Diamond Magnetooptic Sensor

Abstract

A diamond magneto-optical sensor (100) according to the present invention includes: a diamond (102) having a color center that has an electron spin; a transmission circuit (106) that transmits electromagnetic waves; and an irradiation part that irradiates the diamond (102) with electromagnetic waves transmitted by the transmission circuit (106). The transmission circuit (106) includes an impedance converter (108) for decreasing or increasing, when viewed from the irradiation part, impedance of an electromagnetic wave source (110) that outputs electromagnetic waves. The irradiation part includes a resonator (104).

Description

【Technical Field】 【0001】 The present disclosure relates to a diamond-based optically pumped magnetometer. This application claims priority based on Japanese Application No. 2021-059796 filed on March 31, 2021, and incorporates by reference all the descriptions set forth in the Japanese application. 【Background Art】 【0002】 Optically pumped magnetometers using the nitrogen-vacancy (NV) centers in diamond are known. When the NV center, which consists of nitrogen occupying a substitutional position of carbon in diamond and a neighboring vacancy, is negatively charged, its ground state is a triplet state (i.e., spin 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 fluorescence intensity varies depending on the spin state, and the spin state changes due to magnetic resonance by a magnetic field and microwave or radio wave applied to the NV center, so it can be used as a diamond-based optically pumped magnetometer. 【0003】 A diamond-based optically pumped magnetometer includes a diamond substrate containing NV centers, an optical system that transmits excitation light from a light source and irradiates the NV centers, an optical system that condenses fluorescence from the NV centers and transmits it to a photodetector, and a waveguide that transmits microwaves from a power source and irradiates the NV centers. 【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】 Yuta Masuyama, Yuji Hatano, Takayuki Iwasaki, Mutsuko Hatano, "High-Sensitivity Macro Diamond Magnetometer Using a Coplanar Waveguide," Proceedings of the 79th Autumn Meeting of the Japan Society of Applied Physics (Publication Date: September 5, 2018) [Overview of the project] [Means for solving the problem] 【0006】 A diamond magneto-optical sensor according to one aspect of the present disclosure includes a diamond having a color center having electron spin, a transmission circuit for transmitting electromagnetic waves, and an irradiation unit for irradiating the diamond with the electromagnetic waves transmitted by the transmission circuit, wherein the transmission circuit includes an impedance converter for lowering or raising the impedance of an electromagnetic wave source that outputs electromagnetic waves as seen from the irradiation unit. 【0007】 A diamond magneto-optical sensor according to another aspect of the present disclosure includes a diamond having a color center having electron spin, a transmission circuit for transmitting electromagnetic waves, and an irradiation unit for irradiating the diamond with the electromagnetic waves transmitted by the transmission circuit, the irradiation unit including a resonator. [Brief explanation of the drawing] 【0008】 [Figure 1] Figure 1 is a circuit diagram showing a diamond magneto-optical sensor according to the first embodiment of this disclosure. [Figure 2] Figure 2 is a circuit diagram showing a diamond magneto-optical sensor according to a second embodiment of this disclosure. [Figure 3] Figure 3 is a three-view drawing (i.e., a top view, a side view, and a bottom view from top to bottom) showing a specific example of the diamond magneto-optical sensor shown in Figure 2. [Figure 4] Figure 4 is a two-view drawing (i.e., a top view and a front view from above) showing a coplanar waveguide with diamonds arranged within it. [Figure 5] Figure 5 is a cross-sectional view showing the magnetic field formed in the diamond by microwave irradiation in the diamond magneto-optical sensor shown in Figure 3. [Figure 6]Figure 6 is a circuit diagram showing a diamond magneto-optical sensor according to the third embodiment of this disclosure. [Figure 7] Figure 7 is a circuit diagram showing a diamond magneto-optical sensor according to the fourth embodiment of this disclosure. [Figure 8] Figure 8 is a three-view drawing (i.e., a top view, a side view, and a bottom view from top to bottom) showing a specific example of the diamond magneto-optical sensor shown in Figure 7. [Figure 9] Figure 9 is a cross-sectional view showing the magnetic field formed in the diamond by microwave irradiation in the diamond magneto-optical sensor shown in Figure 8. [Figure 10] Figure 10 is a three-view drawing (i.e., a top view, a side view, and a bottom view from top to bottom) showing a specific example of a diamond magneto-optical sensor according to the fifth embodiment of this disclosure. [Figure 11] Figure 11 is a cross-sectional view showing the magnetic field formed in the diamond by microwave irradiation in the diamond magneto-optical sensor shown in Figure 10. [Figure 12] Figure 12 is a three-view drawing (i.e., a top view, a side view, and a bottom view from top to bottom) showing a diamond magnetic sensor when microwave power is supplied by wireless transmission. [Figure 13] Figure 13 is a three-view drawing (i.e., a top view, a side view, and a bottom view from top to bottom) showing a diamond magneto-optical sensor according to the first modified example. [Figure 14] Figure 14 is a three-view drawing (i.e., a top view, a side view, and a bottom view from top to bottom) showing a diamond magneto-optical sensor according to the second modified example. [Figure 15] Figure 15 is a schematic diagram showing a multi-stage λ / 4 transformer. [Figure 16] Figure 16 is a schematic diagram showing a tapered λ / 4 transformer. [Figure 17] Figure 17 is a schematic diagram showing the configuration of the measuring device used in the experiment. [Figure 18] Figure 18 is a plan view showing the resonator of the microstrip line used in the experiment. [Figure 19] Figure 19 is a plan view showing the resonator of the coplanar waveguide used in the experiment. [Figure 20] FIG. 20 is a graph showing the change in the intensity of fluorescence emitted from the NV center of diamond. [Figure 21] FIG. 21 is a graph showing the experimental results. 【BEST MODE FOR CARRYING OUT THE INVENTION】 【0009】 [PROBLEMS TO BE SOLVED BY THE PRESENT DISCLOSURE] Following Non-Patent Document 1, when microwaves from a power source were transmitted using a coplanar waveguide and irradiated to the NV center for magnetic resonance, in order to achieve sufficient magnetic resonance, it was necessary to supply microwaves at a power of about 30 dBm (= 1 W). Also, when using a microstrip line, it was necessary to supply approximately the same level of microwave power. 【0010】 The frequency of the microwaves for magnetic resonance of the NV center is about 3 GHz, and this frequency changes under the influence of magnetic field, electric field, and temperature. The coefficients representing the degree of these influences (i.e., the change in resonance frequency) are shown below. Influence of magnetic field: 28 GHz / T Influence of electric field: 17 Hz / (V / cm) Influence of temperature: -74.2 kHz / K 【0011】 Therefore, if the power of the microwaves for magnetic resonance of the NV center is large, there is a problem that the temperature rises due to transmission loss of microwaves around the diamond including the NV center, the resonance frequency of magnetic resonance is affected, and the measurement is affected. Therefore, it is desirable to perform magnetic resonance with as small a microwave power as possible. 【0012】 Furthermore, when using a diamond magneto-optical sensor for measurements with high-voltage power equipment, it is desirable to ensure remote isolation when transmitting excitation light, fluorescence, and microwaves to avoid dielectric breakdown due to high voltage. Transmission of excitation light and fluorescence can be performed remotely with ensured isolation using optical fibers. While ensuring isolation is difficult with coaxial cable transmission of microwaves, it can be performed remotely with ensured isolation by using a transmitting antenna and a receiving antenna for spatial transmission via radio waves. When transmitting microwaves spatially using a transmitting antenna and a receiving antenna, it is preferable to achieve this with low power consumption, compactness, and low cost. That is, it is desirable to suppress the microwave transmission power, increase the antenna gain, and enable magnetic resonance with the lowest possible microwave power. 【0013】 Therefore, the present disclosure aims to provide a diamond magneto-optical sensor that can be operated by low-power microwaves. 【0014】 [Effects of this disclosure] According to this disclosure, a diamond magneto-optical sensor that can operate with low-power microwaves can be provided. 【0015】 [Description of Embodiments in this Disclosure] The embodiments of this disclosure are described below. At least some of the embodiments described below may be combined in any way. 【0016】 (1) A diamond magneto-optical sensor according to the first aspect of the present disclosure includes a diamond having a color center having electron spin, a transmission circuit for transmitting electromagnetic waves, and an irradiation unit for irradiating the diamond with the electromagnetic waves transmitted by the transmission circuit, wherein the transmission circuit includes an impedance converter for lowering or raising the impedance of an electromagnetic wave source that outputs electromagnetic waves as seen from the irradiation unit. This enables the diamond magneto-optical sensor to be operated by microwaves of low power. 【0017】 (2) The diamond magneto-optical sensor according to the second aspect of the present disclosure includes a diamond having a color center having an electron spin, a transmission circuit for transmitting electromagnetic waves, and an irradiation unit for irradiating the diamond with the electromagnetic waves transmitted by the transmission circuit, the irradiation unit including a resonator. This makes the diamond magneto-optical sensor operable with low-power microwaves. 【0018】 (3) In the diamond magneto-optical sensor relating to the second aspect, the transmission circuit may include an impedance converter to lower or raise the impedance of the electromagnetic wave source that outputs electromagnetic waves as seen from the irradiation part. This makes it possible to increase the current flowing through the resonator or the voltage applied to the resonator, and to efficiently irradiate the diamond with electromagnetic waves. 【0019】 (4) The impedance converter may include a transformer. This allows for easy formation of a diamond magneto-optical sensor. 【0020】 (5) The impedance converter may include a λ / 4 transformer. This allows for accurate impedance conversion between the electromagnetic wave transmission circuit and the resonator, enabling efficient irradiation of the diamond with electromagnetic waves. 【0021】 (6) The resonator may include a λ / 4 stub. This allows for precise adjustment of the resonator's resonant frequency and efficient irradiation of the diamond with electromagnetic waves. 【0022】 (7) The λ / 4 stub may include a λ / 4 open stub. This facilitates the design of diamond shapes with high fluorescence focusing efficiency. It also enables series resonance, increases the short-circuit current, and allows irradiation with microwaves with a stronger magnetic field. 【0023】 (8) The λ / 4 stub may include a λ / 4 short stub. This allows for parallel resonance, increases the open-circuit voltage, and enables irradiation with microwaves with a stronger magnetic field. 【0024】 (9) The λ / 4 stub may include two parallel linear conductors. This can increase the magnetic field applied to the diamond by microwaves. 【0025】 (10) The λ / 4 stub may include four linear conductors arranged in parallel. This can increase the magnetic field applied to the diamond by microwaves. 【0026】 (11) The λ / 4 stub may include two flat conductive plates, the two flat conductive plates may be arranged parallel to each other and facing each other. This increases the magnetic field applied to the diamond by microwaves and improves the uniformity of the magnetic field. 【0027】 (12) The thickness of the diamond may be greater than 0 and less than or equal to 0.3 mm, and the two linear conductors may be arranged with the diamond in between, spaced apart in the direction of the diamond's thickness. This allows the magnetic field applied to the diamond by microwaves to be increased. 【0028】 (13) The thickness of the diamond may be 0.5 mm or more and 3 mm or less, and the two flat conductive plates may be arranged with the diamond in between, spaced apart in the thickness direction of the diamond. This makes it possible to increase the magnetic field applied to the diamond by microwaves and improve the uniformity of the magnetic field. 【0029】 (14) The λ / 4 transformer may be formed in a tapered shape with a continuously changing width. This allows for easy and accurate broadband conversion of impedance. 【0030】 (15) The λ / 4 transformer may be formed as a multi-stage type with discretely varying widths. This allows for easy and accurate broadband conversion of impedance. 【0031】 (16) The impedance converter may include a microstrip line, the width of which may be less than or equal to half the length of the microstrip line. This allows for easy and accurate impedance conversion with minimal loss. 【0032】 (17) The width of the λ / 4 stub may be less than or equal to half the length of the λ / 4 stub. This allows resonance to occur with less radiation. 【0033】 (18) The center of the diamond may be located within a predetermined range from the connection end of the λ / 4 open stub to the transmission circuit, and the predetermined range may be between 1 / 8 and 3 / 8 of the electrical length of the λ / 4 open stub, and the length of the diamond along the longitudinal direction of the λ / 4 open stub may be 1 / 4 or less of the electrical length. This makes it possible to increase the magnetic field applied to the diamond by microwaves. 【0034】 (19) The center of the diamond may be located within a predetermined range from the short-circuit end of the λ / 4 short stub, and this predetermined range may be between 1 / 8 and 3 / 8 of the electrical length of the λ / 4 short stub, and the length of the diamond along the longitudinal direction of the λ / 4 short stub may be 1 / 4 or less of the electrical length. This makes it possible to increase the magnetic field applied to the diamond by microwaves. 【0035】 [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. 【0036】 (First Embodiment) Referring to Figure 1, the diamond magneto-optical sensor 100 according to the first embodiment of this disclosure includes a diamond 102, a resonator 104, a transmission circuit 106, and a microwave source 110. In this embodiment, microwaves are efficiently supplied to the diamond 102 by a resonator configured with a lumped-parameter circuit. The diamond 102 includes an NV center. 【0037】 The resonator 104 includes a coil L1 and a capacitor C1, forming a series resonant circuit. The diamond 102 is positioned near the coil L1 (including inside the coil L1). The inside of the coil L1 refers to the space surrounded by the windings that make up the coil L1. The resonator 104 is an irradiation section for irradiating the diamond 102 with microwaves. The transmission circuit 106 includes an impedance converter 108 and a coaxial cable with characteristic impedance Z1 connecting the impedance converter 108 and the microwave source 110. The microwave source 110 is a power supply that generates microwaves of a predetermined frequency. The characteristic impedance Z1 is, for example, 50Ω, and the microwave source 110 supplies electromagnetic waves (i.e., microwaves) to the diamond magneto-optical sensor 100 via the coaxial cable (i.e., 50Ω power supply). The impedance converter 108 is specifically a transformer. By using a transformer for the impedance converter 108, the diamond magneto-optical sensor can be easily formed. With this configuration, the resonator 104 and impedance converter 108 function as resonators, increasing the magnetic field of the microwaves from the microwave source 110 and irradiating the diamond 102. 【0038】 For example, when impedance conversion is performed using an impedance converter 108 with a winding turns ratio of primary:secondary = 1:N (where N is a positive rational number), the open-circuit voltage on the load side (i.e., an LC series resonator) is N times, and the impedance is N 2 The power doubles, and the short-circuit current flowing through the series resonant circuit becomes 1 / N times greater. Therefore, even if the power of the microwaves output from the microwave source 110 is lower than before, the diamond magneto-optical sensor 100 can function as a magnetic sensor if N is less than 1. 【0039】 (Second Embodiment) Referring to Figure 2, the diamond magneto-optical sensor 120 according to the second embodiment of this disclosure includes a diamond 102, a resonator 124, a transmission circuit 126, and a microwave source 110. In this embodiment, microwaves are efficiently supplied to the diamond 102 by a resonator configured with a high-frequency circuit. 【0040】 The resonator 124 includes a λ / 4 stub 122 and functions as a series resonant circuit. The diamond 102 is positioned near the λ / 4 stub 122. The resonator 124 is an irradiation section for irradiating the diamond 102 with microwaves. The transmission circuit 126 includes a λ / 4 transformer 128 and a coaxial cable with characteristic impedance Z1 connecting the λ / 4 transformer 128 and the microwave source 110. The characteristic impedance Z1 is, for example, 50Ω, and the microwave source 110 supplies microwaves to the diamond magneto-optical sensor 120 via the coaxial cable. The λ / 4 transformer 128 functions as an impedance converter. The λ / 4 stub 122 is, for example, a λ / 4 open stub. By using the λ / 4 transformer 128, the impedance can be accurately converted between the transmission circuit 126 (specifically, the coaxial cable with characteristic impedance Z1) and the resonator 124, and electromagnetic waves can be efficiently irradiated onto the diamond 102. 【0041】 With this configuration, the λ / 4 stub 122 and the λ / 4 transformer 128 function as resonators, increasing the magnetic field of the microwaves from the microwave source 110 and irradiating the diamond 102. Therefore, even if the power of the microwaves output from the microwave source 110 is lower than in conventional designs, the diamond magneto-optical sensor 120 can function as a magnetic sensor. 【0042】 Referring to Figure 3, the specific configurations of the λ / 4 stub 122 and the λ / 4 transformer 128 are shown. The λ / 4 stub 122 is composed of two copper wires 132 and 134. The two copper wires 132 and 134 form a λ / 4 open stub. Each of the copper wires 132 and 134 has a diameter d of 0.45 mm, and its length a1 is formed to 20 mm so that it is λ / 4 for microwaves of approximately 3 GHz (taking into account the surrounding dielectric). The spacing b1 between the copper wires 132 and 134 is 4 mm. The diamond 102 is placed between the copper wires 132 and 134. The diameter of each of the copper wires 132 and 134 may be between approximately 50 μm and 2 mm. If the diameter is too small than 50 μm, the copper wire will overheat and break when the microwave output is high. Furthermore, if the diameter is too large compared to 2 mm, the copper wire will protrude from the transmission circuit, resulting in poor electrical matching of the circuit. In this case (i.e., when using copper wire within the above diameter range), it is preferable that the diamond 102 has a thickness of 1 μm or more and 0.3 mm or less. 【0043】 The λ / 4 transformer 128 is composed of a dielectric substrate 140, a copper foil 130 placed on the surface of the dielectric substrate 140, and a copper foil 138 placed on the back surface of the dielectric substrate 140. The dielectric substrate 140 is formed of, for example, glass epoxy. The copper foil 130 is connected to a copper wire 132. The copper foil 130 is composed of a first part with a width w1 of 3 mm and a second part with a width w2 of 10 mm. The length a2 of the second part is 20 mm. The receptacle 136 is an SMA type receptacle to which a coaxial cable plug is attached. The center line (i.e., signal line) of the receptacle 136 is connected to the copper foil 130, and the ground of the receptacle 136 is connected to the copper foil 138. The copper foil 138 is connected to a copper wire 134. 【0044】 The impedance of the λ / 4 stub 122, which is a λ / 4 open stub, is, for example, 300Ω. To increase the magnetic field applied to the diamond 102 by microwaves at the junction of the λ / 4 transformer 128 and the λ / 4 stub 122, using a λ / 4 transformer 128 with an impedance of 25Ω, it is preferable to adjust the position of the diamond 102 placed on the λ / 4 stub 122. The distance e1 from the connection end of the λ / 4 stub 122 to the transmission circuit 126 (specifically the λ / 4 transformer 128) to the center of the diamond 102 is preferably 1 / 4 of the electrical length of the λ / 4 stub 122 (i.e., the λ / 4 open stub). However, the distance e1 can be in the range of (1 / 4) ± (1 / 8) of the electrical length of the λ / 4 stub 122 (i.e., in the range of 1 / 8 to 3 / 8). The thickness of the diamond 102 in the spacing b1 direction is preferably greater than 0 and 0.3 mm or less. The length of the λ / 4 stub 122 (i.e., λ / 4 open stub) of the diamond 102 along its longitudinal direction is preferably 1 / 4 or less of the electrical length of the λ / 4 stub 122. By making the diamond 102 of this size, the magnetic field applied to the diamond 102 by microwaves can be increased, as will be described later. 【0045】 We will now consider the intensity of the microwaves irradiated onto the diamond 102 under this configuration. Referring to Figure 4, when microwaves are irradiated onto the diamond 102 using a coplanar waveguide, at the moment when an upward current perpendicular to the plane of the paper flows through the conductor 902 on which the diamond 102 is placed, a downward current perpendicular to the plane of the paper flows through the conductors 900 and 904 on both sides (see the lower front view). Since it is a high-frequency current, due to the skin effect and proximity effect, the current concentrates at the ends of the conductors 900, 902, and 904. Therefore, the magnetic fields formed inside the diamond 102 are magnetic fields H1 and H2, indicated by solid arrows, formed by the upward current perpendicular to the plane of the paper, and magnetic fields H3 and H4, indicated by dashed arrows, formed by the downward current perpendicular to the plane of the paper. Since these magnetic fields almost cancel each other out, the combined magnetic field is small. On the other hand, referring to Figure 5, if the configuration is as shown in Figure 3, currents flow in opposite directions through the copper wires 132 and 134, and the magnetic field they form inside the diamond 102 increases because the magnetic field H1 indicated by the solid arrow and the magnetic field H2 indicated by the dashed arrow are pointing in the same direction. 【0046】 For example, compared to the coplanar waveguide shown in Figure 4 (for example, assuming an impedance of 50Ω), as described above, in the configuration shown in Figure 3, a short-circuit current flows due to series resonance, so the current is approximately doubled, and the impedance conversion from 50Ω to 12.5Ω also doubles the short-circuit current. Therefore, if the microwave power is the same, a total of approximately four times the current flows. For example, in a coplanar waveguide, the magnetic field H formed by a current of 1A is H = 14.5 (A / m). On the other hand, in the configuration shown in Figure 3, the magnetic field H formed by two copper wires 132 and 134 arranged in parallel with a spacing of 4mm is H = 70 (A / m) with a current of 1A, which is approximately five times that of the coplanar waveguide. Therefore, with the configuration shown in Figure 3, a total magnetic field 20 (= 4 × 5) times greater than that of the coplanar waveguide shown in Figure 4 can be applied to the diamond 102. Therefore, even if the power of the microwaves output from the microwave source 110 is lower than in conventional systems, the diamond magneto-optical sensor 120 can still function as a magnetic sensor. 【0047】 (Third embodiment) The above describes a case in which the microwaves irradiating the diamond 102 are increased by series resonance, but the invention is not limited to this. In the third embodiment, the microwaves irradiating the diamond 102 are increased by parallel resonance. Referring to Figure 6, the diamond magneto-optical sensor 142 according to the third embodiment of this disclosure includes a diamond 102, a resonator 144, a transmission circuit 146, and a microwave source 110. In this embodiment, microwaves are efficiently supplied to the diamond 102 by a resonator configured with lumped-parameter circuits. 【0048】 The resonator 144 includes a coil L2 and a capacitor C2, forming a parallel resonant circuit. The diamond 102 is placed near the coil L2 (including inside the coil L2). The resonator 144 is an irradiation section for irradiating the diamond 102 with microwaves. The transmission circuit 146 includes an impedance converter 148 and a coaxial cable with characteristic impedance Z1 connecting the impedance converter 148 and the microwave source 110. The characteristic impedance Z1 is, for example, 50Ω, and the microwave source 110 supplies microwaves to the diamond magneto-optical sensor 142 via the coaxial cable. The impedance converter 148 is specifically a transformer. By using a transformer for the impedance converter 148, the diamond magneto-optical sensor can be easily formed. With this configuration, the resonator 144 and the impedance converter 148 function as a resonator, amplifying the microwaves from the microwave source 110 and irradiating the diamond 102. 【0049】 For example, if the turns ratio of the windings of the impedance converter 148 is set to primary:secondary = 1:N when impedance conversion is performed, the open-circuit voltage on the load side (i.e., the LC parallel resonator) becomes N times greater. Therefore, even if the power of the microwaves output from the microwave source 110 is lower than in conventional systems, the diamond magneto-optical sensor 142 can function as a magnetic sensor. 【0050】 (Fourth Embodiment) Referring to Figure 7, the diamond magneto-optical sensor 150 according to the fourth embodiment of this disclosure includes a diamond 102, a resonator 154, a transmission circuit 156, and a microwave source 110. In this embodiment, microwaves are efficiently supplied to the diamond 102 by a resonator configured with a high-frequency circuit. 【0051】 The resonator 154 includes a λ / 4 stub 152 and functions as a parallel resonant circuit. The diamond 102 is positioned near the λ / 4 stub 152. The resonator 154 is an irradiation section for irradiating the diamond 102 with microwaves. The transmission circuit 156 includes a λ / 4 transformer 158 and a coaxial cable with characteristic impedance Z1 connecting the λ / 4 transformer 158 and the microwave source 110. The characteristic impedance Z1 is, for example, 50Ω, and the microwave source 110 supplies microwaves to the diamond magneto-optical sensor 150 via the coaxial cable. The λ / 4 transformer 158 functions as an impedance converter. The λ / 4 stub 152 is, for example, a λ / 4 short stub. By using the λ / 4 transformer 158, the impedance can be accurately converted between the transmission circuit 156 (specifically, the coaxial cable with characteristic impedance Z1) and the resonator 154, and electromagnetic waves can be efficiently irradiated onto the diamond 102. 【0052】 With this configuration, the λ / 4 stub 152 and the λ / 4 transformer 158 function as resonators, increasing the magnetic field of the microwaves from the microwave source 110 and irradiating the diamond 102. Therefore, even if the power of the microwaves output from the microwave source 110 is lower than in conventional designs, the diamond magneto-optical sensor 150 can function as a magnetic sensor. 【0053】 Referring to Figure 8, the specific configurations of the λ / 4 stub 152 and the λ / 4 transformer 158 are shown. The λ / 4 stub 152 is made of a flat copper foil 164. The copper foil 164 is formed by folding it into a rectangle with one side removed, so that its width w4 is 4 mm and its length a3 is 20 mm. That is, the copper foil 164 is configured so that two λ / 4 stubs are short-circuited at the folded portion of the copper foil 164 (hereinafter, the folded portion will be called the short-circuit end). The λ / 4 stub 152 is a λ / 4 short stub. The width w4 of the λ / 4 stub 152 is not limited to the above value. The width w4 of the λ / 4 stub 152 should be less than or equal to half the length a3 of the λ / 4 stub 152. This allows resonance with less radiation. 【0054】 The λ / 4 transformer 158 is connected to the copper foil 164 and consists of two parallel copper wires 160 and 162. The length a4 of the copper wires 160 and 162 is 20 mm, and the spacing b2 is 4 mm. The receptacle 136 is an SMA type receptacle to which the plug of the coaxial cable is attached. The center line (i.e., signal line) of the receptacle 136 is connected to the copper wire 160, and the ground of the receptacle 136 is connected to the copper wire 162. The diamond 102 is located within the space enclosed by the copper foil 164 (i.e., inside the copper foil 164). 【0055】 The impedance of the λ / 4 stub 152, which is a λ / 4 short stub, is, for example, 100Ω. To increase the magnetic field applied to the diamond 102 by microwaves at the junction of the λ / 4 transformer 158 and the λ / 4 stub 152 by converting the impedance with a λ / 4 transformer 158 having an impedance of 300Ω, it is preferable to adjust the position of the diamond 102 placed on the λ / 4 stub 152. The distance e2 from the short-circuit end of the λ / 4 stub 152 to the center of the diamond 102 is preferably 1 / 4 of the electrical length of the λ / 4 stub 152 (i.e., the λ / 4 short stub). However, the distance e2 may be in the range of (1 / 4) ± (1 / 8) of the electrical length of the λ / 4 stub 152 (i.e., in the range of 1 / 8 to 3 / 8). The thickness of the diamond 102 in the direction perpendicular to the λ / 4 stub 152 (i.e., the two parallel flat plate sections) is preferably 0.5 mm to 3 mm. The length of the λ / 4 stub 152 (i.e., λ / 4 short stub) of the diamond 102 along its longitudinal direction is preferably 1 / 4 or less of the electrical length of the λ / 4 stub 152. By making the diamond 102 of this size, the magnetic field applied to the diamond 102 by microwaves can be increased, as will be described later. 【0056】 We will now consider the intensity of the microwaves formed in the diamond 102 due to this configuration. As mentioned above, when microwaves are irradiated onto the diamond 102 using the coplanar waveguide shown in Figure 4, the magnetic fields formed inside the diamond 102 cancel each other out, so the combined magnetic field is small. On the other hand, referring to Figure 9, in the configuration shown in Figure 8, currents flow in opposite directions through the copper wires 160 and 162, and currents also flow in opposite directions through the parallel flat portions of the copper foil 164. Since it is a high-frequency current, the current concentrates at the ends of the copper foil 164 due to the skin effect and proximity effect. The magnetic field formed inside the diamond 102 by the current flowing through the copper foil 164 increases because the magnetic fields H1 and H3, indicated by solid arrows, and the magnetic fields H2 and H4, indicated by dashed arrows, are all pointing in the same direction (i.e., upwards in Figure 9). Furthermore, in Figure 9, the current distribution of the copper foil 164 is symmetrical in both the left-right and up-down directions. Therefore, the left-right component of the magnetic field in the central region inside the copper foil 164 is canceled out, resulting in higher uniformity of the magnetic field in the central region. 【0057】 (Fifth embodiment) In the above, the second embodiment described a case in which a dielectric substrate such as glass epoxy is used and a λ / 4 stub is constructed with two copper wires. In contrast, in the fifth embodiment, a flexible substrate is used and a λ / 4 stub is constructed with four copper wires. Referring to Figure 10, the diamond magneto-optical sensor 300 according to the fifth embodiment of this disclosure is composed of a diamond 102, a λ / 4 stub 302, a λ / 4 transformer 304, and a receptacle 136. 【0058】 The λ / 4 stub 302 is composed of four copper wires 310. The four copper wires 310 constitute a λ / 4 open stub. Each of the copper wires 310 has a diameter d of 0.45 mm and a length a8 of approximately 20 mm, which is λ / 4 for microwaves of approximately 3 GHz. The spacing g between the copper wires 310 is 2 mm. The diamond 102 is positioned in the center of the four copper wires 310. 【0059】 The λ / 4 stub 302 is composed of a flexible substrate 306, a copper foil 308 placed on the surface of the flexible substrate 306, and a copper foil 312 placed on the back surface of the flexible substrate 306. The width w8 of the copper foil 308 is 1 mm, and the length a9 is approximately 15 mm. The center line (i.e., signal line) of the receptacle 136 is connected to the copper foil 308, and the ground of the receptacle 136 is connected to the copper foil 312. The impedance of the λ / 4 stub 302, which is a λ / 4 open stub, is, for example, 200 Ω, and the impedance of the λ / 4 transformer 304 is, for example, 20 Ω. To increase the magnetic field applied to the diamond 102 by microwaves at the junction of the λ / 4 transformer 304 and the λ / 4 stub 302, it is preferable to adjust the position of the diamond 102 placed on the λ / 4 stub 302, similar to the second embodiment. 【0060】 We will now consider the intensity of microwaves formed on the diamond 102 in the diamond magneto-optical sensor 300 shown in Figure 10. Referring to Figure 11, in the configuration shown in Figure 10, of the four copper wires 310, the two upper wires (for example, the copper wires connected to the copper foil 308) have current flowing in the same direction, and the two lower wires (for example, the copper wires connected to the copper foil 312) have current flowing in the same direction. The current directions of the upper and lower wires are opposite. Magnetic fields H5 and H6 (see solid arrows) are formed on the diamond 102 by the two upper copper wires 310, and magnetic fields H7 and H8 (see dashed arrows) are formed by the two lower copper wires 310. Magnetic fields H5 and H8 are directed in the same direction, i.e., diagonally upward to the right in Figure 11, and mutually reinforce each other's magnetic fields. Magnetic fields H6 and H7 are directed in the same direction, i.e., diagonally downward to the right in Figure 11, and mutually reinforce each other's magnetic fields. 【0061】 The magnetic fields H5 to H8 create a combined magnetic field directed to the right. That is, a magnetic field can be applied in a direction parallel to the surface of the flexible substrate 306. On the other hand, as described above, with the configurations in Figures 3 and 8, a magnetic field can be formed perpendicular to the substrate (see Figures 5 and 9). Depending on the crystal orientation of the diamond 102, the direction of the NV centers, the orientation of the NV centers, the irradiation of the excitation light, and the layout of the fluorescence focusing, the direction of the microwave magnetic field relative to the substrate may be perpendicular or horizontal. When the perpendicular direction is preferred, for example, the configuration shown in Figure 3 or Figure 8 can be used. When the horizontal direction is preferred, for example, the configuration shown in Figure 10 can be used. 【0062】 In the first to fifth embodiments described above, microwave power may be supplied by wire or by wireless transmission in space. In the wired case, an example of connecting an SMA receptacle to the transmission circuit was shown above. On the other hand, in the wireless case, for example, as shown in Figure 12, the transmission circuit can be configured to receive microwaves with a monopole antenna and supply power to a resonator directly connected to the monopole antenna. Referring to Figure 12, the diamond magneto-optical sensor 330 is composed of a diamond 102, a λ / 4 stub 332, a λ / 4 transformer 334, and a monopole antenna 336. The λ / 4 stub 332 is composed of a linear conductor 342 (e.g., copper wire) and a part of a linear conductor 338 (e.g., copper wire) (i.e., the part corresponding to the linear conductor 342). The λ / 4 stub 332 is a λ / 4 open stub. The λ / 4 transformer 334 is composed of a flexible substrate 340, copper foil 344, and a portion of a linear conductor 338 (i.e., the portion facing the copper foil 344). The characteristic impedance of the monopole antenna 336 is, for example, 37Ω, and the characteristic impedances of the λ / 4 transformer 334 and the λ / 4 stub 332 are, for example, 20Ω and 200Ω, respectively. That is, the monopole antenna 336 receives microwaves, converts them to a low impedance, and causes them to resonate in series with the λ / 4 open stub. 【0063】 (First variation) In the above description, a case using a dielectric substrate (e.g., glass epoxy) was described as a second embodiment, but the invention is not limited thereto. The diamond magneto-optical sensor according to the first modified example uses a flexible substrate. 【0064】 Referring to Figure 13, the diamond magneto-optical sensor 170 according to the first modified example differs from the diamond magneto-optical sensor 120 shown in Figure 3 in the configuration of the λ / 4 stub 122 and the λ / 4 transformer 128. The λ / 4 stub 122 is composed of a flexible substrate 172, a copper foil 174 placed on the surface of the flexible substrate 172, and a copper foil 178 placed on the back surface of the flexible substrate 172. The flexible substrate 172 is formed of a film-like polyimide. Each of the copper foils 174 and 178 has a width w5 of 0.5 mm and a length a5 of 20 mm, and the distance b3 between them is 4 mm. The copper foils 174 and 178 are λ / 4 open stubs. The λ / 4 transformer 128 is composed of a flexible substrate 172, a copper foil 176 placed on the surface of the flexible substrate 172 and connected to the copper foil 174, and a copper foil 180 placed on the back surface of the flexible substrate 172 and connected to the copper foil 178. The width w6 of copper foil 176 is 1 mm, and the length a6 of copper foil 176 is 15 mm. The flexible substrate 172 constitutes both the λ / 4 stub 122 and the λ / 4 transformer 128, so its length (i.e., a5 + a6) is 35 mm. The center line (i.e., signal line) of receptacle 136, which is an SMA type receptacle to which the coaxial cable plug is attached, is connected to copper foil 176, and the ground of receptacle 136 is connected to copper foil 180. The diamond 102 is located in the space between copper foils 174 and 178 where the flexible substrate 172 is cut out. The characteristic impedance of receptacle 136 is 50 Ω. The characteristic impedances of λ / 4 transformer 128 and λ / 4 stub 122 are 20 Ω and 200 Ω, respectively. 【0065】 The diamond magneto-optical sensor 170 functions as a series resonant circuit, similar to the configuration shown in Figure 3, and can handle a significantly increased short-circuit current compared to conventional designs (see Figure 4). Furthermore, the diamond magneto-optical sensor 170 can increase the strength of the magnetic field formed inside the diamond 102, similar to the configuration shown in Figure 5, compared to conventional designs (see Figure 4). Therefore, even if the microwave power output from the microwave source 110 is lower than conventional designs, the diamond magneto-optical sensor 170 can function as a magnetic sensor. 【0066】 (Second variation) In the first modified example described above, a linear copper foil is used as the λ / 4 stub 122, but the invention is not limited to this. In the diamond magneto-optical sensor according to the second modified example, a planar copper foil is used as the λ / 4 stub 122. 【0067】 Referring to Figure 14, the diamond magneto-optical sensor 182 according to the second modified example differs from the diamond magneto-optical sensor 170 shown in Figure 13 in the configuration of the λ / 4 stub 122. The λ / 4 stub 122 is composed of copper foils 184 and 186. Each of the copper foils 184 and 186 has a width w7 of 4 mm and a length a7 of 20 mm, with a spacing b4 of 4 mm between them. The copper foils 184 and 186 are λ / 4 open stubs. The flexible substrate 188 is formed of film-like polyimide, similar to the diamond magneto-optical sensor 170, but its length a6 (a6 = 15 mm) is shorter than the length of the flexible substrate 172 of the diamond magneto-optical sensor 170 (i.e., a5 + a6). The diamond 102 is placed between the copper foils 184 and 186. The characteristic impedance of the receptacle 136 is 50 Ω. The characteristic impedances of the λ / 4 transformer 128 and the λ / 4 stub 122 are 20Ω and 200Ω, respectively. 【0068】 The diamond magneto-optical sensor 182 functions as a series resonant circuit, similar to the configuration shown in Figure 3, and can handle a significantly increased short-circuit current compared to conventional designs (see Figure 4). Furthermore, the diamond magneto-optical sensor 182 can increase the strength of the magnetic field formed inside the diamond 102, similar to the configuration shown in Figure 5, compared to conventional designs (see Figure 4). Therefore, even if the microwave power output from the microwave source 110 is lower than conventional designs, the diamond magneto-optical sensor 182 can function as a magnetic sensor. 【0069】 The above describes the case where the λ / 4 transformer 128 is formed from a λ / 4 stub (i.e., copper foil) of a predetermined width w2, but it is not limited to this. As shown in Figure 15, it may be a λ / 4 transformer in which the width w changes in steps, or as shown in Figure 16, it may be a λ / 4 transformer in which the width w changes smoothly in a tapered manner. As described above, a diamond magneto-optical sensor constructed using these for the λ / 4 transformer 128 shown in Figure 3 can function as a magnetic sensor even if the power of the microwaves output from the microwave source 110 is lower than in conventional designs. 【0070】 The above describes the case where the impedance converter is a transformer or a λ / 4 transformer, but it is not limited to these. A microstrip line may be used as the impedance converter. Preferably, the width of the microstrip line is 1 / 2 or less of the length of the microstrip line. By using a microstrip line as the impedance converter, the impedance can be easily and accurately converted between the microwave source and the microwave irradiation area. 【0071】 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. [Examples] 【0072】 The following examples illustrate the effectiveness of this disclosure. Using a measuring apparatus with the configuration shown in Figure 17, excitation light was shone onto a diamond having an NV center, and the fluorescence intensity emitted from the NV center was measured. Referring to Figure 17, the configuration of the measuring apparatus for shone excitation light onto the diamond 210 contained in the diamond magneto-optical sensor 216 (i.e., the 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 the 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. The configuration for shone microwaves onto the diamond 210 (i.e., the microwave system) includes a microwave source (not shown) and a coaxial cable 220, and the microwaves transmitted through the coaxial cable 220 are shared by the resonators constituting the diamond magneto-optical sensor 216. 【0073】 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 S06-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. 【0074】 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 then incident on the dichroic mirror 204. The fluorescence incident on the dichroic mirror 204 (i.e., red light) 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. 【0075】 As resonators for the diamond magneto-optical sensor 216, the resonators of the diamond magneto-optical sensor 120 shown in Figure 3, the resonators of the diamond magneto-optical sensor 150 shown in Figure 8, and the resonators of the diamond magneto-optical sensor 300 shown in Figure 10 were used. The configurations and dimensions of each are as described above. As comparative examples, a microstrip line resonator with the configuration and dimensions shown in Figure 18 and a coplanar waveguide resonator with the configuration and dimensions shown in Figure 19 were used. In Figure 18, a conductor that functions as ground is placed on the entire back surface of the dielectric substrate on which the microstrip line is arranged. For the diamonds, cubic diamonds, which will be described later, were placed at the positions shown in Figures 18 and 19. A plug for the coaxial cable 220 (not shown in Figure 17) was attached to the receptacle of each resonator (see Figures 3, 8, 10, 18, and 19) and microwaves were supplied. In the resonators shown in Figures 18 and 19, the receptacles not connected to the coaxial cable 220 were terminated with a 50Ω termination resistor. 【0076】 The same diamond was used for the measurements, and the configurations described in this disclosure and the comparative example were performed. Specifically, a type Ib diamond was used, 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 annealed at 800°C for about 1 hour to produce diamond 210, which was used for measurement. 【0077】 A microwave (1W) generated by a microwave generator (not shown) was transmitted to a diamond magneto-optical sensor 216 using a coaxial cable 220. A coaxial cable with a characteristic impedance of 50Ω was used for the coaxial cable 220. The power of the microwave supplied to the coaxial cable 220 was varied within the range of -16dBm to 30dBm. The microwave frequency was also varied within the range of 2.74GHz to 2.94GHz. When the microwave power is kept constant and the microwave frequency is varied, a dip in the intensity of red fluorescence (i.e., red light intensity) emitted from the diamond NV center can be observed, as shown in Figure 20. From this, the spin detection contrast ratio (i.e., the value obtained by dividing the size of the dip S in the graph 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 (i.e., the resolution of the detected magnetic field B) of a diamond magneto-optical sensor, and the spin detection contrast ratio affects the sensitivity δB. 【0078】 【number】 【0079】 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 This value is close to rad / s / T. η is the fluorescence detection efficiency, and C is the spin detection contrast. 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, the smaller the sensitivity δB becomes, and the higher the sensitivity. 【0080】 For the five types of resonators described above (see Figures 3, 8, 10, 18, and 19), the microwave power was varied as described above, and the valleys in fluorescence intensity (i.e., red light luminance) were observed, and the spin detection contrast ratio was calculated. The results are shown in Figure 21. In Figure 21, white circles represent the results using the λ / 4 open stub resonator shown in Figure 3. Black circles represent the results using the λ / 4 short stub resonator shown in Figure 8. White triangles represent the results using the λ / 4 open stub resonator shown in Figure 10. White squares represent the results using the microstrip line resonator shown in Figure 18. Black squares represent the results using the coplanar waveguide resonator shown in Figure 19. 【0081】 As can be seen from Figure 21, by using a λ / 4 open stub resonator (see Figure 3), an equivalent spin detection contrast ratio was obtained using microwaves with approximately 25 dB (i.e., 1 / 300 in power) less power than the comparative examples (see Figures 18 and 19). By using a λ / 4 short stub resonator (see Figure 8), an equivalent spin detection contrast ratio was obtained using microwaves with approximately 10 dB (i.e., 1 / 10 in power) less power than the comparative examples. Furthermore, by using a λ / 4 open stub resonator with four copper wires arranged in parallel (see Figure 10), an equivalent spin detection contrast ratio was obtained using microwaves with an even lower power of 2 dBm compared to the λ / 4 open stub resonator with two copper wires arranged in parallel (see Figure 3). Thus, by using the resonators of this disclosure, a diamond magneto-optical sensor can be made to function even with microwaves of significantly lower power than conventional methods. [Examples] 【0082】 Using the configuration of the second embodiment (see Figure 3), the diameters of the copper wires 132 and 134 constituting the λ / 4 stub, and the size of the diamonds were changed, and the experiment was conducted in the same manner as in Example 1 (see Figure 17). Specifically, copper wires with diameters of 0.1 mm, 0.3 mm, 1.0 mm, and 1.5 mm were used as copper wires 132 and 134. As a comparative example, copper wires with diameters of 0.02 mm and 3 mm were used as copper wires 132 and 134. Diamonds 210 (see Figure 17) with thicknesses of 0.8 μm, 10 μm, 0.1 mm, 0.3 mm, and 0.5 mm were used. 【0083】 As a result, when copper wires with diameters of 0.1 mm, 0.3 mm, 1.0 mm, and 1.5 mm were used, the results were the same as in Example 1. That is, the same spin detection contrast ratio as shown by the white circle in Figure 21 (i.e., when the diameters of copper wires 132 and 134 were 0.45 mm) was obtained. On the other hand, when copper wires with a diameter of 0.02 mm were used for copper wires 132 and 134, the temperature of the copper wires rose and the resistance value increased. When the microwave output was high, the copper wires broke if the temperature rise was left unchecked. Also, when copper wires with a diameter of 3 mm were used for copper wires 132 and 134, they were too thick, and resonance matching could not be achieved, causing the spin detection contrast ratio to drop to 0.001 or less. 【0084】 Regarding the diamond 210 (see Figure 17), for samples with thicknesses of 10 μm and 0.1 mm, the same results as in Example 1 were obtained, i.e., the same spin detection contrast ratio as shown by the white circles in Figure 21. On the other hand, for the diamond 210 sample with a thickness of 0.8 μm, the fluorescence intensity was low, making light detection difficult. For the diamond 210 sample with a thickness of 0.5 mm, the spin detection contrast ratio decreased to less than 1 / 10 compared to the 0.3 mm sample. 【0085】 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] 【0086】 100, 120, 142, 150, 170, 182, 216, 300, 330 Diamond Magneto-Optical Sensor 102,210 diamonds 104, 124, 144, 154 resonators 106, 126, 146, 156 transmission circuits 108, 148 Impedance Converter 110 Microwave Source 122, 152, 302, 332 λ / 4 stub 128, 158, 304, 334 λ / 4 transformers 130, 138, 164, 174, 176, 178, 180, 184, 186, 308, 312, 344 Copper foil 132, 134, 160, 162, 310 copper wire 136 Receptacles 140 Dielectric substrate 172, 188, 306, 340 Flexible circuit boards 200 light source 202 Collimating Lens 204 Dichroic Mirror 206-sphere lens 208 Fiber Optics 212 LPF 214 Photodetectors 220 Coaxial Cable 336 Monopole Antenna 338, 342 Linear conductors 900, 902, 904 Conductors a1, a2, a3, a4, a5, a6, a7, a8, a9 length b1, b2, b3, b4, g spacing C1, C2 Capacitors d, d1 diameter e1, e2 distance H1, H2, H3, H4, H5, H6, H7, H8 magnetic field L1, L2 coils w1, w2, w4, w5, w6, w7, w8 width Z1 Impedance

Claims

[Claim 1] Diamonds having color centers with electron spin, A transmission circuit that transmits electromagnetic waves, The system includes an irradiation unit that irradiates the diamond with the electromagnetic waves transmitted by the transmission circuit, The irradiation unit includes a resonator, The resonator includes a λ / 4 stub, The λ / 4 stub includes a λ / 4 open stub. The center of the diamond is located within a predetermined range from the connection end of the λ / 4 open stub to the transmission circuit. The predetermined range is 1 / 8 or more and 3 / 8 or less of the electrical length of the λ / 4 open stub. A diamond magneto-optical sensor, wherein the length of the diamond along the longitudinal direction of the λ / 4 open stub is 1 / 4 or less of the electrical length. [Claim 2] Diamonds having color centers with electron spin, A transmission circuit that transmits electromagnetic waves, The system includes an irradiation unit that irradiates the diamond with the electromagnetic waves transmitted by the transmission circuit, The irradiation unit includes a resonator, The resonator includes a λ / 4 stub, The λ / 4 stub includes a λ / 4 short stub. The center of the diamond is located within a predetermined range from the short-circuit end of the λ / 4 short stub. The predetermined range is 1 / 8 or more and 3 / 8 or less of the electrical length of the λ / 4 short stub. A diamond magneto-optical sensor, wherein the length of the diamond along the longitudinal direction of the λ / 4 short stub is 1 / 4 or less of the electrical length. [Claim 3] The diamond magneto-optical sensor according to claim 1 or claim 2, wherein the transmission circuit includes an impedance converter for lowering or raising the impedance of the electromagnetic wave source that outputs the electromagnetic wave, as viewed from the irradiation unit. [Claim 4] The diamond magneto-optical sensor according to claim 3, wherein the impedance converter includes a transformer. [Claim 5] The diamond magneto-optical sensor according to claim 3, wherein the impedance converter includes a λ / 4 transformer. [Claim 6] The diamond magneto-optical sensor according to any one of claims 1 to 5, wherein the λ / 4 stub includes two linear conductors arranged in parallel. [Claim 7] The diamond magneto-optical sensor according to any one of claims 1 to 5, wherein the λ / 4 stub includes four linear conductors arranged in parallel. [Claim 8] The λ / 4 stub includes two flat conductive plates, The diamond magneto-optical sensor according to any one of claims 1 to 5, wherein the two flat conductive plates are arranged parallel to each other and facing each other. [Claim 9] The thickness of the aforementioned diamond is greater than 0 and less than or equal to 0.3 mm. The diamond magneto-optical sensor according to claim 6, wherein the two linear conductors are arranged to sandwich the diamond and spaced apart in the thickness direction of the diamond. [Claim 10] The thickness of the diamond is 0.5 mm or more and 3 mm or less. The diamond magneto-optical sensor according to claim 8, wherein the two flat conductive plates are arranged to sandwich the diamond and are spaced apart in the thickness direction of the diamond. [Claim 11] The diamond magneto-optical sensor according to claim 5, wherein the λ / 4 transformer is formed in a tapered shape with a continuously changing width. [Claim 12] The diamond magneto-optical sensor according to claim 5, wherein the λ / 4 transformer is formed in a multi-stage type with a discretely changing width. [Claim 13] The impedance converter includes a microstrip line, The diamond magneto-optical sensor according to claim 5, wherein the width of the microstrip line is 1 / 2 or less of the length of the microstrip line. [Claim 14] The diamond magneto-optical sensor according to any one of claims 1 to 5, wherein the width of the λ / 4 stub is 1 / 2 or less of the length of the λ / 4 stub.

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