CN116242489A - Terahertz detector and system based on double-frequency super-surface wave-absorbing structure - Google Patents
Terahertz detector and system based on double-frequency super-surface wave-absorbing structure Download PDFInfo
- Publication number
- CN116242489A CN116242489A CN202211695726.2A CN202211695726A CN116242489A CN 116242489 A CN116242489 A CN 116242489A CN 202211695726 A CN202211695726 A CN 202211695726A CN 116242489 A CN116242489 A CN 116242489A
- Authority
- CN
- China
- Prior art keywords
- terahertz
- super
- terahertz detector
- array
- detector
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Pending
Links
- 230000008878 coupling Effects 0.000 claims abstract description 43
- 238000010168 coupling process Methods 0.000 claims abstract description 43
- 238000005859 coupling reaction Methods 0.000 claims abstract description 43
- 239000000758 substrate Substances 0.000 claims abstract description 42
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 39
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 39
- 239000010703 silicon Substances 0.000 claims abstract description 39
- 230000005855 radiation Effects 0.000 claims abstract description 31
- 230000004044 response Effects 0.000 claims abstract description 29
- 238000009413 insulation Methods 0.000 claims abstract description 26
- 238000010521 absorption reaction Methods 0.000 claims abstract description 21
- 230000008859 change Effects 0.000 claims abstract description 8
- 238000001514 detection method Methods 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims abstract description 7
- 239000002184 metal Substances 0.000 claims description 26
- 229910052751 metal Inorganic materials 0.000 claims description 26
- 238000003384 imaging method Methods 0.000 claims description 17
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 11
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 11
- 230000003287 optical effect Effects 0.000 claims description 5
- 230000005540 biological transmission Effects 0.000 claims description 4
- 239000011358 absorbing material Substances 0.000 abstract description 4
- 239000010410 layer Substances 0.000 description 18
- 230000035945 sensitivity Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 6
- 238000013461 design Methods 0.000 description 5
- 238000002360 preparation method Methods 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- 230000000694 effects Effects 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000007689 inspection Methods 0.000 description 3
- 230000000737 periodic effect Effects 0.000 description 3
- 239000000523 sample Substances 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 238000000862 absorption spectrum Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000004364 calculation method Methods 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 239000003989 dielectric material Substances 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- PCHJSUWPFVWCPO-UHFFFAOYSA-N gold Chemical compound [Au] PCHJSUWPFVWCPO-UHFFFAOYSA-N 0.000 description 2
- 239000010931 gold Substances 0.000 description 2
- 229910052737 gold Inorganic materials 0.000 description 2
- 238000011897 real-time detection Methods 0.000 description 2
- 238000004088 simulation Methods 0.000 description 2
- 208000000453 Skin Neoplasms Diseases 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 239000008358 core component Substances 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000003745 diagnosis Methods 0.000 description 1
- 238000002059 diagnostic imaging Methods 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000007667 floating Methods 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 239000005022 packaging material Substances 0.000 description 1
- 239000000123 paper Substances 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 238000005057 refrigeration Methods 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 239000002356 single layer Substances 0.000 description 1
- 231100000075 skin burn Toxicity 0.000 description 1
- 201000000849 skin cancer Diseases 0.000 description 1
- 230000003595 spectral effect Effects 0.000 description 1
Images
Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/08—Optical arrangements
- G01J5/0806—Focusing or collimating elements, e.g. lenses or concave mirrors
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/02—Constructional details
- G01J5/08—Optical arrangements
- G01J5/0896—Optical arrangements using a light source, e.g. for illuminating a surface
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/48—Thermography; Techniques using wholly visual means
- G01J5/485—Temperature profile
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J2005/0077—Imaging
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01J—MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY
- G01J5/00—Radiation pyrometry, e.g. infrared or optical thermometry
- G01J5/10—Radiation pyrometry, e.g. infrared or optical thermometry using electric radiation detectors
- G01J2005/106—Arrays
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Landscapes
- Physics & Mathematics (AREA)
- General Physics & Mathematics (AREA)
- Spectroscopy & Molecular Physics (AREA)
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
The invention relates to a terahertz detector and a terahertz detector system based on a double-frequency super-surface wave-absorbing structure, and belongs to the field of detectors; comprises a coupling module and a reading module; the coupling module is used for coupling terahertz radiation and outputting an optical-thermal response in the form of temperature change; the reading module is used for reading the photo-thermal response output by the coupling module, completing the representation of the terahertz radiation power value and realizing terahertz detection; the coupling module comprises a focal plane array, and is formed by closely and seamlessly arranging a plurality of square array elements in a plane, wherein the structures and materials of the array elements are the same; the array element comprises a super-surface unit array, a heat insulation cantilever and a silicon substrate, wherein the super-surface unit array is suspended at a hollow part at the bottom of the silicon substrate through the heat insulation cantilever. According to the invention, by introducing the super-surface wave-absorbing structure, the problem of low absorption efficiency of the wave-absorbing material in the terahertz detector is solved; and designing a signal reading system based on a thermal imager, and directly reading out a thermal response signal of the detector.
Description
Technical Field
The invention belongs to the field of detectors, and particularly relates to a terahertz detector and a terahertz detector system based on a double-frequency super-surface wave-absorbing structure.
Background
Because of the unique characteristics of terahertz waves, terahertz (THz) imaging has been widely focused in the past two decades and gradually becomes a highly active field, and terahertz technology has wide application prospects in various fields such as security inspection, medical imaging, remote sensing and the like. Many commonly used packaging materials, such as paper, fabric, plastics, etc., are transparent to terahertz waves, and thus terahertz imaging techniques have great potential in the fields of security inspection and nondestructive inspection. The photon energy of terahertz radiation is low, ionization risk is not caused, and terahertz fingerprint spectral characteristics of biomacromolecules enable terahertz imaging to be used as a tool for medical diagnosis and analysis, particularly in the aspects of skin burn and skin cancer. And as a core component in the terahertz imaging system, a terahertz detector with high sensitivity and real-time response is paid attention to by researchers. Generally, terahertz detectors can be divided into two categories: photon detectors and heat detectors. While photon detectors have high sensitivity and extremely fast response times, most photon detectors operate in a narrow band and their need for a cryogenic cooling system results in their high cost and bulk. The heat detector absorbs terahertz radiation as heat, producing a measurable output signal. Typical heat detectors are capable of operating at room temperature with good sensitivity and response time, such as thermopiles, pyroelectric detectors, golay detectors, and the like.
By operating in a scanning mode using the photon or heat detector described above, it may take tens of seconds to hours to obtain a two-dimensional image. Recently, a focal plane array type detector based on an infrared microbolometer has been proposed, and some researches have proved that the detector is applied to a real-time terahertz imaging system, and a terahertz image is shot only by tens of microseconds. However, the sensitivity of such focal plane detectors is greatly affected by the lack of suitable terahertz wave absorbing materials. And because of the need of configuring a high-speed reading circuit for the focal plane array detector, the array scale and the process feasibility are limited to a certain extent.
The concept of the super surface provides a new technical approach for improving the sensitivity of the terahertz detector. A supersurface is an artificially designed, prepared two-dimensional periodic structure, which is typically formed by a series of sub-wavelength units arranged periodically. The macroscopic electromagnetic property of the super surface can be adjusted by designing the unit structure and the size of the super surface, and the regulation and control of the polarization, the phase and the amplitude of electromagnetic waves are realized, and the electromagnetic response and the frequency freedom degree of the super surface are far beyond those of natural materials. The super-surface wave-absorbing structure is applied to the terahertz detector, so that the absorption rate far higher than that of a natural wave-absorbing material can be realized, the absorption frequency can be flexibly designed, and the working frequency of the detector can be adjusted.
Aiming at the problems, the terahertz detector with the characteristics of high wave absorption efficiency, simple reading structure, flexible frequency design and the like is urgently needed.
Disclosure of Invention
The technical problems to be solved are as follows:
in order to avoid the defects of the prior art, the invention provides the terahertz detector based on the double-frequency super-surface wave-absorbing structure, the problem of low absorption efficiency of wave-absorbing materials in the terahertz detector is mainly solved by introducing the super-surface wave-absorbing structure, and a signal reading system based on a thermal imager is designed for reading out a thermal response signal of the detector under the condition of no need of a reading circuit. Aiming at the problems of low absorption efficiency and the like in the existing terahertz detector technology, the following effects are achieved: 1) The detection function under the environment of the room temperature 293K is realized, and refrigeration equipment is not needed; 2) The dual-frequency point detection is realized, and the frequency flexibility is high; 3) The wave absorption efficiency is higher than 90%; 4) Response time is 68ms, and real-time imaging requirements are met; 5) The thermal imager is adopted to read out the response of the detector, so that the preparation complexity brought by a reading circuit is reduced, and the modularized design is realized.
The technical scheme of the invention is as follows: a terahertz detector based on a double-frequency super-surface wave-absorbing structure comprises a coupling module and a reading module; the coupling module is used for coupling terahertz radiation and outputting an optical-thermal response in the form of temperature change; the reading module is used for reading the photo-thermal response output by the coupling module, completing the representation of the terahertz radiation power value and realizing terahertz detection;
the coupling module comprises a focal plane array, and is formed by closely and seamlessly arranging a plurality of square array elements in a plane, wherein the structures and materials of the array elements are the same; the array element comprises a super-surface unit array, a heat insulation cantilever and a silicon substrate, wherein the super-surface unit array is suspended at a hollow part at the bottom of the silicon substrate through the heat insulation cantilever.
The invention further adopts the technical scheme that: the super surface unit array comprises 25 super surface units in a 5 multiplied by 5 mode, the super surface units are of a three-layer structure with two absorption peaks, the top layer and the bottom layer are metal, the middle is a medium layer, and the surface current coupling in the top layer and the bottom layer metal is utilized to inject terahertz waves, so that high-efficiency double-frequency wave absorption is realized.
The invention further adopts the technical scheme that: the top layer of the super surface unit comprises a metal square ring and a metal circular ring which are concentrically arranged, the resonances are respectively 3.18THz and 5.17THz, and the metal of the bottom layer of the super surface unit is combined to absorb electromagnetic waves with two frequencies.
The invention further adopts the technical scheme that: the metal square ring and the metal circular ring are in non-contact, and the circular ring is positioned outside the square ring; wherein, the side length of the square ring is 2a, and the line width is w 4 The radius of the circular ring isr, line width w 5 ，r＝1.5×a+0.2μm+w 5 ,3μm≤a≤4μm。
The invention further adopts the technical scheme that: the side length of the super surface unit is p 2 ，2r+1μm≤p 2 2r+3 mu m or less; the thickness of the top metal and the bottom metal of the super surface unit is h 2 ，h 2 Between 0.1 and 0.5 μm; the thickness of the dielectric layer and the thickness of the heat insulation cantilever in the super-surface unit are both h 3 ，h 3 Between 0.8 and 2 μm.
The invention further adopts the technical scheme that: the cross section of the silicon substrate is p 1 Is of a thickness h 1 ，h 1 300 μm; square through holes are formed in the silicon substrate, and the side length of each square through hole is w 1 ，w 1 ＝5×p 2 +4μm; the ultra-surface unit array is suspended at the bottom of the silicon substrate through a heat insulation cantilever arranged circumferentially, and 5 multiplied by 5 ultra-surface units are opposite to square through holes in the silicon substrate; the heat insulation cantilever is used for isolating the ultra-surface unit array from the silicon substrate, so that heat loss caused by heat exchange is avoided.
The invention further adopts the technical scheme that: the heat insulation cantilever is made of silicon nitride and is of a square annular structure with one side open, the open end of the heat insulation cantilever is connected with the edges of the two opposite sides of the super-surface unit, and the connection width of the heat insulation cantilever and the super-surface unit is w 2 ，w 2 In the range of 4-8 μm; the heat insulation cantilever is provided with a length w on the arm surface opposite to the opening side 3 Jin Maodian the Jin Maodian is the junction surface of the heat-insulating cantilever and the silicon substrate, w 3 Between 10 and 20 μm; the square ring side length of the heat insulation cantilever is l, l=p 2 ×5+w 2 ×2。
The invention further adopts the technical scheme that: the detector size parameters are shown in the following table:
the invention further adopts the technical scheme that: the reading module is a thermal infrared imager, the size of an observation area of the thermal infrared imager is 2cm multiplied by 2cm, the spatial resolution is 400 multiplied by 400, the temperature resolution is 50mK, and the response time is 10ms.
A transmissive terahertz imaging system, characterized in that: the device comprises a terahertz radiation source, a terahertz optical lens group, a terahertz detector and an infrared thermal imager, wherein a beam emitted by the terahertz radiation source is collimated by the terahertz optical lens group and then enters the terahertz detector, and a temperature distribution image of the plane of the terahertz detector, namely a transmission terahertz imaging of an object to be detected is realized by observing the temperature distribution image of the plane of the terahertz detector through the infrared thermal imager, namely the temperature distribution image is equivalent to the terahertz radiation intensity distribution image;
the plane of the terahertz detector is completely in line with the observation field of view of the thermal infrared imager, and the observation direction of the thermal infrared imager is perpendicular to the plane of the terahertz detector.
Advantageous effects
The invention has the beneficial effects that: the invention relates to a terahertz detector based on a double-frequency super-surface wave-absorbing structure, which has the advantages compared with the existing terahertz detector in the following aspects:
1. the invention can realize real-time detection at room temperature (293K). The invention provides a terahertz detector which is basically a thermal detector, can work with normal sensitivity in an environment with the temperature of 293K, and has the response time of 68ms, thereby meeting the requirement of real-time detection. The detector in the invention already forms a 200 multiplied by 200 focal plane array, and can realize staring real-time terahertz imaging by combining a thermal infrared imager.
The detector provided by the embodiment of the invention faces the room temperature environment (293K) at the beginning of design, and the characteristic analysis and the parameter optimization of all structures are simulated in the 293K environment. The temperature change during operation of the probe is shown in fig. 5, where the temperature onset is seen at 293K. In addition, fig. 5 also shows that the probe reaches a steady state temperature substantially at 68ms, so the response time of the probe is 68ms. For the array scale, the resolution of the thermal infrared imager is 400×400, and the observation area is 2cm×2cm. Whereas in the range of 2cm by 2cm, the array of detectors that can be accommodated is 200 by 200 in size.
2. The invention has the double-frequency detection characteristic, and the double-frequency absorption rate is more than 90%. The invention introduces the super-surface structure as the coupling structure of the detector, optimizes the structural parameters of the super-surface structure, and improves the absorption rate by two times compared with the existing conventional natural wave-absorbing film, wherein the absorption rate at two working frequencies is more than 90 percent. The super-surface unit provided by the invention internally comprises two resonant structures, is a composite unit, and can have very high absorptivity at two frequencies. Fig. 4 shows the wave-absorbing spectrum of the super surface, which is evident as having two absorption peaks, with absorption higher than 90%, near perfect absorption.
3. The invention does not require complex integrated readout circuitry. By adopting a mode of observing and reading by the thermal infrared imager, the focal plane array of the detector can complete imaging of terahertz radiation distribution without a complex integrated reading circuit. The design reduces the preparation cost, is beneficial to realizing the modularized design, namely, the detection and imaging of terahertz waves with different frequencies can be realized only by replacing the coupling module.
Preferably, the side length p of the subsurface unit 2 Is influenced by the radius of the ring and becomes smaller in synchronism therewith, in any case the side length p of the super-surface unit 2 Should be no less than 2r+1 μm to avoid overlapping of structures between adjacent supersurface elements; at the same time, an excessively large p 2 The arrangement of the resonance structure in the super surface is too sparse, the absorptivity is affected, and therefore p 2 Should not exceed 2r+3 μm, p within this range 2 The variation of (c) does not have a significant effect on the electromagnetic properties of the subsurface.
Preferably, the thickness of the top metal and the bottom metal in the super surface is consistent, and the thicknesses are h 2 Limited by the preparation process, excessively large h 2 Cannot be prepared, and h 2 The value of (h) has a slight influence on the super-surface absorptivity 2 Should vary between 0.1 and 0.5 μm.
Preferably, the thickness of the super-surface medium layer and the thickness of the silicon nitride cantilever are all h 3 ，h 3 The numerical value of (2) is mainly considered in the super-surface wave-absorbing characteristic, and is to ensureThe composition has higher absorptivity in the terahertz wave band, and h 3 Is limited between 0.8 and 2 mu m.
Preferably, the thickness of the silicon substrate is h 1 The thinner the better, the thinnest silicon substrate thickness is 300 μm under the current process system.
Preferably, w 1 The method refers to the side length of the hole above the silicon substrate, the numerical requirement is slightly larger than the side length of the super-surface array, but too large square holes can lead to too sparse arrangement of detector units, and the effective area is wasted. The size of the supersurface array is 5*5, thus defining w 1 ＝5*p 2 +4μm。
Preferably, w 2 Since the silicon nitride cantilever mainly plays a role of heat insulation in the invention, the contact surface area between the silicon nitride cantilever and the super surface is as small as possible. However, too small a contact surface can result in a less tight bond between the super-surface structure and the cantilever structure, resulting in structural failure. Therefore w2 should be regulated in the range of 4-8 μm.
Preferably, w 3 Is the length of the contact surface of the cantilever with the silicon substrate, which can be regarded as an anchor point for fixing the cantilever to the silicon substrate. From the perspective of sensitivity performance of the detector, w 3 Should be as small as possible to reduce the heat loss due to heat exchange between the cantilever and the silicon substrate; but too small w 3 The connection strength between the cantilever structure and the silicon substrate is insufficient, and the structure is separated. Therefore, w 3 Should be regulated between 10 and 20 mu m.
Drawings
FIG. 1 is a disassembled view of a single array element structure of a coupling module;
FIG. 2 is a schematic diagram of a single array element structure of the coupling module; (a) an isometric view, (b) a top view, (c) a bottom view, and (d) a side view;
FIG. 3 is a schematic diagram of the parameters of the structure of a single array element of the coupling module; (a) a side view of a single array element, (b) a top view of a single subsurface unit, (c) a top view of a thermally insulated cantilever;
the detector coupling module of fig. 4 absorbs the spectrum;
fig. 5 couples (a) photothermal response time and (b) photothermal responsivity of the module.
Reference numerals illustrate: 1. the coupling module comprises a single array element, a through hole, a silicon substrate, a heat insulation cantilever, a gold anchor point, a super-surface unit array, a super-surface unit and a silicon nitride cantilever.
Detailed Description
The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention.
Referring to fig. 1, the present embodiment is a terahertz detector based on a dual-frequency super-surface wave absorbing structure and a thermal imager, where the detector is a thermal detector and includes two sub-modules, namely a coupling module and a readout module. The coupling module is used for coupling terahertz radiation and outputting an optical-thermal response in the form of temperature change; the reading module is used for reading the optical-thermal response output by the coupling module, and finally, the terahertz radiation power is characterized, so that the terahertz detection function is realized. In order to realize the efficient absorption of terahertz waves and meet the requirements of quick response and real-time imaging, the invention uses a super-surface structure as a coupling module; in order to reduce the structural complexity and reduce the preparation cost, the invention adopts the thermal infrared imager and a matched light path as a reading module.
Specifically, the coupling module in this embodiment is a focal plane array, which is formed by closely and seamlessly arranging 200×200 square array elements on a plane, where the structures and materials of the array elements are identical. One array element also includes 5×5 super surface units (hereinafter simply referred to as "units"), and a heat-insulating cantilever. The reading module adopts a thermal infrared imager to read the temperature of each array element in the focal plane array, so as to obtain the terahertz radiation power received by each array element.
The structure and principle of the coupling module are described: as mentioned above, the coupling module is a focal plane array with an array scale of 200×200, and the structure and materials of each array element are consistent, so only a single array element and the periodic arrangement direction of the array element will be described herein. As shown in FIG. 1, one array element comprises three parts, namely a super-surface unit array, a heat insulation cantilever and a silicon substrate. The super surface unit array consists of 5×5 units in the same structure and material. To more clearly show the cell structure, a single super surface cell (simply "cell") is drawn within the dashed box on the right side of fig. 1; the unit comprises a three-layer structure, wherein the top layer and the bottom layer are of metal structures, and the middle layer is of a medium structure. The dimensional parameters of each structure are shown in table 1. The top layer of the cell comprises a metal square ring and a metal circular ring, which are sized differently, and exhibit magnetic dipole-like resonance characteristics at 3.18THz and 5.17THz frequencies, respectively, so that the cell possesses an absorption of over 90% at 3.18THz and 5.17THz, as shown by the full wave simulated absorption spectrum in fig. 4. The heat-insulating cantilever is made of a single-layer dielectric material, and has the main function of separating the super-surface unit array from the silicon substrate as shown in the table 1, so that the super-surface unit array is suspended, and heat exchange between the super-surface unit array and the silicon substrate is reduced or even insulated. The heat insulation structure is necessary for the array elements to form an array, otherwise, heat conduction can occur between the array elements between the arrays, so that the focal plane array cannot accurately reflect the terahertz radiation power distribution received by the focal plane array. The silicon substrate is a structure as a substrate in a semiconductor process, and its thickness is 300 μm. It can be seen from fig. 1 that there are square vias in the silicon substrate, with the via locations being located above the array of super surface units. The through hole structure is used for avoiding attenuation of the terahertz radiation caused by the silicon substrate, so that the terahertz radiation can directly reach the ultra-surface unit array through the square through holes. The parameters of the size of the through holes are shown in table 1. So far, three parts of an array element are all described.
Fig. 2 is an isometric view, a top view, a bottom view and a side view of an array element of a coupling module, wherein the outer contour of the array element is square as can be seen from fig. 2 (b) (c), and the array element forms a periodic arrangement direction of the focal plane array, i.e. extends along two adjacent sides of the outer contour of the array element, as indicated by arrows in fig. 2 (b) (c). The period size is the outline side length of the array element, and the specific numerical parameters are shown in table 1. Fig. 3 marks specific structural dimensions of individual array elements of the detector coupling module. Gold is adopted for all metal structures in the array element, and silicon nitride (relative dielectric constant 9.7) is adopted for dielectric materials. Terahertz radiation is incident on one side of a photosurface (i.e. the side where a silicon substrate is located) to a focal plane array (i.e. a coupling module), and after the terahertz radiation is absorbed by the super-surface unit array, temperature change is generated, and an optical-thermal response curve of an array element is obtained through multi-physical field simulation, as shown in fig. 5, so that an optical-thermal response of the focal plane array (i.e. the coupling module) can be calculated as follows: 0.23 K.mm 2 mu.W, response time was 58ms.
The readout module: the absorption efficiency of the coupling module, the optical-thermal response, and the readout module need to read the temperature change of the coupling module, so that the incident terahertz radiation power is obtained according to inversion of the optical-thermal response calculation value of the coupling module. The coupling module is observed and the temperature profile is read out using a thermal infrared imager. The thermal infrared imager observation area is 2cm multiplied by 2cm, the spatial resolution is 400 multiplied by 400, the temperature resolution is 50mK, and the response time is 10ms. When in observation, the thermal infrared imager is arranged on one side of the dark surface of the coupling module (namely, the thermal infrared imager and terahertz radiation are separated from the two sides of the coupling module), and the plane where the coupling module is located is observed vertically.
Through the performance simulation and calculation, the response time of the terahertz detector is 68ms, and the minimum observable power is 2nW. Can meet the requirements of real-time and high-sensitivity imaging.
The dimensional parameters of the detector of the embodiment are mutually constrained:
square ring edge length 2a, line width w 4 Radius r and line width w of circular ring 5 These four parameters will affect the absorption spectrum of the super-surface wave-absorbing structure, any slight variation of the parameters will cause the wave-absorbing characteristics of the super-surface to change, where w 4 ＝1μm，w 5 ＝0.25μm，r＝1.5×a+0.2μm+w 5 The a is more than or equal to 3 mu m and less than or equal to 4 mu m, so that the inner ring and the outer ring are ensured not to overlap structurally, and resonance peaks caused by the inner ring and the outer ring in frequency spectrum are effectively separated. For this structural dimensioning, the requirements are: the ring is positioned outside the square ring without contact between the ring and the square ring.
Side length p of super surface unit 2 Is influenced by the radius of the ring and becomes smaller in synchronism therewith, in any case the side length p of the super-surface unit 2 Should be no less than 2r+1 μm to avoid overlapping of structures between adjacent supersurface elements; at the same time, an excessively large p 2 The arrangement of the resonance structure in the super surface is too sparse, the absorptivity is affected, and therefore p 2 Should not exceed 2r+3 μm, p within this range 2 The variation of (c) does not have a significant effect on the electromagnetic properties of the subsurface.
The thickness of the top layer metal and the bottom layer metal in the super surface is the same, and the thicknesses are h 2 Limited by the preparation process, excessively large h 2 Cannot be prepared, and h 2 The value of (h) has a slight influence on the super-surface absorptivity 2 Should vary between 0.1 and 0.5 μm.
The thickness of the super-surface medium layer and the thickness of the silicon nitride cantilever are all h 3 ，h 3 The numerical value of (2) is mainly in consideration of the super-surface wave absorption characteristic, and h is used for ensuring higher absorptivity in the terahertz wave band 3 Is limited between 0.8 and 2 mu m.
h 1 Refers to the thickness of the wafer substrate, and the thinner the wafer substrate, the better, and under the current process system, the thinnest silicon substrate has the thickness of 300 mu m.
w 1 Refers to the side length of the hole above the silicon substrate, the numerical requirement is slightly larger than the side length of the super-surface array, but too large square holes can lead to too sparse arrangement of detector units and wasteAn effective area. The size of the supersurface array is 5*5, thus defining w 1 ＝5*p 2 +4μm。
w2 is the contact surface width of the silicon nitride cantilever and the super surface, and the contact surface area of the silicon nitride cantilever and the super surface is as small as possible because the silicon nitride cantilever mainly plays a role of heat insulation in the invention. However, too small a contact surface can result in a less tight bond between the super-surface structure and the cantilever structure, resulting in structural failure. Therefore w2 should be regulated in the range of 4-8 μm.
w 3 Is the length of the contact surface of the cantilever with the silicon substrate, which can be regarded as an anchor point for fixing the cantilever to the silicon substrate. From the perspective of sensitivity performance of the detector, w 3 Should be as small as possible to reduce the heat loss due to heat exchange between the cantilever and the silicon substrate; but too small w 3 The connection strength between the cantilever structure and the silicon substrate is insufficient, and the structure is separated. Therefore, w 3 Should be regulated between 10 and 20 mu m.
The value of the cantilever length l is subject to the super surface unit side length p 2 Cantilever width w 2 To achieve the structural feature of floating the supersurface, define l=p 2 *5+w 2 *2。
Further, the size parameters of the detector of this embodiment are shown in the following table:
table 1 detector size parameter table
The embodiment relates to a transmission terahertz imaging system, which is used for explaining the application scene of a terahertz detector:
1) A terahertz radiation source with a radiation frequency of 3.18THz (or 5.17 THz) is used and its beam is collimated so that it is perpendicularly incident on the plane of the terahertz detector proposed by the present invention. In the collimation process, terahertz optical lens groups such as off-axis parabolic mirrors, collimating lenses and the like can be used, and special requirements are not required.
2) The infrared thermal imager and the terahertz radiation source are respectively arranged at two sides of the plane of the terahertz detector, and the observation range and the angle of the infrared thermal imager are adjusted, so that the plane of the terahertz detector and the observation field of the infrared thermal imager are completely in line, and the observation direction of the infrared thermal imager is vertical to the plane of the terahertz detector.
3) Opening a terahertz radiation source and an infrared thermal imager, placing an object to be observed in a collimated terahertz wave beam, and blocking and attenuating terahertz radiation; and observing a temperature distribution image of the plane of the terahertz detector in the thermal infrared imager, namely, the temperature distribution image is equivalent to a terahertz radiation intensity distribution image, so as to realize transmission terahertz imaging of the object to be detected.
Although embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the invention, and that variations, modifications, alternatives, and variations may be made in the above embodiments by those skilled in the art without departing from the spirit and principles of the invention.
Claims (10)
1. Terahertz detector based on double-frequency super surface wave-absorbing structure, its characterized in that: comprises a coupling module and a reading module; the coupling module is used for coupling terahertz radiation and outputting an optical-thermal response in the form of temperature change; the reading module is used for reading the photo-thermal response output by the coupling module, completing the representation of the terahertz radiation power value and realizing terahertz detection;
the coupling module comprises a focal plane array, and is formed by closely and seamlessly arranging a plurality of square array elements in a plane, wherein the structures and materials of the array elements are the same; the array element comprises a super-surface unit array, a heat insulation cantilever and a silicon substrate, wherein the super-surface unit array is suspended at a hollow part at the bottom of the silicon substrate through the heat insulation cantilever.
2. The terahertz detector based on the double-frequency super-surface wave-absorbing structure according to claim 1, wherein the terahertz detector is characterized in that: the super surface unit array comprises 25 super surface units in a 5 multiplied by 5 mode, the super surface units are of a three-layer structure with two absorption peaks, the top layer and the bottom layer are metal, the middle is a medium layer, and the surface current coupling in the top layer and the bottom layer metal is utilized to inject terahertz waves, so that high-efficiency double-frequency wave absorption is realized.
3. The terahertz detector based on the double-frequency super-surface wave-absorbing structure according to claim 1, wherein the terahertz detector is characterized in that: the top layer of the super surface unit comprises a metal square ring and a metal circular ring which are concentrically arranged, the resonances are respectively 3.18THz and 5.17THz, and the metal of the bottom layer of the super surface unit is combined to absorb electromagnetic waves with two frequencies.
4. The terahertz detector based on the dual-frequency super-surface wave-absorbing structure according to claim 3, wherein the terahertz detector is characterized in that: the metal square ring and the metal circular ring are in non-contact, and the circular ring is positioned outside the square ring; wherein, the side length of the square ring is 2a, and the line width is w 4 The radius of the circular ring is r, the line width is w 5 ，r＝1.5×a+0.2μm+w 5 ,3μm≤a≤4μm。
5. The terahertz detector based on the double-frequency super-surface wave-absorbing structure according to claim 1, wherein the terahertz detector is characterized in that: the side length of the super surface unit is p 2 ，2r+1μm≤p 2 2r+3 mu m or less; the thickness of the top metal and the bottom metal of the super surface unit is h 2 ，h 2 Between 0.1 and 0.5 μm; the thickness of the dielectric layer and the thickness of the heat insulation cantilever in the super-surface unit are both h 3 ，h 3 Between 0.8 and 2 μm.
6. The terahertz detector based on the double-frequency super-surface wave-absorbing structure according to claim 1, wherein the terahertz detector is characterized in that: the cross section of the silicon substrate is p 1 Is of a thickness h 1 ，h 1 300 μm; square through holes are formed in the silicon substrate, and the side length of each square through hole is w 1 ，w 1 ＝5×p 2 +4μm; the ultra-surface unit array is suspended at the bottom of the silicon substrate by a circumferentially arranged heat-insulating cantilever, and is 5 multiplied by 5The surface unit is opposite to the square through hole in the silicon substrate; the heat insulation cantilever is used for isolating the ultra-surface unit array from the silicon substrate, so that heat loss caused by heat exchange is avoided.
7. The terahertz detector based on the double-frequency super-surface wave-absorbing structure according to claim 1, wherein the terahertz detector is characterized in that: the heat insulation cantilever is made of silicon nitride and is of a square annular structure with one side open, the open end of the heat insulation cantilever is connected with the edges of the two opposite sides of the super-surface unit, and the connection width of the heat insulation cantilever and the super-surface unit is w 2 ，w 2 In the range of 4-8 μm; the heat insulation cantilever is provided with a length w on the arm surface opposite to the opening side 3 Jin Maodian the Jin Maodian is the junction surface of the heat-insulating cantilever and the silicon substrate, w 3 Between 10 and 20 μm; the square ring side length of the heat insulation cantilever is l, l=p 2 ×5+w 2 ×2。
8. The terahertz detector based on the dual-frequency super-surface wave-absorbing structure according to any one of claims 1 to 7, wherein: the detector size parameters are shown in the following table:
9. the terahertz detector based on the double-frequency super-surface wave-absorbing structure according to claim 1, wherein the terahertz detector is characterized in that: the reading module is a thermal infrared imager, the size of an observation area of the thermal infrared imager is 2cm multiplied by 2cm, the spatial resolution is 400 multiplied by 400, the temperature resolution is 50mK, and the response time is 10ms.
10. A transmissive terahertz imaging system, characterized in that: the device comprises a terahertz radiation source, a terahertz optical lens group, a terahertz detector and an infrared thermal imager, wherein a beam emitted by the terahertz radiation source is collimated by the terahertz optical lens group and then enters the terahertz detector, and a temperature distribution image of the plane of the terahertz detector, namely a transmission terahertz imaging of an object to be detected is realized by observing the temperature distribution image of the plane of the terahertz detector through the infrared thermal imager, namely the temperature distribution image is equivalent to the terahertz radiation intensity distribution image;
the plane of the terahertz detector is completely in line with the observation field of view of the thermal infrared imager, and the observation direction of the thermal infrared imager is perpendicular to the plane of the terahertz detector.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211695726.2A CN116242489A (en) | 2022-12-28 | 2022-12-28 | Terahertz detector and system based on double-frequency super-surface wave-absorbing structure |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202211695726.2A CN116242489A (en) | 2022-12-28 | 2022-12-28 | Terahertz detector and system based on double-frequency super-surface wave-absorbing structure |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN116242489A true CN116242489A (en) | 2023-06-09 |
Family
ID=86632187
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202211695726.2A Pending CN116242489A (en) | 2022-12-28 | 2022-12-28 | Terahertz detector and system based on double-frequency super-surface wave-absorbing structure |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN116242489A (en) |
-
2022
- 2022-12-28 CN CN202211695726.2A patent/CN116242489A/en active Pending
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| Glenn et al. | Bolocam: a millimeter-wave bolometric camera | |
| Ruhl et al. | The south pole telescope | |
| JPH0731081B2 (en) | Radiation shield for thermoelectrically cooled infrared detectors | |
| Schwan et al. | Invited Article: Millimeter-wave bolometer array receiver for the Atacama pathfinder experiment Sunyaev-Zel'dovich (APEX-SZ) instrument | |
| Groppi et al. | Test and integration results from SuperCam: a 64-pixel array receiver for the 350 GHz atmospheric window | |
| JP6526876B2 (en) | Spectrum conversion element for electromagnetic radiation | |
| CN101285709A (en) | Opto-mechanics infrared imager based on hartmann wavefront sensor | |
| Reusch et al. | Multipoint Thomson scattering diagnostic for the Madison Symmetric Torus reversed-field pinch | |
| CN102004001B (en) | Millimeter wave multi-pixel refrigeration receiver dewar | |
| US20020021782A1 (en) | Optical assembly for increasing the intensity of a formed X-ray beam | |
| CN116242489A (en) | Terahertz detector and system based on double-frequency super-surface wave-absorbing structure | |
| CN101241231B (en) | Infra red optical imaging device | |
| Naylor et al. | Z-Spec: a broadband direct-detection millimeter-wave spectrometer | |
| CN103592032A (en) | Uncooled infrared imaging focal plane array detector | |
| Kreysa et al. | Bolometer arrays for Mm/Submm astronomy | |
| WO2023060660A1 (en) | Terahertz focal plane imaging detector, imaging system and imaging method | |
| Matsumura et al. | POLARBEAR-2 optical and polarimeter designs | |
| CN103630246A (en) | Non-refrigeration infrared imaging focal plane array detector | |
| CN102650551B (en) | Optical readout method of point grid beamsplitter of FPA (focal plane array)-based uncooled thermal imaging optical system | |
| Grossman et al. | Concealed weapons detection system using uncooled pulsed imaging arrays of millimeter-wave bolometers | |
| CN103630242A (en) | Non-refrigeration infrared imaging focal plane array detector | |
| CN216207066U (en) | Terahertz focal plane imaging system based on thermal infrared imager and super surface | |
| Schwan | The Apex-SZ instrument | |
| CN205538714U (en) | Light and heat weak absorption test system | |
| CN217466684U (en) | Imaging device for phase change process of material |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PB01 | Publication | ||
| PB01 | Publication | ||
| SE01 | Entry into force of request for substantive examination | ||
| SE01 | Entry into force of request for substantive examination |