Photoelectric conversion device and photoelectric conversion method

Abstract

The photoelectric conversion device includes an electron emitting member having a metasurface that emits electrons in response to incidence of electromagnetic waves. The metasurface includes a plurality of photoelectric conversion units having sensitivity to electromagnetic waves in different wavelength ranges. The plurality of photoelectric conversion units include patterns having different configurations.

Description

Technical Field

[0001] One aspect of the present disclosure relates to a photoelectric conversion device and a photoelectric conversion method.

Background Art

[0002] For electron emission, for example, there are 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. U.S. Patent Application Publication No. 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 a system having such a configuration, for example, electromagnetic waves in a wavelength range from so-called millimeter waves to infrared light can be detected.

[0005] The detection of electromagnetic waves in the millimeter-wave to infrared wavelength range is expected to have various applications. For example, if electromagnetic waves are transmitted through a gas and the wavelength components absorbed by this gas are identified, the gas components can be identified based on these identified wavelength components. Wavelength components corresponding to various gas components are included in the millimeter-wave to infrared wavelength range. For this reason, this wavelength range is also called the molecular fingerprint region. If the entire above wavelength range is detectable, multiple types of gases can be easily detected.

[0006] Thus, to accommodate various applications, it is conceivable to expand the range of wavelengths of electromagnetic waves that can be detected by a single electromagnetic wave detection device. In the example above, it is conceivable to expand the range of wavelengths of electromagnetic waves that can be detected by the electromagnetic wave detection device to cover the wavelength range corresponding to each of the multiple gas components. In order to broaden the range of wavelengths of electromagnetic waves that can be detected by the electromagnetic wave detection device, it is conceivable to broaden the range of wavelengths of electromagnetic waves that can be converted into electrons by the photoelectric converter. [Means for solving the problem]

[0007] One aspect of this disclosure aims to provide a photoelectric converter that can expand the range of wavelengths of electromagnetic waves that can be converted into electrons. Another aspect of this disclosure aims to provide a photoelectric converter that can expand the range of wavelengths of electromagnetic waves that can be converted into electrons.

[0008] A photoelectric conversion device in one aspect of this disclosure comprises an electron-emitting member having a metasurface that emits electrons in response to the incidence of electromagnetic waves. The metasurface includes a plurality of photoelectric conversion units that are sensitive to electromagnetic waves in different wavelength ranges. The plurality of photoelectric conversion units include patterns having different configurations.

[0009] In this photoelectric conversion device, the electron-emitting member has a metasurface that emits electrons in response to the incidence of electromagnetic waves. The metasurface includes multiple photoelectric conversion units that are sensitive to electromagnetic waves in different wavelength ranges. The multiple photoelectric conversion units include patterns with different configurations. As a result, the photoelectric conversion device is sensitive to electromagnetic waves in different wavelength ranges in its multiple photoelectric conversion units. Therefore, the range of wavelengths of electromagnetic waves that can be converted into electrons is expanded in the photoelectric conversion device.

[0010] In one aspect described above, the pattern of each photoelectric conversion section may include first and second portions that are spaced apart from each other. The second portion may include a tip facing the first portion. The second portion may emit electrons in response to the incidence of electromagnetic waves when it is given a lower potential than the first portion. In this case, the range of wavelengths of electromagnetic waves from which electrons are emitted in the photoelectric conversion device can be controlled by controlling the potential applied to the first and second portions.

[0011] In one aspect described above, the second portion of each photoelectric conversion unit may include a linear portion extending toward the first portion. The linear portions of at least two of the multiple photoelectric conversion units may have different lengths. Depending on the length of the linear portion, the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion unit changes. Therefore, with a simple configuration, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric conversion device can be expanded.

[0012] In one aspect of the above, in two of the multiple photoelectric conversion units, the first or second part of one photoelectric conversion unit and the first or second part of the other photoelectric conversion unit may be electrically connected. In this case, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric conversion device can be expanded with a simpler configuration.

[0013] In one aspect of the above, the photoelectric conversion device may further include a potential control unit that controls the potential applied to the first and second parts of each photoelectric conversion unit. In this case, the potential control unit can select which photoelectric conversion unit to operate.

[0014] In one aspect of the above, the multiple photoelectric conversion units may include a first photoelectric conversion unit and a second photoelectric conversion unit. The potential control unit may control the potential applied to the first and second parts of the first photoelectric conversion unit and the first and second parts of the second photoelectric conversion unit. The potential difference between the potential applied to the first part of the first photoelectric conversion unit and the potential applied to the second part of the first photoelectric conversion unit, and the potential applied to the first part of the second photoelectric conversion unit and the potential applied to the second part of the second photoelectric conversion unit may be different from each other. In this case, the first photoelectric conversion unit and the second photoelectric conversion unit can operate independently. Therefore, this photoelectric conversion device can change the range of wavelengths of electromagnetic waves that can be converted into electrons.

[0015] In one aspect of the above, when the potential control unit applies a potential lower than the potential applied to the first part of the second photoelectric conversion unit to the second part of the second photoelectric conversion unit, it may also apply a potential higher than the potential applied to the first part of the first photoelectric conversion unit to the second part of the first photoelectric conversion unit. In this case, the second photoelectric conversion unit is kept in a state where it emits electrons in response to the incidence of electromagnetic waves, while the emission of electrons from the first photoelectric conversion unit in response to the incidence of electromagnetic waves can be reliably stopped.

[0016] In one aspect of the above, the potential control unit may apply a lower potential to the second part of at least two of the multiple photoelectric conversion units than the potential applied to the first part. In this case, the at least two photoelectric conversion units operate simultaneously. Therefore, the conversion of electromagnetic waves in wavelength ranges corresponding to each of the multiple photoelectric conversion units into electrons can be performed simultaneously.

[0017] In the above aspect, the patterns of each photoelectric conversion unit may be at the same potential. In this case, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric conversion device can be expanded with a simpler configuration.

[0018] In one aspect of the above, the patterns of each photoelectric conversion unit may be electrically connected to one another. In this case, a simpler configuration can be used to expand the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric conversion device.

[0019] In one aspect described above, the pattern of each photoelectric conversion unit may include a linear portion. The linear portions of at least two of the multiple photoelectric conversion units may have different lengths. Depending on the length of the linear portion, the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion unit changes. Therefore, with a simpler configuration, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric conversion device can be expanded.

[0020] In one aspect of the above, the housing may further include a housing that is hermetically sealed and has a window 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.

[0021] A photoelectric conversion method in another aspect of the present disclosure comprises: injecting an electromagnetic wave to be measured into a metasurface including a plurality of photoelectric conversion units; and causing electrons to be emitted from at least one of the plurality of photoelectric conversion units corresponding to the wavelength range of the electromagnetic wave to be measured. The plurality of photoelectric conversion units include patterns having different configurations from each other.

[0022] In this photoelectric conversion method, the electromagnetic wave to be measured is incident on a metasurface containing multiple photoelectric conversion units. The multiple photoelectric conversion units include patterns having different configurations from each other. Electrons are emitted from at least one photoelectric conversion unit corresponding to the wavelength range of the electromagnetic wave to be measured. In this case, the range of wavelengths of electromagnetic waves that can be converted into electrons can be expanded.

[0023] In another aspect, the photoelectric conversion method may further include controlling the potential applied to a plurality of photoelectric conversion units. The pattern of each photoelectric conversion unit may include a first portion and a second portion that is spaced apart from and faces the tip of the first portion. Each photoelectric conversion unit may emit electrons in response to the incidence of electromagnetic waves in a state where a potential lower than the potential applied to the first portion is applied to the second portion. The potentials applied to the first and second portions of each photoelectric conversion unit may be controlled. In this case, the photoelectric conversion unit to be operated is selected by controlling the potentials applied to the first and second portions of each photoelectric conversion unit.

[0024] In another aspect, the potentials applied to a first photoelectric conversion unit and a second photoelectric conversion unit included in a plurality of photoelectric conversion units may be controlled. The potential difference between the potential applied to the first portion of the first photoelectric conversion unit and the potential applied to the second portion of the first photoelectric conversion unit, and the potential difference between the potential applied to the first portion of the second photoelectric conversion unit and the potential applied to the second portion of the second photoelectric conversion unit may be different. In this case, since the potentials applied to the first photoelectric conversion unit and the second photoelectric conversion unit are controlled respectively, the first photoelectric conversion unit and the second photoelectric conversion unit can be operated separately.

[0025] In another aspect, when a potential lower than the potential applied to the first portion of the second photoelectric conversion unit is applied to the second portion of the second photoelectric conversion unit, a potential higher than the potential applied to the first portion of the first photoelectric conversion unit may be applied to the second portion of the first photoelectric conversion unit. When a potential lower than the potential applied to the first portion of the first photoelectric conversion unit is applied to the second portion of the first photoelectric conversion unit, a potential higher than the potential applied to the first portion of the second photoelectric conversion unit may be applied to the second portion of the second photoelectric conversion unit. In this case, while one of the first and second photoelectric conversion units is in a state of emitting electrons in response to the incidence of electromagnetic waves, the emission of electrons in response to the incidence of electromagnetic waves from the other can be reliably stopped.

[0026] In another aspect described above, in at least two of the multiple photoelectric conversion units, a potential lower than the potential applied to the first unit may be applied to the second unit. In this case, the multiple photoelectric conversion units operate simultaneously. Therefore, the conversion of electromagnetic waves of wavelengths corresponding to each of the multiple photoelectric conversion units into electrons can be performed simultaneously.

[0027] According to one aspect of this disclosure, it is possible to provide a photoelectric converter in which the range of wavelengths of electromagnetic waves that can be converted into electrons is expanded. According to another aspect of this disclosure, it is possible to provide a photoelectric converter method in which the range of wavelengths of electromagnetic waves that can be converted into electrons is expanded. [Brief explanation of the drawing]

[0028] [Figure 1] Figure 1 is a schematic diagram of an electromagnetic wave detection device in the first embodiment. [Figure 2] Figure 2 is a schematic diagram of the photoelectric conversion device in the first and second embodiments. [Figure 3] Figure 3 is a plan view of the electron emission member in the first embodiment. [Figure 4] Figure 4 is a schematic diagram of the photoelectric converter in the first embodiment. [Figure 5] Figure 5 is a flowchart of the electromagnetic wave detection method in the first embodiment. [Figure 6] Figure 6 is a flowchart of the electromagnetic wave detection method in a modified example of the first embodiment. [Figure 7] Figure 7 is a plan view of the electron emission member in the second embodiment. [Figure 8] Figure 8 is a plan view of the electron emission member in a modified example of the second embodiment. [Figure 9] Figure 9 is a plan view of the electron emission member in a modified example of the second embodiment. [Figure 10] Figure 10 is a schematic diagram of the electromagnetic wave detection device in the third embodiment. [Figure 11](a) is a plan view of the electron emission member in the third embodiment. (b) is a plan view of the electron emission member in a modified example of the third embodiment. [Modes for carrying out the invention]

[0029] The first and second 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 explanations will be omitted. [First Embodiment]

[0030] First, the configuration of the electromagnetic wave detection device in the first embodiment will be described with reference to Figure 1. Figure 1 is a schematic diagram of the electromagnetic wave detection device in the first embodiment.

[0031] 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.

[0032] 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 sensor outside this electron tube that detects the electrons emitted from the electron tube.

[0033] The electromagnetic wave detection device 1 comprises a housing 10, an electron-emitting member 20, a holding member 30, an electron multiplier unit 40, an electron collection unit 50, and a power supply unit 60. The electron-emitting member 20, the holding member 30, the electron multiplier 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-emitting member 20, and the power supply unit 60, and constitutes a part of the electromagnetic wave detection device 1.

[0034] 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.

[0035] 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.

[0036] 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. For this reason, the window portion 11a is made of an optimal material according to the frequency range of electromagnetic waves incident on the housing 10. The material of the window portion 11a includes, for example, at least one selected from 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.

[0037] The housing 10 further includes 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.

[0038] 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.

[0039] 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 described above. The material of the support 21 may include, for example, silicon. In a single photoelectric conversion device 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.

[0040] 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.

[0041] 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.

[0042] 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.

[0043] 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.

[0044] 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 sensor that detects electrons. 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.

[0045] 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 60. The power supply unit 60 is electrically connected to the metasurface 22. The power supply unit 60 includes a potential supply unit 61 and a potential control unit 62. The potential supply unit 61 supplies a potential to the metasurface 22. The potential control unit 62 controls the potential supply unit 61. The potential supplied to the metasurface 22 is controlled by the potential control unit 62. The metasurface 22 operates according to the potential controlled by the potential control unit 62. In other words, the metasurface 22 emits electrons in response to the potential control by the potential control unit 62.

[0046] The potential control unit 62 is, for example, one or more computers composed of hardware and software such as programs. The potential control unit 62 includes, 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. [Configuration of the photoelectric converter]

[0047] Next, the photoelectric converter 2 will be described in more detail with reference to Figures 2 to 4. Figure 2 is a schematic diagram of the photoelectric converter. The metasurface 22 includes a plurality of photoelectric conversion units 23, 24, and 25. Each of the plurality of photoelectric conversion units 23, 24, and 25 emits electrons in response to the incidence of a corresponding wavelength. Each of the plurality of photoelectric conversion units 23, 24, and 25 emits electrons in response to the incidence of electromagnetic waves in different wavelength ranges. In other words, each of the plurality of photoelectric conversion units 23, 24, and 25 is sensitive to electromagnetic waves in different wavelength ranges. "Different wavelength ranges" includes cases where the multiple wavelength ranges overlap each other, as well as cases where the multiple wavelength ranges are separated from each other.

[0048] The metasurface 22 includes, for example, three photoelectric conversion units 23, 24, and 25. The metasurface 22 may include two or more photoelectric conversion units corresponding to electromagnetic waves in different wavelength ranges. The metasurface 22 may include multiple photoelectric conversion units corresponding to electromagnetic waves in the same wavelength range. In other words, the metasurface 22 may be sensitive to electromagnetic waves in the same wavelength range. For example, photoelectric conversion unit 23 and photoelectric conversion unit 24 may correspond to electromagnetic waves in the same wavelength range, while photoelectric conversion unit 25 may correspond to electromagnetic waves in a different wavelength range than photoelectric conversion units 23 and 24.

[0049] For example, the photoelectric conversion unit 23 is sensitive to a frequency range with a center frequency of 0.5 THz, the photoelectric conversion unit 24 is sensitive to a frequency range with a center frequency of 1.0 THz, and the photoelectric conversion unit 25 is sensitive to a frequency range with a center frequency of 1.5 THz. The frequency ranges to which each photoelectric conversion unit 23, 24, and 25 is sensitive are not limited to these. For example, the photoelectric conversion unit 23 may be sensitive to a frequency range with a center frequency of 0.5 THz, the photoelectric conversion unit 24 may be sensitive to a frequency range with a center frequency of 10 THz, and the photoelectric conversion unit 25 may be sensitive to a frequency range with a center frequency of 100 THz.

[0050] In the example shown in Figure 2, electromagnetic waves W incident on the housing 10 are incident on the photoelectric conversion units 23, 24, and 25. In this case, the photoelectric conversion unit corresponding to the wavelength of the electromagnetic wave W among the photoelectric conversion units 23, 24, and 25 emits electrons E in response to the incidence of the electromagnetic wave W. Electrons E emitted from at least one of the photoelectric conversion units 23, 24, and 25 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.

[0051] Figure 3 is a plan view of the electron-emitting member. As shown in Figure 3, the multiple photoelectric conversion units 23, 24, and 25 in the metasurface 22 include patterns having different configurations. "Configuration" includes various attributes such as shape and material. Each pattern is arranged on the main surface 21b of the support 21. In this embodiment, each pattern has a different shape. "Having different shapes" also includes having different sizes.

[0052] In this embodiment, each of the photoelectric conversion units 23, 24, and 25 includes patterns 33, 34, and 35 having different shapes from each other. Photoelectric conversion unit 23 includes pattern 33, photoelectric conversion unit 24 includes pattern 34, and photoelectric conversion unit 25 includes pattern 35. Each pattern 33, 34, and 35 is a conductive line and conducts electrons. Each pattern 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.

[0053] Each pattern 33, 34, and 35 includes a first part 37 and a second part 38. The first part 37 and the second part 38 are spaced apart from each other. The second part 38 extends toward the first part 37. The second part 38 includes a tip 39 facing the first part 37. In each pattern 33, 34, and 35, the first part 37 and the second part 38 are connected via an oxide layer. In each pattern 33, 34, and 35, the first part 37 and the second part 38 are separated by an oxide layer and are insulated from each other, at least when the photoelectric converter 2 is not operating. The second part 38 emits electrons in response to the incidence of electromagnetic waves when it is given a lower potential than the first part 37.

[0054] In the example shown in Figure 3, the first portion 37 of each pattern 33, 34, 35 includes a pair of linear sections 41 extending in the Y-axis direction. Each linear section 41 is, for example, linear. The pair of linear sections 41 are parallel to each other. The second portion 38 of each pattern 33, 34, 35 includes a plurality of linear sections 42 extending in the Z-axis direction and a linear section 43 extending in the Y-axis direction and connecting the plurality of linear sections 42.

[0055] Multiple linear sections 42 are positioned between pairs of linear sections 41 in each pattern 33, 34, and 35. The multiple linear sections 42 extend from the linear section 43 toward the corresponding first section 37. Each linear section 42 is, for example, linear. The multiple linear sections 42 are, for example, parallel to each other. The linear section 43 is, for example, linear. The pair of linear sections 41 are, for example, parallel to the linear section 43. Each linear section 42 is connected to the linear section 43 at its center. In other words, each linear section 42 extends from the linear section 43 in the +Z-axis direction and the -Z-axis direction.

[0056] In the example shown in Figure 3, each linear section 42 includes a pair of tips 39. Each tip 39 is spaced apart from other linear sections 42 and 43 of the same pattern, as well as from other patterns. In each pattern 33, 34, and 35, each tip 39 faces a different linear section 41 in the Z-axis direction. The shortest distance between each tip 39 and the first section 37 is smaller than the shortest distance between the first section 37 and any other location in the second section 38 that does not contain any of the tips 39. In other words, each tip 39 is the part of the linear section 42 containing it that is closest to the corresponding linear section 41 of the first section 37. Each tip 39 is positioned closer to the linear section 41 than other parts of the pattern containing it.

[0057] In each of the photoelectric conversion units 23, 24, and 25, the linear portion 41 constitutes the bias portion, and the linear portion 42 constitutes the antenna portion. The antenna portion emits electrons in response to the incidence of electromagnetic waves. The bias portion generates an electric field between itself and the corresponding antenna portion when a bias potential is applied. When a higher potential is applied to the bias portion than to the antenna portion, the potential barrier at the tip of the antenna portion on the bias portion side becomes thinner. When a lower potential is applied to the bias portion than to the antenna portion, the potential barrier at the tip of the antenna portion on the bias portion side becomes thicker. The state in which a higher potential is applied to the bias portion than to the antenna portion is called "forward bias". The state in which a lower potential is applied to the bias portion than to the antenna portion is called "reverse bias".

[0058] When electromagnetic waves are incident on the antenna, an electric field is induced around the antenna. The electric field induced around the antenna thins the potential barrier at the antenna-vacuum interface. If the potential barrier is further thinned by the incidence of electromagnetic waves on the antenna in a forward-biased state, electrons present in the antenna can pass through the potential barrier by tunneling. Electrons that have passed through the potential barrier are accelerated by the electric field around the antenna. In this way, field electron emission can occur when electromagnetic waves are incident on the antenna in a forward-biased state. In each photoelectric conversion unit 23, 24, 25, the linear portion 42 of the second part 38 can emit electrons in response to the incidence of electromagnetic waves when it is given a lower potential than the linear portion 41 of the first part 37.

[0059] The smaller the size of the antenna section, the more easily field electron emission occurs for electromagnetic waves with shorter wavelengths, i.e., electromagnetic waves with higher frequencies. The photoelectric conversion sections 23, 24, and 25 of the metasurface 22 are configured to correspond to wavelengths ranging from so-called millimeter waves to infrared light, for example, depending on the change in the structure of the linear section 42 of the second section 38.

[0060] The linear portions 42 of at least two of the multiple photoelectric conversion units 23, 24, and 25 have different lengths. For example, the linear portions 42 of the multiple patterns 33, 34, and 35 have different lengths T1, T2, and T3. In other words, the linear portions 42 of the photoelectric conversion unit 23, the linear portions 42 of the photoelectric conversion unit 24, and the linear portions 42 of the photoelectric conversion unit 25 have different lengths T1, T2, and T3. The lengths T1, T2, and T3 of the linear portions 42 in each pattern 33, 34, and 35 are the lengths in the Z-axis direction from one end 39 to the other end 39 of the linear portion 42.

[0061] In pattern 33, the lengths T1 of the multiple linear sections 42 are the same. In pattern 34, the lengths T2 of the multiple linear sections 42 are the same. In pattern 35, the lengths T3 of the multiple linear sections 42 are the same. "Same" includes differences in length within the manufacturing tolerance range. The lengths T1, T2, and T3 of the linear sections 42 in each of patterns 33, 34, and 35 correspond to the wavelength range of electromagnetic waves from which electrons are emitted in each of the photoelectric conversion units 23, 24, and 25. The lengths T1, T2, and T3 of the linear sections 42 in each of patterns 33, 34, and 35 are designed according to the desired wavelength range from which electrons are emitted from each of the photoelectric conversion units 23, 24, and 25. For example, each of the lengths T1, T2, and T3 is half the length of the central wavelength in the desired wavelength range. In this embodiment, when electromagnetic waves transmitted through the support 21, etc., are incident on the linear section 42, the refractive index of the transmitted support 21, etc., is also taken into consideration. For example, if the wavelength of the electromagnetic wave incident on the electron tube is 600 μm, and the refractive index of the support 21 is 3.4 relative to this electromagnetic wave, then the wavelength of the electromagnetic wave incident on the linear portion 42 is 600 μm / 3.4 = 176 μm. Therefore, in this case, lengths T1, T2, and T3 are suitable if they are 176 μm / 2 = 88 μm.

[0062] The electron-emitting member 20 further comprises a plurality of electrodes 51, 52, 53, 54 spaced apart from each other, as shown in Figure 3. The plurality of electrodes 51, 52, 53, 54 are provided on the main surface 21b of the support 21. The plurality of electrodes 51, 52, 53, 54 are electrically connected to at least one of the plurality of photoelectric conversion units 23, 24, 25. In this embodiment, each electrode 51, 52, 53, 54 has a rectangular shape. In a modified example of this embodiment, each electrode 51, 52, 53, 54 may have a linear shape, similar to the first part 37 or the second part 38. Each electrode 51, 52, 53, 54 may be formed integrally with the first part 37 or the second part 38.

[0063] For example, electrode 51 is electrically connected to the second part 38 of each of the photoelectric conversion units 23, 24, and 25. Electrode 52 is electrically connected to a pair of first parts 37 of the photoelectric conversion unit 23. Electrode 53 is electrically connected to a pair of first parts 37 of the photoelectric conversion unit 24. Electrode 54 is electrically connected to a pair of first parts 37 of the photoelectric conversion unit 25.

[0064] In two of the multiple photoelectric conversion units 23, 24, and 25, the first part 37 or second part 38 of one photoelectric conversion unit may be electrically connected to the first part 37 or second part 38 of the other photoelectric conversion unit. For example, in the example shown in Figure 3, the second part 38 of photoelectric conversion unit 23, the second part 38 of photoelectric conversion unit 24, and the second part 38 of photoelectric conversion unit 25 are electrically connected via the electrode 51.

[0065] Each of the photoelectric conversion units 23, 24, and 25 operates by receiving a potential from the power supply unit 60 via multiple electrodes 51, 52, 53, and 54. The potential application unit 61 of the power supply unit 60 applies a potential to each of the photoelectric conversion units 23, 24, and 25 via the multiple electrodes 51, 52, 53, and 54. The potential control unit 62 of the power supply unit 60 controls the potential applied to each of the photoelectric conversion units 23, 24, and 25.

[0066] Figure 4 is a schematic diagram illustrating the application of potential in a photoelectric converter. As shown in Figure 4, the potential application unit 61 includes, for example, a first potential application unit 61a, a second potential application unit 61b, and a third potential application unit 61c. The first potential application unit 61a applies a potential difference between electrode 51 and electrode 52. The second potential application unit 61b applies a potential difference between electrode 51 and electrode 53. The third potential application unit 61c applies a potential difference between electrode 51 and electrode 54. The potential control unit 62 controls the first potential application unit 61a, the second potential application unit 61b, and the third potential application unit 61c, respectively. [Photoelectric conversion method]

[0067] Next, with reference to Figure 5, the electromagnetic wave detection method in this embodiment will be described. This electromagnetic wave detection method includes a photoelectric conversion method that emits electrons in response to incident electromagnetic waves. Figure 5 is a flowchart of the electromagnetic wave detection method in this embodiment. In the electromagnetic wave detection method shown in Figure 5, the range of wavelengths to be detected is determined. The range of wavelengths to be detected is divided into multiple wavelength ranges, and detection is performed for each wavelength range. As a result, the same results as detection by spectroscopy are obtained for the determined wavelength range. In the example shown in Figure 5, by operating multiple photoelectric conversion units in sequence, the wavelength ranges corresponding to each photoelectric conversion unit are detected in sequence.

[0068] First, the electron-emitting member 20 is prepared (process S1). For example, an electromagnetic wave detection device 1 equipped with the electron-emitting member 20 is positioned.

[0069] Next, the wavelength range is determined (process S2). For example, the potential control unit 62 acquires various information from an external source and determines the wavelength range of the electromagnetic waves to be detected based on this information. The various information may be input by the user or acquired automatically by communication. The potential control unit 62 may also determine the wavelength range of the electromagnetic waves to be detected based on various information stored in advance.

[0070] Next, the photoelectric conversion unit to be operated is determined (process S3). The potential control unit 62 determines the photoelectric conversion unit to be operated, for example, based on the wavelength range determined in process S2. The potential control unit 62 determines, for example, at least one of the photoelectric conversion units that are sensitive to the wavelength range determined in process S2 as the photoelectric conversion unit to be operated. For example, the potential control unit 62 determines that of the multiple photoelectric conversion units 23, 24, 25, photoelectric conversion unit 23 will be operated and used as the photoelectric conversion unit, and that photoelectric conversion units 24 and 25 will not be operated.

[0071] Next, a potential is applied to the photoelectric conversion unit (process S4). The potential control unit 62 determines the potential to be applied to each electrode 51, 52, 53, and 54 based on the photoelectric conversion unit to be operated, for example. For example, the potential control unit 62 obtains information associated with the photoelectric conversion unit to be operated by referring to a pre-stored table. Based on the obtained information, the potential control unit 62 determines the potential to be applied to each of the electrodes 51, 52, 53, and 54.

[0072] For example, the potential control unit 62 controls the bias voltage applied to the photoelectric conversion units that are operated and those that are not, among the multiple photoelectric conversion units. For example, the potential difference between the potential applied to the first part 37 and the potential applied to the second part 38 in the operated photoelectric conversion unit is different from the potential applied to the first part 37 and the potential applied to the second part 38 in the photoelectric conversion unit that is not operated.

[0073] The potential control unit 62 determines the potential to be applied to each photoelectric conversion unit, for example, such that a forward bias voltage is applied to the photoelectric conversion unit that is being operated, and a reverse bias voltage is applied to the photoelectric conversion unit that is not being operated. The potential control unit 62 controls the potential application unit 61 and applies the determined potential to each photoelectric conversion unit. In other words, the potential control unit 62 applies a potential to the second part 38 that is higher than the potential applied to the first part 37 in the photoelectric conversion unit that is being operated. The potential control unit 62 applies a potential to the second part 38 that is lower than the potential applied to the first part 37 in the photoelectric conversion unit that is not being operated.

[0074] For example, when the potential control unit 62 applies a potential lower to the second part 38 of the photoelectric conversion unit 24 than the potential applied to the first part 37 of the photoelectric conversion unit 24, it applies a potential higher to the second part 38 of the photoelectric conversion units 23 and 25 than the potential applied to the first part 37 of the photoelectric conversion units 23 and 25. In this case, the photoelectric conversion unit 24 operates, while the photoelectric conversion units 23 and 25 do not operate. Therefore, electrons are emitted from the metasurface 22 only when electromagnetic waves in the wavelength range corresponding to the photoelectric conversion unit 24 are incident on the photoelectric conversion device 2.

[0075] Next, electromagnetic waves are incident on the metasurface 22 (process S5). For example, electromagnetic waves that have passed through the window portion 11a of the housing 10 are incident on the metasurface 22. For example, the electromagnetic waves to be measured are incident on the metasurface 22. As a result, electrons are emitted from at least one of the multiple photoelectric conversion units 23, 24, 25 that corresponds to the wavelength range of the electromagnetic waves to be measured. The window portion 11a is configured to transmit the electromagnetic waves to be measured.

[0076] Next, electromagnetic waves are detected in response to electrons emitted from the metasurface 22 (process S6). The electromagnetic wave detection device 1 detects electromagnetic waves with the potential determined in process S4 applied to each photoelectric conversion unit. The electromagnetic wave detection device 1, for example, multiplies the electrons emitted from the electron emission member 20 and detects the multiplied electrons. As a result, the electromagnetic wave detection device 1 detects electromagnetic waves incident from the window portion 11a of the housing 10.

[0077] Next, it is determined whether to terminate the electromagnetic wave detection process in the current operating state (process S7). In other words, it is determined whether to terminate the electromagnetic wave detection process in the operating state of the photoelectric conversion unit determined in process S3. If it is determined not to terminate the detection process, the process proceeds to process S5. If it is determined to terminate the detection process, the process proceeds to process S8. The decision in process S7 may be made, for example, by the potential control unit 62 or by another control unit in the electromagnetic wave detection device 1.

[0078] Next, it is determined whether detection of all wavelengths within the wavelength range determined in process S2 has been completed (process S8). For example, the potential control unit 62 determines whether all photoelectric conversion units sensitive to the wavelength range determined in process S2 have been operated. If it is determined that all photoelectric conversion units sensitive to the wavelength range determined in process S2 have been operated, it is determined that detection of the wavelength range determined in process S2 has been completed. The determination in process S8 may be performed by other control units in the electromagnetic wave detection device 1.

[0079] If it is determined in process S8 that detection of all wavelengths within the wavelength range has not been completed, the process proceeds to process S9. In this case, the photoelectric conversion unit to be operated is changed (process S9). For example, the potential control unit 62 changes the photoelectric conversion unit to be operated based on the wavelength range determined in process S3. The potential control unit 62, for example, determines that the photoelectric conversion unit to be operated is one that is not currently operating among the photoelectric conversion units that are sensitive to the wavelength range determined in process S2. If the photoelectric conversion unit to be operated is changed in process S9, the process proceeds to process S4.

[0080] For example, the potential control unit 62 switches from a state where the photoelectric conversion unit 24 is operating and the photoelectric conversion units 23 and 25 are not operating to a state where the photoelectric conversion unit 25 is operating and the photoelectric conversion units 23 and 24 are not operating. In this case, a potential lower than the potential applied to the first part 37 of the photoelectric conversion unit 25 is applied to the second part 38 of the photoelectric conversion unit 25, and a potential higher than the potential applied to the first part 37 of the photoelectric conversion units 23 and 24 is applied to the second part 38 of the photoelectric conversion units 23 and 24. Therefore, the state is switched from one in which electrons are emitted from the metasurface 22 only when electromagnetic waves in the wavelength range corresponding to the photoelectric conversion unit 24 are incident on the photoelectric conversion device 2, to a state in which electrons are emitted from the metasurface 22 only when electromagnetic waves in the wavelength range corresponding to the photoelectric conversion unit 25 are incident on the photoelectric conversion device 2.

[0081] In process S8, if it is determined that detection of all wavelengths within the wavelength range has been completed, the series of processes in the electromagnetic wave detection method is terminated. Thus, in the electromagnetic wave detection method shown in Figure 5, detection of each wavelength range within the wavelength range to be detected is performed by switching the photoelectric conversion unit to be operated and repeating processes S4 to S7. The order in which the photoelectric conversion units to be operated may be determined in process S3.

[0082] In this embodiment, for example, in process S3, if, among the multiple photoelectric conversion units 23, 24, and 25, photoelectric conversion unit 23 is determined to be the photoelectric conversion unit to be operated and photoelectric conversion units 24 and 25 are determined to be the photoelectric conversion units not to be operated, then a forward bias potential is applied to photoelectric conversion unit 23 and a reverse bias potential is applied to photoelectric conversion units 24 and 25. Subsequently, in process S9, if, among the multiple photoelectric conversion units 23, 24, and 25, photoelectric conversion unit 24 is determined to be the photoelectric conversion unit to be operated and photoelectric conversion units 23 and 25 are determined to be the photoelectric conversion units not to be operated, then a forward bias potential is applied to photoelectric conversion unit 24 and a reverse bias potential is applied to photoelectric conversion units 23 and 25.

[0083] Next, with reference to Figure 6, a photoelectric conversion method in a modified version of this embodiment will be described. The differences from the example shown in Figure 5 will be primarily explained, with some overlapping parts omitted. Figure 6 is a flowchart of the electromagnetic wave detection method in this embodiment. In the electromagnetic wave detection method shown in Figure 6, the wavelength range to be detected is determined, and the presence or absence of electromagnetic waves having wavelength components within the determined wavelength range is detected. The wavelength range to be detected may be multiple wavelength ranges that are separated from each other. In the example shown in Figure 6, electromagnetic waves are detected by simultaneously operating multiple photoelectric conversion units corresponding to the determined wavelength range. In the electromagnetic wave detection method shown in Figure 6, electromagnetic waves having wavelength components within multiple wavelength ranges are detected simultaneously.

[0084] First, the electron-emitting member 20 is prepared (process S11). For example, an electromagnetic wave detection device 1 equipped with the electron-emitting member 20 is positioned.

[0085] Next, the wavelength range is determined (process S12). For example, the potential control unit 62 acquires various information from an external source and determines the wavelength range of the electromagnetic waves to be detected based on this information. The various information may be input by the user or acquired automatically by communication. The potential control unit 62 may also determine the wavelength range of the electromagnetic waves to be detected based on various information stored in advance.

[0086] Next, the photoelectric conversion unit to be operated is determined (process S13). The potential control unit 62 determines the photoelectric conversion unit to be operated, for example, based on the wavelength range determined in process S12. The potential control unit 62 determines, for example, a plurality of photoelectric conversion units that are sensitive to the wavelength range determined in process S12 as the photoelectric conversion units to be operated. For example, the potential control unit 62 operates all of the photoelectric conversion units that are sensitive to the wavelength range determined in process S12. The potential control unit 62 determines, for example, all of the photoelectric conversion units corresponding to the wavelength range determined in process S12 as the photoelectric conversion units to be operated.

[0087] Next, potentials are applied to multiple photoelectric conversion units (process S14). The potential control unit 62 determines the potential to be applied to each electrode 51, 52, 53, and 54 based on the photoelectric conversion unit to be operated, for example. For example, the potential control unit 62 obtains information associated with the photoelectric conversion unit to be operated by referring to a pre-stored table. Based on the obtained information, the potential control unit 62 determines the potential to be applied to each of the electrodes 51, 52, 53, and 54.

[0088] The potential control unit 62 applies a lower potential to the second part 38 than the potential applied to the first part 37 in at least two of the multiple photoelectric conversion units. For example, the potential control unit 62 applies a lower potential to the second part 38 than the potential applied to the first part 37 in each of the multiple photoelectric conversion units determined in process S13. In other words, the potential control unit 62 applies a forward bias voltage to all photoelectric conversion units corresponding to the wavelength range determined in process S12, for example. The potential control unit 62 applies a reverse bias voltage to all photoelectric conversion units that do not correspond to the wavelength range determined in process S12, for example.

[0089] For example, the potential control unit 62 applies a potential to the second part 38 that is lower than the potential applied to the first part 37 in each of the photoelectric conversion units 23, 24, and 25. In this case, all of the photoelectric conversion units 23, 24, and 25 operate. Therefore, when electromagnetic waves in the wavelength range corresponding to any of the photoelectric conversion units 23, 24, and 25 are incident on the photoelectric conversion device 2, electrons are emitted from the metasurface 22.

[0090] Next, electromagnetic waves are incident on the metasurface 22 (process S15). For example, electromagnetic waves that have passed through the window portion 11a of the housing 10 are incident on the metasurface 22.

[0091] Next, electromagnetic waves are detected in response to electrons emitted from the metasurface 22 (process S16). The electromagnetic wave detection device 1 detects electromagnetic waves with the potential determined in process S14 applied to each photoelectric conversion unit. The electromagnetic wave detection device 1, for example, multiplies the electrons emitted from the electron emission member 20 and detects the multiplied electrons. In this way, the electromagnetic wave detection device 1 detects electromagnetic waves incident from the window portion 11a of the housing 10.

[0092] Next, a decision is made to terminate the detection process (process S17). If it is decided not to terminate the detection process, the process proceeds to process S15. If it is decided to terminate the detection process, the series of processes in the electromagnetic wave detection method are terminated. In this way, in the electromagnetic wave detection method shown in Figure 6, the photoelectric conversion unit corresponding to the wavelength range to be detected operates simultaneously, and the presence or absence of electromagnetic waves in the wavelength range to be detected is detected at once. [Second Embodiment]

[0093] Next, with reference to Figure 7, the configuration of the electromagnetic wave detection device in the second embodiment will be described. This embodiment is generally similar to or the same as the embodiments and modifications described above. The second embodiment differs from the first embodiment and modifications described above in the structure of the photoelectric conversion unit and the method of applying potential to the electron conversion unit. The differences from the first embodiment described above will be mainly explained below. The metasurface of the second embodiment is also of the active type, similar to the metasurface 22 of the first embodiment.

[0094] Figure 7 is a plan view of the electron emission member in the second embodiment. In this embodiment, the electron emission member 20 has a metasurface 22A. 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 60. In the example shown in Figure 7, the metasurface 22A includes two photoelectric conversion units 23A and 24A. The photoelectric conversion units 23A and 24A correspond to electromagnetic waves in different wavelength ranges. In other words, the multiple photoelectric conversion units 23A and 24A are sensitive to electromagnetic waves in different wavelength ranges.

[0095] Multiple photoelectric conversion units 23A, 24A in the metasurface 22A include patterns having different configurations. Each pattern is arranged on the main surface 21b of the support 21. Each pattern has a different shape. Each of the photoelectric conversion units 23A, 24A includes patterns 33A, 34A having different shapes. Photoelectric conversion unit 23A includes pattern 33A, and photoelectric conversion unit 24A includes pattern 34A. Each pattern 33A, 34A is a conductive line and conducts electrons. Each pattern 33A, 34A 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.

[0096] Each pattern 33A, 34A includes a plurality of first parts 37A and a plurality of second parts 38A. In this modified example, each pattern 33A, 34A includes two first parts 37A and two second parts 38A. In each pattern 33A, 34A, the first parts 37A and the second parts 38A are arranged alternately in the Z-axis direction. Each first part 37A of each pattern 33A, 34A includes a tip 39A. Each second part 38A of each pattern 33A, 34A includes a tip 40A. In adjacent first parts 37A and second parts 38A, the tips 39A and 40A face each other in the Z-axis direction. In each pattern 33A, 34A, the first parts 37A and the second parts 38A are connected via an oxide layer. In each pattern 33A, 34A, the first part 37A and the second part 38A are separated by an oxide layer and are insulated from each other at least when the photoelectric converter 2 is not in operation.

[0097] The first part 37A emits electrons in response to incident electromagnetic waves when it is subjected to a lower potential than the second part 38A. Similarly, the second part 38A emits electrons in response to incident electromagnetic waves when it is subjected to a lower potential than the first part 37A. Therefore, each photoelectric conversion unit 23A, 24A can emit electrons from either the first part 37A or the second part 38A, depending on the potential state.

[0098] In the example shown in Figure 7, each second portion 38A of each pattern 33A, 34A includes a plurality of linear sections 44A extending in the Z-axis direction and a linear section 41A extending in the Y-axis direction and connecting the plurality of linear sections 44A. The plurality of linear sections 44A extend from the linear section 41A toward the corresponding first portion 37A. Each linear section 44A extends from the linear section 41A in the +Z-axis direction and the -Z-axis direction. Each linear section 44A is, for example, linear. The plurality of linear sections 44A are, for example, parallel to each other. The linear section 41A is, for example, linear. Each linear section 44A is connected to the linear section 41A at its center.

[0099] Each first portion 37A of each pattern 33A, 34A includes a plurality of linear sections 42A extending in the Z-axis direction and a linear section 43A extending in the Y-axis direction and connecting the plurality of linear sections 42A. The plurality of linear sections 42A extend from the linear section 43A toward the corresponding second portion 38A. Each linear section 42A extends from the linear section 43A in the +Z-axis direction and the -Z-axis direction. Each linear section 42A is, for example, linear. The plurality of linear sections 42A are, for example, parallel to each other. The linear section 43A is, for example, linear. Each linear section 42A is connected to the linear section 43A at its center. The linear sections 41A and 43A of each pattern 33A, 34A are, for example, parallel to each other.

[0100] In the example shown in Figure 7, each linear section 42A includes a pair of tips 39A. Each tip 39A is spaced apart from other linear sections 42A and 43A of the same pattern, as well as from other patterns. Each linear section 44A includes a pair of tips 40A. Each tip 40A is spaced apart from other linear sections 44A and 41A of the same pattern, as well as from other patterns. Opposing tips 39A and tips 40A face each other. The shortest distance between two opposing tips 40A and 39A is smaller than the shortest distance between a portion of the first section 37A other than tip 39A and each tip 40A. The shortest distance between two opposing tips 39A and 40A is smaller than the shortest distance between a portion of the second section 38A other than tip 40A and each tip 39A. In other words, tip 39A is the portion of the linear section 42A containing this tip 39A that is closest to the corresponding linear section 44A. The tip 40A is the part of the linear section 44A that contains the tip 40A that is closest to the corresponding linear section 42A. The tip 39A is located closer to the linear section 42A than the other parts of the pattern that contain the tip 39A. The tip 40A is located closer to the linear section 42A than the other parts of the pattern that contain the tip 40A.

[0101] In each photoelectric conversion unit 23A, 24A, the linear portion 44A of the second portion 38A emits electrons in response to the incidence of electromagnetic waves when a lower potential is applied than the linear portion 42A of the first portion 37A. In this case, the linear portion 42A constitutes the bias portion, and the linear portion 44A constitutes the antenna portion. In each photoelectric conversion unit 23A, 24A, the linear portion 42A of the first portion 37A emits electrons in response to the incidence of electromagnetic waves when a lower potential is applied than the linear portion 44A of the second portion 38A. In this case, the linear portion 44A constitutes the bias portion, and the linear portion 42A constitutes the antenna portion. In other words, in each photoelectric conversion unit 23A, 24A, at least one of the first portion 37A and the second portion 38A serves as both the antenna portion and the bias portion.

[0102] The linear portions 42A of multiple patterns 33A and 34A have different lengths T4 and T5. In other words, the linear portions 42A of photoelectric conversion unit 23A and the linear portions 42A of photoelectric conversion unit 24A have different lengths T4 and T5. The lengths T4 and T5 of the linear portions 42A in each pattern 33A and 34A are the lengths in the Z-axis direction from one end 39A to the other end 39A of each linear portion 42A.

[0103] The linear portions 44A of multiple patterns 33A and 34A have different lengths T6 and T7. In other words, the linear portions 44A of photoelectric conversion unit 23A and the linear portions 44A of photoelectric conversion unit 24A have different lengths T6 and T7. The lengths T6 and T7 of the linear portions 44A in each pattern 33A and 34A are the lengths in the Z-axis direction from one end 40A to the other end 40A of each linear portion 44A.

[0104] In pattern 33A, the lengths T4 of the multiple linear sections 42A are the same. In pattern 34A, the lengths T5 of the multiple linear sections 42A are the same. In pattern 33A, the lengths T6 of the multiple linear sections 44A are the same. In pattern 34A, the lengths T7 of the multiple linear sections 44A are the same. The lengths T4 and T5 of the linear sections 42A in each pattern 33A and 34A correspond to the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion unit 23A and 24A when a potential lower than that of the linear section 42A is applied to the linear section 42A. The lengths T6 and T7 of the linear sections 44A in each pattern 33A and 34A correspond to the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion unit 23A and 24A when a potential lower than that of the linear section 44A is applied to the linear section 44A. For example, lengths T4, T5, or lengths T6, T7 have a length that is half the length of the central wavelength of the desired wavelength range. As described above, when electromagnetic waves transmitted through the support 21 etc. are incident on the linear portion 42, the refractive index of the transmitted support 21 etc. is also taken into consideration.

[0105] In the example shown in Figure 7, the electron-emitting member 20 further comprises a plurality of electrodes 71, 72, 73, 74 spaced apart from each other. The plurality of electrodes 71, 72, 73, 74 are electrically connected to at least one of the plurality of photoelectric conversion units 23A, 24A. In the example shown in Figure 7, the electron-emitting member 20 comprises two electrodes 71, two electrodes 72, two electrodes 73, and two electrodes 74. In the example shown in Figure 7, each electrode 71, 72, 73, 74 has a rectangular shape. As a modification, each electrode 71, 72, 73, 74 may have a linear shape similar to the first part 37A or the second part 38A. Each electrode 71, 72, 73, 74 may be formed integrally with the first part 37A or the second part 38A.

[0106] For example, each electrode 71 is electrically connected to one first part 37A of the photoelectric conversion unit 23A. Each electrode 72 is electrically connected to one second part 38A of the photoelectric conversion unit 23A. Each electrode 73 is electrically connected to one first part 37A of the photoelectric conversion unit 24A. Each electrode 74 is electrically connected to one second part 38A of the photoelectric conversion unit 24A.

[0107] In the example shown in Figure 7, each of the photoelectric conversion units 23A and 24A operates by receiving a potential from the power supply unit 60 via a plurality of electrodes 71, 72, 73, and 74. The potential application unit 61 of the power supply unit 60 applies a potential to each of the photoelectric conversion units 23A and 24A via the plurality of electrodes 71, 72, 73, and 74. The potential control unit 62 of the power supply unit 60 controls the potential applied to each of the photoelectric conversion units 23A and 24A.

[0108] In the electromagnetic wave detection method using an electron emission member in the second embodiment, for example, the process is performed in which processes S12 and S13 of the electromagnetic wave detection method shown in Figure 6 are omitted. In this case, process S14 is executed as a photoelectric conversion unit that operates both the photoelectric conversion unit 23A and the photoelectric conversion unit 24.

[0109] In each pattern 33A, if the lengths of each linear section 44A and each linear section 42A are different, processing S12 may be executed to change the potential applied to electrodes 71 and 72 according to the determined wavelength range. Similarly, in each pattern 34A, if the lengths of each linear section 44A and each linear section 42A are different, processing S12 may be executed to change the potential applied to electrodes 73 and 74 according to the determined wavelength range.

[0110] Next, with reference to Figure 8, the configuration of a modified example of the second embodiment will be described. Figure 8 is a plan view of the electron emission member in a modified example of the second embodiment. In this modified example, the electron emission member 20 has a metasurface 22B. The metasurface 22B is of the active type and operates by the application of a bias voltage. The metasurface 22B operates by being supplied with a potential by the power supply unit 60. In the example shown in Figure 8, the metasurface 22B includes a plurality of photoelectric conversion units 23B, 24B, 25B, 26B, and 27B. Each of the plurality of photoelectric conversion units 23B, 24B, 25B, 26B, and 27B corresponds to electromagnetic waves in different wavelength ranges. In other words, the plurality of photoelectric conversion units 23B, 24B, 25B, 26B, and 27B are sensitive to electromagnetic waves in different wavelength ranges. The photoelectric conversion units 23B, 24B, 25B, 26B, and 27B are arranged in the Y-axis direction. The photoelectric conversion units 23B, 24B, 25B, 26B, and 27B are arranged in the order of 27B, 26B, 25B, 24B, and 23B in the +Y axis direction.

[0111] Multiple photoelectric conversion sections 23B, 24B, 25B, 26B, and 27B in the metasurface 22B include patterns having different configurations. Each pattern is arranged on the main surface 21b of the support 21. Each pattern has a different shape. Photoelectric conversion section 23B includes pattern 31B, photoelectric conversion section 24B includes pattern 32B, photoelectric conversion section 25B includes pattern 33B, photoelectric conversion section 26B includes pattern 34B, and photoelectric conversion section 27B includes pattern 35B. Each pattern 31B, 32B, 33B, 34B, and 35B is a conductive line that conducts electrons. Each pattern 31B, 32B, 33B, 34B, and 35B 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.

[0112] Each pattern 31B, 32B, 33B, 34B, 35B includes a first part 37B and a second part 38B. In this modified example, each pattern 31B, 32B, 33B, 34B, 35B includes one first part 37B and one second part 38B. Each first part 37B of each pattern 31B, 32B, 33B, 34B, 35B includes a tip 39B. Each second part 38B of each pattern 31B, 32B, 33B, 34B, 35B includes a tip 40B. In adjacent first parts 37B and second parts 38B, the tips 39B and 40B face each other in the Z-axis direction. In each pattern 31B, 32B, 33B, 34B, 35B, the first part 37B and the second part 38B are connected via an oxide layer. In each pattern 31B, 32B, 33B, 34B, and 35B, the first part 37B and the second part 38B are separated by an oxide layer and are insulated from each other at least when the photoelectric converter 2 is not in operation.

[0113] The first part 37B emits electrons in response to incident electromagnetic waves when it is subjected to a lower potential than the second part 38B. Similarly, the second part 38B emits electrons in response to incident electromagnetic waves when it is subjected to a lower potential than the first part 37B. Therefore, each photoelectric conversion unit 23B, 24B, 25B, 26B, 27B can emit electrons from either the first part 37B or the second part 38B, depending on the potential state.

[0114] In the example shown in Figure 8, each first portion 37B of each pattern 31B, 32B, 33B, 34B, 35B includes linear sections 83B, 84B, 85B, 86B, 87B extending in the Z-axis direction and a linear section 82B extending in the Y-axis direction and connecting the multiple linear sections 83B, 84B, 85B, 86B, 87B. In other words, each first portion 37B of each pattern 31B, 32B, 33B, 34B, 35B is connected to one another by a single linear section 82B. The first portion 37B of pattern 31B includes linear section 83B and linear section 82B. The first portion 37B of pattern 32B includes linear section 84B and linear section 82B. The first portion 37B of pattern 33B includes linear section 85B and linear section 82B. The first part 37B of pattern 34B includes a linear portion 86B and a linear portion 82B. The first part 37B of pattern 35B includes a linear portion 87B and a linear portion 82B.

[0115] Multiple linear sections 83B, 84B, 85B, 86B, 87B extend from linear section 82B toward the corresponding second section 38B. Each linear section 83B, 84B, 85B, 86B, 87B extends from linear section 82B in the +Z-axis direction and the -Z-axis direction. Each linear section 83B, 84B, 85B, 86B, 87B is, for example, linear in shape. Multiple linear sections 83B, 84B, 85B, 86B, 87B are, for example, parallel to each other. Linear section 82B is, for example, linear in shape. Each linear section 83B, 84B, 85B, 86B, 87B is connected to linear section 82B at its center.

[0116] Each second part 38B of each pattern 31B, 32B, 33B, 34B, and 35B includes linear sections 93B, 94B, 95B, 96B, and 97B extending in the Z-axis direction, and a linear section 92B extending in the Y-axis direction and connecting multiple linear sections 93B, 94B, 95B, 96B, and 97B. In other words, each second part 38B of each linear section 93B, 94B, 95B, 96B, and 97B is connected to one another by a single linear section 92B. The second part 38B of pattern 31B includes linear section 93B and linear section 92B. The second part 38B of pattern 32B includes linear section 94B and linear section 92B. The second part 38B of pattern 33B includes linear section 95B and linear section 92B. The second part 38B of pattern 34B includes linear section 96B and linear section 92B. The second part 38B of pattern 35B includes linear section 97B and linear section 92B.

[0117] Multiple linear sections 93B, 94B, 95B, 96B, 97B extend from linear section 92B toward the corresponding first section 37B. Each linear section 93B, 94B, 95B, 96B, 97B extends from linear section 92B in the +Z axis direction and the -Z axis direction. Each linear section 93B, 94B, 95B, 96B, 97B is, for example, linear in shape. Multiple linear sections 93B, 94B, 95B, 96B, 97B are, for example, parallel to each other. Linear section 92B is, for example, linear in shape. Each linear section 93B, 94B, 95B, 96B, 97B is connected to linear section 92B at its center. For each pattern 31B, 32B, 33B, 34B, and 35B, the linear sections 82B and 92B are, for example, parallel to each other.

[0118] In the example shown in Figure 8, each linear section 83B, 84B, 85B, 86B, 87B includes a pair of tips 39B. Each tip 39B is spaced apart from other linear sections of the same pattern and from other patterns. Each linear section 93B, 94B, 95B, 96B, 97B includes a pair of tips 40B. Each tip 40B is spaced apart from other linear sections of the same pattern and from other patterns. Opposing tips 39B and tips 40B face each other. The shortest distance between opposing tips 39B and tips 40B is smaller than the shortest distance between a portion of the first section 37B other than the tips 39B and each tip 40B. The shortest distance between opposing tips 39B and tips 40B is smaller than the shortest distance between a portion of the second section 38B other than the tips 40B and each tip 39B. In other words, tip 40B is the part closest to the corresponding line shape 83B, 84B, 85B, 86B, 87B in the line shape sections 93B, 94B, 95B, 96B, 97B that include tip 40B. Tip 39B is the part closest to the corresponding line shape 93B, 94B, 95B, 96B, 97B in the line shape sections 83B, 84B, 85B, 86B, 87B that include tip 39B. Tip 39B is located closer to the line shape sections 93B, 94B, 95B, 96B, 97B than other parts of the pattern that include tip 39B. Tip 40B is located closer to the line shape sections 83B, 84B, 85B, 86B, 87B than other parts of the pattern that include tip 40B.

[0119] The shortest distance between linear sections 83B, 84B, 85B, 86B, 87B and linear sections 93B, 94B, 95B, 96B, 97B that face each other in the Z-axis direction is constant. For example, the shortest distance between linear section 83B and linear section 93B included in photoelectric conversion section 23B is the same as the shortest distance between linear section 84B and linear section 94B included in photoelectric conversion section 24B.

[0120] In each photoelectric conversion unit 23B, 24B, 25B, 26B, 27B, the linear sections 83B, 84B, 85B, 86B, 87B of the first section 37B emit electrons in response to the incidence of electromagnetic waves when they are given a lower potential than the linear sections 93B, 94B, 95B, 96B, 97B of the second section 38B. In this case, the linear sections 93B, 94B, 95B, 96B, 97B constitute the bias section, and the linear sections 83B, 84B, 85B, 86B, 87B constitute the antenna section. In each photoelectric conversion unit 23B, 24B, 25B, 26B, 27B, the linear sections 93B, 94B, 95B, 96B, 97B of the second section 38B emit electrons in response to the incidence of electromagnetic waves when a lower potential is applied than that of the linear sections 83B, 84B, 85B, 86B, 87B of the first section 37B. In this case, the linear sections 83B, 84B, 85B, 86B, 87B constitute the bias section, and the linear sections 93B, 94B, 95B, 96B, 97B constitute the antenna section. In other words, in each photoelectric conversion unit 23B, 24B, 25B, 26B, 27B, at least one of the first section 37B and the second section 38B serves as both the antenna section and the bias section.

[0121] The linear sections 83B, 84B, 85B, 86B, and 87B of multiple patterns 31B, 32B, 33B, 34B, and 35B have different lengths. For example, the length T8 of the linear section 83B of pattern 31B and the length T9 of the linear section 87B of pattern 35B are different. The lengths of the linear sections 83B, 84B, 85B, 86B, and 87B in each pattern 31B, 32B, 33B, 34B, and 35B are the lengths in the Z-axis direction from one end 39B to the other end 39B of each linear section 83B, 84B, 85B, 86B, and 87B. For example, length T8 is smaller than length T9.

[0122] In this embodiment, the length of the linear portion 86B is shorter than the length of the linear portion 87B. The length of the linear portion 85B is shorter than the length of the linear portion 86B. The length of the linear portion 84B is shorter than the length of the linear portion 85B. The length of the linear portion 83B is shorter than the length of the linear portion 84B. In other words, the linear portions 87B, 86B, 85B, 84B, and 83B are configured to become shorter as they move in the direction of the +Y axis.

[0123] The linear sections 93B, 94B, 95B, 96B, and 97B of multiple patterns 31B, 32B, 33B, 34B, and 35B have different lengths. For example, the length T10 of the linear section 93B of pattern 31B and the length T11 of the linear section 97B of pattern 35B are different. The lengths of the linear sections 93B, 94B, 95B, 96B, and 97B in each pattern 31B, 32B, 33B, 34B, and 35B are the lengths in the Z-axis direction from one end 40B to the other end 40B of each linear section 93B, 94B, 95B, 96B, and 97B. For example, length T10 is greater than length T11.

[0124] In this embodiment, the length of the linear portion 96B is greater than the length of the linear portion 97B. The length of the linear portion 95B is greater than the length of the linear portion 96B. The length of the linear portion 94B is greater than the length of the linear portion 95B. The length of the linear portion 93B is greater than the length of the linear portion 94B. In other words, the linear portions 97B, 96B, 95B, 94B, and 93B are configured to become longer as they move in the direction of the +Y axis.

[0125] The lengths of the linear sections 83B, 84B, 85B, 86B, and 87B correspond to the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion section 23B, 24B, 25B, 26B, and 27B when a lower potential is applied to the linear sections 83B, 84B, 85B, 86B, and 87B than the linear sections 93B, 84B, 95B, 96B, and 97B. The lengths of the linear sections 93B, 94B, 95B, 96B, and 97B correspond to the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion section 23B, 24B, 25B, 26B, and 27B when a lower potential is applied to the linear sections 93B, 84B, 85B, 86B, and 87B than the linear sections 93B, 94B, 95B, 96B, and 97B. For example, the lengths of the linear portions 83B, 84B, 85B, 86B, 87B, or the lengths of the linear portions 93B, 94B, 95B, 96B, 97B, are half the length of the central wavelength of the desired wavelength range. As described above, when electromagnetic waves transmitted through the support 21 etc. are incident on the linear portion 42, the refractive index of the transmitted support 21 etc. is also taken into consideration.

[0126] In the example shown in Figure 8, the electron-emitting member 20 further comprises a plurality of electrodes 71B, 72B spaced apart from each other. In the example shown in Figure 8, the electron-emitting member 20 comprises one electrode 71B and one electrode 72B. In the example shown in Figure 8, each electrode 71B, 72B has a rectangular shape. As a modification, each electrode 71B, 72B may have a linear shape similar to the first part 37B or the second part 38B. Each electrode 71B, 72B may be formed integrally with the first part 37B or the second part 38B.

[0127] For example, electrode 71B is electrically connected to the first portion 37B of each photoelectric conversion unit 23B, 24B, 25B, 26B, 27B. Electrode 72B is electrically connected to the second portion 38B of each photoelectric conversion unit 23B, 24B, 25B, 26B, 27B. In the example shown in Figure 8, each of the photoelectric conversion units 23B, 24B, 25B, 26B, 27B operates by receiving a potential from the power supply unit 60 via multiple electrodes 71B, 72B. The potential supply unit 61 of the power supply unit 60 supplies a potential to each of the photoelectric conversion units 23B, 24B, 25B, 26B, 27B via multiple electrodes 71B, 72B. The potential control unit 62 of the power supply unit 60 controls the potential supplied to the first portion 37B and the second portion 38B, respectively.

[0128] In the example shown in Figure 8, linear sections 83B, 84B, 85B, 86B, and 87B, which have different lengths, are connected to each other by linear section 82B. Therefore, when a potential lower than that of electrode 72B is applied to electrode 71B, electrons are emitted from linear sections 83B, 84B, 85B, 86B, and 87B in response to the incidence of electromagnetic waves in the wavelength range corresponding to each of the linear sections 83B, 84B, 85B, 86B, and 87B. In the example shown in Figure 8, linear sections 93B, 94B, 95B, 96B, and 97B, which have different lengths, are connected to each other by linear section 92B. Therefore, when a potential lower than that of electrode 71B is applied to electrode 72B, electrons are emitted from the linear portions 93B, 94B, 95B, 96B, and 97B in response to the incidence of electromagnetic waves in the wavelength range corresponding to each of the linear portions 93B, 94B, 95B, 96B, and 97B.

[0129] As shown in the example in Figure 8, the linear sections 83B, 84B, 85B, 86B, and 87B, which have different lengths, are connected by the same linear section 82B. The linear sections 93B, 94B, 95B, 96B, and 97B, which have different lengths, are connected by the same linear section 92B. With this configuration, a range of wavelengths of electromagnetic waves that can be converted into electrons is ensured with a more compact configuration. In other words, electromagnetic waves with different wavelength components can be detected simultaneously with a more compact configuration. Furthermore, the shortest distance between the linear sections 83B, 84B, 85B, 86B, and 87B that face each other in the Z-axis direction is constant. Therefore, the sensitivity of electromagnetic waves in each photoelectric conversion section 23B, 24B, 25B, 26B, and 27B is ensured.

[0130] Next, with reference to Figure 9, the configuration of yet another modification of the second embodiment will be described. Figure 9 is a plan view of the electron-emitting member in the modification of the second embodiment. In this modification, the electron-emitting member 20 has a metasurface 22C. The metasurface 22C is also of the active type and operates by the application of a bias voltage. This modification is generally similar to or the same as the example shown in Figure 8. The antenna portion of the metasurface 22B includes a dipole antenna, while the antenna portion of the metasurface 22C includes a diamond antenna. The differences between the modification shown in Figure 8 and the modification shown in Figure 9 will be mainly described below.

[0131] In the example shown in Figure 9, the metasurface 22C includes multiple photoelectric conversion units 23C, 24C, 25C, and 26C. Each of the multiple photoelectric conversion units 23C, 24C, 25C, and 26C corresponds to electromagnetic waves in different wavelength ranges. In other words, the multiple photoelectric conversion units 23C, 24C, 25C, and 26C are sensitive to electromagnetic waves in different wavelength ranges. The photoelectric conversion units 23C, 24C, 25C, and 26C are arranged in the order 26C, 25C, 24C, and 23C in the +Y axis direction.

[0132] The photoelectric conversion unit 23C includes pattern 31C, the photoelectric conversion unit 24C includes pattern 32C, the photoelectric conversion unit 25C includes pattern 33C, and the photoelectric conversion unit 26C includes pattern 34C. Each pattern 31C, 32C, 33C, and 34C corresponds to each pattern 31B, 32B, 33B, and 34B, and is made of the same material as each pattern 31B, 32B, 33B, and 34B.

[0133] Each pattern 31C, 32C, 33C, 34C includes a first part 37C and a second part 38C. Each first part 37C of each pattern 31C, 32C, 33C, 34C includes a tip 39C. Each second part 38C of each pattern 31C, 32C, 33C, 34C includes a tip 40C. Each first part 37C corresponds to each first part 37B, and each second part 38C corresponds to each second part 38B. Tip 39C corresponds to tip 39B, and tip 40C corresponds to tip 40B.

[0134] In the example shown in Figure 9, each first portion 37C of each pattern 31C, 32C, 33C, 34C includes a rhomboid portion 83C, 84C, 85C, 86C extending in the Z-axis direction and a linear portion 82C extending in the Y-axis direction and connecting the multiple rhomboid portions 83C, 84C, 85C, 86C, respectively. The linear portion 82C corresponds to the linear portion 82B. The rhomboid portions 83C, 84C, 85C, 86C correspond to the linear portions 83B, 84B, 85B, 86B.

[0135] Multiple rhombic sections 83C, 84C, 85C, and 86C extend from the linear section 82C toward the corresponding second section 38C. Each rhombic section 83C, 84C, 85C, and 86C extends from the linear section 82C in the +Z-axis direction and the -Z-axis direction. Each rhombic section 83C, 84C, 85C, and 86C is connected to the linear section 82C at its center. For example, the linear section 82C is connected to two vertices of each rhombic section 83C, 84C, 85C, and 86C.

[0136] In the example shown in Figure 9, each second part 38C of each pattern 31C, 32C, 33C, 34C includes a rhomboid portion 93C, 94C, 95C, 96C extending in the Z-axis direction and a linear portion 92C extending in the Y-axis direction and connecting the multiple rhomboid portions 93C, 94C, 95C, 96C. The linear portion 92C corresponds to the linear portion 92B. The rhomboid portions 93C, 94C, 95C, 96C correspond to the linear portions 93B, 94B, 95B, 96B. The rhomboid portions 93C, 94C, 95C, 96C differ from the linear portions 93B, 94B, 95B, 96B in that they exhibit a rhomboid shape.

[0137] Multiple rhombic sections 93C, 94C, 95C, and 96C extend from the linear section 92C toward the corresponding first section 37C. Each rhombic section 93C, 94C, 95C, and 96C extends from the linear section 92C in the +Z-axis direction and the -Z-axis direction. Each rhombic section 93C, 94C, 95C, and 96C is connected to the linear section 92C at its center. For example, the linear section 92C is connected to two vertices of each rhombic section 93C, 94C, 95C, and 96C.

[0138] In each photoelectric conversion section 23C, 24C, 25C, 26C, the rhombic sections 83C, 84C, 85C, and 86C of the first section 37C emit electrons in response to the incidence of electromagnetic waves when a lower potential is applied than that of the rhombic sections 93C, 94C, 95C, and 96C of the second section 38C. In this case, the rhombic sections 93C, 94C, 95C, and 96C constitute the bias section, and the rhombic sections 83C, 84C, 85C, and 86C constitute the antenna section. In this case, the rhombic sections 83C, 84C, 85C, and 86C constitute the bowtie antenna.

[0139] In each photoelectric conversion unit 23C, 24C, 25C, 26C, the diamond-shaped portions 93C, 94C, 95C, 96C of the second portion 38C emit electrons in response to the incidence of electromagnetic waves when a lower potential is applied than that of the diamond-shaped portions 83C, 84C, 85C, 86C of the first portion 37C. In this case, the diamond-shaped portions 83C, 84C, 85C, 86C constitute the bias portion, and the diamond-shaped portions 93C, 94C, 95C, 96C constitute the antenna portion. In this case, the diamond-shaped portions 93C, 94C, 95C, 96C constitute the bowtie antenna. In other words, in each photoelectric conversion unit 23C, 24C, 25C, 26C, at least one of the first portion 37C and the second portion 38C serves as both the antenna portion and the bias portion.

[0140] The rhomboid sections 83C, 84C, 85C, and 86C of multiple patterns 31C, 32C, 33C, and 34C have different lengths. For example, the length T12 of the rhomboid section 83C of pattern 31C and the length T13 of the rhomboid section 86C of pattern 34C are different. The lengths of the rhomboid sections 83C, 84C, 85C, and 86C in each pattern 31C, 32C, 33C, and 34C are the lengths in the Z-axis direction from one end 39C to the other end 39C of each rhomboid section 83C, 84C, 85C, and 86C. For example, length T12 is greater than length T13.

[0141] In this embodiment, the length of the rhombic portion 85C is greater than the length of the rhombic portion 86C. The length of the rhombic portion 84C is greater than the length of the rhombic portion 85C. The length of the rhombic portion 83C is greater than the length of the rhombic portion 84C. In other words, the rhombic portions 86C, 85C, 84C, and 83C are configured to become longer as they move in the direction of the +Y axis.

[0142] The rhomboid sections 93C, 94C, 95C, and 96C of multiple patterns 31C, 32C, 33C, and 34C have different lengths. For example, the length T14 of the rhomboid section 93C of pattern 31C and the length T15 of the rhomboid section 96C of pattern 34C are different. The length of the rhomboid sections 93C, 94C, 95C, and 96C in each pattern 31C, 32C, 33C, and 34C is the length in the Z-axis direction from one end 40C to the other end 40C of each rhomboid section 93C, 94C, 95C, and 96C.

[0143] In this embodiment, the length of the rhombic portion 95C is shorter than the length of the rhombic portion 96C. The length of the rhombic portion 94C is shorter than the length of the rhombic portion 95C. The length of the rhombic portion 93C is shorter than the length of the rhombic portion 94C. In other words, the rhombic portions 96C, 95C, 94C, and 93C are configured to become shorter as they move in the direction of the +Y axis.

[0144] In the example shown in Figure 9, the electron-emitting member 20 further comprises a plurality of electrodes 71C, 72C spaced apart from each other. In the example shown in Figure 9, electrode 71C corresponds to electrode 71B, and electrode 72C corresponds to electrode 72B.

[0145] As shown in the example in Figure 9, the rhombic sections 83C, 84C, 85C, and 86C, which have different lengths, are connected by the same linear section 82C. The rhombic sections 93C, 94C, 95C, and 96C, which have different lengths, are connected by the same linear section 92B. With this configuration, a more compact configuration ensures a range of wavelengths of electromagnetic waves that can be converted into electrons. In addition, the shortest distance between the rhombic sections 83C, 84C, 85C, and 86C facing each other in the Z-axis direction is constant. Therefore, the sensitivity of electromagnetic waves in each photoelectric conversion section 23C, 24C, 25C, and 26C is ensured.

[0146] In the example shown in Figure 9, the metasurface 22C includes a diamond antenna instead of a dipole antenna as its antenna section. The wavelength range to which the diamond antenna is sensitive is wider than the wavelength range to which the dipole antenna is sensitive. Therefore, electromagnetic waves with different wavelength components can be detected simultaneously, even with a more compact configuration. [Third Embodiment]

[0147] Next, the configuration of the electromagnetic wave detection device in the third embodiment will be described with reference to Figure 10. Figure 10 is a schematic diagram of the electromagnetic wave detection device in the second embodiment. This embodiment is generally similar to or the same as the embodiments and modifications described above. This embodiment differs from the embodiments and modifications described above in that the metasurface is of a passive type. The differences from the embodiments described above will be mainly explained below.

[0148] The electromagnetic wave detection device 1D includes a photoelectric converter 2D. The photoelectric converter 2D emits electrons in response to the incidence of electromagnetic waves. In this embodiment, the electromagnetic wave detection device 1D detects the incident electromagnetic waves based on the electrons emitted from the photoelectric converter 2D in response to the incidence of electromagnetic waves.

[0149] The electromagnetic wave detection device 1D comprises a housing 10, an electron-emitting member 20D, a holding member 30, an electron multiplier unit 40, and an electron collection unit 50. The electron-emitting member 20D, the holding member 30, the electron multiplier unit 40, and the electron collection unit 50 are arranged inside the housing 10. The photoelectric converter 2D comprises the housing 10 and the electron-emitting member 20D, and constitutes a part of the electromagnetic wave detection device 1. In this embodiment, the electromagnetic wave detection device 1D does not include a power supply unit 60.

[0150] The electron-emitting member 20D emits electrons in response to the incidence of electromagnetic waves. The electron-emitting member 20D has a metasurface 22D. The metasurface 22D is of a passive type and operates without the application of a bias voltage. The metasurface 22D is provided on the support 21. The metasurface 22D emits electrons in response to the incidence of electromagnetic waves.

[0151] The metasurface 22D 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 22D is rectangular in plan view. In a modified example of this embodiment, the metasurface 22D may be provided on the main surface 21a.

[0152] Next, the photoelectric conversion device 2D will be described in more detail with reference to Figures 11(a) and 11(b). Figure 11(a) is a plan view of the electron emission member in the third embodiment. The metasurface 22D includes a plurality of photoelectric conversion units 23D, 24D, 25D, and 26D. The photoelectric conversion units 23D, 24D, 25D, and 26D are arranged in the Z-axis direction.

[0153] Multiple photoelectric conversion units 23D, 24D, 25D, and 26D each emit electrons in response to incident light of their respective wavelengths. Photoelectric conversion units 23D and 25D correspond to electromagnetic waves in different wavelength ranges than photoelectric conversion units 24D and 26D. In other words, photoelectric conversion units 23D and 25D correspond to electromagnetic waves in different wavelength ranges than photoelectric conversion units 24D and 26D. Photoelectric conversion unit 23D and photoelectric conversion unit 25D correspond to electromagnetic waves in the same wavelength range. Photoelectric conversion unit 24D and photoelectric conversion unit 26D correspond to electromagnetic waves in the same wavelength range.

[0154] The photoelectric conversion units 23D, 24D, 25D, and 26D are at the same potential. The photoelectric conversion units 23D, 24D, 25D, and 26D are electrically connected to each other. In a modified example of this embodiment, the photoelectric conversion units 23D, 24D, 25D, and 26D may not be electrically connected to each other but may be connected to the same potential, for example, to ground.

[0155] In this embodiment, as in the example shown in Figure 2, the electromagnetic wave W incident on the housing 10 is incident on the photoelectric conversion units 23D, 24D, 25D, and 26D. As a result, the photoelectric conversion unit among the photoelectric conversion units 23D, 24D, 25D, and 26D that corresponds to the wavelength of the electromagnetic wave W emits electrons in response to the incidence of the electromagnetic wave W. Electrons emitted from at least one of the photoelectric conversion units 23D, 24D, 25D, and 26D 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.

[0156] As shown in Figure 11(a), the photoelectric conversion units 23D, 25D and 24D, 26D include patterns 33D, 34D, 35D, and 36D having different configurations. The patterns 33D and 35D of the photoelectric conversion units 23D, 25D and the patterns 34D and 36D of the photoelectric conversion units 24D, 26D have different shapes. The photoelectric conversion unit 23D and 25D include patterns 33D and 35D of the same shape. The photoelectric conversion unit 24D and 26D include patterns 34D and 36D of the same shape. Each pattern 33D, 34D, 35D, and 36D is a conductive line and conducts electrons. Each pattern 33D, 34D, 35D, and 36D 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. Patterns 33D, 34D, 35D, and 36D are at the same potential.

[0157] The electron-emitting member 20D further comprises a frame pattern 110D. The frame pattern 110 is electrically connected to each of the patterns 33D, 34D, 35D, and 36D. The patterns 33D, 34D, 35D, and 36D are electrically connected to each other via the frame pattern 110. The frame pattern 110 is provided on the main surface 21b of the support 21. The frame pattern 110 is provided along the edge of the main surface 21b so as to surround the patterns 33D, 34D, 35D, and 36D. The frame pattern 110 has, for example, a rectangular frame shape.

[0158] Each pattern 33D, 34D, 35D, 36D includes a plurality of linear portions 42D extending in the Z-axis direction and a linear portion 43D extending in the Y-axis direction and connecting the plurality of linear portions 42D. Each linear portion 42D, 43D is, for example, linear. The plurality of linear portions 42D are, for example, parallel to each other. The plurality of linear portions 42D have a tip 39D. The tip 39D of each pattern 33D, 34D, 35D, 36D is spaced apart from other linear portions 42D and linear portions 43D of the same pattern, as well as from other patterns. Although not shown in Figure 11(a), each pattern 33D, 34D, 35D, 36D may include a linear portion facing the tip 39D and connected to the linear portion 43D. Although not shown in Figure 11(a), each pattern 33D, 34D, 35D, and 36D may include line portions arranged to surround each line shape portion 42D.

[0159] Each linear section 42D emits electrons in response to the incidence of electromagnetic waves. In other words, the linear sections 42D constitute an antenna. The smaller the size of the antenna section, the more likely field electron emission is to occur for electromagnetic waves with shorter wavelengths, i.e., electromagnetic waves with higher frequencies. The photoelectric conversion sections 23D, 25D, 24D, and 26D of the metasurface 22D are configured to correspond to wavelengths in the frequency range of approximately 0.01 to 150 THz, so-called millimeter waves to infrared light, depending on the structure of the linear section 42D.

[0160] The linear portions 42D of at least two of the multiple photoelectric conversion units 23D, 25D, 24D, and 26D have different lengths. For example, the linear portions 42D of photoelectric conversion units 23D and 25D and the linear portions 42D of photoelectric conversion units 24D and 26D have different lengths T16 and T17. The lengths T16 and T17 of the linear portions 42D in each pattern 33D, 34D, 35D, and 36D are the lengths in the Z-axis direction from one end 39D to the other end 39D of the linear portion 42D.

[0161] In each pattern 33D and 35D, the length T16 of the multiple linear sections 42D is the same. In each pattern 34D and 36D, the length T17 of the multiple linear sections 42D is the same. The lengths T16 and T17 of the linear sections 42D in each pattern 33D, 34D, 35D, and 36D correspond to the wavelength range of the electromagnetic waves emitted by electrons in each photoelectric conversion section 23D, 24D, 25D, and 26D.

[0162] Figure 11(b) is a plan view of an electron-emitting member in a modified example of this embodiment. The metasurface 22E includes a plurality of photoelectric conversion units 23E, 24E, 25E, and 26E. The photoelectric conversion units 23E, 24E, 25E, and 26E are arranged in a matrix when viewed from the X-axis direction.

[0163] Multiple photoelectric conversion units 23E, 24E, 25E, and 26E each emit electrons in response to incident light of their respective wavelengths. The photoelectric conversion units 23E, 25E ​​and 24E, 26E correspond to electromagnetic waves in different wavelength ranges. In other words, the photoelectric conversion units 23E, 25E ​​and 24E, 26E are sensitive to electromagnetic waves in different wavelength ranges. Photoelectric conversion unit 23E and 25E correspond to electromagnetic waves in the same wavelength range. Photoelectric conversion unit 24E and 26E correspond to electromagnetic waves in the same wavelength band. The photoelectric conversion units 23E, 24E, 25E, and 26E are at the same potential. The photoelectric conversion units 23E, 24E, 25E, and 26E are electrically connected to each other.

[0164] In this modified example, as in the example shown in Figure 2, the electromagnetic wave W incident on the housing 10 is incident on the photoelectric conversion units 23E, 24E, 25E, and 26E. As a result, the photoelectric conversion unit among the photoelectric conversion units 23E, 24E, 25E, and 26E that corresponds to the wavelength of the electromagnetic wave W emits electrons in response to the incidence of the electromagnetic wave W. Electrons emitted from at least one of the photoelectric conversion units 23E, 24E, 25E, and 26E 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.

[0165] As shown in Figure 11(b), the photoelectric conversion units 23E, 25E ​​and 24E, 26E each contain patterns 33E, 34E, 35E, and 36E, which have different configurations. The patterns 33E, 35E of the photoelectric conversion units 23E, 25E ​​and the patterns 34E, 36E of the photoelectric conversion units 24E, 26E have different shapes. The photoelectric conversion unit 23E and the photoelectric conversion unit 25E contain patterns 33E, 35E with the same shape. The photoelectric conversion unit 24E and the photoelectric conversion unit 26E contain patterns 34E, 36E with the same shape. Each pattern 33E, 34E, 35E, and 36E is a conductive line and conducts electrons. Each pattern 33E, 34E, 35E, and 36E contains at least a metal layer formed on the oxide layer of the metasurface 22. The material of this metal layer is, for example, gold. Patterns 33E, 34E, 35E, and 36E are at the same potential.

[0166] In this modified example, the electron-emitting member 20E further comprises four interconnected frame patterns 110E. Each frame pattern 110E is electrically connected to each of the patterns 33E, 34E, 35E, and 36E. The patterns 33E, 34E, 35E, and 36E are electrically connected to each other via each frame pattern 110E. Each frame pattern 110E is provided on the main surface 21b of the support 21. Each frame pattern 110E is provided so as to surround the corresponding patterns 33E, 34E, 35E, and 36E. Each frame pattern 110E has, for example, a rectangular frame shape. Each frame pattern 110E demarcates the region where the photoelectric conversion unit 23E is provided, the region where the photoelectric conversion unit 24E is provided, the region where the photoelectric conversion unit 25E is provided, and the region where the photoelectric conversion unit 26E is provided.

[0167] Each pattern 33E, 34E, 35E, 36E includes a plurality of linear sections 42D extending in the Z-axis direction and a linear section 43D extending in the Y-axis direction and connecting the plurality of linear sections 42D. The tips 39D of the plurality of linear sections 42D are spaced apart from other linear sections 42D and linear sections 43D of the same pattern, as well as from other patterns. Although not shown in Figure 9, each pattern 33E, 34E, 35E, 36E may include linear sections facing the tips 39D and connected to the linear sections 43D. Although not shown in Figure 11(b), each pattern 33E, 34E, 35E, 36E may include linear sections arranged to surround each linear section 42D.

[0168] The linear sections 42D of the photoelectric conversion units 23E and 25E and the linear sections 42D of the photoelectric conversion units 24E and 26E have different lengths T18 and T19. In each pattern 33E and 35E, the length T18 of multiple linear sections 42D is the same. In each pattern 34E and 36E, the length T19 of multiple linear sections 42D is the same. The lengths T18 and T19 of the linear sections 42D in each pattern 33E, 34E, 35E, and 36E correspond to the wavelength range of the electromagnetic waves emitted by each photoelectric conversion unit 23E, 24E, 25E, and 26E.

[0169] As a modification of the third embodiment, the metasurface 22D may have at least one of the photoelectric conversion units 23B, 24B, 25B, 26B, 27B and 23C, 24C, 25C, 26C in the modification of the second embodiment, instead of the photoelectric conversion units 23D, 24D, 25D, 26D. For example, if the metasurface 22D has photoelectric conversion units 23B, 24B, 25B, 26B, 27B instead of the photoelectric conversion units 23D, 24D, 25D, 26D, both ends of the linear portion 82B and the linear portion 92B shown in Figure 8 are connected to the frame pattern 110D. If the metasurface 22D has photoelectric conversion units 23C, 24C, 25C, and 26C instead of photoelectric conversion units 23D, 24D, 25D, and 26D, then both ends of the linear sections 82C and 92C shown in Figure 9 are connected to the frame pattern 110D.

[0170] Similarly, the metasurface 22E may have at least one of the photoelectric conversion units 23B, 24B, 25B, 26B, 27B and 23C, 24C, 25C, 26C in the modified version of the second embodiment, instead of the photoelectric conversion units 23E, 24E, 25E, 26E. For example, if the metasurface 22E has photoelectric conversion units 23B, 24B, 25B, 26B, 27B instead of the photoelectric conversion units 23E, 24E, 25E, 26E, both ends of the linear portion 82B and the linear portion 92B shown in Figure 8 are connected to each frame pattern 110E. If the metasurface 22E has photoelectric conversion units 23C, 24C, 25C, and 26C instead of photoelectric conversion units 23E, 24E, 25E, and 26E, then both ends of the linear sections 82C and 92C shown in Figure 9 are connected to each frame pattern 110E. [Mechanism of Action and Effects]

[0171] In this photoelectric conversion device 2,2D, the electron-emitting members 20,20D,20E have metasurfaces 22,22A,22B,22C,22D,22E that emit electrons in response to the incidence of electromagnetic waves. The metasurfaces 22,22A,22B,22C,22D,22E include a plurality of photoelectric conversion units that are sensitive to electromagnetic waves in different wavelength ranges. For example, the plurality of photoelectric conversion units 23,24,25 of the metasurface 22 include patterns 33,34,35 having different configurations. The photoelectric conversion units 23,24 of the metasurface 22 include patterns 33,34 having different shapes. The shapes of the patterns 33,34 in each photoelectric conversion unit 23,24 are thought to be related to the wavelength range of the electromagnetic waves from which electrons are emitted in each photoelectric conversion unit 23,24. The plurality of photoelectric conversion units 23,24 are sensitive to electromagnetic waves in different wavelength ranges. Therefore, the photoelectric converter 2 is sensitive to electromagnetic waves of wavelengths corresponding to the photoelectric conversion unit 23 and electromagnetic waves of wavelengths corresponding to the photoelectric conversion unit 24. With this configuration, the photoelectric conversion unit 23 emits electrons in response to the incidence of electromagnetic waves in the wavelength range corresponding to the photoelectric conversion unit 23, and the photoelectric conversion unit 24 emits electrons in response to the incidence of electromagnetic waves in the wavelength range corresponding to the photoelectric conversion unit 24. The same applies to the photoelectric converter 2B. As described above, the range of wavelengths of electromagnetic waves that can be converted into electrons is expanded in the photoelectric converters 2 and 2D.

[0172] The electromagnetic wave detection device 1,1D, equipped with photoelectric converters 2,2D, requires no cooling, and also does not require a spectrometer or optical filter. In the photoelectric converters 2,2D, the metasurfaces 22,22A,22B,22C,22D,22E that emit electrons in response to electromagnetic wave incidence are expanded simply by expanding the area on which the pattern is placed. Therefore, in the electromagnetic wave detection device 1,1D, the area on which electromagnetic waves are incident can be expanded more easily and inexpensively than in detection devices using a spectrometer or optical filter.

[0173] The photoelectric converter 2 has active-type metasurfaces 22, 22A, 22B, and 22C that operate by applying an electric potential. For example, in the metasurface 22 of the photoelectric converter 2, the patterns 33 and 34 of each photoelectric conversion unit 23 and 24 include a first portion 37 and a second portion 88 that are spaced apart from each other. The second portion 38 includes a tip 39 that faces the first portion 37. The second portion 38 emits electrons in response to the incidence of electromagnetic waves when a lower electric potential than that of the first portion 37 is applied. In this case, the sensitivity of each photoelectric conversion unit 23 and 24 is improved.

[0174] Furthermore, the operating photoelectric conversion unit can be switched by controlling the application of potential to the first part 37 and the second part 38 of the metasurface 22. For example, since the multiple photoelectric conversion units 23 and 24 emit electrons in response to the incidence of electromagnetic waves in different wavelength ranges, the wavelength range in which electrons are emitted can be switched by controlling the operating photoelectric conversion unit. Therefore, by controlling the application of potential to the first part 37 and the second part 38, the wavelength range of electromagnetic waves from which electrons are emitted in the photoelectric conversion device 2 can be controlled. The photoelectric conversion device 2 can emit electrons in response to the incidence of electromagnetic waves having wavelength components within the wavelength range corresponding to each photoelectric conversion unit, even without optical elements such as a spectrometer and optical filters.

[0175] The electromagnetic wave detection device 1, equipped with the photoelectric conversion device 2 described above, can also detect electromagnetic waves for each wavelength range corresponding to each photoelectric conversion unit 23, 24, similar to detection by spectroscopy. The electromagnetic wave detection device 1 can, for example, simultaneously detect the presence or absence of electromagnetic waves having wavelength components within multiple wavelength ranges. The electromagnetic wave detection device 1 can also expand or contract the range of wavelengths of electromagnetic waves to be detected depending on the situation.

[0176] For example, in the metasurface 22 of the photoelectric conversion device 2, the second portion 38 of each photoelectric conversion unit 23, 24 includes a linear portion 42 extending toward the first portion 37. The linear portion 42 of the photoelectric conversion unit 23 and the linear portion 42 of the photoelectric conversion unit 24 have different lengths. Depending on the length of the linear portion 42, the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion unit 23, 24 changes. Therefore, with a simple configuration, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric conversion device 2 can be expanded.

[0177] For example, in multiple photoelectric conversion units 23, 24, the first part 37 or second part 38 of the photoelectric conversion unit 23 and the first part 37 or second part 38 of the photoelectric conversion unit 24 are electrically connected. In the metasurface 22, the second part 38 of the photoelectric conversion unit 23 and the second part 38 of the photoelectric conversion unit 24 are electrically connected. In this case, a simpler configuration can be used to expand the wavelength range of electromagnetic waves that can be converted into electrons in the photoelectric conversion device 2.

[0178] The photoelectric conversion device 2 includes, for example, a potential control unit 62 that controls the potential applied to the first part 37 and the second part 38 of each photoelectric conversion unit 23, 24, and 25. In this case, the potential control unit 62 selects which photoelectric conversion unit to operate.

[0179] The potential control unit 62 controls, for example, the potential applied to the first and second parts 37, 38 of the photoelectric conversion unit 23 and the first and second parts 37, 38 of the photoelectric conversion unit 24. The potential difference between the potential applied to the first part 37 of the photoelectric conversion unit 23 and the potential applied to the second part 38 of the photoelectric conversion unit 23, and the potential difference between the potential applied to the first part 37 of the photoelectric conversion unit 24 and the potential applied to the second part 38 of the photoelectric conversion unit 24, may be different from each other. In this case, the photoelectric conversion unit 23 and the photoelectric conversion unit 24 can operate independently. Therefore, the photoelectric conversion device 2 can change the range of wavelengths of electromagnetic waves that can be converted into electrons. In other words, the photoelectric conversion device 2 emits electrons in response to the incidence of electromagnetic waves having wavelength components within a desired wavelength range among a plurality of wavelength ranges corresponding to a plurality of photoelectric conversion units. For this reason, the electromagnetic wave detection device 1 can also detect electromagnetic waves for each wavelength range corresponding to each photoelectric conversion unit 23, 24, for example, similar to detection by spectroscopy. The electromagnetic wave detection device 1 can also expand or contract the range of wavelengths of electromagnetic waves to be detected, depending on the situation.

[0180] For example, when the potential control unit 62 applies a potential lower to the second part 38 of the photoelectric conversion unit 24 than the potential applied to the first part 37 of the photoelectric conversion unit 24, it applies a potential higher to the second part 38 of the photoelectric conversion unit 23 than the potential applied to the first part 37 of the photoelectric conversion unit 23. In this case, the photoelectric conversion unit 24 is in a state where it emits electrons in response to the incidence of electromagnetic waves, while the emission of electrons from the photoelectric conversion unit 23 in response to the incidence of electromagnetic waves can be reliably stopped.

[0181] The potential control unit 62 applies a potential to the second part 38 that is lower than the potential applied to the first part 37 in at least two of the multiple photoelectric conversion units 23, 24, and 25. In this case, the at least two photoelectric conversion units are operated simultaneously. Therefore, for example, the conversion of electromagnetic waves in the wavelength range corresponding to photoelectric conversion unit 23 to electrons and the conversion of electromagnetic waves in the wavelength range corresponding to photoelectric conversion unit 24 to electrons can be performed simultaneously. As a result, the electromagnetic wave detection device 1 can, for example, detect the presence or absence of electromagnetic waves having wavelength components within multiple wavelength ranges at once.

[0182] The photoelectric converter 2D has passive type metasurfaces 22D, 22E that operate without the application of a potential. In this case, the electromagnetic wave detection device 1D equipped with the photoelectric converter 2D can simultaneously detect, for example, the presence or absence of electromagnetic waves having wavelength components within multiple wavelength ranges. In the photoelectric converter 2D, the patterns 33D, 33E of the photoelectric conversion units 23D, 23E and the patterns 34D, 34E of the photoelectric conversion units 24D, 24E are at the same potential. In this case, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric converter 2B can be expanded with a simpler configuration.

[0183] In the photoelectric converter 2D, the patterns 33D and 33E of the photoelectric conversion units 23D and 23E and the patterns 34D and 34E of the photoelectric conversion units 24D and 24E are electrically connected to each other. In this case, a simpler configuration can be used to expand the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric converter 2D.

[0184] In the photoelectric converter 2D, the patterns of each photoelectric conversion unit 23D, 25D, 24D, and 26D include linear sections. The linear sections 42D of at least two of the multiple photoelectric conversion units 23D, 25D, 24D, and 26D have different lengths. For example, the linear sections 42D of photoelectric conversion units 23D and 23E and the linear sections 42D of photoelectric conversion units 24D and 24E have different lengths. Depending on the length of the linear section 42D, the wavelength range of electromagnetic waves from which electrons are emitted in each photoelectric conversion unit changes. Therefore, the range of wavelengths of electromagnetic waves that can be converted into electrons in the photoelectric converter 2D can be expanded with a simpler configuration.

[0185] The electromagnetic wave detection device 1,1D further includes a housing 10 that is sealed and has a window portion 11a that transmits electromagnetic waves. The electron emission members 20,20D are arranged inside the housing 10. 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 10 or filling the housing 10 with gas. [Explanation of symbols]

[0186] 2,2B,2D… Photoelectric conversion device, 10…Houjing, 20,20D,20E…Electron emission components, 22,22A,22B,22C,22D,22E…Metal service, 23,23A,23B,23C,23D,23E,24,24A,24B,24C,24D,24E,25,25B,25C,25D,25E,26B,26C,26D,26E,27B…Photoelectric conversion unit, 31B,31C,32B,32C,33,33A,33B,33C,33D,33E,34,34A,34B,34C,34D,34 E,35,35B,35D,35E,36D,36E…Pattern, 37,37A,37B,37C…First part, 37,38,38A,38B,38C,88…Second part, 39,39A,39B,39C,39D,40A,40B,40C…Terminal, 41,41A,42,42A,42D,43,43A,43D,44A,82B,82C,83B,84B,85B,86B,87B,92B,92C,93B,94B,95B,96B,97B…Linear part, 62…Potential control part, E…Electron, W…Electromagnetic wave.

Claims

1. The electron-emitting member has a metasurface that emits electrons in response to the incidence of electromagnetic waves, The metasurface includes a plurality of photoelectric conversion units that are sensitive to electromagnetic waves in different wavelength ranges. The plurality of photoelectric conversion units include patterns having different configurations from each other. Each of the aforementioned photoelectric conversion units includes a first and second portion that are spaced apart from each other. The second portion includes a tip facing the first portion, and emits electrons in response to the incidence of electromagnetic waves when a lower potential is applied to it than to the first portion. Each of the photoelectric conversion units includes a linear portion that extends toward the first portion. A photoelectric conversion device in which the linear portions of at least two of the plurality of photoelectric conversion units have different lengths from each other.

2. The photoelectric conversion device according to claim 1, wherein in two of the plurality of photoelectric conversion units, the first or second portion of one of the photoelectric conversion units and the first or second portion of the other photoelectric conversion unit are electrically connected.

3. The photoelectric conversion device according to claim 1, further comprising a potential control unit that controls the potential applied to the first and second portions of each of the photoelectric conversion units.

4. The aforementioned plurality of photoelectric conversion units include a first photoelectric conversion unit and a second photoelectric conversion unit, The potential control unit controls the potential applied to the first and second parts of the first photoelectric conversion unit and the first and second parts of the second photoelectric conversion unit. The photoelectric conversion device according to claim 3, wherein the potential difference between the potential applied to the first part of the first photoelectric conversion unit and the potential applied to the second part of the first photoelectric conversion unit, and the potential difference between the potential applied to the first part of the second photoelectric conversion unit and the potential applied to the second part of the second photoelectric conversion unit are different from each other.

5. The photoelectric conversion apparatus according to claim 4, wherein when the potential control unit applies a potential lower than the potential applied to the first part of the second photoelectric conversion unit to the second part of the second photoelectric conversion unit, it applies a potential higher than the potential applied to the first part of the first photoelectric conversion unit to the second part of the first photoelectric conversion unit.

6. The photoelectric conversion apparatus according to claim 3, wherein the potential control unit applies a potential lower than the potential applied to the first part to at least two of the plurality of photoelectric conversion units to the second part.

7. The photoelectric conversion device according to claim 1, wherein the patterns of each of the photoelectric conversion units are at the same potential.

8. The photoelectric conversion device according to claim 1, wherein the patterns of each of the photoelectric conversion units are electrically connected to one another.

9. 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 8, wherein the electron-emitting member is disposed within the housing.

10. The process involves injecting the electromagnetic wave to be measured into a metasurface that includes multiple photoelectric conversion units, each containing patterns with different configurations, The system includes emitting electrons from at least one of the plurality of photoelectric conversion units that corresponds to the wavelength range of the electromagnetic wave to be measured, Each of the patterns of the photoelectric conversion unit includes a first portion and a second portion which is spaced apart from the first portion and has a tip facing the first portion. Each of the photoelectric conversion units emits electrons in response to the incidence of electromagnetic waves when a potential lower than the potential applied to the first part is applied to the second part. Each of the photoelectric conversion units includes a linear portion that extends toward the first portion. A photoelectric conversion method wherein the linear portions of at least two of the plurality of photoelectric conversion units have different lengths from each other.

11. The system further includes controlling the potential applied to the plurality of photoelectric conversion units. The photoelectric conversion method according to claim 10, wherein the potential applied to the first and second parts of each of the photoelectric conversion units is controlled.

12. The photoelectric conversion method according to claim 11, wherein the potentials applied to the first photoelectric conversion unit and the second photoelectric conversion unit included in the plurality of photoelectric conversion units are controlled to be different in terms of the potential difference between the potential applied to the first part of the first photoelectric conversion unit and the potential applied to the second part of the first photoelectric conversion unit, and the potential difference between the potential applied to the first part of the second photoelectric conversion unit and the potential applied to the second part of the second photoelectric conversion unit.

13. When a potential lower than the potential applied to the first part of the second photoelectric conversion unit is applied to the second part of the second photoelectric conversion unit, a potential higher than the potential applied to the first part of the first photoelectric conversion unit is applied to the second part of the first photoelectric conversion unit. The photoelectric conversion method according to claim 12, wherein when a potential lower than the potential applied to the first part of the first photoelectric conversion unit is applied to the second part of the first photoelectric conversion unit, a potential higher than the potential applied to the first part of the second photoelectric conversion unit is applied to the second part of the second photoelectric conversion unit.

14. The photoelectric conversion method according to any one of claims 11 to 13, wherein in at least two of the plurality of photoelectric conversion units, a potential lower than the potential applied to the first unit is applied to the second unit.

Images