JP2022098572A - Sensor - Google Patents

Abstract

To provide a sensor capable of generating a uniform magnetic field in a wide frequency band to an element having a color center such as an NV center, and capable of coping with miniaturization of the sensor.SOLUTION: A sensor includes a diamond element 2 having an NV center, a pair of antennas 10 provided with the diamond element 2 sandwiched therebetween, and a feeder for supplying a frequency-variable high frequency current to the pair of antennas 10. A plurality of loop conductors provided in the radiation element 12 of the antenna 10 have mutually different lengths in the circumferential direction, and are arranged so as to be spaced apart on the outer peripheral side in a multiplexed manner as the length in the circumferential direction increases, and have mutually different resonance frequencies. The feeder supplies the high frequency current to the radiation element 12 of a pair of antennas 10 so that a magnetic flux induced by the radiation element 12 of one antenna 10 and a magnetic flux induced by the radiation element 12 of the other antenna 10 pass through the diamond element 2 in the same direction.SELECTED DRAWING: Figure 7

Description

The present invention relates to a sensor.

A sensor that measures a magnetic field by the principle of Optically Detected Magnetic Resonance (ODMR) using a diamond element having an NV center is known (see, for example, Patent Document 1). In this sensor, green light as excitation light is irradiated to the NV center, and microwaves are irradiated to the NV center while sweeping the frequency, and red fluorescence emitted from the NV center is detected. In this sensor, when a microwave having a resonance frequency is applied to the NV center, electron spin resonance occurs in the NV center and the brightness of the red fluorescence emitted from the NV center decreases. Here, the magnetic field causes Zeeman splitting in the NV center, which causes at least two red fluorescence luminance drop points during microwave frequency sweep. Since Zeeman splitting in the NV center occurs in a magnitude proportional to the magnetic field strength, the difference in microwave frequency (hereinafter referred to as frequency split) corresponding to the brightness reduction points of the two red fluorescence points is proportional to the magnetic field strength. And get bigger. Thereby, the magnetic field strength can be detected based on the magnitude of the split of the frequency of the microwave.

International Publication No. 2015/107907

By the way, a battery sensor for measuring the remaining battery level of an electric vehicle (xEV) is required to expand the measurement range with the expansion of the output current range of the electric vehicle. When the above-mentioned sensor is used for this battery sensor, the range of fluctuation of the microwave frequency split is expanded. Therefore, an antenna capable of operating the sensor in a wide frequency band is required.

Further, when the above-mentioned sensor is used as the battery sensor, it is necessary to generate a uniform magnetic field in a wide frequency band with respect to the NV center, but when the coplanar line is used as an antenna, the frequency is changed. It has been confirmed that the distribution of the magnetic field strength changes and the strength of the magnetic field changes at the position of the NV center (see FIG. 16). Further, there is a demand for miniaturization of the battery sensor, and the coplanar line has a size more than 100 times that of the diamond element.

In view of the above circumstances, the present invention provides a sensor that can generate a uniform magnetic field in a wide frequency band for an element having a color center such as an NV center, and can also cope with miniaturization of the sensor. The purpose is to do.

The sensor of the present invention supplies a variable-frequency high-frequency current to an element having a color center to be excited, a pair of color center-exciting antennas provided across the element, and a pair of the color-center-exciting antennas. The color center excitation antenna is provided with a feeder, and is formed on a substrate facing the element and a surface of the substrate facing the element, and the high-frequency current is supplied by the feeder. The radiating element includes a radiating element that radiates a microwave, and the radiating element includes a plurality of loop conductors. The plurality of loop conductors have different circumferential lengths from each other. They are multiplely spaced apart from each other so as to be located at, and have different resonance frequencies from each other. The high-frequency current is supplied to the radiation element of the pair of color center excitation antennas so that the magnetic flux formed by the radiation element of the color center excitation antenna passes through the element in the same direction.

Further, in the sensor of the present invention, a high frequency current having a variable frequency is applied to an element having a color center to be excited, a pair of color center excitation antennas provided across the element, and a pair of the color center excitation antennas. The color center excitation antenna is formed on the surface of the element, and includes a radiating element to which the high-frequency current is supplied by the feeding device to radiate microwaves. A plurality of loop conductors are provided, and the plurality of loop conductors have different circumferential lengths from each other, and are arranged at intervals from each other so as to be located on the outer peripheral side as the circumferential length increases. The resonance frequencies are different from each other, and the feeder has a magnetic current formed by the radiating element of one of the color center exciting antennas and a current flux formed by the radiating element of the other color center exciting antenna. The high-frequency current is supplied to the radiating element of the pair of the color center excitation antennas so that the antennas pass through the element in the same direction.

According to the present invention, a uniform magnetic field can be generated in a wide frequency band for an element having a color center such as an NV center, and the sensor can be miniaturized.

FIG. 1 is a diagram showing an outline of a sensor according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing the structure of a diamond element having an NV center. FIG. 3 is a diagram for explaining the principle of a diamond quantum sensor including a diamond element having an NV center and measuring magnetic field strength and the like by the principle of optical detected magnetic resonance. FIG. 4 is a graph showing the relationship between the brightness reduction point of red fluorescence during microwave frequency sweep, the microwave frequency, and the magnetic field strength. FIG. 5 is a perspective view showing the antenna shown in FIG. 1 from the front surface side. FIG. 6 is a plan view showing the antenna shown in FIG. 1 from the front surface side. FIG. 7 is a perspective view showing the pair of antennas and the diamond element shown in FIG. FIG. 8 is a perspective view showing the pair of antennas and the diamond element shown in FIG. 7 with the substrate not shown. FIG. 9 is a cross-sectional view showing a magnetic field formed by the pair of antennas shown in FIGS. 7 and 8. FIG. 10 is a cross-sectional view showing a magnetic field formed by the pair of antennas shown in FIGS. 7 and 8. FIG. 11 is a graph showing a simulation result of the magnetic field strength of the pair of antennas of the embodiment. FIG. 12 is a diagram showing a simulation result of the magnetic field strength directly above the antenna having three loop conductors. FIG. 13 is a diagram showing a simulation result of the magnetic field strength directly above the antenna having four loop conductors. FIG. 14 is a diagram showing a simulation result of the magnetic field strength directly above the antenna having five loop conductors. FIG. 15 is a graph showing the simulation results of the magnetic field strength of the antenna of the comparative example. FIG. 16 is a diagram showing the distribution of the magnetic field strength of the antenna of the second comparative example.

Hereinafter, the present invention will be described with reference to preferred embodiments. The present invention is not limited to the embodiments shown below, and can be appropriately modified without departing from the spirit of the present invention. Further, in the embodiments shown below, some parts of the configuration are not shown or explained, but the details of the omitted techniques are within the range where there is no contradiction with the contents described below. , Known or well-known techniques are applied as appropriate.

FIG. 1 is a diagram showing an outline of a sensor 1 according to an embodiment of the present invention. As shown in this figure, the sensor 1 is generated by the diamond element 2 having an NV center, the optical system 3 that irradiates the diamond element 2 with green light GL as excitation light, and the electron spin resonance of the NV center. A pair of an optical sensor 4 that detects an optical signal, a control / arithmetic processing unit 5 that processes an optical signal detected by the optical sensor 4 and controls the entire sensor 1, and a pair of diamond elements 2 that irradiate a variable frequency microwave. The antenna 10 is provided with a power amplifier 6 for supplying a high-frequency current to the pair of antennas 10. The sensor 1 irradiates the NV center with green light GL and irradiates the NV center with microwaves while sweeping the frequency, and measures the magnetic field strength, electric field strength, temperature, etc. of the measurement target by the principle of optical detected magnetic resonance.

The diamond element 2 is formed, for example, in the shape of a square plate having a length of 2 to 5 mm and a width of 2 to 5 mm. That is, the diamond element 2 is a small plate-shaped element having a vertical and horizontal dimension of less than 10 mm.

On the other hand, the antenna 10 is, for example, a planar antenna having a square microwave radiation region of 2 to 5 mm in length × 2 to 5 mm in width. That is, the antenna 10 is a planar antenna having a small-sized microwave radiation region having a vertical and horizontal dimension of less than 10 mm. Although the details will be described later, the pair of antennas 10 sandwich the diamond element 2. Then, the surface of each antenna 10 that emits microwaves and one surface of the diamond element 2 face each other without leaving a gap.

FIG. 2 is a diagram schematically showing the structure of the diamond element 2 having an NV center. As shown in this figure, the NV center is a complex impurity consisting of a pair of nitrogen (Nitrogen) that has entered the carbon substitution position in the diamond lattice and vacancy (Vacancy) in which the carbon atom adjacent to this nitrogen has escaped. It is a defect. When this NV center captures one electron from the neutral charge state _NV0 and becomes NV ⁻ , it forms an electron spin triplet state with magnetic quantum numbers ms = -1, 0, +1. The diamond quantum sensor uses this electron spin triplet state to measure a magnetic field, an electric field, temperature, distortion, and the like.

FIG. 3 is a diagram for explaining the principle of a diamond quantum sensor including a diamond element 2 having an NV center and measuring magnetic field strength and the like by the principle of optical detected magnetic resonance. As shown in FIGS. 2 and 3, the NV center emits red fluorescent RL when irradiated with green light GL as excitation light. The brightness of this red fluorescent RL is large when the NV center is excited from the ground state (the state where the magnetic quantum number _ms = 0 of the electron spin), whereas the NV center is the level at which electron spin resonance occurs. It becomes smaller when excited from (state of magnetic quantum number _ms = ± 1 of electron spin).

Here, when the NV center is irradiated with a microwave MW having a resonance frequency (about 2.8 GHz) when the magnetic field strength is 0, the NV center causes an electron spin resonance (ESR) level (m _S =). Transition to ± 1). Some of the electrons photoexcited from this level do not contribute to light emission by returning to the ground state through a non-radiative transition. Therefore, as described above, when the NV center is excited from the level at which electron spin resonance occurs, the brightness of the red fluorescent RL decreases.

FIG. 4 is a graph showing the relationship between the luminance drop point of the red fluorescent RL at the time of frequency sweeping of the microwave MW, the frequency of the microwave MW, and the magnetic field intensity B. As shown in this graph, when the magnetic field strength B is 0, the luminance drop point of the red fluorescent RL is only one point, whereas the magnetic field strength B is a value B ₁ , B ₂ , B ₃ larger than 0. When (B ₃ > B ₂ > B ₁ > 0), the red fluorescent RL
There are two points of decrease in brightness. Here, the split Δf (= f ₂ -f ₁ ) of the frequency of the microwave MW corresponding to the brightness reduction points of the two red fluorescent RLs increases in proportion to the magnetic field strength B.

By the way, the sensor 1 of the present embodiment is used as a battery sensor for measuring the remaining battery level of the electric vehicle. Here, the range of the output current of the electric vehicle is wide, for example, from 10 mA to a value exceeding 1000 A. Along with this, the antenna 10 of the sensor 1 of the present embodiment is required to have the ability to sweep the microwave MW in a wide frequency band such as 1 to 5 GHz, and to have stable high output in this wide frequency band. Will be done. Further, it is required to reduce the size of the antenna 10 according to the size of the diamond element 2. That is, the antenna 10 is required to satisfy the above performance due to the constraint of miniaturization. Further, the antenna 10 is required to generate a uniform magnetic field in a wide frequency band with respect to the diamond element 2.

Hereinafter, the pair of antennas 10 will be described. 5 is a perspective view showing the antenna 10 shown in FIG. 1 from the front surface side, and FIG. 6 is a plan view showing the antenna 10 shown in FIG. 1 from the front surface side. As shown in these figures, the antenna 10 includes a substrate 11, a radiating element 12, a plurality of capacitors 13A and 13B, and feeder lines 14A and 14B. The pair of antennas 10 have the same configuration.

The substrate 11 is a rectangular plate material, and is formed of, for example, a material used in a printed circuit board or the like. A square microwave radiation region is set on the surface of the substrate 11, and the microwave radiation region faces one of the square surfaces of the diamond element 2. In the present embodiment, the microwave radiation region is arranged at a position closer to one side (upper side in FIG. 6) of the four sides of the substrate 11.

The radiating element 12 includes a plurality of loop-shaped conductors (hereinafter referred to as loop conductors) 12A and 12B. The plurality of loop conductors 12A and 12B are formed in the microwave radiation region of the substrate 11. The loop conductors 12A and 12B are conductive foils such as copper foil, and are formed in a rectangular loop shape (annular shape). Examples of the method for forming the loop conductors 12A and 12B include copper foil etching and the like.

The loop conductors 12A and 12B have different lengths in the circumferential direction. As will be described later, the loop conductors 12A and 12B are provided with gaps G1 to G3, and the length of the loop conductors 12A and 12B including the gaps G1 to G3 in the circumferential direction is set to the loop conductor 12A. , 12B circumference.

The peripheral lengths of the loop conductors 12A and 12B increase in the order of 12A and 12B. The loop conductor 12B having the maximum peripheral length (first) is formed at the outermost peripheral portion of the microwave radiation region. The loop conductor 12A having the minimum peripheral length (second) is formed on the inner peripheral side of the loop conductor 12B with a space between the loop conductor 12B and the loop conductor 12B.

The centers of the loop conductors 12A and 12B are aligned. When three or more loop conductors are provided, the three or more loop conductors are arranged at equal intervals from the central portion to the outermost peripheral portion of the microwave radiation region.

One gap G1 is formed in the loop conductor 12A, and two gaps G2 and G3 are formed in the loop conductor 12B. The three gaps G1 to G3 are arranged so as to be aligned on the same straight line. The straight line passing through the three gaps G1 to G3 passes through the center of the loop conductors 12A and 12B and is orthogonal to the opposite sides of the loop conductors 12A and 12B arranged in parallel in the vertical direction in FIG. Here, where each of the loop conductors 12A and 12B has opposite sides arranged in parallel vertically in FIG. 6, the gap G1 is formed on the upper side of the loop conductor 12A in FIG. 6, and the gap G2 is formed. The loop conductor 12B is formed on the upper side in FIG. 6, and the gap G3 is formed on the lower side of the loop conductor 12B in FIG.

The plurality of capacitors 13A and 13B are mounted on the back surface of the substrate 11. The plurality of capacitors 13A and 13B are arranged side by side in a row at the center of FIG. 6 in the left-right direction on the back surface of the substrate 11.

The capacitor 13A is arranged at a position overlapping the gap G1 of the loop conductor 12A, and is electrically connected to the loop conductor 12A through a through hole. The capacitor 13A has a function of adjusting the resonance frequency of the loop conductor 12A. The resonance frequency of the loop conductor 12A is adjusted to the first frequency (for example, about 5 GHz).

The capacitor 13B is arranged at a position overlapping the gap G2 of the loop conductor 12B, and is electrically connected to the loop conductor 12B through a through hole. The capacitor 13B has a function of adjusting the resonance frequency of the loop conductor 12B. The resonance frequency of the loop conductor 12B is adjusted to a second frequency (for example, about 1 GHz) lower than the first frequency.

The feeder lines 14A and 14B are waveguides formed on the surface of the substrate 11. The feeder lines 14A and 14B are conductive foils such as copper foils, and are formed in a straight line. Examples of the method for forming the feeder lines 14A and 14B include copper foil etching and the like.

The feeder lines 14A and 14B are formed parallel to each other on the surface of the substrate 11. One end of the feeder lines 14A and 14B is arranged so as to overlap one of the four sides of the substrate 11 (the lower side in FIG. 6), and the power amplifier 6 (see FIG. 1) is connected to the feeder line 14A and 14B. On the other hand, the other ends of the feeder lines 14A and 14B are arranged so as to sandwich the gap G3 of the loop conductor 12B, and are connected to one end or the other end of the loop conductor 12B.

FIG. 7 is a perspective view showing the pair of antennas 10 and the diamond element 2 shown in FIG. FIG. 8 is a perspective view showing the pair of antennas 10 and the diamond element 2 shown in FIG. 7 with the substrate 11 not shown. As shown in these figures, the pair of antennas 10 are arranged so as to sandwich the diamond element 2 in the microwave radiation region. Specifically, the square region surrounded by the loop conductor 12B on the outer peripheral side and one square surface of the diamond element 2 have the same length of the vertical side and the length of the horizontal side, and the center position is also the same. Match. Further, in the pair of antennas 10, the feeder lines 14A and 14B are arranged symmetrically with respect to the center of the radiating element 12. It is sufficient that the square region surrounded by the loop conductor 12B on the outer peripheral side and the NV center of the diamond element 2 face each other, and the dimensional relationship between the loop conductor 12B on the outer peripheral side and the diamond element 2 is limited to the above. It is not something that will be done. For example, the vertical and horizontal lengths of one square surface of the diamond element 2 are larger than the vertical and horizontal lengths of the square region surrounded by the loop conductor 12B on the outer peripheral side, or are surrounded by the loop conductor 12B on the outer peripheral side. The vertical and horizontal lengths of the square region may be larger than the vertical and horizontal lengths of one of the square surfaces of the diamond element 2.

The pair of antennas 10 having the above configuration are supplied with a frequency-variable high-frequency current from the power amplifier 6 (see FIG. 1) through the feeder lines 14A and 14B, and radiate the frequency-variable microwave MW from the loop conductors 12A and 12B. do. The frequency of the high frequency current supplied to the pair of antennas 10 is swept. Resonance occurs in any of the loop conductors 12A and 12B according to the frequency of the high frequency current at the time of frequency sweep, and the magnetic field amplified by the resonance is generated from the loop conductors 12A and 12B.

Here, the high-frequency current output from the power amplifier 6 is distributed by a distributor (not shown) and supplied to the pair of antennas 10. As a result, a high frequency current whose frequency and phase are synchronized is supplied to the pair of antennas 10. Further, the high frequency current is supplied to the pair of antennas 10 so as to flow in the same direction (clockwise direction indicated by the arrow A in the figure) in the loop conductor 12B of the pair of antennas 10.

9 and 10 are cross-sectional views showing a magnetic field formed by the pair of antennas 10 shown in FIGS. 7 and 8. FIG. 9 shows a simulation result of a magnetic field formed by the pair of antennas 10 when a high frequency current having a frequency of 1 GHz is supplied to the pair of antennas 10. Further, FIG. 10 shows a simulation result of a magnetic field formed by the pair of antennas 10 when a high frequency current having a frequency of 5 GHz is supplied to the pair of antennas 10.

As described above, high frequency currents synchronized in frequency and phase flow in the same direction in the pair of loop conductors 12B facing each other. The diamond element 2 is present between the pair of loop conductors 12A and 12B facing each other. As a result, as shown in FIGS. 9 and 10, the magnetic flux formed by one radiating element 12 and the magnetic flux formed by the other radiating element 12 are in the same direction (perpendicular to both sides of the diamond element 2). It passes through the diamond element 2 in the direction). That is, the magnetic flux formed by one radiating element 12 and the magnetic flux formed by the other radiating element 12 are superimposed at the position of the diamond element 2. It has been confirmed by the simulation carried out by the inventor of the present application that this phenomenon occurs in both the case where the frequency of the high frequency current supplied to the pair of loop conductors 12B is 1 GHz and the case where the frequency is 5 GHz. Therefore, according to the sensor 1 of the present embodiment, a uniform magnetic field is generated in a wide frequency band with respect to the NV center by using a pair of antennas 10 having a microwave radiation amount range having the same dimensions as the diamond element 2. Can be made to.

Hereinafter, a simulation carried out by the present inventor to confirm the effect of the antenna 10 of the present embodiment will be described. FIG. 11 is a graph showing a simulation result of the magnetic field strength of the antenna of the embodiment (magnetic field strength on the observation line set on the diamond element 2). As shown in this figure, the observation line is set at the center of the diamond element 2 in the thickness direction. This observation line is set so as to pass through the center point of the diamond element 2 from one of the opposite sides of the diamond element 2 to the other. The left end of the observation line in the figure corresponds to the position of 0.0 [mm] in the graph, and the right end of the observation line in the figure corresponds to the position of 2.0 [mm] in the graph.

In this simulation, a high-frequency current having a synchronized frequency and phase was supplied to the pair of loop conductors 12B so as to flow in the same direction, and a magnetic flux passing through the diamond element 2 was generated. The frequency of the high frequency current was changed to 1 GHz, 2 GHz, 3 GHz, 4 GHz, and 5 GHz. As a result, as shown in the graph of FIG. 11, it can be confirmed that the magnetic field strength is about 8.0 [A / m] or more at any frequency of 1 to 5 GHz. Further, it can be confirmed that the magnetic field strength at the center of the observation line (position of 1.0 mm) is as high as the magnetic field strength at both sides of the observation line (position of 0.3 mm and 1.7 mm).

The present inventor carried out a simulation for confirming the difference in effect depending on the number of loop conductors. FIG. 12 is a diagram showing a simulation result of the magnetic field strength directly above the antenna having three loop conductors 12S. FIG. 13 is a diagram showing a simulation result of the magnetic field strength directly above the antenna having four loop conductors 12S. FIG. 14 is a diagram showing a simulation result of the magnetic field strength directly above the antenna having five loop conductors 12S. In these simulation models, a capacitor 13S is set on the upper side of the pair of upper and lower opposite sides of each loop conductor 12S.

The magnetic field strength in this simulation is the magnetic field strength in a rectangular region of 5 mm in length × 5 mm in width directly above the antenna, and assumes the magnetic field strength in the surface of the diamond element 2 facing the antenna. The magnetic field generation region of the antenna is a rectangular region having a length of 5 mm and a width of 5 mm. The feeding point was set on the second loop conductor from the outer peripheral side in any of the three, four, and five loop conductors 12S.

In this simulation, the frequency of the high frequency current was swept in the range of 1 to 5 GHz. 12, 13, and 14 show the distribution of the magnetic field strength directly above the antenna when the frequency of the high frequency current is 1 GHz, 2 GHz, 3 GHz, 4 GHz, and 5 GHz. The region shown by hatching in these figures is a region having a magnetic field strength of 10 A / m or more. From these figures, it can be confirmed that as the number of loop conductors 12S increases, the region where the magnetic field strength is 10 A / m or more becomes wider and the antenna characteristics become better.

The present inventor carried out a simulation to confirm the effect of the antenna of the comparative example. FIG. 15 is a graph showing the simulation results of the magnetic field strength of the antenna of the comparative example. As shown in this figure, the radiating element 12'of the antenna of the comparative example is a loop element having a resonance frequency of 3 GHz and a surrounding area of a square having a length of 2 mm and a width of 2 mm. That is, the radiating element 12'of the antenna of the comparative example has a configuration in which the loop conductor 12A on the inner peripheral side is removed from the radiating element 12 of the antenna 10 of the present embodiment. Further, in the sensor of the comparative example, one antenna is provided on one side of the diamond element 2, and the configuration is different from that of the sensor 1 of the present embodiment in which the diamond element 2 is sandwiched between the pair of antennas. The observation line is set in the same manner as in the simulation of the above embodiment.

In this simulation, a high-frequency current was supplied to the radiating element 12'with only one loop conductor to generate a magnetic flux passing through the diamond element 2. The frequency of the high frequency current was changed to 1 GHz, 2 GHz, 3 GHz, 4 GHz, and 5 GHz. As a result, as shown in the graph of FIG. 15, it can be confirmed that the magnetic field strength at the position of the center (1.0 mm) of the observation line is lower than that of the above embodiment. In particular, when the frequency is 1 GHz, it can be confirmed that the magnetic field strength is inferior to that of the above embodiment so that the magnetic field strength is less than about 7.0 [A / m].

In addition, the present inventor carried out a simulation to confirm the effect of the antenna of the second comparative example. FIG. 16 is a diagram showing the distribution of the magnetic field strength of the antenna of the second comparative example. As shown in this figure, the antenna 100 of the second comparative example has two parallel coplanar lines 101 formed on the substrate 102. The diamond element 2 is provided facing a part of the two Coplanar lines 101. The range shown by the broken line in the figure is a range in which the magnetic field strength of less than 0.1 [A / m] is significantly reduced.

In this simulation, a high-frequency current was supplied to the two Coplanar lines 101 to generate magnetic flux. The frequency of the high frequency current was changed to 1 GHz, 3 GHz, and 5 GHz. As a result, it can be confirmed that the magnetic field strength is not uniform along the coplanar line 101, although the magnetic flux is formed around the two coplanar lines 101. Here, when the frequencies are 3 GHz and 5 GHz, it can be confirmed that a range in which the magnetic field strength is remarkably lowered occurs at predetermined intervals along the Coplanar line 101. In particular, when the frequency is 5 GHz, it can be confirmed that the magnetic field strength is remarkably lowered at the position where it overlaps with the diamond element 2.

On the other hand, in the sensor 1 of the present embodiment, a plurality of loop conductors 12A and 12B having different peripheral lengths are arranged at intervals from each other so as to be located on the outer peripheral side as the peripheral length increases. The resonance frequencies are different from each other. By adopting such a configuration, the resonance frequency of each of the loop conductors 12A and 12B can be appropriately set according to the magnetic field strength to be measured and its range. In addition, it is possible to expand the region where the magnetic field strength is high in the rectangular microwave radiation region. Further, the magnetic field strength generated from the antenna 10 can be amplified by utilizing resonance. Further, a high-frequency current having a synchronized frequency and phase flows in the same direction in a pair of loop conductors 12B facing each other, so that a magnetic flux formed by one radiating element 12 and a magnetic flux formed by the other radiating element 12 Passes through the diamond element 2 in the same direction. That is, the magnetic flux formed by one radiating element 12 and the magnetic flux formed by the other radiating element 12 are superimposed at the position of the diamond element 2. Therefore, according to the sensor 1 of the present embodiment, even when the antenna 10 is miniaturized according to the size of the diamond element 2, the miniaturized antenna 10 is stable in a wide frequency band such as 1 to 5 GHz. It becomes possible to emit a high-power microwave MW. Therefore, the sensor 1 using the diamond element 2 having an NV center can be stably operated in a wide frequency band due to the limitation of miniaturization.

Further, according to the antenna 10 according to the present embodiment, since the generated magnetic field strength is amplified by using resonance, the antenna 10 is increased in output and the energy input to the antenna 10 is increased due to the limitation of miniaturization. Can be reduced.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-described embodiments, and changes may be made without departing from the spirit of the present invention. May be combined.

For example, in the present embodiment, the element having the color center to be excited is a diamond element having an NV center, but the element is a diamond element having a SnV color center composed of tin (Sn) and pores, silicon ( Other devices such as a diamond element having a SiV color center composed of Si) and holes, or a diamond element having a GeV color center composed of germanium (Ge) and holes may be used.

Further, in the present embodiment, the capacitors 13A and 13B are provided in the loop conductors 12A and 12B in order to adjust the resonance frequency of the loop conductors 12A and 12B, but the resonance frequency of the loop conductors 12A and 12B depends on the capacitors 13A and 13B. If the desired value can be obtained without adjustment, the capacitors 13A and 13B may not be provided. Further, when the capacitors 13A and 13B are provided, it is not essential to provide the capacitors 13A and 13B to all the loop conductors 12A and 12B, and the loop conductors 12A and 12B provided with the capacitors 13A and 13B and the loop without the capacitors 13A and 13B are provided. Conductors 12A and 12B may be mixed.

Further, in the present embodiment, the two loop conductors 12A and 12B are provided, but the number of the loop conductors 12A and 12B may be appropriately increased or decreased depending on the size of the element having the color center. Further, in the present embodiment, the shapes of the loop conductors 12A and 12B are square, but other loop shapes such as a circle and a triangle may be used. Further, the "loop conductor" described in the present specification includes both an endless one due to the presence of one or more gaps and an endless one due to the absence of a gap. Further, in the present embodiment, the feeding points are set for the two loop conductors 12B, but the number and positions of the feeding points are determined by the strength and intensity distribution of the magnetic field generated from the antenna 10, the size of the element having the color center, and the like. It may be set appropriately accordingly. The number of feeder lines 14A and 14B may be one.

Further, in the present embodiment, the radiating element 12 of the antenna 10 is provided on the substrate 11, but the radiating element 12 of the antenna 10 may be provided on the surface of the diamond element 2. That is, the radiating element 12 of the antenna 10 may be formed on one of the pair of square surfaces parallel to each other of the diamond element 2 and the other. In this case, since the substrate 11 is not required, the sensor 1 can be further miniaturized.

1: Sensor 2: Diamond element (element)
3: Optical system 4: Optical sensor 6: Power amplifier (feeder)
10: Antenna (antenna for color center excitation)
11: Substrate 12: Radiant element 12A, 12B: Loop conductor 13A, 13B: Capacitor 14A, 14B: Feed line (first feed line, second feed line)
G1: Gap (first gap)
G2: Gap (first gap)
G3: Gap (second gap)
GL: Green light RL: Red fluorescent MW: Microwave

Claims (6)

An element having a color center to be excited and
A pair of color center excitation antennas provided across the element,
The pair of color center excitation antennas is equipped with a feeder that supplies a high-frequency current with variable frequency.
The color center excitation antenna is
A substrate provided facing the element and
A radiating element formed on a surface of the substrate facing the element and supplied with the high frequency current by the feeder to radiate microwaves is provided.
The radiating element comprises a plurality of loop conductors.
The plurality of loop conductors have different lengths in the circumferential direction, and are arranged at intervals so as to be located on the outer peripheral side as the length in the circumferential direction increases, and the resonance frequencies of the plurality of conductors are different from each other. Different,
In the feeder, the magnetic flux formed by the radiating element of one of the color center excitation antennas and the magnetic flux formed by the radiating element of the other color center exciting antenna pass through the element in the same direction. As described above, a sensor that supplies the high frequency current to the radiating element of the pair of color center excitation antennas. The sensor according to claim 1, wherein the feeder supplies the pair of radiating elements with the high-frequency current having a synchronized frequency and phase so as to flow in the same direction. At least one of the plurality of loop conductors has a first gap formed.
The sensor according to claim 1 or 2, further comprising a capacitor provided at a position overlapping the first gap and electrically connected to the loop conductor in which the first gap is formed. A second gap is formed in at least one of the plurality of loop conductors, and one end and the other end of the loop conductor face each other with the second gap interposed therebetween.
A first feeder connected to one end of the loop conductor,
The sensor according to any one of claims 1 to 3, further comprising a second feeder connected to the other end of the loop conductor. An element having a color center to be excited and
A pair of color center excitation antennas provided across the element,
The pair of color center excitation antennas is equipped with a feeder that supplies a high-frequency current with variable frequency.
The color center excitation antenna is
A radiating element formed on the surface of the element and supplied with the high frequency current by the feeder to radiate microwaves is provided.
The radiating element comprises a plurality of loop conductors.
The plurality of loop conductors have different lengths in the circumferential direction, and are arranged at intervals so as to be located on the outer peripheral side as the length in the circumferential direction increases, and the resonance frequencies of the plurality of conductors are different from each other. Different,
In the feeder, the magnetic flux formed by the radiating element of one of the color center excitation antennas and the magnetic flux formed by the radiating element of the other color center exciting antenna pass through the element in the same direction. As described above, a sensor that supplies the high frequency current to the radiating element of the pair of color center excitation antennas. An optical system that irradiates the element with green light,
It is equipped with an optical sensor that detects the brightness of red fluorescence generated from the element.
The sensor according to any one of claims 1 to 5, which measures at least one of a magnetic field, an electric field, and a temperature according to the brightness of the red fluorescence detected by the optical sensor.

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