A gas refractive index measuring device based on a metasurface

Abstract

This invention relates to a gas refractive index measurement device based on a metasurface, belonging to the field of refractive index measurement technology. It includes: a first metal rectangular waveguide with a first flange at one end, the first flange having a first rectangular opening, and a cylindrical hole communicating with its inner wall on the outer wall of the first metal rectangular waveguide; a second metal rectangular waveguide with a second flange at one end, the second flange having a second rectangular opening; the first and second flanges having the same shape and size, and the first and second rectangular openings having the same shape and size; a metasurface disposed within the first metal rectangular waveguide; and a vector network analyzer connected to the other end of the second metal rectangular waveguide, used to detect the refractive index of the gas within the waveguide merge when the first and second metal rectangular waveguides are combined to form a waveguide merge. This invention enables accurate measurement of gas refractive index.

Description

Technical Field

[0001] This invention relates to the field of gas refractive index measurement technology, and in particular to a gas refractive index measurement device based on a metasurface. Background Technology

[0002] Refractive index is a fundamental physical quantity characterizing the optical properties of a material, directly affecting its synthesis, manufacturing, and applications in various fields. It is a key parameter in optical device design, chemical analysis, and biological detection. Existing refractive index detection technologies include:

[0003] Gas refractive index measurement related technologies: optical interferometry (inverts the refractive index change by measuring the amount of movement of interference fringes after the introduction of gas, but requires a complex and precise optical system structure, a stable vibration isolation platform and a constant temperature environment, and is extremely sensitive to environmental disturbances); surface plasmon resonance method (requires expensive precious metal (such as gold) sensing chips, complex optical path coupling systems and precise angle or wavelength scanning mechanisms, the system cost is high and it is easy to be contaminated).

[0004] However, in pursuit of high precision, traditional refractive index measurement techniques often sacrifice system simplicity, robustness, and cost-effectiveness, failing to balance laboratory-level accuracy with the convenience required for field applications, thus limiting their use in scenarios such as biochemical analysis and on-site quality inspection. Furthermore, traditional high-precision gas refractive index measurement devices are extremely sensitive to minute changes in the refractive index of the medium, but the system costs are high, and the sensor chips are prone to contamination and have limited lifespan, making them unsuitable for long-term, online industrial monitoring.

[0005] Therefore, developing a gas refractive index measuring device that is simple in structure, easy to operate, and has high-precision measurement capabilities is of great significance for promoting technological progress in related industries and reducing testing costs. Summary of the Invention

[0006] Therefore, the technical problem to be solved by the present invention is to overcome the problems of complex structure, high cost and unsuitability for long-term, online industrial monitoring of gas refractive index measuring devices in the prior art.

[0007] To address the aforementioned technical problems, this invention provides a gas refractive index measuring device based on a metasurface, comprising:

[0008] A first metal rectangular waveguide, one end of which is provided with a first flange, the first flange having a first rectangular opening, and the outer wall of the first metal rectangular waveguide having a cylindrical hole communicating with its inner wall.

[0009] A second metal rectangular waveguide, one end of which is provided with a second flange, and the second flange has a second rectangular opening;

[0010] The first flange and the second flange have the same shape and size, and the first rectangular opening and the second rectangular opening have the same shape and size;

[0011] Metasurface, wherein the metasurface is disposed in the first metallic rectangular waveguide;

[0012] A vector network analyzer, connected to the other end of a second metal rectangular waveguide, is used to detect the refractive index of the gas within the waveguide merger when the first and second metal rectangular waveguides are combined to form a waveguide merger.

[0013] The waveguide assembly is operated in a high-order transverse magnetic wave mode. The vector network analyzer excites a transverse magnetic wave into the waveguide assembly. Near the cutoff frequency of the transverse magnetic wave, the reflectivity of the metasurface rapidly decays and reaches a minimum. The gas to be tested is introduced into the first metal rectangular waveguide through a cylindrical hole. The frequency corresponding to the minimum reflectivity of the metasurface will shift. The shift of this frequency is measured by the vector network analyzer, and the refractive index value of the gas to be tested is calculated based on the shift.

[0014] In one embodiment of the present invention, the metasurface is coated on the inner wall surface of the first metallic rectangular waveguide.

[0015] In one embodiment of the present invention, the straight-line distance between the cylindrical hole and the first flange is less than the distance between the metasurface and the first flange.

[0016] In one embodiment of the present invention, the operating frequency range of the first metal rectangular waveguide and the second metal rectangular waveguide is 0.1 GHz to 50 GHz.

[0017] In one embodiment of the invention, the metasurface is made of copper, aluminum, or a material with electrical conductivity of [missing information]. It is made of any one of the materials in the doped silicon wafer.

[0018] In one embodiment of the present invention, when the transverse magnetic wave excited by the vector network analyzer is at a preset grazing angle When a waveguide composite formed by a first and a second metallic rectangular waveguide is incident on the metasurface, the reflectivity of the metasurface reaches a minimum if the operating frequency of the waveguide composite and the conductivity of the metasurface satisfy the following formula:

[0019] ;

[0020] in, The electrical conductivity of the metasurface, Angular frequency and , It is the operating frequency of the waveguide assembly. is the vacuum permittivity.

[0021] In one embodiment of the present invention, the preset grazing angle The scope is: .

[0022] In one embodiment of the present invention, in the waveguide combination formed by the first and second metallic rectangular waveguides, when the higher-order mode transverse magnetic wave operates near the cutoff frequency, the higher-order mode transverse magnetic wave is approximately equivalent to four plane waves with a preset grazing angle. When incident on a metasurface, the conductivity of the metasurface... The frequency corresponding to the minimum reflectivity of the metasurface actually observed in the waveguide assembly. The following relationship must be satisfied:

[0023] ;

[0024] in, The vacuum permittivity, It is the operating frequency of the waveguide assembly, and also the frequency corresponding to the minimum reflectivity. This is the cutoff frequency for higher-order transverse magnetic wave modes within the waveguide merging body.

[0025] In one embodiment of the present invention, the cutoff frequency The structural dimensions of the first rectangular opening of the first flange and the mode order of the transverse magnetic wave propagating within the waveguide assembly are related, and are expressed as follows:

[0026] ;

[0027] in, It is the speed of light in a vacuum. It is the refractive index of the gas inside the waveguide. and These are the width and narrow side dimensions of the first rectangular opening of the first metallic rectangular waveguide, respectively. and They are transverse magnetic waves The order of the pattern.

[0028] In one embodiment of the present invention, when the refractive index of the gas within the waveguide assembly changes, the frequency corresponding to the minimum reflectivity of the metasurface will be affected. The offset satisfies the following relationship:

[0029] ;

[0030] in, This represents the change in the refractive index of the gas. This represents the change in the frequency of the minimum reflectivity within the waveguide merging body caused by the change in the refractive index of the corresponding gas.

[0031] Compared with the prior art, the above-described technical solution of the present invention has the following advantages:

[0032] The gas refractive index measuring device based on metasurface described in this invention can effectively and accurately measure the refractive index of gases. The gas refractive index measuring device constructed in this invention has a simple structure and can meet the needs of laboratory-level accuracy and convenient field application, effectively improving its application in biochemical analysis, on-site quality inspection and other scenarios.

[0033] The gas refractive index measurement device based on metasurface constructed in this invention has low cost, long service life, and is suitable for long-term, online industrial monitoring. Attached Figure Description

[0034] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0035] Figure 1 This is a schematic diagram of the overall structure of the gas refractive index measuring device based on metasurface in an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of a metal rectangular waveguide structure in an embodiment of the present invention;

[0037] Figure 3 In the air-filled waveguide of this embodiment of the invention A schematic diagram of the reflectance curve of the mode;

[0038] Figure 4 This is the mode under minute changes in refractive index in the embodiments of the present invention. A schematic diagram of reflectivity curves and frequency shifts;

[0039] Figure 5 In this embodiment of the invention, the metasurface is taken as copper, using a standard BJ120 waveguide. A schematic diagram of the reflectivity curve and frequency shift of the mode;

[0040] Figure 6 In this embodiment of the invention, the metasurface is taken as aluminum, using a standard BJ120 waveguide. A schematic diagram of the reflectivity curve and frequency shift of the mode. Detailed Implementation

[0041] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0042] Example 1

[0043] Reference Figure 1 and Figure 2 As shown, the present invention relates to a gas refractive index measuring device based on a metasurface, comprising:

[0044] A first metal rectangular waveguide 1-1, one end of which is provided with a first flange 2-1, the first flange 2-1 having a first rectangular opening 3-1, and the outer wall of the first metal rectangular waveguide 1-1 having a cylindrical hole 6 communicating with its inner wall.

[0045] A second metal rectangular waveguide 1-2, one end of which is provided with a second flange 2-2, and the second flange 2-2 has a second rectangular opening 3-2;

[0046] The first flange 2-1 and the second flange 2-2 have the same shape and size, and the first rectangular opening 3-1 and the second rectangular opening 3-2 have the same shape and size;

[0047] Metasurface 4 is disposed in the first metallic rectangular waveguide 1-1;

[0048] Vector network analyzer 5, which is connected to the other end of the second metal rectangular waveguide 1-2, is used to detect the refractive index of the gas in the waveguide merge when the first metal rectangular waveguide 1-1 and the second metal rectangular waveguide 1-2 are merged to form a waveguide merge.

[0049] The waveguide assembly is operated in a higher-order transverse magnetic wave mode (higher-order transverse magnetic wave mode is...) , ,For example , The vector network analyzer 5 excites a transverse magnetic wave into the waveguide and the body. At the cutoff frequency of the transverse magnetic wave, the reflectivity of the metasurface 4 rapidly decays and reaches a minimum value. The gas to be tested is introduced into the first metal rectangular waveguide 1-1 through the cylindrical hole 6. The frequency corresponding to the minimum reflectivity of the metasurface 4 will shift. The vector network analyzer 5 measures the shift of this frequency and calculates the refractive index value of the gas to be tested based on the shift.

[0050] The following is a detailed description of this embodiment:

[0051] Furthermore, in this embodiment, the metasurface 4 is coated on the inner wall surface of the first metal rectangular waveguide 1-1. To ensure detection performance, the metasurface 4 can be coated on all four sides of the inner wall of the first metal rectangular waveguide 1-1. Figure 2The metasurface 4 in the first metal rectangular waveguide 1-1 is rectangular on each of the four sides of the inner wall.

[0052] Furthermore, in this embodiment, the shortest straight-line distance between the cylindrical hole 6 and the first flange 2-1 is less than the shortest straight-line distance between the metasurface 4 and the first flange 2-1. In short, from... Figure 2 It is not difficult to see that the cylindrical hole 6 is closer to the first flange 2-1 than the metasurface 4. The purpose is to allow the transverse magnetic wave excited by the vector network analyzer 5 to pass through the gas to be measured first, and then through the metasurface 4. Otherwise, the transverse magnetic wave excited by the vector network analyzer 5 will not undergo a change in reflectivity frequency shift.

[0053] Furthermore, the operating frequency range of the first metal rectangular waveguide 1-1 and the second metal rectangular waveguide 1-2 in this embodiment is 0.1GHz-50GHz.

[0054] Furthermore, the metasurface 4 in this embodiment is made of copper, aluminum, or a material with electrical conductivity of [missing information]. It is made of any one of the materials in the doped silicon wafer.

[0055] To more clearly demonstrate the physical mechanism of high-precision gas refractive index measurement in the first metallic rectangular waveguide 1-1, the following combines... Figure 2 To elaborate in detail.

[0056] When the transverse magnetic wave excited by the vector network analyzer 5 grazes at a preset angle ( When a waveguide composite formed by the first metallic rectangular waveguide 1-1 and the second metallic rectangular waveguide 1-2 is incident on the metasurface 4, if the operating frequency of the waveguide composite and the conductivity of the metasurface 4 satisfy the following formula, then the reflectivity of the metasurface 4 reaches a minimum (i.e., ):

[0057]

[0058] In the waveguide assembly formed by the first metallic rectangular waveguide 1-1 and the second metallic rectangular waveguide 1-2, the propagation of the higher-order mode transverse magnetic wave is equivalent to the superposition of four plane waves. When the higher-order mode transverse magnetic wave operates near the cutoff frequency, it is approximated as four plane waves with a preset grazing angle. When incident on metasurface 4, the electrical conductivity of metasurface 4 is... The frequency corresponding to the actual observed minimum reflectivity in the waveguide assembly The following relationship must be satisfied:

[0059]

[0060] in, The vacuum permittivity, It is the operating frequency of the waveguide assembly, and also the frequency corresponding to the minimum reflectivity. This is the cutoff frequency for higher-order transverse magnetic wave modes within the waveguide merging body.

[0061] Furthermore, cutoff frequency The structural dimensions of the first rectangular opening 3-1 of the first flange 2-1 and the mode order of the transverse magnetic wave propagating within the waveguide assembly are related, and are expressed as follows:

[0062]

[0063] in, It is the speed of light in a vacuum. It is the refractive index of the gas inside the waveguide. and These are the width and narrow side dimensions of the cross-section of the first metallic rectangular waveguide 1-1 (i.e., the first rectangular opening 3-1 opened in the first flange 2-1). and They are transverse magnetic waves The order of the pattern. It should be noted that the above... The formula can also be used to describe the refractive index of the gas inside the waveguide. The inversion formula.

[0064] Based on the above mechanism, when the refractive index of the gas within the waveguide assembly changes, it will cause the frequency corresponding to the minimum reflectivity of the metasurface 4 to change. The offset satisfies the following relationship to achieve high-sensitivity and high-precision measurement of the gas refractive index:

[0065]

[0066] in, This represents the change in the refractive index of the gas. This represents the change in the frequency of the minimum reflectivity within the waveguide merging body caused by the change in the refractive index of the corresponding gas.

[0067] Specific examples are as follows:

[0068] In a specific implementation example, to verify the accuracy and performance of the gas refractive index measurement device based on metasurface in this embodiment, a test system was constructed. This system employs a first metallic rectangular waveguide 1-1 and a second metallic rectangular waveguide 1-2 conforming to Chinese national standard BJ58, the wide side dimensions of the first rectangular opening 3-1 of the first flange 2-1, and the second rectangular opening 3-2 of the second flange 2-2. Narrow side size The inner wall of the first metallic rectangular waveguide 1-1 is coated with a metasurface 4 (conductivity). Under standard environmental conditions (temperature 20°C, air pressure 101.325 kPa), measurements were first taken using dry air as the reference medium, and its refractive index was approximately... By exciting transverse magnetic waves By scanning the higher-order modes and frequencies, a distinct minimum point can be observed in the reflectance curve, and its corresponding characteristic frequency is precisely determined to be... , specifically Figure 3 As shown, this frequency value will serve as the normalization reference for subsequent measurements of refractive index changes.

[0069] To verify the accuracy characteristics of the gas refractive index measurement device based on metasurface proposed in this embodiment, this embodiment achieves accurate measurement of the refractive index change of the medium by monitoring the shift of the minimum frequency point in the reflectivity curve. For example... Figure 4 As shown, when the change in the refractive index of the medium is approximately The system can clearly and stably detect the corresponding characteristic frequency shift. The experimental results are in high agreement with the calculated values ​​of the aforementioned theoretical formula, thus verifying the effectiveness and accuracy of the device in this embodiment in achieving high-precision and high-sensitivity refractive index measurement.

[0070] To demonstrate the tunability of the above-mentioned gas refractive index measurement device based on metasurfaces at the operating frequency, this embodiment can also achieve this by changing the rectangular waveguides of different sizes. For example, the system uses a first metallic rectangular waveguide 1-1 and a second metallic rectangular waveguide 1-2 conforming to Chinese national standard BJ120, with the width dimensions of the first rectangular opening 3-1 and the second rectangular opening 3-2 being... Narrow side size Using conductivity Metasurface 4 (material: copper). Benchmark measurements were performed on dry air medium under standard environmental conditions (temperature 20°C, air pressure 101.325 kPa) (see [reference]). Figure 5 (a) in the text) and high-precision measurement of minute changes in the refractive index of the medium ( (See also) Figure 5 (b)). The results further validate the frequency adaptability and measurement reliability of this embodiment.

[0071] In specific implementation, the metasurface 4 used in the above embodiments, although taking copper as an example (conductivity) However, material selection offers flexibility in actual design and production. For example, in this embodiment, lighter and lower-cost aluminum can also be used as the coating material (electrical conductivity). The system also employs a first metallic rectangular waveguide 1-1 and a second metallic rectangular waveguide 1-2 conforming to Chinese national standard BJ120, and uses a metasurface 4 made of aluminum. Reference measurements were performed on dry air medium under standard environmental conditions (temperature 20°C, air pressure 101.325 kPa) (see [link to relevant documentation]). Figure 6 (a) in the middle) and for small changes in refractive index ( High-sensitivity measurement (see [link]) Figure 6 (b)). The results all show that the system still has excellent measurement performance and stability under the aluminum coating.

[0072] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A gas refractive index measuring device based on a metasurface, characterized in that, include: A first metal rectangular waveguide (1-1) is provided at one end of a first flange (2-1), the first flange (2-1) has a first rectangular opening (3-1), and the outer wall of the first metal rectangular waveguide (1-1) is provided with a cylindrical hole (6) communicating with its inner wall. A second metal rectangular waveguide (1-2) is provided at one end of the second metal rectangular waveguide (1-2), and a second flange (2-2) is provided at the second flange (2-2). The first flange (2-1) and the second flange (2-2) are the same in shape and size, and the first rectangular opening (3-1) and the second rectangular opening (3-2) are the same in shape and size; Metasurface (4) is disposed in the first metallic rectangular waveguide (1-1); Vector network analyzer (5), which is connected to the other end of the second metal rectangular waveguide (1-2), is used to detect the refractive index of the gas in the waveguide merge when the first metal rectangular waveguide (1-1) and the second metal rectangular waveguide (1-2) are merged to form a waveguide merge; The waveguide assembly is operated in a high-order transverse magnetic wave mode. The vector network analyzer (5) excites a transverse magnetic wave into the waveguide assembly. At the cutoff frequency of the transverse magnetic wave, the reflectivity of the metasurface (4) rapidly decays and reaches a minimum value. The gas to be tested is introduced into the first metal rectangular waveguide (1-1) through the cylindrical hole (6). The frequency corresponding to the minimum reflectivity of the metasurface (4) will shift. The shift of this frequency is measured by the vector network analyzer (5), and the refractive index value of the gas to be tested is calculated based on the shift.

2. The gas refractive index measuring device based on metasurface according to claim 1, characterized in that: The metasurface (4) is coated on the inner wall surface of the first metal rectangular waveguide (1-1).

3. The gas refractive index measuring device based on metasurface according to claim 1, characterized in that: The shortest straight-line distance between the cylindrical hole (6) and the first flange (2-1) is less than the shortest straight-line distance between the metasurface (4) and the first flange (2-1).

4. The gas refractive index measuring device based on metasurface according to claim 1, characterized in that: The first metal rectangular waveguide (1-1) and the second metal rectangular waveguide (1-2) operate in the frequency range of 0.1 GHz to 50 GHz.

5. The gas refractive index measuring device based on metasurface according to claim 1, characterized in that: The metasurface (4) is made of copper, aluminum, or a material with electrical conductivity of It is made of any one of the materials in the doped silicon wafer.

6. The gas refractive index measuring device based on metasurface according to claim 1, characterized in that: When the transverse magnetic wave excited by the vector network analyzer (5) is at a preset grazing angle When a waveguide merging body formed by the first metallic rectangular waveguide (1-1) and the second metallic rectangular waveguide (1-2) is incident on the metasurface (4), if the operating frequency of the waveguide merging body and the conductivity of the metasurface (4) satisfy the following formula, then the reflectivity of the metasurface (4) reaches a minimum: ； in, The conductivity of the metasurface (4) is given by Angular frequency and , It is the operating frequency of the waveguide assembly. is the vacuum permittivity.

7. The gas refractive index measuring device based on metasurface according to claim 6, characterized in that: The preset glancing angle The scope is: .

8. The gas refractive index measuring device based on metasurface according to claim 1, characterized in that: In the waveguide combination formed by the first metallic rectangular waveguide (1-1) and the second metallic rectangular waveguide (1-2), when the higher-order mode transverse magnetic wave operates near the cutoff frequency, the higher-order mode transverse magnetic wave is approximately equivalent to four plane waves with a preset grazing angle. When incident on the metasurface (4), the conductivity of the metasurface (4) is... The frequency corresponding to the minimum reflectivity of the metasurface (4) actually observed in the waveguide merging. The following relationship must be satisfied: ； in, The vacuum permittivity, It is the operating frequency of the waveguide assembly, and also the frequency corresponding to the minimum reflectivity of the metasurface (4); This is the cutoff frequency for higher-order transverse magnetic wave modes within the waveguide merging body.

9. The gas refractive index measuring device based on a metasurface according to claim 8, characterized in that: The cutoff frequency The structural dimensions of the first rectangular opening (3-1) of the first flange (2-1) and the mode order of the transverse magnetic wave propagating within the waveguide assembly are related, and are expressed as follows: ； in, It is the speed of light in a vacuum. It is the refractive index of the gas inside the waveguide. and These are the wide and narrow side dimensions of the first rectangular opening (3-1) of the first metallic rectangular waveguide (1-1), respectively. and They are transverse magnetic waves The order of the pattern.

10. The gas refractive index measuring device based on a metasurface according to claim 9, characterized in that: When the refractive index of the gas within the waveguide merged body changes, it will cause the frequency corresponding to the minimum reflectivity of the metasurface (4) to be affected. The offset satisfies the following relationship: ； in, This represents the change in the refractive index of the gas. This represents the change in the frequency of the minimum reflectivity within the waveguide merging body caused by the change in the refractive index of the corresponding gas.

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