components 420 respectively. Figure 11 It can be seen that when the spacing between adjacent conductive components 420 is approximately λ / 2 or less, the microwave transmission loss is drastically reduced, enabling efficient microwave transmission. It can also be seen that when the spacing between adjacent conductive components 420 is approximately λ / 4 or less, the microwave transmission loss is further reduced, enabling even more efficient microwave transmission. Furthermore, it can be seen that simply placing a conductive component 420 between the transmitting patch antenna and the receiving patch antenna can reduce transmission loss.

[0085] The electrical length of the interval corresponding to the third point from the right is λ×0.43, which serves as a benchmark for achieving efficient microwave transmission by reducing transmission loss. That is, λ×0.43 is the upper limit related to the electrical length of the interval between adjacent conductive members 420. The aforementioned upper limit related to the electrical length of the interval between adjacent conductive members, i.e., 1.7 times λ / 4, is derived from λ×0.43.

[0086] Example 4 Experiments were conducted by varying the lengths of multiple conductive components. Specifically, in Figure 10A as well as Figure 10B In the configuration shown, the length of the conductive member 420 has been changed. The distance between the transmitting patch antenna and the receiving patch antenna is 0.4m. Microwaves at a frequency of 2.87GHz are emitted from the transmitting patch antenna, and the signal received by the receiving patch antenna is measured using a vector network analyzer. The results are shown below. Figure 12 .

[0087] exist Figure 12In the diagram, the vertical axis represents transmission loss (dB units), and the horizontal axis represents the length of the conductive component (mm units). Figure 12 In this context, the wavelength of microwaves with a frequency of 2.87 GHz is denoted as λ, and the length corresponding to λ / 2 is indicated by an arrow. (From...) Figure 12 It can be seen that if the length of the conductive component is shorter than λ / 2, the microwave transmission loss is reduced sharply, and microwaves can be transmitted efficiently.

[0088] The present disclosure has been described above by way of example, but the above-described embodiments are merely examples and the present disclosure is not limited to the above-described embodiments. The scope of the present disclosure is shown by the claims based on the detailed description of the invention, and includes all changes within the scope and meaning of the statements therein.

[0089] Explanation of reference numerals in the attached figures 100: Diamond sensor; 102: Diamond components; 104: Excitation light; 106: Fluorescence; 108: Excitation light-generating part; 110: Filter; 112: Concentrating element; 114: Optical waveguide; 116: LPF; 118: Optical Detection Department; 120, 400: Sending Department; 122: Complex; 124, 402: Receiving Unit; 126: Electromagnetic wave irradiation section; 130: Control Department; 132: Electromagnetic wave generating unit; 200, 250, 406, 420: Conductive components; 202, 252, 422: Dielectric components; 220: First conductive plate; 222: Second conductive plate; 260: Insulator; 300: Adapter section; 302: Trumpet section; 304: Connector; 306: Central axis; 404: Supporting component; A: Power supply point; D1, D2: Interval; Δf: Frequency difference; L1, L2, L3, L4, L5, L6, L7, L8, L9, L10, L11: Length; O: Center point; Th: thickness; t, t1, t2, t3: time.

Claims

1. A diamond sensor, wherein, The diamond sensor includes: Diamond has color centers with electron spin; An excitation light irradiation section irradiates the diamond with excitation light; The transmitting antenna transmits electromagnetic waves. A receiving antenna for receiving the electromagnetic waves transmitted from the transmitting antenna; The electromagnetic wave irradiation section irradiates the diamond with the electromagnetic waves received by the receiving antenna; The detection unit detects the emitted light from the color center of the diamond after the excitation light and the electromagnetic wave are irradiated onto the diamond. as well as The composite material has both conductive and dielectric components. The composite is disposed between the transmitting antenna and the receiving antenna to transmit the electromagnetic waves.

2. The diamond sensor according to claim 1, wherein, The conductive member is a line whose length in the first direction is longer than the length in any direction orthogonal to the first direction, and is arranged such that the first direction is along the electric field direction of the electromagnetic wave. The wavelength of the electromagnetic wave is set as λ, and the electrical length of the conductive member in the first direction is more than 0.7 times and less than 1.1 times λ / 2.

3. The diamond sensor according to claim 1 or 2, wherein, The conductive components are arranged in multiple ways along the direction of electromagnetic wave propagation. The wavelength of the electromagnetic wave is set as λ, and the electrical length between two adjacent conductive components is more than 0.1 times and less than 1.7 times λ / 4.

4. The diamond sensor according to any one of claims 1 to 3, wherein, The dielectric component includes a thermal insulation component or an electrical insulation component.

5. The diamond sensor according to any one of claims 1 to 4, wherein, The dielectric component comprises air and a dielectric material other than the air.

6. The diamond sensor according to any one of claims 1 to 5, wherein, The dielectric component comprises a porous component.

7. The diamond sensor according to any one of claims 1 to 6, wherein, The dielectric component comprises polyimide, polypropylene, or aluminum oxide.

8. The diamond sensor according to claim 6 or 7, wherein, The dielectric component comprises a dielectric with independent air bubbles.

9. The diamond sensor according to claim 8, wherein, The wavelength of the electromagnetic wave is set as λ, and the size of the independent bubble is greater than λ / 200 and less than λ / 50.

10. The diamond sensor according to any one of claims 1 to 9, wherein, The composite is disposed inside the insulator.

11. The diamond sensor according to claim 10, wherein, The dielectric component is air.

12. The diamond sensor according to any one of claims 1 to 11, wherein, The receiving antenna is a patch antenna.

13. The diamond sensor according to any one of claims 1 to 12, wherein, The transmitting antenna is a horn antenna or a patch antenna.

14. The diamond sensor according to any one of claims 1 to 13, wherein, The electromagnetic waves transmitted from the transmitting antenna are microwaves, millimeter waves, or submillimeter waves.

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