Detection device and electromagnetic wave detection method

Abstract

To provide an electromagnetic wave detection device having high spatial resolution and high detection sensitivity.SOLUTION: A detection device 10 comprises: a diamond crystal 101 having a NV center; an electromagnetic wave supply unit for supplying, to the diamond crystal 101, a supply electromagnetic wave which is either a first electromagnetic wave having a magnetic field of a first amplitude or a second electromagnetic wave having a magnetic field of a second amplitude different from the first amplitude, in accordance with a prescribed supply sequence; a light receiving unit for acquiring a first received light signal based on first fluorescence having intensity corresponding to the amplitude of the first electromagnetic wave and a second received light signal based on second fluorescence having intensity corresponding to the second amplitude of the second electromagnetic wave; a detection signal generation unit 1035 for generating a first detection signal based on the first received light signal and a second detection signal based on the second received light signal; and an image generation unit 1036 for generating, on the basis of the first and second detection signals, a detection image 1501 that indicates the distribution of an external magnetic field that enters the diamond crystal.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a detection device and an electromagnetic wave detection method. [Background technology]

[0002] There is a technology for visualizing the distribution of radio frequency (RF) signals and electromagnetic waves on the surface of an object or in a space distant from the object. Patent Document 1 shows an RF sensor system having a plurality of magnetoresistive sensors, each of which generates an output voltage in response to an external magnetic field that changes over time, thereby visualizing the intensity distribution of the electromagnetic waves. The intensity of the electromagnetic waves is, for example, the amplitude of an electric field or a magnetic field. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2009-014720 A Summary of the Invention [Problem to be solved by the invention]

[0004] When electrically coupled magnetoresistance sensors are arranged and the intensity of the electromagnetic wave is visualized using the output of each magnetoresistance sensor, as in the RF sensor system described in Patent Document 1, the spatial resolution and the number of pixels are limited by the size of the sensor and the number of arrangements between the sensors. When the spatial resolution and the number of pixels are limited, it becomes difficult to visualize the electromagnetic wave from a small object. Furthermore, when the object is small, the signal strength of the electromagnetic wave may be small, so in addition to the spatial resolution, it is necessary to increase the detection sensitivity. In addition, the influence of mutual interference between sensors and between the sensor and the object is unavoidable, the method of correcting the influence of mutual interference is complicated, and the measurement accuracy is reduced. For these reasons, it has been difficult to visualize the intensity of the electromagnetic wave with a high spatial resolution on the order of μm to mm.

[0005] SUMMARY OF THE PRESENT EMBODIMENTS An object of the present invention is to provide an electromagnetic wave detection device having high spatial resolution and high detection sensitivity. [Means for solving the problem]

[0006] a first detection signal based on the first fluorescence and a second detection signal based on the second fluorescence as received light signals; an electromagnetic wave supply unit that supplies a detection image showing the distribution of an external electromagnetic field incident on the diamond crystal based on the first detection signal and the second detection signal; and an image generation unit that generates a detection image showing the distribution of an external electromagnetic field incident on the diamond crystal based on the first detection signal and the second detection signal.

[0007] In the detection device of the above aspect, a first electromagnetic wave having a magnetic field of a first amplitude and a second electromagnetic wave having a magnetic field of a second amplitude are supplied to the NV center of the diamond crystal at different timings.

[0008] The spins of the NV center to which the first electromagnetic wave is supplied undergo Rabi oscillations (first Rabi oscillations) having a first frequency corresponding to the first amplitude. The spins undergoing the first Rabi oscillations are strongly affected by an external electromagnetic field having a frequency close to the first frequency. The spins undergoing the first Rabi oscillations emit stronger fluorescence as the frequency of the external electromagnetic field becomes closer to the first frequency.

[0009] The spins of the NV center to which the second electromagnetic wave is supplied undergo Rabi oscillations (second Rabi oscillations) having a second frequency according to the second amplitude. Since the second amplitude is different from the first amplitude, the second frequency is different from the first frequency. If the second amplitude is larger than the first amplitude, the second frequency is higher than the first frequency.

[0010] The spins undergoing the second Rabi oscillation are strongly affected by an external electromagnetic field having a frequency close to the second frequency, and the spins undergoing the second Rabi oscillation emit stronger fluorescence as the external electromagnetic field has a frequency close to the second frequency.

[0011] The light receiving unit acquires a first light receiving signal based on the first electromagnetic wave and the external electromagnetic field and a second light receiving signal based on the second electromagnetic wave and the external electromagnetic field, which are generated as a result of the laser irradiation unit exciting the NV center. The detection signal generating unit generates a first detection signal based on the first light receiving signal and a second detection signal based on the second light receiving signal.

[0012] The first detection signal is a signal indicative of the strength of an external electromagnetic field of a first frequency detected by the NV center supplied with the first electromagnetic wave, and the second detection signal is a signal indicative of the strength of an external electromagnetic field of a second frequency detected by the NV center supplied with the second electromagnetic wave.

[0013] The image generating section generates a detection image showing the distribution of the intensity of the external electromagnetic field incident on the diamond crystal based on the first detection signal and the second detection signal.

[0014] The first detection signal alone cannot adequately image the distribution of the intensity of the external electromagnetic field. This is because, when the frequency of the external electromagnetic field is far from the first frequency, the first detection signal is hardly affected by the external electromagnetic field. Therefore, even if the first detection signal has a signal intensity that is spatially distributed in the diamond crystal, it is difficult to distinguish whether the distribution of the intensity is a distribution caused by noise or a distribution that reflects the external electromagnetic field. This makes it difficult to adequately image the distribution of the intensity of the external electromagnetic field.

[0015] Therefore, the detection device further acquires a second detection signal indicating the intensity of the external electromagnetic field at a second frequency different from the first frequency. The first detection signal and the second detection signal make it possible to calculate the intensity of the external electromagnetic field at each of the first frequency and the second frequency. By using the first detection signal and the second detection signal as the basis, the influence of the intensity distribution of the external electromagnetic field caused by noise can be suppressed.

[0016] The detection device has high spatial resolution by using minute structures called NV centers, and has high detection sensitivity by using detection signals of external electromagnetic fields at different frequencies.

[0017] In the above aspect, the second amplitude is greater than the first amplitude, the electromagnetic wave supply unit supplies any one of the first electromagnetic wave, the second electromagnetic wave, or a third electromagnetic wave having a magnetic field with a third amplitude greater than the second amplitude to the diamond crystal in accordance with a supply sequence, the light receiving unit receives a third fluorescence having a third intensity corresponding to the third amplitude of the third electromagnetic wave from the NV center excited by the laser and obtains a third received light signal based on the third fluorescence as the received light signal, the detection signal generation unit generates a third detection signal based on the third received light signal as the detection signal, the image generation unit calculates a background signal based on the third detection signal and the first detection signal, and the image generation unit generates a detection image based on a signal obtained by removing the background signal from the second detection signal.

[0018] The detection signal generating unit calculates a background signal as noise based on the first detection signal and the third detection signal. The image generating unit can generate a detection image based on a signal obtained by removing the background signal from the second detection signal, thereby suppressing the influence of the intensity distribution of an external electromagnetic field caused by noise.

[0019] When the frequency of the second Rabi oscillation due to the second electromagnetic wave having a magnetic field of the second amplitude is close to the frequency of the external electromagnetic field, the second detection signal has a large value. Since the second amplitude is a magnetic field amplitude having an intermediate magnitude between the first amplitude and the third amplitude, the third frequency, which is the frequency of the third Rabi oscillation based on the first frequency and the third electromagnetic wave, has a value far from the frequency of the external electromagnetic field. Therefore, the values ​​of the first detection signal and the third detection signal are smaller than the second detection signal. Therefore, when the intensities of the first detection signal, the second detection signal, and the third detection signal are plotted with frequency on the horizontal axis, the frequency plot has an extreme value based on the second detection signal.

[0020] The detection device detects and visualizes an external electromagnetic field with higher detection sensitivity by generating a detection image based on the second detection signal, which is an extreme value and from which the background signal has been removed.

[0021] In the above embodiment, the supply sequence includes a first supply sequence and a second supply sequence, and the electromagnetic wave supply unit may, in the first supply sequence, supply to the diamond crystal a supply electromagnetic wave that sets the spin state of the NV center to a first spin state, supply to the diamond crystal a supply electromagnetic wave that has a magnetic field oscillating in a first spin direction of the first spin state and sets the spin state to a second spin state, and supply to the diamond crystal a supply electromagnetic wave that sets the second spin state to a third spin state.

[0022] In addition, in the second supply sequence, the electromagnetic wave detection unit may supply to the diamond crystal a supply electromagnetic wave that sets the spin state to a first spin state, supply to the diamond crystal a supply electromagnetic wave having a magnetic field oscillating in the first spin direction that sets the spin state to a second spin state, and supply to the diamond crystal a supply electromagnetic wave that sets the second spin state to a fourth spin state having a spin direction opposite to the spin direction of the third spin state.

[0023] In addition, the light receiving unit may acquire a third light receiving signal emitted from the NV center in the third spin state and a fourth light receiving signal emitted from the NV center in the fourth spin state, and the detection signal generating unit may generate a detection signal based on the difference between the third light receiving signal and the fourth light receiving signal.

[0024] By the first supply sequence and the second supply sequence, the light receiving unit can obtain two light receiving signals, the third light receiving signal and the fourth light receiving signal, based on the amplitude of the magnetic field of the supplied electromagnetic wave having a certain amplitude. The third light receiving signal and the fourth light receiving signal have opposite spin directions of the spin states on which they are based. The NV center in the second spin state is affected by the external electromagnetic field of the detection target and other noise. Since the direction of the noise is random, the noise can be canceled by taking the difference between the third light receiving signal and the fourth light receiving signal. Since the third spin state and the fourth spin state are opposite to each other, it is possible to extract the net effect of the external electromagnetic field on the second spin state by taking the difference between the third light receiving signal and the fourth light receiving signal.

[0025] In the above aspect, the electromagnetic wave supply unit may supply, in the second supply sequence, electromagnetic waves that have a phase that is 180 degrees different from the phase of the electromagnetic waves that cause the spin state in the first supply sequence to be the third spin state and that cause the spin state to be the fourth spin state, thereby making it possible to extract the net effect of the external electromagnetic field on the second spin state.

[0026] In the above-mentioned embodiment, diamond crystal may have a plurality of NV centers distributed in the area that occupies a certain volume in the inside of the surface of diamond crystal.This makes it possible to detect the external electromagnetic field from a wider area of ​​the electromagnetic wave detection object that emits the external electromagnetic field.

[0027] A fluorescence detection method according to another aspect of the present invention includes a fluorescence detection device supplying a supply electromagnetic wave, either a first electromagnetic wave having a magnetic field of a first amplitude or a second electromagnetic wave having a magnetic field of a second amplitude different from the first amplitude, to a diamond crystal having NV centers in accordance with a predetermined supply sequence; irradiating the diamond crystal with a laser that excites the NV centers; receiving a first fluorescence having a first intensity corresponding to the first amplitude of the first electromagnetic wave from the NV centers excited by the laser, and receiving a second fluorescence having a second intensity corresponding to the second amplitude of the second electromagnetic wave from the NV centers excited by the laser; acquiring a first received light signal based on the first fluorescence and a second received light signal based on the second fluorescence as received light signals; generating a first detection signal based on the first received light signal and a second detection signal based on the second received light signal as detection signals; and generating a detection image showing the distribution of the intensity of the external electromagnetic field incident on the diamond crystal based on the first detection signal and the second detection signal. Effect of the Invention

[0028] According to the present invention, it is possible to provide an electromagnetic wave detection device having high spatial resolution and high detection sensitivity. [Brief description of the drawings]

[0029] [Figure 1] FIG. 1 is a block diagram of a detection device according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a diagram showing the arrangement of a diamond crystal, an antenna, and a sample according to the present embodiment. [Diagram 3] 1 is a diagram for explaining detection of an external electromagnetic field according to the present embodiment. FIG. [Figure 4] FIG. 4 is a diagram illustrating an example of a first supply sequence according to the present embodiment. [Diagram 5] 10A to 10C are diagrams illustrating an example of a second supply sequence according to the present embodiment. [Figure 6] 10A to 10C are diagrams illustrating another example of the first supply sequence according to the embodiment. [Figure 7] 10A to 10C are diagrams illustrating another example of the second supply sequence according to the embodiment. [Figure 8] 5A and 5B are diagrams illustrating binning of detection signals according to the present embodiment. [Figure 9] 10 is a flowchart for explaining a detection process of an external electromagnetic field according to the present embodiment. [Figure 10] 4 is a diagram for explaining the resonance frequency of the NV center according to the embodiment. FIG. [Figure 11] 10 is a flowchart for explaining a detection image generation process according to the present embodiment. [Figure 12] FIG. 2 is a plan view of an example of a sample according to the embodiment. [Figure 13] FIG. 4 is a diagram for explaining fluorescence intensity according to the embodiment. [Figure 14] FIG. 4 is a diagram for explaining an example of fluorescence intensity according to the embodiment. [Figure 15] FIG. 4 is a diagram for explaining an example of a detection image according to the embodiment. [Figure 16] FIG. 2 is a diagram for explaining an NV center. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0030] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described with reference to the accompanying drawings, in which like reference numerals denote like or similar structures.

[0031] 1 shows a block diagram of a detection device 10 according to this embodiment. The detection device 10 includes a diamond crystal 101, an antenna unit 102, a control unit 103, a pulse generator 104, a laser irradiator 105, an imaging device 106, a local oscillator 107, an arbitrary waveform generator 108, a mixer 109, a switch 110, an amplifier 111, and a signal generator 112. The detection device 10 is used to detect an external electromagnetic field emitted by a sample S.

[0032] The diamond crystal 101 is provided in a position very close to or in contact with the sample S. The diamond crystal 101 has an NV center, which will be described below.

[0033] Here, the NV center will be briefly explained. FIG. 16 shows a structural diagram for explaining the structure of the NV center. The NV center is a complex defect formed by a nitrogen atom N at one of the lattice points of a diamond crystal composed of carbon atoms C and a vacancy V due to the loss of a carbon atom adjacent to the nitrogen atom N. As shown conceptually in FIG. 16, this complex defect can capture an electron e. The electron e has a quantum state (spin s). The NV center strongly absorbs light of a specific wavelength, for example, green laser light, and emits light of another specific wavelength, for example, red fluorescence. The intensity of the fluorescence from the NV center has the characteristic that it changes according to the spin s of the electron e.

[0034] When light of a predetermined wavelength, for example, a green laser, is incident on the diamond crystal 101, the NV centers of the diamond crystal 101 emit light of another predetermined wavelength, for example, red fluorescence. The shapes of the diamond crystal 101 and the antenna portion 102 will be described later.

[0035] The antenna portion 102 is provided in contact with the diamond crystal 101. The diamond crystal 101 is sandwiched between the antenna portion 102 and the sample S. The antenna portion 102 transmits an electromagnetic wave (supplied electromagnetic wave) based on a radio frequency signal having a predetermined frequency and a selected amplitude, which is input via the amplifier 111, to the diamond crystal 101, thereby propagating the electromagnetic wave to the diamond crystal 101.

[0036] The control unit 103 is a control component connected to the pulse generator 104, the imaging device 106, the local oscillator 107, and the arbitrary waveform generator 108. The control unit 103 is a device that performs various controls for the detection of electromagnetic waves by the detection device 10. The physical configuration of the control unit 103 includes a CPU (Central Processing Unit) that performs processes required for control, a RAM (Random Access Memory), a ROM (Read Only Memory), or an HDD (Hard Disk Drive) as a storage area, and a communication device that performs various communications.

[0037] The control unit 103 includes, as functional components, a storage unit 1031, a signal generating unit 1032, an electromagnetic wave supply control unit 1033, a light receiving signal acquiring unit 1034, a detection signal generating unit 1035, and an image generating unit 1036. Each of these units is realized, for example, by using a storage area such as a RAM or a ROM, or by the CPU executing a program stored in the storage area. For example, the program is stored in the storage unit 1031.

[0038] The storage unit 1031 is a storage area in which programs and information necessary for various processes in the control unit 103 are stored.

[0039] The signal generating unit 1032 controls the signal generator 112 described below, thereby controlling the supply of a radio frequency signal (RF signal) to the sample S. The "radio frequency signal" means a signal having a frequency band used for wireless communication. The radio frequency signal is supplied to the sample S via a wired connection. Note that the radio frequency signal may also be supplied to the sample S wirelessly.

[0040] The electromagnetic wave supply control unit 1033 controls the local oscillator 107 and the arbitrary waveform generator 108 to control the supply of electromagnetic waves to the antenna unit 102 .

[0041] The light reception signal acquisition unit 1034 acquires, from the image capturing device 106, a light reception signal based on the fluorescence from the NV center detected by the image capturing device 106.

[0042] The detection signal generating unit 1035 generates a detection signal based on the received light signal acquired by the received light signal acquiring unit 1034 .

[0043] The image generating unit 1036 generates a detection image showing the intensity distribution of the external electromagnetic field emitted by the sample S to the outside, based on the detection signal generated by the detection signal generating unit 1035.

[0044] Specific processing by each unit of control unit 103 will be described later.

[0045] The pulse generator 104 is connected to the control unit 103, the laser irradiator 105, the image pickup device 106, the arbitrary waveform generator 108, and the switch 110. The pulse generator 104 supplies a pulse signal having a predetermined pulse width (hereinafter also simply referred to as a "pulse") to the laser irradiator 105, the image pickup device 106, the arbitrary waveform generator 108, and the switch 110 under the control of the control unit 103.

[0046] The pulse generator 104 supplies a pulse for an RF signal to be supplied to the antenna unit 102 to the switch 110. The pulse generator 104 supplies an irradiation pulse for controlling laser irradiation by the laser irradiator 105 to the laser irradiator 105. The pulse generator 104 supplies an imaging pulse for triggering imaging timing by the imaging device 106 to the imaging device 106. The pulse generator 104 supplies a waveform generation pulse for controlling signal generation by the arbitrary waveform generator 108 to the arbitrary waveform generator 108. The pulse generator 104 supplies a switching control pulse for controlling on / off switching of the switch 110 to the switch 110.

[0047] The laser irradiator 105 irradiates laser light L having a frequency of . For example, the wavelength of the laser light L is 520 nm, and the laser light L is a green laser. The output of the laser light L is 7 mW, for example. Note that the wavelength and output of the laser light L are not limited to the above values, and may be any value capable of exciting the NV center of the diamond crystal 101.

[0048] Laser light L is irradiated onto diamond crystal 101 through an optical system having mirror 1051, half mirror 1052, and objective lens 1053. The laser irradiator 105, mirror 1051, half mirror 1052, and objective lens 1053 can be collectively referred to as a laser irradiation unit.

[0049] The imaging device 106 receives the fluorescence PL emitted from the diamond crystal 101 irradiated with the laser light L. The fluorescence has a frequency and wavelength that results in red fluorescence, for example. The imaging device 106 receives the fluorescence PL emitted from the diamond crystal 101 through the objective lens 1053, the long wavelength filter 1061, and the imaging lens 1062. The long wavelength filter 1061 is a filter that transmits fluorescence with a wavelength longer than red. The imaging lens 1062 is a lens that adjusts the fluorescence so that it is suitable for reception by the imaging device 106.

[0050] The imaging device 106 is, for example, a CMOS camera having a plurality of light receiving elements. When a CMOS camera is used for the imaging device 106, the CMOS camera may be a cooled CMOS camera. The imaging device 106 generates a light receiving signal based on the incidence of fluorescent light on the light receiving element. The generated light receiving signal is transmitted to a light receiving signal acquisition unit 1034. The imaging device 106 and the light receiving signal acquisition unit 1034 can be collectively referred to as a light receiving unit. Note that the half mirror 1052 and the objective lens 1053 may be included in both the laser irradiation unit and the light receiving unit.

[0051] The local oscillator 107 is connected to the control unit 103 and the mixer 109. The local oscillator 107 generates an RF signal of a predetermined frequency based on a signal from the electromagnetic wave supply control unit 1033. The local oscillator 107 transmits the generated RF signal to the mixer 109.

[0052] The arbitrary waveform generator 108 supplies mutually orthogonal I and Q signals to the mixer 109 based on the waveform generation pulse from the pulse generator 104. The I and Q signals are signals whose phases differ by π / 2.

[0053] The mixer 109 generates a signal obtained by pulsing the RF signal based on the RF signal from the local oscillator 107 and the I signal and the Q signal from the arbitrary waveform generator 108. The pulsed RF signal is transmitted to the switch 110.

[0054] The switch 110 is a switch that connects the mixer 109 and the amplifier 111 so that the pulsed RF signal from the mixer 109 is supplied to the antenna unit 102 through the amplifier 111 based on a switching control pulse from the pulse generator 104. The switch 110 is controlled so as to be on only when the mixer 109 is generating a pulsed RF signal.

[0055] The amplifier 111 amplifies the power of the pulsed RF signal. The amplifier 111 supplies the amplified pulsed RF signal to the antenna unit 102. The antenna unit 102, the control unit 103, the pulse generator 104, the local oscillator 107, the arbitrary waveform generator 108, the mixer 109, and the switch 110 can be collectively referred to as an electromagnetic wave supply unit.

[0056] The signal generator 112 supplies a predetermined radio frequency signal (RF signal) to the sample S based on a signal from the signal generating unit 1032. The RF signal generated by the signal generator 112 is a signal generated independently of the RF signal generated by the local oscillator 107. By supplying the RF signal to the sample S, an external electromagnetic field is generated by the sample S in the vicinity of the diamond crystal 101.

[0057] An outline of how the detection device 10 detects an external electromagnetic field is as follows. A pulsed RF signal is supplied to the antenna unit 102. The antenna unit 102 supplies electromagnetic waves to the diamond crystal 101 based on the pulsed RF signal. The supplied electromagnetic waves put the diamond crystal 101 in a state that enables it to detect the external electromagnetic field.

[0058] When an RF signal is supplied to the sample S, an external electromagnetic field is generated near the diamond crystal 101. The laser irradiator 105 irradiates the diamond crystal 101, which is affected by the external electromagnetic field, with laser light L. The diamond crystal 101 is excited by the laser light L and emits fluorescence PL. The fluorescence PL is input to the imaging device 106, and a received light signal is acquired by the received light signal acquisition unit 1034.

[0059] The control unit 103 is supplied with a pulse signal from a pulse generator 104. The timing of supplying an RF signal to the antenna unit 102, irradiating the laser light L by the laser irradiator 105, and generating a light receiving signal by the imaging device 106 are synchronized by the pulse signal.

[0060] The detection signal generating unit 1035 generates a detection signal based on the light receiving signal at a certain timing. The image generating unit 1036 generates a detection image indicating the intensity distribution of the external electromagnetic field in the sample S based on the detection signal.

[0061] The structures of the diamond crystal 101, the antenna portion 102, and the sample S will be described with reference to FIG.

[0062] The diamond crystal 101 has a diamond crystal layer 201 and an NV center layer 202 .

[0063] The diamond crystal layer 201 is a diamond crystal structure having a main surface parallel to the xy plane. The diamond crystal layer 201 is provided sandwiching an NV center layer 202. Since the diamond crystal 101 is divided by the NV center layer 202, the diamond crystal layer 201 is called a layer for convenience.

[0064] The NV center layer 202 is a layer containing a plurality of NV centers formed in the diamond crystal 101. The NV center layer 202 is formed in a predetermined range, for example, a range of about 10 nm, in the positive z-axis direction from the surface facing the negative z-axis direction of the diamond crystal layer 201. The NV center layer 202 is distributed inside the surface of the diamond crystal, in a range occupying a predetermined volume in the diamond crystal.

[0065] A static magnetic field is applied by permanent magnets 207a and 207b to the NV center of the NV center layer 202. The static magnetic field separates the degeneracy of the spin state of the NV center of the NV center layer 202, making it detectable by the detection device 10.

[0066] The antenna unit 102 has a substrate 203 and an antenna 204. The substrate 203 is, for example, a mounting substrate formed from a resin material. The antenna 204 is a metal pattern formed in the substrate 203 parallel to the main surface of the diamond crystal 101. The antenna 204 can be made of, for example, gold. When a signal MW is input through the amplifier 111, the antenna 204 emits an electromagnetic wave to the diamond crystal 101.

[0067] The sample S has a substrate 205 and wiring 206. The substrate 205 has a main surface parallel to the main surface of the diamond crystal 101. The substrate 205 is a mounting substrate formed of, for example, a resin material. Although the sample S and the diamond crystal 101 are shown in FIG. 2 as being in contact with each other, they may be separated by a small distance.

[0068] The wiring 206 is a metal wiring formed on the substrate 205. The material of the wiring 206 is, for example, a Ti / Au alloy. The wiring 206 is formed on the substrate 205 by using photolithography.

[0069] A signal RF, which is a radio frequency signal, is input to the wiring 206 via the signal generator 112. The signal RF causes the wiring 206 to emit an external electromagnetic field toward the outside.

[0070] With reference to FIG. 3, an overview of how the detection device 10 detects an external electromagnetic field will be described.

[0071] In the detection device 10, as process (A), a signal RF is supplied to the wiring 206. The wiring 206 emits an external electromagnetic field based on the signal RF.

[0072] In the next process (B), laser light L1 from a laser irradiator 105 is irradiated onto the diamond crystal 101, more specifically, onto the NV center layer 202. The NV centers of the NV center layer 202 irradiated with the laser light L1 are initialized to have a predetermined spin state.

[0073] In process (C), a signal MW is input to the antenna 204, and an electromagnetic wave from the antenna 204 is supplied to the NV center layer 202. The supplied electromagnetic wave sets the NV centers in the NV center layer 202 to a spin state capable of detecting a predetermined external electromagnetic field.

[0074] In process (D), the external electromagnetic field emitted by the wiring 206 affects the spin state of the NV centers in the NV center layer 202, so that the strength of the external electromagnetic field is reflected in the spin state of the NV centers in the NV center layer 202.

[0075] In process (E), the laser beam L2 from the laser irradiator 105 is irradiated onto the NV center layer 202. The laser beam L2 is a laser beam for reading out the spin state of the NV center in the NV center layer 202.

[0076] In process (F), fluorescence PL is emitted from the NV centers of the NV center layer 202 excited by the laser light L2. The fluorescence PL passes through the half mirror 1052 and is detected by the imaging device 106.

[0077] Through the above process, the strength of the external electromagnetic field emitted by the wiring 206 is detected.

[0078] The sequence of irradiating laser light by laser irradiator 105 and supplying electromagnetic waves to diamond crystal 101 by antenna section 102 will be described with reference to FIGS.

[0079] 4 shows a laser supply sequence LS, and electromagnetic wave supply sequences MSx and MSy (first supply sequence). The laser supply sequence LS indicates that the laser irradiator 105 irradiates the diamond crystal 101 with laser light for a predetermined time τ.

[0080] By irradiating the laser light, the spin state of the NV center is initialized to the |0〉 state. The initialized spin direction is oriented in the positive z-axis direction in a three-dimensional xyz rotating coordinate system.

[0081] The electromagnetic wave supply sequence MSx indicates that the antenna section 102 supplies to the diamond crystal 101 an electromagnetic wave (first electromagnetic wave) having a magnetic field of a predetermined amplitude A1 (first amplitude) and causing the spin state of the NV center in the NV center layer 202 to become a predetermined spin state. Specifically, an electromagnetic wave is supplied that rotates the spin direction by 90 degrees in the positive direction of the x-axis in the above coordinate system. This electromagnetic wave is also called a π / 2 pulse.

[0082] By supplying the first π / 2 pulse in the electromagnetic wave supply sequence MSx, the initialized spin state becomes a predetermined spin state (first spin state).

[0083] By the second supply of the π / 2 pulse in the electromagnetic wave supply sequence MSx, the spin state based on the electromagnetic wave supply sequence MSy described below becomes a predetermined spin state (third spin state).

[0084] The electromagnetic wave supply sequence MSy indicates that the antenna portion 102 supplies electromagnetic waves having a magnetic field of amplitude A1, which sets the spin state of the NV center in the NV center layer 202 to a predetermined spin state (second spin state), to the diamond crystal 101. The second spin state becomes a dressed state, which is a hybrid state of spin and electromagnetic wave, as shown in the following mathematical formula.

number

[0085] An energy gap Ω1 occurs between the dressed spins |+〉 and |-〉. The energy gap Ω1 corresponds to the energy of an electromagnetic wave with a Rabi frequency proportional to the amplitude A1. The Rabi frequency is the frequency of Rabi oscillations that repeatedly transition between energy states when irradiated with electromagnetic waves.

[0086] The spins are only affected by electromagnetic waves with the same energy as the energy gap Ω1, i.e., electromagnetic waves with frequencies that resonate with the energy gap Ω1. They are not affected by electromagnetic waves with frequencies that do not resonate with the energy gap Ω1.

[0087] After the electromagnetic wave is applied to the diamond crystal 101 for a predetermined time by the electromagnetic wave supply sequence MSy, a second π / 2 pulse is supplied in the electromagnetic wave supply sequence MSx. This supply causes the spin state of the NV center to become a predetermined spin state (third spin state).

[0088] FIG. 5 shows a laser supply sequence LS and electromagnetic wave supply sequences MSx and MSy (second supply sequence). The second supply sequence differs from the first supply sequence in the second supply of the electromagnetic wave in the electromagnetic wave supply sequence MSx. In the electromagnetic wave supply sequence MSx of the second supply sequence, an electromagnetic wave that rotates the spin direction by 90 degrees in the negative x-axis direction is supplied in the second supply of the electromagnetic wave. This electromagnetic wave is also called a -π / 2 pulse. By supplying a -π / 2 pulse in the electromagnetic wave supply sequence MSx, the spin state based on the electromagnetic wave supply sequence MSy described below becomes a predetermined spin state (fourth spin state).

[0089] The third spin state and the fourth spin state include the influence of electromagnetic waves resonating with the energy gap Ω in the second spin state and the influence of other noise components. Of these, the influence of electromagnetic waves resonating with the energy gap Ω is approximately the same in the third spin state and the fourth spin state, resulting in spin states with opposite positive and negative signs. In addition, the influence of noise is random in both the third spin state and the fourth spin state.

[0090] Since the third spin state and the fourth spin state are opposite in direction to each other, it is possible to extract the net effect of the external electromagnetic field on the second spin state by taking the difference between the third spin state and the fourth spin state.

[0091] Another example of the first supply sequence is shown in Fig. 6. The difference from the first supply sequence shown in Fig. 4 is that the magnetic field in the electromagnetic wave supply sequences MSx and MSy has an amplitude A2 (second amplitude).

[0092] The amplitude A2 is larger than the amplitude A1. As a result, in the second spin state, the energy gap Ω2 based on the electromagnetic wave of the amplitude A2 (second electromagnetic wave) is larger than the energy gap Ω1 based on the electromagnetic wave of the amplitude A1.

[0093] The energy gap Ω2 is affected by an external electromagnetic field with a higher frequency than the frequency of the external electromagnetic field corresponding to the energy gap Ω1. By changing the amplitude of the magnetic field, the frequency of the external electromagnetic field that can be detected using the energy gap in the second spin state can be changed. In this way, when the frequency of the external electromagnetic field is unknown, the detection device 10 can scan the detection frequency to correspond to the unknown frequency of the external electromagnetic field by scanning the amplitude of the magnetic field.

[0094] FIG. 7 shows a second supply sequence corresponding to the first supply sequence when the magnetic field has an amplitude A2.

[0095] 8, the binning of the signal from the imaging device by the image generating section 1036 will be described. Fluorescence PL from the diamond crystal 101 corresponding to the external electromagnetic field enters the light receiving element 801 of the imaging device .

[0096] The light receiving element 801 has pixels 802, for example, 528×512 pixels, which is a number of pixels that provides sufficient resolution for detecting the intensity distribution of the external electromagnetic field generated by the sample S. If the size of the pixels 802 exceeds the analysis limit of the objective lens 1053, it becomes difficult for each pixel 802 to appropriately detect the fluorescence PL.

[0097] The image generating unit 1036 bins, for example, detection signals corresponding to signals from the 16×16 pixel pixels 802, to generate an image 804 of 33×32 pixels, thereby improving the signal-to-noise ratio and increasing the dynamic range.

[0098] The process up to recording of the detection signal by the detection device 10 will be described with reference to FIG.

[0099] In step S901, the control unit 103 controls the pulse generator 104 so that the laser irradiator 105 irradiates the diamond crystal 101 with laser light.

[0100] In step S902, the received light signal acquisition unit 1034 acquires a signal indicating the fluorescence intensity from the NV centers in the NV center layer 202 through the imaging device 106. The acquired fluorescence intensity is stored in the storage unit 1031.

[0101] In step S903, the electromagnetic wave supply control unit 1033 supplies the antenna unit 102 with an electromagnetic wave of a certain frequency.

[0102] In step S904, the control unit 103 controls the laser irradiator 105 to irradiate the diamond crystal 101 with laser light.

[0103] In step S905, the received light signal acquisition unit 1034 causes the imaging device 106 to acquire fluorescence from the NV centers in the NV center layer 202, and acquires a signal indicating the fluorescence intensity. The acquired fluorescence intensity is stored in the storage unit 1031.

[0104] By repeating the above processes from step S901 to step S905, normalized fluorescence intensities that satisfy the following relationship, normalized fluorescence intensity=(fluorescence intensity with electromagnetic wave applied) / (fluorescence intensity without electromagnetic wave irradiation), are calculated for a plurality of frequencies. An example of the normalized fluorescence intensity is shown in FIG. 10.

[0105] In step S906, the electromagnetic wave supply control unit 1033 can select a frequency at which the normalized fluorescence intensity is small, that is, at which the fluorescence intensity under the supply of electromagnetic waves is reduced by the NV center resonating with the laser light. For example, the frequency f in FIG. 10 can be set as the resonant frequency.

[0106] In step S907, the signal generating unit 1032 supplies an RF signal to the sample S through the signal generator 112. This causes the sample S to generate an external electromagnetic field. The RF signal is, for example, a signal with a frequency of 15 MHz and a power of −30 dBm.

[0107] In step S 908 , the electromagnetic wave supply control unit 1033 selects the amplitude of the magnetic field of the electromagnetic wave that the antenna unit 102 supplies to the diamond crystal 101 .

[0108] In step S909, the electromagnetic wave supply control unit 1033 supplies a signal having a frequency that is the resonant frequency and a selected amplitude to the diamond crystal 101 in accordance with the first sequence. At this time, the laser irradiator 105 irradiates a laser in accordance with the laser supply sequence.

[0109] In step S910, the control unit 103 causes the laser irradiator 105 to irradiate the diamond crystal 101 with laser light.

[0110] In step S911, the received light signal acquisition unit 1034 causes the imaging device 106 to acquire fluorescence having an intensity according to the selected amplitude. In step S912, the received light signal acquisition unit 1034 acquires and stores a received light signal SG1 (third received light signal) based on the acquired intensity.

[0111] In step S913, the electromagnetic wave supply control unit 1033 supplies a signal having a frequency that is the resonant frequency and a selected amplitude to the diamond crystal 101 in accordance with the second sequence. At this time, the laser irradiator 105 irradiates a laser in accordance with the laser supply sequence.

[0112] In step S914, the control unit 103 controls the laser irradiator 105 to irradiate the diamond crystal 101 with laser light.

[0113] In step S915, the light receiving signal acquisition unit 1034 causes the imaging device 106 to acquire fluorescence having an intensity according to the selected amplitude. In step S916, the light receiving signal acquisition unit 1034 acquires and stores a light receiving signal SG2 (fourth light receiving signal) based on the acquired intensity. Both the light receiving signal SG1 and the light receiving signal SG2 are light receiving signals (first light receiving signals) based on the intensity of fluorescence (first fluorescence) having an intensity (first intensity) according to the selected amplitude.

[0114] In step S917, the detection signal generating unit 1035 generates and stores a detection signal (first detection signal) corresponding to each pixel of the detection image generated by the image generating unit 1036, based on the light receiving signals SG1 and SG2. Specifically, the detection signal generating unit 1035 calculates the detection signal by calculating the difference between the light receiving signals SG1 and SG2 for each pixel.

[0115] Note that the processes from step S909 to step S917 may be repeated multiple times to reduce noise in the detection signal due to an error in the light reception signal.

[0116] In step S918, the detection signal generating unit 1035 determines whether storage of the detection signal has been completed for the frequency range to be detected, which is determined in accordance with the external electromagnetic field.

[0117] If the detection signal is not stored over the frequency range of the detection target, the process from step S908 is repeated. At this time, the electromagnetic wave supply control unit 1033 selects the amplitude of the magnetic field of the electromagnetic wave supplied to the diamond crystal 101 by the antenna unit 102 as a magnetic field having an amplitude larger than the amplitude of the magnetic field of the electromagnetic wave already supplied. This makes it possible to scan the amplitude, that is, to scan the frequency. The amplitude is, for example, an amplitude corresponding to the Rabi frequency from 10.2 MHz to 20.8 MHz.

[0118] By repeating the process from step S908, new light receiving signals SG1 and SG2 are repeatedly acquired as light receiving signals (second light receiving signals) based on the intensity of the fluorescence (second fluorescence) having an intensity (second intensity) according to the other selected amplitude. The detection signal generating unit 1035 generates and stores detection signals (second detection signals) corresponding to each pixel of the detection image generated by the image generating unit 1036 based on the new light receiving signals SG1 and SG2.

[0119] If detected signals have been stored over the frequency range of interest, the process ends.

[0120] 11 to 15, the generation process of the detected image will be described with examples of the detected image. Here, the description will be given on the assumption that all storage of the detected signals has been completed.

[0121] In step S1101, the image generating unit 1036 acquires a detection signal for each frequency in the frequency range of the detection target for a certain pixel in the detection range.

[0122] For example, as shown in the plan view of sample S in Fig. 12, wiring 206 with a width of 10 µm is provided on a substrate 205 with a size of 35 µm x 35 µm. The detection range of the detection device 10 is a range of 35 µm x 35 µm on the substrate 205. The detected image is an image having the pixels 803 described in Fig. 8.

[0123] In step S1102, the image generating unit 1036 calculates a peak frequency at which the acquired detection signal takes an extreme value.

[0124] For example, an example of detection signals at a pixel at multiple frequencies is shown in Figure 13. The detection signals are plotted with the horizontal axis representing frequency and the vertical axis representing normalized fluorescence intensity.

[0125] Each frequency in Fig. 13 is based on the amplitude of the magnetic field of the electromagnetic wave supplied to the diamond crystal 101 by the electromagnetic wave supply control unit 1033. The normalized fluorescence intensity when the magnetic field amplitude is amplitude A1, amplitude A2, and amplitude A3 (third amplitude) are respectively indicated by arrows in Fig. 13. The amplitude increases in the order of amplitude A1, amplitude A2, and amplitude A3, and the corresponding Rabi frequencies also increase in this order.

[0126] In Fig. 13, the detection signal has an extreme value when the amplitude A2, i.e., the second frequency, is 15 MHz. Therefore, the image generating unit 1036 calculates 15 MHz as the peak frequency (second frequency). This frequency corresponds to the frequency (15 MHz) of the RF signal supplied to the sample S by the signal generating unit 1032 in step S907 in Fig. 9. This is because the NV centers of the NV center layer 202, which are affected by the external electromagnetic field of 15 MHz, emit the strongest fluorescence when supplied with an electromagnetic wave having a magnetic field with the amplitude A2.

[0127] In this way, by taking the extreme value of the detection signal, the image generating section 1036 can calculate the frequency of the external electromagnetic field to be detected.

[0128] In step S1103, the image generating unit 1036 calculates a first frequency and a second frequency around the peak frequency based on the change in the slope of the detection signal. For example, the first frequency and the second frequency are respectively the frequency corresponding to the amplitude A1 and the amplitude A3 in FIG. 13, which are frequencies at which the absolute value of the slope of the detection signal becomes smaller than a predetermined value.

[0129] In step S1104, the image generating unit 1036 calculates a background signal based on the detection signal at the first frequency and the detection signal at the second frequency (third detection signal). Specifically, the image generating unit 1036 calculates an equation representing a straight line connecting a point indicating the normalized fluorescence intensity at the first frequency and a point indicating the normalized fluorescence intensity at the second frequency in FIG. 13. The image generating unit 1036 calculates the normalized fluorescence intensity when the frequency is set to the second frequency in the equation of the calculated straight line. The image generating unit 1036 regards this normalized fluorescence intensity as the background signal.

[0130] In step S1105, the image generating unit 1036 subtracts the background signal from the detection signal at the peak frequency.

[0131] In step S1106, the image generating unit 1036 stores the spin locking signal, which is the detection signal from which the background signal has been subtracted, in association with the pixel.

[0132] In step S1107, the image generating unit 1036 determines whether calculation of the spin locking signal has been completed for all pixels in the detection range.

[0133] If calculation of the spin locking signal has not been completed for all pixels in the detection range, the image generating unit 1036 repeats the processes from steps S1101 to S1106.

[0134] When calculation of the spin locking signals has been completed for all pixels in the detection range, in step S1108, the image generating unit 1036 generates a detection image based on the spin locking signals.

[0135] An example of the intensity of the spin locking signal at each pixel in the x direction at a certain y direction position is shown in Fig. 14. As shown in Fig. 14, the spin locking signal has a large value at a position corresponding to the end of the wiring 206 in Fig. 12 in the x direction. This means that at that position, the wiring 206 is emitting a strong external electromagnetic field, and that the frequency is 15 MHz.

[0136] Fig. 15 shows an example of a detection image 1501 generated by the image generating unit 1036. The spin locking signal as shown in Fig. 14 is calculated for each pixel in the y direction. Therefore, it is visualized that the spin locking signal has a large value at the position corresponding to the end of the wiring 206 in Fig. 12 in the x direction.

[0137] The detected image 1501 is an image obtained as a result of visualizing the electromagnetic waves emitted by the wiring 206 based on the spin locking signal. The detected image 1501 is obtained by scanning the Rabi frequency that excites the diamond crystal 101, thereby visualizing the electromagnetic waves emitted by the wiring 206.

[0138] The present embodiment has been described above. In the detection device 10, the spatial resolution is limited by the distance (about 10 nm) from the surface of the diamond crystal 101 to the NV center layer 202, and the spatial resolution can be significantly improved. In addition, the number of pixels of the detected image is not limited by the number of wirings. The inductance of the NV center is extremely small, and the influence of mutual interference between sensors and between the sensor and the target object can be avoided. Therefore, the detection device 10 can significantly improve the detection sensitivity of electromagnetic waves. By performing mathematical processing, the detection device 10 can be applied to visualization of dielectric constant changes regardless of whether the material is transparent or opaque, and technology for estimating and visualizing the current path and distribution of electronic circuits.

[0139] The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The elements of the embodiment, as well as their arrangement, materials, conditions, shapes, sizes, etc., are not limited to those exemplified, and may be modified as appropriate. [Explanation of symbols]

[0140] 10...detection device, 101...diamond crystal, 102...antenna unit, 204...antenna, 103...control unit, 104...pulse generator, 105...laser irradiator, 106...imaging device, 107...local oscillator, 108...arbitrary waveform generator, 109...mixer, 110...switch, 111...amplifier, 112...signal generator, S...sample, 201...diamond crystal layer, 202...NV center layer, 203, 205...substrate, 206...wiring, 1031...storage unit, 1032...signal generation unit, 1033...electromagnetic wave supply control unit, 1034...received light signal acquisition unit, 1035...detection signal generation unit, 1036...image generation unit

Claims

1. A diamond crystal having NV centers; an electromagnetic wave supply unit that supplies, in accordance with a predetermined supply sequence, to the diamond crystal, either a first electromagnetic wave having a magnetic field of a first amplitude or a second electromagnetic wave having a magnetic field of a second amplitude different from the first amplitude; a laser irradiation unit that irradiates the diamond crystal with a laser that excites the NV center; a light receiving unit having a light receiving element that receives a first fluorescence having a first intensity corresponding to the first amplitude of the first electromagnetic wave from the NV center excited by the laser and receives a second fluorescence having a second intensity corresponding to the second amplitude of the second electromagnetic wave from the NV center excited by the laser, and obtains a first light receiving signal based on the first fluorescence and a second light receiving signal based on the second fluorescence as light receiving signals; a detection signal generating unit that generates, as detection signals, a first detection signal based on the first light receiving signal and a second detection signal based on the second light receiving signal; and an image generating unit that generates a detection image showing the distribution of the intensity of the external electromagnetic field incident on the diamond crystal based on the first detection signal and the second detection signal.

2. 2. The detection device according to claim 1, the second amplitude is greater than the first amplitude; the electromagnetic wave supplying unit supplies any one of the first electromagnetic wave, the second electromagnetic wave, and a third electromagnetic wave having a magnetic field of a third amplitude greater than the second amplitude to the diamond crystal in accordance with the supply sequence; the light receiving unit receives a third fluorescence having a third intensity corresponding to the third amplitude of the third electromagnetic wave from the NV center excited by the laser, and obtains a third received light signal based on the third fluorescence as the received light signal; The detection signal generating unit generating a third detection signal based on a third light receiving signal as the detection signal; The image generating unit calculates a background signal based on the first detection signal and the third detection signal; The detection device generates the detection image based on a signal obtained by removing the background signal from the second detection signal.

3. 3. The detection device according to claim 1 or 2, the supply sequence includes a first supply sequence and a second supply sequence; The electromagnetic wave supply unit includes: In the first supply sequence, supplying the supply electromagnetic wave to the diamond crystal such that the spin state of the NV center is a first spin state; supplying to the diamond crystal an electromagnetic wave having a magnetic field oscillating in a first spin direction of the first spin state, the electromagnetic wave causing the spin state to become a second spin state; supplying to the diamond crystal the supply electromagnetic wave that causes the second spin state to become a third spin state; In the second supply sequence, supplying the supply electromagnetic wave to the diamond crystal such that the spin state is the first spin state; supplying to the diamond crystal an electromagnetic wave having a magnetic field oscillating in the first spin direction such that the spin state is the second spin state; supplying to the diamond crystal the supply electromagnetic wave that causes the second spin state to become a fourth spin state having a spin direction opposite to that of the third spin state; the light receiving unit acquires a third light receiving signal emitted from the NV center in the third spin state and a fourth light receiving signal emitted from the NV center in the fourth spin state; The detection device, wherein the detection signal generating section generates the detection signal based on a difference between the third light receiving signal and the fourth light receiving signal.

4. 4. The detection device according to claim 3, The electromagnetic wave supply unit includes: a detection device that supplies, in the second supply sequence, an electromagnetic wave having a phase that is 180 degrees different from a phase of the electromagnetic wave that sets the spin state to the third spin state in the first supply sequence, and sets the spin state to the fourth spin state.

5. A detection device according to any one of claims 1 to 4, A detection device, wherein the diamond crystal has a plurality of NV centers distributed within a surface of the diamond crystal and occupying a predetermined volume in the diamond crystal.

6. 1. An electromagnetic wave detection method, comprising: The detection device is supplying, according to a predetermined supply sequence, either a first electromagnetic wave having a magnetic field of a first amplitude or a second electromagnetic wave having a magnetic field of a second amplitude different from the first amplitude, to a diamond crystal having NV centres; irradiating the diamond crystal with a laser that excites the NV centers; receiving a first fluorescence having a first intensity corresponding to the first amplitude of the first electromagnetic wave from the NV center excited by the laser, and receiving a second fluorescence having a second intensity corresponding to the second amplitude of the second electromagnetic wave from the NV center excited by the laser; acquiring, as light receiving signals, a first light receiving signal based on the first fluorescence and a second light receiving signal based on the second fluorescence; generating, as detection signals, a first detection signal based on the first light receiving signal and a second detection signal based on the second light receiving signal; generating a detection image showing a distribution of the intensity of an external electromagnetic field incident on the diamond crystal based on the first detection signal and the second detection signal. Electromagnetic wave detection method.

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