Terahertz system

Abstract

A terahertz system (10) comprises: a plurality of first terahertz elements (21) that oscillate and detect terahertz waves; a plurality of second terahertz elements (22) that oscillate and detect terahertz waves; and a control device (30) configured to switch between a first state in which the plurality of first terahertz elements (21) oscillate terahertz waves and the plurality of second terahertz elements (22) detect the terahertz waves, and a second state in which the plurality of second terahertz elements (22) oscillate terahertz waves and the first terahertz elements (21) detect the terahertz waves.

Description

Terahertz System

[0001] The present disclosure relates to terahertz systems.

[0002] In recent years, as electronic devices such as transistors have become increasingly miniaturized and scaled down to nanoscale, a phenomenon known as the quantum effect has become apparent. Development is underway to utilize this quantum effect to realize ultrafast devices and devices with new functions.

[0003] In such an environment, attempts are being made to perform high-capacity communication, information processing, imaging, measurement, etc., by utilizing electromagnetic waves in a frequency region called the terahertz band, which has a frequency of 0.1 THz to 10 THz, as shown in Patent Document 1, for example. Electromagnetic waves in this frequency region have the properties of both light and radio waves, and if devices operating in this frequency region are realized, they could be used for many applications, including the above-mentioned imaging, high-capacity communication, and information processing, as well as measurements in various fields such as physical property analysis, astronomy, and biology.

[0004] Japanese Patent Application Laid-Open No. 2020-115500

[0005] [Summary] In a system using a terahertz element for oscillation and a terahertz element for detection, if these terahertz elements are arranged in an array, the area for arranging the terahertz elements becomes large.

[0006] A terahertz system according to one aspect of the present disclosure includes a plurality of first terahertz elements that oscillate and detect terahertz waves, a plurality of second terahertz elements that oscillate and detect terahertz waves, and a control device configured to switch between a first state in which the plurality of first terahertz elements oscillate terahertz waves and the plurality of second terahertz elements detect the terahertz waves, and a second state in which the plurality of second terahertz elements oscillate terahertz waves and the first terahertz elements detect the terahertz waves.

[0007] FIG. 1 is a schematic diagram of an exemplary terahertz system according to a first embodiment. FIG. 2 is a schematic plan view of a terahertz device in the terahertz system of FIG. 1. FIG. 3 is a block diagram showing an outline of the electrical configuration of the terahertz system of FIG. 1. FIG. 4 is a block diagram showing an outline of the electrical configuration of a power supply control circuit and its periphery in a control device of the terahertz system of FIG. 3. FIG. 5 is a schematic plan view of the first terahertz element of FIG. 2. FIG. 6 is a schematic plan view enlarging a region F6 in the first terahertz element of FIG. 5. FIG. 7 is a schematic cross-sectional view of the first terahertz element taken along line F7-F7 in FIG. 6. FIG. 8 is a schematic cross-sectional view enlarging an active element and its periphery in the first terahertz element of FIG. 7. FIG. 9 is a graph showing the relationship between the forward voltage and forward current of the first terahertz element. FIG. 10 is a graph showing the transition of the oscillation and detection operations of a plurality of first terahertz elements and a plurality of second terahertz elements. FIG. 11 is a schematic plan view of the terahertz device in a first state. FIG. 12 is a schematic plan view of a terahertz device in a second state. FIG. 13 is a schematic plan view of a terahertz device in an exemplary terahertz system according to a second embodiment. FIG. 14 is a graph showing progress of oscillation and detection operations of a plurality of first to fourth terahertz elements. FIG. 15 is a schematic plan view of a terahertz device in a first state. FIG. 16 is a schematic plan view of a terahertz device in a second state. FIG. 17 is a schematic plan view of a terahertz device in a third state. FIG. 18 is a schematic plan view of a terahertz device in a fourth state. FIG. 19 is a schematic plan view of a terahertz device in an exemplary terahertz system according to a third embodiment. FIG. 20 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. FIG. 21 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. FIG. 22 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. FIG. 23 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. 24 and 25 are schematic plan views of a terahertz device in a terahertz system according to a modified example.Fig. 26 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. Fig. 27 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. Fig. 28 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. Fig. 29 is a graph showing progress of oscillation operation and detection operation of a first terahertz element in a terahertz system according to a modified example. Fig. 30 is a schematic plan view of a terahertz system according to a modified example. Fig. 31 is a schematic plan view of a terahertz device in the terahertz system of Fig. 30. Fig. 32 is a schematic plan view of a terahertz device in the terahertz system of Fig. 30. Fig. 33 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. Fig. 34 is a schematic plan view of a terahertz device in a terahertz system according to a modified example. Fig. 35 is a schematic plan view of a terahertz device in a terahertz system according to a modified example.

[0008] DETAILED DESCRIPTION Several embodiments of the terahertz system of the present disclosure will now be described with reference to the accompanying drawings. Note that for simplicity and clarity of description, components shown in the drawings are not necessarily drawn to scale. Also, cross-sectional views may omit hatching lines for ease of understanding. The accompanying drawings merely illustrate embodiments of the present disclosure and should not be considered as limiting the present disclosure.

[0009] The following detailed description includes devices, systems, and methods embodying exemplary embodiments of the present disclosure. This detailed description is merely illustrative in nature and is not intended to limit the embodiments of the present disclosure or the application and uses of such embodiments.

[0010] The terms "first," "second," "third," etc. used in this disclosure are merely used to label and are not necessarily intended to assign any order to their objects. The phrase "at least one" used in this disclosure means "one or more" of the desired options. As an example, the phrase "at least one" used in this disclosure means "only one option" or "both of two options" if the number of options is two. As another example, the phrase "at least one" used in this disclosure means "only one option" or "any combination of two or more options" if the number of options is three or more.

[0011] First Embodiment Overall Configuration of Terahertz System The overall configuration of a terahertz system 10 will be described with reference to Fig. 1. Fig. 1 schematically shows the general configuration of a reflective terahertz system.

[0012] 1 , a terahertz system 10 according to the first embodiment is used to capture an image of a detection target 100. The terahertz system 10 includes a terahertz device 20 that generates and detects terahertz waves W, and a control device 30 that controls the terahertz device 20. Here, the terahertz waves W are electromagnetic waves in a frequency range of 0.1 THz or more and 10 THz or less.

[0013] 1 , terahertz device 20 is disposed facing detection object 100. Terahertz device 20 includes a plurality of first terahertz elements 21 that oscillate and detect terahertz waves W, and a plurality of second terahertz elements 22 that oscillate and detect terahertz waves W. In terahertz device 20, one of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 radiates terahertz waves W toward detection object 100. In terahertz device 20, the other of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 detects terahertz waves W radiated toward detection object 100 and reflected by detection object 100. In this way, terahertz device 20 is a device in which an oscillator that oscillates terahertz waves W and a detector that detects terahertz waves W are integrally provided.

[0014] The control device 30 is electrically connected to the terahertz device 20. The control device 30 is configured to control the oscillation and detection of terahertz waves W of the terahertz device 20. The control device 30 controls the multiple first terahertz elements 21 and the multiple second terahertz elements 22 so that the multiple first terahertz elements 21 oscillate and the multiple second terahertz elements 22 detect. The control device 30 controls the multiple first terahertz elements 21 and the multiple second terahertz elements 22 so that the multiple second terahertz elements 22 oscillate and the multiple first terahertz elements 21 detect.

[0015] The control device 30 receives, for example, imaging information relating to the terahertz waves W detected from the terahertz device 20. The control device 30 is configured to generate a digital image of the detection target 100, which has been imaged based on the imaging information, for example.

[0016] [Configuration of Terahertz Device] The configuration of the terahertz device 20 will be described with reference to Fig. 2. Fig. 2 schematically shows the planar structure of the terahertz device 20.

[0017] As shown in FIG. 2 , the terahertz device 20 includes a substrate 25 whose thickness direction is the Z direction. The substrate 25 may be made of a material containing, for example, silicon (Si). In one example, a Si substrate may be used as the substrate 25. The substrate 25 may be doped with, for example, iron (Fe). Here, two mutually orthogonal directions among directions orthogonal to the Z direction are referred to as the "X direction" and the "Y direction." Viewing the terahertz device 20 from the Z direction is referred to as a "planar view." Here, the X direction is an example of a "first direction," and the Y direction is an example of a "second direction."

[0018] 2 , the substrate 25 has a rectangular shape with its long side in the X direction and its short side in the Y direction in plan view. Both the dimensions of the substrate 25 in the X direction and the Y direction are greater than its thickness (dimension in the Z direction). The substrate 25 includes a first substrate surface 25S. Each of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 is mounted on the first substrate surface 25S. The shape and size of the substrate 25 in plan view can be changed as appropriate depending on the number and arrangement of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22.

[0019] In the first embodiment, the multiple first terahertz elements 21 are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. It can also be said that the multiple first terahertz elements 21 are arranged side by side in the X direction. In the first embodiment, four first terahertz elements 21 are arranged along the X direction. Hereinafter, for convenience, the four first terahertz elements 21 may be referred to as "first terahertz elements 21A to 21D."

[0020] In the first embodiment, the multiple second terahertz elements 22 are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. The multiple second terahertz elements 22 can also be said to be arranged side by side in the X direction. In the first embodiment, four second terahertz elements 22 are arranged along the X direction. That is, in the first embodiment, the number of the multiple first terahertz elements 21 and the number of the multiple second terahertz elements 22 are equal to each other. Hereinafter, for convenience, the four second terahertz elements 22 may be referred to as "second terahertz elements 22A to 22D."

[0021] The plurality of second terahertz elements 22 are arranged spaced apart from the plurality of first terahertz elements 21 in the Y direction. It can also be said that the plurality of second terahertz elements 22 are arranged side by side with the plurality of first terahertz elements 21 in the Y direction. When viewed from the Y direction, the plurality of second terahertz elements 22 are arranged at positions overlapping the plurality of first terahertz elements 21. In the first embodiment, the second terahertz element 22A is arranged at a position overlapping with the first terahertz element 21A when viewed from the Y direction. The second terahertz element 22B is arranged at a position overlapping with the first terahertz element 21B when viewed from the Y direction. The second terahertz element 22C is arranged at a position overlapping with the first terahertz element 21C when viewed from the Y direction. The second terahertz element 22D is arranged at a position overlapping with the first terahertz element 21D when viewed from the Y direction.

[0022] In this way, the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are arranged in a matrix in a planar view. With the X direction as rows and the Y direction as columns, it can be said that the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are arranged in rows. It can also be said that the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are arranged in an array in a planar view. Note that the detailed configurations of the first terahertz elements 21 and the second terahertz elements 22 will be described later with reference to FIGS. 5 to 8 .

[0023] [Configuration of Control Device] The configuration of the control device 30 will be described with reference to Fig. 3 and Fig. 4. Fig. 3 shows a schematic circuit configuration of the terahertz system 10 including the control device 30. Fig. 4 shows a schematic circuit configuration of the control device 30.

[0024] As shown in FIG. 3, the control device 30 includes a power supply control circuit 31, an oscillation signal generation circuit 32, a detection signal generation circuit 33, a signal processing circuit , a selection circuit 35, and a timing generation circuit .

[0025] The oscillation signal generation circuit 32 is electrically connected to the power supply control circuit 31. The oscillation signal generation circuit 32 is configured to generate an oscillation drive signal S1 that causes the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 to oscillate terahertz waves W. The oscillation drive signal S1 is, for example, an AC signal in which a modulation signal of a predetermined modulation frequency is superimposed on an oscillation bias voltage VB1.

[0026] As shown in FIG. 4 , the oscillation signal generating circuit 32 includes a modulation circuit 32A, an oscillation bias circuit 32B, and a superposition circuit 32C. The modulation circuit 32A is configured to generate a modulation signal with a predetermined modulation frequency. The modulation signal may be an AC signal. The modulation signal may be, for example, a rectangular wave (square wave). The modulation signal may also be a sine wave, a triangular wave, or the like. The modulation frequency may be lower than the oscillation frequencies of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. The modulation frequency may be 1 MHz, for example. The amplitude of the modulation signal may be 200 mV, for example.

[0027] The oscillation bias circuit 32B is configured to generate an oscillation bias voltage VB1 for the first terahertz element 21 and the second terahertz element 22. The oscillation bias voltage VB1 may be, for example, a DC voltage. For example, the oscillation bias voltage VB1 may be 280 mV.

[0028] The superimposing circuit 32C is configured to generate an oscillation drive signal S1 by superimposing a modulation signal on the oscillation bias voltage VB1. The superimposing circuit 32C is configured to output the oscillation drive signal S1 to the power supply control circuit 31.

[0029] The detection signal generation circuit 33 is electrically connected to the power supply control circuit 31. The detection signal generation circuit 33 is configured to generate a detection drive signal S2 that causes the multiple first terahertz elements 21 and the multiple second terahertz elements 22 to detect the terahertz waves W. The detection signal generation circuit 33 includes a detection bias circuit 33A that is configured to generate a detection bias voltage VB2. The detection bias voltage VB2 may be, for example, a DC voltage. In one example, the detection bias voltage VB2 may be a voltage different from the oscillation bias voltage VB1. The detection drive signal S2 is, for example, a DC signal of the detection bias voltage VB2.

[0030] The power supply control circuit 31 is configured to output an oscillation drive signal S1 and a detection drive signal S2 to the terahertz device 20. The power supply control circuit 31 is configured to alternately apply the oscillation drive signal S1 and the detection drive signal S2 to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. Therefore, the terahertz device 20 alternately switches between a first state in which the plurality of first terahertz elements 21 oscillate terahertz waves W and the plurality of second terahertz elements 22 detect the terahertz waves W, and a second state in which the plurality of second terahertz elements 22 oscillate terahertz waves W and the plurality of first terahertz elements 21 detect the terahertz waves W. In this way, the control device 30 is configured to switch between the first state and the second state.

[0031] As shown in FIG. 4, the power supply control circuit 31 includes a noise reduction circuit 31A and a current amplification circuit 31B used to output the oscillation drive signal S1, a current amplification circuit 31C and a noise reduction circuit 31D used to output the detection drive signal S2, and an analog switch 31E that switches the output destination of the oscillation drive signal S1 and the detection drive signal S2.

[0032] The noise reduction circuit 31A is electrically connected to the oscillation signal generation circuit 32. More specifically, the noise reduction circuit 31A is electrically connected to the superimposing circuit 32C in the oscillation signal generation circuit 32. The noise reduction circuit 31A may include, for example, a low-pass filter circuit. For example, the noise reduction circuit 31A may be configured to cut frequencies higher than the modulation frequency and pass frequencies equal to or lower than the modulation frequency. Here, the cutoff frequency of the low-pass filter may be, for example, 10 MHz.

[0033] The current amplifier circuit 31B is electrically connected to the noise reduction circuit 31A and the analog switch 31E. The current amplifier circuit 31B amplifies the current supplied to the terahertz device 20. The current amplifier circuit 31B includes an operational amplifier (not shown). The operational amplifier of the current amplifier circuit 31B may be configured as a buffer circuit.

[0034] The oscillation drive signal S1 output from the oscillation signal generating circuit 32 to the power supply control circuit 31 has noise removed in the noise reduction circuit 31A, and then the current supplied to the terahertz device 20 is amplified by the current amplification circuit 31B and input to the analog switch 31E.

[0035] The current amplifier circuit 31C is electrically connected to the detection signal generating circuit 33. The current amplifier circuit 31C includes an operational amplifier (not shown). This operational amplifier may be configured as a buffer circuit. In this manner, the current amplifier circuit 31C may have the same configuration as, for example, the current amplifier circuit 31B.

[0036] The noise reduction circuit 31D is electrically connected to the current amplifier circuit 31C and the analog switch 31E. The noise reduction circuit 31D may include, for example, a direct current (DC) filter circuit. That is, the noise reduction circuit 31D is configured to block alternating current (AC) components while passing DC components.

[0037] The detection drive signal S2 output from the detection signal generation circuit 33 to the power supply control circuit 31 is amplified in the current amplification circuit 31C so that the current to be supplied to the terahertz device 20 is amplified, and then input to the analog switch 31E as a DC voltage from which the AC component (noise) has been blocked in the noise reduction circuit 31D.

[0038] The analog switch 31E is electrically connected to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 (see FIG. 3 ). The analog switch 31E is configured to be switchable between a first connection state and a second connection state. The first connection state is a connection state in which the plurality of first terahertz elements 21 are electrically connected to the oscillation signal generation circuit 32, and the plurality of second terahertz elements 22 are electrically connected to the detection signal generation circuit 33. The second connection state is a connection state in which the plurality of first terahertz elements 21 are electrically connected to the detection signal generation circuit 33, and the plurality of second terahertz elements 22 are electrically connected to the oscillation signal generation circuit 32. When the analog switch 31E is in the first connection state, an oscillation drive signal S1 is applied to each of the plurality of first terahertz elements 21, and a detection drive signal S2 is applied to each of the plurality of second terahertz elements 22. As a result, the terahertz device 20 enters a first state in which the plurality of first terahertz elements 21 oscillate terahertz waves W and the plurality of second terahertz elements 22 detect the terahertz waves W. When the analog switch 31E is in the second connection state, the detection drive signal S2 is applied to each of the plurality of first terahertz elements 21 and the oscillation drive signal S1 is applied to each of the plurality of second terahertz elements 22. As a result, the terahertz device 20 enters a second state in which the plurality of second terahertz elements 22 oscillate terahertz waves W and the plurality of first terahertz elements 21 detect the terahertz waves W. In this way, as the connection state of the analog switch 31E is switched between the first connection state and the second connection state, the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are switched between the first state and the second state.

[0039] 3 , the signal processing circuit 34 is electrically connected to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 individually through the selection circuit 35. The signal processing circuit 34 is configured to process the outputs from the first terahertz elements 21 and the second terahertz elements 22. More specifically, the signal processing circuit 34 is configured to convert frequency information of the first detection signals SR1 detected by the plurality of first terahertz elements 21 into information corresponding to the terahertz waves W of the first terahertz elements 21. The signal processing circuit 34 is configured to convert frequency information of the second detection signals SR2 detected by the plurality of second terahertz elements 22 into information corresponding to the terahertz waves W of the second terahertz elements 22. The first detection signals SR1 include information related to the terahertz waves W detected by the first terahertz elements 21. The second detection signals SR2 include information related to the terahertz waves W detected by the second terahertz elements 22. The information relating to the terahertz waves W includes frequency information of the terahertz waves W, amplitude information of the terahertz waves W, intensity information of the terahertz waves W, and the like.

[0040] The signal processing circuit 34 includes a sample and hold circuit 34A, a noise reduction circuit 34B, a signal amplification circuit 34C, and an analog-to-digital conversion circuit 34D. The sample and hold circuit 34A is electrically connected to the selection circuit 35 and the noise reduction circuit 34B. A voltage based on the output current from each of the first terahertz elements 21 and each of the second terahertz elements 22 is input to the sample and hold circuit 34A through the selection circuit 35. The sample and hold circuit 34A is configured to sample the voltage from each of the first terahertz elements 21 and each of the second terahertz elements 22 and hold the voltage for a predetermined period. The sample and hold circuit 34A is configured to output the voltage held for the predetermined period to the noise reduction circuit 34B.

[0041] The noise reduction circuit 34B is electrically connected to the signal amplification circuit 34C. The noise reduction circuit 34B may include, for example, a filter. The noise reduction circuit 34B is configured to remove noise from the analog signal from the sample-and-hold circuit 34A before outputting the signal to the signal amplification circuit 34C.

[0042] The signal amplifier circuit 34C is electrically connected to the analog-to-digital conversion circuit 34D. The signal amplifier circuit 34C includes a differential amplifier (not shown). The signal amplifier circuit 34C is configured to amplify the analog signal from the noise reduction circuit 34B and then output the amplified signal to the analog-to-digital conversion circuit 34D.

[0043] The analog-to-digital conversion circuit 34D is configured to convert the analog signal input from the signal amplification circuit 34C into a digital signal. The analog-to-digital conversion circuit 34D may be, for example, a SAR (Successive Approximation Register) ADC (Analog-Digital Converter). In this way, the signal processing circuit 34 is configured to process the analog signals (first detection signals SR1 and second detection signals SR2) output from the multiple first terahertz elements 21 and the multiple second terahertz elements 22 into digital signals.

[0044] The selection circuit 35 is electrically connected to each of the first terahertz elements 21 and the second terahertz elements 22. The selection circuit 35 is electrically connected to the signal processing circuit 34. The selection circuit 35 is configured to selectively output the first detection signals SR1 of the first terahertz elements 21 and the second detection signals SR2 of the second terahertz elements 22 to the signal processing circuit 34.

[0045] The selection circuit 35 includes analog switches 35A electrically connected to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. In one example, a plurality of analog switches 35A are provided, the number of which corresponds to the number of first terahertz elements 21 and the number of second terahertz elements 22. In the first embodiment, the selection circuit 35 includes four analog switches 35A. For convenience, the four analog switches 35A will be referred to below as "analog switch 35AA," "analog switch 35AB," "analog switch 35AC," and "analog switch 35AD." The analog switch 35AA is electrically connected to both the first terahertz element 21A and the second terahertz element 22A. The analog switch 35AB is electrically connected to both the first terahertz element 21B and the second terahertz element 22B. The analog switch 35AC is electrically connected to both the first terahertz element 21C and the second terahertz element 22C. The analog switch 35AD is electrically connected to both the first terahertz element 21D and the second terahertz element 22D. In this way, a plurality of analog switches 35A are provided corresponding to the number of combinations of the first terahertz element 21 and the second terahertz element 22. Each of the analog switches 35AA to 35AD is electrically connected to the signal processing circuit 34.

[0046] The timing generation circuit 36 ​​is electrically connected to both the power supply control circuit 31 and the selection circuit 35. The timing generation circuit 36 ​​is electrically connected to the analog switch 31E (see FIG. 3) of the power supply control circuit 31. In the first embodiment, the timing generation circuit 36 ​​is electrically connected individually to the analog switches 35AA to 35AD of the selection circuit 35. That is, the timing generation circuit 36 ​​is configured to individually control the analog switches 35AA to 35AD. Therefore, it can be said that the control device 30 is configured to individually control the multiple analog switches 35A. The timing generation circuit 36 ​​is configured to control the power supply control circuit 31 and the selection circuit 35. The timing generation circuit 36 ​​is a circuit that controls the timing of switching between a first state and a second state as oscillation and detection states of the multiple first terahertz elements 21 and the multiple second terahertz elements 22.

[0047] The timing generation circuit 36 ​​includes, for example, a clock signal generation circuit and a counter that counts the clock signal. The timing generation circuit 36 ​​is configured to generate a timing generation signal based on the count of the counter. The timing generation signal includes a first timing signal CS1 and a second timing signal CS2. The timing generation circuit 36 ​​may be configured to generate the timing generation signal using a clock signal having a frequency (e.g., 1 kHz) that corresponds to the timing at which the first state and the second state are switched.

[0048] The timing generation circuit 36 ​​is configured to switch between the first state and the second state at predetermined intervals. A specific example is described below. For example, in the first state, the timing generation circuit 36 ​​is configured to output a first timing signal CS1 to the analog switch 31E and the analog switches 35AA-35AD when the count value reaches a switching count value from the start of counting. This switches the analog switch 31E from the first connection state to the second connection state. As a result, the oscillation and detection states of the multiple first terahertz elements 21 and the multiple second terahertz elements 22 are switched from the first state to the second state. More specifically, the multiple first terahertz elements 21 are electrically connected to the detection signal generation circuit 33, and the multiple second terahertz elements 22 are electrically connected to the oscillation signal generation circuit 32. The analog switches 35AA-35AD electrically connect the multiple first terahertz elements 21A-21D to the signal processing circuit 34. As a result, the first detection signals SR1 of the plurality of first terahertz elements 21A to 21D are input to the signal processing circuit 34. The timing generation circuit 36 ​​is configured to control the plurality of analog switches 35AA to 35AD of the selection circuit 35 so as to sequentially output the first detection signals SR1 of the plurality of first terahertz elements 21 to the signal processing circuit 34.

[0049] The timing generation circuit 36 ​​is configured to output a second timing signal CS2 to the analog switch 31E and the analog switches 35AA-35AD when, for example, the count value reaches the switching count value from the start of counting in the second state. This switches the analog switch 31E from the second connection state to the first connection state. As a result, the oscillation and detection states of the multiple first terahertz elements 21 and the multiple second terahertz elements 22 are switched from the second state to the first state. More specifically, the multiple first terahertz elements 21 are electrically connected to the oscillation signal generation circuit 32, and the multiple second terahertz elements 22 are electrically connected to the detection signal generation circuit 33. The analog switches 35AA-35AD electrically connect the multiple second terahertz elements 22A-22D to the signal processing circuit 34. This causes the second detection signals SR2 of the multiple second terahertz elements 22A-22D to be input to the signal processing circuit 34. The timing generation circuit 36 ​​is configured to control the multiple analog switches 35AA to 35AD of the selection circuit 35 so as to sequentially output the second detection signals SR2 of the multiple second terahertz elements 22 to the signal processing circuit 34.

[0050] Here, the switching count value is a count corresponding to a predetermined period, such as a first period T1 and a second period T2 (both of which are described later and are shown in FIG. 10 ). The timing generation circuit 36 ​​is configured to reset the count when the count value reaches the switching count value from the start of counting. Here, the predetermined period (first period T1 and second period T2) is longer than the period of the modulation signal of the modulation circuit 32A. In one example, the predetermined period (first period T1 and second period T2) is longer than the time required for the signal processing circuit 34 to process the first detection signal SR1 or the second detection signal SR2.

[0051] [Configuration of Terahertz Elements] The configurations of the first terahertz element 21 and the second terahertz element 22 will be described with reference to FIGS. 5 to 8. FIG. 5 schematically shows the general planar structure of one first terahertz element 21. FIG. 6 schematically shows an enlarged structure of region F6 in FIG. 5. FIG. 7 schematically shows a cross-sectional structure of the first terahertz element 21 taken along line F7-F7 in FIG. 6. FIG. 8 schematically shows an enlarged cross-sectional structure of the active element 42 and its periphery in FIG. 7. Note that an insulating layer 45, which will be described later, is omitted from FIGS. 5, 6, and 8.

[0052] In the first embodiment, the first terahertz element 21 and the second terahertz element 22 have the same configuration. Therefore, in the following, the detailed configuration of the first terahertz element 21 will be described, and a description of the configuration of the second terahertz element 22 (see FIG. 2 ) will be omitted.

[0053] As shown in FIG. 5 , the first terahertz element 21 includes a semiconductor substrate 41, an active element 42, a first electrode 43, a second electrode 44, and an insulating layer 45 (see FIG. 7 ). The semiconductor substrate 41 is a semi-insulating substrate made of a semiconductor material. The semiconductor substrate 41 may be made of a material containing indium phosphide (InP), for example. The semiconductor substrate 41 has a flat plate shape with its thickness direction aligned in the Z direction. The semiconductor substrate 41 has a rectangular shape in plan view. Although not shown, a back reflector metal layer may be provided on a second substrate surface of the semiconductor substrate 41 opposite the first substrate surface 41S.

[0054] The active element 42 may be provided on the semiconductor substrate 41. The active element 42 is electrically connected to both the first electrode 43 and the second electrode 44. The active element 42 may typically be a resonant tunneling diode (RTD). That is, the first terahertz element 21 may include an RTD. The active element 42 may also be configured by a diode, a transistor, or the like other than the RTD. Such diodes and transistors may be, for example, TUNNETT (Tunnel Transit Time) diodes, IMPATT (Impact Ionization Avalanche Transit Time) diodes, gallium arsenide (GaAs)-based field effect transistors, gallium nitride (GaN)-based field effect transistors, high electron mobility transistors (HEMTs), heterojunction bipolar transistors (HBTs), complementary metal-oxide-semiconductor (CMOS) FETs, or Schottky barrier diodes.

[0055] As shown in FIG. 7 , the active element 42 includes a structure in which multiple semiconductor layers are stacked. More specifically, as shown in FIG. 8 , an indium gallium arsenide layer (hereinafter referred to as an “InGaAs layer”) 51A is disposed on a semiconductor substrate 41. The InGaAs layer 51A is heavily doped with n-type impurities. An InGaAs layer 52A is disposed on the InGaAs layer 51A. The InGaAs layer 52A is doped with n-type impurities. An InGaAs layer 53A is disposed on the InGaAs layer 52A. The InGaAs layer 53A is not doped with impurities. An aluminum arsenide layer (hereinafter referred to as an “AlAs layer”) 54A is disposed on the InGaAs layer 53A. An InGaAs layer 55 is disposed on the AlAs layer 54A. An AlAs layer 54B is disposed on the InGaAs layer 55. An InGaAs layer 53B is disposed on the AlAs layer 54B. The InGaAs layer 53B is not doped with impurities. An InGaAs layer 52B is disposed on the InGaAs layer 53B. An InGaAs layer 51B is disposed on the InGaAs layer 52B. The InGaAs layer 51B is doped with a high concentration of n-type impurities. A second electrode 44 is disposed on the InGaAs layer 51B.

[0056] The AlAs layer 54A, the InGaAs layer 55, and the AlAs layer 54B constitute the RTD portion of the active element 42. The InGaAs layer 55 is a quantum well layer, and the AlAs layers 54A and 54B are each a tunnel barrier layer. The InGaAs layer 55 may be thicker than the AlAs layers 54A and 54B. The indium content in the InGaAs layer 55 may be greater than the indium content in the other indium-containing layers (InGaAs layers 51A to 53A, 51B to 53B).

[0057] 5 and 7 , the first electrode 43 and the second electrode 44 may constitute terminals of the first terahertz element 21. The first electrode 43 and the second electrode 44 serve as output terminals in the first state and as input terminals in the second state. In this way, the first electrode 43 and the second electrode 44 are an example of a "first terminal."

[0058] Since the second terahertz element 22 has the same configuration as the first terahertz element 21, the first electrode and the second electrode of the second terahertz element 22 serve as an input terminal in the first state and as an output terminal in the second state. In this way, the first electrode and the second electrode of the second terahertz element 22 are an example of a "second terminal."

[0059] 8, the first electrode 43 is disposed on the semiconductor substrate 41, with a portion thereof disposed on the InGaAs layer 51A. The second electrode 44 is disposed on the semiconductor substrate 41, with a portion thereof disposed on the InGaAs layer 51B. The second electrode 44 is disposed spaced apart from the InGaAs layer 51A. An insulating layer 45 is interposed between the second electrode 44 and the InGaAs layer 51A. The first electrode 43 and the second electrode 44 are disposed spaced apart from each other.

[0060] Both the first electrode 43 and the second electrode 44 may be configured with a stacked structure of metal layers. The first electrode 43 and the second electrode 44 may be a stacked structure of gold (Au), palladium (Pd), and titanium (Ti), for example. In another example, the first electrode 43 and the second electrode 44 may be a stacked structure of gold and titanium, for example.

[0061] As shown in FIG. 6 , the first electrode 43 includes an antenna portion 43A, a feeder portion 43B, and a pad electrode portion 43C. The second electrode 44 includes an antenna portion 44A, a feeder portion 44B, and a pad electrode portion 44C. As such, the antenna structure formed by the antenna portions 43A and 44A is integrated in the first terahertz element 21. In the example shown in FIG. 6 , the antenna portions 43A and 44A form a dipole antenna. Note that the antenna structure formed by the antenna portions 43A and 44A is not limited to a dipole antenna, and may be a slot antenna, a bowtie antenna, a ring antenna, or the like. The feeder portion 43B connects the antenna portion 43A and the pad electrode portion 43C. The feeder portion 44B connects the antenna portion 44A and the pad electrode portion 44C. The pad electrode portions 43C and 44C form terminals.

[0062] As shown in FIG. 7, the insulating layer 45 is, for example, a silicon oxide film (SiO ２ ), silicon nitride film (SiN), silicon oxynitride film (SiON), hafnium oxide film (HfO ２ ), and aluminum oxide film (Al ２ O ３ ) The insulating layer 45 may be a single-layer film or a multi-layer film. The insulating layer 45 may cover the active element 42. The insulating layer 45 is interposed between the InGaAs layer 51A and the second electrode 44, thereby insulating the InGaAs layer 51A from the second electrode 44.

[0063] [Oscillation and Detection Operations of Terahertz Elements] The oscillation and detection operations of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 will be described with reference to FIGS. 9 to 12. FIG. 9 shows the current-voltage characteristics of the first terahertz elements 21 and the plurality of second terahertz elements 22. FIG. 10 shows the transition of the oscillation drive signal S1 applied to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. FIG. 11 schematically shows the planar structure of the terahertz device 20 when the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are in a first state. FIG. 12 schematically shows the planar structure of the terahertz device 20 when the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are in a second state.

[0064] As shown in Fig. 9, the current-voltage characteristics of the first terahertz element 21 and the second terahertz element 22 (see Fig. 2) including the RTD include a negative resistance region RX in which the forward current IF decreases as the forward voltage VF increases. The first terahertz element 21 and the second terahertz element 22 oscillate in the negative resistance region RX. In other words, the negative resistance region RX can also be said to be the oscillation region R1 of the first terahertz element 21 and the second terahertz element 22. Therefore, when the oscillation drive voltage V1 of the oscillation drive signal S1 is applied to the first terahertz element 21 and the second terahertz element 22 so that the oscillation drive voltage V1 is within the oscillation region R1, the first terahertz element 21 and the second terahertz element 22 oscillate.

[0065] Furthermore, in the current-voltage characteristics of the first terahertz element 21 and the second terahertz element 22, a detection region R2 is set adjacent to the oscillation region R1 on the lower voltage side. The detection region R2 is a region where the forward voltage VF is lower than the negative resistance region RX, and therefore is a region where the first terahertz element 21 and the second terahertz element 22 do not oscillate. Therefore, when the detection drive voltage V2 of the detection drive signal S2 is applied to the first terahertz element 21 and the second terahertz element 22, the first terahertz element 21 and the second terahertz element 22 can detect the terahertz wave W. The detection drive voltage V2 may be set according to the sensitivity characteristics of the first terahertz element 21 and the second terahertz element 22. Here, the detection drive voltage V2 may be the same as the detection bias voltage VB2. Furthermore, the oscillation drive signal S1 may be generated so that the drive voltage VG when the oscillation drive signal S1 is off is within the detection region R2. The drive voltage VG can be changed arbitrarily.

[0066] As shown in FIGS. 9 and 10, when the pulsed oscillation drive signal S1 is applied to the second terahertz element 22, the second terahertz element 22 operates so as to alternately repeat an oscillation state and an oscillation-stop state.

[0067] The oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are switched between a first state and a second state at predetermined intervals by the timing generation circuit 36 ​​in Fig. 3 and the analog switch 31E of the power supply control circuit 31 in Fig. 4. Specifically, as shown in Fig. 10, the first state is set during a first period T1 from time (2n-1)T to time 2nT, and the second state is set during a second period T2 from time 2nT to time (2n+1)T. In other words, at time 2nT, the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are switched from the first state to the second state.

[0068] During the first period T1, a pulsed oscillation drive signal S1 is applied to the multiple first terahertz elements 21. Each first terahertz element 21 operates by alternately switching between an oscillation state and an oscillation-stopped state in response to the applied oscillation drive signal S1. Although not shown, during the first period T1, a detection drive signal S2 as a DC voltage is applied to the multiple second terahertz elements 22. Each second terahertz element 22 maintains a state capable of detecting terahertz waves W throughout the first period T1 due to the applied detection drive signal S2. As shown in FIG. 11 , the multiple first terahertz elements 21 are in an oscillation state, and the multiple second terahertz elements 22 are in a non-oscillation state (detection state). Therefore, the multiple first terahertz elements 21 emit terahertz waves W toward the detection object 100 (see FIG. 1 ). The multiple second terahertz elements 22 then detect the terahertz waves W reflected from the detection object 100.

[0069] As shown in FIG. 10 , during the second period T2, an oscillation drive signal S1 is applied to the plurality of second terahertz elements 22. Each second terahertz element 22 operates by alternately switching between an oscillation state and an oscillation-stopped state in response to the applied oscillation drive signal S1. Although not shown, during the second period T2, a detection drive signal S2 is applied to the plurality of first terahertz elements 21. Each first terahertz element 21 maintains a state capable of detecting terahertz waves W throughout the second period T2 due to the applied detection drive signal S2. As a result, as shown in FIG. 12 , the plurality of first terahertz elements 21 enter a non-oscillation state (detection state), and the plurality of second terahertz elements 22 enter an oscillation state. Therefore, the plurality of second terahertz elements 22 emit terahertz waves W toward the detection object 100 (see FIG. 1 ). The plurality of first terahertz elements 21 then detect the terahertz waves W reflected from the detection object 100.

[0070] 11 are set to periods sufficiently longer than the period of the modulation frequency. For example, when the modulation frequency is 1 MHz, both the first period T1 and the second period T2 may be set to 1 msec. As a result, during the first period T1, a plurality of pulse-shaped oscillation drive signals S1 are applied to the first terahertz element 21. During the second period T2, a plurality of pulse-shaped oscillation drive signals S1 are applied to the second terahertz element 22.

[0071] [Operation of First Embodiment] The operation of the terahertz system 10 of the first embodiment will be described. In the terahertz device 20, the multiple first terahertz elements 21 are configured to oscillate terahertz waves W in a first state and detect terahertz waves W in a second state. The multiple second terahertz elements 22 are configured to detect terahertz waves W in the first state and oscillate terahertz waves W in the second state. In this manner, each of the first terahertz elements 21 and each of the second terahertz elements 22 has the function of both oscillating terahertz waves W and detecting terahertz waves W. Therefore, compared to the case where a terahertz element for oscillation and a terahertz element for detection are provided, the number of terahertz elements is reduced, and therefore the area for arranging the terahertz elements can be made smaller.

[0072] Effects of First Embodiment The terahertz system 10 of the first embodiment provides the following effects: (1-1) The terahertz system 10 includes a plurality of first terahertz elements 21 that oscillate and detect terahertz waves W, a plurality of second terahertz elements 22 that oscillate and detect terahertz waves W, and a control device 30 that is configured to switch between a first state in which the plurality of first terahertz elements 21 oscillate the terahertz waves W and the plurality of second terahertz elements 22 detect the terahertz waves W, and a second state in which the plurality of second terahertz elements 22 oscillate the terahertz waves W and the first terahertz elements 21 detect the terahertz waves W.

[0073] According to this configuration, each of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 serves as both an oscillation terahertz element and a detection terahertz element, so that the area for arranging the terahertz elements can be made small.

[0074] In addition, the control device 30 switches the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 between the first state and the second state, thereby making it possible to acquire information detected by the plurality of first terahertz elements 21 and information detected by the plurality of second terahertz elements 22. Therefore, it is possible to suppress a decrease in detection accuracy in the terahertz system 10.

[0075] (1-2) The control device 30 includes a power supply control circuit 31 configured to output an oscillation drive signal S1 that operates the device to oscillate terahertz waves W, and a detection drive signal S2 that operates the device to detect terahertz waves W. The power supply control circuit 31 is configured to alternately apply the oscillation drive signal S1 and the detection drive signal S2 to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22.

[0076] According to this configuration, the power supply control circuit 31 enters the first state by applying the oscillation drive signal S1 to the plurality of first terahertz elements 21 and the detection drive signal S2 to the plurality of second terahertz elements 22, and enters the second state by applying the detection drive signal S2 to the plurality of first terahertz elements 21 and the oscillation drive signal S1 to the plurality of second terahertz elements 22. The power supply control circuit 31 can switch between the first state and the second state by alternately applying the oscillation drive signal S1 and the detection drive signal S2 to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22.

[0077] (1-3) The control device 30 includes an oscillation signal generation circuit 32 configured to generate an oscillation drive signal S1. The oscillation signal generation circuit 32 includes an oscillation bias circuit 32B configured to generate a DC oscillation bias voltage VB1, a modulation circuit 32A configured to generate a modulation signal at a modulation frequency, and a superposition circuit 32C that generates the oscillation drive signal S1 by superimposing the modulation signal on the oscillation bias voltage VB1. With this configuration, when the terahertz element detects terahertz waves W, the signal intensity at the modulation frequency increases, making it possible to suitably acquire information about the terahertz waves W.

[0078] (1-4) The control device 30 includes a detection signal generation circuit 33 configured to generate a detection drive signal S2. The detection signal generation circuit 33 includes a detection bias circuit 33A configured to generate a DC detection bias voltage VB2. The oscillation bias voltage VB1 and the detection bias voltage VB2 are different from each other.

[0079] This configuration can prevent the multiple first terahertz elements 21 and the multiple second terahertz elements 22 from both oscillating and the multiple first terahertz elements 21 and the multiple second terahertz elements 22 from both detecting.

[0080] (1-5) The control device 30 includes a signal processing circuit 34 that processes signals output from the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 into digital signals. The control device 30 includes a selection circuit 35 electrically connected to the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, and the signal processing circuit 34. The selection circuit 35 is configured to selectively output, to the signal processing circuit 34, a first detection signal SR1 detected by the plurality of first terahertz elements 21 and a second detection signal SR2 detected by the plurality of second terahertz elements 22.

[0081] According to this configuration, the second terahertz element 22 is in an oscillation state when the first detection signal SR1 is output to the signal processing circuit 34. In this case, the selection circuit 35 selectively outputs the first detection signal SR1 to the signal processing circuit 34, and therefore does not output a signal from the second terahertz element 22 to the signal processing circuit 34. On the other hand, the first terahertz element 21 is in an oscillation state when the second detection signal SR2 is output to the signal processing circuit 34. In this case, the selection circuit 35 selectively outputs the second detection signal SR2 to the signal processing circuit 34, and therefore does not output a signal from the first terahertz element 21 to the signal processing circuit 34. In this way, the selection circuit 35 is configured not to output a signal from the terahertz element in an oscillation state to the signal processing circuit 34. In other words, it is possible to output only a detection signal to the signal processing circuit 34, and therefore a decrease in the detection accuracy of the terahertz wave W can be suppressed.

[0082] (1-6) The selection circuit 35 includes an analog switch 35A electrically connected to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. A plurality of analog switches 35A are provided corresponding to the number of combinations of the first terahertz elements 21 and the second terahertz elements 22. The control device 30 is configured to individually control the plurality of analog switches 35A.

[0083] According to this configuration, the number of analog switches 35A can be reduced compared to when an analog switch 35A is provided corresponding to each of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22.

[0084] (1-7) The control device 30 includes a timing generation circuit 36 ​​configured to switch between the first state and the second state at predetermined intervals. The predetermined interval is a period during which the modulation circuit 32A can output the modulated signal multiple times.

[0085] According to this configuration, after each second terahertz element 22 detects the terahertz wave W in the first state, a period for the signal processing circuit 34 to perform signal processing can be secured, and after each first terahertz element 21 detects the terahertz wave W in the second state, a period for the signal processing circuit 34 to perform signal processing can be secured.

[0086] (1-8) The plurality of first terahertz elements 21 include first electrodes 43 and second electrodes 44 as first terminals that serve as output terminals in the first state and as input terminals in the second state. The plurality of second terahertz elements 22 include first electrodes 43 and second electrodes 44 as second terminals that serve as input terminals in the first state and as output terminals in the second state.

[0087] According to this configuration, compared to a configuration in which each first terahertz element 21 includes an input-only terminal and an output-only terminal, it is possible to reduce the size of each first terahertz element 21. Compared to a configuration in which each second terahertz element 22 includes an input-only terminal and an output-only terminal, it is possible to reduce the size of each second terahertz element 22. Therefore, it is possible to densely arrange a plurality of first terahertz elements 21, and it is possible to densely arrange a plurality of second terahertz elements 22. Therefore, it is possible to reduce the area for arranging the terahertz elements.

[0088] Second Embodiment A terahertz system 10 according to a second embodiment will be described with reference to Figures 13 to 18. The terahertz system 10 according to the second embodiment differs from the terahertz system 10 according to the first embodiment mainly in the configuration of the terahertz device 20. In the following, components common to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0089] Fig. 13 schematically shows the planar structure of the terahertz device 20 of the second embodiment. Fig. 14 shows the transition of the oscillation drive signal S1 applied to the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, the plurality of third terahertz elements 23 (described later), and the plurality of fourth terahertz elements 24 (described later). Figs. 15 to 18 schematically show the planar structure of the terahertz device 20, showing the oscillation state and non-oscillation state (detection state) of the first to fourth terahertz elements 21 to 24.

[0090] As shown in Figure 13, the terahertz device 20 of the second embodiment further includes a plurality (four in the second embodiment) of third terahertz elements 23 that oscillate and detect terahertz waves W, and a plurality (four in the second embodiment) of fourth terahertz elements 24 that oscillate and detect terahertz waves W.

[0091] The third terahertz elements 23 are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. The third terahertz elements 23 are arranged on the opposite side of the first terahertz elements 21 with respect to the second terahertz elements 22 in the Y direction.

[0092] The plurality of fourth terahertz elements 24 are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. The plurality of fourth terahertz elements 24 are arranged on the opposite side of the plurality of second terahertz elements 22 with respect to the plurality of third terahertz elements 23 in the Y direction.

[0093] In this way, the first to fourth terahertz elements 21 to 24 are arranged in a matrix in plan view. If the X direction is defined as rows and the Y direction is defined as columns, the first to fourth terahertz elements 21 to 24 can be said to be arranged in rows.

[0094] The control device 30 (see FIG. 1) is configured to switch the combination of oscillation and detection states of the first to fourth terahertz elements 21 to 24 between first to fourth states. As shown in FIG. 15 , the first state is a state in which the plurality of first terahertz elements 21 oscillate terahertz waves W, and the plurality of second terahertz elements 22, the plurality of third terahertz elements 23, and the plurality of fourth terahertz elements 24 detect the terahertz waves W. That is, in the first state, the plurality of first terahertz elements 21 are in an oscillation state, and the plurality of second to fourth terahertz elements 22 to 24 are in a non-oscillation state (detection state).

[0095] 16 , the second state is a state in which the plurality of second terahertz elements 22 oscillate terahertz waves W, and the plurality of first terahertz elements 21, the plurality of third terahertz elements 23, and the plurality of fourth terahertz elements 24 detect the terahertz waves W. That is, in the second state, the plurality of second terahertz elements 22 are in an oscillation state, and the plurality of first, third, and fourth terahertz elements 21, 23, and 24 are in a non-oscillation state (detection state).

[0096] 17 , the third state is a state in which the plurality of third terahertz elements 23 oscillate terahertz waves W, and the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, and the plurality of fourth terahertz elements 24 detect the terahertz waves W. That is, in the third state, the plurality of third terahertz elements 23 are in an oscillation state, and the plurality of first, second, and fourth terahertz elements 21, 22, and 24 are in a non-oscillation state (detection state).

[0097] 18 , the fourth state is a state in which the plurality of fourth terahertz elements 24 oscillate terahertz waves W, and the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, and the plurality of third terahertz elements 23 detect the terahertz waves W. That is, in the fourth state, the plurality of fourth terahertz elements 24 are in an oscillation state, and the plurality of first to third terahertz elements 21 to 23 are in a non-oscillation state (detection state).

[0098] Next, an example of the operation of the first to fourth terahertz elements 21 to 24 will be described. As shown in FIG. 14 , the timing generation circuit 36 ​​in FIG. 4 and the analog switch 31E of the power supply control circuit 31 in FIG. 3 switch among the first, second, third, and fourth states at predetermined intervals. Specifically, the first state is set during a first period T1 from time (2n-2)T ​​to time (2n-1)T, the second state is set during a second period T2 from time (2n-1)T to time 2nT, the third state is set during a third period T3 from time 2nT to time (2n+1)T, and the fourth state is set during a fourth period T4 from time (2n+1)T to time (2n+2)T. In this way, the first state is switched to the second state at time (2n-1)T, the second state is switched to the third state at time 2nT, and the third state is switched to the fourth state at time (2n+1)T.

[0099] During the first period T1, an oscillation drive signal S1 is applied to the plurality of first terahertz elements 21, and a detection drive signal S2 is applied to the plurality of second to fourth terahertz elements 22 to 24. As a result, as shown in FIG. 15 , the plurality of first terahertz elements 21 enter an oscillation state, and the plurality of second to fourth terahertz elements 22 to 24 enter a non-oscillation state (detection state). Therefore, the plurality of first terahertz elements 21 emit terahertz waves W toward the detection object 100 (see FIG. 1 ). Then, the plurality of second to fourth terahertz elements 22 to 24 detect the terahertz waves W reflected from the detection object 100.

[0100] In the second period T2, a detection bias voltage VB2 is applied to the plurality of first terahertz elements 21, an oscillation drive signal S1 is applied to the plurality of second terahertz elements 22, and a detection drive signal S2 is applied to the plurality of third terahertz elements 23 and the plurality of fourth terahertz elements 24. As a result, as shown in FIG. 16 , the plurality of first, third, and fourth terahertz elements 21, 23, and 24 enter a non-oscillation state (detection state), and the plurality of second terahertz elements 22 enter an oscillation state. Therefore, the plurality of second terahertz elements 22 emit terahertz waves W toward the detection object 100. Then, the plurality of first, third, and fourth terahertz elements 21, 23, and 24 detect the terahertz waves W reflected from the detection object 100.

[0101] In the third period T3, the oscillation drive signal S1 is applied to the plurality of third terahertz elements 23, and the detection drive signal S2 is applied to the plurality of first, second, and fourth terahertz elements 21, 22, and 24. As a result, as shown in Fig. 17, the plurality of third terahertz elements 23 enter an oscillation state, and the plurality of first, second, and fourth terahertz elements 21, 22, and 24 enter a non-oscillation state (detection state). Therefore, the plurality of third terahertz elements 23 emit terahertz waves W toward the detection object 100. Then, the plurality of first, second, and fourth terahertz elements 21, 22, and 24 detect the terahertz waves W reflected from the detection object 100.

[0102] In the fourth period T4, the oscillation drive signal S1 is applied to the plurality of fourth terahertz elements 24, and the detection drive signal S2 is applied to the plurality of first to third terahertz elements 21 to 23. As a result, as shown in Fig. 18, the plurality of first to third terahertz elements 21 to 23 enter a non-oscillation state (detection state), and the plurality of fourth terahertz elements 24 enter an oscillation state. Therefore, the plurality of fourth terahertz elements 24 emit terahertz waves W toward the detection object 100. Then, the plurality of first to third terahertz elements 21 to 23 detect the terahertz waves W reflected from the detection object 100.

[0103] In this way, the terahertz system 10 performs an operation of oscillating one row of the plurality of first to fourth terahertz elements 21 to 24 and detecting with the remaining three rows of terahertz elements in accordance with the first to fourth periods T1 to T4, for each row. Note that the oscillation and detection of the plurality of first to fourth terahertz elements 21 to 24 may be repeated by repeating the first to fourth periods T1 to T4.

[0104] Here, the first to fourth periods T1 to T4 are set to periods sufficiently longer than the period of the modulation frequency. For example, when the modulation frequency is 1 MHz, each of the first to fourth periods T1 to T4 may be set to 1 msec. As a result, during the first period T1, a plurality of pulsed oscillation drive signals S1 are applied to the first terahertz element 21. During the second period T2, a plurality of pulsed oscillation drive signals S1 are applied to the second terahertz element 22. During the third period T3, a plurality of pulsed oscillation drive signals S1 are applied to the third terahertz element 23. During the fourth period T4, a plurality of pulsed oscillation drive signals S1 are applied to the fourth terahertz element 24. According to the second embodiment, the same effects as those of the first embodiment can be obtained.

[0105] [Application Example of Terahertz System] An application example of the terahertz system 10 of the second embodiment will be described. The terahertz system 10 of the second embodiment can be applied to, for example, an image sensor similar to a rolling shutter type CMOS (Complementary Metal Oxide Semiconductor) image sensor. In this image sensor, an image captured by the image sensor is read out by scanning, for example, a plurality of pixels arranged in a matrix, row by row or column by column.

[0106] In moving image shooting, for example, it is necessary to quickly read out the image from the image sensor, so that in moving image shooting, instead of reading out all the pixels of the image sensor, a thinning process is performed in which every other row is selected as the row to be scanned and the rows in between are skipped.

[0107] In this case, in the terahertz system 10, as a thinning process, for example, the first terahertz elements 21 oscillate as one row, and the second to fourth terahertz elements 22 to 24 detect as the remaining three rows. In this way, an image formed by the first to fourth terahertz elements 21 to 24 may be read out. Note that the number of oscillating terahertz elements in one row can be changed arbitrarily. Furthermore, the number of rows to be detected is not limited to three rows, and may be two rows of terahertz elements or one row of terahertz elements.

[0108] On the other hand, when capturing a still image as an image sensor, the terahertz system 10 repeats the process of oscillating the first to fourth terahertz elements 21 to 24 row by row and detecting the remaining three rows during the first to fourth periods T1 to T4 as described above. This allows information from the first to fourth terahertz elements 21 to 24 to be read out.

[0109] Third Embodiment A terahertz system 10 according to a third embodiment will be described with reference to Fig. 19. The terahertz system 10 according to the third embodiment differs from the terahertz system 10 according to the first embodiment mainly in the configurations of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. In the following, components common to the first embodiment are denoted by the same reference numerals, and descriptions thereof will be omitted.

[0110] FIG. 19 schematically illustrates the planar structure of a terahertz device 20 in a terahertz system 10 according to the third embodiment. As illustrated in FIG. 19 , the plurality of first terahertz elements 21 in the terahertz device 20 includes a first terahertz element 21P configured to be capable of oscillating and detecting a first terahertz wave W1 having a first oscillation frequency F1 and a first terahertz element 21Q configured to be capable of oscillating and detecting a second terahertz wave W2 having a second oscillation frequency F2 different from the first oscillation frequency F1. The plurality of second terahertz elements 22 include a second terahertz element 22P configured to be capable of oscillating and detecting the first terahertz wave W1 having the first oscillation frequency F1 and a second terahertz element 22Q configured to be capable of oscillating and detecting a second terahertz wave W2 having the second oscillation frequency F2. The first oscillation frequency F1 is, for example, 300 GHz. The second oscillation frequency F2 is, for example, 500 GHz.

[0111] In the third embodiment, a plurality of first terahertz elements 21P and 21Q are provided. In the third embodiment, the terahertz device 20 includes four first terahertz elements 21. The four first terahertz elements 21 include two first terahertz elements 21P and two first terahertz elements 21Q. In other words, the number of first terahertz elements 21P oscillating at the first oscillation frequency F1 is equal to the number of first terahertz elements 21Q oscillating at the second oscillation frequency F2. In addition, a plurality of second terahertz elements 22P and 22Q are provided. The terahertz device 20 includes four second terahertz elements 22. The four second terahertz elements 22 include two second terahertz elements 22P and four second terahertz elements 22Q. That is, the number of second terahertz elements 22P that oscillate at the first oscillation frequency F1 is equal to the number of second terahertz elements 22Q that oscillate at the second oscillation frequency F2.

[0112] Next, an example of the operation of the terahertz system 10 will be described. In the first state, the first terahertz wave W1 from the first terahertz element 21P is reflected by the detection object 100 (see FIG. 1 ) and then detected by the second terahertz element 22P. The second terahertz wave W2 from the first terahertz element 21Q is reflected by the detection object 100 and then detected by the second terahertz element 22Q. In other words, the first terahertz wave W1 from the first terahertz element 21P, which oscillates the first terahertz wave W1 at the first oscillation frequency F1, is detected by the second terahertz element 22P, which oscillates the first terahertz wave W1 at the first oscillation frequency F1. The second terahertz wave W2 from the first terahertz element 21Q that oscillates the second terahertz wave W2 at the second oscillation frequency F2 is detected by the second terahertz element 22Q that oscillates the second terahertz wave W2 at the second oscillation frequency F2.

[0113] In the second state, the first terahertz wave W1 from the second terahertz element 22P is reflected by the detection object 100 and then detected by the first terahertz element 21P. The second terahertz wave W2 from the second terahertz element 22Q is reflected by the detection object 100 and then detected by the first terahertz element 21Q. That is, the first terahertz wave W1 from the second terahertz element 22P that oscillates the first terahertz wave W1 at the first oscillation frequency F1 is detected by the first terahertz element 21P that oscillates the first terahertz wave W1 at the first oscillation frequency F1. The second terahertz wave W2 from the second terahertz element 22Q that oscillates the second terahertz wave W2 at the second oscillation frequency F2 is detected by the first terahertz element 21Q that oscillates the second terahertz wave W2 at the second oscillation frequency F2.

[0114] [Effects of Third Embodiment] The terahertz system 10 of the third embodiment provides the following effects. (3-1) The plurality of first terahertz elements 21 include a first terahertz element 21P that oscillates and performs detection at a first oscillation frequency F1 and a first terahertz element 21Q that oscillates at a second oscillation frequency F2 that is different from the first oscillation frequency F1. The plurality of second terahertz elements 22 include a second terahertz element 22P that oscillates at the first oscillation frequency F1 and a second terahertz element 22Q that oscillates and performs detection at the second oscillation frequency F2.

[0115] According to this configuration, by varying the oscillation frequency, it is possible to obtain, for example, information on the position where the first terahertz wave W1 is emitted and the position where the first terahertz wave W1 is detected, and information on the position where the second terahertz wave W2 is emitted and the position where the second terahertz wave W2 is detected. This makes it possible to obtain the optical path states of the first terahertz wave W1 and the second terahertz wave W2. Furthermore, it is possible to obtain the spectroscopic characteristics of the detection target object 100 based on the signal intensity when the first terahertz wave W1 is detected and the signal intensity when the second terahertz wave W2 is detected.

[0116] <Modifications> The above-described embodiments can be modified as follows: Furthermore, the above-described embodiments and the following modifications can be combined with each other to the extent that no technical contradiction occurs.

[0117] The second and third embodiments can be combined, that is, the first to fourth terahertz elements 21 to 24 can be terahertz elements with different oscillation frequencies.

[0118] In the first and third embodiments, the plurality of first terahertz elements 21 arranged in the X direction and the plurality of second terahertz elements 22 arranged in the X direction may be arranged alternately one by one in the Y direction. In this case, the control device 30 may be configured to switch between a first state in which the first terahertz elements 21 in the plurality of rows emit terahertz waves W and the second terahertz elements 22 in the plurality of rows detect the terahertz waves W, and a second state in which the second terahertz elements 22 in the plurality of rows emit terahertz waves W and the first terahertz elements 21 in the plurality of rows detect the terahertz waves W. In this way, when the terahertz system 10 of the modified example is applied to an image sensor, interlaced scanning can be performed.

[0119] In the first and third embodiments, it is possible to arbitrarily change the arrangement of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. In one example, as shown in Fig. 20 , the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be arranged in a line in the X direction.

[0120] In the first embodiment, the modulation frequency of the modulation signal included in the oscillation drive signal S1 applied to the plurality of first terahertz elements 21 may be different from the modulation frequency of the modulation signal included in the oscillation drive signal S1 applied to the plurality of second terahertz elements 22. That is, the plurality of first terahertz elements 21 may include first terahertz elements 21 to which a first oscillation drive signal in which a modulation signal with a first modulation frequency is superimposed on an oscillation bias voltage VB1 is applied, and first terahertz elements 21 to which a second oscillation drive signal in which a modulation signal with a second modulation frequency different from the first modulation frequency is superimposed on the oscillation bias voltage VB1 is applied. Similarly, the plurality of second terahertz elements 22 may include second terahertz elements 22 to which a first oscillation drive signal in which a modulation signal with a first modulation frequency is superimposed on an oscillation bias voltage VB1 is applied, and second terahertz elements 22 to which a second oscillation drive signal in which a modulation signal with a second modulation frequency is superimposed on the oscillation bias voltage VB1 is applied. Here, the first modulation frequency may be, for example, 1 MHz, and the second modulation frequency may be, for example, 0.9 MHz.

[0121] By varying the modulation frequency in this manner, it is possible to obtain information on, for example, the position where the terahertz wave is emitted and the position where the terahertz wave is detected. This makes it possible to obtain the optical path state of the terahertz wave. Furthermore, it is possible to obtain the spectroscopic characteristics of the detection target 100 based on the signal intensity when the first terahertz wave W1 is detected and the signal intensity when the second terahertz wave W2 is detected.

[0122] In the first and third embodiments, the number of first terahertz elements 21 and the number of second terahertz elements 22 may be different from each other. In one example, as shown in Fig. 21 , the number of second terahertz elements 22 may be less than the number of first terahertz elements 21. In the example shown in Fig. 21 , two second terahertz elements 22 are arranged adjacent to each other in the X direction at the center of the substrate 25 in the X direction.

[0123] The arrangement of the two first terahertz elements 21 can be changed arbitrarily. In one example, the two second terahertz elements 22 may be arranged offset from the center of the substrate 25 in the X direction. In another example, the two second terahertz elements 22 may be arranged spaced apart from each other in the X direction. That is, the distance between the two second terahertz elements 22 in the X direction may be greater than the distance between adjacent first terahertz elements 21 in the X direction among the multiple first terahertz elements 21. Furthermore, the number of first terahertz elements 21 may be smaller than the number of second terahertz elements 22.

[0124] In the third embodiment, the arrangement of the first terahertz elements 21P and 21Q having different oscillation frequencies and the second terahertz elements 22P and 22Q having different oscillation frequencies can be changed as desired. The arrangement can be changed as shown in the first to third examples in FIGS. 22 to 24, for example.

[0125] 22 , two first terahertz elements 21P oscillating at a first oscillation frequency F1 may be arranged side by side in the X direction, and two first terahertz elements 21Q oscillating at a second oscillation frequency F2 may be arranged side by side in the X direction. Two second terahertz elements 22P oscillating at the first oscillation frequency F1 may be arranged side by side in the X direction, and two second terahertz elements 22Q oscillating at the second oscillation frequency F2 may be arranged side by side in the X direction. In the example shown in FIG. 22 , the two first terahertz elements 21P are arranged adjacent to the two second terahertz elements 22P in the Y direction. The two first terahertz elements 21Q are arranged adjacent to the two second terahertz elements 22Q in the Y direction.

[0126] In addition, the two first terahertz elements 21P may be arranged adjacent to the two second terahertz elements 22Q in the Y direction, and the two first terahertz elements 21Q may be arranged adjacent to the two second terahertz elements 22P in the Y direction.

[0127] 23 , the plurality of first terahertz elements 21 may include three first terahertz elements 21P that oscillate at a first oscillation frequency F1 and one first terahertz element 21Q that oscillates at a second oscillation frequency F2. That is, the number of first terahertz elements 21P and the number of first terahertz elements 21Q may be different from each other. In the example shown in FIG. 23 , the first terahertz element 21Q may be disposed at an end of the plurality of first terahertz elements 21 in the X direction. The three first terahertz elements 21P may be arranged adjacent to each other in the X direction.

[0128] The plurality of second terahertz elements 22 may include three second terahertz elements 22P oscillating at the first oscillation frequency F1 and one second terahertz element 22Q oscillating at the second oscillation frequency F2. That is, the number of second terahertz elements 22P may be different from the number of second terahertz elements 22Q. In the example shown in FIG. 23 , the second terahertz element 22Q may be disposed at an end of the plurality of second terahertz elements 22 in the X direction. The three second terahertz elements 22P may be arranged adjacent to each other in the X direction. In the example shown in FIG. 23 , the second terahertz element 22P may be disposed adjacent to the first terahertz element 21P in the Y direction.

[0129] The second terahertz element 22Q may be disposed at a position different from the position adjacent to the first terahertz element 21Q in the Y direction. Furthermore, each of the first terahertz element 21Q and the second terahertz element 22Q may be disposed at a position different from the end of the substrate 25 in the X direction.

[0130] In the second example, the number of first terahertz elements 21P and the number of second terahertz elements 22P may be different from each other. The number of first terahertz elements 21Q and the number of second terahertz elements 22Q may be different from each other.

[0131] 24 , when a plurality of first terahertz elements 21 and a plurality of second terahertz elements 22 are arranged in a line in the X direction, the first terahertz elements 21P and the second terahertz elements 22P may be arranged side by side in the X direction at the center of the substrate 25 in the X direction. In the example shown in FIG. 24 , the plurality of first terahertz elements 21 include three first terahertz elements 21P that oscillate at the first oscillation frequency F1 and one first terahertz element 21Q that oscillates at the second oscillation frequency F2. The plurality of second terahertz elements 22 include three second terahertz elements 22P that oscillate at the first oscillation frequency F1 and one second terahertz element 22Q that oscillates at the second oscillation frequency F2. In other words, the number of first terahertz elements 21P and the number of first terahertz elements 21Q are different from each other. The number of second terahertz elements 22P and the number of second terahertz elements 22Q are different from each other.

[0132] At least one of the first terahertz elements 21Q and the second terahertz elements 22Q may be disposed between the first terahertz elements 21P and the first terahertz elements 21Q in the X direction. The number of the first terahertz elements 21P and the number of the first terahertz elements 21Q may be the same. The number of the second terahertz elements 22P and the number of the second terahertz elements 22Q may be the same.

[0133] In the first embodiment, the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be configured to oscillate and detect at different oscillation frequencies. In one example, the plurality of first terahertz elements 21 may be configured to be capable of oscillating and detecting at a first oscillation frequency F1. In another example, the plurality of second terahertz elements 22 may be configured to be capable of oscillating and detecting at a second oscillation frequency F2 different from the first oscillation frequency F1.

[0134] In the second embodiment, the first to fourth terahertz elements 21 to 24 may include a terahertz element that oscillates at a first oscillation frequency F1 and a terahertz element that oscillates at a second oscillation frequency F2. The configuration of the first to fourth terahertz elements 21 to 24 can be changed, for example, as in a first example shown in FIG. 25 and a second example shown in FIG. 26.

[0135] 25 , each of the plurality of first terahertz elements 21 and the plurality of fourth terahertz elements 24 may be configured to oscillate at a first oscillation frequency F1. Each of the plurality of second terahertz elements 22 and the plurality of third terahertz elements 23 may be configured to oscillate at a second oscillation frequency F2.

[0136] 25 , in the first state, the terahertz waves W radiated from the plurality of first terahertz elements 21 can be detected by the plurality of fourth terahertz elements 24. In the second state, the terahertz waves W radiated from the plurality of second terahertz elements 22 can be detected by the plurality of third terahertz elements 23. In the third state, the terahertz waves W radiated from the plurality of third terahertz elements 23 can be detected by the plurality of second terahertz elements 22. In the fourth state, the terahertz waves W radiated from the plurality of fourth terahertz elements 24 can be detected by the plurality of first terahertz elements 21.

[0137] 26 , the plurality of first terahertz elements 21 include two first terahertz elements 21P that oscillate at a first oscillation frequency F1 and two first terahertz elements 21Q that oscillate at a second oscillation frequency F2. The plurality of second terahertz elements 22 include two second terahertz elements 22P that oscillate at the first oscillation frequency F1 and two second terahertz elements 22Q that oscillate at the second oscillation frequency F2. The plurality of third terahertz elements 23 include two third terahertz elements 23P that oscillate at the first oscillation frequency F1 and two third terahertz elements 23Q that oscillate at the second oscillation frequency F2. The plurality of fourth terahertz elements 24 include two fourth terahertz elements 24P that oscillate at a first oscillation frequency F1 and two fourth terahertz elements 24Q that oscillate at a second oscillation frequency F2.

[0138] In the example shown in FIG. 26 , two first terahertz elements 21P are arranged side by side in the X direction. Two first terahertz elements 21Q are arranged side by side in the X direction. Two second terahertz elements 22P are arranged side by side in the X direction. Two second terahertz elements 22Q are arranged side by side in the X direction. Two second terahertz elements 22P are arranged at positions adjacent to the two first terahertz elements 21P in the Y direction. Two second terahertz elements 22Q are arranged at positions adjacent to the two first terahertz elements 21Q in the Y direction. Two third terahertz elements 23P are arranged side by side in the X direction. Two third terahertz elements 23Q are arranged side by side in the X direction. Two third terahertz elements 23P are arranged at positions adjacent to the two second terahertz elements 22P in the Y direction. The two third terahertz elements 23Q are arranged at positions adjacent to the two second terahertz elements 22Q in the Y direction. The two fourth terahertz elements 24P are arranged side by side in the X direction. The two fourth terahertz elements 24Q are arranged side by side in the X direction. The two fourth terahertz elements 24P are arranged at positions adjacent to the two third terahertz elements 23P in the Y direction. The two fourth terahertz elements 24Q are arranged at positions adjacent to the two third terahertz elements 23Q in the Y direction.

[0139] 26 , in the first state, the first terahertz waves W1 radiated from the plurality of first terahertz elements 21P can be detected by the plurality of second to fourth terahertz elements 22P to 24P. The second terahertz waves W2 radiated from the plurality of first terahertz elements 21Q can be detected by the plurality of second to fourth terahertz elements 22Q to 24Q. In the second state, the first terahertz waves W1 radiated from the plurality of second terahertz elements 22P can be detected by the plurality of first, third, and fourth terahertz elements 21P, 23P, and 24P. The second terahertz waves W2 radiated from the plurality of second terahertz elements 22Q can be detected by the plurality of first, third, and fourth terahertz elements 21Q, 23Q, and 24Q. In the third state, the first terahertz waves W1 radiated from the plurality of third terahertz elements 23P can be detected by the plurality of first, second, and fourth terahertz elements 21P, 22P, and 24P. The second terahertz waves W2 radiated from the plurality of third terahertz elements 23Q can be detected by the plurality of first, second, and fourth terahertz elements 21Q, 22Q, and 24Q. In the fourth state, the first terahertz waves W1 radiated from the plurality of fourth terahertz elements 24P can be detected by the plurality of first to third terahertz elements 21P to 23P. The second terahertz waves W2 radiated from the plurality of fourth terahertz elements 24Q can be detected by the plurality of first to third terahertz elements 21Q to 23Q.

[0140] The number and arrangement of the first terahertz elements 21P, 21Q, the second terahertz elements 22P, 22Q, the third terahertz elements 23P, 23Q, and the fourth terahertz elements 24P, 24Q can be changed as desired. For example, the number of first terahertz elements 21P and the number of first terahertz elements 21Q may be different from each other. For example, the number of second terahertz elements 22P and the number of second terahertz elements 22Q may be different from each other. For example, the number of third terahertz elements 23P and the number of third terahertz elements 23Q may be different from each other. For example, the number of fourth terahertz elements 24P and the number of fourth terahertz elements 24Q may be different from each other. For example, the first terahertz element 21P (21Q) may be arranged at a position different from the position adjacent to the second terahertz element 22P (22Q) in the Y direction. In one example, the second terahertz element 22P (22Q) may be disposed at a position different from the position adjacent to the third terahertz element 23P (23Q) in the Y direction. In another example, the third terahertz element 23P (23Q) may be disposed at a position different from the position adjacent to the fourth terahertz element 24P (24Q) in the Y direction.

[0141] In the second embodiment, it is possible to arbitrarily change the oscillation timing and detection timing of the first to fourth terahertz elements 21 to 24. In this case, the control device 30 may be configured to individually control the oscillation state and detection state of the first to fourth terahertz elements 21 to 24.

[0142] 27 , the control device 30 (see FIG. 4 ) may be configured to be switchable between a first state in which the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 oscillate and the plurality of third terahertz elements 23 and the plurality of fourth terahertz elements 24 perform detection, and a second state in which the plurality of third terahertz elements 23 and the plurality of fourth terahertz elements 24 oscillate and the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 perform detection. In other words, the control device 30 may control the oscillation states and detection states of the plurality of terahertz elements so that two adjacent rows of terahertz elements oscillate and the remaining two adjacent rows of terahertz elements perform detection.

[0143] 28 , the control device 30 may be configured to be switchable between a first state in which the plurality of first terahertz elements 21 and the plurality of fourth terahertz elements 24 are oscillated and the plurality of second terahertz elements 22 and the plurality of third terahertz elements 23 are detected, and a second state in which the plurality of second terahertz elements 22 and the plurality of third terahertz elements 23 are oscillated and the plurality of first terahertz elements 21 and the plurality of fourth terahertz elements 24 are detected. In other words, the control device 30 may control the oscillation state and the detection state of the plurality of terahertz elements so that two rows of terahertz elements spaced apart in the Y direction oscillate and the remaining two rows of terahertz elements perform detection.

[0144] In the modified example shown in FIG. 27, one of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be configured to oscillate and detect a first terahertz wave W1 of a first oscillation frequency F1, and the other of the plurality of terahertz elements may be configured to oscillate and detect a second terahertz wave W2 of a second oscillation frequency F2 different from the first oscillation frequency F1.

[0145] One of the plurality of third terahertz elements 23 and the plurality of fourth terahertz elements 24 may be configured to oscillate and detect a first terahertz wave W1 of a first oscillation frequency F1, and the other of the plurality of terahertz elements may be configured to oscillate and detect a second terahertz wave W2 of a second oscillation frequency F2.

[0146] In one example, the first terahertz element 21 and the third terahertz element 23 may be configured to oscillate and detect a first terahertz wave W1 having a first oscillation frequency F1, and the second terahertz element 22 and the fourth terahertz element 24 may be configured to oscillate and detect a second terahertz wave W2 having a second oscillation frequency F2.

[0147] In the modified example shown in FIG. 28 , one of the plurality of first terahertz elements 21 and the plurality of fourth terahertz elements 24 may be configured to oscillate and detect a first terahertz wave W1 of a first oscillation frequency F1, and the other of the plurality of terahertz elements may be configured to oscillate and detect a second terahertz wave W2 of a second oscillation frequency F2 different from the first oscillation frequency F1.

[0148] One of the plurality of second terahertz elements 22 and the plurality of third terahertz elements 23 may be configured to oscillate and detect a first terahertz wave W1 of a first oscillation frequency F1, and the other of the plurality of terahertz elements may be configured to oscillate and detect a second terahertz wave W2 of a second oscillation frequency F2.

[0149] In one example, the first terahertz element 21 and the second terahertz element 22 may be configured to oscillate and detect a first terahertz wave W1 having a first oscillation frequency F1, and the third terahertz element 23 and the fourth terahertz element 24 may be configured to oscillate and detect a second terahertz wave W2 having a second oscillation frequency F2.

[0150] In the second embodiment and the modified examples shown in FIGS. 27 and 28 , the number of the plurality of first terahertz elements 21 may be different from the number of the plurality of second terahertz elements 22. The number of the plurality of first terahertz elements 21 may be different from the number of the plurality of third terahertz elements 23. The number of the plurality of first terahertz elements 21 may be different from the number of the plurality of fourth terahertz elements 24. The number of the plurality of second terahertz elements 22 may be different from the number of the plurality of third terahertz elements 23. The number of the plurality of second terahertz elements 22 may be different from the number of the plurality of fourth terahertz elements 24. The number of the plurality of third terahertz elements 23 may be different from the number of the plurality of fourth terahertz elements 24.

[0151] In the second embodiment, the plurality of fourth terahertz elements 24 may be omitted from the terahertz device 20. In this case, the control device 30 may be configured to switch between a first state in which the plurality of first terahertz elements 21 oscillate terahertz waves W and the plurality of second terahertz elements 22 and the plurality of third terahertz elements 23 detect the terahertz waves W, a second state in which the plurality of second terahertz elements 22 oscillate terahertz waves W and the plurality of first terahertz elements 21 and the plurality of third terahertz elements 23 detect the terahertz waves W, and a third state in which the plurality of third terahertz elements 23 oscillate terahertz waves W and the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 detect the terahertz waves W.

[0152] In the third embodiment, the multiple first terahertz elements 21 include two types of first terahertz elements 21 with different oscillation frequencies, and the multiple second terahertz elements 22 include two types of second terahertz elements 22 with different oscillation frequencies, but this is not limited to this. The multiple first terahertz elements 21 may include three or more types of first terahertz elements 21 with different oscillation frequencies. The multiple second terahertz elements 22 may include three or more types of second terahertz elements 22 with different oscillation frequencies. Even when three types of first terahertz elements and second terahertz elements with different oscillation frequencies are included, it is preferable that the different oscillation frequencies of the multiple first terahertz elements 21 and the different oscillation frequencies of the multiple second terahertz elements 22 are the same. In other words, when the plurality of first terahertz elements 21 include a first terahertz element 21 of a first oscillation frequency F1, a first terahertz element 21 of a second oscillation frequency F2, and a first terahertz element 21 of a third oscillation frequency F3, it is preferable that the plurality of second terahertz elements 22 include a second terahertz element 22 of a first oscillation frequency F1, a second terahertz element 22 of a second oscillation frequency F2, and a second terahertz element 22 of a third oscillation frequency F3.

[0153] In the third embodiment, the first terahertz element 21P is configured to be able to oscillate and detect the first terahertz wave W1 having the first oscillation frequency F1, and the first terahertz element 21Q is configured to be able to oscillate and detect the second terahertz wave W2 having the second oscillation frequency F2. However, this is not limited to this. The first terahertz elements 21P and 21Q may have the same structure, and different oscillation bias voltages VB1 may be supplied to the first terahertz element 21P and the first terahertz element 21Q. The first terahertz elements 21P and 21Q may emit terahertz waves W having an oscillation frequency corresponding to the supplied oscillation bias voltage VB1. For example, the control device 30 may be configured to apply different oscillation bias voltages VB1 to the first terahertz elements 21P and 21Q. That is, a first oscillation bias voltage VB11 may be applied to the first terahertz element 21P so that the first terahertz element 21P oscillates a first terahertz wave W1 having a first oscillation frequency F1. A second oscillation bias voltage VB12 may be applied to the first terahertz element 21Q so that the first terahertz element 21Q oscillates a second terahertz wave W2 having a second oscillation frequency F2. In this case, the first oscillation bias voltage VB11 and the second oscillation bias voltage VB12 are different from each other. The first oscillation frequency F1 is, for example, 290 GHz. The second oscillation frequency F2 is, for example, 370 GHz.

[0154] Furthermore, the control device 30 may be configured to apply different detection bias voltages VB2 to the first terahertz elements 21P and 21Q. That is, the first terahertz wave W1 having the first oscillation frequency F1 may be detected by applying a first detection bias voltage VB21 to the first terahertz element 21P. The second terahertz wave W2 having the second oscillation frequency F2 may be detected by applying a second detection bias voltage VB22 to the first terahertz element 21Q. In this case, the first detection bias voltage VB21 and the second detection bias voltage VB22 are different from each other.

[0155] In the third embodiment, the second terahertz element 22P is configured to be capable of oscillating and detecting the first terahertz wave W1 having the first oscillation frequency F1, and the second terahertz element 22Q is configured to be capable of oscillating and detecting the second terahertz wave W2 having the second oscillation frequency F2. However, this is not limited to this. The second terahertz elements 22P and 22Q may have the same structure, and different oscillation bias voltages VB1 may be supplied to the second terahertz elements 22P and 22Q. The second terahertz elements 22P and 22Q may emit terahertz waves W having an oscillation frequency corresponding to the supplied oscillation bias voltage VB1. For example, the control device 30 may be configured to apply different oscillation bias voltages VB1 to the second terahertz elements 22P and 22Q. That is, the first oscillation bias voltage VB11 may be applied to the second terahertz element 22P so that the second terahertz element 22P oscillates the first terahertz wave W1 having the first oscillation frequency F1. The second oscillation bias voltage VB12 may be applied to the second terahertz element 22Q so that the second terahertz element 22Q oscillates the second terahertz wave W2 having the second oscillation frequency F2. In this case, the first oscillation bias voltage VB11 and the second oscillation bias voltage VB12 are different from each other.

[0156] Furthermore, the control device 30 may be configured to apply different detection bias voltages VB2 to the second terahertz elements 22P and 22Q. That is, the first terahertz wave W1 having the first oscillation frequency F1 may be detected by applying a first detection bias voltage VB21 to the second terahertz element 22P. The second terahertz wave W2 having the second oscillation frequency F2 may be detected by applying a second detection bias voltage VB22 to the second terahertz element 22Q. In this case, the first detection bias voltage VB21 and the second detection bias voltage VB22 are different from each other.

[0157] The oscillation bias voltages VB11 and VB12 applied to the first terahertz elements 21P and 21Q may be different from the oscillation bias voltages VB11 and VB12 applied to the second terahertz elements 22P and 22Q. The detection bias voltages VB21 and VB22 applied to the first terahertz elements 21P and 21Q may be different from the detection bias voltages VB21 and VB22 applied to the second terahertz elements 22P and 22Q.

[0158] In contrast to the third embodiment, the terahertz system 10 may be configured such that the multiple first terahertz elements 21 and the multiple second terahertz elements 22 have different oscillating frequencies and detectable frequencies. In one example, the multiple first terahertz elements 21 and the multiple second terahertz elements 22 may have the same structure. In a modified example, the terahertz system 10 may be configured such that the first terahertz elements 21P and 21Q oscillate at a first oscillation frequency F1, and the second terahertz elements 22P and 22Q oscillate at a second oscillation frequency F2. The first terahertz elements 21P and 21Q may be configured to detect a second terahertz wave W2 having the second oscillation frequency F2, and the second terahertz elements 22P and 22Q may be configured to detect a first terahertz wave W1 having the first oscillation frequency F1.

[0159] In one example, the bias voltages applied to the first terahertz elements 21P and 21Q and the bias voltages applied to the second terahertz elements 22P and 22Q are changed. More specifically, a first oscillation bias voltage VB11 is applied to each of the first terahertz elements 21P and 21Q so that the first terahertz wave W1 has a first oscillation frequency F1, and a second oscillation bias voltage VB12 is applied to each of the second terahertz elements 22P and 22Q so that the second terahertz wave W2 has a second oscillation frequency F2. In this case, the first oscillation bias voltage VB11 and the second oscillation bias voltage VB12 are different from each other. The first oscillation frequency F1 is, for example, 290 GHz. The second oscillation frequency F2 is, for example, 370 GHz.

[0160] Furthermore, a first detection bias voltage VB21 is applied to each of the first terahertz elements 21P and 21Q so that the first terahertz wave W2 having the second oscillation frequency F2 is detected. A second detection bias voltage VB22 is applied to each of the second terahertz elements 22P and 22Q so that the second terahertz wave W1 having the first oscillation frequency F1 is detected. In this case, the first detection bias voltage VB21 and the second detection bias voltage VB22 are different from each other.

[0161] The control device 30 is configured to switch between a first state in which the first terahertz elements 21P, 21Q oscillate a first terahertz wave W1 of a first oscillation frequency F1 and the second terahertz elements 22P, 22Q detect the first terahertz wave W1, and a second state in which the second terahertz elements 22P, 22Q oscillate a second terahertz wave W2 of a second oscillation frequency F2 and the first terahertz elements 21P, 21Q detect the second terahertz wave W2.

[0162] In the second embodiment, the first to fourth terahertz elements 21 to 24 may be configured to be capable of oscillating and detecting terahertz waves W having different oscillation frequencies depending on the bias voltages applied thereto. That is, a first oscillation bias voltage VB11 may be applied to the first terahertz element 21 so that the first terahertz element 21 oscillates a first terahertz wave W1 having a first oscillation frequency F1. A second oscillation bias voltage VB12 may be applied to the second terahertz element 22 so that the second terahertz element 22 oscillates a second terahertz wave W2 having a second oscillation frequency F2. A third oscillation bias voltage VB13 may be applied to the third terahertz element 23 so that the third terahertz element 23 oscillates a third terahertz wave W3 having a third oscillation frequency F3. A fourth oscillation bias voltage VB14 may be applied to the fourth terahertz element 24 so that the fourth terahertz element 24 oscillates a fourth terahertz wave W4 having a fourth oscillation frequency F4. Here, the first to fourth oscillation frequencies F1 to F4 are different from one another, and the first to fourth oscillation bias voltages VB11 to VB14 are different from one another from the oscillation bias voltage VB1.

[0163] Furthermore, a first detection bias voltage VB21 may be applied to the first to fourth terahertz elements 21 to 24 so that the first to fourth terahertz elements 21 to 24 detect the first terahertz wave W1. A second detection bias voltage VB22 may be applied to the first to fourth terahertz elements 21 to 24 so that the first to fourth terahertz elements 21 to 24 detect the second terahertz wave W2. A third detection bias voltage VB23 may be applied to the first to fourth terahertz elements 21 to 24 so that the first to fourth terahertz elements 21 to 24 detect the third terahertz wave W3. A fourth detection bias voltage VB24 may be applied to the first to fourth terahertz elements 21 to 24 so that the first to fourth terahertz elements 21 to 24 detect the fourth terahertz wave W4. Here, the first to fourth detection bias voltages VB21 to VB24 are detection bias voltages VB2 that are different from each other.

[0164] The control device 30 is configured to switch the combination of oscillation and detection states of the first to fourth terahertz elements 21 to 24 between first to fourth states. The first state is a state in which the plurality of first terahertz elements 21 oscillate a first terahertz wave W1, and the plurality of second terahertz elements 22, the plurality of third terahertz elements 23, and the plurality of fourth terahertz elements 24 detect the first terahertz wave W1. That is, in the first state, the plurality of first terahertz elements 21 are in an oscillation state, and the plurality of second to fourth terahertz elements 22 to 24 are in a non-oscillation state (detection state). Therefore, a first oscillation bias voltage VB11 is applied to each first terahertz element 21, and a first detection bias voltage VB21 is applied to each of the second to fourth terahertz elements 22 to 24.

[0165] The second state is a state in which the plurality of second terahertz elements 22 oscillate second terahertz waves W2, and the plurality of first terahertz elements 21, the plurality of third terahertz elements 23, and the plurality of fourth terahertz elements 24 detect the second terahertz waves W2. That is, in the second state, the plurality of second terahertz elements 22 are in an oscillation state, and the plurality of first, third, and fourth terahertz elements 21, 23, and 24 are in a non-oscillation state (detection state). Therefore, a second oscillation bias voltage VB12 is applied to each second terahertz element 22, and a second detection bias voltage VB22 is applied to each first terahertz element 21, each third terahertz element 23, and each fourth terahertz element 24.

[0166] The third state is a state in which the plurality of third terahertz elements 23 oscillate third terahertz waves W3, and the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, and the plurality of fourth terahertz elements 24 detect the third terahertz waves W3. That is, in the third state, the plurality of third terahertz elements 23 are in an oscillation state, and the plurality of first, second, and fourth terahertz elements 21, 22, and 24 are in a non-oscillation state (detection state). Therefore, a third oscillation bias voltage VB13 is applied to each third terahertz element 23, and a third detection bias voltage VB23 is applied to each first terahertz element 21, each second terahertz element 22, and each fourth terahertz element.

[0167] The fourth state is a state in which the plurality of fourth terahertz elements 24 oscillate fourth terahertz waves W4, and the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, and the plurality of third terahertz elements 23 detect the fourth terahertz waves W4. That is, in the fourth state, the plurality of fourth terahertz elements 24 are in an oscillation state, and the plurality of first to third terahertz elements 21 to 23 are in a non-oscillation state (detection state). Therefore, a fourth oscillation bias voltage VB14 is applied to each fourth terahertz element 24, and a fourth detection bias voltage VB24 is applied to each of the first to third terahertz elements 21 to 23.

[0168] Note that the oscillation bias voltage VB1 of any one of the first to fourth oscillation bias voltages VB11 to VB14 may be applied to the first to fourth terahertz elements 21 to 24. In one example, the first terahertz element 21 may be applied with any one of the second to fourth oscillation bias voltages VB12 to VB14. In one example, the second terahertz element 22 may be applied with any one of the first oscillation bias voltage VB11, the third oscillation bias voltage VB13, and the fourth oscillation bias voltage VB14. In one example, the third terahertz element 23 may be applied with any one of the first oscillation bias voltage VB11, the second oscillation bias voltage VB12, and the fourth oscillation bias voltage VB14. In one example, the fourth terahertz element 24 may be applied with any one of the first to third oscillation bias voltages VB11 to VB13.

[0169] In each embodiment, the configuration of the analog switch 35A of the selection circuit 35 can be changed as desired. For example, the analog switch 35A may be electrically connected to a plurality of first terahertz elements 21 and a plurality of second terahertz elements 22. In this case, for example, when the first detection signals SR1 of the plurality of first terahertz elements 21 are simultaneously input to the analog switch 35A, the first detection signals SR1 of the plurality of first terahertz elements 21 are input to the signal processing circuit 34 through the analog switch 35A as superimposed detection signals. Furthermore, for example, when the second detection signals SR2 of the plurality of second terahertz elements 22 are simultaneously input to the analog switch 35A, the second detection signals SR2 of the plurality of second terahertz elements 22 are input to the signal processing circuit 34 through the analog switch 35A as superimposed detection signals. In such a configuration including the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, and the analog switch 35A, it is preferable to provide a diode in the electrical connection path between the plurality of first terahertz elements 21 and the analog switch 35A to prevent the detection signal from leaking from the analog switch 35A to the plurality of first terahertz elements 21. It is also preferable to provide a diode in the electrical connection path between the plurality of second terahertz elements 22 and the analog switch 35A to prevent the detection signal from leaking from the analog switch 35A to the plurality of second terahertz elements 22. In another example, the selection circuit 35 may include analog switches 35A connected individually to the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22.

[0170] In the first and third embodiments, the first period T1, which is a period during which the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are in the first state, and the second period T2, which is a period during which the oscillation and detection states of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are in the second state, may be different from each other. In other words, the first period T1 may be longer or shorter than the second period T2.

[0171] In the second embodiment, the first period T1, the second period T2, the third period T3, and the fourth period T4 can be individually set when the oscillation and detection states of the first to fourth terahertz elements 21 to 24 are in the first state, the second period T2, the third period T3, and the fourth period T4, respectively. For example, the first to fourth periods T1 to T4 may be different from one another.

[0172] In each embodiment, the analog switch 31E alternately supplies the oscillation drive signal S1 and the detection drive signal S2 to the first terahertz element 21 and the second terahertz element 22. Alternatively, as shown in FIG. 29 , the control device 30 may be configured to generate a first drive signal S11 and a second drive signal S12 that alternately include a pulsed oscillation portion TP and a DC detection portion TQ, and to supply the first drive signal S11 to the first terahertz element 21 and the second drive signal S12 to the second terahertz element 22. The first drive signal S11 and the second drive signal S12 are signals that complementarily include an oscillation portion TP and a detection portion TQ. The first drive signal S11 and the second drive signal S12 may include a stop portion TR that supplies a predetermined voltage, for example, an off-state drive voltage VG, between the oscillation portion TP and the detection portion TQ.

[0173] In each embodiment, a transmission-type terahertz system may be used instead of a reflection-type terahertz system. More specifically, as shown in Fig. 30 , the terahertz system 10 includes a first terahertz device 110, a second terahertz device 120, and a control device 130. The first terahertz device 110 and the second terahertz device 120 are disposed opposite each other with the detection target 100 sandwiched therebetween. The control device 130 is configured to control the first terahertz device 110 and the second terahertz device 120.

[0174] 31 , the first terahertz device 110 includes a plurality of oscillation terahertz elements 111. The plurality of oscillation terahertz elements 111 include a first oscillation terahertz element 111P that oscillates a first terahertz wave W1 at a first oscillation frequency F1 and a second oscillation terahertz element 111Q that oscillates a second terahertz wave W2 at a second oscillation frequency F2 that is different from the first oscillation frequency F1. In the example shown in FIG. 31 , a plurality of first oscillation terahertz elements 111P and a plurality of second oscillation terahertz elements 111Q are provided. The number of first oscillation terahertz elements 111P and the number of second oscillation terahertz elements 111Q are equal to each other.

[0175] 31 , the multiple first oscillation terahertz elements 111P are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. It can also be said that the multiple first oscillation terahertz elements 111P are arranged side by side in the X direction. The multiple second oscillation terahertz elements 111Q are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. It can also be said that the multiple second oscillation terahertz elements 111Q are arranged side by side in the X direction. The multiple first oscillation terahertz elements 111P and the multiple second oscillation terahertz elements 111Q are arranged at positions adjacent to each other in the Y direction.

[0176] 32 , the second terahertz device 120 includes a plurality of detection terahertz elements 121. The plurality of detection terahertz elements 121 include a first detection terahertz element 121P that detects the first terahertz wave W1 and a second detection terahertz element 121Q that detects the second terahertz wave W2. In the example shown in FIG. 32 , a plurality of first detection terahertz elements 121P and a plurality of second detection terahertz elements 121Q are provided. The number of first detection terahertz elements 121P and the number of second detection terahertz elements 121Q are equal to each other.

[0177] 32 , the multiple first detection terahertz elements 121P are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. It can also be said that the multiple first detection terahertz elements 121P are arranged side by side in the X direction. The multiple second detection terahertz elements 121Q are arranged at the same positions in the Y direction and spaced apart from each other in the X direction. It can also be said that the multiple second detection terahertz elements 121Q are arranged side by side in the X direction. The multiple first detection terahertz elements 121P and the multiple second detection terahertz elements 121Q are arranged at positions adjacent to each other in the Y direction.

[0178] In this way, the first terahertz device 110 is an oscillation device that oscillates the first terahertz wave W1 and the second terahertz wave W2, and the second terahertz device 120 is a detection device that detects the first terahertz wave W1 and the second terahertz wave W2.

[0179] As shown in Figures 30 to 32, the first terahertz device 110 and the second terahertz device 120 are arranged opposite each other, so that the multiple first oscillation terahertz elements 111P and the multiple second oscillation terahertz elements 111Q are arranged opposite each other, and the multiple first detection terahertz elements 121P and the multiple second detection terahertz elements 121Q are arranged opposite each other.

[0180] Each of the first terahertz device 110 and the second terahertz device 120 may include a first terahertz element that oscillates and detects a first terahertz wave W1 of a first oscillation frequency F1, and a second terahertz element that oscillates and detects a second terahertz wave W2 of a second oscillation frequency F2 different from the first oscillation frequency F1. In this case, the control device 130 is configured to switch between a first state in which the first terahertz element of the first terahertz device 110 emits a first terahertz wave W1, the multiple second terahertz elements emit a second terahertz wave W2, the first terahertz element of the second terahertz device 120 detects the first terahertz wave W1, and the multiple second terahertz elements detect the second terahertz wave W2, and a second state in which the multiple first terahertz elements of the second terahertz device 120 emit the first terahertz wave W1, the multiple second terahertz elements emit the second terahertz wave W2, the multiple first terahertz elements of the first terahertz device 110 detect the first terahertz wave W1, and the multiple second terahertz elements detect the second terahertz wave W2.

[0181] Furthermore, the arrangement of the multiple first oscillation terahertz elements 111P and the multiple second oscillation terahertz elements 111Q of the first terahertz device 110 shown in Fig. 31 can be changed as desired. In one example, as shown in Fig. 33, the multiple first oscillation terahertz elements 111P and the multiple second oscillation terahertz elements 111Q may be arranged alternately one by one in the X direction. The multiple first oscillation terahertz elements 111P and the multiple second oscillation terahertz elements 111Q may be arranged adjacent to each other in the Y direction. In this way, the multiple first oscillation terahertz elements 111P and the multiple second oscillation terahertz elements 111Q may be arranged adjacent to each other.

[0182] The arrangement of the plurality of first detection terahertz elements 121P and the plurality of second detection terahertz elements 121Q of the second terahertz device 120 shown in Fig. 32 can be changed as desired. In one example, the plurality of first detection terahertz elements 121P and the plurality of second detection terahertz elements 121Q may be arranged adjacent to each other, similar to the plurality of first oscillation terahertz elements 111P and the plurality of second oscillation terahertz elements 111Q shown in Fig. 33 .

[0183] Furthermore, the number of the plurality of first oscillation terahertz elements 111P and the number of the plurality of second oscillation terahertz elements 111Q may be different from each other. The number of the plurality of first detection terahertz elements 121P and the number of the plurality of second detection terahertz elements 121Q may be different from each other. Furthermore, the number of the plurality of oscillation terahertz elements 111 may be different from the number of the plurality of detection terahertz elements 121.

[0184] In the first and third embodiments, the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are arranged spaced apart from each other in the X direction (first direction), but this is not limiting.

[0185] In one example, the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be arranged spaced apart from each other in the Y direction (second direction). That is, the plurality of first terahertz elements 21 may be arranged side by side in the Y direction. The plurality of second terahertz elements 22 may be arranged side by side in the Y direction. The plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be arranged adjacent to each other in the X direction (first direction).

[0186] In another example, the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be arranged alternately one by one in the X direction as shown in Fig. 34. In the example shown in Fig. 34, the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 are arranged alternately one by one in the X direction and are also arranged alternately one by one in the Y direction.

[0187] 35, the plurality of first terahertz elements 21 may be arranged in a first region RA, and the plurality of second terahertz elements 22 may be arranged in a second region RB adjacent to the first region RA. In the example shown in FIG. 35, the first region RA and the second region RB are adjacent to each other in the X direction.

[0188] The plurality of first terahertz elements 21 in the first region RA may be arranged at intervals in both the X direction and the Y direction. That is, the plurality of first terahertz elements 21 may be arranged in a matrix.

[0189] The second terahertz elements 22 in the second region RB may be arranged at intervals in both the X direction and the Y direction. That is, the second terahertz elements 22 may be arranged in a matrix.

[0190] In the second embodiment, the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, the plurality of third terahertz elements 23, and the plurality of fourth terahertz elements 24 were arranged at a distance from each other in the X direction (first direction), but this is not limited to this.

[0191] In one example, the plurality of first terahertz elements 21, the plurality of second terahertz elements 22, the plurality of third terahertz elements 23, and the plurality of fourth terahertz elements 24 may be arranged spaced apart from one another in the Y direction (second direction). That is, the plurality of first terahertz elements 21 may be arranged side by side in the Y direction. The plurality of second terahertz elements 22 may be arranged side by side in the Y direction. The plurality of third terahertz elements 23 may be arranged side by side in the Y direction. The plurality of fourth terahertz elements 24 may be arranged side by side in the Y direction. The plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be arranged adjacent to each other in the X direction (first direction). The plurality of third terahertz elements 23 may be arranged adjacent to the plurality of second terahertz elements 22 on the opposite side of the plurality of first terahertz elements 21 in the X direction. The plurality of fourth terahertz elements 24 may be arranged adjacent to the plurality of third terahertz elements 23 on the opposite side to the plurality of second terahertz elements 22 in the X direction.

[0192] In each embodiment, a waveguide may be provided in each of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22. The waveguide is, for example, a rectangular parallelepiped having a through-hole penetrating in the Z direction. In one example, the waveguides provided in adjacent terahertz elements of the plurality of first terahertz elements 21 and the plurality of second terahertz elements 22 may be arranged so as to be in contact with each other.

[0193] In each embodiment, the orientation of each of the first terahertz elements 21 and the second terahertz elements 22 is constant, but this is not limiting. At least one of the first terahertz elements 21 and the second terahertz elements 22 may be arranged in an orientation different from that of the other terahertz elements.

[0194] One or more of the various examples described in this disclosure can be combined to the extent that they are not technically inconsistent. The term "on" used in this disclosure includes the meanings of "on" and "above," unless the context clearly indicates otherwise. Thus, for example, the expression "a first element is disposed on a second element" means that in some embodiments, the first element may be in contact with the second element and disposed directly on the second element, but in other embodiments, the first element may be disposed above the second element without contacting the second element. In other words, the term "on" does not exclude a structure in which another element is formed between the first element and the second element.

[0195] The Z direction used in this disclosure does not necessarily have to be the vertical direction, nor does it have to completely coincide with the vertical direction. Therefore, various structures according to this disclosure are not limited to the "up" and "down" in the Z axis direction described in this disclosure being "up" and "down" in the vertical direction. For example, the X direction may be the vertical direction, or the Y direction may be the vertical direction.

[0196] <Supplementary Notes> The technical ideas that can be understood from this disclosure are described below. Note that, for the purpose of aiding understanding and not intending to be limiting, the components described in the supplementary notes are given the reference numerals of the corresponding components in the above embodiment. The reference numerals are shown as examples to aid understanding, and the components described in each supplementary note should not be limited to the components indicated by the reference numerals.

[0197] [Supplementary Note 1] A terahertz system (10) including: a plurality of first terahertz elements (21) that oscillate and detect terahertz waves (W); a plurality of second terahertz elements (22) that oscillate and detect terahertz waves (W); and a control device (30) configured to switch between a first state in which the plurality of first terahertz elements (21) oscillate terahertz waves (W) and the plurality of second terahertz elements (22) detect the terahertz waves (W), and a second state in which the plurality of second terahertz elements (22) oscillate terahertz waves (W) and the first terahertz elements (21) detect the terahertz waves (W).

[0198] [Supplementary Note 2] The terahertz system according to Supplementary Note 1, wherein the control device (30) includes a power supply control circuit (31) configured to output an oscillation drive signal (S1) that operates the device to oscillate the terahertz waves (W) and a detection drive signal (S2) that operates the device to detect the terahertz waves (W), and the power supply control circuit (31) is configured to alternately apply the oscillation drive signal (S1) and the detection drive signal (S2) to the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22).

[0199] [Supplementary Note 3] The terahertz system according to Supplementary Note 2, wherein the control device (30) includes an oscillation signal generation circuit (32) configured to generate the oscillation drive signal (S1), and the oscillation signal generation circuit (32) includes: an oscillation bias circuit (32B) configured to generate a DC oscillation bias voltage (VB1); a modulation circuit (32A) configured to generate a modulation signal at a modulation frequency; and a superposition circuit (33C) configured to generate the oscillation drive signal (S1) by superimposing the modulation signal on the oscillation bias voltage (VB1).

[0200] [Supplementary Note 4] The terahertz system according to Supplementary Note 3, wherein the control device (30) includes a detection signal generation circuit (33) configured to generate the detection drive signal (S2), the detection signal generation circuit (33) includes a detection bias circuit (33A) configured to generate a DC detection bias voltage (VB2), and the oscillation bias voltage (VB1) and the detection bias voltage (VB2) are different from each other.

[0201] [Supplementary Note 5] The terahertz system according to any one of Supplementary Notes 1 to 4, wherein the control device (30) includes a signal processing circuit (34) configured to process analog signals output from the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) into digital signals.

[0202] [Supplementary Note 6] The terahertz system according to Supplementary Note 5, wherein the control device (30) includes a selection circuit (35) electrically connected to the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), and the signal processing circuit (34), and the selection circuit (35) is configured to selectively output a first detection signal (SR1) detected by the plurality of first terahertz elements (21) and a second detection signal (SR2) detected by the plurality of second terahertz elements (22) to the signal processing circuit (34).

[0203] [Supplementary Note 7] The terahertz system according to Supplementary Note 6, wherein the selection circuit (35) includes analog switches (35A / 35AA to 35AD) electrically connected to the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22), wherein a plurality of the analog switches (35A / 35AA to 35AD) are provided corresponding to the number of combinations of the first terahertz elements (21) and the second terahertz elements (22), and wherein the control device (30) is configured to individually control the plurality of analog switches (35A / 35AA to 35AD).

[0204] [Supplementary Note 8] The terahertz system according to Supplementary Note 6 or 7, wherein the signal processing circuit (34) is configured to convert frequency information of the first detection signals (SR1) of the plurality of first terahertz elements (21) into information corresponding to the terahertz waves of the first terahertz elements (21), and to convert frequency information of the second detection signals (SR2) of the plurality of second terahertz elements (22) into information corresponding to the terahertz waves of the second terahertz elements (22).

[0205] [Supplementary Note 9] The terahertz system according to any one of Supplementary Notes 6 to 8, wherein the signal processing circuit (34) includes: a sample-and-hold circuit (34A) configured to sample and hold the first detection signal (SR1) and the second detection signal (SR2); a noise reduction circuit (34B) configured to reduce noise in the first detection signal (SR1) and the second detection signal (SR2); a signal amplification circuit (34C) configured to amplify the amplitudes of the first detection signal (SR1) and the second detection signal (SR2); and an analog-to-digital conversion circuit (34D) configured to convert the first detection signal (SR1) and the second detection signal (SR2) into digital signals.

[0206] [Supplementary Note 10] The terahertz system according to Supplementary Note 4, wherein the control device (30) includes a timing generation circuit (36) configured to switch between the first state and the second state at predetermined intervals.

[0207] [Supplementary Note 11] The terahertz system according to Supplementary Note 10, wherein the predetermined period is longer than the period of the modulation signal modulated by the modulation circuit (33).

[0208] [Supplementary Note 12] The terahertz system according to any one of Supplementary Notes 1 to 11, wherein the plurality of first terahertz elements (21) are arranged at intervals in a first direction (X), the plurality of second terahertz elements (22) are arranged at intervals in the first direction (X), and the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) are arranged at intervals in a second direction (Y) perpendicular to the first direction (X).

[0209] [Supplementary Note 13] The terahertz system according to any one of Supplementary Notes 1 to 12, wherein the plurality of first terahertz elements (21) include a first terahertz element (21P) configured to be capable of oscillation and detection at a first oscillation frequency (F1), and a first terahertz element (21Q) configured to be capable of oscillation and detection at a second oscillation frequency (F2) different from the first oscillation frequency (F1), and the plurality of second terahertz elements (22) include a second terahertz element (22P) configured to be capable of oscillation and detection at the first oscillation frequency (F1), and a second terahertz element (22Q) configured to be capable of oscillation and detection at the second oscillation frequency (F2).

[0210] [Supplementary Note 14] The terahertz system according to any one of Supplementary Notes 1 to 13, wherein the number of the first terahertz elements (21) and the number of the second terahertz elements (22) are equal to each other.

[0211] [Supplementary Note 15] The terahertz system according to any one of Supplementary Notes 1 to 13, wherein the number of the first terahertz elements (21) and the number of the second terahertz elements (22) are different from each other.

[0212] [Supplementary Note 16] The terahertz system according to any one of Supplementary Notes 1 to 15, wherein the plurality of first terahertz elements (21) include first terminals (43, 44) that serve as output terminals in the first state and as input terminals in the second state, and the plurality of second terahertz elements (22) include second terminals (43, 44) that serve as input terminals in the first state and as output terminals in the second state.

[0213] [Supplementary Note 17] The terahertz system according to any one of Supplementary Notes 1 to 16, wherein each of the first terahertz element (21) and the second terahertz element (22) includes a resonant tunneling diode.

[0214] [Supplementary Note 18] A plurality of first terahertz elements (21) that oscillate and detect terahertz waves (W); a plurality of second terahertz elements (22) that oscillate and detect terahertz waves (W); a plurality of third terahertz elements (23) that oscillate and detect terahertz waves (W); and a plurality of fourth terahertz elements (24) that oscillate and detect terahertz waves (W). a first state in which the plurality of first terahertz elements (21) oscillate terahertz waves (W), and the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) detect the terahertz waves (W); a second state in which the plurality of second terahertz elements (22) oscillate terahertz waves (W), and the plurality of first terahertz elements (21), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) detect the terahertz waves (W); a control device (30) configured to switch between a third state in which an element (23) oscillates terahertz waves (W), and the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), and the plurality of fourth terahertz elements (24) detect the terahertz waves (W), and a fourth state in which the plurality of fourth terahertz elements (24) oscillates terahertz waves (W), and the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), and the plurality of third terahertz elements (23) detect the terahertz waves (W).

[0215] [Supplementary Note 19] The plurality of first terahertz elements (21) are arranged at intervals in a first direction (X), The plurality of second terahertz elements (22) are arranged at intervals in the first direction (X), The plurality of third terahertz elements (23) are arranged at intervals in the first direction (X), The plurality of fourth terahertz elements (24) are arranged at intervals in the first direction (X), The plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) are arranged so as to be adjacent to each other in a second direction (Y) perpendicular to the first direction (X), The plurality of third terahertz elements (23) are arranged so as to be adjacent to each other on the opposite side of the plurality of first terahertz elements (21) with respect to the plurality of second terahertz elements (22) in the second direction (Y), The terahertz system described in Appendix 18, wherein the plurality of fourth terahertz elements (24) are arranged adjacent to the plurality of third terahertz elements (23) on the opposite side of the plurality of second terahertz elements (22) in the second direction (Y).

[0216] [Supplementary Note 20] The plurality of first terahertz elements (21) include a first terahertz element (21P) configured to be capable of oscillation and detection at a first oscillation frequency (F1), and a first terahertz element (21Q) configured to be capable of oscillation and detection at a second oscillation frequency (F2) different from the first oscillation frequency (F1); the plurality of second terahertz elements (22) include a second terahertz element (22P) configured to be capable of oscillation and detection at the first oscillation frequency (F1), and a second terahertz element (22Q) configured to be capable of oscillation and detection at the second oscillation frequency (F2); and the plurality of third terahertz elements (23) include a third terahertz element (23P) configured to be capable of oscillation and detection at the first oscillation frequency (F1), and a third terahertz element (23Q) configured to be capable of oscillation and detection at the second oscillation frequency (F2); The terahertz system described in Appendix 18 or 19, wherein the plurality of fourth terahertz elements (24) include a fourth terahertz element (24P) configured to be capable of oscillating and detecting at the first oscillation frequency (F1) and a fourth terahertz element (24Q) configured to be capable of oscillating and detecting at the second oscillation frequency (F2).

[0217] [Supplementary Note 21] The terahertz system according to any one of Supplementary Notes 1 to 11, wherein the first terahertz element (21) is configured to be capable of oscillating and detecting a first terahertz wave (W1) having a first oscillation frequency (F1), and the second terahertz element (22) is configured to be capable of oscillating and detecting a second terahertz wave (W2) having a second oscillation frequency (F2) different from the first oscillation frequency (F1).

[0218] [Supplementary Note 22] The terahertz system according to any one of Supplementary Notes 1 to 11, wherein the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) are arranged alternately one by one in a first direction (X).

[0219] [Supplementary Note 23] The terahertz system according to any one of Supplementary Notes 1 to 11, wherein the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) are arranged alternately one by one in a first direction (X) and are arranged alternately one by one in a second direction (Y) perpendicular to the first direction (X).

[0220] [Supplementary Note 24] The terahertz system according to any one of Supplementary Notes 1 to 11, wherein the plurality of first terahertz elements (21) are arranged in a first region (RA), and the plurality of second terahertz elements (22) are arranged in a second region (RB) adjacent to the first region (RA).

[0221] [Supplementary Note 25] The terahertz system according to Supplementary Note 24, wherein the plurality of first terahertz elements (21) are arranged in the first region (RA) at a distance from each other in both a first direction (X) and a second direction (Y) perpendicular to the first direction (X), and the plurality of second terahertz elements (22) are arranged in the second region (RB) at a distance from each other in both the first direction (X) and the second direction (Y).

[0222] [Supplementary Note 26] The terahertz system according to Supplementary Note 1, wherein the control device (30) includes: a power supply control circuit (31) configured to output an oscillation drive signal (S1) that operates to oscillate the terahertz waves (W) and a detection drive signal (S2) that operates to detect the terahertz waves (W); a signal processing circuit (34) that processes signals output from the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) into digital signals; a selection circuit (35) that is electrically connected to the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) and the signal processing circuit (34), and configured to selectively output signals from the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) to the signal processing circuit (34); and a timing generation circuit (36) configured to control the power supply control circuit (31) and the selection circuit (35).

[0223] [Supplementary Note 27] The terahertz system according to Supplementary Note 26, wherein the selection circuit (35) includes analog switches (35A / 35AA to 35AD) electrically connected to both the first terahertz element (21) and the second terahertz element (22), a plurality of the analog switches (35A / 35AA to 35AD) are provided corresponding to the number of combinations of the first terahertz elements (21) and the second terahertz elements (22), and the control device (30) is configured to output a signal for switching between the first state and the second state to the power supply control circuit (31) and each of the plurality of analog switches (35A / 35AA to 35AD).

[0224] [Supplementary Note 28] The present invention further includes a plurality of third terahertz elements (23) that oscillate and detect terahertz waves (W), The terahertz system according to any one of appendices 1 to 17, wherein the control device (30) is configured to switch between a first state in which the plurality of first terahertz elements (21) oscillate terahertz waves (W), and the plurality of second terahertz elements (22) and the plurality of third terahertz elements (23) detect the terahertz waves (W), a second state in which the plurality of second terahertz elements (22) oscillate terahertz waves (W), and the plurality of first terahertz elements (21) and the plurality of third terahertz elements (23) detect the terahertz waves (W), and a third state in which the plurality of third terahertz elements (23) oscillate terahertz waves (W), and the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) detect the terahertz waves (W).

[0225] [Supplementary Note 29] A terahertz system including: a plurality of first oscillation terahertz elements (111P) configured to oscillate a first terahertz wave (W1); and a plurality of second oscillation terahertz elements (111Q) configured to oscillate a second terahertz wave (W2) having an oscillation frequency different from the oscillation frequency of the first terahertz wave (W1), wherein the plurality of first oscillation terahertz elements (111P) and the plurality of second oscillation terahertz elements (111Q) are arranged adjacent to each other.

[0226] [Supplementary Note 30] The terahertz system according to Supplementary Note 29, wherein the plurality of first oscillation terahertz elements (111P) and the plurality of second oscillation terahertz elements (111Q) are arranged alternately one by one in a first direction (X).

[0227] [Supplementary Note 31] The terahertz system according to Supplementary Note 29, wherein the plurality of first oscillation terahertz elements (111P) are arranged side by side in a first direction (X), the plurality of second oscillation terahertz elements (111Q) are arranged side by side in the first direction (X), and the plurality of first oscillation terahertz elements (111P) and the plurality of second oscillation terahertz elements (111Q) are arranged side by side in a second direction (Y) perpendicular to the first direction (X).

[0228] [Supplementary Note 32] The terahertz system according to Supplementary Note 29, wherein the plurality of first oscillation terahertz elements (111P) and the plurality of second oscillation terahertz elements (111Q) are arranged alternately one by one in a first direction (X) and are arranged alternately one by one in a second direction (Y) perpendicular to the first direction (X).

[0229] [Supplementary Note 33] The terahertz system according to any one of Supplementary Notes 29 to 32, wherein the number of the first oscillation terahertz elements (111P) is equal to the number of the second oscillation terahertz elements (111Q).

[0230] [Supplementary Note 34] The terahertz system according to any one of Supplementary Notes 29 to 32, wherein the number of the first oscillation terahertz elements (111P) is different from the number of the second oscillation terahertz elements (111Q).

[0231] [Supplementary Note 35] The terahertz system according to any one of Supplementary Notes 29 to 34, including: a plurality of first detection terahertz elements (121P) configured to detect a first terahertz wave (W1); and a plurality of second detection terahertz elements (121Q) configured to detect the second terahertz wave (W2), wherein the plurality of first detection terahertz elements (121P) and the plurality of second detection terahertz elements (121Q) are arranged adjacent to each other.

[0232] [Supplementary Note 36] The terahertz system according to Supplementary Note 35, wherein the plurality of first oscillation terahertz elements (111P) and the plurality of second oscillation terahertz elements (111Q) are arranged opposite to the plurality of first detection terahertz elements (121P) and the plurality of second detection terahertz elements (121Q).

[0233] [Supplementary Note 37] A plurality of first terahertz elements (21) that oscillate and detect terahertz waves (W); a plurality of second terahertz elements (22) that oscillate and detect terahertz waves (W); a plurality of third terahertz elements (23) that oscillate and detect terahertz waves (W); and a plurality of fourth terahertz elements (24) that oscillate and detect terahertz waves (W). a control device (30) configured to individually control the oscillation states and detection states of the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) so ​​that two types of terahertz elements among the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) oscillate terahertz waves (W) and the remaining two types of terahertz elements detect the terahertz waves (W).

[0234] [Supplementary Note 38] The plurality of first terahertz elements (21) are arranged at intervals in a first direction (X), The plurality of second terahertz elements (22) are arranged at intervals in the first direction (X), The plurality of third terahertz elements (23) are arranged at intervals in the first direction (X), The plurality of fourth terahertz elements (24) are arranged at intervals in the first direction (X), The plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) are arranged so as to be adjacent to each other in a second direction (Y) perpendicular to the first direction (X), The plurality of third terahertz elements (23) are arranged so as to be adjacent to each other on the opposite side of the plurality of first terahertz elements (21) with respect to the plurality of second terahertz elements (22) in the second direction (Y), The terahertz system described in Appendix 37, wherein the plurality of fourth terahertz elements (24) are arranged adjacent to the plurality of third terahertz elements (23) on the opposite side of the plurality of second terahertz elements (22) in the second direction (Y).

[0235] [Supplementary Note 39] The terahertz system according to Supplementary Note 37 or 38, wherein the control device (30) is configured to switch between a first state in which the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) oscillate terahertz waves (W), and the plurality of third terahertz elements (23) and the plurality of fourth terahertz elements (24) detect the terahertz waves (W), and a second state in which the plurality of third terahertz elements (23) and the plurality of fourth terahertz elements (24) oscillate terahertz waves (W), and the plurality of first terahertz elements (21) and the plurality of second terahertz elements (22) detect the terahertz waves (W).

[0236] [Supplementary Note 40] The terahertz system according to Supplementary Note 37 or 38, wherein the control device (30) is configured to switch between a first state in which the plurality of first terahertz elements (21) and the plurality of fourth terahertz elements (24) oscillate terahertz waves (W), and the plurality of second terahertz elements (22) and the plurality of third terahertz elements (23) detect the terahertz waves (W), and a second state in which the plurality of second terahertz elements (22) and the plurality of third terahertz elements (23) oscillate terahertz waves (W), and the plurality of first terahertz elements (21) and the plurality of fourth terahertz elements (24) detect the terahertz waves (W).

[0237] [Supplementary Note 41] The terahertz system according to any one of Supplementary Notes 37 to 40, wherein the first terahertz element (21) and the third terahertz element (23) are configured to oscillate and detect, as the terahertz waves (W), first terahertz waves (W1) having a first oscillation frequency (F1), and the second terahertz element (22) and the fourth terahertz element (24) are configured to oscillate and detect, as the terahertz waves (W), second terahertz waves (W2) having a second oscillation frequency (F2) different from the first oscillation frequency (F1).

[0238] [Supplementary Note 42] A terahertz system (10) including: a plurality of first terahertz elements (21P, 21Q) that oscillate terahertz waves (W); and a plurality of second terahertz elements (22P, 22Q) that oscillate terahertz waves (W), wherein the plurality of first terahertz elements (21P, 21Q) and the plurality of second terahertz elements (22P, 22Q) have the same structure; and a control device (30) configured to apply a first oscillation bias voltage (VB11) to the plurality of first terahertz elements (21P, 21Q) and to apply a second oscillation bias voltage (VB12) different from the first bias voltage (VB11) to the plurality of second terahertz elements (22P, 22Q).

[0239] [Supplementary Note 43] The terahertz system according to Supplementary Note 42, wherein the plurality of first terahertz elements (21P, 21Q) and the plurality of second terahertz elements (22P, 22Q) oscillate first terahertz waves (W1) of a first oscillation frequency (F1) as the terahertz waves (W) when the first oscillation bias voltage (VB11) is applied, and oscillate second terahertz waves (W2) of a second oscillation frequency (F2) as the terahertz waves (W) when the second oscillation bias voltage (VB12) is applied, and the plurality of first terahertz elements (21P, 21Q) and the plurality of second terahertz elements (22P, 22Q) are capable of detecting the second terahertz waves (W2) when a first detection bias voltage (VB21) is applied, and are capable of detecting the first terahertz waves (W1) when a second detection bias voltage (VB22) is applied.

[0240] [Supplementary Note 44] The terahertz system according to Supplementary Note 43, wherein the control device (30) is configured to switch between a first state in which the plurality of first terahertz elements (21P, 21Q) oscillate the first terahertz wave (W1) and the plurality of second terahertz elements (22P, 22Q) detect the first terahertz wave (W1), and a second state in which the plurality of second terahertz elements (22P, 22Q) oscillate the second terahertz wave (W2) and the first terahertz elements (21P, 21Q) detect the second terahertz wave (W2).

[0241] [Supplementary Note 45] A terahertz wave detector includes: a plurality of first terahertz elements (21) that oscillate and detect terahertz waves (W); a plurality of second terahertz elements (22) that oscillate and detect terahertz waves (W); a plurality of third terahertz elements (23) that oscillate and detect terahertz waves (W); and a plurality of fourth terahertz elements (24) that oscillate and detect terahertz waves (W), wherein the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) have the same structure as one another, A terahertz system (10) including a control device (30) configured to apply different oscillation bias voltages (VB1) to the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24).

[0242] [Supplementary Note 46] The plurality of first terahertz elements (21), the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) oscillate a first terahertz wave (W1) of a first oscillation frequency (F1) as the terahertz wave (W) by applying a first oscillation bias voltage (VB11) as the oscillation bias voltage (VB1), and oscillate the first terahertz wave (W1) of a first oscillation frequency (F1) as the terahertz wave (W) by applying a second oscillation bias voltage (VB12) as the oscillation bias voltage (VB1). a third oscillation bias voltage (VB13) is applied as the oscillation bias voltage (VB1) to oscillate a third terahertz wave (W3) having a third oscillation frequency (F3) as the terahertz wave (W); a fourth oscillation bias voltage (VB14) is applied as the oscillation bias voltage (VB1) to oscillate a fourth terahertz wave (W4) having a fourth oscillation frequency (F4) as the terahertz wave (W); the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) are capable of detecting the first terahertz wave (W1) by applying a first detection bias voltage (VB21), are capable of detecting the second terahertz wave (W2) by applying a second detection bias voltage (VB22), are capable of detecting the third terahertz wave (W3) by applying a third detection bias voltage (VB23), and are capable of detecting the fourth terahertz wave (W4) by applying a fourth detection bias voltage (VB24); the first oscillation bias voltage (VB11), the second oscillation bias voltage (VB12), the third oscillation bias voltage (VB13), and the fourth oscillation bias voltage (VB14) are different from one another; The terahertz system according to claim 45, wherein the first detection bias voltage (VB21), the second detection bias voltage (VB22), the third detection bias voltage (VB23), and the fourth detection bias voltage (VB24) are different from each other.

[0243] [Supplementary Note 47] The control device (30) is configured to have a first state in which the plurality of first terahertz elements (21) oscillate the first terahertz wave (W1), and the plurality of second terahertz elements (22), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) detect the first terahertz wave (W1); and a second state in which the plurality of second terahertz elements (22) oscillate the second terahertz wave (W2), and the plurality of first terahertz elements (21), the plurality of third terahertz elements (23), and the plurality of fourth terahertz elements (24) detect the second terahertz wave (W2); The terahertz system (10) according to Appendix 46 is configured to switch between a third state in which the plurality of third terahertz elements (23) oscillate the third terahertz waves (W3), and the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), and the plurality of fourth terahertz elements (24) detect the third terahertz waves (W3), and a fourth state in which the plurality of fourth terahertz elements (24) oscillate the fourth terahertz waves (W4), and the plurality of first terahertz elements (21), the plurality of second terahertz elements (22), and the plurality of third terahertz elements (23) detect the fourth terahertz waves (W4).

[0244] The above description is merely illustrative. Those skilled in the art will recognize that many more possible combinations and permutations are possible other than the components and methods (manufacturing processes) listed for the purpose of illustrating the technology of the present disclosure. The present disclosure is intended to embrace all alternatives, modifications, and variations that fall within the scope of the present disclosure, including the claims.

[0245] 10... Terahertz system, 20... Terahertz device, 21, 21A to 21D, 21P, 21Q... First terahertz element, 22, 22A to 22D, 22P, 22Q... Second terahertz element, 23, 23P, 23Q... Third terahertz element, 24, 24P, 24Q... Fourth terahertz element, 25... Substrate, 25S... First substrate surface, 30... Control device, 31... Power supply control circuit, 31A... Noise reduction circuit, 31B... Current amplification circuit, 31C...current amplifier circuit, 31D...noise reduction circuit, 31E...analog switch, 32...oscillation signal generation circuit, 32A...modulation circuit, 32B...oscillation bias circuit, 32C...superposition circuit, 33...detection signal generation circuit, 33A...detection bias circuit, 34...signal processing circuit, 34A...sample and hold circuit, 34B...noise reduction circuit, 34C...signal amplifier circuit, 34D...analog-to-digital conversion circuit, 35...selection circuit, 35A,35AA to 35AD...analog switches, 36...timing generation circuit, 41...semiconductor substrate, 41S...first substrate surface, 42...active element, 43...first electrode, 43A...antenna portion, 43B...feeder portion, 43C...pad electrode portion, 44...second electrode, 44A...antenna portion, 44B...feeder portion, 44C...pad electrode portion, 45...insulating layer, 51A...InGaAs layer, 51B...InGaAs layer, 52A...In GaAs layer, 52B...InGaAs layer, 53A...InGaAs layer, 53B...InGaAs layer, 54A...AlAs layer, 54B...AlAs layer, 55...InGaAs layer, 100...detection object, 110...first terahertz device, 111...oscillating terahertz element, 111P...first oscillating terahertz element, 111Q...second oscillating terahertz element, 120...second terahertz device, 121...detecting terahertz element element, 121P...first terahertz detection element, 121Q...second terahertz detection element, 130...control device, W...terahertz wave, W1...first terahertz wave, W2...second terahertz wave, V1...oscillation drive voltage, V2...detection drive voltage, VB1...oscillation bias voltage, VB2...detection bias voltage, VG...drive voltage when off, RX...negative resistance region, R1...oscillation region, R2...detection region, RA...first region, RB... Second region, S1...oscillation drive signal, S2...detection drive signal, S11...first drive signal, S12...second drive signal, SR1...first detection signal, SR2...second detection signal, CS1...first timing signal, CS2...second timing signal, F1...first oscillation frequency, F2...second oscillation frequency, T1...first period, T2...second period, T3...third period, T4...fourth period, TP...oscillation portion, TQ...detection portion, TR...stop portion.

Claims

1. A terahertz system comprising: a plurality of first terahertz elements that emit and detect terahertz waves; a plurality of second terahertz elements that emit and detect terahertz waves; and a control device configured to switch between a first state in which the plurality of first terahertz elements emit terahertz waves and the plurality of second terahertz elements detect the terahertz waves, and a second state in which the plurality of second terahertz elements emit terahertz waves and the first terahertz elements detect the terahertz waves.

2. The terahertz system of claim 1, wherein the control device includes a power supply control circuit configured to output an oscillation drive signal that operates the device to oscillate the terahertz waves and a detection drive signal that operates the device to detect the terahertz waves, and the power supply control circuit is configured to alternately apply the oscillation drive signal and the detection drive signal to the plurality of first terahertz elements and the plurality of second terahertz elements.

3. The terahertz system according to claim 2, wherein the control device includes an oscillation signal generation circuit configured to generate the oscillation drive signal, and the oscillation signal generation circuit includes: an oscillation bias circuit configured to generate a DC oscillation bias voltage; a modulation circuit configured to generate a modulation signal at a modulation frequency; and a superposition circuit configured to generate the oscillation drive signal by superimposing the modulation signal on the oscillation bias voltage.

4. The terahertz system according to claim 3, wherein the control device includes a detection signal generation circuit configured to generate the detection drive signal, the detection signal generation circuit includes a detection bias circuit configured to generate a DC detection bias voltage, and the oscillation bias voltage and the detection bias voltage are different from each other.

5. A terahertz system according to any one of claims 1 to 4, wherein the control device includes a signal processing circuit configured to process analog signals output from the plurality of first terahertz elements and the plurality of second terahertz elements into digital signals.

6. The terahertz system according to claim 5, wherein the control device includes a selection circuit electrically connected to the plurality of first terahertz elements, the plurality of second terahertz elements, and the signal processing circuit, and the selection circuit is configured to selectively output a first detection signal detected by the plurality of first terahertz elements and a second detection signal detected by the plurality of second terahertz elements to the signal processing circuit.

7. The terahertz system according to claim 6, wherein the selection circuit includes an analog switch electrically connected to the plurality of first terahertz elements and the plurality of second terahertz elements, a plurality of the analog switches are provided corresponding to the number of combinations of the first terahertz elements and the second terahertz elements, and the control device is configured to individually control the plurality of analog switches.

8. The terahertz system according to claim 6 or 7, wherein the signal processing circuit is configured to convert frequency information of the first detection signals of the plurality of first terahertz elements into information corresponding to the terahertz waves of the first terahertz elements, and to convert frequency information of the second detection signals of the plurality of second terahertz elements into information corresponding to the terahertz waves of the second terahertz elements.

9. A terahertz system according to any one of claims 6 to 8, wherein the signal processing circuit includes: a sample-and-hold circuit configured to sample and hold the first detection signal and the second detection signal; a noise reduction circuit configured to reduce noise in the first detection signal and the second detection signal; a signal amplification circuit configured to amplify the amplitude of the first detection signal and the second detection signal; and an analog-to-digital conversion circuit configured to convert the first detection signal and the second detection signal into a digital signal.

10. The terahertz system according to claim 4, wherein the control device includes a timing generation circuit configured to switch between the first state and the second state at predetermined intervals.

11. The terahertz system according to claim 10, wherein the predetermined period is longer than the period of the signal modulated by the modulation circuit.

12. A terahertz system according to any one of claims 1 to 11, wherein the plurality of first terahertz elements are arranged at intervals in a first direction, the plurality of second terahertz elements are arranged at intervals in the first direction, and the plurality of first terahertz elements and the plurality of second terahertz elements are arranged at intervals in a second direction perpendicular to the first direction.

13. A terahertz system according to any one of claims 1 to 12, wherein the plurality of first terahertz elements include a first terahertz element configured to be capable of oscillating and detecting at a first oscillation frequency, and a first terahertz element configured to be capable of oscillating and detecting at a second oscillation frequency different from the first oscillation frequency, and the plurality of second terahertz elements include a second terahertz element configured to be capable of oscillating and detecting at the first oscillation frequency, and a second terahertz element configured to be capable of oscillating and detecting at the second oscillation frequency.

14. A terahertz system according to any one of claims 1 to 13, wherein the number of the first terahertz elements and the number of the second terahertz elements are equal to each other.

15. A terahertz system according to any one of claims 1 to 13, wherein the number of the first terahertz elements and the number of the second terahertz elements are different from each other.

16. The terahertz system according to claim 1, wherein the plurality of first terahertz elements include first terminals that serve as output terminals in the first state and as input terminals in the second state, and the plurality of second terahertz elements include second terminals that serve as input terminals in the first state and as output terminals in the second state.

17. A terahertz system according to any one of claims 1 to 16, wherein each of the first terahertz element and the second terahertz element includes a resonant tunneling diode.

18. A plurality of first terahertz elements that oscillate and detect terahertz waves; a plurality of second terahertz elements that oscillate and detect terahertz waves; a plurality of third terahertz elements that oscillate and detect terahertz waves; and a plurality of fourth terahertz elements that oscillate and detect terahertz waves. a control device configured to switch between a first state in which the plurality of first terahertz elements oscillate terahertz waves and the plurality of second terahertz elements, the plurality of third terahertz elements, and the plurality of fourth terahertz elements detect the terahertz waves; a second state in which the plurality of second terahertz elements oscillate terahertz waves and the plurality of first terahertz elements, the plurality of third terahertz elements, and the plurality of fourth terahertz elements detect the terahertz waves; a third state in which the plurality of third terahertz elements oscillate terahertz waves and the plurality of first terahertz elements, the plurality of second terahertz elements, and the plurality of fourth terahertz elements detect the terahertz waves; and a fourth state in which the plurality of fourth terahertz elements oscillate terahertz waves and the plurality of first terahertz elements, the plurality of second terahertz elements, and the plurality of third terahertz elements detect the terahertz waves.

19. The terahertz system of claim 18, wherein the plurality of first terahertz elements are arranged at intervals in a first direction, the plurality of second terahertz elements are arranged at intervals in the first direction, the plurality of third terahertz elements are arranged at intervals in the first direction, the plurality of fourth terahertz elements are arranged at intervals in the first direction, the plurality of first terahertz elements and the plurality of second terahertz elements are arranged adjacent to each other in a second direction perpendicular to the first direction, the plurality of third terahertz elements are arranged adjacent to each other on the opposite side of the plurality of first terahertz elements relative to the plurality of second terahertz elements in the second direction, and the plurality of fourth terahertz elements are arranged adjacent to each other on the opposite side of the plurality of second terahertz elements relative to the plurality of third terahertz elements in the second direction.

20. The terahertz system according to claim 18 or 19, wherein the plurality of first terahertz elements include a first terahertz element configured to be capable of oscillating and detecting at a first oscillation frequency, and a first terahertz element configured to be capable of oscillating and detecting at a second oscillation frequency different from the first oscillation frequency; the plurality of second terahertz elements include a second terahertz element configured to be capable of oscillating and detecting at the first oscillation frequency, and a second terahertz element configured to be capable of oscillating and detecting at the second oscillation frequency; the plurality of third terahertz elements include a third terahertz element configured to be capable of oscillating and detecting at the first oscillation frequency, and a third terahertz element configured to be capable of oscillating and detecting at the second oscillation frequency; and the plurality of fourth terahertz elements include a fourth terahertz element configured to be capable of oscillating and detecting at the first oscillation frequency, and a fourth terahertz element configured to be capable of oscillating and detecting at the second oscillation frequency.

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