Photoelectric conversion device, electromagnetic wave detection device, photoelectric conversion method, and electromagnetic wave detection method

Abstract

The photoelectric conversion device includes an electron emitting member. The electron emitting member has a metasurface that emits electrons in response to the incidence of electromagnetic waves. The metasurface includes a first antenna portion, a first bias portion, a second antenna portion, and a second bias portion. The first antenna portion extends in a first direction and emits electrons in response to the incidence of electromagnetic waves. The first bias portion faces the first antenna portion and is configured to generate an electric field having a component in the first direction between the first antenna portion and the first antenna portion. The second antenna portion extends in a second direction intersecting the first direction and emits electrons in response to the incidence of electromagnetic waves. The second bias portion faces the second antenna portion and is configured to generate an electric field having a component in the second direction between the second antenna portion and the second antenna portion.

Description

Technical Field

[0001] One aspect of the present disclosure relates to a photoelectric conversion device, an electromagnetic wave detection device, a photoelectric conversion method, and an electromagnetic wave detection method.

Background Art

[0002] For electron emission, there are, for example, four types of emission: thermionic emission, photoelectron emission, secondary emission, and electric field field emission. Thermionic emission is caused by heating an electrode. Photoelectron emission is caused by irradiation with photons. Secondary emission is caused by the collision of light-speed electrons. Field emission occurs in the presence of an electrostatic field. US 2016 / 0216201 discloses an electromagnetic wave detection system for detecting electromagnetic waves. This system includes a photoelectric conversion device that converts electromagnetic waves into electrons. The photoelectric conversion device includes an electron emission member having a metamaterial structure. This system detects electromagnetic waves incident on the electron emission member.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The electron emission member of the photoelectric conversion device emits electrons in response to the incidence of electromagnetic waves. The system detects the incident electromagnetic waves based on the electrons emitted from the electron emission member. According to the system, for example, terahertz waves can be detected.

[0005] Incidentally, there is a demand for detecting the polarization state of incident electromagnetic waves. One possible method for detecting the polarization state is to use an optical system that combines a polarizer and a detector. For example, an optical system that combines a wire grid and a detector is used. However, when using such an optical system, the structure of the device is complex, and the cost of detecting the polarization state is also high. [Means for solving the problem]

[0006] One aspect of this disclosure aims to provide a photoelectric conversion device that can easily detect the polarization state of electromagnetic waves. Another aspect of this disclosure aims to provide an electromagnetic wave detection device that can easily detect the polarization state of electromagnetic waves. Yet another aspect of this disclosure aims to provide a photoelectric conversion method that can easily detect the polarization state of electromagnetic waves. Yet another aspect of this disclosure aims to provide an electromagnetic wave detection method that can easily detect the polarization state of electromagnetic waves.

[0007] A photoelectric converter in one aspect of this disclosure includes an electron-emitting member. The electron-emitting member has a metasurface that emits electrons in response to the incidence of electromagnetic waves. The metasurface includes a first antenna portion, a first bias portion, a second antenna portion, and a second bias portion. The first antenna portion extends in a first direction and emits electrons in response to the incidence of electromagnetic waves. The first bias portion faces the first antenna portion and is configured to generate an electric field having a component in the first direction between itself and the first antenna portion. The second antenna portion extends in a second direction intersecting the first direction and emits electrons in response to the incidence of electromagnetic waves. The second bias portion faces the second antenna portion and is configured to generate an electric field having a component in the second direction between itself and the second antenna portion.

[0008] In this photoelectric converter, the first antenna section and the second antenna section extend in first and second directions, intersecting each other. The first bias section is configured to generate an electric field having a component in the first direction between the first bias section and the first antenna section. The second bias section is configured to generate an electric field having a component in the second direction between the second bias section and the second antenna section. With this configuration, the first antenna section emits electrons according to the component of the electric field strength of the incident electromagnetic wave in the first direction. The second antenna section emits electrons according to the component of the electric field strength of the incident electromagnetic wave in the second direction. Therefore, electrons emitted according to the component of the electric field strength of the incident electromagnetic wave in the first direction and electrons emitted according to the component of the electric field strength of the incident electromagnetic wave in the second direction can be detected. By detecting these, the polarization state of the electromagnetic wave can be easily detected.

[0009] In one aspect of the above, the photoelectric conversion device may further include a potential control unit that controls the potential applied to the metasurface. The potential control unit may switch between the first state and the second state, and between the third state and the fourth state, by controlling the potential applied to the metasurface. In the first state, the component of the electric field from the first bias unit toward the first antenna unit in the first direction may be positive. In the second state, the component of the electric field from the first bias unit toward the first antenna unit in the first direction may be negative. In the third state, the component of the electric field from the second bias unit toward the second antenna unit in the second direction may be positive. In the fourth state, the component of the electric field from the second bias unit toward the second antenna unit in the second direction may be negative. In this case, when an electromagnetic wave is incident on the metasurface in the first state, electrons are emitted from the first antenna unit in accordance with the positive component of the electric field strength of the incident electromagnetic wave in the first direction. When an electromagnetic wave is incident on the metasurface in the second state, electrons are emitted from the first antenna unit in accordance with the negative component of the electric field strength of the incident electromagnetic wave in the first direction. In the third state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section according to the positive component of the electric field strength of the incident electromagnetic waves in the second direction. In the fourth state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section according to the negative component of the electric field strength of the incident electromagnetic waves in the second direction. Therefore, this photoelectric conversion device can measure the electric field strength of electromagnetic waves incident on the electron-emitting member for each polarity in both the first and second directions by detecting electrons emitted from the metasurface in each state. As a result, the detection of the polarization state of electromagnetic waves can be achieved more accurately.

[0010] In one aspect of the above, the first antenna section may include first and second tips positioned at different locations in the first direction. The first bias section may include a first part and a second part. The first part may face the first tip and generate an electric field having a component in the first direction between it and the first tip. The second part may face the second tip and generate an electric field having a component in the first direction between it and the second tip. The second antenna section may include third and fourth tips positioned at different locations in the second direction. The second bias section may include a third part and a fourth part. The third part may face the third tip and generate an electric field having a component in the second direction between it and the third tip. The fourth part may face the fourth tip and generate an electric field having a component in the second direction between it and the fourth tip. In the first direction, the second part, second tip, first tip, and first part may be arranged in this order. In the second direction, the fourth part, fourth tip, third tip, and third part may be arranged in this order. In this case, despite the simple configuration, the detection of electrons emitted from the metasurface makes it possible to measure the electric field strength of electromagnetic waves incident on the electron-emitting member for each polarity in both the first and second directions.

[0011] In one aspect of the above, the system may further include a potential control unit that controls the potential applied to the metasurface. The potential control unit may switch between the first state and the second state, and between the third state and the fourth state, by controlling the potential applied to the metasurface. In the first state, the component of the electric field from the first tip toward the first part in the first direction may be positive, the component of the electric field from the second part toward the second tip in the first direction may be positive, the component of the electric field from the third tip toward the third part in the second direction may be positive, and the component of the electric field from the fourth tip toward the fourth part in the second direction may be negative. In the second state, the component of the electric field from the first part toward the first tip in the first direction may be negative, the component of the electric field from the second tip toward the second part in the first direction may be negative, the component of the electric field from the third tip toward the third part in the second direction may be positive, and the component of the electric field from the fourth tip toward the fourth part in the second direction may be negative. In the third state, the component of the electric field from the first tip toward the first part in the first direction may be positive, the component of the electric field from the second tip toward the second part in the first direction may be negative, the component of the electric field from the third tip toward the third part in the second direction may be positive, and the component of the electric field from the fourth part toward the fourth tip in the second direction may be positive. In the fourth state, the component of the electric field from the first tip toward the first part in the first direction may be positive, the component of the electric field from the second tip toward the second part in the first direction may be negative, the component of the electric field from the third part toward the third tip in the second direction may be negative, and the component of the electric field from the fourth tip toward the fourth part in the second direction may be negative. In this case, when electromagnetic waves are incident on the metasurface in the first state, electrons are emitted from the first antenna section in accordance with the positive component of the electric field strength of the incident electromagnetic wave in the first direction, and the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic wave is suppressed. In the second state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the first antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic waves in the first direction, while the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic waves is suppressed.In the third state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the positive component of the electric field strength of the incident electromagnetic waves in the second direction, while the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic waves is suppressed. In the fourth state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic waves in the second direction, while the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic waves is suppressed.

[0012] In one aspect of the above, the system may further include a potential control unit that controls the potential applied to the metasurface. The potential control unit may switch between a first state and a second state, and between a third state and a fourth state, by controlling the potential applied to the metasurface. In the first state, the potential applied to the first part may be lower than the potential applied to the first antenna part, the potential applied to the second part may be higher than the potential applied to the first antenna part, the potential applied to the third part may be lower than the potential applied to the second antenna part, and the potential applied to the fourth part may be lower than the potential applied to the second antenna part. In the second state, the potential applied to the first part may be higher than the potential applied to the first antenna part, the potential applied to the second part may be lower than the potential applied to the first antenna part, the potential applied to the third part may be lower than the potential applied to the second antenna part, and the potential applied to the fourth part may be lower than the potential applied to the second antenna part. In the third state, the potential applied to the first part may be lower than the potential applied to the first antenna part, the potential applied to the second part may be lower than the potential applied to the first antenna part, the potential applied to the third part may be lower than the potential applied to the second antenna part, and the potential applied to the fourth part may be higher than the potential applied to the second antenna part. In the fourth state, the potential applied to the first part may be lower than the potential applied to the first antenna part, the potential applied to the second part may be lower than the potential applied to the first antenna part, the potential applied to the third part may be higher than the potential applied to the second antenna part, and the potential applied to the fourth part may be lower than the potential applied to the second antenna part. In this case, potential differences are generated between the first tip and the first part, between the second tip and the second part, between the third tip and the third part, and between the fourth tip and the fourth part. An electric field is generated by the potential difference. As a result, when electromagnetic waves are incident on the metasurface in the first state, electrons are emitted from the first antenna part according to the positive component of the electric field strength of the incident electromagnetic wave in the first direction, and the emission of electrons according to other components of the electric field strength of the incident electromagnetic wave is suppressed.In the second state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the first antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic wave in the first direction, while the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic wave is suppressed. In the third state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the positive component of the electric field strength of the incident electromagnetic wave in the second direction, while the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic wave is suppressed. In the fourth state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic wave in the second direction, while the emission of electrons in accordance with other components of the electric field strength of the incident electromagnetic wave is suppressed.

[0013] In the above aspect, the first and second directions may be orthogonal. The metasurface may further include a third antenna section and a third bias section. The third antenna section extends in a third direction intersecting the first and second directions and may emit electrons in response to the incidence of electromagnetic waves. The third bias section faces the third antenna section and may be configured to generate an electric field having a third-direction component between itself and the third antenna section. With such a configuration, the third antenna section emits electrons in response to the third-direction component of the electric field strength of the incident electromagnetic wave. In this case, the electrons emitted in response to the third-direction component of the electric field strength of the incident electromagnetic wave can be further detected. Therefore, by detecting electrons emitted from the metasurface, the polarization state of the incident electromagnetic wave, including circular polarization, can be detected by simple calculation processing.

[0014] In one aspect of the above, the system may further include a potential control unit that controls the potential applied to the metasurface. The potential control unit may switch between the first and second states, the third and fourth states, and the fifth and sixth states by controlling the potential applied to the metasurface. In the first state, the component of the electric field from the first bias unit toward the first antenna unit in the first direction may be positive. In the second state, the component of the electric field from the first bias unit toward the first antenna unit in the first direction may be negative. In the third state, the component of the electric field from the second bias unit toward the second antenna unit in the second direction may be positive. In the fourth state, the component of the electric field from the second bias unit toward the second antenna unit in the second direction may be negative. In the fifth state, the component of the electric field from the third bias unit toward the third antenna unit in the third direction may be negative. In the sixth state, the component of the electric field from the third bias unit toward the third antenna unit in the third direction may be positive. In this case, when electromagnetic waves are incident on the metasurface in the first state, electrons are emitted from the first antenna unit according to the positive component of the electric field strength of the incident electromagnetic waves in the first direction. In the second state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the first antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic waves in the first direction. In the third state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the positive component of the electric field strength of the incident electromagnetic waves in the second direction. In the fourth state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic waves in the second direction. In the fifth state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the negative component of the electric field strength of the incident electromagnetic waves in the third direction. In the sixth state, when electromagnetic waves are incident on the metasurface, electrons are emitted from the second antenna section in accordance with the positive component of the electric field strength of the incident electromagnetic waves in the third direction. Therefore, by detecting the electrons emitted from the metasurface in each state, this photoelectric conversion device can measure the electric field strength of electromagnetic waves incident on the electron-emitting member for each polarity in the first, second, and third directions.

[0015] In one aspect of the above, the photoelectric converter may further include a housing that is hermetically sealed and has a window portion that allows electromagnetic waves to pass through. The electron emission member may be placed inside the housing. In this case, the amount of electrons emitted in response to the incidence of electromagnetic waves can be improved by creating a vacuum inside the housing or filling the housing with gas.

[0016] An electromagnetic wave detection device in another aspect of this disclosure comprises the photoelectric conversion device described above, a detection unit, and a calculation unit. The detection unit detects electrons emitted from an electron-emitting member. The calculation unit calculates the polarization information of the electromagnetic wave based on the detection result of the detection unit in the first state, the detection result of the detection unit in the second state, the detection result of the detection unit in the third state, and the detection result of the detection unit in the fourth state. In this case, the electromagnetic wave detection device can easily detect the polarization state of the electromagnetic wave.

[0017] A photoelectric conversion method in yet another aspect of the present disclosure comprises the steps of: using a metasurface including a first antenna section, a first bias section, a second antenna section, and a second bias section, emitting electrons from the first antenna section in a state in which an electric field having a first directional component is generated between the first bias section and the first antenna section in response to the incidence of an electromagnetic wave to be measured onto the metasurface; and using the metasurface, emitting electrons from the second antenna section in a state in which an electric field having a second directional component is generated between the second bias section and the second antenna section in response to the incidence of an electromagnetic wave to be measured onto the metasurface. The first antenna section extends in the first direction. The first bias section faces the first antenna section. The second antenna section extends in a second direction intersecting the first direction. The second bias section faces the second antenna section.

[0018] In this photoelectric conversion method, when an electromagnetic wave to be measured is incident on the metasurface while an electric field having a component in the first direction is generated between the first bias unit and the first antenna unit, electrons are emitted from the first antenna unit. When an electromagnetic wave to be measured is incident on the metasurface while an electric field having a component in the second direction is generated between the second bias unit and the second antenna unit, electrons are emitted from the second antenna unit. In this case, the first antenna unit emits electrons according to the component of the electric field strength of the incident electromagnetic wave in the first direction. The second antenna unit emits electrons according to the component of the electric field strength of the incident electromagnetic wave in the second direction. Therefore, electrons emitted according to the component of the electric field strength of the incident electromagnetic wave in the first direction and electrons emitted according to the component of the electric field strength of the incident electromagnetic wave in the second direction can be detected. Through these detections, the polarization state of the electromagnetic wave can be easily detected.

[0019] In yet another aspect of the above, the step of emitting electrons from the first antenna section may include a first electron emission step and a second electron emission step. In the first electron emission step, in the first state, electrons may be emitted from the first antenna section in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the first state, a potential may be applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is positive. In the second electron emission step, in the second state, electrons may be emitted from the first antenna section in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the second state, a potential may be applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is negative. The step of emitting electrons from the second antenna section may include a third electron emission step and a fourth electron emission step. In the third electron emission step, in the third state, electrons may be emitted from the second antenna section in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the third state, a potential may be applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is positive. The fourth electron emission step may cause electrons to be emitted from the second antenna section in the fourth state in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the fourth state, a potential may be applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is negative. In this case, in the first state, the component of the electric field from the first bias section toward the first antenna section in the first direction is positive. Therefore, when an electromagnetic wave is incident on the metasurface in the first state, electrons corresponding to the positive component of the electric field strength of the incident electromagnetic wave in the first direction are emitted from the first antenna section. In the second state, the component of the electric field from the first bias section toward the first antenna section in the first direction is negative. Therefore, when an electromagnetic wave is incident on the metasurface in the second state, electrons corresponding to the negative component of the electric field strength of the incident electromagnetic wave in the first direction are emitted from the first antenna section. In the third state, the component of the electric field from the second bias section toward the second antenna section in the second direction is positive.Therefore, when electromagnetic waves are incident on the metasurface in the third state, electrons corresponding to the positive component of the electric field strength of the incident electromagnetic waves in the second direction are emitted from the second antenna section. In the fourth state, the component of the electric field from the second bias section toward the second antenna section in the second direction is negative. Therefore, when electromagnetic waves are incident on the metasurface in the fourth state, electrons corresponding to the negative component of the electric field strength of the incident electromagnetic waves in the second direction are emitted from the second antenna section. Thus, with this photoelectric conversion method, by detecting the electrons emitted from the metasurface in each state, it is possible to measure the electric field strength of the electromagnetic waves incident on the electron-emitting member for each polarity in the first and second directions.

[0020] In yet another aspect of the above, the first and second directions may be orthogonal. The metasurface may further include a third antenna section and a third bias section. The third antenna section may extend in a third direction intersecting the first and second directions. The third bias section may face the third antenna section. This photoelectric conversion method may further include a step of emitting electrons from the third antenna section in response to the incidence of an electromagnetic wave to be measured onto the metasurface. In this case, the third antenna section emits electrons in accordance with the component of the electric field strength of the incident electromagnetic wave in the third direction. Therefore, electrons emitted in accordance with the component of the electric field strength of the incident electromagnetic wave in the third direction can be detected. Thus, by detecting electrons emitted from the metasurface, the polarization state of the incident electromagnetic wave, including circular polarization, can be detected by simple calculation processing.

[0021] In yet another aspect of the above, the step of emitting electrons from the first antenna section may include a first electron emission step and a second electron emission step. In the first electron emission step, in the first state, electrons may be emitted from the first antenna section in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the first state, a potential may be applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is positive. In the second electron emission step, in the second state, electrons may be emitted from the first antenna section in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the second state, a potential may be applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is negative. The step of emitting electrons from the second antenna section may include a third electron emission step and a fourth electron emission step. In the third electron emission step, in the third state, electrons may be emitted from the second antenna section in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the third state, a potential may be applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is positive. The fourth electron emission step may cause electrons to be emitted from the second antenna section in the fourth state in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the fourth state, a potential may be applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is negative. The step of emitting electrons from the third antenna section may include a fifth electron emission step and a sixth electron emission step. The fifth electron emission step may cause electrons to be emitted from the third antenna section in the fifth state in response to the incidence of the electromagnetic wave to be measured onto the metasurface. In the fifth state, a potential may be applied to the metasurface such that the component of the electric field from the third bias section toward the third antenna section in the third direction is negative. The sixth electron emission step may cause electrons to be emitted from the third antenna section in the sixth state in response to the incidence of the electromagnetic wave to be measured onto the metasurface.In the sixth state, a potential may be applied to the metasurface such that the component of the electric field in the third direction from the third bias section to the third antenna section is positive. In this case, when electromagnetic waves are incident on the metasurface in the fifth state, electrons corresponding to the positive component in the third direction of the electric field strength of the incident electromagnetic waves are emitted from the second antenna section. When electromagnetic waves are incident on the metasurface in the sixth state, electrons corresponding to the negative component in the third direction of the electric field strength of the incident electromagnetic waves are emitted from the second antenna section. Therefore, by detecting the electrons emitted from the metasurface in each state, it is possible to measure the electric field strength of the electromagnetic waves incident on the electron-emitting member for each polarity in the first, second, and third directions.

[0022] An electromagnetic wave detection method in yet another aspect of this disclosure comprises the photoelectric conversion method described above, and further comprises a first detection step, a second detection step, a third detection step, a fourth detection step, and a calculation step. In the first detection step, electrons emitted from the electron-emitting member in the first electron emission step are detected. In the second detection step, electrons emitted from the electron-emitting member in the second electron emission step are detected. In the third detection step, electrons emitted from the electron-emitting member in the third electron emission step are detected. In the fourth detection step, electrons emitted from the electron-emitting member in the fourth electron emission step are detected. In the calculation step, polarization information of the electromagnetic wave is calculated based on the detection results of the first detection step, the second detection step, the third detection step, and the fourth detection step. In this case, the polarization state of the electromagnetic wave can be easily detected.

[0023] According to one aspect of the present disclosure, it is possible to provide a photoelectric conversion device capable of easily detecting the polarization state of an electromagnetic wave. According to another aspect of the present disclosure, it is possible to provide an electromagnetic wave detection device capable of easily detecting the polarization state of an electromagnetic wave. According to still another aspect of the present disclosure, it is possible to provide a photoelectric conversion method capable of easily detecting the polarization state of an electromagnetic wave. According to still another aspect of the present disclosure, it is possible to provide an electromagnetic wave detection method capable of easily detecting the polarization state of an electromagnetic wave.

Brief Description of the Drawings

[0024] [Figure 1] FIG. 1 is a schematic diagram of an electromagnetic wave detection device in the present embodiment. [Figure 2] FIG. 2 is a schematic diagram of a photoelectric conversion device. [Figure 3] FIG. 3 is a plan view of an electron-emitting member. [Figure 4] (a) is a diagram for explaining the operation of the photoelectric conversion device. (b) is a diagram for explaining the operation of the photoelectric conversion device. [Figure 5] FIG. 5 is a diagram for explaining the operation of the photoelectric conversion device. [Figure 6] FIG. 6 is a diagram for explaining the operation of the photoelectric conversion device. [Figure 7] (a) is a diagram for explaining the operation of the photoelectric conversion device. (b) is a diagram for explaining the operation of the photoelectric conversion device. [Figure 8] FIG. 8 is a plan view of an electron-emitting member in a modification of the present embodiment. [Figure 9] FIG. 9 is a plan view of an electron-emitting member in a modification of the present embodiment. [Figure 10] (a) is a diagram showing the structure of a pattern in a modification of the present embodiment. (b) is a diagram showing the structure of a pattern in a modification of the present embodiment. [Figure 11] FIG. 11 is a flowchart of an electromagnetic wave detection method. [Figure 12] FIG. 12 is a flowchart of an electromagnetic wave detection method. [Figure 13] Figure 13 is a diagram illustrating the calculation process in a modified example of this embodiment. [Modes for carrying out the invention]

[0025] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the following description, the same or equivalent elements will be denoted by the same reference numerals, and redundant descriptions will be omitted.

[0026] First, the configuration of the electromagnetic wave detection device in this embodiment will be described with reference to Figure 1. Figure 1 is a schematic diagram of the electromagnetic wave detection device in this embodiment.

[0027] The electromagnetic wave detection device 1 detects incident electromagnetic waves. The electromagnetic wave detection device 1 includes a photoelectric converter 2. The photoelectric converter 2 emits electrons in response to the incidence of electromagnetic waves. In this specification, "light" includes electromagnetic waves other than visible light. In this embodiment, the electromagnetic wave detection device 1 detects incident electromagnetic waves based on electrons emitted from the photoelectric converter 2 in response to the incidence of electromagnetic waves. The photoelectric converter 2 emits electrons when electromagnetic waves in the wavelength range from so-called millimeter waves to infrared light are incident on it. The wavelength range from millimeter waves to infrared light corresponds to a frequency range of approximately 0.01 to 150 THz, for example. In this specification, "wavelength range" may include a range of multiple wavelength ranges that are separated from each other, or it may be a range of a single continuous wavelength range. The photoelectric converter 2 emits electrons by field emission, for example.

[0028] The electromagnetic wave detection device 1 is, for example, an electron tube that outputs an electrical signal in response to the incidence of electromagnetic waves. For example, the electromagnetic wave detection device 1 emits electrons inside the electron tube in response to the incidence of electromagnetic waves, detects the emitted electrons, and outputs an electrical signal based on the detection result. The electron tube is, for example, a photomultiplier tube (PMT). The electromagnetic wave detection device 1 emits electrons inside when electromagnetic waves are incident and multiplies the emitted electrons. As a modification of this embodiment, the electromagnetic wave detection device 1 does not have a configuration to detect electrons inside the electron tube. In other words, the electromagnetic wave detection device 1 may include an electron tube that emits electrons to the outside in response to the incidence of electromagnetic waves as a photoelectric converter 2, and may have a detection unit outside this electron tube that detects the electrons emitted from the electron tube.

[0029] The electromagnetic wave detection device 1 comprises a housing 10, an electron emission member 20, a holding member 30, an electron multiplication unit 40, an electron collection unit 50, a power supply unit 70, and a calculation unit 75. The electron emission member 20, the holding member 30, the electron multiplication unit 40, and the electron collection unit 50 are arranged inside the housing 10. The photoelectric conversion device 2 comprises the housing 10, the electron emission member 20, and the power supply unit 70, and constitutes a part of the electromagnetic wave detection device 1.

[0030] The housing 10 has a valve 11 and a stem 12. The inside of the housing 10 is hermetically sealed by the valve 11 and the stem 12. In this embodiment, the inside of the housing 10 is kept under vacuum. The vacuum inside the housing 10 does not have to be an absolute vacuum, and may be a state in which it is filled with a gas at a pressure lower than atmospheric pressure. For example, the inside of the housing 10 is 1 × 10⁻¹⁰ -4 ~1 × 10 -7 It is held in Pa.

[0031] The valve 11 includes an electromagnetic wave-transmitting window 11a. In this specification, "electromagnetic wave-transmitting" means the property of transmitting at least a portion of the wavelength range of incident electromagnetic waves. In this embodiment, the housing 10 has a cylindrical shape. The housing 10 extends in the X-axis direction as shown in Figure 1. The stem 12 constitutes the bottom surface of the housing 10. The stem 12 constitutes, for example, one end surface of the housing 10 in the X-axis direction. The valve 11 constitutes the side surface of the housing 10 and the bottom surface facing the stem 12. The X, Y, and Z axes are orthogonal to each other.

[0032] The window portion 11a forms the bottom surface facing the stem 12. The window portion 11a has a circular shape, for example, when viewed from the X-axis direction, with the YZ-axis direction being the radial direction. The frequency characteristics of electromagnetic wave transmittance differ depending on the material. Therefore, the window portion 11a is made of an optimal material according to the frequency range of electromagnetic waves incident on the housing 10. For example, the window portion 11a includes at least one selected from, for example, quartz, silicon, germanium, sapphire, zinc selenide, zinc sulfide, magnesium fluoride, lithium fluoride, barium fluoride, calcium fluoride, magnesium oxide, calcium carbonate, diamond, and chalcogenide glass. This allows electromagnetic waves in any frequency range from millimeter waves to infrared light to be guided into the interior of the housing 10. For example, quartz is suitable for materials that transmit electromagnetic waves in the frequency range of 0.1 to 5 THz, silicon for 0.04 to 11 THz and above 46 THz, magnesium fluoride for above 40 THz, germanium for above 13 THz, and zinc selenide for above 14 THz.

[0033] The housing 10 further has a plurality of wires 13 that enable electrical connections between the outside and inside of the housing 10. The plurality of wires 13 are, for example, lead wires or pins. In this embodiment, the plurality of wires 13 are pins that pass through the stem 12 and extend from the inside to the outside of the housing 10. At least one of the plurality of wires 13 is connected to various components provided inside the housing 10.

[0034] The electron-emitting member 20 emits electrons in response to the incidence of electromagnetic waves. The electron-emitting member 20 includes a support 21. The support 21 is, for example, plate-shaped. The support 21 is, for example, rectangular in plan view. The support 21 has two opposing main surfaces 21a and 21b. The main surfaces 21a and 21b are surfaces of the support 21 located on opposite sides of each other. The main surfaces 21a and 21b are, for example, flat surfaces and are rectangular in plan view. The main surfaces 21a and 21b are arranged parallel to the window portion 11a. The main surface 21a faces the window portion 11a. Electromagnetic waves that have passed through the window portion 11a are incident on the main surface 21a.

[0035] The support 21 is electromagnetically transparent to electromagnetic waves that pass through the window 11a. Therefore, the support 21 transmits at least a portion of the frequency range of the electromagnetic waves that have passed through the window 11a. The support 21 may be made of the same material as the window 11a. The material of the support 21 may include, for example, silicon. In a single photoelectric converter 2, the support 21 and the window 11a do not have to be made of the same material. The support 21 is spaced apart from the window 11a and the electron multiplier 40.

[0036] The electron-emitting member 20 has a metasurface 22. The metasurface 22 is provided on the support 21. The metasurface 22 emits electrons in response to the incidence of electromagnetic waves. The metasurface 22 is sensitive to electromagnetic waves in the wavelength range from so-called millimeter waves to infrared light. The metasurface 22 is also sensitive to terahertz waves. The wavelength range of terahertz waves corresponds to a frequency range from 100 GHz to 30 THz. "Sensitive to electromagnetic waves" means that electrons are emitted in response to the incidence of these electromagnetic waves.

[0037] The metasurface 22 includes, for example, an oxide layer formed on the main surface 21b of the support 21 and a metal layer formed on the oxide layer. The material of the oxide layer includes, for example, silicon dioxide and titanium oxide. For example, the oxide layer includes a layer containing silicon dioxide and a layer containing titanium oxide. The material of the metal layer includes, for example, gold. In this embodiment, an oxide layer is formed on the main surface 21b of a support 21 made of quartz, and a metal layer is formed on the oxide layer. For example, the thickness of the support 21 is 525 μm, the thickness of the silicon dioxide layer of the metasurface 22 is 1 μm, the thickness of the titanium dioxide layer of the metasurface 22 is 10 nm, and the thickness of the metal layer of the metasurface 22 is 200 nm. The metasurface 22 is rectangular in plan view. In a modified example of this embodiment, the metasurface 22 may be provided on the main surface 21a.

[0038] The retaining member 30 holds the electron-emitting member 20 inside the housing 10. The retaining member 30 is positioned relative to the inner surface 10a of the housing 10. The retaining member 30 positions the electron-emitting member 20 relative to the housing 10. The retaining member 30 is frame-shaped along the inner surface 10a of the housing 10, and a through-hole is formed in the retaining member 30. When viewed from a direction perpendicular to the main surfaces 21a and 21b of the electron-emitting member 20, the metasurface 22 of the electron-emitting member 20 is positioned inside the edge defining the through-hole.

[0039] The electron multiplier unit 40 is located inside the housing 10 and has an incident surface 40a into which electrons emitted from the electron emission member 20 are incident. The electron multiplier unit 40 multiplies the electrons incident on the incident surface 40a. In this embodiment, the main surface 21b of the electron emission member 20 faces the incident surface 40a of the electron multiplier unit 40. The metasurface 22 faces the incident surface 40a of the electron multiplier unit 40, and electrons emitted from the metasurface 22 are incident on the incident surface 40a. The main surface 21a of the electron emission member 20 faces the window portion 11a of the housing 10. The electron multiplier unit 40 has, for example, multiple stages of dynodes.

[0040] The electron collection unit 50 is located inside the housing 10 and collects electrons multiplied by the electron multiplier unit 40. The electron collection unit 50 is a detection unit that detects electrons emitted from the electron emission member 20. The electromagnetic wave detection device 1 detects electromagnetic waves by detecting electrons in the electron collection unit 50. In this embodiment, the electron collection unit 50 has, for example, an anode to which one of the plurality of wires 13 is connected. A predetermined potential is applied to the anode through the wire 13. The anode captures electrons multiplied by the dynode of the electron multiplier unit 40. The electron collection unit 50 may have a diode instead of an anode.

[0041] In this embodiment, the metasurface 22 is of the active type and operates by the application of a bias voltage. The metasurface 22 operates by being supplied with a potential by the power supply unit 70. The power supply unit 70 is electrically connected to the metasurface 22. The power supply unit 70 includes a potential supply unit 71 and a potential control unit 72. The potential supply unit 71 supplies a potential to the metasurface 22. The potential control unit 72 controls the potential supply unit 71. The potential supplied to the metasurface 22 is controlled by the potential control unit 72. The metasurface 22 operates according to the potential controlled by the potential control unit 72. In other words, the metasurface 22 emits electrons in response to the potential control by the potential control unit 72.

[0042] The calculation unit 75 acquires the detection results from the electron collection unit 50 and calculates information regarding the electric field strength of the electromagnetic wave based on these detection results. For example, the calculation unit 75 acquires an electrical signal based on electrons collected by the electron collection unit 50 as the detection result. The information regarding the electric field strength of the electromagnetic wave to be calculated may be the electric field strength itself. The calculation unit 75 calculates the polarization information of the electromagnetic wave based on the information regarding the electric field strength of the electromagnetic wave. "Polarization information" is information regarding the "polarization state". For example, the calculation unit 75 calculates the polarization direction of linearly polarized light. For example, the calculation unit 75 outputs the calculated electric field strength information and polarization information to a display unit (not shown) for display.

[0043] The potential control unit 72 and the arithmetic unit 75 are, for example, one or more computers composed of hardware and software such as programs. The potential control unit 72 and the arithmetic unit 75 include, for example, a processor, main memory, auxiliary storage, a communication device, and an input device as hardware. The processor executes an operating system and application programs. The main memory consists of ROM (Read Only Memory) and RAM (Random Access Memory). The auxiliary storage is a storage medium consisting of a hard disk and flash memory, etc. Auxiliary storage generally stores a larger amount of data than main memory. The communication device consists of a network card or a wireless communication module. The input device consists of a keyboard, mouse, and touch panel, etc. The potential control unit 72 and the arithmetic unit 75 may be configured as a single unit or as separate units. [Configuration of the photoelectric converter]

[0044] Next, the photoelectric converter 2 will be described in more detail with reference to Figures 2 and 3. Figure 2 is a schematic diagram of the photoelectric converter. Figure 3 is a plan view of the electron-emitting member in the photoelectric converter.

[0045] In the example shown in Figure 2, an electromagnetic wave W incident on the housing 10 is incident on the metasurface 22, and the metasurface 22 emits electrons P in response to the incidence of the electromagnetic wave W. The electric field strength of the electromagnetic wave W includes, for example, a Y-axis component and a Z-axis component. The electrons P emitted from the metasurface 22 are incident on the electron multiplication unit 40. The electrons multiplied in the electron multiplication unit 40 are collected in the electron collection unit 50. For example, if the Z-axis direction corresponds to the first direction, the Y-axis direction corresponds to the second direction.

[0046] As shown in Figure 3, the metasurface 22 includes at least one photoelectric conversion unit 25. The photoelectric conversion unit 25 emits electrons P in response to the incidence of an electromagnetic wave W having a corresponding wavelength. For example, the photoelectric conversion unit 25 is sensitive to a frequency range centered at 0.5 THz. For example, the photoelectric conversion unit 25 is sensitive to the Y-axis and Z-axis components of the electric field strength of the electromagnetic wave W. The cases in which the photoelectric conversion unit 25 is sensitive to a positive Y-axis component, a negative Y-axis component, a positive Z-axis component, and a negative Z-axis component are switched according to the potential control by the potential control unit 72. The directional components and frequency ranges of the electric field to which the photoelectric conversion unit 25 is sensitive are not limited to these.

[0047] As shown in Figure 3, the metasurface 22 includes multiple spaced patterns 31, 32, 33, 34, and 35. The directional components and frequency range of the electric field to which the photoelectric conversion unit 25 is sensitive depend on the configuration of the multiple patterns 31, 32, 33, 34, and 35. "Configuration" includes various attributes such as shape and material. "Shape" also includes size. Patterns 31 and 32 each include a bias section β1. Patterns 33 and 34 each include a bias section β2. Pattern 35 includes antenna sections α1 and α2. In each of the antenna sections α1 and α2, the smaller the size of the antenna sections α1 and α2, the more likely field electron emission is to occur for electromagnetic waves with shorter wavelengths, i.e., electromagnetic waves with higher frequencies. Antenna sections α1 and α2 are sensitive to different directional components. Antenna section α1 is sensitive to the Z-axis component. Antenna section α2 is sensitive to the Y-axis component. For example, if antenna section α1 corresponds to the first antenna section, then antenna section α2 corresponds to the second antenna section. If bias section β1 corresponds to the first bias section, then bias section β2 corresponds to the second bias section.

[0048] Antenna sections α1 and α2 emit electrons P in response to the incidence of electromagnetic waves W. Antenna section α1 extends in the Z-axis direction. Bias section β1 faces antenna section α1. When a bias potential is applied to bias section β1, bias section β1 is configured to generate an electric field with a component in the Z-axis direction between it and the corresponding antenna section α1. In this embodiment, bias section β1 generates an electric field in the Z-axis direction between it and antenna section α1. When a higher potential than that of antenna section α1 is applied to bias section β1, the potential barrier at the tip portion of antenna section α1 on the bias section β1 side becomes thinner. When a lower potential than that of antenna section α1 is applied to bias section β1, the potential barrier at the tip portion of antenna section α1 on the bias section β1 side becomes thicker.

[0049] The antenna section α2 extends in the Y-axis direction. The bias section β2 faces the antenna section α2. The bias section β2 is configured to generate an electric field with a Y-axis component between itself and the corresponding antenna section α2 when a bias potential is applied. In this embodiment, the bias section β2 generates an electric field in the Y-axis direction between itself and the antenna section α2. When a higher potential than that of the antenna section α2 is applied to the bias section β2, the potential barrier at the tip of the antenna section α2 on the bias section β2 side becomes thinner. When a lower potential than that of the antenna section α2 is applied to the bias section β2, the potential barrier at the tip of the antenna section α2 on the bias section β2 side becomes thicker. The state in which a higher potential than that of the antenna section is applied to the bias section is called "forward bias". The state in which a lower potential than that of the antenna section is applied to the bias section is called "reverse bias".

[0050] When electromagnetic waves W are incident on antenna sections α1 and α2, an electric field is induced around them. The electric field induced around antenna sections α1 and α2 thins the potential barrier at the antenna-vacuum interface. If the potential barrier is further thinned by the incidence of electromagnetic waves W on antenna sections α1 and α2 in a forward-biased state, electrons present in antenna sections α1 and α2 can pass through the potential barrier by tunneling. Electrons P that have passed through the potential barrier are accelerated by the electric field around antenna sections α1 and α2. Thus, field electron emission can occur when electromagnetic waves W are incident on antenna sections α1 and α2 in a forward-biased state.

[0051] Each of the patterns 31, 32, 33, 34, and 35 is arranged on the main surface 21b of the support 21. The multiple patterns 31, 32, 33, 34, and 35 are connected via an oxide layer. The multiple patterns 31, 32, 33, 34, and 35 are separated from each other by the oxide layer and are insulated from each other at least when the photoelectric converter 2 is not operating. Each of the patterns 31, 32, 33, 34, and 35 is a conductive line and conducts electrons. Each of the patterns 31, 32, 33, 34, and 35 includes at least a metal layer formed on the oxide layer of the metasurface 22. The material of this metal layer is, for example, gold.

[0052] In the example shown in Figure 3, pattern 31 includes a plurality of linear sections 41 and linear sections 42 that electrically connect the plurality of linear sections 41 to each other. Each linear section 41 extends in the Y-axis direction. Each linear section 41 constitutes a bias section β1. Each linear section 41 has, for example, a rectangular shape extending in the Y-axis direction. The linear sections 42 are connected to each linear section 41. In this embodiment, the plurality of linear sections 41 are arranged on the same straight line extending in the Y-axis direction, and adjacent linear sections 41 are connected by the plurality of linear sections 42. Multiple groups, each consisting of a plurality of linear sections 41 arranged on the same straight line extending in the Y-axis direction, are arranged parallel to each other in the Z-axis direction.

[0053] Pattern 32 includes a plurality of linear sections 43 and a plurality of linear sections 44 that electrically connect the plurality of linear sections 43 to each other. Each linear section 43 extends in the Y-axis direction. Each linear section 43 constitutes a bias section β1. Each linear section 43 has, for example, a rectangular shape extending in the Y-axis direction. Corresponding linear sections 41 and 43 are arranged on the same straight line extending in the Z-axis direction. Pattern 35 is arranged between corresponding linear sections 41 and 43. The linear sections 44 are connected to each linear section 43. In this embodiment, a plurality of linear sections 43 are arranged on the same straight line in the Y-axis direction, and adjacent linear sections 43 are connected by a plurality of linear sections 44. A plurality of groups, each consisting of a plurality of linear sections 43 arranged on the same straight line extending in the Y-axis direction, are arranged parallel to each other in the Z-axis direction. A pattern 35 is positioned between one group consisting of multiple linear portions 41 and another group consisting of multiple linear portions 43. When the linear portions 41 correspond to the first portion, the linear portions 43 correspond to the second portion.

[0054] Pattern 33 includes a plurality of linear sections 46 and a linear section 47 that electrically connects the plurality of linear sections 46 to each other. Each linear section 46 extends in the Z-axis direction. Each linear section 46 constitutes a bias section β2. Each linear section 46 has, for example, a rectangular shape extending in the Z-axis direction. The linear section 47 is connected to each linear section 46. In this embodiment, the plurality of linear sections 46 are arranged on the same straight line in the Z-axis direction, and adjacent linear sections 46 are connected by the plurality of linear sections 47. Multiple groups, each consisting of a plurality of linear sections 46 arranged on the same straight line extending in the Z-axis direction, are arranged parallel to each other in the Y-axis direction.

[0055] Pattern 34 includes a plurality of linear sections 48 and a plurality of linear sections 49 that electrically connect the plurality of linear sections 48 to each other. Each linear section 48 extends in the Z-axis direction. Each linear section 48 constitutes a bias section β2. Each linear section 48 has, for example, a rectangular shape extending in the Z-axis direction. Corresponding linear sections 46 and 48 are arranged on the same straight line extending in the Y-axis direction. Pattern 35 is arranged between corresponding linear sections 46 and 48. The linear section 49 is connected to each linear section 48. In this embodiment, a plurality of linear sections 48 are arranged on the same straight line in the Z-axis direction, and adjacent linear sections 48 are connected by a plurality of linear sections 49. A plurality of groups, each consisting of a plurality of linear sections 48 arranged on the same straight line extending in the Z-axis direction, are arranged parallel to each other in the Y-axis direction. A pattern 35 is positioned between one group consisting of multiple linear portions 46 and another group consisting of multiple linear portions 48. When the linear portions 46 correspond to the third portion, the linear portions 48 correspond to the fourth portion.

[0056] Pattern 35 extends toward patterns 31, 32, and patterns 33, 34. Pattern 35 emits electrons P in response to the incidence of electromagnetic waves W when it is given a lower potential than patterns 31, 32, 33, or 34. Pattern 35 includes a plurality of linear portions 51 and a plurality of linear portions 52. The linear portions 51 and 52 each extend in directions that intersect each other. In other words, the direction in which the linear portions 51 extend and the direction in which the linear portions 52 extend intersect each other. In this embodiment, the linear portions 51 and 52 each extend in directions that are orthogonal to each other.

[0057] Each linear portion 51 extends in the Z-axis direction. Each linear portion 51 constitutes an antenna portion α1. Each linear portion 51 has, for example, a rectangular shape extending in the Z-axis direction. Multiple linear portions 51 are parallel to each other. Pattern 35 includes linear portions 53 that electrically connect the multiple linear portions 51 to each other. The linear portions 53 are connected to each linear portion 51. In this embodiment, multiple linear portions 51 are arranged on the same straight line in the Y-axis direction, and adjacent linear portions 51 are connected by multiple linear portions 53. Multiple groups of multiple linear portions 51, each arranged on the same straight line extending in the Z-axis direction, are arranged in the Y-axis direction. Multiple linear portions 51 belonging to different groups are arranged on the same straight line extending in the Z-axis direction.

[0058] Each linear section 51 extends in the +Z-axis direction and the -Z-axis direction from the portion connected to the linear section 53. Each linear section 53 is connected to the center of each linear section 51. Each linear section 51 includes a pair of linear sections 51a and 51b. Linear section 51a extends in the +Z-axis direction from the portion connected to the linear section 53. Linear section 51b extends in the -Z-axis direction from the portion connected to the linear section 53. In this embodiment, the pair of linear sections 51a and 51b in each linear section 51 extend on the same straight line extending in the Z-axis direction. Each linear section 51 is located between a pair of bias sections β1 in the Z-axis direction. Each linear section 51 is located between pattern 31 and pattern 32 in the Z-axis direction. Each linear section 51 is located between linear section 41 and linear section 43 in the Z-axis direction.

[0059] Each linear section 52 extends in the Y-axis direction. Each linear section 52 constitutes an antenna section α2. Each linear section 52 has, for example, a rectangular shape extending in the Y-axis direction. Multiple linear sections 52 are parallel to each other. The linear section 53 described above electrically connects the multiple linear sections 52 to each other. The linear section 53 is connected to each linear section 52. In this embodiment, multiple linear sections 52 are arranged on the same straight line in the Z-axis direction, and adjacent linear sections 52 are connected by multiple linear sections 53. Multiple groups, each consisting of multiple linear sections 52 arranged on the same straight line extending in the Z-axis direction, are arranged in the Y-axis direction. Multiple linear sections 52 belonging to different groups are arranged on the same straight line extending in the Y-axis direction. In this embodiment, multiple linear sections 51 and multiple linear sections 52 are electrically connected by the linear section 53.

[0060] Each linear section 52 extends in the +Y-axis direction and the -Y-axis direction from the portion connected to the linear section 53. Each linear section 53 is connected to the center of each linear section 52. Each linear section 52 includes a pair of linear sections 52a and 52b. Linear section 52a extends in the +Y-axis direction from the portion connected to the linear section 53. Linear section 52b extends in the -Y-axis direction from the portion connected to the linear section 53. In this embodiment, the pair of linear sections 52a and 52b in each linear section 52 extend on the same straight line in the Y-axis direction. Each linear section 52 is located between a pair of bias sections β2 in the Y-axis direction. Each linear section 52 is located between pattern 33 and pattern 34 in the Y-axis direction. Each linear section 52 is located between linear section 46 and linear section 48 in the Y-axis direction.

[0061] Pattern 35 includes a tip 36 facing pattern 31, a tip 37 facing pattern 32, a tip 38 facing pattern 33, and a tip 39 facing pattern 34. For example, tip 36 corresponds to the first tip, tip 37 to the second tip, tip 38 to the third tip, and tip 39 to the fourth tip. In this embodiment, each linear shape portion 51 constituting the antenna portion α1 includes tip 36 and tip 37, and each linear shape portion 52 constituting the antenna portion α2 includes tip 38 and tip 39.

[0062] Tip 36 and tip 37 are located at both ends of each linear section 51. Tip 36 is included in the linear section 51a. Tip 37 is included in the linear section 51b. Tips 36 and 37, which are included in the same linear section 51, are arranged on the same straight line extending in the Z-axis direction. Tips 38 and 39 are located at both ends of each linear section 52. Tip 38 is included in the linear section 52a. Tip 39 is included in the linear section 52b. Tips 38 and 39, which are included in the same linear section 52, are arranged on the same straight line extending in the Y-axis direction.

[0063] The tip 36 faces the bias portion β1. The tip 36 faces the corresponding linear portion 41 of the bias portion β1. The linear portion 41 generates an electric field having a Z-axis component between itself and the tip 36. The tip 36 is the portion of the linear portion 51 that includes the tip 36 that is closest to the pattern 31. The tip 36 is positioned closer to the corresponding linear portion 41 than other portions of the pattern 35.

[0064] The tip 37 faces the bias portion β1. The tip 37 faces the corresponding linear portion 43 of the bias portion β1. The linear portion 43 generates an electric field having a Z-axis component between itself and the tip 37. The tip 37 is the portion of the linear portion 51 that includes the tip 37 that is closest to the pattern 32. The tip 37 is positioned closer to the corresponding linear portion 43 than other portions of the pattern 35.

[0065] The tips 36 and 37, and the linear portions 41 and 43 are arranged in the order of linear portion 43, tip 37, tip 36, and linear portion 41 in the Z-axis direction. In the photoelectric conversion unit 25, each linear portion 51 can emit electrons P in response to the incidence of electromagnetic waves W when a lower potential than that of linear portion 41 or linear portion 43 is applied to it.

[0066] The tip 38 faces the bias portion β2. The tip 38 faces the corresponding linear portion 46 of the bias portion β2. The linear portion 46 generates an electric field having a Y-axis component between itself and the tip 38. The tip 38 is the portion of the linear portion 52 that includes the tip 38 that is closest to the pattern 33. The tip 38 is positioned closer to the corresponding linear portion 46 than other portions of the pattern 35.

[0067] The tip 39 faces the bias portion β2. The tip 39 faces the corresponding linear portion 48 of the bias portion β2. The linear portion 48 generates an electric field having a Y-axis component between itself and the tip 39. The tip 39 is the portion of the linear portion 52 that includes the tip 39 that is closest to the pattern 34. The tip 39 is positioned closer to the corresponding linear portion 48 than other portions of the pattern 35.

[0068] The tip 38 and tip 39, and the linear portion 46 and linear portion 48 are arranged in the order of linear portion 48, tip 39, tip 38, and linear portion 46 in the Y-axis direction. In the photoelectric conversion unit 25, each linear portion 52 can emit electrons P in response to the incidence of electromagnetic waves W when a lower potential than that of the linear portion 46 or linear portion 48 is applied to it.

[0069] The photoelectric conversion unit 25 is configured to correspond to wavelengths ranging from so-called millimeter waves to infrared light, depending on the structure of the linear sections 51 and 52. For example, the length of the linear section 51 in the Z-axis direction corresponds to the wavelength range of the electromagnetic wave W from which electrons P are emitted in the photoelectric conversion unit 25. For example, the length of the linear section 51 in the Z-axis direction is designed according to a desired wavelength range from which electrons P are emitted from the photoelectric conversion unit 25. Similarly, the length of the linear section 52 in the Y-axis direction corresponds to the wavelength range of the electromagnetic wave W from which electrons P are emitted in the photoelectric conversion unit 25. For example, the length of the linear section 52 in the Y-axis direction is designed according to a desired wavelength range from which electrons P are emitted from the photoelectric conversion unit 25. For example, each linear section 51, 52 has a length of half the central wavelength in the desired wavelength range. The length of each linear section 51 is from tip 36 to tip 37 in the Z-axis direction. The length of each linear section 52 is from tip 38 to tip 39 in the Y-axis direction.

[0070] In this embodiment, when electromagnetic waves W transmitted through the support 21, etc., are incident on the linear portions 51 and 52, the refractive index of the transmitted support 21, etc., is also taken into consideration. For example, if the wavelength of electromagnetic waves W incident on the electron tube is 600 μm, and the refractive index of the support 21 is 3.4 relative to this electromagnetic wave W, then the wavelength of electromagnetic waves W incident on the linear portions 51 and 52 is 600 μm / 3.4 = 176 μm. Therefore, in this case, for example, the length of the linear portion 51 in the Z-axis direction and the length of the linear portion 52 in the Y-axis direction are suitable to be 176 μm / 2 = 88 μm.

[0071] As shown in Figure 3, the electron-emitting member 20 further comprises a plurality of electrodes 61, 62, 63, 64, and 65 spaced apart from each other. The plurality of electrodes 61, 62, 63, 64, and 65 are provided on the main surface 21b of the support 21. The plurality of electrodes 61, 62, 63, 64, and 65 are electrically connected to the photoelectric conversion unit 25. In this embodiment, each electrode 61, 62, 63, 64, and 65 has a rectangular shape. In a modified example of this embodiment, each electrode 61, 62, 63, 64, and 65 may have a linear shape similar to the linear portions 42, 44, 47, 49, and 53. These electrodes may be connected to the main surface 21a side of the support 21 by through electrodes.

[0072] For example, electrode 61 is included in pattern 31. Electrode 61 is electrically connected to a plurality of linear portions 41 via a linear portion 42. Electrode 61 may be formed integrally with the linear portion 42 and the plurality of linear portions 41. Electrode 62 is included in pattern 32. Electrode 62 is electrically connected to a plurality of linear portions 43 via a linear portion 44. Electrode 62 may be formed integrally with the linear portion 44 and the plurality of linear portions 43. Electrode 63 is included in pattern 33. Electrode 63 is electrically connected to a plurality of linear portions 46 via a linear portion 47. Electrode 63 may be formed integrally with the linear portion 47 and the plurality of linear portions 46. Electrode 64 is included in pattern 34. Electrode 64 is electrically connected to a plurality of linear portions 48 via a linear portion 49. Electrode 64 may be formed integrally with the linear portion 49 and the plurality of linear portions 48. The electrode 65 is included in the pattern 35. The electrode 65 is electrically connected to a plurality of linear portions 51, 52 via a linear portion 53. The electrode 65 may be formed integrally with the linear portion 53 and the plurality of linear portions 51, 52.

[0073] The photoelectric conversion unit 25 operates by receiving a potential from the power supply unit 70 via multiple electrodes 61, 62, 63, 64, and 65. The potential application unit 71 of the power supply unit 70 applies a potential to the photoelectric conversion unit 25 via the multiple electrodes 61, 62, 63, 64, and 65. The potential control unit 72 of the power supply unit 70 controls the potential applied to the photoelectric conversion unit 25 of the metasurface 22.

[0074] Next, the operation of the photoelectric converter 2 in this embodiment will be described in detail with reference to Figures 4(a), 4(b), 5, 6, 7(a), and 7(b). Figures 4(a), 4(b), 5, 6, 7(a), and 7(b) show a part of the photoelectric converter 25. Figures 4(a), 4(b), and 6 are diagrams for explaining the operation of the antenna section α1 and the bias section β1 in different states. Figures 5, 7(a), and 7(b) are diagrams for explaining the operation of the antenna section α2 and the bias section β2. In Figures 4(a), 4(b), 5, 6, 7(a), and 7(b), arrow D1 indicates the direction of the electric field generated around the antenna section α1 or antenna section α2. In Figures 4(a), 4(b), 7(a), and 7(b), arrow D2 indicates the direction in which electron P moves in antenna section α1 or antenna section α2.

[0075] The potential control unit 72 switches between the first and second states, and between the third and fourth states, by controlling the potential applied to multiple patterns 31, 32, 33, 34, and 35. The first state corresponds to the state shown in Figures 4(a) and 5. In the first state, the potential control unit 72 controls the potential so that electrons P are emitted from the tip 37 of the antenna part α1 in response to the incidence of electromagnetic waves W, while the emission of electrons from the tip 36 of the antenna part α1 and the tips 38 and 39 of the antenna part α2 is suppressed. The second state corresponds to the state shown in Figures 4(b) and 5. In the second state, the potential control unit 72 controls the potential so that electrons P are emitted from the tip 36 of the antenna part α1 in response to the incidence of electromagnetic waves W, while the emission of electrons from the tip 37 of the antenna part α1 and the tips 38 and 39 of the antenna part α2 is suppressed. The third state corresponds to the state shown in Figures 6 and 7(a). In the third state, the potential control unit 72 controls the potential such that electrons P are emitted from the tip 39 of antenna section α2 in response to the incidence of electromagnetic waves W, while electron emission from the tips 36, 37 of antenna section α1 and the tip 38 of antenna section α2 is suppressed. The fourth state corresponds to the state shown in Figures 6 and 7(b). In the fourth state, the potential control unit 72 controls the potential such that electrons P are emitted from the tip 38 of antenna section α2 in response to the incidence of electromagnetic waves W, while electron emission from the tips 36, 37 of antenna section α1 and the tip 39 of antenna section α2 is suppressed.

[0076] In the first state, the potential applied to pattern 35 is higher than the potential applied to pattern 31 and lower than the potential applied to pattern 32. In other words, the potential applied to the linear portion 41 constituting the bias portion β1 is lower than the potential applied to the linear portion 51a constituting the antenna portion α1. The potential applied to the linear portion 43 constituting the bias portion β1 is higher than the potential applied to the linear portion 51b constituting the antenna portion α1.

[0077] In this case, as shown in Figure 4(a), an electric field is generated in the +Z direction between the tip 36 and the linear portion 41, and an electric field is generated in the +Z direction between the tip 37 and the linear portion 43. In other words, an electric field is generated from the linear portion 51a constituting the antenna portion α1 toward the linear portion 41 constituting the bias portion β1. An electric field is generated from the linear portion 43 constituting the bias portion β1 toward the linear portion 51b constituting the antenna portion α1.

[0078] As a result, in the first state, the potential barrier at the tip of the antenna portion α1, which is composed of the linear portion 51a, becomes thicker. In other words, the potential difference between pattern 35 and pattern 31 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear portion 51a in response to the incidence of electromagnetic waves W onto the linear portion 51a is suppressed. In the first state, the component of the electric field in the Z-axis direction from the tip 36 of the linear portion 51a toward the linear portion 41 that constitutes the bias portion β1 is positive.

[0079] In the first state, the potential barrier at the tip of the antenna portion α1, which is composed of the linear portion 51b, becomes thinner. In other words, the potential difference between pattern 35 and pattern 32 thins the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons P from the linear portion 51b in response to the incidence of electromagnetic waves W on the linear portion 51b is promoted. In the first state, the component of the electric field in the Z-axis direction from the linear portion 43, which constitutes the bias portion β1, toward the tip 37 of the linear portion 51b, which constitutes the antenna portion α1, is positive. Therefore, in the first state, when the component of the electric field strength in the Z-axis direction of the electromagnetic wave W incident on the photoelectric conversion unit 25 is positive, the potential barrier at the antenna-vacuum interface becomes even thinner in response to the incidence of this electromagnetic wave W. Therefore, in the first state, when the component of the electric field strength in the Z-axis direction of the electromagnetic wave W incident on the photoelectric conversion unit 25 is positive, electrons P are emitted from the linear portion 51b.

[0080] In the first state, the potential applied to pattern 35 is higher than the potential applied to patterns 33 and 34. In other words, the potential applied to the linear portion 46 constituting the bias portion β2 is lower than the potential applied to the linear portion 51b constituting the antenna portion α2. The potential applied to the linear portion 48 constituting the bias portion β2 is lower than the potential applied to the linear portion 51b constituting the antenna portion α2.

[0081] In this case, as shown in Figure 5, an electric field is generated in the +Y axis direction between the tip 38 and the linear portion 46, and an electric field is generated in the -Y axis direction between the tip 39 and the linear portion 48. In other words, an electric field is generated from the linear portion 52a constituting the antenna portion α2 toward the linear portion 46 constituting the bias portion β2. An electric field is generated from the linear portion 52b constituting the antenna portion α2 toward the linear portion 48 constituting the bias portion β2.

[0082] As a result, in the first state, the potential barrier at each tip of the antenna section α2, which is composed of the linear sections 52a and 52b, becomes thicker. In other words, the potential difference between pattern 35 and patterns 33 and 34 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear sections 52a and 52b in response to the incidence of electromagnetic waves W on them is suppressed. In the first state, the component of the electric field in the Y-axis direction from the tip 38 of the linear section 52a toward the linear section 46 that constitutes the bias section β2 is positive, and the component of the electric field in the Y-axis direction from the tip 39 of the linear section 52b toward the linear section 48 that constitutes the bias section β2 is negative.

[0083] In the second state, the potential applied to pattern 35 is lower than the potential applied to pattern 31 and higher than the potential applied to pattern 32. In other words, the potential applied to the linear portion 41 constituting the bias portion β1 is higher than the potential applied to the linear portion 51a constituting the antenna portion α1. The potential applied to the linear portion 43 constituting the bias portion β1 is lower than the potential applied to the linear portion 51b constituting the antenna portion α1.

[0084] In this case, as shown in Figure 4(b), an electric field is generated in the -Z direction between the tip 36 and the linear portion 41, and an electric field is generated in the -Z direction between the tip 37 and the linear portion 43. In other words, an electric field is generated from the linear portion 41 constituting the bias portion β1 toward the linear portion 51a constituting the antenna portion α1. An electric field is generated from the linear portion 51b constituting the antenna portion α1 toward the linear portion 43 constituting the bias portion β1.

[0085] As a result, in the second state, the potential barrier at the tip of the antenna portion α1, which is composed of the linear portion 51a, becomes thinner. In other words, the potential difference between pattern 35 and pattern 31 thins the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons P from the linear portion 51a in response to the incidence of electromagnetic waves W on the linear portion 51a is promoted. In the second state, the component of the electric field in the Z-axis direction from the linear portion 41 constituting the bias portion β1 toward the tip 36 of the linear portion 51a constituting the antenna portion α1 is negative. For this reason, in the second state, when the component of the electric field strength in the Z-axis direction of the electromagnetic wave W incident on the photoelectric conversion unit 25 is negative, the potential barrier at the antenna-vacuum interface becomes even thinner in response to the incidence of this electromagnetic wave W. As a result, in the second state, when the component of the electric field strength in the Z-axis direction of the electromagnetic wave W incident on the photoelectric conversion unit 25 is negative, electrons P are emitted from the linear portion 51a.

[0086] In the second state, the potential barrier at the tip of the antenna portion α1, which is composed of the linear portion 51b, becomes thicker. In other words, the potential difference between pattern 35 and pattern 32 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear portion 51b in response to the incidence of electromagnetic waves W onto the linear portion 51b is suppressed. In the second state, the component of the electric field in the Z-axis direction from the tip 37 of the linear portion 51b toward the linear portion 43 that constitutes the bias portion β1 is negative.

[0087] In the second state, the potential applied to pattern 35 is higher than the potential applied to patterns 33 and 34, similar to the first state. In other words, the potential applied to the linear portion 46 constituting the bias section β2 is lower than the potential applied to the linear portion 51b constituting the antenna section α2. The potential applied to the linear portion 48 constituting the bias section β2 is lower than the potential applied to the linear portion 51b constituting the antenna section α2.

[0088] In the second state, as shown in Figure 5, an electric field is generated in the +Y direction between the tip 38 and the linear portion 46, and an electric field is generated in the -Y direction between the tip 39 and the linear portion 48. As a result, in the second state, the potential barrier at each tip portion of the antenna portion α2, which is composed of the linear portions 52a and 52b, becomes thicker. In other words, the potential difference between pattern 35 and patterns 33 and 34 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear portions 52a and 52b in response to the incidence of electromagnetic waves W on the linear portions 52a and 52b is suppressed. In the second state, the Y-axis component of the electric field from the tip 38 of the linear portion 52a toward the linear portion 46 that constitutes the bias portion β2 is positive, and the Y-axis component of the electric field from the tip 39 of the linear portion 52b toward the linear portion 48 that constitutes the bias portion β2 is negative.

[0089] In the third state, the potential applied to pattern 35 is higher than the potential applied to patterns 31 and 32. In other words, the potential applied to the linear portion 41 constituting the bias portion β1 is lower than the potential applied to the linear portion 51a constituting the antenna portion α1. The potential applied to the linear portion 43 constituting the bias portion β1 is lower than the potential applied to the linear portion 51a constituting the antenna portion α1.

[0090] In this case, as shown in Figure 6, an electric field is generated in the +Z direction between the tip 36 and the linear portion 41, and an electric field is generated in the -Z direction between the tip 37 and the linear portion 43. In other words, an electric field is generated from the linear portion 51a constituting the antenna portion α1 toward the linear portion 41 constituting the bias portion β1. An electric field is generated from the linear portion 51b constituting the antenna portion α1 toward the linear portion 43 constituting the bias portion β1.

[0091] As a result, in the third state, the potential barrier at each tip of the antenna section α1, which is composed of the linear sections 51a and 51b, becomes thicker. In other words, the potential difference between pattern 35 and patterns 31 and 32 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear sections 51a and 51b in response to the incidence of electromagnetic waves W on them is suppressed. In the third state, the component of the electric field in the Z-axis direction from the tip 36 of the linear section 51a toward the linear section 41 that constitutes the bias section β1 is positive, and the component of the electric field in the Z-axis direction from the tip 37 of the linear section 51b toward the linear section 43 that constitutes the bias section β1 is negative.

[0092] In the third state, the potential applied to pattern 35 is higher than the potential applied to pattern 33 and lower than the potential applied to pattern 34. In other words, the potential applied to the linear portion 46 constituting the bias portion β2 is lower than the potential applied to the linear portion 52a constituting the antenna portion α2. The potential applied to the linear portion 48 constituting the bias portion β2 is higher than the potential applied to the linear portion 52b constituting the antenna portion α2.

[0093] In this case, as shown in Figure 7(a), an electric field is generated in the +Y axis direction between the tip 38 and the linear portion 46, and an electric field is generated in the +Y axis direction between the tip 39 and the linear portion 48. In other words, an electric field is generated from the linear portion 52a constituting the antenna portion α2 toward the linear portion 46 constituting the bias portion β2. An electric field is generated from the linear portion 48 constituting the bias portion β2 toward the linear portion 52b constituting the antenna portion α2.

[0094] As a result, in the third state, the potential barrier at the tip of the antenna portion α2, which is composed of the linear portion 52a, becomes thicker. In other words, the potential difference between pattern 35 and pattern 33 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear portion 52a in response to the incidence of electromagnetic waves W onto the linear portion 52a is suppressed. In the third state, the component of the electric field in the Y-axis direction from the tip 38 of the linear portion 52a toward the linear portion 46 that constitutes the bias portion β2 is positive.

[0095] In the third state, the potential barrier at the tip of the antenna portion α2, which is composed of the linear portion 52b, becomes thinner. In other words, the potential difference between pattern 35 and pattern 34 thins the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons P from the linear portion 52b in response to the incidence of electromagnetic waves W on the linear portion 52b is promoted. In the third state, the Y-axis component of the electric field from the linear portion 48, which constitutes the bias portion β2, toward the tip 39 of the linear portion 52b, which constitutes the antenna portion α2, is positive. Therefore, in the third state, when the Y-axis component of the electric field strength of the electromagnetic wave W incident on the photoelectric conversion unit 25 is positive, the potential barrier at the antenna-vacuum interface becomes even thinner in response to the incidence of this electromagnetic wave W. As a result, in the third state, when the Z-axis component of the electric field strength of the electromagnetic wave W incident on the photoelectric conversion unit 25 is positive, electrons P are emitted from the linear portion 52b.

[0096] In the fourth state, the potential applied to pattern 35 is higher than the potential applied to patterns 31 and 32, similar to the third state. In other words, the potential applied to the linear portion 41 constituting the bias section β1 is lower than the potential applied to the linear portion 51a constituting the antenna section α1. The potential applied to the linear portion 43 constituting the bias section β1 is lower than the potential applied to the linear portion 51a constituting the antenna section α1.

[0097] In the fourth state, as shown in Figure 6, an electric field is generated in the +Z direction between the tip 36 and the linear portion 41, and an electric field is generated in the -Z direction between the tip 37 and the linear portion 43. As a result, in the fourth state, the potential barrier at each tip portion of the antenna portion α1, which is composed of the linear portions 51a and 51b, becomes thicker. In other words, the potential difference between pattern 35 and patterns 31 and 32 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear portions 51a and 51b in response to the incidence of electromagnetic waves W on them is suppressed. In the fourth state, the component of the electric field in the Z direction from the tip 36 of the linear portion 51a toward the linear portion 41 that constitutes the bias portion β1 is positive, and the component of the electric field in the Z direction from the tip 37 of the linear portion 51b toward the linear portion 43 that constitutes the bias portion β1 is negative.

[0098] In the fourth state, the potential applied to pattern 35 is lower than the potential applied to pattern 33 and higher than the potential applied to pattern 34. In other words, the potential applied to the linear portion 46 constituting the bias portion β2 is higher than the potential applied to the linear portion 52a constituting the antenna portion α2. The potential applied to the linear portion 48 constituting the bias portion β2 is lower than the potential applied to the linear portion 52b constituting the antenna portion α2.

[0099] In this case, as shown in Figure 7(b), an electric field is generated in the -Y axis direction between the tip 38 and the linear portion 46, and an electric field is generated in the -Y axis direction between the tip 39 and the linear portion 48. In other words, an electric field is generated from the linear portion 46 constituting the bias portion β2 toward the linear portion 52a constituting the antenna portion α2. An electric field is generated from the linear portion 52b constituting the antenna portion α2 toward the linear portion 48 constituting the bias portion β2.

[0100] As a result, in the fourth state, the potential barrier at the tip of the antenna portion α2, which is composed of the linear portion 52a, becomes thinner. In other words, the potential difference between pattern 35 and pattern 33 thins the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons P from the linear portion 52a in response to the incidence of electromagnetic waves W on the linear portion 52a is promoted. In the fourth state, the Y-axis component of the electric field from the linear portion 46 constituting the bias portion β2 toward the tip 38 of the linear portion 52a constituting the antenna portion α2 is negative. Therefore, in the fourth state, when the Y-axis component of the electric field strength of the electromagnetic wave W incident on the photoelectric conversion unit 25 is negative, the potential barrier at the antenna-vacuum interface becomes even thinner in response to the incidence of this electromagnetic wave W. Therefore, in the fourth state, when the Y-axis component of the electric field strength of the electromagnetic wave W incident on the photoelectric conversion unit 25 is negative, electrons P are emitted from the linear portion 52a.

[0101] In the fourth state, the potential barrier at the tip of the antenna portion α2, which is composed of the linear portion 52b, becomes thicker. In other words, the potential difference between pattern 35 and pattern 34 thickens the potential barrier at the antenna-vacuum interface. Therefore, the emission of electrons from the linear portion 52b in response to the incidence of electromagnetic waves W onto the linear portion 52b is suppressed. In the fourth state, the component of the electric field in the Y-axis direction from the tip 39 of the linear portion 52b toward the linear portion 48 that constitutes the bias portion β2 is negative.

[0102] The calculation unit 75 calculates polarization information of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the first, second, third, and fourth states. The detection results of the electron collection unit 50 are, for example, information indicating the emission intensity of electrons emitted from the electron-emitting member 20. The emission intensity represents the amount of electrons emitted and depends on the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20. For example, the calculation unit 75 calculates first information regarding the positive component of the electric field strength of the electromagnetic wave W in the Z-axis direction based on the detection results of the electron collection unit 50 in the first state. The calculation unit 75 calculates second information regarding the negative component of the electric field strength of the electromagnetic wave W in the Z-axis direction based on the detection results of the electron collection unit 50 in the second state. The calculation unit 75 calculates third information regarding the positive component of the electric field strength of the electromagnetic wave W in the Y-axis direction based on the detection results of the electron collection unit 50 in the third state. The calculation unit 75 calculates fourth information regarding the negative component of the electric field strength of the electromagnetic wave W in the Y-axis direction based on the detection result of the electron collection unit 50 in the fourth state. Based on the first information, second information, third information, and fourth information, the calculation unit 75 calculates polarization information of the electric field strength of the electromagnetic wave W incident on the electron emission member 20.

[0103] The calculation unit 75 calculates the electric field strength in the Z-axis direction of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the first and second states. The calculation unit 75 determines the polarity in the Z-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the first and second states. For example, the calculation unit 75 determines the polarity of the electric field in the Z-axis direction by comparing the detection result of the electron collection unit 50 in the first state with the detection result of the electron collection unit 50 in the second state. The calculation unit 75 calculates the electric field strength in the Y-axis direction of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the third and fourth states. The calculation unit 75 determines the polarity in the Y-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the third and fourth states. For example, the calculation unit 75 determines the polarity of the electric field in the Y-axis direction by comparing the detection result of the electron collection unit 50 in the third state with the detection result of the electron collection unit 50 in the fourth state. The calculation unit 75 calculates the polarization information of the electromagnetic wave W incident on the electron emission member 20 based on the electric field strength in the Z-axis direction and the electric field strength in the Y-axis direction. For example, the calculation unit 75 determines the polarization direction of the electromagnetic wave W incident on the electron emission member 20 by comparing the electric field strength in the Z-axis direction and the electric field strength in the Y-axis direction.

[0104] Next, a modified example of the electron emission member will be described with reference to Figure 8. Figure 8 is a plan view of the electron emission member in the modified example of this embodiment. This modified example is generally similar to or the same as the embodiment described above. The electron emission member in this modified example differs from the embodiment described above in that it also includes an antenna portion that has sensitivity in directions intersecting the Y-axis and Z-axis directions. The differences between the embodiment described above and the modified example will be mainly described below.

[0105] In this modified example, the electron-emitting member 20 has a metasurface 22A. The metasurface 22A corresponds to the metasurface 22. The metasurface 22A is of the active type and operates by the application of a bias voltage. The metasurface 22A operates by being supplied with a potential by the power supply unit 70.

[0106] The metasurface 22A shown in Figure 8 includes at least one photoelectric conversion unit 25A. The photoelectric conversion unit 25A emits electrons P in response to the incidence of an electromagnetic wave W having corresponding wavelength and corresponding electric field strength directional components. The photoelectric conversion unit 25A is sensitive to the Y-axis and Z-axis components of the electric field strength of the electromagnetic wave W, as well as the γ1-axis component that intersects the Y-axis and Z-axis. The γ1-axis is an axis that intersects the Y-axis and Z-axis in the YZ plane. The γ1-axis direction is orthogonal to the γ2-axis direction. The γ2-axis direction is inclined at an angle of 45 degrees with respect to the Y-axis and Z-axis in the YZ plane. The cases in which the photoelectric conversion unit 25A is sensitive to a positive Y-axis component, a negative Y-axis component, a positive Z-axis component, a negative Z-axis component, a positive γ1-axis component, and a negative γ1-axis component are switched according to the potential control by the potential control unit 72. The directional components and frequency ranges of the electric field to which the photoelectric conversion unit 25A is sensitive are not limited to these. When the Z-axis and Y-axis directions correspond to the first and second directions, the γ1-axis direction corresponds to the third direction.

[0107] The metasurface 22A shown in Figure 8 includes multiple spaced patterns 31A, 32A, 33A, 34A, 35A, 81A, and 82A. The directional component and frequency range of the electric field to which the photoelectric conversion unit 25A is sensitive depends on the configuration of the multiple patterns 31A, 32A, 33A, 34A, 35A, 81A, and 82A. Each of the multiple patterns 31A and 32A includes a bias section β1. Each of the patterns 33A and 34A includes a bias section β2. Each of the patterns 35A includes antenna sections α1, α2, and α3. Each of the patterns 81A and 82A includes a bias section β3. In the antenna section α3, as with antenna sections α1 and α2, the smaller the size of the antenna section α3, the more likely field electron emission is to occur for electromagnetic waves with shorter wavelengths, i.e., electromagnetic waves with higher frequencies. Antenna section α3 is sensitive to directional components different from those of antenna sections α1 and α2. Antenna section α3 is sensitive to the component in the γ1 axis direction within the YZ plane. Antenna section α3 extends in the γ1 axis direction. For example, if antenna sections α1 and α2 correspond to the first and second antenna sections, then antenna section α3 corresponds to the third antenna section. If bias sections β1 and β2 correspond to the first and second bias sections, then bias section β3 corresponds to the third bias section.

[0108] Antenna sections α1, α2, and α3 emit electrons P in response to the incidence of electromagnetic waves W. Bias section β3 faces antenna section α3. When a bias potential is applied to bias section β3, it is configured to generate an electric field with a component in the γ1 axis direction between it and the corresponding antenna section α3. In this embodiment, bias section β3 generates an electric field in the γ1 axis direction between it and antenna section α3. When a bias potential is applied to bias section β3, it generates an electric field between it and the corresponding antenna section α3. When a higher potential than that of antenna section α3 is applied to bias section β3, the potential barrier at the tip portion of antenna section α3 on the bias section β3 side becomes thinner. When a lower potential than that of antenna section α3 is applied to bias section β3, the potential barrier at the tip portion of antenna section α3 on the bias section β3 side becomes thicker. When electromagnetic waves W are incident on antenna section α3, an electric field is induced around antenna section α3, similar to antenna sections α1 and α2. If the potential barrier becomes even thinner due to the incidence of electromagnetic waves W on antenna section α3 in a forward bias state, field electron emission may occur.

[0109] Each pattern 31A, 32A, 33A, 34A, 35A, 81A, 82A is arranged on the main surface 21b of the support 21. Multiple patterns 31A, 32A, 33A, 34A, 35A, 81A, 82A are connected via an oxide layer. Multiple patterns 31A, 32A, 33A, 34A, 35A, 81A, 82A are separated from each other by the oxide layer and are insulated from each other at least when the photoelectric converter 2 is not operating. Each pattern 31A, 32A, 33A, 34A, 35A, 81A, 82A is a conductive line and conducts electrons. Each pattern 31A, 32A, 33A, 34A, 35A, 81A, 82A includes at least a metal layer formed on the oxide layer of the metasurface 22A. The material of this metal layer is, for example, gold.

[0110] In the example shown in Figure 8, pattern 31A includes a plurality of linear sections 41A and a plurality of linear sections 42A that electrically connect the plurality of linear sections 41A to each other. Each linear section 41A extends in the Y-axis direction. Each linear section 41A constitutes a bias section β1. Each linear section 41A has, for example, a rectangular shape extending in the Y-axis direction. The linear section 42A is connected to each linear section 41A. In this modified example, the plurality of linear sections 41A are arranged on the same straight line extending in the Y-axis direction, and adjacent linear sections 41A are connected by the plurality of linear sections 42A.

[0111] Pattern 32A includes a plurality of linear sections 43A and a linear section 44A that electrically connects the plurality of linear sections 43A to each other. Each linear section 43A extends in the Y-axis direction. Each linear section 43A constitutes a bias section β1. Each linear section 43A has, for example, a rectangular shape extending in the Y-axis direction. Corresponding linear sections 41A and 43A are arranged on the same straight line extending in the Z-axis direction. Pattern 35 is arranged between the corresponding linear sections 41A and 43A. The linear section 44A is connected to each linear section 43A. In this modified example, a plurality of linear sections 43A are arranged on the same straight line in the Y-axis direction, and adjacent linear sections 43A are connected by a plurality of linear sections 44A. When a linear section 41A corresponds to the first part, a linear section 43A corresponds to the second part.

[0112] Pattern 33A includes a plurality of linear sections 46A and a linear section 47A that electrically connects the plurality of linear sections 46A to each other. Each linear section 46A extends in the Z-axis direction. Each linear section 46A constitutes a bias section β2. Each linear section 46A has, for example, a rectangular shape that extends in the Z-axis direction. The linear section 47A is connected to each linear section 46A. In this modified example, the plurality of linear sections 46A are arranged on the same straight line in the Z-axis direction, and adjacent linear sections 46A are connected by the plurality of linear sections 47A.

[0113] Pattern 34A includes a plurality of linear sections 48A and a linear section 49A that electrically connects the plurality of linear sections 48A to each other. Each linear section 48A extends in the Z-axis direction. Each linear section 48A constitutes a bias section β2. Each linear section 48A has, for example, a rectangular shape extending in the Z-axis direction. Corresponding linear sections 46A and 48A are arranged on the same straight line extending in the Y-axis direction. Pattern 35 is arranged between corresponding linear sections 46A and 48A. The linear section 49A is connected to each linear section 48A. In this modified example, a plurality of linear sections 48A are arranged on the same straight line in the Z-axis direction, and adjacent linear sections 48A are connected by a plurality of linear sections 49A. When linear section 46A corresponds to the third section, linear section 48A corresponds to the fourth section.

[0114] Pattern 81A includes a plurality of linear sections 86A and a linear section 87A that electrically connects the plurality of linear sections 86A to each other. Each linear section 86A extends in the direction of the γ2 axis. Each linear section 86A constitutes a bias section β3. Each linear section 86A has, for example, a rectangular shape that extends in the direction of the γ2 axis. The linear section 87A is connected to each linear section 86A. In this modified example, the plurality of linear sections 86A are arranged on the same straight line in the direction of the γ2 axis, and adjacent linear sections 86A are connected by the plurality of linear sections 87A.

[0115] Pattern 82A includes a plurality of linear sections 88A and a linear section 89A that electrically connects the plurality of linear sections 88A to each other. Each linear section 88A extends in the direction of the γ2 axis. Each linear section 88A constitutes a bias section β2. Each linear section 88A has, for example, a rectangular shape that extends in the direction of the γ2 axis. Corresponding linear sections 86A and 88A are arranged on the same straight line extending in the direction of the γ1 axis. Pattern 35 is arranged between corresponding linear sections 86A and 88A. The linear section 89A is connected to each linear section 88A. In this modified example, a plurality of linear sections 88A are arranged on the same straight line in the direction of the γ2 axis, and adjacent linear sections 88A are connected by a plurality of linear sections 89A. When linear section 86A corresponds to the fifth section, linear section 88A corresponds to the sixth section.

[0116] Pattern 35A extends toward patterns 31A, 32A, 33A, 34A, and 81A, 82A. Pattern 35A emits electrons P in response to the incidence of electromagnetic waves W when it is given a lower potential than patterns 31A, 32A, 33A, 34A, 81A, or 82A. Pattern 35A includes a plurality of linear portions 91, a plurality of linear portions 92, and a plurality of linear portions 95. The linear portions 91, 92, and 95 each extend in directions that intersect each other in the YZ plane. In other words, the direction in which the linear portion 91 extends, the direction in which the linear portion 92 extends, and the direction in which the linear portion 95 extends intersect each other in the YZ plane. In this modified example, the linear portions 91 and 92 each extend in directions that are orthogonal to each other.

[0117] Each linear section 91 extends in the Z-axis direction and has the same configuration as the linear section 51 described above. Each linear section 91 constitutes the antenna section α1, similar to the linear section 51. Pattern 35A includes a linear section 93 that electrically connects a plurality of linear sections 91 to each other. The linear section 93 is connected to each linear section 91. Each linear section 91 includes a pair of linear sections 91a and 91b corresponding to a pair of linear sections 51a and 51b. The linear section 91a extends in the +Z-axis direction from the portion connected to the linear section 93. The linear section 91b extends in the -Z-axis direction from the portion connected to the linear section 93. In this embodiment, each linear section 91 is positioned between the linear section 41A and the linear section 43A in the Z-axis direction.

[0118] Each linear section 92 extends in the Y-axis direction and has the same configuration as the linear section 52 described above. Each linear section 92 constitutes the antenna section α2, similar to the linear section 52. The linear section 93 described above electrically connects the multiple linear sections 92 to each other. The linear section 93 is connected to each linear section 92. Each linear section 92 includes a pair of linear sections 92a and 92b corresponding to a pair of linear sections 52a and 52b. The linear section 92a extends in the +Y-axis direction from the portion connected to the linear section 93. The linear section 92b extends in the -Y-axis direction from the portion connected to the linear section 93. In this embodiment, each linear section 92 is positioned between the linear section 46A and the linear section 48A in the Y-axis direction. The multiple linear sections 91 and the multiple linear sections 92 are electrically connected by the linear section 93.

[0119] Each linear portion 95 extends in the direction of the γ1 axis. Each linear portion 95 constitutes an antenna portion α3. Each linear portion 95 has, for example, a rectangular shape extending in the direction of the γ1 axis. Multiple linear portions 95 are parallel to each other. The linear portion 93 described above electrically connects the multiple linear portions 95 to each other. The linear portion 93 is connected to each linear portion 95. In this modified example, multiple linear portions 95 are arranged on the same straight line in the direction of the γ2 axis, and adjacent linear portions 95 are connected by multiple linear portions 93.

[0120] Each linear section 95 extends in the +γ1 axis direction and the -γ1 axis direction from the portion connected to the linear section 93. Each linear section 93 is connected to the center of each linear section 95. Each linear section 95 includes a pair of linear sections 95a and 95b. Linear section 95a extends in the -γ1 axis direction from the portion connected to the linear section 93. Linear section 95b extends in the +γ1 axis direction from the portion connected to the linear section 93. In this modified example, the pair of linear sections 95a and 95b in each linear section 95 extend on the same straight line in the γ1 axis direction. Each linear section 95 is positioned between a pair of bias sections β3 in the γ1 axis direction. Each linear section 93 is positioned between pattern 81A and pattern 82A in the γ1 axis direction. Each linear section 95 is positioned between linear section 86A and linear section 88A in the γ1 axis direction.

[0121] Pattern 35A includes a tip 36A facing pattern 31A, a tip 37A facing pattern 32A, a tip 38A facing pattern 33A, a tip 39A facing pattern 34A, a tip 96A facing pattern 81A, and a tip 97A facing pattern 82A. In this modified example, each linear portion 91 includes tip 36A and tip 37A, each linear portion 92 includes tip 38A and tip 39A, and each linear portion 95 includes tip 96A and tip 97A.

[0122] Tips 36A and 37A correspond to tips 36 and 37 described above, respectively. Tips 38A and 39A correspond to tips 38 and 39 described above, respectively. Tip 36A is included in the linear section 91a. Tip 37A is included in the linear section 91b. Tips 36A and 37A are located at both ends of each linear section 91. Tip 38A is included in the linear section 92a. Tip 39A is included in the linear section 92b. Tips 38A and 39A are located at both ends of each linear section 92.

[0123] The tip 96A faces the bias portion β3. The tip 96A faces the corresponding linear portion 86A. The tip 96A is the portion of the linear portion 95 that includes the tip 96A that is closest to the pattern 81A. The tip 96A is positioned closer to the corresponding linear portion 86A than other portions of the pattern 35A.

[0124] The tip 97A faces the bias portion β3. The tip 97A faces the corresponding linear portion 88A. The tip 97A is the portion of the linear portion 95 that includes the tip 97A that is closest to the pattern 82A. The tip 97A is positioned closer to the corresponding linear portion 88A than other portions of the pattern 35A.

[0125] The tips 96A and 97A, and the linear portions 86A and 88A are arranged in the order of linear portion 86A, tip 96A, tip 97A, and linear portion 88A in the γ1 axis direction. In the photoelectric conversion unit 25, each linear portion 95 can emit electrons P in response to the incidence of electromagnetic waves W when a lower potential than that of linear portion 86A or linear portion 88A is applied.

[0126] The photoelectric conversion unit 25A is configured to correspond to wavelength ranges ranging from so-called millimeter waves to infrared light, depending on the structural changes of the linear sections 91, 92, and 95. For example, the length of the linear section 95 in the γ1 axis direction corresponds to the wavelength range of the electromagnetic wave W from which electrons P are emitted in the photoelectric conversion unit 25A. For example, the length of the linear section 95 in the γ1 axis direction is designed according to a desired wavelength range from which electrons P are emitted from the photoelectric conversion unit 25A. For example, each linear section 91, 92, and 95 has a length of half the central wavelength in the desired wavelength range. The length of each linear section 91 is from tip 36A to tip 37A in the Z axis direction. The length of each linear section 92 is from tip 38A to tip 39A in the Y axis direction. The length of each linear section 95 is from tip 96A to tip 97A in the γ1 axis direction. Similar to the linear portions 51 and 52, when electromagnetic waves W that have passed through the support 21 etc. are incident on the linear portions 91, 92, and 95, the refractive index of the transmitted support 21 etc. is also taken into consideration.

[0127] The electron-emitting member 20 shown in Figure 8 further comprises a plurality of electrodes 61A, 62A, 63A, 64A, 65A, 67A, and 68A spaced apart from each other. The plurality of electrodes 61A, 62A, 63A, 64A, 65A, 67A, and 68A are provided on the main surface 21b of the support 21. The plurality of electrodes 61A, 62A, 63A, 64A, 65A, 67A, and 68A are electrically connected to the photoelectric conversion unit 25A. In this modified example, each electrode 61A, 62A, 63A, 64A, 65A, 67A, and 68A has a rectangular shape. Each electrode 61A, 62A, 63A, 64A, 65A, 67A, and 68A may also have a linear shape similar to the linear portion 42A, 44A, 47A, 49A, 87A, or 89A.

[0128] For example, electrode 61A is included in pattern 31A. Electrode 61A is electrically connected to a plurality of linear portions 41A via a linear portion 42A. Electrode 61A may be formed integrally with the linear portion 42A and the plurality of linear portions 41A. Electrode 62A is included in pattern 32A. Electrode 62A is electrically connected to a plurality of linear portions 43A via a linear portion 44A. Electrode 62A may be formed integrally with the linear portion 44A and the plurality of linear portions 43A. Electrode 63A is included in pattern 33A. Electrode 63A is electrically connected to a plurality of linear portions 46A via a linear portion 47A. Electrode 63A may be formed integrally with the linear portion 47A and the plurality of linear portions 46A.

[0129] Electrode 64A is included in pattern 34A. Electrode 64A is electrically connected to a plurality of wire-shaped portions 48A via wire-shaped portion 49A. Electrode 64A may be formed integrally with wire-shaped portion 49A and the plurality of wire-shaped portions 48A. Electrode 65A is included in pattern 35A. Electrode 65A is electrically connected to a plurality of wire-shaped portions 91, 92, 95 via wire-shaped portion 93. Electrode 65A may be formed integrally with wire-shaped portion 93 and the plurality of wire-shaped portions 91, 92, 95. Electrode 67A is included in pattern 81A. Electrode 67A is electrically connected to a plurality of wire-shaped portions 86A via wire-shaped portion 87A. Electrode 67A may be formed integrally with wire-shaped portion 87A and the plurality of wire-shaped portions 86A. Electrode 68A is included in pattern 82A. The electrode 68A is electrically connected to a plurality of wire-shaped portions 88A via a wire-shaped portion 89A. The electrode 68A may be formed integrally with the wire-shaped portion 89A and the plurality of wire-shaped portions 88A.

[0130] The photoelectric conversion unit 25A operates by receiving a potential from the power supply unit 70 via multiple electrodes 61A, 62A, 63A, 64A, 65A, 67A, and 68A. The potential application unit 71 of the power supply unit 70 applies a potential to the photoelectric conversion unit 25A of the metasurface 22A via the multiple electrodes 61A, 62A, 63A, 64A, 65A, 67A, and 68A. The potential control unit 72 of the power supply unit 70 controls the potential applied to the photoelectric conversion unit 25A.

[0131] In the photoelectric converter 2 equipped with the electron-emitting member 20 in this modified example, the potential control unit 72 switches between the first and second states, the third and fourth states, and the fifth and sixth states by controlling the potential applied to a plurality of patterns 31A, 32A, 33A, 34A, 35A, 81A, and 82A. In the first state, the potential is controlled so that electrons P are emitted from the tip 37A of the antenna part α1 in response to the incidence of electromagnetic waves W, and the emission of electrons from the tip 36A of the antenna part α1, as well as from the antenna parts α2 and α3, is suppressed. In the second state, the potential is controlled so that electrons P are emitted from the tip 36A of the antenna part α1 in response to the incidence of electromagnetic waves W, and the emission of electrons from the tip 37A of the antenna part α1, as well as from the antenna parts α2 and α3, is suppressed. In the third state, the potential is controlled such that electrons P are emitted from the tip 39A of antenna section α2 in response to the incidence of electromagnetic waves W, while the emission of electrons from the tip 38A of antenna section α2, as well as from antenna sections α1 and α3, is suppressed. In the fourth state, the potential is controlled such that electrons P are emitted from the tip 38A of antenna section α2 in response to the incidence of electromagnetic waves W, while the emission of electrons from the tip 39A of antenna section α2, as well as from antenna sections α1 and α3, is suppressed.

[0132] In the fifth state, the potential is controlled such that electrons P are emitted from the tip 96A of antenna section α3 in response to the incidence of electromagnetic waves W, while the emission of electrons from the tip 97A of antenna section α3, antenna section α1, and antenna section α2 is suppressed. In the sixth state, the potential is controlled such that electrons P are emitted from the tip 97A of antenna section α3 in response to the incidence of electromagnetic waves W, while the emission of electrons from the tip 96A of antenna section α3, antenna section α1, and antenna section α2 is suppressed.

[0133] In the fifth state, the potential applied to pattern 35A is lower than the potential applied to patterns 31A, 32A, 33A, 34A, and 81A, and higher than the potential applied to pattern 82A. In other words, the potential applied to the linear portion 88A constituting the bias section β3 is higher than the potential applied to the linear portion 95b constituting the antenna section α3. The potential applied to the linear portion 86A constituting the bias section β3 is lower than the potential applied to the linear portion 95a constituting the antenna section α3. In the fifth state, the component of the electric field in the γ1 axis direction from the tip 96A of the linear portion 95a constituting the antenna section α3 toward the linear portion 86A constituting the bias section β3 is negative, and the component of the electric field in the γ1 axis direction from the linear portion 88A constituting the bias section β3 toward the tip 97A of the linear portion 95b constituting the antenna section α3 is negative.

[0134] In the sixth state, the potential applied to pattern 35A is lower than the potential applied to patterns 31A, 32A, 33A, 34A, and 82A, and higher than the potential applied to pattern 81A. In other words, the potential applied to the linear portion 88A constituting the bias section β3 is lower than the potential applied to the linear portion 95b constituting the antenna section α3. The potential applied to the linear portion 86A constituting the bias section β3 is higher than the potential applied to the linear portion 95a constituting the antenna section α3. In the sixth state, the component of the electric field in the γ1 axis direction from the tip 97A of the linear portion 95b constituting the antenna section α3 toward the linear portion 88A constituting the bias section β3 is positive, and the component of the electric field in the γ1 axis direction from the linear portion 86A constituting the bias section β3 toward the tip 96A of the linear portion 95a constituting the antenna section α3 is positive.

[0135] In this modified example, the calculation unit 75 calculates polarization information of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the first, second, third, fourth, fifth, and sixth states. For example, the calculation unit 75 calculates the first information, second information, third information, and fourth information, similar to the embodiment described above. Based on the detection results of the electron collection unit 50 in the fifth state, the calculation unit 75 calculates fifth information relating to the negative component of the electric field strength of the electromagnetic wave W in the γ1 axis direction. Based on the detection results of the electron collection unit 50 in the sixth state, the calculation unit 75 calculates sixth information relating to the positive component of the electric field strength of the electromagnetic wave W in the γ1 axis direction. Based on the first information, second information, third information, fourth information, fifth information, and sixth information, the calculation unit 75 calculates polarization information of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20.

[0136] Similar to the embodiments described above, the calculation unit 75 calculates the electric field strength in the Z-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the first and second states. The calculation unit 75 determines the polarity in the Z-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the first and second states. Similar to the embodiments described above, the calculation unit 75 calculates the electric field strength in the Y-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the third and fourth states. The calculation unit 75 determines the polarity in the Y-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the third and fourth states. The calculation unit 75 calculates the electric field strength in the γ1-axis direction of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 based on the detection results of the electron collection unit 50 in the fifth and sixth states. The calculation unit 75 determines the polarity of the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 in the γ1 axis direction based on the detection results of the electron collection unit 50 in the fifth and sixth states. For example, the calculation unit 75 determines the polarity of the electric field in the Y axis direction by comparing the detection results of the electron collection unit 50 in the fifth state with the detection results of the electron collection unit 50 in the sixth state. The calculation unit 75 calculates the polarization information of the electromagnetic wave W incident on the electron-emitting member 20 based on the electric field strength in the Z axis direction component, the electric field strength in the Y axis direction component, and the electric field strength in the γ1 axis direction component. For example, the calculation unit 75 determines whether the electromagnetic wave incident on the electron-emitting member 20 is linearly polarized, circularly polarized, or elliptically polarized by comparing the electric field strength in the Z axis direction component, the electric field strength in the Y axis direction component, and the electric field strength in the γ1 axis direction component. The calculation unit 75 determines the polarization direction of the electromagnetic wave W incident on the electron-emitting member 20.

[0137] Next, with reference to Figure 9, another modified example of the electron emission member will be described. Figure 9 is a plan view of the electron emission member in the modified example of this embodiment. This modified example is generally similar to or the same as the embodiment described above and the modified example shown in Figure 8. The electron emission member 20 in this modified example differs from the modified example shown in Figure 8 in that only one electrode is connected to each of the bias portions β1, β2, and β3. The differences from the modified example shown in Figure 8 will be mainly described below.

[0138] The electron-emitting member 20 shown in Figure 9 comprises a plurality of electrodes 61B, 63B, 65A, and 67B spaced apart from each other. The plurality of electrodes 61B, 63B, 65A, and 67B are provided on the main surface 21b of the support 21. The plurality of electrodes 61B, 63B, 65A, and 67B are electrically connected to the photoelectric conversion unit 25A. In this modified example, each electrode 61B, 63B, 65A, and 67B has a rectangular shape. Each electrode 61B, 63B, 65A, and 67B may also have a linear shape similar to the linear portions 42A, 44A, 47A, 49A, 87A, or 89A.

[0139] For example, electrode 61B is included in pattern 31B. Electrode 61B is electrically connected to a plurality of linear portions 41A via a linear portion 42A. Electrode 61B is electrically connected to a plurality of linear portions 43A via a linear portion 44A. Electrode 61B may be formed integrally with the linear portions 42A, 44A, and the plurality of linear portions 41A, 43A. Electrode 63B is included in pattern 33B. Electrode 63B is electrically connected to a plurality of linear portions 46A via a linear portion 47A. Electrode 63B is electrically connected to a plurality of linear portions 48A via a linear portion 49A. Electrode 63B may be formed integrally with the linear portions 47A, 49A, and the plurality of linear portions 46A, 48A. Electrode 65A is included in pattern 35B. Electrode 65A is electrically connected to a plurality of wire-shaped portions 91, 92, and 95 via a wire-shaped portion 93. Electrode 65A may be formed integrally with the wire-shaped portion 93 and the plurality of wire-shaped portions 91, 92, and 95. Electrode 67B is included in pattern 81B. Electrode 67B is electrically connected to a plurality of wire-shaped portions 86A via a wire-shaped portion 87A. Electrode 67B is electrically connected to a plurality of wire-shaped portions 88A via a wire-shaped portion 89A. Electrode 67B may be formed integrally with the wire-shaped portions 87A, 89A, and the plurality of wire-shaped portions 86A and 88A.

[0140] The photoelectric conversion unit 25A operates by receiving a potential from the power supply unit 70 via multiple electrodes 61B, 63B, 65A, and 67B. The potential application unit 71 of the power supply unit 70 applies a potential to the photoelectric conversion unit 25A via the multiple electrodes 61B, 63B, 65A, and 67B. The potential control unit 72 of the power supply unit 70 controls the potential applied to the photoelectric conversion unit 25A.

[0141] In the photoelectric converter 2 equipped with the electron-emitting member 20 in this modified example, the potential control unit 72 switches between the seventh, eighth, and ninth states by controlling the potential applied to a plurality of patterns 31B, 33B, 35B, and 36B. In the seventh state, the potential is controlled so that electrons P are emitted from the tips 36A and 37A of the antenna part α1 in response to the incidence of electromagnetic waves W, while the emission of electrons from antenna parts α2 and α3 is suppressed. In the eighth state, the potential is controlled so that electrons P are emitted from the tips 38A and 39A of the antenna part α2 in response to the incidence of electromagnetic waves W, while the emission of electrons from antenna parts α1 and α3 is suppressed. In the ninth state, the potential is controlled so that electrons P are emitted from the tips 96A and 97A of the antenna part α3 in response to the incidence of electromagnetic waves W, while the emission of electrons from antenna parts α1 and α2 is suppressed.

[0142] In the seventh state, the potential applied to pattern 35B is lower than the potential applied to pattern 31B, and higher than the potential applied to patterns 33B and 81B. In other words, the potential applied to bias section β1, which is composed of linear sections 41A and 43A, is higher than the potential applied to antenna section α1, which is composed of linear sections 91a and 91b. In the seventh state, the component of the electric field in the Z-axis direction from bias section β1, which is composed of linear section 41A, toward the tip 36A of linear section 91a is negative, and the component of the electric field in the Z-axis direction from bias section β1, which is composed of linear section 43A, toward the tip 37A of linear section 91b is positive.

[0143] In the eighth state, the potential applied to pattern 35B is lower than the potential applied to pattern 33B, and higher than the potential applied to patterns 31B and 81B. In other words, the potential applied to bias section β2, which is composed of linear sections 46A and 48A, is higher than the potential applied to antenna section α2, which is composed of linear sections 92a and 92b. In the eighth state, the Y-axis component of the electric field from bias section β2, which is composed of linear section 46A, toward the tip 38A of linear section 92a is negative, and the Y-axis component of the electric field from bias section β2, which is composed of linear section 48A, toward the tip 39A of linear section 92b is positive.

[0144] In the ninth state, the potential applied to pattern 35B is lower than the potential applied to pattern 81B, and higher than the potential applied to patterns 31B and 33B. In other words, the potential applied to bias section β3, which is composed of linear sections 86A and 88A, is higher than the potential applied to antenna section α3, which is composed of linear sections 95a and 95b. In the ninth state, the component of the electric field in the γ1 axis direction from bias section β3, which is composed of linear section 86A, toward the tip 96A of linear section 95a is positive, and the component of the electric field in the γ1 axis direction from bias section β3, which is composed of linear section 88A, toward the tip 97A of linear section 95b is negative.

[0145] In this modified example, the calculation unit 75 calculates the electric field strength in the Z-axis direction for the electromagnetic wave W incident on the electron-emitting member 20 based on the detection result of the electron collection unit 50 in the seventh state. The calculation unit 75 calculates the electric field strength in the Y-axis direction for the electromagnetic wave W incident on the electron-emitting member 20 based on the detection result of the electron collection unit 50 in the eighth state. The calculation unit 75 calculates the electric field strength in the γ1-axis direction for the electromagnetic wave W incident on the electron-emitting member 20 based on the detection result of the electron collection unit 50 in the ninth state. The calculation unit 75 calculates the polarization information of the electromagnetic wave W incident on the electron-emitting member 20 based on the electric field strength in the Z-axis direction, the electric field strength in the Y-axis direction, and the electric field strength in the γ1-axis direction. For example, the calculation unit 75 determines whether the electromagnetic wave W incident on the electron-emitting member 20 is circularly polarized or elliptically polarized by comparing the electric field strength in the Z-axis direction, the electric field strength in the Y-axis direction, and the electric field strength in the γ1-axis direction.

[0146] Next, the structure of the pattern in yet another modification of this embodiment will be described in detail with reference to Figures 10(a) and 10(b). Figures 10(a) and 10(b) are diagrams showing the structure of the pattern in yet another modification of this embodiment. Figures 10(a) and 10(b) show parts of patterns 31, 32, and 35. Figures 10(a) and 10(b) show modified structures relating to the linear parts 41 and 44 constituting the bias section β1 and the linear part 51 constituting the antenna section α1 as an example of the configuration of the bias section and the antenna section, but similar configurations may be applied to the bias sections β2 and β3 and the antenna sections α2 and α3.

[0147] In the examples shown in Figures 10(a) and 10(b), a pair of spaced-apart linear portions 41 face a linear portion 51. Each pair of linear portions 41 includes a tip 101 and a tip 102. The tips 101 and 102 of the pair of linear portions 41 face each other. Each linear portion 41 is electrically connected to the electrode 61 via a linear portion 42, similar to the embodiments described above. The pair of linear portions 41 are located on the same straight line extending in the Y-axis direction.

[0148] In the examples shown in Figures 10(a) and 10(b), a pair of spaced-apart linear portions 43 face a linear portion 51. Each pair of linear portions 43 includes a tip 103 and a tip 104. The tips 103 and 104 of the pair of linear portions 43 face each other. Each linear portion 43 is electrically connected to the electrode 62 via a linear portion 44, similar to the embodiments described above. The pair of linear portions 43 are located on the same straight line extending in the Y-axis direction.

[0149] In the examples shown in Figures 10(a) and 10(b), the linear portion 51 extends in the +Z-axis direction and the -Z-axis direction from the portion connected to the linear portion 53. The linear portion 51 includes a pair of linear portions 51a and 51b, similar to the embodiments described above. The linear portion 51a extends in the +Z-axis direction from the portion connected to the linear portion 53. The linear portion 51b extends in the -Z-axis direction from the portion connected to the linear portion 53.

[0150] The tip 36 of the linear portion 51a faces the tips 101 and 102. In the Z-axis direction, the tip 36 of the linear portion 51 is located between the tips 101 and 102. The shortest distance between tip 36 and tip 101 is equal to the shortest distance between tip 36 and tip 102. The distance between tip 36 and tip 101 in the Y-axis direction is equal to the distance between tip 36 and tip 102 in the Y-axis direction. The distance between tip 36 and tip 101 in the Z-axis direction is equal to the distance between tip 36 and tip 102 in the Z-axis direction. Tips 101 and 102, which face the same tip 36, are contained within different linear portions 41.

[0151] The tip 37 of the linear portion 51b faces the tips 103 and 104. In the Z-axis direction, the tip 37 of the linear portion 51 is located between the tips 103 and 104. The shortest distance between tip 37 and tip 103 is equal to the shortest distance between tip 37 and tip 104. The distance between tip 37 and tip 103 in the Y-axis direction is equal to the distance between tip 37 and tip 104 in the Y-axis direction. The distance between tip 37 and tip 103 in the Z-axis direction is equal to the distance between tip 37 and tip 104 in the Z-axis direction. Tips 103 and 104, which face the same tip 37, are contained within different linear portions 43.

[0152] In the example shown in Figure 10(a), the pair of linear sections 51a and 51b in the linear section 51 are arranged on the same straight line extending in the Z-axis direction. In the example shown in Figure 10(b), the pair of linear sections 51a and 51b in the linear section 51 are spaced apart from each other and are arranged on different straight lines extending in the Z-axis direction. In the example shown in Figure 10(b), the linear section 51a is connected to the linear section 53 at the end 111 opposite to the end 36, and the linear section 51b is connected to the linear section 53 at the end 112 opposite to the end 37.

[0153] Similar to the embodiments described above, the length of the linear portion 51 in the Z-axis direction is designed according to the desired wavelength range in which electrons P are emitted from the photoelectric conversion unit 25. In the example shown in Figure 10(a), the linear portion 51 has a length of half the central wavelength in the desired wavelength range. Therefore, in the example shown in Figure 10(a), the length L1 from tip 36 to tip 37 in the Z-axis direction is half the length of the central wavelength in the desired wavelength range. When electromagnetic waves W transmitted through the support 21 etc. are incident on the linear portion 51, the refractive index of the transmitted support 21 etc. is taken into consideration.

[0154] In the example shown in Figure 10(b), each of the linear portions 51a and 51b has a length of half the central wavelength in the desired wavelength range. Therefore, in the example shown in Figure 10(b), the length L2 from tip 36 to tip 111 in the Z-axis direction and the length L3 from tip 37 to tip 112 in the Z-axis direction are each half the central wavelength in the desired wavelength range. In this case as well, when electromagnetic waves W transmitted through the support 21 etc. are incident on the linear portions 51a and 51b, the refractive index of the transmitted support 21 etc. is taken into consideration. [Photoelectric conversion method]

[0155] Next, the electromagnetic wave detection method in this embodiment will be described with reference to Figures 11 and 12. This electromagnetic wave detection method includes a photoelectric conversion method that emits electrons in response to the incident electromagnetic wave W. Figures 11 and 12 are flowcharts of the electromagnetic wave detection method in this embodiment. In the electromagnetic wave detection method shown in Figures 11 and 12, by controlling the state of the potential applied to the metasurface 22, electrons P are emitted from the metasurface 22 at different timings for each directional component of the electric field strength of the electromagnetic wave W incident on the electron emission member 20. As a result, the electric field strength of the electromagnetic wave W incident on the electron emission member 20 is measured for each directional component. In the configuration shown in Figures 3 and 8, by controlling the state of the potential applied to the metasurface 22, electrons P are emitted from the metasurface 22 at different timings for each polarity of each directional component of the electric field strength of the electromagnetic wave W incident on the electron emission member 20. As a result, the electric field strength of the electromagnetic wave W incident on the electron emission member 20 is measured for each polarity of each directional component.

[0156] Referring to Figure 11, the outline of the electromagnetic wave detection method in this embodiment will be described. First, the electron emission member 20 is prepared (process S1). For example, an electromagnetic wave detection device 1 equipped with the electron emission member 20 is positioned.

[0157] Next, the electromagnetic wave W to be measured is incident on the electron emission member 20 (process S2). In this embodiment, in process S2, the incident of electromagnetic wave W on the electron emission member 20 is started and continues until the detection of electromagnetic wave W is completed.

[0158] Next, the process of acquiring the electric field strength in each directional component is executed (process S3). In process S3, the calculation unit 75 calculates the electric field strength in each directional component.

[0159] Next, the polarization information of the electromagnetic wave W incident on the electron-emitting member 20 is calculated (processing S4). In processing S4, the calculation unit 75 calculates the polarization information of the electromagnetic wave W incident on the electron-emitting member 20. For example, the calculation unit 75 compares the information on the electric field strength of each directional component obtained in processing S3 and calculates the polarization information of the electromagnetic wave W incident on the electron-emitting member 20. For example, the calculation unit 75 compares the calculated electric field strength of each directional component and outputs the polarization direction of the electromagnetic wave W incident on the electron-emitting member 20.

[0160] Next, we will explain process S3 in detail with reference to Figure 12. Figure 12 shows the flow of the process for acquiring electric field strength in each directional component.

[0161] First, the potential to be applied to each pattern is determined (process S11). In this embodiment, the potential control unit 72 determines the potential to be applied to each pattern 31, 32, 33, 34, 35 so that it is in one of the first, second, third, and fourth states. For example, in the configuration shown in Figure 8, the potential control unit 72 determines the potential to be applied to each pattern 31A, 32A, 33A, 34A, 35A, 81A, 82A so that it is in one of the first to sixth states.

[0162] Next, an electric potential is applied to each pattern (process S12). For example, the electric potential application unit 71 applies an electric potential to each pattern via electrodes according to instructions from the electric potential control unit 72. For example, the electric potential application unit 71 applies the electric potential determined in the previous process S11 to each pattern 31, 32, 33, 34, and 35. The electric potential application unit 71 applies the electric potential determined in the previous process S11 to each pattern until at least processes S13 and S14 are completed.

[0163] Next, with an electric potential applied to each pattern, electrons are emitted from the metasurface (process S13). For example, when the electromagnetic wave W to be measured is incident on the metasurface 22, with the electric potential determined in the preceding process S11 applied to each pattern 31, 32, 33, 34, and 35, the electron-emitting member 20 emits electrons P from either the tip of antenna section α1 or antenna section α2. Which tip of antenna section α1 or antenna section α2 emits electrons P depends on how the electric potential is applied to each pattern in process S12. For example, if the electric potential applied to each pattern is in the first state, electrons P are emitted from the tip 37 of antenna section α1. If the electric potential applied to each pattern is in the second state, electrons P are emitted from the tip 36 of antenna section α1. If the electric potential applied to each pattern is in the third state, electrons P are emitted from the tip 39 of antenna section α2. If the potential state applied to each pattern is the fourth state, electrons P are emitted from the tip 38 of the antenna section α2.

[0164] For example, in the configuration shown in Figure 8, the electron-emitting member 20 emits electrons P from one of the tips of antenna section α1, antenna section α2, or antenna section α3 when the potential determined in the preceding process S11 is applied to each pattern 31A, 32A, 33A, 34A, 35A, 81A, 82A. In this case, if the potential applied to each pattern is in the first state, electrons P are emitted from the tip 37A of antenna section α1. If the potential applied to each pattern is in the second state, electrons P are emitted from the tip 36A of antenna section α1. If the potential applied to each pattern is in the third state, electrons P are emitted from the tip 39A of antenna section α2. If the potential applied to each pattern is in the fourth state, electrons P are emitted from the tip 38A of antenna section α2. If the potential applied to each pattern is in the fifth state, electrons P are emitted from the tip 97A of antenna section α3. If the potential state assigned to each pattern is the sixth state, electron P is emitted from the tip 96A of antenna section α3.

[0165] Next, the emitted electrons P are detected (process S14). For example, the electron collection unit 50 collects the electrons P emitted in process S13 and detects the collected electrons P. The calculation unit 75 acquires the signal output from the electron collection unit 50.

[0166] Next, information regarding the electric field strength is calculated (process S15). For example, the calculation unit 75 calculates information regarding the electric field strength of the electromagnetic wave W based on the signal acquired from the electron collection unit 50 in process S14. For example, if the potential state applied to each pattern in processes S13 and S14 is the first state, the calculation unit 75 calculates first information regarding the positive Z-axis component of the electric field strength of the electromagnetic wave W.

[0167] Next, it is determined whether or not information regarding the electric field strength of the positive and negative coaxial components has been obtained (process S16). For example, the calculation unit 75 determines whether or not information regarding the electric field strength of both the positive and negative coaxial components has been obtained for the directional component of the electric field strength calculated in the previous process S15. For example, if the calculation unit 75 determined that information regarding the positive Z-axis component of the electric field strength had been calculated in the previous process S15, it determined that information regarding the negative Z-axis component of the electric field strength had not been obtained. For example, if the potential state applied to each pattern in the previous processes S13 and S14 is the first state, the calculation unit 75 determined that information for the second state, i.e., second information regarding the negative Z-axis component of the electric field strength, had not been obtained.

[0168] If it is determined that information regarding the electric field strength of the positive and negative coaxial components has not been obtained, the process returns to process S11. In this case, in process S11, the potential to be applied to each pattern is determined so that information regarding the electric field strength of the polarity that has not been obtained is obtained. For example, if it is determined in process S16 that the first information has been obtained but the second information has not been obtained, the potential control unit 72 determines in process S11 the potential to be applied to each pattern 31, 32, 33, 34, 35 so that it reaches the second state. For example, if it is determined in process S16 that the third information has been obtained but the fourth information has not been obtained, the potential control unit 72 determines in process S11 the potential to be applied to each pattern 31, 32, 33, 34, 35 so that it reaches the fourth state.

[0169] If it is determined that information regarding the positive and negative components of the electric field strength has been obtained, the polarity of the electric field is determined (processing S17). For example, the calculation unit 75 determines the polarity of the electric field in the Z-axis direction of the electromagnetic wave W based on the first and second pieces of information. The calculation unit 75 determines the polarity of the electric field in the Y-axis direction of the electromagnetic wave W based on the third and fourth pieces of information. In the configuration shown in Figure 8, the calculation unit 75 determines the polarity of the electric field in the γ1-axis direction of the electromagnetic wave W based on the fifth and sixth pieces of information. The polarity of the electric field of the electromagnetic wave W switches, for example, on a femtosecond order. Therefore, for example, if the first and second pieces of information are obtained on a femtosecond order, the calculation unit 75 outputs the larger of the positive Z-axis component of the electric field strength of the electromagnetic wave W and the negative Z-axis component of the electric field strength of the electromagnetic wave W as the polarity of the electric field in the Z-axis direction. When the third and fourth pieces of information are acquired on a femtosecond order, the calculation unit 75 outputs the larger of the positive Y-axis component of the electric field strength of the electromagnetic wave W and the negative Y-axis component of the electric field strength of the electromagnetic wave W as the polarity of the electric field in the Y-axis direction. The first, second, third, and fourth pieces of information can be acquired on a picosecond order. The information acquisition time depends on the time waveform of the electromagnetic wave W.

[0170] When processing S17 is completed, it is determined whether or not information regarding the electric field strength for all directional components has been acquired (processing S18). For example, the calculation unit 75 determines whether or not the first and second information regarding the electric field strength for the Z-axis direction component and the third and fourth information regarding the electric field strength for the Y-axis direction component have been acquired. In the configuration shown in Figure 8, the calculation unit 75 determines whether or not the first and second information regarding the electric field strength for the Z-axis direction component, the third and fourth information regarding the electric field strength for the Y-axis direction component and the fifth and sixth information regarding the electric field strength for the Z-axis direction component have been acquired.

[0171] If it is determined that information regarding the electric field strength for all directional components has not been obtained, the process returns to process S11. In this case, in process S11, the potential to be applied to each pattern is determined so that information regarding the electric field strength for the directional components that have not yet been obtained is acquired. For example, if it is determined in process S18 that information regarding the electric field strength for the Y-axis component has not been obtained, the potential control unit 72 determines in process S11 the potential to be applied to each pattern 31, 32, 33, 34, 35 so that it reaches the third or fourth state. In the configuration shown in Figure 8, for example, if it is determined in process S18 that information regarding the electric field strength for the γ1-axis component has not been obtained, the potential control unit 72 determines in process S11 the potential to be applied to each pattern 31A, 32A, 33A, 34A, 35A, 81A, 82A so that it reaches the fifth or sixth state.

[0172] If it is determined that information regarding the electric field strength for all directional components has been obtained, the series of processes in process S3 is terminated. Processes S11 to S17 are repeated by process S18 until information regarding the electric field strength for all directional components has been obtained. By repeating processes S11 to S14, electrons P are emitted in each of the first to fourth states described above. In this embodiment, by repeating processes S11 to S14, potential is applied to each pattern in the order of the first state, second state, third state, and fourth state. In the configuration shown in Figure 8, by repeating processes S11 to S14, potential is applied to each pattern in the order of the first state, second state, third state, fourth state, fifth state, and sixth state.

[0173] As process S15 is repeated, electrons P emitted in each of the first to fourth states are detected. In the configuration shown in Figure 8, as processes S11 to S14 are repeated, electrons P are emitted in each of the first to sixth states described above, and as process S15 is repeated, electrons P emitted in each of the first to sixth states are detected. As process S17 is repeated, the polarity of the electric field in each direction is determined.

[0174] The order of processes S1 to S4 and S11 to S18 is not limited to those shown in Figures 11 and 12. For example, process S17 may be performed after process S18. Processes S16 and S17 are optional. If process S16 is omitted, process S18 determines whether or not information regarding the electric field strength has been obtained for all states. For example, the incidence of electromagnetic wave W in process S2 may be performed only in processes S13 and S14.

[0175] As described above, in the electromagnetic wave detection method of this embodiment, electrons P emitted from the electron-emitting member 20 are detected in each state, and polarization information of the electromagnetic wave W is calculated. For example, the calculation unit 75 calculates information from the first to the fourth information, and calculates the polarization information of the electromagnetic wave W incident on the electron-emitting member 20 based on the information from the first to the fourth information. In the configuration shown in Figure 8, the calculation unit 75 calculates information from the first to the sixth information, and calculates the polarization information of the electromagnetic wave W incident on the electron-emitting member 20 based on the information from the first to the sixth information. [Mechanism of Action and Effects]

[0176] In this photoelectric converter 2, antenna sections α1 and α2 extend in the Z-axis and Y-axis directions, respectively, where they intersect. Bias section β1 is configured to generate an electric field having a component in the Z-axis direction between bias section β1 and antenna section α1. Bias section β2 is configured to generate an electric field having a component in the Y-axis direction between bias section β2 and antenna section α2. With this configuration, antenna section α1 emits electrons P in accordance with the Z-axis component of the electric field strength of the electromagnetic wave W. Antenna section α2 emits electrons P in accordance with the Y-axis component of the electric field strength of the electromagnetic wave W. Therefore, electrons P emitted in accordance with the Z-axis component of the electric field strength of the electromagnetic wave W and electrons P emitted in accordance with the Y-axis component of the electric field strength of the electromagnetic wave W can be detected. For example, based on these detection results, the ratio of the Z-axis component of the electric field strength of the electromagnetic wave W to the Y-axis component can be calculated. The polarization state of the electromagnetic wave W can be easily detected using the calculated ratio. The photoelectric converter 2 does not require cooling.

[0177] The photoelectric converter 2 further includes a potential control unit 72 that controls the potential applied to the metasurface 22 or metasurface 22A. For example, the potential control unit 72 switches between the first and second states, and between the third and fourth states, by controlling the potential applied to multiple patterns 31, 32, 33, 34, and 35 of the metasurface 22. In this case, when an electromagnetic wave W is incident on the metasurface 22 or metasurface 22A in the first state, electrons P corresponding to the positive component in the Z-axis direction of the electric field strength of the electromagnetic wave W are emitted from the antenna unit α1. When an electromagnetic wave W is incident on the metasurface 22 or metasurface 22A in the second state, electrons P corresponding to the negative component in the Z-axis direction of the electric field strength of the electromagnetic wave W are emitted from the antenna unit α1. When an electromagnetic wave W is incident on the metasurface 22 or metasurface 22A in the third state, electrons P corresponding to the positive component in the Y-axis direction of the electric field strength of the electromagnetic wave W are emitted from the antenna unit α2. In the fourth state, when an electromagnetic wave W is incident on the metasurface 22 or metasurface 22A, electrons P corresponding to the negative component of the electromagnetic wave W's electric field strength in the Y-axis direction are emitted from the antenna section α2. Therefore, the photoelectric converter 2 can measure the electric field strength of the electromagnetic wave W for each polarity in the Z-axis direction by detecting the electrons P emitted from the metasurface 22 or metasurface 22A in the first and second states. Similarly, in the third and fourth states, the detection of electrons P emitted from the metasurface 22 or metasurface 22A can enable measurement of the electric field strength of the electromagnetic wave W for each polarity in the Y-axis direction. As a result, the polarization state of the electromagnetic wave W can be detected more accurately by considering the polarity of each directional component.

[0178] In the photoelectric conversion device 2, the calculation unit 75 determines the polarity of the electric field in each axial direction of the electric field strength of the electromagnetic wave W. Therefore, in addition to the polarization state of the electromagnetic wave W, more detailed information about the electromagnetic wave W is obtained. For example, electric field waveform data of the electromagnetic wave W may be obtained.

[0179] In the configuration shown in Figure 8, the metasurface 22A further includes an antenna section α3 and a bias section β3. The antenna section α3 extends in the γ1 axis direction intersecting the Y axis direction and the Z axis direction, and emits electrons P in response to the incidence of electromagnetic waves W. The bias section β3 faces the antenna section α3 and is configured to generate an electric field having a component in the γ1 axis direction between itself and the antenna section α3. With this configuration, the antenna section α3 emits electrons P in accordance with the component of the electric field strength of the electromagnetic wave W in the γ1 axis direction. In this case, the electrons P emitted in accordance with the component of the electric field strength of the electromagnetic wave W in the γ1 axis direction can be detected. Therefore, for example, the ratio of the component of the electric field strength of the electromagnetic wave W in the Z axis direction, the component of the electric field strength of the electromagnetic wave W in the Y axis direction, and the component of the electric field strength of the electromagnetic wave W in the γ1 axis direction can be calculated. Using the calculated ratio, the detection of the polarization state of the electromagnetic wave W can be more easily realized by simpler calculation processing. For the electromagnetic wave W, the polarization state, including circular polarization, can be detected.

[0180] In the configuration shown in Figure 8, the potential control unit 72 may switch between the first and second states, the third and fourth states, and the fifth and sixth states by controlling the potential applied to multiple patterns 31A, 32A, 33A, 34A, 35A, 81A, and 82A of the metasurface 22A. In this case, the photoelectric conversion device 2 can measure the electric field strength of the electromagnetic wave W for each polarity in the Z-axis direction by detecting electrons P emitted from the metasurface 22A in the first and second states. Similarly, by detecting electrons P emitted from the metasurface 22A in the third and fourth states, it can measure the electric field strength of the electromagnetic wave W for each polarity in the Y-axis direction. Furthermore, by detecting electrons P emitted from the metasurface 22A in the fifth and sixth states, it can measure the electric field strength of the electromagnetic wave W for each polarity in the γ1-axis direction. As a result, the polarization state of the electromagnetic wave W can be detected more accurately by considering the polarity of each directional component.

[0181] The antenna section α1 of the metasurface 22 includes tips 36 and 37, which are positioned at different locations in the Z-axis direction. The bias section β1 includes linear sections 41 and 43. Linear section 41 faces tip 36 and generates an electric field with a component in the Z-axis direction between it and tip 36. Linear section 43 faces tip 37 and generates an electric field with a component in the Z-axis direction between it and tip 37. The antenna section α2 includes tips 38 and 39, which are positioned at different locations in the Y-axis direction. The bias section β2 includes linear sections 46 and 48. Linear section 46 faces tip 38 and generates an electric field with a component in the Y-axis direction between it and tip 38. Linear section 48 faces tip 39 and generates an electric field with a component in the Y-axis direction between it and tip 39. The tips 36 and 37, and the linear sections 41 and 43 are arranged in the Z-axis direction in the order of linear section 43, tip 37, tip 36, and linear section 41. The tips 38, 39 and the linear portions 46, 48 are arranged in the order of linear portion 48, tip 39, tip 38, and linear portion 46 in the Y-axis direction. In this case, despite the simple configuration, the detection of electrons P emitted from the metasurface 22 makes it possible to measure the electric field strength of the electromagnetic wave W incident on the electron-emitting member 20 for each polarity in both the Z-axis and Y-axis directions. The same effect is achieved in the metasurface 22A.

[0182] For example, in the first state, the component of the electric field from tip 36 toward the linear portion 41 in the Z-axis direction is positive, the component of the electric field from linear portion 43 toward tip 37 in the Z-axis direction is positive, the component of the electric field from tip 38 toward linear portion 46 in the Y-axis direction is positive, and the component of the electric field from tip 39 toward linear portion 48 in the Y-axis direction is negative. In the second state, the component of the electric field from linear portion 41 toward tip 36 in the Z-axis direction is negative, the component of the electric field from tip 37 toward linear portion 43 in the Z-axis direction is negative, the component of the electric field from tip 38 toward linear portion 46 in the Y-axis direction is positive, and the component of the electric field from tip 39 toward linear portion 48 in the Y-axis direction is negative. In the third state, the component of the electric field from tip 36 toward the linear portion 41 in the Z-axis direction is positive, the component of the electric field from tip 37 toward the linear portion 43 in the Z-axis direction is negative, the component of the electric field from tip 38 toward the linear portion 46 in the Y-axis direction is positive, and the component of the electric field from linear portion 48 toward tip 39 in the Y-axis direction is positive. In the fourth state, the component of the electric field from tip 36 toward the linear portion 41 in the Z-axis direction is positive, the component of the electric field from tip 37 toward the linear portion 43 in the Z-axis direction is negative, the component of the electric field from linear portion 46 toward tip 38 in the Y-axis direction is negative, and the component of the electric field from tip 39 toward the linear portion 48 in the Y-axis direction is negative. In this case, when electromagnetic waves W are incident on the metasurface 22 in the first state, electrons P are emitted from the antenna portion α1 in accordance with the positive component of the electric field strength of electromagnetic waves W in the Z-axis direction, and the emission of electrons in accordance with other components of the electric field strength of electromagnetic waves W is suppressed. In the second state, when electromagnetic waves W are incident on the metasurface 22, electrons P are emitted from the antenna part α1 in accordance with the negative component of the electric field strength of the electromagnetic waves W in the Z-axis direction, and the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed. In the third state, when electromagnetic waves W are incident on the metasurface 22, electrons P are emitted from the antenna part α2 in accordance with the positive component of the electric field strength of the electromagnetic waves W in the Y-axis direction, and the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed.In the fourth state, when electromagnetic waves W are incident on the metasurface 22, electrons P are emitted from the antenna section α2 in accordance with the negative component of the electric field strength of the electromagnetic waves W in the Y-axis direction, while the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed. Therefore, more accurate measurement of the polarity of each directional component can be achieved. Furthermore, detection of the polarization state of the electromagnetic waves W can be achieved more accurately. Similar effects are observed in the metasurface 22A.

[0183] For example, in the first state, the potential applied to the linear portion 41 is lower than the potential applied to the antenna portion α1, the potential applied to the linear portion 43 is higher than the potential applied to the antenna portion α1, the potential applied to the linear portion 46 is lower than the potential applied to the antenna portion α2, and the potential applied to the linear portion 48 is lower than the potential applied to the antenna portion α2. In the second state, the potential applied to the linear portion 41 is higher than the potential applied to the antenna portion α1, the potential applied to the linear portion 43 is lower than the potential applied to the antenna portion α1, the potential applied to the linear portion 46 is lower than the potential applied to the antenna portion α2, and the potential applied to the linear portion 48 is lower than the potential applied to the antenna portion α2. In the third state, the potential applied to the linear portion 41 is lower than the potential applied to the antenna portion α1, the potential applied to the linear portion 43 is lower than the potential applied to the antenna portion α1, the potential applied to the linear portion 46 is lower than the potential applied to the antenna portion α2, and the potential applied to the linear portion 48 is higher than the potential applied to the antenna portion α2. In the fourth state, the potential applied to the linear portion 41 is lower than the potential applied to the antenna portion α1, the potential applied to the linear portion 43 is lower than the potential applied to the antenna portion α1, the potential applied to the linear portion 46 is higher than the potential applied to the antenna portion α2, and the potential applied to the linear portion 48 is lower than the potential applied to the antenna portion α2. In this case, a potential difference is generated between the tip 36 and the linear portion 41, between the tip 37 and the linear portion 43, between the tip 38 and the linear portion 46, and between the tip 39 and the linear portion 48. This potential difference generates an electric field as described above. As a result, when electromagnetic waves W are incident on the metasurface 22 in the first state, electrons P are emitted from the antenna part α1 in accordance with the positive component of the electric field strength of the electromagnetic waves W in the Z-axis direction, and the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed. When electromagnetic waves W are incident on the metasurface 22 in the second state, electrons P are emitted from the antenna part α1 in accordance with the negative component of the electric field strength of the electromagnetic waves W in the Z-axis direction, and the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed.In the third state, when electromagnetic waves W are incident on the metasurface 22, electrons P are emitted from the antenna α2 in accordance with the positive component of the electric field strength of the electromagnetic waves W in the Y-axis direction, while the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed. In the fourth state, when electromagnetic waves W are incident on the metasurface 22, electrons P are emitted from the antenna α2 in accordance with the negative component of the electric field strength of the electromagnetic waves W in the Y-axis direction, while the emission of electrons in accordance with other components of the electric field strength of the electromagnetic waves W is suppressed. Therefore, more accurate measurement of the polarity of each directional component can be achieved. Furthermore, detection of the polarization state of the electromagnetic waves W can be achieved more accurately. Similar effects are observed in the metasurface 22A.

[0184] The photoelectric converter 2 further comprises a housing 10 that is hermetically sealed and has a window portion 11a that allows electromagnetic waves W to pass through. The electron emission member 20 is located inside the housing 10. In this case, the amount of electrons P emitted in response to the incidence of electromagnetic waves W can be improved by creating a vacuum inside the housing 10 or by filling the housing 10 with gas.

[0185] The electromagnetic wave detection device 1 comprises the photoelectric conversion device 2 described above, an electron collection unit 50, and a calculation unit 75. The electron collection unit 50 detects electrons P emitted from the electron emission member 20. The calculation unit 75 calculates the polarization information of the electromagnetic wave W based on the detection results of the electron collection unit 50 in the first state, the second state, the third state, and the fourth state. In this case, the electromagnetic wave detection device 1 can easily detect the polarization state of the electromagnetic wave W. The electromagnetic wave detection device 1 does not require cooling.

[0186] While embodiments and modifications of the present invention have been described above, the present invention is not necessarily limited to the embodiments described above, and various modifications are possible without departing from the spirit of the invention.

[0187] For example, the configurations of the photoelectric conversion units 25 and 25A can be combined as appropriate. Multiple types of photoelectric conversion units may be provided on a single electron-emitting member 20.

[0188] The arrangement of the various linear sections in patterns 31, 32, 33, 34, 35, patterns 31A, 32A, 33A, 34A, 35A, 81A, 82A, and patterns 31B, 33B, 81B is not limited to the configuration of the embodiments described above. The number and arrangement of the linear sections can be changed as appropriate, as long as the functional relationship between the corresponding bias section and antenna section is maintained.

[0189] For example, one linear section may be configured to serve as both an antenna section that emits electrons P in response to the incidence of electromagnetic waves W and a bias section that generates an electric field. For example, the photoelectric conversion section of the electron emission member 20 may be configured to include a pair of first and second linear sections that face each other and extend in the same direction, and to be configured to switch between a state in which the first linear section functions as an antenna section and the second linear section functions as a bias section, and a state in which the first linear section functions as a bias section and the second linear section functions as an antenna section. The tips of the pair of first and second linear sections are arranged to face each other. For example, the switching between the state in which the first and second linear sections function as an antenna section and the state in which they function as a bias section is performed by controlling the potential applied to the electrodes electrically connected to each linear section. By switching which of the first and second linear sections facing each other functions as an antenna section, it becomes possible to detect the electric field strength of the electromagnetic waves W for each polarity component in the extending direction of the pair of linear sections.

[0190] Furthermore, antenna section α1 and antenna section α2 do not have to be orthogonal to each other. The calculation unit 75 may be configured to determine the polarization state based on the electrons P emitted from antenna sections α1 and α2 that are not orthogonal to each other. [Explanation of Symbols]

[0191] 1...Electromagnetic wave detection device, 2...Photoelectric conversion device, 10...Housing, 11a...Window section, 20...Electron emission member, 22,22A...Metasurface, 72...Potential control section, 75...Calculation unit, P...Electron, W...Electromagnetic wave.

Claims

1. It is equipped with an electron-emitting member having a metasurface that emits electrons in response to the incidence of electromagnetic waves, The metasurface includes a first antenna portion extending in a first direction and emitting electrons in response to the incidence of electromagnetic waves, a first bias portion facing the first antenna portion and configured to generate an electric field having a component in the first direction between itself and the first antenna portion, a second antenna portion extending in a second direction intersecting the first direction and emitting electrons in response to the incidence of electromagnetic waves, and a second bias portion facing the second antenna portion and configured to generate an electric field having a component in the second direction between itself and the second antenna portion. The first antenna section includes a first tip and a second tip that are positioned at different locations in the first direction. The first bias portion includes a first portion that faces the first tip and generates an electric field having a component in the first direction between itself and the first tip, and a second portion that faces the second tip and generates an electric field having a component in the first direction between itself and the second tip. The second antenna section includes a third tip and a fourth tip that are positioned at different locations in the second direction. The second bias portion includes a third portion that faces the third tip and generates an electric field having a component in the second direction between itself and the third tip, and a fourth portion that faces the fourth tip and generates an electric field having a component in the second direction between itself and the fourth tip. In the first direction, the second portion, the second tip, the first tip, and the first portion are arranged in this order. A photoelectric converter in which, in the second direction, the fourth portion, the fourth tip, the third tip, and the third portion are arranged in this order.

2. The system further includes a potential control unit that controls the potential applied to the metasurface. The potential control unit is By controlling the potential applied to the metasurface, a first state is achieved in which the component of the electric field from the first bias section toward the first antenna section in the first direction is positive, and a second state is achieved in which the component of the electric field from the first bias section toward the first antenna section in the first direction is negative. The photoelectric conversion device according to claim 1, which switches between a third state in which the component of the electric field from the second bias section toward the second antenna section in the second direction is positive, and a fourth state in which the component of the electric field from the second bias section toward the second antenna section in the second direction is negative.

3. The system further includes a potential control unit that controls the potential applied to the metasurface. The potential control unit controls the potential applied to the metasurface, A first state in which the component of the electric field from the first tip toward the first part in the first direction is positive, the component of the electric field from the second part toward the second tip in the first direction is positive, the component of the electric field from the third tip toward the third part in the second direction is positive, and the component of the electric field from the fourth tip toward the fourth part in the second direction is negative, Switching to a second state in which the component of the electric field from the first part toward the first tip in the first direction is negative, the component of the electric field from the second tip toward the second part in the first direction is negative, the component of the electric field from the third tip toward the third part in the second direction is positive, and the component of the electric field from the fourth tip toward the fourth part in the second direction is negative, A third state in which the component of the electric field from the first tip toward the first part in the first direction is positive, the component of the electric field from the second tip toward the second part in the first direction is negative, the component of the electric field from the third tip toward the third part in the second direction is positive, and the component of the electric field from the fourth part toward the fourth tip in the second direction is positive, The photoelectric converter according to claim 1, which switches between a fourth state in which the component of the electric field from the first tip toward the first part in the first direction is positive, the component of the electric field from the second tip toward the second part in the first direction is negative, the component of the electric field from the third part toward the third tip in the second direction is negative, and the component of the electric field from the fourth tip toward the fourth part in the second direction is negative.

4. The system further includes a potential control unit that controls the potential applied to the metasurface. The potential control unit controls the potential applied to the metasurface, In the first state, the potential applied to the first part is lower than the potential applied to the first antenna section, the potential applied to the second part is higher than the potential applied to the first antenna section, the potential applied to the third part is lower than the potential applied to the second antenna section, and the potential applied to the fourth part is lower than the potential applied to the second antenna section. Switching between a second state in which the potential applied to the first part is higher than the potential applied to the first antenna part, the potential applied to the second part is lower than the potential applied to the first antenna part, the potential applied to the third part is lower than the potential applied to the second antenna part, and the potential applied to the fourth part is lower than the potential applied to the second antenna part, In the third state, the potential applied to the first part is lower than the potential applied to the first antenna part, the potential applied to the second part is lower than the potential applied to the first antenna part, the potential applied to the third part is lower than the potential applied to the second antenna part, and the potential applied to the fourth part is higher than the potential applied to the second antenna part. The photoelectric converter according to claim 1, which switches between a fourth state in which the potential applied to the first part is lower than the potential applied to the first antenna part, the potential applied to the second part is lower than the potential applied to the first antenna part, the potential applied to the third part is higher than the potential applied to the second antenna part, and the potential applied to the fourth part is lower than the potential applied to the second antenna part.

5. The first direction and the second direction are orthogonal to each other. The photoelectric conversion device according to claim 1, wherein the metasurface further includes a third antenna portion that extends in a third direction intersecting the first direction and the second direction and emits electrons in response to the incidence of electromagnetic waves, and a third bias portion that faces the third antenna portion and is configured to generate an electric field having a component in the third direction between itself and the third antenna portion.

6. The system further includes a potential control unit that controls the potential applied to the metasurface. The potential control unit is By controlling the potential applied to the metasurface, a first state is achieved in which the component of the electric field from the first bias section toward the first antenna section in the first direction is positive, and a second state is achieved in which the component of the electric field from the first bias section toward the first antenna section in the first direction is negative. A third state in which the component of the electric field from the second bias section toward the second antenna section in the second direction is positive, and a fourth state in which the component of the electric field from the second bias section toward the second antenna section in the second direction is negative, are switched between. The photoelectric conversion device according to claim 5, which switches between a fifth state in which the component of the electric field from the third bias section toward the third antenna section in the third direction is negative, and a sixth state in which the component of the electric field from the third bias section toward the third antenna section in the third direction is positive.

7. The housing further comprises a window that is airtight and allows electromagnetic waves to pass through, The photoelectric conversion device according to any one of claims 1 to 6, wherein the electron-emitting member is disposed within the housing.

8. A photoelectric conversion device according to any one of claims 2, 3, 4, and 6, A detection unit for detecting electrons emitted from the electron emission member, An electromagnetic wave detection device comprising: a calculation unit that calculates the polarization information of the electromagnetic wave based on the detection result of the detection unit in the first state, the detection result of the detection unit in the second state, the detection result of the detection unit in the third state, and the detection result of the detection unit in the fourth state.

9. A metasurface comprising a first antenna portion extending in a first direction, a first bias portion facing the first antenna portion, a second antenna portion extending in a second direction intersecting the first direction, and a second bias portion facing the second antenna portion, wherein electrons are emitted from the first antenna portion in a state in which an electric field having a component in the first direction is generated between the first bias portion and the first antenna portion in response to the incidence of an electromagnetic wave to be measured onto the metasurface, The system includes the step of using the metasurface to generate an electric field having a component in a second direction between the second bias unit and the second antenna unit in response to the incidence of electromagnetic waves to be measured onto the metasurface, and then emitting electrons from the second antenna unit. The first antenna section includes a first tip and a second tip that are positioned at different locations in the first direction. The first bias portion includes a first portion that faces the first tip and generates an electric field having a component in the first direction between itself and the first tip, and a second portion that faces the second tip and generates an electric field having a component in the first direction between itself and the second tip. The second antenna section includes a third tip and a fourth tip that are positioned at different locations in the second direction. The second bias portion includes a third portion that faces the third tip and generates an electric field having a component in the second direction between itself and the third tip, and a fourth portion that faces the fourth tip and generates an electric field having a component in the second direction between itself and the fourth tip. In the first direction, the second portion, the second tip, the first tip, and the first portion are arranged in this order. A photoelectric conversion method in which, in the second direction, the fourth portion, the fourth tip, the third tip, and the third portion are arranged in this order.

10. The step of emitting electrons from the first antenna section is: In a first state in which a potential is applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is positive, a first electron emission step is performed in which electrons are emitted from the first antenna section in response to the incidence of electromagnetic waves to be measured toward the metasurface, The method includes a second electron emission step in which, in a second state in which a potential is applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is negative, electrons are emitted from the first antenna section in response to the incidence of electromagnetic waves to be measured onto the metasurface, The step of emitting electrons from the second antenna section is as follows: In a third state in which a potential is applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is positive, a third electron emission step is performed in which electrons are emitted from the second antenna section in response to the incidence of electromagnetic waves to be measured onto the metasurface, The photoelectric conversion method according to claim 9, comprising: a fourth electron emission step in which, in a fourth state in which a potential is applied to the metasurface such that the component of the electric field from the second bias portion toward the second antenna portion in the second direction is negative, electrons are emitted from the second antenna portion in response to the incidence of an electromagnetic wave to be measured toward the metasurface.

11. The first direction and the second direction are orthogonal to each other. The metasurface further includes a third antenna portion extending in a third direction intersecting the first and second directions, and a third bias portion facing the third antenna portion. The photoelectric conversion method according to claim 9, further comprising the step of emitting electrons from the third antenna in response to the incidence of electromagnetic waves to be measured onto the metasurface.

12. The step of emitting electrons from the first antenna section is: In a first state in which a potential is applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is positive, a first electron emission step is performed in which electrons are emitted from the first antenna section in response to the incidence of electromagnetic waves to be measured toward the metasurface, The method includes a second electron emission step in which, in a second state in which a potential is applied to the metasurface such that the component of the electric field from the first bias section toward the first antenna section in the first direction is negative, electrons are emitted from the first antenna section in response to the incidence of electromagnetic waves to be measured onto the metasurface, The step of emitting electrons from the second antenna section is as follows: In a third state in which a potential is applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is positive, a third electron emission step is performed in which electrons are emitted from the second antenna section in response to the incidence of electromagnetic waves to be measured onto the metasurface, The method includes a fourth electron emission step in which, in a fourth state in which a potential is applied to the metasurface such that the component of the electric field from the second bias section toward the second antenna section in the second direction is negative, electrons are emitted from the second antenna section in response to the incidence of electromagnetic waves to be measured onto the metasurface, The step of emitting electrons from the third antenna section is as follows: In a fifth state in which a potential is applied to the metasurface such that the component of the electric field from the third bias section toward the third antenna section in the third direction is negative, a fifth electron emission step is performed in which electrons are emitted from the third antenna section in response to the incidence of electromagnetic waves to be measured toward the metasurface, The photoelectric conversion method according to claim 11, comprising: a sixth electron emission step in which, in a sixth state in which a potential is applied to the metasurface such that the component of the electric field from the third bias portion toward the third antenna portion in the third direction is positive, electrons are emitted from the third antenna portion in response to the incidence of an electromagnetic wave to be measured toward the metasurface.

13. An electromagnetic wave detection method comprising the photoelectric conversion method described in claim 10 or 12, A first detection step in which electrons emitted from the electron emission member in the first electron emission step are detected, A second detection step for detecting electrons emitted from the electron-emitting member in the second electron emission step, A third detection step in which electrons emitted from the electron-emitting member are detected in the third electron emission step, A fourth detection step for detecting electrons emitted from the electron-emitting member in the fourth electron emission step, An electromagnetic wave detection method further comprising: a calculation step for calculating the polarization information of the electromagnetic wave based on the detection results of the first detection step, the second detection step, the third detection step, and the fourth detection step.

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