Diamond magneto-optical sensor and diamond magneto-optical sensor system

Abstract

This diamond magneto-optical sensor includes: a diamond which includes a color center having electron spin, and to which excitation light is projected; and a projection unit that projects, to the diamond, the excitation light for the color center and electromagnetic waves for magnetic resonance. The projection unit receives modulated light which was amplitude modulated. The modulation frequency of the modulated light is within the microwave frequency band.

Description

Technical Field

[0001] The present disclosure relates to a diamond optical magnetic sensor and a diamond optical magnetic sensor system. This application claims priority based on Japanese Patent Application No. 2021-059797 filed on March 31, 2021, and incorporates all the descriptions set forth in the above Japanese Patent Application.

Background Art

[0002] Optical magnetic sensors using the NV center of diamond (hereinafter referred to as the NV center) are known. When the NV center, which consists of nitrogen that has entered the substitution position of carbon in diamond and a vacancy adjacent to the nitrogen, is negatively charged, its ground state becomes a triplet state (i.e., the spin S is S = 1). When the NV center is excited by light with a wavelength of 532 nm (i.e., green light), it emits fluorescence with a wavelength of 637 nm (i.e., red light). The emission intensity of the fluorescence changes depending on the spin state, and the spin state changes due to magnetic resonance by a magnetic field and microwaves or radio waves applied to the NV center. Therefore, it can be used as a diamond optical magnetic sensor.

[0003] A diamond optical magnetic sensor includes a diamond substrate containing an NV center, an optical system that transmits excitation light from a light source and irradiates the NV center, an optical system that condenses fluorescence from the NV center and transmits it to a photodetector, and a waveguide that transmits microwaves from a power source and irradiates the NV center.

[0004] For example, Non-Patent Document 1 below discloses a configuration in which a diamond sensor is placed on a coplanar waveguide and irradiated with microwaves. The shape of the diamond substrate is a rectangular parallelepiped, the excitation light is irradiated from the side of the diamond substrate, and the fluorescence is condensed from above the diamond substrate.

Prior Art Documents

Non-Patent Documents

[0005]

Non-Patent Document 1

[0006] A diamond magneto-optical sensor according to one aspect of the present disclosure includes a diamond having a color center with electron spin, which is irradiated with excitation light, and an irradiation unit that irradiates the diamond with electromagnetic waves for magnetic resonance, wherein the irradiation unit receives amplitude-modulated modulated light, and the modulation frequency of the modulated light is in the microwave frequency band.

[0007] A diamond magneto-optical sensor system relating to another aspect of the present disclosure includes the diamond magneto-optical sensor described above, an optical modulation unit that generates modulated light, and a transmission unit that transmits the modulated light, wherein the modulated light is transmitted via the transmission unit and received by an irradiation unit. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a block diagram showing a diamond magneto-optical sensor system according to an embodiment of the present disclosure. [Figure 2] Figure 2 is a block diagram showing the transmission paths of microwave and excitation light irradiated onto a diamond. [Figure 3] Figure 3 is a block diagram showing an example of the configuration of the optical power supply section in the diamond magneto-optical sensor system shown in Figure 1. [Figure 4] Figure 4 is a block diagram showing an example of a configuration for generating a reverse bias voltage, which differs from the configuration shown in Figure 3. [Figure 5] Figure 5 is a block diagram showing an example of a configuration for generating a reverse bias voltage, which differs from the configurations shown in Figures 3 and 4. [Figure 6] Figure 6 is a block diagram showing an example of the resonator configuration shown in Figure 3. [Figure 7] Figure 7 is a block diagram showing the optical power supply unit according to the first modified example. [Figure 8] Figure 8 is a block diagram showing the transmission paths of microwaves and excitation light irradiated onto the diamond in a diamond magneto-optical sensor system according to the second modified example. [Figure 9] Figure 9 is a block diagram showing the transmission paths of microwaves and excitation light irradiated onto the diamond in a diamond magneto-optical sensor system according to the third modified example. [Figure 10] Figure 10 is a block diagram showing the transmission paths of microwaves and excitation light irradiated onto the diamond in the diamond magneto-optical sensor system according to the fourth modified example. [Figure 11] Figure 11 is a schematic diagram showing the configuration of the measuring device used in the experiment. [Figure 12] Figure 12 is a perspective view showing the shape of the diamond used in the experiment. [Figure 13] Figure 13 is a graph showing the experimental results of transmitting microwaves using optical power supply. [Figure 14] Figure 14 is a graph showing the change in fluorescence intensity emitted from the NV center of a diamond. [Figure 15] Figure 15 is a graph showing the experimental results of transmitting microwaves through a coaxial cable. [Modes for carrying out the invention]

[0009] [Issues this disclosure aims to address] When using a diamond magneto-optical sensor for measurements in high-voltage power equipment, it is preferable to transmit the excitation light, fluorescence, and microwaves remotely while ensuring isolation to avoid dielectric breakdown due to the high voltage.

[0010] Regarding the transmission of excitation light and fluorescence, this can be done remotely while ensuring isolation by using optical fibers. Regarding microwave transmission, while ensuring isolation is difficult with coaxial cable transmission, it can be done remotely while ensuring isolation by using a transmitting antenna and a receiving antenna to transmit the microwaves as radio waves in space.

[0011] When microwave is transmitted spatially using a transmitting antenna and a receiving antenna, the frequency of the microwave that causes magnetic resonance of the NV center is about 3 GHz, and the wavelength of the microwave in space is about 10 cm. Therefore, the receiving antenna also needs to be about 10 cm in size. Since the antenna is composed of a conductor, in the measurement of high-voltage power equipment, it is necessary to consider ensuring insulation isolation and avoiding electric field concentration so as not to cause insulation breakdown. However, if the receiving antenna is as large as 10 cm, it is difficult to ensure insulation isolation and avoid electric field concentration. Also, radiating radio waves of about 3 GHz into the air is restricted by the Radio Law. Due to these constraints, there is a problem that free and flexible measurement cannot be performed.

[0012] Therefore, an object of the present disclosure is to provide a diamond optical magnetic sensor and a diamond optical magnetic sensor system that can be easily used for measurement in high-voltage power equipment.

[0013] [Effects of the Present Disclosure] According to the present disclosure, a diamond optical magnetic sensor and a diamond optical magnetic sensor system that can be easily used for measurement in high-voltage power equipment can be provided.

[0014] [Description of Embodiments of the Present Disclosure] The contents of the embodiments of the present disclosure will be listed and described. At least a part of the embodiments described below may be arbitrarily combined.

[0015] (1) The diamond optical magnetic sensor according to the first aspect of the present disclosure has a color center with electron spin, and includes a diamond irradiated with excitation light and an irradiation unit that irradiates the diamond with electromagnetic waves for magnetic resonance. The irradiation unit receives amplitude-modulated modulated light, and the modulation frequency of the modulated light is included in the frequency band of microwaves. Thereby, a diamond optical magnetic sensor that can be easily used for measurement in high-voltage power equipment can be realized. Since all the transmission paths of the excitation light, microwaves, and fluorescence transmitted between the diamond optical magnetic sensor and the measuring device are constituted by non-metallic members, it is easy to ensure insulation isolation to avoid dielectric breakdown in the measurement of high-voltage power equipment, and the freedom and flexibility of measurement are improved.

[0016] (2) The irradiation unit can further include a photoelectric conversion unit that converts the modulated light into an electrical signal. The electromagnetic wave for magnetic resonance is formed by the electrical signal generated by the photoelectric conversion unit and can be irradiated onto the diamond. Thereby, since electromagnetic waves (i.e., microwaves) are not transmitted in space using an antenna or the like, it is not subject to the restrictions of the Radio Law. Therefore, the measurement environment is not limited to within a shielded room, and measurement can be performed in any environment.

[0017] (3) The photoelectric conversion unit may include a photodiode that converts the modulated light into an electrical signal. The irradiation unit may further include a first bias tee that extracts an AC component from the electrical signal generated by the photodiode. The electromagnetic wave for magnetic resonance may be formed by the AC component. Thereby, the diamond optical magnetic sensor can be made more compact than the wavelength of the electromagnetic wave used for measurement (i.e., about 10 cm) and can be housed in a case without corners such as a sphere. Therefore, it is easy to avoid electric field concentration in the measurement of high-voltage power equipment.

[0018] (4) The photoelectric conversion unit may include a photoelectric conversion element that converts a portion of the light, including at least one of the light from the light emitter, modulated light, and excitation light, into an electric potential, and the first bias tee may extract the AC component from the electrical signal by applying the electric potential generated by the photoelectric conversion element. This enables electrical isolation between the diamond and the light source and microwave source. It also extends the lifespan of the diamond magneto-optical sensor.

[0019] (5) The photoelectric conversion unit may include a photoelectric conversion element that converts a portion of the light, including at least one of the light from the light source, modulated light, and excitation light, into power, and an amplifier that amplifies the output signal of the photodiode or the first bias tee, and the output signal may be amplified by applying the power generated by the photoelectric conversion element to the amplifier. This enables electrical isolation between the diamond and the light source and microwave source, allows for irradiation of the diamond with higher power microwaves, and enables more sensitive magnetic detection. It also extends the lifespan of the diamond magneto-optical sensor.

[0020] (6) The wavelength of the carrier wave of the modulated light may be different from that of the excitation light. This allows for easy transmission of both the modulated light and the excitation light using the same optical fiber, thereby reducing the number of components.

[0021] (7) The wavelength of the carrier wave of the modulated light may be included in the near-infrared wavelength band. This facilitates the generation and transmission of the modulated light.

[0022] (8) The excitation light may have the same wavelength as the carrier wave of the modulated light, and the modulated light may be generated by amplitude modulation of the excitation light. This reduces the number of components because only the excitation light needs to be generated.

[0023] (9) The modulated light may be laser light. This allows the intensity of the modulated light to be increased and the modulated light to be transmitted over a longer distance.

[0024] (10) Modulated light may be output from a laser diode by controlling the drive current of the laser diode to change at the modulation frequency. This allows modulated light to be easily generated by the direct modulation method and enables miniaturization of the modulation device.

[0025] (11) Modulated light may be output from an LN element to which laser light is input, by controlling the LN element with a modulation signal of the modulation frequency. This enables high-speed modulation and generates modulated light with a high modulation frequency.

[0026] (12) The drive current of the laser diode may be controlled by a second bias tee. This allows modulated light to be easily generated using the laser diode.

[0027] (13) The excitation light may be laser light. This allows for easy generation of excitation light using a laser diode or the like.

[0028] (14) The modulated light may be transmitted via the first optical fiber and received by the irradiator. This ensures reliable transmission of the modulated light to the irradiator. Furthermore, the diamond magneto-optical sensor can be safely used in high-voltage power equipment.

[0029] (15) The excitation light may be transmitted through a second optical fiber and irradiated onto the diamond. This ensures reliable transmission of the excitation light to the irradiating part. Furthermore, the diamond magneto-optical sensor can be safely used in high-voltage power equipment.

[0030] (16) The excitation light may be transmitted through the first optical fiber and irradiated onto the diamond. This allows the modulated light and the excitation light to be transmitted through a single optical fiber, reducing the number of components and simplifying manufacturing.

[0031] (17) The irradiation section may include a resonator, and the diamond may be placed in the resonator. This allows the diamond to be efficiently irradiated with electromagnetic waves (i.e., microwaves).

[0032] (18) The diamond may be positioned within 5 mm of the photoelectric conversion unit. This allows the diamond to be irradiated with high-power electromagnetic waves (i.e., microwaves).

[0033] (19) The irradiation unit may irradiate the diamond with the input modulated light as an electromagnetic wave for magnetic resonance. This eliminates the need for a photoelectric converter that converts the modulated light into an electrical signal, reduces the number of parts, and simplifies manufacturing.

[0034] (20) The diamond magneto-optical sensor may further include a housing formed in a smooth shape by a conductive material, and the diamond and the irradiation part may be housed in the housing. This allows the diamond magneto-optical sensor to be used safely in high-voltage power equipment.

[0035] (21) The diamond magneto-optical sensor system according to the second aspect of the present disclosure includes the diamond magneto-optical sensor described above, an optical modulation unit that generates modulated light, and a transmission unit that transmits the modulated light, wherein the modulated light is transmitted via the transmission unit and received by the irradiation unit. As a result, the transmission paths of the excitation light, microwaves, and fluorescence transmitted between the diamond magneto-optical sensor and the measuring instrument can all be made of non-metallic materials, making it easy to ensure insulating separation to avoid dielectric breakdown when measuring in high-voltage power equipment, and improving the freedom and flexibility of measurement. Furthermore, since electromagnetic waves (i.e., microwaves) are not transmitted through space using an antenna or the like, it is not subject to the restrictions of the Radio Law.Therefore, the measurement environment is not limited to inside a shielded room, and measurements can be taken in any environment. Furthermore, since microwaves are not transmitted through space using an antenna or the like, it is not subject to the restrictions of the Radio Law.Therefore, the measurement environment is not limited to inside a shielded room, and measurements can be taken in any environment.

[0036] [Details of the embodiments of this disclosure] In the following embodiments, identical parts are assigned the same reference numeral. Their names and functions are also identical. Therefore, detailed descriptions of them will not be repeated.

[0037] Referring to Figure 1, the diamond magneto-optical sensor system 100 according to the embodiment of this disclosure includes a diamond 104, a photoelectric conversion unit 106, a transmission unit 108, a modulation signal generation unit 110, an optical modulation unit 112, an optical fiber 114, an excitation light generation unit 120, a demultiplexer 122, a light concentrator 124, an optical fiber 126, and a control unit 130. The diamond 104 includes an NV center. Microwaves are supplied to the diamond 104 by optical power supply. The diamond 104, the photoelectric conversion unit 106, and the transmission unit 108 constitute a diamond magneto-optical sensor. When measurements are performed by the diamond magneto-optical sensor system 100 in high-voltage power equipment, etc., it is preferable that the diamond 104, the photoelectric conversion unit 106, and the transmission unit 108 are housed in a conductive case 102 made of metal or the like to avoid electric field concentration. As described later, the control unit 130 controls the modulation signal generation unit 110 and the excitation light generation unit 120 to irradiate the diamond 104 with microwaves and excitation light, detects the fluorescence emitted from the diamond 104 with the detection unit 128, and acquires it as measurement data. The control unit 130 is implemented by a CPU (Central Processing Unit), a microcomputer, etc.

[0038] The modulation signal generation unit 110, under the control of the control unit 130, generates a signal of a predetermined frequency (i.e., the microwave frequency band) and inputs it to the optical modulation unit 112. The optical modulation unit 112 amplitude modulates light of the predetermined frequency using the signal supplied from the modulation signal generation unit 110, generating and outputting modulated light. In other words, the signal output by the modulation signal generation unit 110 is the modulation signal used to generate the modulated light. The frequency of the signal output by the modulation signal generation unit 110 is the modulation frequency. The light of the predetermined frequency to be modulated is the carrier wave. The modulated light generated by the optical modulation unit 112 is transmitted to the photoelectric conversion unit 106 via the optical fiber 114.

[0039] The photoelectric conversion unit 106 converts the modulated light transmitted via the optical fiber 114 into an electrical signal (i.e., photoelectric conversion) and inputs it to the transmission unit 108. This generates an electrical signal having the frequency of its carrier wave (i.e., the microwave frequency band) from the modulated light and supplies it to the transmission unit 108. The transmission unit 108 increases the input electrical signal, i.e., current, and transmits it to the diamond 104. The electromagnetic waves formed by the electrical signal transmitted through the transmission unit 108 irradiate the diamond 104 and are used for magnetic resonance of the NV center. In other words, the photoelectric conversion unit 106 and the transmission unit 108 constitute the irradiation unit 116, and the modulated signal generation unit 110, the optical modulation unit 112, the optical fiber 114, and the irradiation unit 116 constitute the optical power supply unit 118 for irradiating the diamond 104 with microwaves.

[0040] The excitation light generation unit 120, under the control of the control unit 130, generates and outputs excitation light (i.e., green light) for the NV center. The excitation light generated by the excitation light generation unit 120 is reflected by the demultiplexer 122, focused by the light concentrator 124, and incident on the optical fiber 126. The demultiplexer 122 reflects or transmits the incident light according to the wavelength of the incident light. The demultiplexer 122 is, for example, a dichroic mirror, which reflects green excitation light and transmits red fluorescence. The optical fiber 126 transmits the input excitation light to the diamond 104. As a result, the excitation light irradiates the diamond 104, and fluorescence (i.e., red light) is emitted from the NV center of the diamond 104. The fluorescence emitted from the diamond 104 is incident on the optical fiber 126, transmitted through the optical fiber 126, and emitted from the output end of the optical fiber 126. Fluorescence emitted from the output end of the optical fiber 126 is converted into parallel light by the light-collecting unit 124, passes through the demultiplexer 122, and enters the detection unit 128. The detection unit 128 detects the intensity of the incident fluorescence. The control unit 130 acquires the signal detected by the detection unit 128 as measurement data. This enables the measurement of magnetic fields and other parameters using the diamond magneto-optical sensor system 100.

[0041] As described above, in the diamond magneto-optical sensor system 100, the microwaves irradiated onto the diamond 104 are supplied by optical power. That is, referring to Figure 2, the microwaves irradiated onto the diamond 104 are transmitted as light (i.e., modulated light) via the optical fiber 114 to near the diamond 104, and then converted into an electrical signal to become electromagnetic waves (i.e., microwaves). On the other hand, the excitation light for the NV center is output from the excitation light generation unit 120 and transmitted to the diamond 104 via the optical fiber 126. The fluorescence emitted from the NV center is transmitted to the detection unit 128 via the optical fiber 126. In this way, by using optical power supply, the transmission paths for the excitation light, microwaves, and fluorescence transmitted between the diamond magneto-optical sensor and the measuring instrument can all be made of non-metallic materials (e.g., optical fibers). Therefore, in measurements with high-voltage power equipment, it is easy to ensure the necessary isolation distance to avoid dielectric breakdown, improving the freedom and flexibility of measurement.

[0042] The optical power supply section 118 of the diamond magneto-optical sensor system 100 will be described in more detail. Referring to Figure 3, the modulation signal generation section 110 (see Figure 1) includes a VCO 140, an attenuator 142, an amplifier 144, a circulator 146, and a terminator 148. The optical modulation section 112 (see Figure 1) includes a bias tee 150, a current source 152, and an LD (laser diode) 154. The optical fiber 114 (see Figure 1) includes an optical fiber 156. The photoelectric conversion section 106 (see Figure 1) includes a PD (photodiode) 158, a bias tee 160, and a voltage source 162. If it is necessary to amplify the signal photoelectrically converted by the photoelectric conversion section 106, a power amplifier may be included between the PD 158 and the bias tee 160, or downstream of the bias tee 160. The transmission section 108 (see Figure 1) includes a circulator 164, a terminator 166, and a resonator 168.

[0043] The VCO 140 generates and outputs an electrical signal with a constant frequency. This constant frequency falls within the microwave frequency band. The output signal of the VCO 140 is shaped into a signal of a predetermined level without changing its frequency by the attenuator 142 and amplifier 144. The circulator 146 supplies the signal supplied from amplifier 144 to bias tee 150. A portion of the signal supplied from circulator 146 to bias tee 150 may be reflected and input back into circulator 146. To prevent this from affecting the output signal of amplifier 144, circulator 146 diverts the signal returning from bias tee 150 to terminator 148, as indicated by the dashed arrow, and consumes it. Terminator 148 is, for example, a 50Ω terminator.

[0044] The bias tee 150 outputs a constant current supplied by the current source 152 by adding a constant frequency signal supplied by the circulator 146. The current source 152 functions as a constant current source to supply the drive current (i.e., bias current) for the LD154. The LD154 is driven by the output signal from the bias tee 150 and outputs laser light. Since the output signal from the bias tee 150 is a constant level current superimposed with a constant frequency (i.e., microwave frequency) supplied by the circulator 146, the laser light output from the LD154 becomes amplitude-modulated light (i.e., modulated light). That is, the LD154 is controlled by a direct modulation method and outputs modulated light. The constant frequency (i.e., microwave frequency) supplied by the circulator 146 functions as the modulation signal for the modulated light output from the bias tee 150.

[0045] The modulated light output from LD154 is transmitted to PD158 via optical fiber 156. PD158 performs photoelectric conversion on the modulated light input from optical fiber 156. For PD158 to perform photoelectric conversion, a reverse bias voltage must be applied to PD158. The reverse bias voltage is supplied from voltage source 162 and applied to PD158 via bias tee 160. Voltage source 162 is a power supply that outputs a constant voltage, such as a battery (e.g., a dry cell). Preferably, instead of a battery, a photoelectric conversion element that converts light into electric potential is used. The light irradiated onto the photoelectric conversion element may be natural light, but as described later, a light source may be provided to generate light. More preferably, as described later, it is efficient to irradiate the photoelectric conversion element with a portion of the modulated or excitation light irradiated onto the diamond, or with the leakage light of fluorescence emitted from the diamond. In this way, electrical isolation between the diamond and the light source and microwave source is achieved by using a battery or a mechanism that generates electric potential using light. Although a configuration using a light source is more complex in mechanism than a configuration using batteries, the lifespan of the diamond magneto-optical sensor system 100 is longer.

[0046] PD158 converts the modulated light input from the optical fiber 156 into an electrical signal and outputs it to the bias tee 160. The electrical signal output from PD158 is a signal in which an AC component having the same frequency as the modulation frequency (i.e., microwave frequency) of the modulated light is superimposed on a DC component. As described above, the electrical signal output from PD158 may be amplified by a power amplifier and input to the bias tee 160, or the electrical signal output from the bias tee 160 may be power amplified. The power used for the power amplifier is supplied, for example, by a battery. Preferably, instead of a battery, a photoelectric conversion element that converts light into electricity is used. The light irradiated onto the photoelectric conversion element may be natural light, but a light source may be provided to generate light. More preferably, it is efficient to irradiate the photoelectric conversion element with a portion of the modulated light or excitation light irradiated onto the diamond, or with the leakage light of fluorescence emitted from the diamond. Thus, by using a battery or a mechanism that generates power using light, electrical isolation is achieved between the diamond and the light source and microwave source, allowing for higher-power microwave irradiation of the diamond and enabling more sensitive magnetic detection. Although the configuration using a light source is more complex in mechanism than the configuration using a battery, the lifespan of the diamond magneto-optical sensor system 100 is extended.

[0047] The bias tee 160 adds a constant voltage supplied from the voltage source 162 (i.e., the reverse bias voltage of the PD158) to the signal input from the PD158 and outputs it. In other words, the bias tee 160 cuts the DC component from the signal input from the PD158 and outputs the AC component.

[0048] The voltage source 162 for supplying the reverse bias voltage to PD158 is not limited to the dry cell battery described above. The reverse bias voltage may be generated using a photoelectric conversion element. For example, as shown in Figure 4, a solar cell 300 and a floodlight 302 may be used instead of the voltage source 162 in Figure 3. Alternatively, as shown in Figure 5, a photodiode 304 may be used instead of the voltage source 162. Both Figures 4 and 5 are extracted portions of the configuration shown in Figure 3, including the bias tee 160.

[0049] Referring to Figure 4, the solar cell 300 is illuminated by light output from the floodlight 302 and generates a DC voltage. The light output from the floodlight 302 is shown by a dashed line. The generated DC voltage is supplied to the bias tee 160 as the reverse bias voltage for PD158. This cuts off the DC component from the signal input to the bias tee 160 from PD158, and only the AC component is output. Note that the light irradiated onto the solar cell 300 is not limited to the light output from the floodlight 302. Natural light may be irradiated onto the solar cell 300. Also, as will be described later, a portion of the modulated light or excitation light, or the leakage light of fluorescence emitted from the diamond may be irradiated onto the solar cell 300.

[0050] Referring to Figure 5, the photodiode 304 is irradiated with leaked excitation light 306, which is part of the excitation light irradiated onto the diamond 104 (see Figure 3), and generates a DC voltage. The generated DC voltage is supplied to the bias tee 160 as the reverse bias voltage of PD158. As a result, the DC component is cut from the signal input to the bias tee 160 from PD158, and only the AC component is output. Note that the light irradiated onto the photodiode 304 is not limited to leaked excitation light 306. Natural light may be irradiated onto the photodiode 304. Alternatively, part of the modulated light input to PD158 from the optical fiber 156 (see Figure 3) may be irradiated onto the photodiode 304. In this case, general electronic circuit measures such as using a Zener diode are necessary to keep the output potential of the photodiode constant. Alternatively, part of the leaked fluorescence light from the diamond may be irradiated onto the photodiode 304.

[0051] The AC signal (i.e., microwave) output from the bias tee 160 is input to the circulator 164. The circulator 164 outputs the signal supplied from the bias tee 160 to the resonator 168. A portion of the signal supplied from the circulator 164 to the resonator 168 may be reflected and input back into the circulator 164. To prevent this from affecting the output signal of the bias tee 160, the circulator 164 diverts the signal returning from the resonator 168 to the terminator 166, as indicated by the dashed arrow, and dissipates it. The terminator 166 is, for example, a 50Ω terminator.

[0052] The resonator 168 amplifies the supplied microwaves and irradiates the diamond 104. The resonator 168 includes, for example, an impedance transducer 170 and a resonator 172, with reference to Figure 6. The diamond 104 is located in the vicinity of the resonator 172 (including inside the resonator 172). The impedance transducer 170 is, for example, a λ / 4 transformer, and the resonator 172 is, for example, a λ / 4 stub. The resonator 172 is, for example, a stub (i.e., a λ / 4 open stub) formed by two parallel copper wires, each one-quarter the length of the electric length of the microwave, with the end opposite to the end connected to the impedance transducer 170 being open. The resonator 172 may also be, for example, a stub (i.e., a λ / 4 short stub) formed by two parallel, opposing copper foils, each one one-quarter the length of the electric length of the microwave, with the ends opposite to the end connected to the impedance transducer 170 being connected (i.e., shorted). The impedance converter 170 allows the impedance of the circulator 164 to be lowered or raised relative to the resonator 172. The resonator 172 functions as a series or parallel resonant circuit, increasing the supplied microwaves. This causes microwaves to irradiate the diamond 104, causing magnetic resonance at the NV center of the diamond 104. The resonator 168 may be a resonator of a microstrip line or a resonator of a coplanar waveguide.

[0053] As described above, the transmission paths for excitation light, microwaves, and fluorescence transmitted between the diamond magneto-optical sensor (i.e., diamond 104, photoelectric conversion unit 106, and transmission unit 108) and the measuring instrument (i.e., detection unit 128, control unit 130, etc.) can be constructed entirely from non-metallic optical fibers 114 and 126 (see Figure 1). Therefore, in measurements of high-voltage power equipment, it is easy to ensure sufficient insulation separation to avoid dielectric breakdown, improving the freedom and flexibility of measurement.

[0054] Since electromagnetic waves (i.e., microwaves) are not transmitted through space using antennas or the like, it is not subject to the restrictions of the Radio Law. Therefore, the measurement environment is not limited to a shielded room, and measurements can be taken in any environment. In addition, the diamond magneto-optical sensor (i.e., diamond 104, photoelectric conversion unit 106, and transmission unit 108) can be made more compact than the wavelength of the electromagnetic waves used for measurement (for example, about 10 cm) and can be housed in a rounded case such as a sphere. Therefore, it is easy to avoid electric field concentration when measuring high-voltage power equipment.

[0055] The above describes a case where a diamond magneto-optical sensor includes an NV center and microwaves are transmitted by optical power supply, but it is not limited to this. Any sensor that utilizes light whose intensity is modulated to a frequency in the electromagnetic wave region (i.e., modulated light) is acceptable. Preferably, electromagnetic waves are transmitted by optical power supply. More preferably, electromagnetic waves in the microwave frequency band are transmitted by optical power supply. Even more preferably, electromagnetic waves with a frequency of 1 GHz to 5 GHz are transmitted by optical power supply.

[0056] As mentioned above, it is preferable to generate microwaves from modulated light using PD158, but it is not limited to this. Any device that performs discharge conversion or a sensor that utilizes an element will suffice.

[0057] The wavelength of the carrier wave of the modulated light is preferably within the near-infrared wavelength band. This facilitates the generation and transmission of the modulated light.

[0058] As mentioned above, the modulated light is the laser light output from the LD154. This allows the intensity of the modulated light to be increased, and thus the modulated light to be transmitted over longer distances.

[0059] As described above, modulated light is the light output from LD154 by controlling the drive current of LD154 supplied by the current source 152 so that it changes at the modulation frequency. This allows modulated light to be easily generated by the direct modulation method, and the modulation device can be miniaturized.

[0060] As described above, the drive current of the LD154 supplied by the current source 152 is controlled by the bias tee 150. This makes it easy to generate modulated light using the LD154.

[0061] As described above, the excitation light is laser light. This allows the excitation light to be easily generated using the excitation light generation unit 120.

[0062] As described above, the modulated light is transmitted via the optical fiber 114 and received by the irradiation unit 116. This ensures reliable transmission of the modulated light to the irradiation unit 116. Furthermore, the diamond magneto-optical sensor can be safely used in high-voltage power equipment.

[0063] As described above, the excitation light is transmitted via the optical fiber 126 and irradiated onto the diamond 104. This ensures reliable transmission of the excitation light. Furthermore, the diamond magneto-optical sensor can be safely used in high-voltage power equipment.

[0064] As described above, it is preferable that the transmission unit 108 includes a resonator 168 and that the diamond 104 is placed in the resonator 168. This allows the diamond to be efficiently irradiated with electromagnetic waves (i.e., microwaves).

[0065] Preferably, the diamond 104 is positioned within 10 mm of the PD158. More preferably, the diamond 104 is positioned within 5 mm of the PD158. Even more preferably, the diamond 104 is positioned within 3 mm of the PD158. This allows the diamond 104 to irradiate with powerful electromagnetic waves (i.e., microwaves).

[0066] As described above, the diamond 104, the photoelectric conversion unit 106, and the transmission unit 108 are preferably housed in a conductive case 102 to avoid electric field concentration. The case 102 includes an opening for passing an optical fiber 114 for transmitting modulated light to the photoelectric conversion unit 106 and an optical fiber 126 for transmitting excitation light to the diamond 104, and is preferably substantially sealed. The outer shape of the case 102 does not need to be sharp and is smoothly formed, and is preferably spherical or ellipsoidal in shape. This allows the diamond magneto-optical sensor to be used safely in high-voltage power equipment and the like.

[0067] (First variation) In the above, modulated light was generated by a direct modulation method, but modulated light may also be generated by an external modulation method. The optical power supply unit 118 shown in Figure 1 may be configured as shown in Figure 7. The optical power supply unit according to the first modified example generates modulated light by an external modulation method.

[0068] The only difference between the configuration shown in Figure 7 and that in Figure 3 is the configuration of the optical modulation unit 112. The other configurations in Figure 7 are the same as in Figure 3. Therefore, in the following, we will mainly explain the differences without repeating explanations. Referring to Figure 7, as described above, the constant frequency electrical signal output from the VCO 140 is transmitted to the circulator 146 via the attenuator 142 and amplifier 144, and supplied from the circulator 146 to the LN element 180. The signal supplied from the circulator 146 to the LN element 180 is the modulation signal used to generate modulated light, as will be described later.

[0069] The current source 152 is a constant current source and supplies a drive current (i.e., bias current) to the LD154 to drive it. The LD154 is driven by the output signal from the bias tee 150 and outputs laser light with constant frequency and amplitude. The laser light output from the bias tee 150 is input to the LD154 via the optical fiber 182. The LN element 180 is an optical modulator formed of lithium niobate (LiNbO3). The LN element 180 amplitude modulates the input laser light using the signal from the circulator 146 as the modulation signal and outputs modulated light. That is, the LN element 180 generates modulated light by an external modulation method. As described above, the modulated light output from the LN element 180 is transmitted to the PD158 via the optical fiber 156, where it is photoelectrically converted into microwaves and irradiated onto the diamond 104 via the resonator 168.

[0070] By employing the optical power supply unit shown in Figure 7, the transmission paths for excitation light, microwaves, and fluorescence transmitted between the diamond magneto-optical sensor (i.e., diamond 104, photoelectric conversion unit 106, and transmission unit 108) and the measuring instrument (i.e., detection unit 128 and control unit 130, etc.) can be constructed entirely from non-metallic optical fibers 114 and 126 (see Figure 1). Therefore, in measurements of high-voltage power equipment, it is easy to ensure sufficient isolation to avoid dielectric breakdown, improving the freedom and flexibility of measurement. Since electromagnetic waves (i.e., microwaves) are not transmitted through space using antennas, etc., it is not subject to the restrictions of the Radio Law. Therefore, the measurement environment is not limited to a shielded room, and measurements can be performed in any environment. Furthermore, the diamond magneto-optical sensor (i.e., diamond 104, photoelectric conversion unit 106, and transmission unit 108) can be made more compact than the wavelength of the electromagnetic waves used for measurement (for example, about 10 cm), and can be housed in a rounded case such as a sphere. Therefore, in measurements of high-voltage power equipment, it is easy to avoid electric field concentration.

[0071] By using the LN element 180 and generating modulated light by an external modulation method, high-speed modulation is possible, and modulated light with a high modulation frequency (e.g., several tens of GHz) can be generated.

[0072] (Second variation) The above describes a case in which the modulated light for optical power supply and the excitation light are transmitted to the vicinity of the diamond 104 using different optical fibers (i.e., optical fibers 114 and 126), as shown in Figure 2, but the invention is not limited to this. In the diamond magneto-optical sensor system according to the second modified example, the modulated light for optical power supply and the excitation light are transmitted using the same optical fiber.

[0073] Referring to Figure 8, the modulated light output from the optical modulation unit 112 (see Figure 1) and the excitation light output from the excitation light generation unit 120 are both transmitted through the optical fiber 190. The carrier frequency of the modulated light is different from the frequency of the excitation light. The modulated light output from the output end of the optical fiber 190 is input to the photoelectric conversion unit 106, where it is photoelectrically converted as described above to generate microwaves. The generated microwaves are irradiated onto the diamond 104. On the other hand, the excitation light output from the output end of the optical fiber 190 is directly irradiated onto the diamond 104. The fluorescence emitted from the diamond 104 may be transmitted to the detection unit 128 via another optical fiber, or it may be transmitted to the detection unit 128 via the demultiplexer 192. In this way, by having a different wavelength for the carrier wave of the modulated light than for the excitation light, the modulated light and the excitation light can be easily transmitted using the same optical fiber, and the number of components can be reduced.

[0074] To input the modulated light and the excitation light into the optical fiber 190, optical elements should be arranged at the input end of the optical fiber 190 so that the optical paths of the modulated light and the excitation light overlap. For example, if the carrier wave of the modulated light and the excitation light have different frequencies (i.e., different wavelengths), a dichroic mirror can be used. For example, the modulated light can pass through the dichroic mirror and enter the optical fiber 190, and the excitation light can be reflected by the dichroic mirror and enter the optical fiber 190.

[0075] (Third variation) The above describes a case where modulated light and excitation light with different frequencies (i.e., different wavelengths) are transmitted to the vicinity of the diamond 104 using the same optical fiber 190, as shown in Figure 8, but the invention is not limited to this. In the diamond magneto-optical sensor system according to the third modified example, modulated light and excitation light with the same frequency (i.e., the same wavelength) are transmitted using the same optical fiber.

[0076] Referring to Figure 9, the modulated excitation light is transmitted via the optical fiber 190. The modulated excitation light is generated by amplitude modulation of the excitation light from the NV center, using a microwave frequency signal as the modulation signal. The carrier frequency of the modulated excitation light is the same as the frequency of the excitation light. The modulated excitation light output from the output end of the optical fiber 190 is separated into two optical paths by the distributor 194. The light from the first optical path is input to the photoelectric converter 106, where it is photoelectrically converted as described above to generate microwaves. The generated microwaves are irradiated onto the diamond 104. On the other hand, the light from the second optical path is directly irradiated onto the diamond 104 as excitation light.

[0077] The modulated excitation light incident on the optical fiber 190 can be generated by externally modulating the excitation light output from the excitation light generation unit 120 (see Figure 1) using the LN element 180, as shown in Figure 7. By modulating the excitation light, there is no need to provide an LD (LD154 shown in Figures 3 and 7) for generating the modulated light, which reduces the number of components and simplifies manufacturing.

[0078] (Fourth variation) The above describes a case in which modulated light is photoelectrically converted by the photoelectric conversion unit 106 to generate microwaves, but the system is not limited to this. In the diamond magneto-optical sensor system according to the fourth modified example, the modulated light is directly irradiated onto the diamond 104.

[0079] Referring to Figure 10, the modulated excitation light is transmitted via the optical fiber 190, similar to Figure 9. The modulated excitation light is generated by amplitude modulating the excitation light of the NV center with a microwave frequency signal as the modulation signal. The modulated excitation light output from the output end of the optical fiber 190 is directly irradiated onto the diamond 104. That is, the modulated excitation light is used as the excitation light for the NV center and as microwaves for magnetic resonance. This eliminates the need for the photoelectric conversion unit 106 for photoelectric conversion, reduces the number of parts, and simplifies manufacturing.

[0080] The above describes a case where the diamond magneto-optical sensor contains NV centers, but it is not limited to this. Any diamond magneto-optical sensor having color centers with electron spin is acceptable. Color centers with electron spin are centers that form a spin triplet state and emit light when excited, with NV centers being a typical example. In addition, it is known that color centers with electron 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, diamonds containing these may be used instead of diamonds containing NV centers to construct a diamond magneto-optical sensor.

[0081] The above describes the transmission of modulated light to near a diamond using an optical fiber, but it is not limited to this. Instead of an optical fiber, lenses and mirrors may be used to transmit the modulated light in space. [Examples]

[0082] The following examples illustrate the effectiveness of this disclosure. Using a measuring apparatus with the configuration shown in Figure 11, a diamond having an NV center was irradiated with microwaves and excitation light, and the fluorescence intensity emitted from the NV center was measured. Referring to Figure 11, the diamond magneto-optical sensor 216 in the measuring apparatus consisted of the diamond 104, photoelectric conversion unit 106, and transmission unit 108 shown in Figure 3. However, in Figure 11, the diamond 104 in Figure 3 is replaced by diamond 210. The microwave supply source 220 (i.e., microwave system) for irradiating the diamond 210 with microwaves used the modulation signal generation unit 110, optical modulation unit 112, and optical fiber 156 shown in Figure 3, and the modulated light was transmitted to the diamond magneto-optical sensor 216. The configuration for irradiating the diamond 210 contained in the diamond magneto-optical sensor 216 with excitation light (i.e., irradiation system) includes a light source 200, a collimating lens 202, a dichroic mirror 204, a spherical lens 206, and an optical fiber 208. The configuration for observing fluorescence emitted from the diamond 210 (i.e., the observation system) includes an optical fiber 208, a spherical lens 206, a dichroic mirror 204, an LPF (Long Pass Filter) 212, and a photodetector 214.

[0083] Referring to Figure 3, an electrical signal with a predetermined frequency of 3 dBm was output from VCO140. The predetermined frequency was varied within the range of 2.7 GHz to 2.94 GHz. The output signal of VCO140 was attenuated by -20 dB by attenuator 142, amplified by +40 dB by amplifier 144, and input to circulator 146. A Thorlabs LPSC-1550-FC was used for LD154, and a bias current of 130 mA was output from current source 152 and supplied to LD154 via bias tee 150 to generate modulated light using the direct modulation method. The modulated light, which included a DC component of 15 mW and an AC component of 10 mWrms (RMS), was transmitted via optical fiber 156 to diamond magneto-optical sensor 216. A Thorlabs FGA01FC was used for PD158, which constitutes the diamond magneto-optical sensor 216. A dry cell battery was used as the voltage source 162, and a 9V reverse bias voltage was output from the voltage source 162 and supplied to the PD158 via the bias tee 160, generating a microwave electrical signal by photoelectric conversion. The generated microwave was transmitted to the resonator 168 via a circulator 164 with a characteristic impedance of 50Ω. The resonator 168 used a λ / 4 transformer and a λ / 4 open stub resonator.

[0084] As a comparative example, instead of the microwave supply source 220, microwaves generated by a microwave generator (not shown) were transmitted using a coaxial cable with a characteristic impedance of 50 Ω and irradiated onto the diamond 210 through the resonator of the coplanar waveguide described above. The frequency of the microwaves transmitted through the coaxial cable was also varied within the range of 2.74 GHz to 2.94 GHz.

[0085] A laser diode (LD) element (specifically, a Thorlabs L515A1) was used as the light source 200 to generate excitation light, producing 5mW of green laser light (i.e., excitation light). The excitation light output from the light source 200 was focused by a collimating lens 202 and then incident on a dichroic mirror 204. A Thorlabs LA1116-A was used as the collimating lens 202, and a Suruga Seiki Co., Ltd. SO6-RG was used as the dichroic mirror 204. The excitation light (i.e., green light) incident on the dichroic mirror 204 was reflected by the dichroic mirror 204. The reflected light was focused by a spherical lens 206 and incident on an optical fiber 208 (specifically, the core), transmitted through the optical fiber 208, and then irradiated onto a diamond 210. An Opto Sigma MS-08-4.35P1 (8mm in diameter) was used as the spherical lens 206. Optical fiber 208 used an optical digital cable with a core diameter of φ0.9 mm.

[0086] Fluorescence emitted from the diamond 210 that entered the optical fiber 208 was propagated through the optical fiber 208, then made into parallel light by the spherical lens 206, and entered the dichroic mirror 204. The fluorescence (i.e., red light) that entered the dichroic mirror 204 passed through the dichroic mirror 204 and entered the LPF 212. The fluorescence that passed through the LPF 212 was detected by the photodetector 214. The LPF 212 allows light with wavelengths above a predetermined wavelength to pass through and cuts (e.g., reflects) light with wavelengths below a predetermined wavelength. An LOPF-25C-593 manufactured by Opto Sigma was used for the LPF 212. A photodiode (specifically, an S6967 manufactured by Hamamatsu Photonics K.K.) was used for the photodetector 214. The synchrotron radiation from the diamond is red light and passes through the LPF 212, but the excitation light has a shorter wavelength and therefore does not pass through the LPF 212. This suppresses the decrease in detection sensitivity caused by excitation light emitted from the light source 200 being detected by the photodetector 214 and becoming noise.

[0087] For Diamond 210, we used type Ib diamond, with an electron beam acceleration energy of 3 MeV and an electron beam dose of 3 × 10⁻¹⁶. 18 pieces / cm 2 Electrons were injected, and then the diamond containing NV centers was produced by annealing at 800°C for about 1 hour. As shown in Figure 12, this was cut into a corner cube with a hypotenuse of 1 mm to produce diamond 210. The diamond shown in Figure 12 is a triangular pyramid with points A, B, C, and D as vertices, and angles α, β, and γ all being right angles. Excitation light (i.e., green light) is incident from the optical fiber 208 described above, perpendicular to the plane of triangle ABC. The excitation light incident inside the diamond is internally reflected by the three planes that function as reflective surfaces (i.e., triangles ABD, BCD, and ACD) because the refractive index of diamond is approximately 2.5, and travels a longer optical path than if it were not reflected, irradiating the NV centers. The fluorescence (i.e., red light) emitted from the NV centers is internally reflected by the three planes that function as reflective surfaces, and is output from the plane of triangle ABC from which the excitation light was incident, and is incident on the optical fiber 208 described above.

[0088] As described above, Figure 13 shows the results of measuring the fluorescence emitted from the diamond 210 after irradiating it with microwaves supplied by light using the microwave power source 220. In Figure 13, the horizontal axis represents the frequency of the microwaves irradiated onto the diamond 210 (i.e., the frequency of the VCO 140), and the vertical axis represents the fluorescence intensity measured by the photodetector 214. By keeping the microwave power constant and changing the microwave frequency, a dip in the intensity of red fluorescence emitted from the NV center of the diamond (i.e., red light intensity) could be observed. From this, the spin detection contrast ratio (i.e., the value obtained by dividing the size S of the dip in the graph shown in Figure 14 by the fluorescence intensity S0), which is the rate of decrease in red light intensity, can be calculated. Equation 1 below is known as the theoretical formula for the sensitivity δB of a diamond magneto-optical sensor (i.e., the resolution of the detection magnetic field B), and the spin detection contrast ratio affects the sensitivity δB.

[0089]

number

[0090] In Equation 1, γ is the gyromagnetic ratio (i.e., a constant), and the gyromagnetic ratio of electrons is (i.e., 1.76 × 10⁻⁶). 11 The value is close to rad / s / T). η is the fluorescence detection efficiency, and C is the spin detection contrast ratio. N is the number of negatively charged NV centers present in the area where excitation light is irradiated and fluorescence is focused. T2 is the transverse relaxation time of the electron spin. From the above theoretical sensitivity formula (Equation 1), the higher the spin detection contrast ratio, the smaller the sensitivity δB becomes, and the higher the sensitivity.

[0091] The measurement results in Figure 13 show that a fluorescence intensity of 1 μA and a spin detection contrast ratio of approximately 1.3% were obtained. Since the microwave source 220 includes circulators 146 and 164, the baseline fluctuation of fluorescence intensity shown in Figure 13 is suppressed to approximately ±0.1%.

[0092] As a comparative example, Figure 15 shows the results of measuring the fluorescence emitted from a diamond 210 after transmitting microwaves via a coaxial cable. In Figure 15, the horizontal axis represents the frequency of the microwaves irradiated onto the diamond 210, and the vertical axis represents the fluorescence intensity measured by the photodetector 214. By keeping the microwave power constant and changing the microwave frequency, a dip in the intensity of the red fluorescence emitted from the NV center of the diamond (i.e., red light luminance) could be observed, and a fluorescence intensity of 1 μA and a spin detection contrast ratio of approximately 2% were obtained. Since microwaves were transmitted via a coaxial cable, no circulator was included, and therefore, in the measurement results shown in Figure 15, the baseline fluctuation of the fluorescence intensity fluctuates by approximately ±1%.

[0093] Comparing the measurement results shown in Figures 13 and 15, it was possible to observe the same fluorescence intensity as when microwaves were transmitted via coaxial cable by transmitting microwaves using optical power supply, and to achieve a similar spin detection contrast ratio. This indicates that optical power supply of microwaves is effective in magnetic detection using a diamond NV center, and demonstrates the effectiveness of a diamond magneto-optical sensor configured accordingly. [Examples]

[0094] Similar to Example 1, a measurement apparatus with the configuration shown in Figure 11 was used, and a different microwave source 220 than in Example 1 was used to irradiate a diamond 210 having an NV center with microwaves and excitation light, and the fluorescence intensity emitted from the NV center was measured. Specifically, the microwave source 220 was configured as an external modulation type, using an LN element as shown in Figure 7 to input an external electrical modulation signal and form modulated light. The other parts were the same experimental configuration as in Example 1. With this configuration, modulated light could be generated using an LN element. The modulated light was converted to microwaves by a PD and bias tee after passing through an optical fiber and could be irradiated onto the diamond. By changing the microwave frequency, a spectrum similar to Figure 13 was obtained in which the fluorescence intensity decreased at the resonance frequency. The frequency position of the dip in the spectrum shifted depending on the strength of the magnetic field, confirming that the magnetic field could be detected. [Examples]

[0095] Similar to Example 1, a measurement apparatus with the configuration shown in Figure 11 was used, and the optical transmission component via optical fiber in the microwave supply source 220 was modified. Microwaves and excitation light were irradiated onto a diamond 210 having an NV center, and the fluorescence intensity emitted from the NV center was measured. Specifically, as shown in Figure 8, the modulated light and excitation light were combined and transmitted by injecting them into the same optical fiber. At the output side, the signals were again separated by a distributor, and microwaves were generated from the separated modulated light using a photoelectric converter, PD, and bias tee, and irradiated onto the diamond. By controlling the frequency of the modulated light and changing the frequency of the microwaves, a spectrum similar to that in Figure 13, in which the fluorescence intensity decreases at the resonance frequency, was obtained. The frequency position of the dip in the spectrum shifted depending on the strength of the magnetic field, confirming that the magnetic field could be detected. [Examples]

[0096] Similar to Example 1, a measurement apparatus with the configuration shown in Figure 11 was used, and the configuration of the microwave supply source 220 was changed. Microwaves and excitation light were irradiated onto a diamond 210 having an NV center, and the fluorescence intensity emitted from the NV center was measured. Specifically, a power amplifier was installed after the PD (corresponding to PD158 in Figure 3) in the photoelectric conversion unit (corresponding to photoelectric conversion unit 106 in Figure 3) to convert the modulated light into an electrical signal and amplify the power. Subsequently, the high-frequency component and the DC component were separated by a bias tee (corresponding to bias tee 160 in Figure 3). The high-frequency component was irradiated onto the diamond 210. The DC component separated by the bias tee was used for the power of the power amplifier. By changing the frequency of the microwave by changing the frequency of the modulated light, a spectrum similar to that in Figure 13, in which the fluorescence intensity decreases at the resonance frequency, could be obtained. The frequency position of the dip in the spectrum shifted depending on the strength of the magnetic field, confirming that the magnetic field could be detected. [Examples]

[0097] Similar to Example 1, a measurement apparatus with the configuration shown in Figure 11 was used. Instead of a dry cell battery (9V) for the voltage source 162, a solar cell with a rated voltage of 5V and output of 2W was used (see Figure 4). Microwaves and excitation light were irradiated onto a diamond 210 having an NV center, and the fluorescence intensity emitted from the NV center was measured. Light was irradiated onto the solar cell using a floodlight. By changing the frequency of the microwaves by changing the frequency of the modulated light, a spectrum similar to that in Figure 13, in which the fluorescence intensity decreases at the resonance frequency, was obtained. The frequency position of the dip in the spectrum shifted depending on the strength of the magnetic field, confirming that the magnetic field could be detected.

[0098] The present disclosure has been described above by describing embodiments, but the embodiments described above are illustrative and the present disclosure is not limited to the embodiments described above. The scope of the present disclosure is given by each claim, with reference to the description in the detailed description of the invention, and includes all modifications within the meaning and scope equivalent to the wording contained herein. [Explanation of symbols]

[0099] 100 Diamond Magneto-Optical Sensor System 102 cases 104,210 diamonds 106 Photoelectric conversion unit 108 Transmission section 110 Modulation signal generation unit 112 Optical Modulation Section 114, 126, 156, 182, 190, 208 optical fibers 116 Irradiation area 118 Optical power supply section 120 Excitation light generation unit 122, 192 splitter 124 Light-gathering section 128 Detection unit 130 Control Unit 140 VCO 142 Attenuator 144 Amplifier 146, 164 Circulator 148, 166 Terminator 150, 160 Bias Tea 152 Current source 154 LD 158 PD 162 Voltage source 168 Resonator 170 Impedance Converter 172 Resonator 180 LN element 194 Distributor 200 light source 202 Collimating Lens 204 Dichroic Mirror 206-sphere lens 212 LPF 214 Photodetectors 216 Diamond Magneto-Optical Sensor 220 Microwave Source 300 solar cells 302 Floodlight 304 Photodiode 306 Leaked excitation light A, B, C, D points α, β, γ angles

Claims

1. A diamond having a color center with electron spin, and being irradiated with excitation light, It includes an irradiation unit that irradiates the diamond with electromagnetic waves for magnetic resonance, The irradiation unit receives amplitude-modulated modulated light, The modulation frequency of the modulated light is included in the microwave frequency band. The irradiation unit further includes a photoelectric conversion unit that converts the modulated light into an electrical signal, The electromagnetic waves for magnetic resonance are formed by the electrical signals generated by the photoelectric conversion unit. The photoelectric conversion unit includes a photodiode that converts the modulated light into an electrical signal. The irradiation unit further includes a first bias tee that extracts the AC component from the electrical signal generated by the photodiode. The electromagnetic wave for magnetic resonance is formed by the AC component, The photoelectric conversion unit includes a photoelectric conversion element that converts a portion of the light, including at least one of the light from the light emitter, the modulated light, and the excitation light, into an electric potential. The first bias tee is a diamond magneto-optical sensor to which the potential generated by the photoelectric conversion element is applied, and the AC component is extracted from the electrical signal generated by the photodiode by adding the potential as the reverse bias voltage of the photodiode.

2. The photoelectric conversion unit further includes an amplifier that amplifies the output signal of the photodiode or the first bias tee. The diamond magneto-optical sensor according to claim 1, wherein the output signal is amplified by applying the power generated by the photoelectric conversion element to the amplifier.

3. The diamond magneto-optical sensor according to claim 1 or claim 2, wherein the carrier wave of the modulated light has a different wavelength from the wavelength of the excitation light.

4. The diamond magneto-optical sensor according to any one of claims 1 to 3, wherein the wavelength of the carrier wave of the modulated light is included in the near-infrared light wavelength band.

5. The excitation light has the same wavelength as the carrier wave of the modulated light, The diamond magneto-optical sensor according to claim 1 or claim 2, wherein the modulated light is generated by amplitude modulation of the excitation light.

6. The diamond magneto-optical sensor according to any one of claims 1 to 4, wherein the modulated light is laser light.

7. The diamond magneto-optical sensor according to any one of claims 1 to 6, wherein the modulated light is output from the laser diode by controlling the drive current of the laser diode to change at the modulation frequency.

8. The diamond magneto-optical sensor according to any one of claims 1 to 6, wherein the modulated light is output from the LN element, which receives laser light input, when the LN element is controlled by the modulation signal of the modulation frequency.

9. The diamond magneto-optical sensor according to claim 7, wherein the drive current of the laser diode is controlled by a second bias tee.

10. The diamond magneto-optical sensor according to any one of claims 1 to 9, wherein the excitation light is laser light.

11. The diamond magneto-optical sensor according to any one of claims 1 to 10, wherein the modulated light is transmitted via a first optical fiber and received by the irradiation unit.

12. The diamond magneto-optical sensor according to claim 11, wherein the excitation light is transmitted through a second optical fiber and irradiated onto the diamond.

13. The diamond magneto-optical sensor according to claim 11, wherein the excitation light is transmitted through the first optical fiber and irradiated onto the diamond.

14. The irradiation unit includes a resonator, The diamond is disposed in the resonator, as described in any one of claims 1 to 13.

15. The diamond magneto-optical sensor according to any one of claims 1 to 14, wherein the diamond is positioned within 5 mm of the photoelectric conversion unit.

16. The diamond magneto-optical sensor according to any one of claims 1 to 15, wherein the irradiation unit irradiates the diamond with the input modulated light as the electromagnetic wave for magnetic resonance.

17. It further includes a housing portion formed in a smooth shape by a conductive material, The diamond and the irradiation unit are housed in the housing unit, wherein the diamond is a magneto-optical sensor according to any one of claims 1 to 16.

18. A diamond magneto-optical sensor according to any one of claims 1 to 17, A light modulation unit that generates the modulated light, It includes a transmission unit that transmits the modulated light, A diamond magneto-optical sensor system in which the modulated light is transmitted via the transmission unit and received by the irradiation unit.

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