Diamond sensor unit and diamond sensor system

Abstract

A diamond sensor unit comprising: a sensor part containing a diamond having a color center in which electron spin is present; an irradiation part that irradiates the diamond with excitation light; a detection part that detects radiated light from the color center of the diamond; and an optical waveguide through which the excitation light and the radiated light propagate.

Description

[Technical Field]

[0001] This disclosure relates to a diamond sensor unit and a diamond sensor system. This application claims priority to Japanese Patent Application No. 2021-010935, filed on January 27, 2021, and incorporates by reference all of the contents of said Japanese application. [Background technology]

[0002] A sensor using the NV center of diamond is known. When the NV center of diamond is used in combination with a microscope, it is configured as shown in FIG. 1, for example. That is, an LED 900 arranged on a substrate 912 emits green light to excite the NV center of a diamond 904. The emitted light passes through a short pass filter (SPF) 902 and then enters the diamond 904 arranged on the substrate 914. This allows the NV center to be detected. - The electron at the center is excited. When the excited electron returns to its original ground state, red fluorescence is emitted from the diamond 904. The fluorescence is collected by the lens 906, passes through an LPF (Long Pass Filter) 908, and is then detected by a photodiode 910 disposed on a substrate 916. Microwaves generated by an external device (not shown) are also irradiated onto the diamond 904. As a result, when the diamond 904 is excited into a state of resonance with a different spin state, the intensity of the red fluorescence from the diamond 904 changes. This change is detected by the photodiode 910. The lens 906 can be configured as a high-performance optical microscope lens, or a simple lens.

[0003] Patent Document 1 below discloses a scanning probe microscope (i.e., a frequency modulation atomic force microscope (FM-AFM)) that uses the NV center of diamond. Patent Document 2 below discloses a magnetic field detection device that uses the NV center of diamond. Non-Patent Document 2 below discloses a compact magnetic field detection device that uses a lens. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2017-67650 A [Patent Document 2] Japanese Patent Application Publication No. 2018-136316 [Non-patent literature]

[0005] [Non-Patent Document 1] Arne Wickenbrock, et al., “Microwave-free magnetometry with nitrogen-vacancy centers in diamond”, Applied Physics Letters 109, 053505 (2016) [Non-patent document 2] Felix M. Stuerner, et al., “Compact integrated magnetometer based on nitrogen-vacancy centers in diamond”, Diamond & Related Materials 93 (2019) 59-65 Summary of the Invention

[0006] A diamond sensor unit according to one aspect of the present disclosure includes a sensor section including a diamond having a color center with electronic spin, an irradiation section that irradiates the diamond with excitation light, a detection section that detects radiation light from the color center of the diamond, and an optical waveguide that transmits the excitation light and radiation light.

[0007] A diamond sensor system according to another aspect of the present disclosure includes the diamond sensor unit described above, in which a diamond is disposed on a transmission line that transmits microwaves or millimeter waves, and a sensor unit that functions as a magnetic sensor; an electromagnetic wave generating unit that generates microwaves or millimeter waves; an irradiating unit; a detecting unit; knowledgeThe control unit controls the electromagnetic wave generating unit, and the control unit irradiates the diamond with microwaves or millimeter waves in a temporally and spatially combined manner together with the excitation light. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view showing a conventional microscope using a diamond NV center. [Figure 2] FIG. 2 is a schematic diagram showing a schematic configuration of the diamond sensor unit according to the first embodiment of the present disclosure. [Figure 3] FIG. 3 is a sequence diagram showing the timing of irradiation of excitation light and electromagnetic waves and the timing of measurement of synchrotron radiation during measurement using the diamond sensor unit shown in FIG. [Figure 4] FIG. 4 is a graph showing a schematic relationship between the observed signal intensity (ie, the radiation intensity) and the frequency of the electromagnetic wave (ie, the microwave). [Figure 5] FIG. 5 is a schematic diagram showing a schematic configuration of a diamond sensor unit according to the second embodiment of the present disclosure. [Figure 6] FIG. 6 is a schematic diagram showing a schematic configuration of a diamond sensor unit according to a first modified example. [Figure 7] FIG. 7 is a schematic diagram showing a schematic configuration of a diamond sensor unit according to a second modified example. [Figure 8] FIG. 8 is a schematic diagram showing a schematic configuration of a diamond sensor unit according to a third modified example. [Figure 9] FIG. 9 is a schematic diagram showing a schematic configuration of a diamond sensor unit according to the fourth modified example. [Figure 10] FIG. 10 is a schematic diagram showing a schematic configuration of a diamond sensor unit according to the fifth modified example. [Figure 11] FIG. 11 is a perspective view showing an example of the second embodiment (see FIG. 5). [Figure 12] FIG. 12 is a perspective view showing an electromagnetic wave irradiating section using a coplanar line. [Figure 13] FIG. 13 is a perspective view showing a patch antenna for receiving microwaves. [Figure 14A] FIG. 14A is a graph showing the experimental results. [Figure 14B] FIG. 14B is a graph showing the experimental results. [Figure 14C] FIG. 14C is a graph showing the experimental results. [Figure 15] FIG. 15 is a graph showing the experimental results. [Figure 16] FIG. 16 is a perspective view showing an embodiment of the configuration shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Problem to be solved by the invention] When a sensor is used in high-voltage equipment such as electric power equipment, the light-emitting element and the light-receiving element may be damaged by the high voltage and large current that are instantaneously generated by discharge, and by the strong electromagnetic waves that accompany them. The configuration disclosed in Patent Document 1 cannot be used for sensors used in high-voltage environments.

[0010] Patent Document 2 discloses that the light-emitting element and the light-receiving element are arranged at a distance from the diamond and the microwave irradiation coil. However, the excitation light and the emitted fluorescence are transmitted through the air as parallel rays, which causes diffusion, and there is a limit to the distance that can be separated. This is particularly problematic because the signal strength of the fluorescence is weak.

[0011] Therefore, an object of the present disclosure is to provide a diamond sensor unit and a diamond sensor system that are not damaged even in a high-voltage environment and can accurately detect magnetic fields and the like from a remote location.

[0012] [Effects of the invention] According to the present disclosure, it is possible to provide a diamond sensor unit and a diamond sensor system that can measure magnetic fields, electric fields, etc. remotely and accurately without being damaged even in a high-voltage environment.

[0013] [Description of the embodiments of the present disclosure] The contents of the embodiments of the present disclosure will be listed and explained below. At least some of the embodiments described below may be combined in any combination.

[0014] (1) A diamond sensor unit according to a first aspect of the present disclosure includes a sensor section including a diamond having a color center with electronic spin, an irradiation section that irradiates the diamond with excitation light, a detection section that detects radiation from the color center of the diamond, and an optical waveguide that transmits the excitation light and radiation light. This allows for accurate remote measurement of magnetic and electric fields, etc., without being damaged even in a high-voltage environment.

[0015] (2) The sensor unit can include a focusing element for focusing the excitation light and the emitted light, and the focusing element can be disposed between the diamond and the optical waveguide, thereby reducing loss of the excitation light and the emitted light and improving detection accuracy.

[0016] (3) The focusing element may be a spherical lens made of silicon oxide or a Fresnel lens made of silicon oxide, and the optical waveguide may be an optical fiber with a core diameter of 1 μm or more and 80 μm or less. This allows for more efficient transmission of excitation light and emitted light, improving detection accuracy. It also makes it relatively easy to guide the laser light to the desired position and suppresses divergence at the output end of the optical fiber.

[0017] (4) The optical waveguide may be disposed through at least one insulator. This allows detection even if a discharge occurs in a high-voltage environment where the sensor unit is disposed. knowledge This can prevent parts etc. from being damaged.

[0018] (5) The optical waveguide may include a single medium for transmitting the excitation light and the emitted light, and may include a fluorescence reflection filter, LPF, or dichroic mirror for separating the excitation light and the emitted light within a predetermined distance from one of the two ends of the optical waveguide that is located farther from the diamond. This allows for fewer components and a simpler configuration than when separate media for transmitting the excitation light and the emitted light are provided.

[0019] (6) The optical waveguide may include a first optical waveguide that transmits the excitation light and a second optical waveguide that transmits the emitted light, wherein one end of the first optical waveguide may be located closer to the diamond than the other end of the first optical waveguide, and one end of the second optical waveguide may be located closer to the diamond than the other end of the second optical waveguide, and may include a fluorescence reflection filter, LPF, or dichroic mirror that separates the excitation light and the emitted light within a predetermined distance from one end of the first optical waveguide and one end of the second optical waveguide. This allows the excitation light and the emitted light to be transmitted in a form that is suitable for each, compared to when both the excitation light and the emitted light are transmitted through a single medium, thereby improving detection accuracy.

[0020] (7) The first optical waveguide may include a first optical fiber, and the second optical waveguide may include a second optical fiber, the core diameter of which may be larger than the core diameter of the first optical fiber. This allows the excitation light and the emitted light to be transmitted in a form suitable for their respective wavelengths, thereby improving detection accuracy.

[0021] (8) The core diameter of the first optical fiber may be 1 μm or more and 100 μm or less, and the core diameter of the second optical fiber may be 1 μm or more and 1 mm or less. This allows the excitation light and the emitted light to be transmitted using optical fibers with core diameters appropriate for their respective wavelengths, and eliminates the need for optical fibers with unnecessarily thick core diameters, thereby reducing costs.

[0022] (9) The diamond may have at least a plurality of flat surfaces, the excitation light may be incident on a first flat surface of the plurality of flat surfaces, and the detection unit may detect emitted light emitted from a second flat surface other than the first flat surface of the plurality of flat surfaces. This eliminates the need for a component (e.g., a fluorescence reflection filter, an LPF, or a dichroic mirror) that separates the excitation light from the emitted light, thereby reducing costs.

[0023] (10) The sensor part having diamond may be entirely made of an electrically insulating material, which can prevent the sensor part from being damaged even if a discharge or the like occurs in the high-voltage environment in which the sensor part is placed.

[0024] (11) The diamond may be placed on a transmission line that transmits microwaves or millimeter waves, and the sensor unit may function as a magnetic sensor. This allows the microwaves or millimeter waves to be irradiated accurately onto the NV centers of the diamond.

[0025] (12) The transmission line may include a main wiring arranged on a rectangular printed circuit board with sides of 5 cm or less, and a diamond may be arranged at one end of the main wiring, which allows microwaves to be irradiated to the NV center of the diamond.

[0026] (13) The spin coherence time of diamond may be less than 50 μsec. This allows the NV center to quickly return from an excited state to its original state, enabling efficient detection of alternating magnetic and electric fields. In particular, it becomes possible to detect magnetic and electric fields that change in a pulsed manner.

[0027] (14) The total hydrogen concentration in the diamond may be 1 ppm or less. This shortens the spin coherence time T2 of the diamond, allowing the NV center to quickly return from an excited state to its original state. This allows for efficient detection of AC magnetic and electric fields.

[0028] (15) NVH in diamond -The concentration, CH concentration, and CH2 concentration may all be less than 1 ppm. This shortens the spin coherence time T2 of the diamond, allowing the NV center to quickly return from the excited state to its original state. Therefore, it is possible to efficiently detect alternating magnetic and electric fields, including pulse-changing magnetic and electric fields.

[0029] (16) A diamond sensor system according to a second aspect of the present disclosure includes the diamond sensor unit described above, in which a diamond is arranged on a transmission line that transmits microwaves or millimeter waves, and the sensor unit functions as a magnetic sensor, an electromagnetic wave generating unit that generates microwaves or millimeter waves, an irradiating unit, a detecting unit, and a detecting unit. knowledge The control unit controls the electromagnetic wave generator, and the control unit irradiates the diamond with a microwave or millimeter wave in a temporally and spatially combined manner together with the excitation light. This allows for accurate remote measurement of magnetic and electric fields without damage even in a high-voltage environment.

[0030] [Details of the embodiments of the present disclosure] In the following embodiments, the same components are denoted by the same reference numerals, and their names and functions are also the same, so detailed descriptions thereof will not be repeated.

[0031] (First embodiment) 2, the diamond sensor unit 100 according to the first embodiment of the present disclosure includes an excitation light generating section 106, a fluorescence reflecting filter 110, an optical waveguide 112, a sensor section 120, an LPF 122, and a light receiving section 128. An electromagnetic wave generating section 140 and a control section 142 are arranged outside the diamond sensor unit 100.

[0032] The control unit 142 includes a CPU (Central Processing Unit) and a storage unit (neither of which are shown). The processing performed by the control unit 142, which will be described later, is realized by the CPU reading and executing a program stored in advance in the storage unit.

[0033] The excitation light generating unit 106 includes a light emitting element 102 and a light collecting element 104. Under the control of the control unit 142, the light emitting element 102 collects the NV of diamond, which will be described later. - The light-collecting element 104 collects the excitation light output from the light-emitting element 102. The light-collecting element 104 is used to input as much of the excitation light as possible that is diffused and output from the light-emitting element 102 into the light-incident end of the optical waveguide 112, which will be described later. The light-collecting element 104 preferably outputs parallel light that is collected within an area smaller than the size of the light-incident end of the optical waveguide 112 (for example, the core diameter (i.e., the core diameter) when an optical fiber is used).

[0034] The fluorescence reflection filter 110 is an element for separating the excitation light incident from the light-collecting element 104 from the light (i.e., fluorescence) emitted from the diamond, which will be described later. For example, the fluorescence reflection filter 110 is a short-pass filter that passes light with wavelengths equal to or less than a predetermined wavelength and cuts (i.e., reflects) light with wavelengths greater than the predetermined wavelength, or a band-pass filter that passes light with wavelengths within a predetermined wavelength range and cuts (i.e., reflects) light with wavelengths outside the predetermined wavelength range. Generally, excitation light has a shorter wavelength than fluorescence, so such a configuration is preferable. The fluorescence reflection filter 110 is preferably a dichroic mirror with this function.

[0035] The optical waveguide 112 includes a light-transmitting medium and transmits light bidirectionally. That is, the excitation light incident on one end located on the excitation light generating unit 106 side is transmitted to the other end located on the sensor unit 120 side. The emitted light (i.e., fluorescence) from the diamond element 116 incident on the other end is transmitted to the one end. The optical waveguide 112 is, for example, an optical fiber. To increase the energy density of the transmitted excitation light, it is preferable that the core diameter of the optical fiber be as small as possible. On the other hand, if the core diameter is too small, the efficiency of inputting the diffused light emitted from the light source (i.e., the light-emitting element) into the optical fiber decreases. Therefore, there is an appropriate core diameter. For example, the core diameter of the optical fiber is approximately 80 μm or less and 1 μm or more. For example, if the core diameter is larger than 80 μm, it is difficult to increase the energy density of the excitation light even with the use of a lens, which makes it difficult to initialize the spin of the NV center, resulting in a sensor with a slow response speed. To solve this problem, a laser with a higher output power would be required, sacrificing portability and stability. On the other hand, if the core diameter is smaller than 1 μm, the efficiency of injection into the optical fiber would decrease, and the light source size of the corresponding laser diode would become too small, making it more susceptible to failure due to catastrophic optical damage (COD). Furthermore, laser diodes that can generate sufficient output power for pumping light are limited to expensive models, making their practical use difficult.

[0036] The sensor unit 120 includes a light-collecting element 114, a diamond element 116, and an electromagnetic wave irradiator 118. The diamond element 116 includes an NV center. The light-collecting element 114 is disposed in contact with the diamond element 116. The light-collecting element 114 converges the excitation light output from the optical waveguide 112 and irradiates the diamond element 116 with the converged light. The electromagnetic wave irradiator 118 irradiates the diamond element 116 with electromagnetic waves (e.g., microwaves). The electromagnetic wave irradiator 118 is, for example, a coil formed including an electrical conductor. The electromagnetic waves are supplied to the electromagnetic wave irradiator 118 from an electromagnetic wave generator 140 outside the diamond sensor unit 100. The irradiation of the excitation light and electromagnetic waves to the diamond element 116 is controlled by a controller 142, and is performed, for example, at the timing shown in FIG. 3. That is, the controller 142 controls the light-emitting element 102 to output the excitation light at a predetermined timing for a predetermined time (e.g., period t1). The control unit 142 controls the electromagnetic wave generator 140 to output electromagnetic waves at a predetermined timing for a predetermined time (e.g., period t2). An appropriate pulse sequence may be used during period t2 depending on the diamond used (e.g., the alignment of the orientations of multiple NV centers) and the observed signal (i.e., a signal affected by the spin state of the NV center). This allows the electromagnetic waves to be combined temporally and spatially with the excitation light and irradiated onto the diamond element 116. The control unit 142, as will be described later, captures the output signal of the light detector 126 at a predetermined timing (e.g., within period t3) and stores it in the memory unit.

[0037] The NV center has a structure in which a carbon (C) atom in a diamond crystal is replaced with a nitrogen (N) atom, and the carbon atom that should be adjacent to it is not present (i.e., a vacancy (V)). The NV center transitions from the ground state to an excited state when exposed to green light with a wavelength of approximately 490 to 560 nm (e.g., 532 nm laser light), and then emits red light with a wavelength of approximately 630 to 800 nm (e.g., 637 nm fluorescence) and returns to the ground state. The NV center is in a state in which one electron is captured (i.e., NV - ), the magnetic quantum number m s forms a spin triplet state of -1, 0, +1, and in the presence of a magnetic field, m sThe energy levels of the =±1 state are separated according to the magnetic field strength (i.e., Zeeman separation). By irradiating the NV center with microwaves of about 2.87 GHz, s = 0 state is m s After causing a transition to a state of Δf = ±1 (i.e., electron spin resonance), it is excited by irradiating it with green light. As a result, the transition when returning to the ground state includes a transition that does not emit light (i.e., fluorescence), so the intensity of the observed emitted light decreases. Therefore, a valley (i.e., a drop in the signal) is observed in the ESR (Electron Spin Resonance) spectrum. As described above, the control unit 142 controls the light-emitting element 102 and the electromagnetic wave generation unit 140, and thereby, for example, a spectrum such as that shown in Figure 4 is measured. The observed Δf depends on the magnetic field strength at the position of the diamond element 116.

[0038] A specific spectrum is measured as follows. That is, the light (i.e., fluorescence) diffused and emitted from the diamond element 116 is collected by the collecting element 114 to form parallel light, which is input to the other end of the optical waveguide 112. The light (i.e., fluorescence) input to the optical waveguide 112 is transmitted through the optical waveguide 112 and output from one end of the optical waveguide 112. The light (i.e., fluorescence) output from one end of the optical waveguide 112 is reflected by the fluorescence reflection filter 110, passes through the LPF 122, is collected by the collecting element 124, and is irradiated onto the optical detection unit 126. As a result, light of a frequency corresponding to the magnetic field at the position where the diamond element 116 is placed is detected by the optical detection unit 126. The optical detection unit 126 generates and outputs an electrical signal corresponding to the incident light. The optical detection unit 126 is, for example, a photodiode. The output signal from the optical detection unit 126 is acquired by the control unit 142.

[0039] LPF 122 is a long-pass filter that passes light with wavelengths equal to or greater than a predetermined wavelength and cuts (for example, reflects) light with wavelengths smaller than the predetermined wavelength. The emitted light from diamond element 116 is red light and passes through LPF 122, but the excitation light has a shorter wavelength and does not pass through LPF 122. This prevents the excitation light emitted from light-emitting element 102 from being detected by light detection unit 126 and becoming noise, thereby preventing a decrease in the detection sensitivity of the emitted light (i.e., fluorescence) from diamond element 116.

[0040] As described above, the control unit 142 irradiates the diamond element 116 with excitation light, sweeps the frequency of the electromagnetic wave within a predetermined range and irradiates the diamond element 116 with it, and acquires the light (i.e., fluorescence) emitted from the diamond element 116 as an electrical signal output from the light detection unit 126. The magnetic field strength at the position of the diamond element 116 can be calculated from the observed Δf (i.e., a value dependent on the magnetic field strength at the position of the diamond element 116). In other words, the diamond sensor unit 100 functions as a magnetic sensor. Note that the diamond sensor unit 100 can be used as a sensor for detecting not only magnetic fields (i.e., magnetic fields), but also physical quantities related to magnetic fields, such as magnetization, electric fields, voltage, current, temperature, and pressure.

[0041] By using optical fiber for the optical waveguide 112, the diamond element 116, which is the main body of the sensor, and the light-collecting element 114 are formed of electrical insulators. This prevents damage due to discharge, even if the other end of the sensor unit 120 and the optical waveguide 112 are installed in high-voltage equipment. Therefore, the diamond sensor unit 100 can safely measure magnetic fields and other parameters in high-voltage environments. Furthermore, the excitation light generating unit 106 and the light-receiving unit 128 can be located away from high-voltage environments via the optical waveguide 112, enabling the diamond sensor unit 100 to measure magnetic fields and other parameters remotely. Furthermore, the sensor unit 120 includes the light-collecting element 114, which is located between the diamond element 116 and the optical waveguide 112, reducing loss of excitation light and emitted light and improving detection accuracy. Furthermore, a fluorescence reflection filter 110 is provided to separate the excitation light from the emitted light, allowing the excitation light and emitted light to be transmitted via a single medium (e.g., the optical waveguide 112). This allows for fewer components and a simpler configuration than when two media are provided for transmitting the excitation light and the emitted light, as will be described later.

[0042] (Second embodiment) In the first embodiment, one optical waveguide 112 was used to transmit light (i.e., excitation light and emitted light) in both directions, but in the second embodiment, optical waveguides are used to transmit each of the excitation light and emitted light of the diamond element 216. Referring to Figure 5, a diamond sensor unit 200 according to the second embodiment of the present disclosure includes an excitation light generating section 206, a first optical waveguide 212, a focusing element 208, a fluorescence reflection filter 210, a sensor section 220, an LPF 222, a focusing element 224, a second optical waveguide 230, and a light receiving section 228. As in the first embodiment, an electromagnetic wave generating section 140 and a control section 142 are arranged outside the diamond sensor unit 200.

[0043] The excitation light generating unit 206 includes a light-emitting element 202 and a light-collecting element 204. The sensor unit 220 includes a light-collecting element 214, a diamond element 216, and an electromagnetic wave irradiating unit 218. The light receiving unit 228 includes a light detecting unit 226. The light-emitting element 202, the light-collecting element 204, the fluorescence reflection filter 210, the light-collecting element 214, the diamond element 216, the electromagnetic wave irradiating unit 218, the LPF 222, and the light detecting unit 226 correspond to the light-emitting element 102, the light-collecting element 104, the fluorescence reflection filter 110, the light-collecting element 114, the diamond element 116, the electromagnetic wave irradiating unit 118, the LPF 122, and the light detecting unit 126 shown in FIG. 2, respectively, and function in the same way. Therefore, they will be described briefly.

[0044] As in the first embodiment, the light-emitting element 202 generates excitation light for exciting the NV center of diamond under the control of the control unit 142. The control unit 142 supplies, for example, a voltage to the light-emitting element 202 at a predetermined timing to cause the light-emitting element 202 to emit light. The excitation light is green light. The excitation light is preferably laser light, and the light-emitting element 202 is preferably a semiconductor laser. The light-collecting element 204 collects the excitation light diffused and output from the light-emitting element 202, and inputs it to the light-incident end of the first optical waveguide 212.

[0045] The first optical waveguide 212 includes a medium for transmitting light. Unlike the optical waveguide 112 shown in FIG. 2, the first optical waveguide 212 transmits excitation light but does not transmit radiation light from the diamond element 216. That is, excitation light incident on one end (i.e., the input end) of the first optical waveguide 212 located on the excitation light generating unit 206 side is transmitted to the other end (i.e., the output end) located on the sensor unit 220 side and output. The first optical waveguide 212 is, for example, an optical fiber. The excitation light diffused and output from the first optical waveguide 212 is collected by the collecting element 208 and incident on the fluorescence reflecting filter 210 as parallel light.

[0046] The fluorescence reflection filter 210 is an element for separating the excitation light incident from the light-collecting element 208 from the light (i.e., fluorescence) emitted from the diamond element 216. The fluorescence reflection filter 210 may be a dichroic mirror.

[0047] The focusing element 214 focuses the excitation light that has passed through the fluorescence reflection filter 210 and is input, and irradiates the diamond element 216. The focusing element 214 is arranged in contact with the diamond element 216. The diamond element 216 includes an NV center. The electromagnetic wave irradiating unit 218 irradiates the diamond element 216 with electromagnetic waves (e.g., microwaves). The electromagnetic wave irradiating unit 218 is, for example, a coil. The electromagnetic waves are supplied to the electromagnetic wave irradiating unit 218 from the electromagnetic wave generating unit 140. The irradiation of the excitation light and electromagnetic waves to the diamond element 216 is controlled by the control unit 142, for example, at the timing shown in FIG. 3. As a result, red light (i.e., fluorescence) is emitted from the diamond element 216, as described above.

[0048] The light diffused and emitted from the diamond element 216 (i.e., red fluorescence) is collected by the light collecting element 214 to become parallel light, and is input to the fluorescence reflection filter 210. The light input to the fluorescence reflection filter 210 (i.e., red fluorescence) is reflected by the fluorescence reflection filter 210 and enters the LPF 222. The emitted light from the diamond element 216 (i.e., red fluorescence) that enters the LPF 222 passes through the LPF 222, is collected by the light collecting element 224, and enters one end (i.e., incident end) of the second optical waveguide 230. The LPF 222 prevents the excitation light emitted from the light-emitting element 202 from being detected by the light detecting unit 226 and becoming noise, and therefore prevents a decrease in the detection sensitivity of the emitted light from the diamond element 216 (i.e., fluorescence).

[0049] The second optical waveguide 230 includes a medium for transmitting light. The second optical waveguide 230 transmits light (i.e., light emitted from the diamond element 216) incident on one end (i.e., incident end) from the light-collecting element 224 to the other end (i.e., output end) located on the light-receiving unit 228 side. The light output from the second optical waveguide 230 is detected by the light detection unit 226. The light detection unit 226 is, for example, a photodiode. The output signal of the light detection unit 226 is acquired by the control unit 142.

[0050] As described above, the control unit 142, like the first embodiment, irradiates the diamond element 216 with excitation light, sweeps the frequency of electromagnetic waves within a predetermined range and irradiates the diamond element 216 with the electromagnetic waves, and acquires the light (i.e., fluorescence) emitted from the diamond element 216 as an electrical signal output from the light detection unit 226. Therefore, the diamond sensor unit 200 functions as a magnetic sensor. The diamond sensor unit 200 can be used as a sensor for detecting not only magnetic fields but also physical quantities related to magnetic fields, such as magnetization, electric fields, voltage, current, temperature, and pressure.

[0051] By using optical fibers for the two optical waveguides, the diamond element 216, which is the main body of the sensor, and the light-collecting element 214 are made of electrical insulators, which reduces the risk of damage due to discharges and the like. Therefore, the diamond sensor unit 200 can safely measure magnetic fields and the like in high-voltage environments. Furthermore, the excitation light generating unit 206 and the light-receiving unit 228 can be located away from high-voltage environments via the first optical waveguide 212 and the second waveguide 230, making it possible to measure magnetic fields and the like remotely using the diamond sensor unit 200. Furthermore, the sensor unit 220 includes the light-collecting element 214, which is located between the diamond element 216 and the first optical waveguide 212 and the second waveguide 230, thereby reducing loss of excitation light and emitted light and improving detection accuracy.

[0052] By using two optical waveguides (i.e., the first optical waveguide 212 and the second optical waveguide 230), the excitation light and the emitted light from the diamond element 216, which have different wavelengths, can be appropriately transmitted. That is, by using an optical fiber with a core diameter according to the wavelength, it is possible to design a focusing optical system (i.e., focusing element 204, focusing element 208, focusing element 214, and focusing element 224) suitable for each, thereby improving the light transmission efficiency and measurement accuracy. When an optical fiber is used as the optical waveguide, it is preferable that the core diameter of the optical fiber (i.e., the second optical waveguide 230) that transmits the emitted light from the diamond is larger than the core diameter of the optical fiber (i.e., the first optical waveguide 212) that transmits the excitation light.

[0053] As mentioned above, the optical fiber used to transmit the excitation light should have a small core diameter to increase the energy density of the excitation light. However, if the core diameter is too small, loss occurs when light is input from the light source to the optical fiber. Therefore, there is an appropriate core diameter. The core diameter of the first optical waveguide 212 is preferably 1 μm or more and 100 μm or less. On the other hand, the larger the core diameter of the optical fiber used to transmit the emitted light from the diamond element 216, the better. However, if the core diameter is too large, the cost will increase. The core diameter of the second optical waveguide 230 is preferably 1 μm or more and 1 mm or less. However, even in this case, if the core diameter of the second optical waveguide 230 is smaller than the core diameter of the first optical waveguide 212, the fluorescence generated by the excitation light will not be sufficiently collected, resulting in a large loss of driving power. Therefore, the core diameter of the second optical waveguide 230 is preferably equal to or greater than the core diameter of the first optical waveguide 212, and more preferably greater than the core diameter of the first optical waveguide 212. For example, when the core diameter of the first optical waveguide 212 is 1 μm, the core diameter of the second optical waveguide 230 is preferably equal to or greater than 1 μm, more preferably equal to or greater than 25 μm, and even more preferably equal to or greater than 50 μm. Furthermore, when the core diameter of the first optical waveguide 212 is 1 μm, the core diameter of the second optical waveguide 230 is preferably equal to or greater than 80 μm rather than equal to or greater than 50 μm, more preferably equal to or greater than 400 μm, and even more preferably equal to or greater than 800 μm. For example, when the core diameter of the first optical waveguide 212 is 80 μm, the core diameter of the second optical waveguide 230 is preferably equal to or greater than 80 μm, more preferably equal to or greater than 105 μm, more preferably equal to or greater than 400 μm, and even more preferably equal to or greater than 800 μm. In either case, if the core diameter is greater than 1 mm, inconveniences arise such as the optical fiber being difficult to bend, being costly, etc. As described above, if the core diameter of the first optical waveguide 212 is in the range of 1 μm or more and 100 μm or less, the above-mentioned preferable conditions are met.

[0054] (First Modification) In the second embodiment, the excitation light and the emitted light of the diamond element 216 are separated using the fluorescence reflection filter 210 and the LPF 222, but the present invention is not limited to this. The excitation light and the emitted light of the diamond element 216 may be separated by using the excitation light reflection filter having the function of an LPF.

[0055] Referring to Figure 6, the diamond sensor unit 300 according to the first modification uses an excitation light reflection filter 302 with an LPF function to separate the excitation light from the light emitting element 202 and the emitted light from the diamond element 216. The diamond sensor unit 300 is the diamond sensor unit 200 (see Figure 5) in which the fluorescence reflection filter 210 and the LPF 222 are replaced with an excitation light reflection filter 302 with an LPF function, and the path for generating and transmitting the excitation light and the path for transmitting and detecting the emitted light from the diamond element 216 are interchanged. The excitation light reflection filter 302 with an LPF function is both a long-pass filter and an excitation light reflection filter. In Figure 6, components with the same reference numerals as in Figure 5 represent the same components as in Figure 5. Therefore, redundant description thereof will not be repeated.

[0056] The excitation light generated by the light-emitting element 202 is collected by the light-collecting element 204 and input to one end of the first optical waveguide 212. The excitation light is transmitted through the first optical waveguide 212, output from the other end of the first optical waveguide 212, and collected by the light-collecting element 224 to become parallel light, which then enters the excitation light reflection filter 302 that functions as an LPF. Since the excitation light is green light, it is reflected by the excitation light reflection filter 302 that functions as an LPF and enters the light-collecting element 214.

[0057] On the other hand, the light emitted from the diamond element 216 is collected by the light collecting element 214 to become parallel light, and enters the excitation light reflection filter 302 having the function of an LPF. The light emitted from the diamond element 216 (i.e., red fluorescence) passes through the excitation light reflection filter 302 having the function of an LPF, is collected by the light collecting element 224, enters the second optical waveguide 230, is transmitted by the second optical waveguide 230 to the light receiving unit 228, and is detected by the light receiving unit 228. Therefore, similar to the diamond sensor unit 200 of the second embodiment, the diamond sensor unit 300 functions as a sensor that detects magnetic fields, etc.

[0058] (Second Modification) In the above, the case where excitation light is incident on one surface of the diamond element containing NV center and the radiation light from the same surface is measured has been described, but this is not limited to this.When the diamond element containing NV center has multiple flat surfaces, the surface that is irradiated with excitation light and the surface that measures the radiation light may be different.A flat surface means a single plane that has an area of ​​at least a predetermined size, and here, the flat surface of the diamond element containing NV center means a single plane that has an area larger than a circle with a diameter of about 200 μm.

[0059] 7, a diamond sensor unit 400 according to the second modification detects light emitted from a surface of a diamond element 402 different from the surface on which excitation light is incident. Diamond sensor unit 400 is the same as diamond sensor unit 200 shown in FIG. 5, except that sensor unit 220 is replaced with sensor unit 408, and light-collecting element 208, fluorescence reflection filter 210, and light-collecting element 224 have been removed. In FIG. 7, components with the same reference numerals as those in FIG. 5 represent the same components as those in FIG. 5. Duplicate explanations of these components will not be repeated.

[0060] The sensor unit 408 includes a diamond element 402, a light-collecting element 404, a light-collecting element 406, and an electromagnetic wave irradiation unit 218. The diamond element 402 includes an NV center and has a plurality of flat surfaces. The diamond element 402 is formed, for example, in the shape of a rectangular parallelepiped. The light-collecting element 404 is arranged in contact with one flat surface (hereinafter referred to as a first flat surface) of the diamond element 402. The light-collecting element 406 is arranged in contact with a flat surface (hereinafter referred to as a second flat surface) of the diamond element 402 that is different from the first flat surface.

[0061] The excitation light transmitted by the first optical waveguide 212 enters the light-collecting element 404, is collected by the light-collecting element 404, and irradiates the first flat surface of the diamond element 402. As described above, the diamond element 402 is irradiated with excitation light and electromagnetic waves (e.g., microwaves) by the electromagnetic wave irradiator 218 at predetermined timings, causing light to be emitted from the diamond element 402. The radiated light is emitted in all directions. The light radiated from the second flat surface of the diamond element 402 (i.e., red fluorescence) is collected by the light-collecting element 406 to become parallel light, which enters the LPF 222 and passes through the LPF 222 to one end of the second optical waveguide 230. The light radiated from the second flat surface of the diamond element 402 (i.e., red fluorescence) is then transmitted by the second optical waveguide 230 to the light detector 226 and detected by the light detector 226. Therefore, similar to the diamond sensor unit 200 of the second embodiment, the diamond sensor unit 400 functions as a sensor that detects a magnetic field or the like.

[0062] In this way, by configuring the device to detect emitted light from a surface (i.e., the second flat surface) different from the surface irradiated with excitation light (i.e., the first flat surface), the number of light-collecting elements can be reduced, and the elements (e.g., fluorescent reflection filters) for separating the excitation light from the emitted light of the diamond element can be reduced. Therefore, the diamond sensor unit can be made into a simpler configuration, and costs can be reduced.

[0063] In the above, a case has been described in which diamond element 402 is formed into a rectangular parallelepiped, and the first flat surface and the second flat surface are two surfaces that form an angle of 90 degrees, but this is not limiting. When diamond element 402 is formed into a rectangular parallelepiped, a flat surface parallel to the first flat surface may be used as the second flat surface that collects the radiation light to be detected. Furthermore, diamond element 402 only needs to have at least two flat surfaces, and is not limited to a hexahedron, and the shape of diamond element 402 is arbitrary.

[0064] (Third Modification) Although the above description has been given of a case where an electromagnetic wave (e.g., microwave) is irradiated onto a diamond element containing an NV center, the present invention is not limited to this. As disclosed in Non-Patent Document 1, a diamond element containing an NV center can function as a magnetic sensor even without being irradiated with an electromagnetic wave.

[0065] Referring to FIG. 8, the diamond sensor unit 500 according to the third modification is the diamond sensor unit 100 shown in FIG. 2 with the electromagnetic wave irradiating unit 118 removed. That is, the sensor unit 502 includes the light-collecting element 114 and the diamond element 116, but does not include an electromagnetic wave irradiating unit (e.g., a coil). In the diamond sensor unit 500, similar to the diamond sensor unit 100 (see FIG. 2), excitation light (i.e., green light) output from the light-emitting element 102 is irradiated onto the diamond element 116. This excites the NV center of the diamond element 116, which then emits light (i.e., red fluorescence) and returns to its original state. Therefore, by measuring the emitted light, the diamond sensor unit 500 functions as a magnetic sensor.

[0066] The measurement principle using microwaves is as described above, and by utilizing the difference between the intensity of fluorescence from the ground level and the intensity of fluorescence from the excited level resonantly absorbed by microwaves, the resonance level can be quantified using the microwave frequency, and changes in the magnetic field can be measured by changes in the resonance level. On the other hand, the measurement principle used here utilizes the fact that fluorescence intensity changes even when microwaves are not irradiated. In other words, it utilizes the fact that electrons present in the ground level change under the influence of a magnetic field, and the fluorescence intensity changes in correlation with the magnetic field.

[0067] Therefore, the diamond sensor unit 500 functions as a sensor that detects magnetic fields, etc. The sensor section 502 does not include conductive members such as coils, and is composed entirely of electrically insulating members. Therefore, even if the sensor section 502 is installed in high-voltage equipment, it will not be damaged by discharge, etc. As a result, the diamond sensor unit 500 can safely measure magnetic fields, etc. in a high-voltage environment.

[0068] (Fourth Modification) The configuration for making a diamond element containing an NV center function as a magnetic sensor without irradiating it with electromagnetic waves is not limited to that shown in Figure 8. Referring to Figure 9, a diamond sensor unit 600 according to a fourth modified example is obtained by removing the light-collecting element 114 and the electromagnetic wave irradiating unit 118 from the diamond sensor unit 100 shown in Figure 2. That is, the sensor unit 602 includes a diamond element 116, but does not include either a light-collecting element or an electromagnetic wave irradiating unit. The diamond element 116 is arranged in contact with the end of the optical waveguide 112.

[0069] In the diamond sensor unit 600, similarly to the diamond sensor unit 100 (see FIG. 2), when the excitation light (i.e., green light) output from the light-emitting element 102 is irradiated onto the diamond element 116, the NV center of the diamond element 116 is excited, emits light (i.e., red fluorescence), and returns to its original state. Therefore, by measuring the emitted light, the diamond sensor unit 600 functions as a magnetic sensor. The method of measuring the magnetic field is the same as in the third modified example.

[0070] Therefore, the diamond sensor unit 600 functions as a sensor that detects magnetic fields, etc. The sensor section 602 does not include conductive members such as coils, and is made entirely of electrically insulating materials. Therefore, even if the sensor section 602 is installed in high-voltage equipment, it will not be damaged by discharge, etc., and can safely measure magnetic fields, etc. in a high-voltage environment.

[0071] (Fifth Modification) In the third and fourth modifications, the excitation light and the emitted light are transmitted through one optical waveguide. However, two optical waveguides may be used to transmit each of the excitation light and the emitted light. Referring to FIG. 10, the diamond sensor unit 700 according to the fifth modification is the diamond sensor unit 200 shown in FIG. 5, with the electromagnetic wave irradiating unit 218 removed. That is, the sensor unit 702 includes the light-collecting element 214 and the diamond element 216, but does not include an electromagnetic wave irradiating unit (e.g., a coil). In the diamond sensor unit 700, similar to the diamond sensor unit 200 (see FIG. 5), when the diamond element 216 is irradiated with excitation light (i.e., green light) output from the light-emitting element 202, the NV center of the diamond element 216 is excited, emitting light (i.e., red fluorescence), and returning to its original state. Therefore, by measuring the emitted light, the diamond sensor unit 700 functions as a magnetic sensor. The magnetic field measurement method is the same as that of the third modification.

[0072] Therefore, the diamond sensor unit 700 functions as a sensor that detects magnetic fields, etc. The sensor section 702 does not include conductive members such as coils, and is composed entirely of electrically insulating members. Therefore, even if the sensor section 702 is installed in high-voltage equipment, it will not be damaged by discharge, etc., and can safely measure magnetic fields, etc. in a high-voltage environment.

[0073] The electromagnetic wave irradiating section 218 may be removed from the diamond sensor unit 300 shown in Fig. 6 and the diamond sensor unit 400 shown in Fig. 7. In this case, too, the magnetic field can be measured without irradiating electromagnetic waves.

[0074] In the above, we have described the case where a diamond element having an NV center is used in the diamond sensor unit, but this is not limited to this. Any diamond element having a color center with electronic spin will do. A color center with electronic spin is a center that forms a spin triplet state and emits light when excited, and the NV center is a typical example. In addition, it is known that color centers with electronic spin also 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 may be used instead of diamond elements containing NV centers to construct a diamond sensor unit.

[0075] The wavelengths of the excitation light and emitted light (i.e., fluorescence) and the frequency of the electromagnetic waves used for resonant excitation vary depending on the level of the color center. Among these, NV centers are preferred because they are easy to handle in terms of the wavelength of light and the frequency of microwaves. In the case of Si-V centers, Ge-V centers, and Sn-V centers, millimeter waves (e.g., 30 GHz to 300 GHz) or submillimeter waves (e.g., 300 GHz to 3 THz) with higher frequencies than microwaves (e.g., 1 GHz to 30 GHz) are used as the electromagnetic waves to be irradiated. For example, millimeter waves of approximately 48 GHz can be used for Si-V centers, and submillimeter waves of approximately 850 GHz can be used for Sn-V centers.

[0076] The excitation light is preferably a laser beam, and a semiconductor laser is more preferable as a generator because it can be made smaller. The detector for the emitted light from the diamond element may be a vacuum tube type, but a semiconductor detection device is more preferable because it can be made smaller.

[0077] The optical waveguide preferably has a coaxial structure of two or more layers, having a core portion through which light passes and a portion formed around the core and made of a material with a different refractive index from that of the core portion. The core portion does not have to be densely filled with a medium that transmits light. The core portion may be hollow, since the space itself can transmit light. The optical waveguide is preferably an optical fiber with a core diameter of 1 μm or more and 80 μm or less. This is because using an optical fiber makes it relatively easy to guide laser light to the desired location and also suppresses divergence at the output end of the optical fiber.

[0078] The focusing element may be formed of any material capable of focusing light. For example, it may be a lens formed of a silicon oxide-based material (e.g., glass, which may contain additives other than silicon oxide) or a material with diffractive properties. The focusing element is preferably a lens that transmits light and utilizes refraction. Spherical lenses, hemispherical lenses, and Fresnel lenses are preferred. Lenses in which the focal point of parallel light is located on a spherical surface due to the relationship between the refractive index and spherical shape are particularly preferred. The use of such lenses greatly simplifies the adjustment of the optical focus and optical axis, maximizing the use of light. It is preferable that silicon oxide-based lenses be in direct contact with the diamond. Failure to do so can result in insufficient focusing of light. Furthermore, a strong impact can change the distance from the diamond to the lens, which can also affect the focusing of light. Furthermore, it is more preferable that silicon oxide-based lenses be in direct contact with the optical fiber. This reduces loss when focusing fluorescence into the optical fiber and makes it less likely that the distance will change due to an impact.

[0079] When the sensor unit is placed in a high-voltage environment, it is preferable to place the optical waveguide (e.g., optical fiber) that transmits the excitation light and the emitted light from the diamond inside an insulator. This insulates the excitation light generating unit and the light receiving unit from high voltage and protects the devices used in the excitation light generating unit and the light receiving unit.

[0080] The electromagnetic wave irradiating section is not limited to a coil-shaped one, and may be a linear electrical wiring, as will be described later. In this case, the diamond element may be placed on the surface or at the end of a transmission path (e.g., a conductive member) that transmits electromagnetic waves (e.g., microwaves or millimeter waves). This allows the electromagnetic waves to be irradiated accurately to the NV centers of the diamond.

[0081] When using the diamond sensor unit described above to detect time-dependent changes in a fluctuating magnetic field or the like using AC power as a target, it is preferable that the NV center of the diamond element, after being excited, quickly returns from the state of emitting light to its original state (i.e., the state before excitation). For this purpose, it is preferable that the spin coherence time T2 of the diamond element is short. For example, it is preferable that the spin coherence time T2 of the diamond element is less than 50 μsec. The detection sensitivity (T2) -1 / 2 Therefore, when detecting sudden changes in magnetic field fluctuations, for example, when detecting pulsed magnetic field fluctuations, it is possible to sacrifice detection sensitivity and shorten the spin coherence time T2 of the diamond element as much as possible.

[0082] To shorten the spin coherence time, it is preferable that the diamond element contains impurities. Considering that the smaller T2 is, the lower the detection sensitivity is, for example, it is preferable that the total hydrogen concentration in the diamond is greater than 0 ppm and less than 1 ppm. In addition, the NVH in the diamond - It is also preferable that the concentration, CH concentration, and CH2 concentration are all greater than 0 ppm and equal to or less than 1 ppm, where the concentration (unit: ppm) represents the ratio of the number of atoms. [Example]

[0083] The effectiveness of the present disclosure will be demonstrated below by way of an example. Figure 11 shows an example of the configuration shown in Figure 5. In Figure 11, components corresponding to those shown in Figure 5 are assigned the same reference numerals as in Figure 5.

[0084] Step-index multimode optical fibers were used for the first optical waveguide 212 and the second optical waveguide 230. The first optical waveguide 212 had a core diameter of 50 μm and an NA (i.e., numerical aperture) of 0.2. The second optical waveguide 230 had a core diameter of 400 μm and an NA of 0.5. The diamond element 216 was a rectangular diamond measuring 3 mm × 3 mm × 0.3 mm. The focusing element 214 was a spherical lens with a diameter of 2 mm, which was fixed in contact with the surface of the diamond element 216 (i.e., the flat surface of 3 mm × 3 mm). The optical system for transmitting the excitation light included the focusing element 208, the fluorescence reflection filter 210, and a triangular prism 250, forming a collimating optical system. This adjusted the excitation light to be incident on the center of the focusing element 214.

[0085] The electromagnetic wave irradiation section 218 used a coplanar line as shown in Figure 12. A copper foil 272 formed on the surface of a glass epoxy substrate 270 with a side length of approximately 2 cm was cut into a U-shape, and the electromagnetic wave irradiation section 218, which is the main wiring with a width of 1 mm, was formed in the center. The diamond element 216 was fixed with silver paste to one end of the electromagnetic wave irradiation section 218 (i.e., the area shown by the dashed-dotted oval in Figure 12). This allows microwaves to be accurately irradiated to the NV center of the diamond element 216. The other end of the electromagnetic wave irradiation section 218 (i.e., the end where the diamond element 216 is not located) was connected to the connector 254 in Figure 11.

[0086] Microwaves were generated by a remote microwave generator, transmitted through the air, and received by antenna 252 (see FIG. 11). A horn antenna (gain 10 dB) was used to radiate the microwaves into the air. Antenna 252 was the patch antenna (frequency 2.873 GHz, maximum gain approximately 10 dBi) shown in FIG. 13. The patch antenna included substrates 280 and 284 and a connector 288 for outputting the received signal. Substrates 280 and 284 were spaced apart by spacers 286 at the four corners, leaving a gap H (H = 5.2 mm). Both substrates 280 and 284 were glass epoxy resin substrates (e.g., FR4), 1 mm thick, and square in shape (each side had a length L of 120 mm). Four conductive members 282 were arranged on the surface of substrate 280 that did not face substrate 284. A conductive member is arranged over the entire surface of the surface of substrate 284 facing substrate 280 (hereinafter referred to as the ground surface). The four conductive members 282 are connected in parallel to the signal line of connector 288, and the ground surface of substrate 284 is connected to the shield (i.e., ground) of connector 288. The microwaves received by antenna 252 are transmitted to connector 254 via a transmission path (i.e., a coaxial cable), and are irradiated from electromagnetic wave irradiator 218 to diamond element 216.

[0087] A PIN-AMP (i.e., a photodiode IC with a linear current amplifier circuit) was used for the light detection unit 226. The PIN-AMP used had a photodiode sensitivity wavelength range of 300 to 1000 nm and a maximum sensitivity wavelength of 650 nm, and amplified the photocurrent generated by the photodiode by 1300 times before outputting it.

[0088] The light-collecting element 214, diamond element 216, and electromagnetic wave irradiator 218 that make up the sensor unit were placed near electrical wiring 260, and an AC current (50 Hz or 60 Hz, 30 A) was passed through the electrical wiring 260, with the resulting fluctuating magnetic field being the detection target. The maximum value of the magnetic field formed in the sensor unit by the AC current was approximately 0.3 μT. The power of the microwaves radiated from the horn antenna was kept constant (30 dBm (= 1 W)), and measurements were taken while changing the distance D between the sensor unit and the horn antenna radiating the microwaves. The results are shown in Figures 14A to 14C and 15.

[0089] 14A to 14C show signals detected by the PIN-AMP when a 50 Hz AC current (30 A) is passed through the electrical wiring 260. FIGS. 14A to 14C show measurement results when D=2.8 (m), D=4 (m), and D=5 (m), respectively. In all cases, the vertical axis represents 10.0 mV per division, and the horizontal axis represents 5 ms per division. FIG. 15 shows signals detected by the PIN-AMP when a 60 Hz AC current (30 A) is passed through the electrical wiring 260 and D=10 (m). The vertical axis represents 10.0 mV per division, and the horizontal axis represents 4 ms per division.

[0090] As can be seen from Figures 14A to 14C and Figure 15, the detected signal decreases as the microwave radiation distance D increases. However, even when a relatively weak microwave of about 1 W was radiated from a position about 10 m away from the sensor unit, the magnetic field change caused by the AC current was sufficiently detected. The detection signal shown in Figures 14A to 14C varies at an AC frequency of 50 Hz. The detection signal shown in Figure 15 varies at an AC frequency of 60 Hz. Note that microwaves attenuate with distance, but the radiated microwave power, the gain of the radiating antenna, and the gain of the receiving antenna can be adjusted taking into account the detection limit (i.e., the lower limit of power) of the optical detection unit used and the radiation distance.

[0091] In the above, the coplanar line is formed on a substrate with a side of about 2 cm, but a rectangular substrate with a side of about 5 cm or less may also be used.

[0092] Furthermore, as shown in the third to fifth modified examples (see Figs. 8 to 10), magnetic fields can be detected without irradiating the diamond element with electromagnetic waves (e.g., microwaves, etc.). For example, as shown in Fig. 16, a diamond sensor unit may be constructed by excluding the elements for irradiating microwaves (i.e., electromagnetic wave irradiator 218, antenna 252, connector 254, etc.) from the configuration of the embodiment shown in Fig. 11. In this case, too, it is possible to detect a fluctuating magnetic field generated by an alternating current flowing through electrical wiring 260.

[0093] The experiment was conducted under the same experimental conditions as above, where the focusing element 214 was placed 0.1 mm away from the surface of the diamond element 216, making it non-contact, and the other conditions were the same as those for the experiment where D = 2.8 m, i.e., the signal in Figure 14A was observed. As a result, the signal intensity was less than 1 / 10 of the detection limit and could not be observed. It is believed that the density of the excitation light was reduced and the fluorescence intensity was not focused, resulting in a signal intensity of less than 1 / 10. Note that signal intensity refers to the difference between the maximum and minimum values ​​obtained by averaging the noise portion of the vertical axis value in Figure 14A.

[0094] Furthermore, experiments were conducted with the core diameter of the first optical waveguide 212 set to 1 μm and the core diameter of the second optical waveguide 230 varied to 0.9 μm, 1 μm, 25 μm, 50 μm, 80 μm, 400 μm, and 800 μm. Other conditions were the same as the experimental conditions for D = 2.8 μm described above, i.e., the experimental conditions under which the signal in FIG. 14A was observed. As a result, the signal intensity (i.e., fluorescence intensity) was less than 0.1 times, 0.5 times, 1.2 times, 1.6 times, 1.8 times, 1.9 times, and 2 times the signal intensity in FIG. 14A, respectively, with the signal intensity being taken as a reference value (e.g., 1). That is, signals were detectable except when the core diameter of the second optical waveguide 230 was 0.9 μm, and the detected signal increased as the core diameter of the second optical waveguide 230 increased. It should be noted that when the core diameter of the second optical waveguide 230 was 1.2 mm, it was not possible to accommodate it in a compact experimental system. Furthermore, similar experiments were conducted on other modified examples that utilized the first optical waveguide 212 and the second optical waveguide 230, and as a result, approximately the same ratio as above was obtained for the detected signal strength.

[0095] In addition, experiments were conducted with the core diameter of the first optical waveguide 212 set to 80 μm and the core diameter of the second optical waveguide 230 changed to 50 μm, 80 μm, 105 μm, 400 μm, and 800 μm. Other conditions were the same as the experimental conditions for D = 2.8 μm described above, i.e., the experimental conditions under which the signal in Figure 14A was observed. As a result, the signal intensity (i.e., fluorescence intensity) was less than 0.1, 0.3, 0.6, 0.75, and 0.8 times the signal intensity in Figure 14A, with the signal intensity set to a reference value (e.g., 1). That is, signals were detected except when the core diameter of the second optical waveguide 230 was 50 μm, and the detected signal increased as the core diameter of the second optical waveguide 230 increased. Note that when the core diameter of the second optical waveguide 230 was 1.2 mm, it was not possible to fit the second optical waveguide 230 into a compact experimental system. Furthermore, similar experiments were carried out on other modified examples that utilize the first optical waveguide 212 and the second optical waveguide 230, and as a result, approximately the same ratio as above was obtained for the detected signal strength.

[0096] Although the present disclosure has been described above by explaining the embodiments, the above-described embodiments are merely examples, and the present disclosure is not limited to only the above-described embodiments. The scope of the present disclosure is defined by the claims in the scope of the claims, taking into consideration the description of the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wordings described therein. [Explanation of symbols]

[0097] 100, 200, 300, 400, 500, 600, 700 Diamond Sensor Unit 102, 202 Light-emitting element 104, 114, 124, 204, 208, 214, 224, 404, 406 Condenser element 106, 206 Excitation light generating unit 110, 210 Fluorescence Reflection Filter 112 Optical waveguide 116, 216, 402 Diamond elements 118, 218 Electromagnetic wave irradiation section 120, 220, 408, 502, 602, 702 Sensor part 122, 222, 908 LPF 126, 226 Light detection unit 128, 228 Light receiving section 140 Electromagnetic wave generator 142 Control Unit 212 1st optical waveguide 230 Second optical waveguide 250 Triangular Prism 252 Antenna 254, 288 connectors 260 Electrical Wiring 270 Glass epoxy board 272 Copper foil 280, 284, 912, 914, 916 boards 282 Conductive materials 286 Spacer 302 Excitation light reflection filter 900 LED 902 SPF 904 Diamond 906 Lens 910 Photodiode H interval L length

Claims

1. a sensor portion including a diamond having a color center with electron spin; an irradiation unit that irradiates the diamond with excitation light; a detector for detecting radiation from the color center of the diamond; an optical waveguide that transmits the excitation light and the emitted light; The diamond sensor unit, wherein the optical waveguide is disposed through at least one insulator.

2. the sensor unit includes a light-collecting element that collects the excitation light and the emitted light, The diamond sensor unit according to claim 1 , wherein the light-collecting element is disposed between the diamond and the optical waveguide.

3. the light-collecting element is a spherical lens formed on a silicon oxide base or a Fresnel lens formed on a silicon oxide base, 3. The diamond sensor unit according to claim 2, wherein the optical waveguide is an optical fiber having a core diameter of 1 μm or more and 80 μm or less.

4. the optical waveguide includes a medium for transmitting the excitation light and the emitted light; A diamond sensor unit as described in any one of claims 1 to 3, which includes a fluorescence reflection filter, LPF or dichroic mirror that separates the excitation light and the emitted light within a predetermined distance from one of the two ends of the optical waveguide that is located farther from the diamond.

5. the optical waveguide includes a first optical waveguide that transmits the excitation light and a second optical waveguide that transmits the emitted light; one end of the first optical waveguide is disposed closer to the diamond than the other end of the first optical waveguide; one end of the second optical waveguide is disposed closer to the diamond than the other end of the second optical waveguide; A diamond sensor unit as described in any one of claims 1 to 3, comprising a fluorescence reflection filter, LPF or dichroic mirror that separates the excitation light and the emitted light within a predetermined distance from the one end of the first optical waveguide and the one end of the second optical waveguide.

6. the first optical waveguide includes a first optical fiber; the second optical waveguide includes a second optical fiber; The diamond sensor unit according to claim 5 , wherein the core diameter of the second optical fiber is larger than the core diameter of the first optical fiber.

7. the core diameter of the first optical fiber is 1 μm or more and 100 μm or less; 7. The diamond sensor unit according to claim 6, wherein the core diameter of the second optical fiber is 1 μm or more and 1 mm or less.

8. the diamond has a plurality of flat faces; the excitation light is incident on a first flat surface of the plurality of flat surfaces; The diamond sensor unit according to any one of claims 5 to 7, wherein the detection unit detects the radiated light emitted from a second flat surface other than the first flat surface among the plurality of flat surfaces.

9. 9. The diamond sensor unit according to claim 1, wherein the sensor portion having the diamond is entirely made of an electrically insulating material.

10. A sensor portion including a diamond having a color center with electron spin; an irradiation unit that irradiates the diamond with excitation light; a detector for detecting radiation from the color center of the diamond; an optical waveguide that transmits the excitation light and the emitted light; the diamond is disposed on a transmission line that transmits microwaves or millimeter waves; The sensor unit is a diamond sensor unit that functions as a magnetic sensor.

11. the transmission line includes a main wiring arranged on a rectangular printed circuit board having a side of 5 cm or less, The diamond sensor unit according to claim 10, wherein a diamond is disposed at one end of the main wiring.

12. 12. The diamond sensor unit according to claim 1, wherein the spin coherence time of the diamond is less than 50 μsec.

13. A sensor portion including a diamond having a color center with electron spin; an irradiation unit that irradiates the diamond with excitation light; a detector for detecting radiation from the color center of the diamond; an optical waveguide that transmits the excitation light and the emitted light; A diamond sensor unit, wherein the total hydrogen concentration in the diamond is 1 ppm or less.

14. NVH in the diamond － concentration, CH concentration and CH ２ 13. The diamond sensor unit according to claim 1, wherein all of the concentrations are 1 ppm or less.

15. The diamond sensor unit according to claim 10 or 11; an electromagnetic wave generating unit that generates the microwave or the millimeter wave; a control unit that controls the irradiation unit, the detection unit, and the electromagnetic wave generation unit, The control unit irradiates the diamond with the microwaves or millimeter waves in a temporally and spatially combined manner together with the excitation light.

Images