Terahertz receiver based on variable capacitance and focal plane camera device thereof

Abstract

This invention discloses a terahertz receiver and a focal plane camera device based on a variable capacitor. The receiver includes a connected zigzag inductor and interdigitated capacitors; each finger of the interdigitated capacitor is composed of closely arranged double-cross-shaped repeating units, enabling it to efficiently absorb terahertz waves without the need for an additional absorber. Terahertz radiation changes the dielectric constant of the dielectric, causing changes in capacitance and resonant frequency; detection is achieved by detecting these changes. The focal plane camera device includes an array of the aforementioned receivers. Each receiver is coupled to a zigzag-shaped center feed line via a coupling feed line, and each unit has a different resonant frequency, achieving frequency division multiplexing readout. This invention combines absorption and resonance functions into one, greatly simplifying the structure, achieving high absorption efficiency, possessing dual polarization and intrinsic frequency division multiplexing capabilities, and easily expanding into large arrays. It can be widely applied in fields such as high-sensitivity terahertz passive imaging and spectral analysis.

Description

Technical Field

[0001] This invention relates to terahertz detection technology, specifically to a terahertz receiver based on a variable capacitor and its focal plane camera device. Background Technology

[0002] Terahertz waves typically refer to electromagnetic waves with frequencies ranging from 0.1 THz to 10 THz, with a spectrum between microwaves and the infrared band. Terahertz waves possess a certain degree of penetrability through dry, nonpolar materials, exhibit characteristic absorption lines in biological macromolecules, and are non-ionizing. Furthermore, the cosmic microwave background radiation contains abundant terahertz spectral information, demonstrating significant application potential in fields such as security imaging, biomedical detection, national defense, and space astronomical observation. Therefore, achieving high-sensitivity, high-performance terahertz detection is the core key to driving the development of these applications.

[0003] In the pursuit of high-sensitivity terahertz detection technology, several common technical challenges remain to be overcome. First, the physical size of the detector pixel is often limited by the area of ​​its core resonant or absorbing structure, restricting the improvement of the spatial resolution of the focal plane array. Second, in extremely low-temperature operating environments, low-frequency noise introduced by dielectric dipole fluctuations in the device substrate or dielectric layer degrades the final signal-to-noise ratio and sensitivity of the detection system. Furthermore, independent terahertz wave absorbers and electrical resonant structures are typically designed separately, increasing the structural complexity and fabrication integration difficulty of the device, which is detrimental to achieving large-scale pixel arrays with high fill factor and high integration, as well as efficient readout. Therefore, developing a new terahertz detection mechanism and structure that can balance high spatial resolution, high sensitivity, and high integration is an urgent problem to be solved in this field. Summary of the Invention

[0004] Purpose of the invention: The purpose of this invention is to provide a terahertz receiver based on a variable capacitor with a simplified structure, high absorption efficiency, high fill factor, and intrinsic frequency division multiplexing readout capability, as well as its focal plane camera device, to solve the technical problems of complex structure, low integration, and limited spatial resolution caused by the separate design of absorber and resonator in existing terahertz detectors.

[0005] Technical solution: The terahertz receiver based on variable capacitor of the present invention includes a connected zigzag inductor, interdigitated capacitors, and a coupling feed line. Each finger of the interdigitated capacitor is composed of closely arranged double cross-shaped finger repeating units. The finger repeating unit is composed of a central rectangular capacitor structure and parallel plate capacitor structures on both sides symmetrical about the center of the rectangle. The zigzag inductor is connected to the interdigitated capacitor to form a resonant circuit. The coupling feed line is located outside the interdigitated capacitor and is connected to the second finger arm of the interdigitated capacitor, and is parallel to the fingers of the interdigitated capacitor.

[0006] Furthermore, the interdigitated capacitor is a structure formed by interlaced fingers connected by two arms, including two sets of finger and finger arm connection structures. The fingers of these two sets of structures interlaced and spaced apart to form a capacitor. The first finger is perpendicularly connected to the first finger arm to form the first set of finger and finger arm connection structures. The second finger is perpendicularly connected to the second finger arm to form the second set of finger and finger arm connection structures. The first finger arm and the second finger arm are parallel. The first finger and the second finger are both located between the first finger arm and the second finger arm, arranged alternately and parallel to each other, that is, the sides of the first finger are the second finger, and the sides of the second finger are the first finger. The first finger arm and the second finger arm are respectively connected to the two ends of the broken-line inductor, and the second finger arm is perpendicularly connected to the coupling feed line to form the coupling line finger arm.

[0007] Furthermore, the zigzag inductor consists of a horizontal inductor and a vertical inductor; the horizontal inductor is located on the opposite side of the external coupling feed line of the interdigital capacitor and connected to the first finger arm, and the vertical inductor is located on the adjacent side of the external coupling feed line of the interdigital capacitor and connected to the second finger arm; the zigzag inductor bends towards the coupling feed line after being led out from the second finger arm, and is arranged in a zig pattern parallel to the second finger arm; the zigzag inductor bends towards the first finger arm after folding back, and is arranged in a zig pattern parallel to each finger, and then bends vertically after folding back to connect to the first finger arm; the spacing between adjacent wires of the zigzag inductor is equal.

[0008] Furthermore, the zigzag inductor, interdigitated capacitor, and coupling feed line are made of the same superconducting material thin film and are disposed in the receiver slot formed by being surrounded by a coplanar waveguide ground plane.

[0009] Furthermore, the interdigitated capacitor directly achieves terahertz wave absorption through its own mesh-like structure, eliminating the need for an additional absorber.

[0010] Furthermore, the structure of the interdigitated capacitor has essentially the same capacitive effect in the parallel and vertical directions, thereby generating approximately consistent bipolarized absorption peaks near the same target frequency.

[0011] The terahertz focal plane camera device based on variable capacitance of the present invention includes a coplanar waveguide, a resonant receiver, and a coplanar waveguide ground plane disposed on a substrate; the coplanar waveguide includes a center feed line and a feed line connector connected to the end of the center feed line; the center feed line, the feed line connector, and the resonant receiver are surrounded by and insulated from the coplanar waveguide ground plane; there are N×M resonant receivers, arranged in an N×M row and column array; the center feed line is zig-shaped and interspersed between rows or columns of the resonant receiver array; the resonant receivers are the aforementioned receivers; each resonant receiver is coupled to the center feed line through a coupling feed line.

[0012] Furthermore, the piecewise linear inductance of each resonant receiver has a different inductance value, and the resonant frequencies of each resonant receiver form an arithmetic sequence.

[0013] Furthermore, the center feed line is located outside the interdigitated capacitor and is parallel to the coupling feed line; the center feed line and the coupling feed line are separated by a ground isolation section with a coplanar waveguide ground plane.

[0014] Furthermore, the array is disposed on a substrate having high-resistivity silicon and a surface silicon nitride layer or silicon oxide layer.

[0015] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: 1. This invention utilizes the direct absorption of terahertz radiation by interdigitated capacitors, which causes a change in the dipole-two-level system in the dielectric, resulting in a change in the dielectric constant of the dielectric. This change in the capacitance of the interdigitated capacitors leads to a change in the resonant frequency of the resonant receiver. Terahertz wave detection and imaging are achieved by analyzing the change in the resonant frequency of the resonant receiver. The pixel size is adjustable, the interdigitated capacitor fill factor is high, and the array pixel spatial resolution is high.

[0016] 2. The focal plane camera device of the present invention adopts an on-chip integrated design, and the fabrication process is compatible with standard silicon processes, which simplifies the process and facilitates the realization of highly integrated large-scale pixel arrays. The readout system is simple, supports efficient frequency division multiplexing, significantly reduces system complexity and overall manufacturing cost, has good scalability, and is easy to promote.

[0017] 3. The focal plane camera device of the present invention achieves high optical absorption efficiency in a specific frequency band, has dual-polarization detection capability, and can realize high-sensitivity weak signal detection. It is expected to be applied to terahertz passive imaging, spectral analysis and other fields requiring high-sensitivity detection performance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the overall structure of an embodiment of the focal plane camera device of the present invention.

[0019] Figure 2 yes Figure 1 Enlarged view of the section R1 within the dashed box.

[0020] Figure 3 yes Figure 2 Enlarged view of the section R2 within the dashed box (superconducting thin film material is indicated by shading).

[0021] Figure 4 This is a schematic diagram of a finger repetition unit.

[0022] Figure 5 This is a diagram of the bipolarized absorption rate of the finger repeating unit.

[0023] Figure reference numerals: 1-coplanar waveguide, 11-center feeder, 12-feeder connector; 2-Resonant receiver, 200-Resonant receiver array, 21-Bentline inductor, 211-Horizontal inductor, 212-Vertical inductor, 22-Interdigital capacitor, 221-Finger, 2211-First finger, 2212-Second finger, 2213-Finger repeating unit, 222-Finger arm, 2221-First finger arm, 2222-Second finger arm, 25-Coupled feed line; 520-Coupling capacitor; 8-Coplanar waveguide ground plane, 81-Feeder slot, 811-Center feeder slot, 812-Pad slot, 82-Receiver slot, 85-Ground isolation section; 9-Substrate, 91-Dielectric layer. Detailed Implementation

[0024] The technical solution of the present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 An example of a focal plane camera device, namely the terahertz focal plane camera device based on variable capacitance as referred to in this invention, includes a coplanar waveguide 1, a resonant receiver 2, and a coplanar waveguide ground plane 8 disposed on a substrate 9. The substrate 9 is preferably made of high-resistivity silicon with a resistivity ≥20 kΩ•cm and a surface dielectric layer 91. The coplanar waveguide 1 includes a center feed line 11 and a feed line connector 12 connected to the end of the center feed line 11. The center feed line 11, the feed line connector 12, and the resonant receiver 2 are surrounded by and insulated from the coplanar waveguide ground plane 8.

[0026] Those skilled in the art will understand that the dielectric layer 91 can be an amorphous dielectric containing a large number of two-level systems. In this embodiment, the dielectric layer 91 is selected as a silicon nitride layer or silicon oxide layer with a thickness of 300 nm, covering the high-resistivity silicon substrate, and the focal plane camera device is located above the dielectric layer 91. Alternatively, the focal plane camera device can be fabricated on the high-resistivity silicon substrate, with the dielectric layer 91 covering the focal plane camera device.

[0027] For ease of explanation, this specification uses substrate 9 as a horizontal reference ground, and the positions of components on substrate 9 are based on the diagram with left-west, right-east, top-north, and bottom-south. Specifically, components farther from substrate 9 are considered "upper," and those closer to substrate 9 are considered "lower." Figure 1 , Figure 2 , Figure 3 In this diagram, the left side is west, the right side is east, the top is north, and the bottom is south. Those skilled in the art will understand that the positional relationships in this specification are only relative.

[0028] Specifically, a coplanar waveguide ground plane 8 surrounds and forms a feed slot 81 and a receiver slot 82. The feed slot 81 and receiver slot 82 are portions of the substrate 9 directly exposed and not covered by the coplanar waveguide ground plane 8. A coplanar waveguide 1 is disposed within the feed slot 81, and a resonant receiver 2 is disposed within the receiver slot 82. The feed slot 81 includes a central feed slot 811 and a pad slot 812 connected to the end of the central feed slot 811. The central feed 11 is located within the central feed slot 811, and the feed connector 12 is located within the pad slot 812. In this embodiment, the width of the central feed 11 is 20 micrometers, and the width of the insulation gap between it and the edge of the central feed slot 811 is 12 micrometers.

[0029] There are N×M resonant receivers 2, arranged in N×M rows and columns to form a resonant receiver array 200. The center feed line 11 is routed in a zigzag pattern, interspersed between rows or columns of the resonant receiver array 200. In this embodiment, both N and M are 3. That is, the resonant receivers 2 in the resonant receiver array 200 are arranged in 3 rows and 3 columns, for a total of 9 resonant receivers 2.

[0030] Resonant receiver 2, also known as the terahertz receiver based on a variable capacitor as referred to in this invention, is simply called the receiver. (See reference...) Figure 2 The resonant receiver 2 includes a broken-line inductor 21, interdigitated capacitors 22, and a coupling feed line 25. The broken-line inductor 21 and interdigitated capacitors 22 are arranged in a north-south direction. Since the east-west dimension of the coupling feed line 25 is longer than that of the interdigitated capacitors 22, and it provides radio frequency current to ground during resonance, the coplanar waveguide ground plane 8 on the east side of the resonant receiver 2 reserves a certain space for the coupling feed line 25 before moving closer to the first finger arm 2221. Therefore, the receiver slot 82 is not strictly rectangular. The north-south dimension of the receiver slot 82 is W82, and the east-west dimension of the main area is L82. In this embodiment, W82 is preferably 1069 micrometers, and L82 is preferably 972 micrometers. The north-south dimension of the protruding area is W821, and the east-west dimension is L821. In this embodiment, W821 is 36 micrometers, and L821 is 26 micrometers.

[0031] The coupling feed line 25 is used to couple the resonator to the center feed line and is located north of the interdigitated capacitor 22, i.e., the coupling feed line 25 is located at the northernmost edge of the receiver slot 82. The coupling feed line 25 is an east-west oriented line parallel to the north side of the receiver slot 82. The center feed line 11, which runs between rows or columns of the resonant receiver array 200, is located outside the north side of the receiver slot 82 and is parallel to the coupling feed line 25. The center feed line 11 and the coupling feed line 25 are separated by a ground isolation section 85 of the coplanar waveguide ground plane 8. The coupling structure formed by the center feed line 11, the coupling feed line 25, the ground isolation section 85, the gap between the center feed line 11 and the ground isolation section 85, and the gap between the coupling feed line 25 and the ground isolation section 85 constitutes the coupling capacitor 520 composed of the center feed line 11 and the coupling feed line 25. Because a ground isolation section 85 separates the center feeder 11 and the coupling feeder 25, the coupling feeder 25 and the center feeder 11 are weakly coupled, with a coupling coefficient less than 1. In this embodiment, the width of the ground isolation section 85 is 8 micrometers, and the width of the insulation gap between the coupling feeder 25 and the ground isolation section 85 is 8 micrometers.

[0032] The broken-line inductor 21 consists of a horizontal inductor 211 and a vertical inductor 212. The horizontal inductor 211 is located south of the interdigitated capacitor 22 and is arranged in an east-west direction, while the vertical inductor 212 is located west of the interdigitated capacitor 22 and is arranged in a north-south direction. That is, the two ends of the broken-line inductor 21 are located in the east-west direction. The eastern end of the broken-line inductor 21, i.e., the end located in the east direction, is connected to the southern end of the first finger arm 2221; the western end of the broken-line inductor 21, i.e., the end located in the west direction, is connected to the southern end of the second finger arm 2222. Thus, the broken-line inductor 21 and the interdigitated capacitor 22 form an LC resonant circuit, which is connected to the coupling feed line 25 through the second finger arm 2222 to form a coupling line finger arm.

[0033] The zigzag inductor 21 is a wire with a zigzag structure formed by the intersection of mutually perpendicular zigzag lines. The western end of the zigzag inductor 21 extends westward from the south end of the second finger arm 2222 and then bends northward, arranged parallel to the second finger arm 2222 in a zigzag pattern. The zigzag inductor 21 then bends southward and then eastward, arranged parallel to each finger 221 in a zigzag pattern, and finally bends northward after turning eastward to connect with the southern end of the first finger arm 2221. In this embodiment, the spacing between adjacent wires of the zigzag inductor 21 is 10 micrometers.

[0034] The interdigitated capacitor 22 is a structure formed by the crossing of fingers 221 connected by two arms. Specifically, in this embodiment, combined with... Figure 3The interdigitated capacitor 22 includes a connection structure of two sets of fingers 221 and finger arms 222, with the fingers 221 of the two sets of structures interlacing and spacing to form a capacitor. More specifically, the two sets of fingers 221 are a first finger 2211 and a second finger 2212; the two sets of finger arms 222 are a first finger arm 2221 and a second finger arm 2222. The first finger 2211 is perpendicularly connected to the first finger arm 2221 to form the connection structure of the first set of fingers 221 and finger arms 222; the second finger 2212 is perpendicularly connected to the second finger arm 2222 to form the connection structure of the second set of fingers 221 and finger arms 222. The first finger arm 2221 and the second finger arm 2222 are parallel. The first finger arm 2221 is located on the east side of the receiver slot 82, and the connected first finger 2211 is located on the west side of the first finger arm 2221; the second finger arm 2222 is located on the west side of the receiver slot 82, and the connected second finger 2212 is located on the east side of the second finger arm 2222. The first finger 2211 and the second finger 2212 are both located between the first finger arm 2221 and the second finger arm 2222, arranged alternately in a north-south direction and parallel to each other. That is, the north and south sides of the first finger 2211 are the second finger 2212, and the north and south sides of the second finger 2212 are the first finger 2211. The south end of the first finger arm 2221 is vertically connected to the east end of the broken-line inductor 21; the south end of the second finger arm 2222 is connected to the west end of the broken-line inductor 21, and the north end is vertically connected to the coupling feed line 25, forming a coupling line finger arm. The finger 221 is formed by closely parallel finger repeating units 2213, which are appropriately extended by a certain distance D221 at the connection with the finger arm 222, and the two ends of each finger repeating unit 2213 of the first finger 2211 and the second finger 2212 are aligned. (Refer to...) Figure 4 The finger repeating unit 2213 consists of a central rectangular capacitor structure and two side capacitor structures, forming effective capacitance in both the east-west and north-south directions. The east-west length of the finger repeating unit 2213 is L2213, and its north-south length is W2213. The line width and spacing of each line in the central capacitor structure of the finger repeating unit 2213 are W221, while the line width of the side capacitor structures is G2213. The minimum spacing between the fingers 221 is also W221, referring to the spacing between the central structures of each aligned finger repeating unit 2213 of the first finger 2211 and the second finger 2212. The line length of the finger 221 is L221, and the distance between the tip of the finger 221 and the opposite finger arm 222 is D221. The distance between the tip of the finger 221 and the opposite finger arm 222 refers to the distance between the tip of the first finger 2211 and the second finger arm 2222, and the distance between the tip of the second finger 2212 and the first finger arm 2221. In this embodiment, L2213 is preferably 46 micrometers, W2213 is 40 micrometers, G2213 is 6 micrometers, W221 is 4 micrometers, L221 is 891 micrometers, and D221 is 17 micrometers.

[0035] It should be noted that, in order to more clearly demonstrate the structural features of the finger repetition unit 2213, Figures 2-4 The boundaries are schematically represented in the text. In practice, the multiple finger repeating units 2213 constituting the same finger 221 are integrally formed through the same process, forming a seamless and closely arranged continuous structure, with no physical seams or gaps between adjacent repeating units.

[0036] The terahertz detection of the resonant receiver 2 of this invention utilizes the principle of the change in dielectric constant caused by the interaction between a dipole two-level system in a dielectric and an electric field. Its specific working principle is as follows: When detecting terahertz signals, the interdigital capacitor 22 acts as an absorber to receive the terahertz waves. Upon receiving the terahertz signal, the interdigital capacitor 22 transfers energy to the dielectric layer 91. The amorphous dielectric layer 91 contains numerous defect structures, which easily generate two-level systems with dipole moments, affecting the microwave resonance characteristics. This causes the dielectric constant of the dielectric layer 91 to gradually decrease, which in turn causes the capacitance of the interdigital capacitor 22 to gradually decrease, leading to an increase in the resonant frequency of the resonant receiver 2. Therefore, the change in the terahertz response signal can be recorded by reading the frequency change of the resonant receiver 2.

[0037] To complement the operating principle of the resonant receiver 2 described above, in this embodiment of the terahertz focal plane camera device, the coplanar waveguide 1, the coplanar waveguide ground plane 8, and the zigzag inductor 21, interdigitated capacitor 22, and coupling feed line 25 in the resonant receiver 2 are all made of the same superconducting material of the same thickness, specifically a 100-nanometer-thick superconducting tantalum thin film with a superconducting critical transition temperature of approximately 4.3 K. In this embodiment, the focal plane camera device operates in a temperature range of approximately 100 mK to 400 mK, ensuring that the superconducting material remains in a superconducting state and avoiding dynamic inductance effects.

[0038] Those skilled in the art will understand that the interdigitated capacitor 22 in this embodiment can be made of a different superconducting material than the rest, and must satisfy the requirement that its superconducting critical transition temperature is lower than that of the rest. The terahertz focal plane camera device is placed in a cryostat during operation, and the temperature is maintained below 0.1 times the superconducting critical transition temperature of the superconducting material used in the interdigitated capacitor 22.

[0039] Under the structure and size of the finger repetition unit 2213 described above in this embodiment, referring to Figure 5 The finger repetition unit 2213 has an average absorption efficiency of 74.6% for terahertz waves in the north-south and east-west directions at the center frequency of 1.6THz, which is very high. It produces an absorption peak with approximately uniform dual polarization. Therefore, the resonant receiver 2 in this embodiment has polarization in the absorption of terahertz waves in both the east-west and north-south directions.

[0040] Furthermore, in the resonant receiver 2 of the present invention, the resonant frequency of the resonant receiver 2 mainly depends on the inductance and capacitance of the piecewise linear inductor 21 and the interdigital capacitor 22. In this embodiment, the resonant frequency of the resonant receiver 2 is configured between 0.1 and 4 GHz. In this embodiment, the size of the resonant receiver 2 is smaller than the approximate size of the receiver slot 82, which is 1165 micrometers × 966 micrometers, less than one-twentieth of the resonant wavelength.

[0041] Those skilled in the art will understand that the inductance value of the broken-line inductor 21 can be adjusted by adjusting the number of broken lines in the broken-line inductor 21; while the capacitance value of the interdigital capacitor 22 can be adjusted by the number of fingers, finger size parameters, and size parameters of the finger repetition unit 2213 of the interdigital capacitor 22; the terahertz signal absorption frequency of the interdigital capacitor 22 can be adjusted by adjusting the finger repetition unit 2213. In the terahertz focal plane camera device of this embodiment, the interdigital capacitors 22 of each resonant receiver 2 have the same structure and capacitance value, but the broken-line inductors 21 of each resonant receiver 2 are configured with different numbers of broken lines, so that the broken-line inductors 21 of each resonant receiver 2 have different inductance values, thereby making the resonant frequencies of each resonant receiver 2 different, and the resonant frequencies of each resonant receiver 2 form an arithmetic sequence. In this embodiment, the frequency difference of the resonant frequencies of adjacent resonant receivers 2 is approximately 11MHz. The area of ​​the resonant receiver 2 can be scaled down, making the pixel area of ​​the focal plane camera device smaller and the fill factor of the interdigital capacitor 22 higher, thereby improving the spatial resolution. By selecting appropriate interdigitated capacitor 22 superconducting material and adjusting the scale design of the receiver unit, the working band of the focal plane camera device can be flexibly designed in the microwave, millimeter wave, submillimeter wave, mid-infrared, near-infrared and optical bands.

[0042] Compared to conventional linear finger structures, the interdigital capacitor 22 designed and using the double cross-shaped finger repeating unit 2213 in this embodiment also functions as an absorber. Its absorption efficiency for terahertz waves in both the north-south and east-west directions averages 74.6% at the center frequency of 1.6 THz, demonstrating high absorption efficiency and producing a nearly uniform bipolar absorption peak. No external structure is needed to achieve the absorber function or bipolarization, simplifying the device structure and increasing integration. Compared to detectors based on superconducting dynamic inductors, this embodiment greatly simplifies the structure of the zigzag inductor 21. The performance of the resonant receiver 2 mainly depends on the two-level system of the dielectric layer 91 and the structure of the interdigital capacitor 22, reducing the requirements for material selection and operating temperature control, and increasing the fill factor of the interdigital capacitor 22, thereby improving the spatial resolution of the focal plane array.

[0043] The working principle of the focal plane camera device in this embodiment is as follows: When the focal plane camera device is in operation, a signal corresponding to the resonant frequency is injected into each resonant receiver 2 through one end of the coplanar waveguide 1, causing each resonant receiver 2 to enter a resonant state. When each resonant receiver 2 detects terahertz waves, a change in resonant frequency occurs. The data acquisition system connected to the other end of the coplanar waveguide 1 receives the coupled output signals of each resonant receiver 2 after resonance, coupled to the center feed line 11 through the coupling feed line 25. The data acquisition system performs spectrum analysis on the signals output by the coplanar waveguide 1 to determine whether the resonant receiver 2 has received a terahertz wave signal.

[0044] Based on the above working principle, the resonant receiver 2 requires that the resonant energy be preserved as much as possible when receiving the injected signal. Therefore, the broken-line inductor 21, interdigitated capacitor 22, coupling feed line 25, and coplanar waveguide 1 are required to be in a superconducting state to reduce resonant energy loss. That is, the resonant receiver 2 is required to have a high intrinsic quality factor. The resonant energy loss of the resonant receiver 2 comes from the energy output caused by the coupling between the circuit itself and the external environment. In this embodiment, the intrinsic quality factor of each resonant receiver 2 is not less than 10. 4 .

Claims

1. A terahertz receiver based on a variable capacitor, comprising a connected piecewise linear inductor (21), an interdigital capacitor (22), and a coupling feed line (25), characterized in that, Each finger (221) of the interdigital capacitor (22) is composed of closely arranged double cross-shaped finger repeating units (2213). The finger repeating unit (2213) is composed of a central rectangular capacitor structure and parallel plate capacitor structures on both sides symmetrical about the center of the rectangle. The broken line inductor (21) is connected to the interdigital capacitor (22) to form a resonant circuit. The coupling feed line (25) is set outside the interdigital capacitor (22) and connected to the second finger arm (2222) of the interdigital capacitor (22), and is parallel to the finger (221) of the interdigital capacitor (22).

2. The receiver according to claim 1, characterized in that, The interdigitated capacitor (22) is a structure formed by the interlacing of two connected fingers (221), including a connection structure of two sets of fingers (221) and finger arms (222). The fingers (221) of the two sets of structures interlaced and spaced to form a capacitor; the first finger (2211) is perpendicularly connected to the first finger arm (2221) to form the connection structure of the first set of fingers (221) and finger arms (222); the second finger (2212) is perpendicularly connected to the second finger arm (2222) to form the connection structure of the second set of fingers (221) and finger arms (222); the first finger arm (2221) and the second finger arm (2222) are connected to each other. The finger arms (2222) are parallel; the first finger (2211) and the second finger (2212) are both located between the first finger arm (2221) and the second finger arm (2222), arranged alternately and parallel to each other, that is, the second finger (2212) is on both sides of the first finger (2211), and the first finger (2211) is on both sides of the second finger (2212); the first finger arm (2221) and the second finger arm (2222) are respectively connected to the two ends of the broken line inductor (21), and the second finger arm (2222) is perpendicularly connected to the coupling feed line (25) to form the coupling line finger arm.

3. The receiver according to claim 1, characterized in that, The zigzag inductor (21) consists of a horizontal inductor (211) and a vertical inductor (212). The horizontal inductor (211) is located on the opposite side of the external coupling feed line (25) of the interdigital capacitor (22) and is connected to the first finger arm (2221). The vertical inductor (212) is located on the adjacent side of the external coupling feed line (25) of the interdigital capacitor (22) and is connected to the second finger arm (2222). The zigzag inductor (21) is led out from the second finger arm (2222) and bends towards the coupling feed line (25), and is arranged in a zig shape parallel to the second finger arm (2222). After the zigzag inductor (21) is folded back, it bends towards the first finger arm (2221), and is arranged in a zig shape parallel to each finger (221). After folding back, it bends vertically and is connected to the first finger arm (2221). The spacing between adjacent wires of the zigzag inductor (21) is equal.

4. The receiver according to claim 1, characterized in that, The zigzag inductor (21), interdigitated capacitor (22) and coupling feed line (25) are made of the same superconducting material thin film and are disposed in the receiver slot (82) formed by being surrounded by a coplanar waveguide ground plane (8).

5. The receiver according to claim 1, characterized in that, The interdigitated capacitor (22) directly achieves terahertz wave absorption through its own mesh-like structure, without the need for an additional absorber.

6. The receiver according to claim 1, characterized in that, The structure of the interdigital capacitor (22) has essentially the same capacitance effect in the parallel and vertical directions, thereby producing approximately consistent bipolar absorption peaks near the same target frequency.

7. A terahertz focal plane camera device based on variable capacitance, characterized in that, The system includes a coplanar waveguide (1), a resonant receiver (2), and a coplanar waveguide ground plane (8) disposed on a substrate (9). The coplanar waveguide (1) includes a center feed line (11) and a feed line connector (12) connected to the end of the center feed line (11). The center feed line (11), the feed line connector (12), and the resonant receiver (2) are surrounded by the coplanar waveguide ground plane (8) and are insulated from the coplanar waveguide ground plane (8). There are N×M resonant receivers (2), which are arranged in N×M rows and columns to form a resonant receiver array (200). The center feed line (11) is zig-shaped and interspersed between rows or columns of the resonant receiver array (200). The resonant receiver (2) is the receiver described in any one of claims 1-6. Each resonant receiver (2) is coupled to the center feed line (11) through a coupling feed line (25).

8. The focal plane camera device according to claim 7, characterized in that, Each resonant receiver (2) has a different inductance value for its piecewise linear inductance (21), and the resonant frequencies of each resonant receiver (2) are in an arithmetic sequence.

9. The focal plane camera device according to claim 7, characterized in that, The center feed line (11) is located outside the interdigitated capacitor (22) and parallel to the coupling feed line (25); the center feed line (11) and the coupling feed line (25) are separated by a ground isolation section (85) of the coplanar waveguide ground plane (8).

10. The focal plane camera device according to claim 7, characterized in that, The resonant receiver array (200) is disposed on a substrate having a high-resistivity silicon substrate and a surface silicon nitride layer or silicon oxide layer.

Images