Material electromagnetic property heterogeneity test system and method

Abstract

The invention discloses a non-uniformity test system and method for electromagnetic properties of a material, and belongs to the technical field of electromagnetic parameter detection of materials. The system comprises a vector network analyzer, a terahertz source module, a terahertz detection module, a diffraction plate, a beam splitter, a semiconductor material, a laser galvanometer, a laser and a computer. According to the system, terahertz wave beams are shaped into large-view-field flat-topped wave beams with uniform irradiation through a diffraction plate; a laser galvanometer is used for controlling a laser spot to accurately scan on a semiconductor material, and a local plasma effect is induced to be generated through dynamic adjustability of the spot size in a sub-wavelength to wavelength range, so that local electromagnetic characteristics are changed; and the electromagnetic parameter distribution of the material is inversely calculated by measuring the change of the scattering parameter S21 in the process. According to the method, rapid screening of heterogeneity of the electromagnetic property of the material and fine analysis of the sub-wavelength resolution in a large view field range are achieved, the diffraction limit of a traditional method is broken through, and the characterization problem of the cross-scale electromagnetic coupling effect is solved.

Description

Technical Field

[0001] This invention belongs to the field of detection and terahertz technology, specifically relating to a test system and method for non-uniformity of electromagnetic properties of materials across a large field of view and wavelength scale. Background Technology

[0002] With the development of high-speed communication, meteorological remote sensing, and advanced electronic devices, new materials such as composite gradient materials, heterogeneous doped systems, and artificial metamaterials have been widely used. During the preparation and use of these materials, the uniformity of their internal electromagnetic properties directly determines the final performance of the devices. Therefore, achieving non-contact, high-resolution testing of the spatial distribution of material electromagnetic parameters (such as dielectric constant and permeability) is crucial.

[0003] However, existing techniques for testing the electromagnetic properties of materials, such as free-space methods, resonant cavity methods, and near-field scanning microscopy, have significant limitations. While free-space methods can test macroscopic samples, they typically require sample sizes much larger than the wavelength and struggle to achieve subwavelength resolution. Near-field microscopy, although capable of overcoming the diffraction limit, usually suffers from a narrow field of view and low scanning efficiency, failing to meet the demands for rapid detection of large-size samples. These techniques share a common "scale discontinuity" problem: they cannot achieve continuous, dynamic measurements between macroscopic large fields of view and microscopic subwavelength resolution, thus hindering the accurate characterization of cross-scale electromagnetic coupling effects in new materials.

[0004] Therefore, there is an urgent need in this field for a material electromagnetic property inhomogeneity testing technology and system that can take into account a large field of view, high resolution and rapid detection capability. Summary of the Invention

[0005] To address the aforementioned technical problems in the existing technology, this invention proposes a material electromagnetic property non-uniformity testing system and method to achieve cross-scale continuous testing and high-resolution imaging of material electromagnetic properties. The system is rationally designed, overcomes the shortcomings of the existing technology, and has good performance.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A material electromagnetic property inhomogeneity testing system includes a vector network analyzer, a terahertz source module, a terahertz detection module, a diffraction plate, a beam splitter, a semiconductor material, a laser galvanometer, a laser, and a computer; The vector network analyzer, operating at frequencies from 10MHz to 26.5GHz, is configured to provide RF and local oscillator signals to the terahertz source module and local oscillator signals to the terahertz detection module, while simultaneously acquiring scattering parameters S based on reference and test signals. 21 ; The terahertz source module includes frequency doubling links and frequency mixing links, which are interconnected via directional couplers; The frequency doubling link is configured to generate a terahertz signal by frequency doubling and amplification under RF signal excitation, and radiate it into free space through an antenna; a directional coupler couples a portion of the terahertz signal to the mixing link; The mixing link is configured to downmix the coupled terahertz signal to obtain a reference signal under local oscillator excitation and transmit it to the vector network analyzer via a coaxial cable; The diffraction plate is configured to beam-shape the radiated terahertz signal to form a uniformly distributed terahertz radiation field. The radiation area is circular or square, and the diameter of the circular area or the side length of the square area is 200 mm. Beam splitter is configured to radiate a shaped terahertz beam onto the surface of the material under test; Semiconductor materials, attached to the material under test, are configured to generate a plasma effect under laser excitation, radiating terahertz signals; A laser is configured to generate a high-power laser signal, which is radiated onto the surface of a semiconductor material via a laser galvanometer. The laser galvanometer is configured to control the size of the laser spot within the range of 0.1 to 1 terahertz signal wavelength and to control the laser beam to scan the semiconductor material region corresponding to the material under test. The terahertz detection module is configured to receive the terahertz signal reflected from the material under test, and mix it with the terahertz signal reflected from the sample under test under the excitation of the local oscillator signal to obtain the test signal. The test signal is transmitted to the vector network analyzer through a coaxial cable. The computer is configured to control the vector network analyzer, laser, and laser galvanometer, based on the scattering parameter S. 21 Calculate the electromagnetic parameters and their distribution of the material under test to achieve high-resolution imaging at the subwavelength scale.

[0007] Preferably, the semiconductor material includes silicon, germanium, or indium phosphide.

[0008] Preferably, the diameter of the radiation area is 200 mm when it is circular, and the side length is 200 mm when it is square.

[0009] Preferably, the laser galvanometer is configured to control the laser spot size to be continuously adjustable within the range of 0.1 to 1 terahertz signal wavelength, and the scanning step is programmable.

[0010] Preferably, the terahertz source module and the terahertz detection module adopt a transmit-receive separation mode, with the terahertz detection module set up independently to receive the reflected signal.

[0011] Furthermore, this invention also provides a method for testing the non-uniformity of electromagnetic properties of materials. This method employs the material electromagnetic property non-uniformity testing system described above, and is characterized by comprising the following steps: Step 1: Test preparation. Power on all hardware devices in the system and preheat them for 30 minutes. Step 2: Quick test, including: Step 2.1: Set the test parameters, including the operating frequency and signal power of the vector network analyzer, terahertz source module, and terahertz detection module; set the laser parameters; and set the laser galvanometer motion parameters so that the laser spot size is approximately one terahertz signal wavelength. Step 2.2: Attach the sample to be tested to the semiconductor material and place it at the test position. With the laser and laser galvanometer not working, use a vector network analyzer to collect the scattering parameter S. 21 ; Step 2.3: Turn on the laser, irradiate the semiconductor material, control the laser galvanometer to move the spot position, traverse the entire test area, and record the S corresponding to each position in real time. 21i ; Step 2.4: Transfer each S 21i With S 21 Normalization operation yields A i Based on A i Electromagnetic parameter B was calculated using a numerical iteration method. i and to B i Normalization is performed to obtain C i Analyze the uniformity of electromagnetic properties, if C i If singularities are found, a more refined test will be performed. Step 3: Refined testing, including: Step 3.1: Set the test parameters so that the laser spot size is within the range of 0.1 to less than 1 terahertz signal wavelength; Step 3.2: Attach the sample to be tested to the semiconductor material and place it at the test position. When the laser and laser galvanometer are not working, collect the scattering parameter S. 21 ; Step 3.3: Turn on the laser, irradiate the semiconductor material, control the laser galvanometer to move the spot position to traverse the target area, and record the S corresponding to each position in real time. 21i ; Step 3.4: Transfer each S 21i With S 21 Normalization operation yields A i Based on A i Electromagnetic parameter B was calculated using a numerical iteration method. i and to B i Normalization is performed to obtain C i Analyze the distribution of electromagnetic properties to locate the position and type of defects; Step 4: Output the detection results and end the test.

[0012] Preferably, the normalization operation is A i = S 21i / S 21 .

[0013] Preferably, the normalization process is C i = {B i - mean[B i ]} / {max[B i ] - mean[B i ]}, where mean[B i ] is B i The average value, max[B i ] is B i The maximum value.

[0014] Preferably, in both rapid and refined testing, the scanning trajectory of the laser spot covers the entire testing area, and the scanning speed can be adjusted.

[0015] Preferably, cross-wavelength scale testing is achieved by varying the size of the laser spot, and the imaging resolution is related to the size of the laser spot, thus breaking the diffraction limit.

[0016] The beneficial technical effects of this invention are as follows: (1) A terahertz flat-top beam is used to achieve uniform radiation of a large field of view (circular area diameter 200mm, square area side length 200mm) of material, which solves the problem of limited radiation area and uneven signal energy distribution in the radiation area of ​​traditional terahertz antennas. (2) High-energy lasers are used to excite semiconductor materials to generate plasma effects and radiate terahertz signals, which causes changes in the electromagnetic field within the terahertz beam radiation area. By detecting the changes in the electromagnetic field caused by the terahertz signals generated by the plasma, the electromagnetic properties and distribution of the materials can be tested. (3) By using a galvanometer, the size of the laser spot can be rapidly changed and the position can be moved at high speed, thus quickly covering the scanning area. This enables high-resolution imaging of materials. The imaging resolution is only related to the size of the laser spot and is not related to the wavelength of the microwave, millimeter wave, or terahertz wave signal. This can break through the diffraction limit and achieve high-resolution imaging with wavelength compression. (4) The use of terahertz transceiver separation mode realizes high sensitivity detection of weak terahertz signals from plasma radiation, which solves the problem of insufficient dynamics in commonly used transceiver modules. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the structure of the testing system provided in an embodiment of the present invention.

[0018] Figure 2 This is a schematic diagram of a circular, large field-of-view lighting area.

[0019] Figure 3 This is a schematic diagram of a square, large field-of-view lighting area.

[0020] Figure 4 This is a flowchart of the method of the present invention. Detailed Implementation

[0021] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments: like Figure 1 As shown, the test system of the present invention includes a vector network analyzer, a terahertz source module, a terahertz detection module, a diffraction plate, a beam splitter, semiconductor materials, a laser galvanometer, a laser, and a computer.

[0022] The vector network analyzer operates at frequencies ranging from 10MHz to 26.5GHz. Its functions include: 1) providing RF and local oscillator signals to the terahertz source module, and simultaneously providing a local oscillator signal to the terahertz detection module; 2) obtaining S based on the reference signal from the terahertz source module and the test signal from the terahertz detection module. 21 ; The terahertz source module consists of a frequency doubling link and a frequency mixing link, which are interconnected by a single fixed coupler. Under the excitation of the RF signal of the vector network analyzer, the terahertz source link generates a terahertz signal through frequency doubling, amplification, and frequency multiplication. The terahertz signal is transmitted to the terahertz antenna port through the directional coupler and radiated into free space by the antenna. While transmitting the terahertz signal, the directional coupler also couples a signal to the mixer of the frequency mixing link. Under the excitation of the local oscillator signal of the vector network analyzer, the frequency mixing link mixes the terahertz signal coupled to the directional coupler to obtain a reference signal. The reference signal is obtained by the vector network analyzer through a coaxial cable and is denoted as R. The terahertz signal radiated into free space is beam-shaped by a diffracting plate to obtain a uniformly distributed terahertz radiation field. The radiation region can be selected as a square or circular area as needed, such as... Figure 2 and Figure 3 As shown; The shaped terahertz beam is radiated onto the surface of the material under test via a beam splitter. The material under test is tightly bonded to the semiconductor material, which can be silicon, germanium, indium phosphide, etc. The role of the semiconductor material is that, under the excitation of high-energy laser, electron-hole pairs are generated, which diffuse across the irradiation spot to form a plasma region, causing a significant local increase in conductivity and radiating an ultra-wideband terahertz signal. Since the laser spot size can be rapidly switched at a subwavelength scale smaller than microwave-terahertz, a plasma region that breaks the diffraction limit is formed. The size of the region can be rapidly adjusted by controlling the size of the laser spot. The function of a laser is to generate a high-power laser signal, which is then radiated onto the surface of a semiconductor material through a laser galvanometer. The functions of a laser galvanometer include: first, controlling the rapid change of the laser spot size within a terahertz signal wavelength range (0.1-1) according to testing requirements; and second, controlling the laser beam to rapidly scan the region of semiconductor material corresponding to the size of the test material according to a set path, such as... Figure 4 As shown; The terahertz signal reflected by the test sample passes through a beam splitter, diffraction plate, and terahertz antenna, and is detected by the terahertz detection module. Excited by the local oscillator signal of the vector network analyzer, the terahertz detection module mixes the reflected terahertz signal with the signal from the test sample to obtain a test signal. This test signal is then transmitted via a coaxial cable to the vector network analyzer and denoted as A. The vector network analyzer obtains the scattering parameter S21 based on the test signal A and the reference signal R. The computer's functions include: first, controlling the normal operation of equipment such as vector network analyzers, lasers, and laser galvanometers; and second, calculating the electromagnetic parameters of the material under test and the distribution of its electromagnetic properties based on the collected S21 data to obtain high-resolution imaging at the wavelength scale.

[0023] A method for analyzing the non-uniformity of electromagnetic properties of materials across a large field of view and wavelength scale, the process is as follows: Figure 4 As shown, it includes the following steps: Step 1, Test Preparation: Power on all hardware devices in the system and preheat them for 30 minutes.

[0024] Step 2, Quick test parameter settings: Set the operating frequency, signal power, and other test parameters of the vector network analyzer, source module, and terahertz detection module according to actual needs; set the laser parameters; set the motion parameters of the laser galvanometer so that the laser spot size is approximately on the order of one wavelength of the signal in the test frequency band, so as to achieve rapid testing of electromagnetic properties and their distribution. The test sample is attached to the selected semiconductor material and placed at the test position; with the laser and laser galvanometer inactive, the scattering parameters S under this condition are acquired using a vector network analyzer. 21 ; Turn on the laser to irradiate the semiconductor material, and set the starting position of the laser irradiation to (x). 0， y0), the termination position is (x n y n The laser galvanometer rapidly moves the spot position, traversing the entire test area. For a specific location, the vector network analyzer records the corresponding S in real time. 21i (i=0,1,…,n); After data collection is completed, S is respectively... 21i (i=0,1,…,n) and S 21 Perform normalization, denoted as A.i (i=0,1,…,n)=S 21i (i=0,1,…,n) / S 21 Based on A i (i=0,1,…,n), the electromagnetic parameters at all locations within the material testing area can be obtained using a numerical iteration method; B i The obtained electromagnetic parameters (i=0,1,…,n) are normalized, i.e., C i (i=0,1,…,n)={B i (i=0,1,…,n)-mean[Bi (i=0,1,…,n)]} / {max[B i (i=0,1,…,n)]-mean[Bi(i=0,1,…,n)]}; This can be used to obtain the uniformity of the electromagnetic properties of the material in the test area; If there are singularities in Ci, then the target area corresponding to Ci is subjected to refined testing; Step 3, refine test parameter settings: accurately analyze the depth of the defect within the material, the size of the defect, and the type of defect.

[0025] Set the operating frequency, signal power, and other test parameters of the vector network analyzer, source module, and terahertz detection module according to actual needs; set the laser parameters; set the motion parameters of the laser galvanometer so that the laser spot size is approximately on the subwavelength order of the signal in the test frequency band (selected between 0.1 wavelength and less than 1 wavelength) to achieve accurate testing of electromagnetic properties and their distribution. The test sample is attached to the selected semiconductor material and placed at the test position; with the laser and laser galvanometer inactive, the scattering parameters S under this condition are acquired using a vector network analyzer. 21 ; Turn on the laser to irradiate the semiconductor material, and set the starting position of the laser irradiation to (x). o， y o The ending position is (x) p y p The laser galvanometer rapidly moves the spot position, traversing the entire test area. For a specific location, the vector network analyzer records the corresponding S in real time. 21i (i=o,…,p); After data collection is completed, S is respectively... 21i (i=o,…,p) and S 21 Perform normalization, denoted as A. i (i=o,…,p)=S 21i (i=o,…,p) / S 21 Based on A i (i=o,,p), the electromagnetic parameters at all locations within the material testing area can be obtained using a numerical iteration method; Bi The obtained electromagnetic parameters (i=o,…,p) are normalized, i.e., C i (i=o,…,p)={B i (i=o,…,p)-mean[Bi (i=o,…,p)]} / {max[B i (i=o,…,p)]-mean[Bi(i=o,…,p)]}; This allows us to obtain the uniformity of the electromagnetic properties of the material within the test area, and to locate the defect location and possible defect type based on the refined electromagnetic properties of the test area; Step four, test complete.

[0026] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A system for testing the non-uniformity of electromagnetic properties of materials, characterized in that, It includes a vector network analyzer, a terahertz source module, a terahertz detection module, a diffraction plate, a beam splitter, semiconductor materials, a laser galvanometer, a laser, and a computer; The vector network analyzer, operating at frequencies from 10MHz to 26.5GHz, is configured to provide RF and local oscillator signals to the terahertz source module and local oscillator signals to the terahertz detection module, while simultaneously acquiring scattering parameters S based on reference and test signals. 21 ; The terahertz source module includes frequency doubling links and frequency mixing links, which are interconnected via directional couplers; The frequency doubling link is configured to generate terahertz signals by frequency doubling and amplification under the excitation of radio frequency signals, and radiate them into free space through an antenna; A directional coupler couples a portion of the terahertz signal to the mixer link; The mixing link is configured to downmix the coupled terahertz signal to obtain a reference signal under local oscillator excitation and transmit it to the vector network analyzer via a coaxial cable; The diffraction plate is configured to beam-shape the radiated terahertz signal to form a uniformly distributed terahertz radiation field. The radiation area is circular or square, and the diameter of the circular area or the side length of the square area is 200 mm. Beam splitter is configured to radiate a shaped terahertz beam onto the surface of the material under test; Semiconductor materials, attached to the material under test, are configured to generate a plasma effect under laser excitation, radiating terahertz signals; A laser is configured to generate a high-power laser signal, which is radiated onto the surface of a semiconductor material via a laser galvanometer. The laser galvanometer is configured to control the size of the laser spot within the range of 0.1 to 1 terahertz signal wavelength and to control the laser beam to scan the semiconductor material region corresponding to the material under test. The terahertz detection module is configured to receive the terahertz signal reflected from the material under test, and mix it with the terahertz signal reflected from the sample under test under the excitation of the local oscillator signal to obtain the test signal. The test signal is transmitted to the vector network analyzer through a coaxial cable. The computer is configured to control the vector network analyzer, laser, and laser galvanometer, based on the scattering parameter S. 21 Calculate the electromagnetic parameters and their distribution of the material under test to achieve high-resolution imaging at the subwavelength scale.

2. The material electromagnetic property non-uniformity testing system according to claim 1, characterized in that, Semiconductor materials include silicon, germanium, or indium phosphide.

3. The material electromagnetic property non-uniformity testing system according to claim 1, characterized in that, The diameter of the radiation area is 200mm when it is circular, and the side length is 200mm when it is square.

4. The material electromagnetic property non-uniformity testing system according to claim 1, characterized in that, The laser galvanometer is configured to control the laser spot size to be continuously adjustable within the range of 0.1 to 1 terahertz signal wavelength, and the scanning step is programmable.

5. The material electromagnetic property non-uniformity testing system according to claim 1, characterized in that, The terahertz source module and the terahertz detection module adopt a transmit-receive separation mode, with the terahertz detection module set up independently to receive reflected signals.

6. A method for testing the non-uniformity of electromagnetic properties of materials, employing the material electromagnetic property non-uniformity testing system as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Test preparation. Power on all hardware devices in the system and preheat them for 30 minutes. Step 2: Quick test, including: Step 2.1: Set the test parameters, including the operating frequency and signal power of the vector network analyzer, terahertz source module, and terahertz detection module; set the laser parameters; and set the laser galvanometer motion parameters so that the laser spot size is approximately one terahertz signal wavelength. Step 2.2: Attach the sample to be tested to the semiconductor material and place it at the test position. With the laser and laser galvanometer not working, use a vector network analyzer to collect the scattering parameter S. 21 ; Step 2.3: Turn on the laser, irradiate the semiconductor material, control the laser galvanometer to move the spot position, traverse the entire test area, and record the S corresponding to each position in real time. 21i ; Step 2.4: Transfer each S 21i With S 21 Normalization operation yields A i Based on A i Electromagnetic parameter B was calculated using a numerical iteration method. i and to B i Normalization is performed to obtain C i Analyze the uniformity of electromagnetic properties, if C i If singularities are found, a more refined test will be performed. Step 3: Refined testing, including: Step 3.1: Set the test parameters so that the laser spot size is within the range of 0.1 to less than 1 terahertz signal wavelength; Step 3.2: Attach the sample to be tested to the semiconductor material and place it at the test position. When the laser and laser galvanometer are not working, collect the scattering parameter S. 21 ; Step 3.3: Turn on the laser, irradiate the semiconductor material, control the laser galvanometer to move the spot position to traverse the target area, and record the S corresponding to each position in real time. 21i ; Step 3.4: Transfer each S 21i With S 21 Normalization operation yields A i Based on A i Electromagnetic parameter B was calculated using a numerical iteration method. i and to B i Normalization is performed to obtain C i Analyze the distribution of electromagnetic properties to locate the position and type of defects; Step 4: Output the test results and end the test.

7. The method for testing the non-uniformity of electromagnetic properties of materials according to claim 6, characterized in that, Normalization operation is A i = S 21i / S 21 .

8. The method for testing the non-uniformity of electromagnetic properties of materials according to claim 6, characterized in that, Normalization to C i = {B i - mean[B i ]} / {max[B i ] - mean[B i ]}, where mean[B i ] is B i The average value, max[B i ] is B i The maximum value.

9. The method for testing the non-uniformity of electromagnetic properties of materials according to claim 6, characterized in that, In both rapid and refined testing, the scanning trajectory of the laser spot covers the entire testing area, and the scanning speed can be adjusted.

10. The method for testing the non-uniformity of electromagnetic properties of materials according to claim 6, characterized in that, By varying the size of the laser spot, cross-wavelength scale testing is achieved, and the imaging resolution is related to the size of the laser spot, thus breaking the diffraction limit.

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