High-frequency generator and high-frequency generation method

Abstract

To provide a high-output high-frequency generator having a simple configuration.SOLUTION: The high frequency generator (10) is provided with a voltage generation part (12) for generating a voltage by the irradiation of feed light, a photodiode (11) for generating electrons by the photoelectric conversion of signal light and converting the electrons into a current by the voltage, and an antenna (13) for radiating radio waves on the basis of the current. The high frequency generation device may include a vacuum package (14), and the voltage generation unit, the photodiode, and the antenna may be provided in the vacuum package.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a high frequency generating device including a photodiode and a high frequency generating method. [Background technology]

[0002] With the increase in communication traffic, there is a need to increase the capacity of wireless networks as the last access point, eliminate the speed difference between wired and wireless networks, and enable high-speed wireless interfaces. Terahertz waves (electromagnetic waves with a carrier frequency of approximately 100 GHz or higher) are attracting attention as a technology that can achieve these goals. In particular, for short-distance, high-capacity wireless technology, the development of high-speed wireless interfaces using terahertz waves is an urgent issue.

[0003] The following method, for example, is used to generate terahertz waves. When two light waves with different optical frequencies, i.e., different wavelengths, are input to a photodiode, an electron flow is generated in the p-type semiconductor photoelectric conversion layer (cathode electrode layer), which has a small band gap. The amount of this electron flow changes at the same frequency as the optical frequency difference between the two input light waves. This electron flow is made to travel through the electron transit layer and reach the n-type semiconductor collector layer (anode electrode layer), where terahertz waves are emitted from an antenna connected to the p-type semiconductor photoelectric conversion layer (cathode electrode layer) and the n-type semiconductor collector layer (anode electrode layer).

[0004] As a technology for generating terahertz waves, a configuration in which electrons generated in a photoelectric conversion layer flow through an electron transit layer is described (Patent Document 1). In this document, the anode and cathode are defined in the opposite way to the specification of the present application.

[0005] In this technology, electrons generated in the photoelectric conversion layer (p-type absorber) of the photodiode travel within the electron transit layer. The electrical capacitance of the region where the electrons travel is the electrical capacitance of the photodiode, and the upper limit frequency of the AC current that the photodiode can generate decreases in inverse proportion to this electrical capacitance. Specifically, the upper limit frequency f of the photodiode is f=1 / 2πCR. Here, C is the electrical capacitance of the electron transit layer, and R is the impedance of the antenna. The electrical capacitance C of the electron transit layer is determined by the area S of the photoelectric conversion layer, the thickness d, and the relative dielectric constant ε r , using the dielectric constant of vacuum ε0, C=ε0ε r S / d. Since the electron transport layer is a semiconductor, ε r is 10 or more. In order to increase the emitted terahertz waves, it is necessary to increase the intensity of the incident light waves and the amount of AC current generated, but there is an upper limit to the current density that can be tolerated in semiconductors. Therefore, if the area is increased to increase the amount of current, the capacitance C increases according to the above formula, and the upper limit frequency decreases. Thus, there has been a problem in that high-frequency operation and high output cannot be achieved at the same time. For example, at a frequency of 300 GHz, the upper limit of output is 100 μW.

[0006] To solve this problem, a vacuum photodiode has been disclosed that uses a vacuum space with a dielectric constant one-tenth that of a semiconductor as the electron transport layer (Reference 2). This allows the area of ​​the photoelectric conversion layer to be increased while maintaining the small capacitance required for 300 GHz response, thereby increasing the amount of current. Since the terahertz wave output radiated from the antenna is proportional to the square of the amount of current, increasing the amount of current increases the terahertz wave output.

[0007] FIG. 2 shows a configuration for generating high-frequency waves (terahertz waves) using a conventional vacuum photodiode. This configuration includes a module 20 in which a vacuum photodiode 21 is mounted in a vacuum package 24, and a DC power supply 22 for applying voltage to the vacuum photodiode 21. The vacuum photodiode 21 and DC power supply 22 are connected via a voltage application terminal 26 and an electrical cable 27. A vacuum space 25 is formed within the vacuum package 24. The vacuum photodiode 21 is formed as a chip measuring several square millimeters. The chip vacuum photodiode 21 includes a photoelectric conversion layer with a diameter of approximately 10 μm, and an antenna 23 for outputting high-frequency waves (terahertz waves) 3 is integrated on the back surface of the photodiode 21. At least the top surface of the vacuum package 24 is made of a material that transmits signal light, and the bottom surface is made of a material that transmits terahertz waves. Examples of such materials include quartz glass. In this photodiode, the area of ​​the photoelectric conversion layer can be increased by ten times without increasing the electrical capacitance, thereby enabling a tenfold increase in the amount of current. As a result, the terahertz wave output power emitted from the antenna can be increased to 10mW, 100 times the previous upper limit of 100μW.

[0008] Cited Document 2 discloses an example in which a cathode is disposed inside a vacuum tube and an anode is disposed on the inner wall of the vacuum tube, with wiring extending from each to the outside of the vacuum tube. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] J. Appl. Phys. 127, 031101 (2020); doi: 10.1063 / 1.5128444. [Non-patent document 2] Rev. Sci. Instrum. 68 (2), pp. 1142-1148 (1997). Summary of the Invention [Problem to be solved by the invention]

[0010] In conventional vacuum photodiodes, the entire photodiode is mounted in a vacuum package to form a vacuum space, and a voltage is applied between the cathode electrode layer and the anode electrode layer from a DC power supply outside the vacuum package via a voltage application terminal inside the vacuum package. In this configuration, the voltage application terminal must be formed by penetrating the wall of the vacuum package, which causes problems such as a deterioration in the degree of vacuum and an increase in the cost of the module components. [Means for solving the problem]

[0011] In order to solve the above-mentioned problems, the high frequency generator according to the present invention includes a voltage generating unit that generates a voltage by irradiating a power supply light, a photodiode that generates electrons by photoelectric conversion of signal light and converts the electrons into a current by the voltage, and an antenna that emits radio waves based on the current.

[0012] Furthermore, a radio frequency generating method according to the present invention is a method for generating radio frequency using a radio frequency generating device including a voltage generating unit, a photodiode, and an antenna, and includes the steps of: the voltage generating unit generating a voltage by irradiating power supply light; the photodiode generating electrons by photoelectric conversion of two signal lights having different frequencies, and converting the electrons into an alternating current by the voltage in accordance with the frequency difference between the two signal lights; and the antenna emitting radio waves based on the alternating current. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a high-output radio frequency generating device and a radio frequency generating method having a simple configuration. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a high frequency generator according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a conventional high-frequency generator. DETAILED DESCRIPTION OF THE INVENTION

[0015] First Embodiment A high frequency generator according to a first embodiment of the present invention will be described with reference to FIG.

[0016] <Configuration of high frequency generator> 1, a radio frequency generator 10 according to this embodiment includes a vacuum photodiode 11, a voltage generating unit 12, an antenna 13, and a vacuum package 14. In the radio frequency generator 10, a vacuum space 15 is formed within the vacuum package 14. The term "vacuum" refers to a state in which the space is filled with a gas at a pressure lower than atmospheric pressure, and includes an absolute vacuum.

[0017] The vacuum photodiode 11 includes a photoelectric conversion layer (cathode layer) made of a p-type semiconductor, an anode layer made of an n-type semiconductor, a cathode electrode, and an anode electrode.

[0018] By disposing the vacuum photodiode 11 in the vacuum package 14, the electron transit layer between the photoelectric conversion layer (cathode layer) and the anode layer of the vacuum photodiode 11 becomes a vacuum.

[0019] The voltage generating unit 12 is, for example, a solar cell, and is mounted in a vacuum package 14. The output of the voltage generating unit 12 is connected to the cathode electrode and the anode electrode of the vacuum photodiode 11.

[0020] The antenna 13 is disposed on the back surface of the vacuum photodiode 11 .

[0021] The appropriate length of antenna 13 is approximately half the wavelength of the emitted radio wave. Since the wavelength of 300 GHz is 1 mm, the appropriate length of antenna 13 is 0.5 mm, which allows integration onto the chip of vacuum photodiode 11, which is several mm square (1 mm to 5 mm).

[0022] At least the upper surface of the vacuum package 14 is made of a material that transmits the signal light 1 and the power supply light 2, and the lower surface is made of a material that transmits the high frequency wave (terahertz wave) 3. These materials include, for example, quartz glass.

[0023] When signal light 1 is incident on the vacuum photodiode 11, electrons are generated by photoelectric conversion in the photoelectric conversion layer (cathode layer) of the photodiode 11.

[0024] Moreover, a direct current voltage (electromotive force) required for photoelectric conversion is generated by irradiating the solar cell with the power supply light 2. The power supply light 2 is, for example, visible light.

[0025] This voltage is applied to the cathode electrode and anode electrode of the vacuum photodiode 11. As a result, the applied voltage causes electrons generated by photoelectric conversion to travel through the electron transit layer, which is a vacuum space, i.e., the electrons are converted into current.

[0026] To generate terahertz waves, two light waves with different optical frequencies (different wavelengths) are incident on a photodiode 11 as signal light 1, and an AC current with the same frequency as the optical frequency difference between the two light waves is generated by photoelectric conversion.

[0027] The alternating current is fed to an antenna 13 connected to a photodiode 11 , and the terahertz wave 3 is emitted from the antenna 13 .

[0028] For example, when photodiode 11 is simultaneously irradiated with laser light having an optical frequency of 193.0 THz and laser light having an optical frequency of 193.3 THz, an alternating current having a frequency of 0.3 THz, which is the frequency difference between these laser lights, or 300 GHz, is supplied to antenna 13. Radio waves 3 having a frequency of 300 GHz are emitted from antenna 13, which is located on the back surface of the photodiode 11 chip, through the underside of vacuum package 14 and into the air.

[0029] The frequency difference of the input light (for example, laser light) may be 0.1 THz to 10 THz, and is preferably 0.1 THz to 3 THz.

[0030] According to the high frequency generator of this embodiment, a voltage generated by irradiating a voltage generating unit mounted in a vacuum package with power supply light 2 can be applied to a vacuum photodiode to operate the vacuum photodiode. This eliminates the need to apply a voltage to the vacuum photodiode from outside the vacuum package, and eliminates the need for a voltage application terminal. As a result, a vacuum photodiode module can be realized that is simple in configuration, highly airtight, and low-cost.

[0031] Furthermore, the high frequency generator according to this embodiment has a small electrical capacity necessary for high frequency, especially terahertz, response, and can increase the area of ​​the photoelectric conversion layer, increase the amount of current, and increase the output of terahertz waves.

[0032] In the embodiment of the present invention, an example has been shown in which a vacuum photodiode is used, but a photodiode in which the electron transit layer is formed of a gas such as the atmosphere may also be used, or a photodiode in which a semiconductor is used for the electron transit layer may also be used.

[0033] In the embodiment of the present invention, an example has been shown in which two light waves with different wavelengths are incident on a photodiode to generate terahertz waves, but a configuration in which an optical signal with a single wavelength is received by a photodiode may also be used.

[0034] In the embodiments of the present invention, examples of the structure, dimensions, materials, etc. of each component in the configuration of the radio frequency generator and the radio frequency generation method are shown, but the present invention is not limited to these examples. Anything that can demonstrate the functions and effects of the radio frequency generator and the radio frequency generation method may be used.

[0035] It should be noted that the present invention is not limited to the above-described embodiments, and it is clear that many modifications and combinations can be made by a person having ordinary knowledge in the art within the technical concept of the present invention.

[0036] A part or all of the above-described embodiment or an example thereof can be described as, but is not limited to, the following supplementary notes.

[0037] (Appendix 1) A high frequency generator comprising: a voltage generating unit that generates a voltage by irradiation with power supply light; a photodiode that generates electrons by photoelectric conversion of signal light and converts the electrons into current by the voltage; and an antenna that emits radio waves based on the current.

[0038] (Supplementary Note 2) The high frequency generator according to Supplementary Note 1, comprising a vacuum package, in which the voltage generating unit, the photodiode, and the antenna are provided.

[0039] (Appendix 3) The high frequency generating device according to appendix 1 or appendix 2, wherein the signal light is two signal lights, the two signal lights have different frequencies, and the radio wave, which is a terahertz wave, is emitted based on the frequency difference between the two signal lights.

[0040] (Appendix 4) A method for generating a high frequency wave using a high frequency wave generating device including a voltage generating unit, a photodiode, and an antenna, the method comprising the steps of: the voltage generating unit generating a voltage by irradiating power supply light; the photodiode generating electrons by photoelectric conversion of two signal lights having different frequencies, and converting the electrons into an alternating current by the voltage in accordance with the frequency difference between the two signal lights; and the antenna emitting radio waves based on the alternating current.

[0041] (Appendix 5) The high-frequency generating device according to any one of Appendices 1 to 3, wherein the photodiode comprises a photoelectric conversion layer made of a p-type semiconductor, an anode layer made of an n-type semiconductor, a cathode electrode, and an anode electrode, and a vacuum is formed between the photoelectric conversion layer and the anode layer.

[0042] (Appendix 6) The high frequency generator according to any one of Appendices 1 to 3 and 5, wherein the length of the antenna is about half the wavelength of the radio wave.

[0043] (Appendix 7) A high-frequency generator according to any one of Appendices 1 to 3, 5 and 6, having a size of 1 mm square or more and 5 mm square or less. [Industrial Applicability]

[0044] The present invention relates to an apparatus and method for generating high frequency waves, particularly terahertz waves, and is applicable to communication systems and their interfaces. [Explanation of symbols]

[0045] 10 High frequency generator 11 Photodiode 12 Voltage generation section 13 Antenna

Claims

1. a voltage generating unit that generates a voltage by irradiation with power supply light; a photodiode that generates electrons by photoelectric conversion of signal light and converts the electrons into a current using the voltage; an antenna that emits radio waves based on the current; A high frequency generating device comprising:

2. Equipped with vacuum packaging, The high frequency generator according to claim 1 , wherein the voltage generating unit, the photodiode, and the antenna are contained in the vacuum package.

3. the signal light is two signal lights, the two signal lights have different frequencies, and the radio wave, which is a terahertz wave, is emitted based on the frequency difference between the two signal lights; 3. The high frequency generator according to claim 1 or 2.

4. A method for generating a high frequency wave using a high frequency wave generating device including a voltage generating unit, a photodiode, and an antenna, comprising: a step in which the voltage generating unit generates a voltage by irradiating the power supply light; a step in which the photodiode generates electrons by photoelectric conversion of two signal lights having different frequencies, and converts the electrons into an AC current according to the frequency difference between the two signal lights using the voltage; the antenna radiating radio waves based on the AC current; A high frequency generation method comprising:

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