A highly sensitive suspended terahertz metamaterial sensor and its application

Abstract

The invention discloses a high-sensitivity suspended terahertz metamaterial sensor and an application thereof, comprising N×M periodically arranged unit structures, wherein the unit structure comprises a substrate, a dielectric support layer and a metal layer arranged on the dielectric support layer; the dielectric support layer and the metal layer are both in a "V" shape, and there are two "V" shapes, which are symmetrically arranged mouth to mouth; the line width of the "V" shape is 4-8μm, the line length of both sides is 30-45μm, the angle is 35°-45°, and the bottom width is 8-10μm; the interval between the "V" shapes is 4-8μm; the dielectric support layer is a photoresist with a refractive index of 1.50-1.60, and the ratio of the thickness of the dielectric support layer to the thickness of the metal layer is 70-80:1; the sensor of the invention has a simple structure, low cost, small size, easy processing, high sensitivity, and is applied to the field of biomedical detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of terahertz sensors, and in particular relates to a high-sensitivity suspended terahertz metamaterial sensor and applications thereof. Background Art

[0002] Terahertz waves are electromagnetic waves between microwaves / millimeter waves and infrared radiation, and their frequency range is generally considered to be 0.1-10THz, corresponding to a wavelength of 3mm-30μm. Currently, terahertz technology has become a hot topic of research, mainly because terahertz waves have the unique properties of low photon energy, strong penetration, short pulse time, and fingerprint spectra of many substances. However, most natural materials have no electromagnetic response in the terahertz band, and terahertz devices have disadvantages such as large size, high weight, and imperfect functions. Therefore, the introduction of metamaterial structures combined with terahertz technology has become a new development direction for terahertz devices.

[0003] Metamaterial is an electromagnetic structure with sub-wavelength microstructure units, whose size scale is smaller than the wavelength of external stimulation and has properties that do not exist in nature. Since metamaterials are very sensitive to tiny changes in the dielectric environment around them, when the surrounding dielectric environment changes, the terahertz band resonance peak of the metamaterial structure will shift in frequency. This phenomenon has promoted the development of terahertz metamaterial sensors.

[0004] A Chinese patent with publication number CN112014350B discloses a reflective terahertz adjustable refractive index sensor, which changes the chemical potential of graphene by applying electricity to adjust the dielectric constant and conductivity of graphene, thereby achieving the function of switching multiple resonance points of the refractive index sensor. Its preparation process is relatively complex.

[0005] A Chinese patent application with publication number CN118258788A discloses a tunable graphene metamaterial triple-frequency terahertz refractive index sensor with a maximum sensing sensitivity of up to 1.38THz / RIU. Although the sensor has high sensitivity, the repeatability and consistency of the graphene-based sensor are difficult to guarantee, which directly affects the performance and reliability of the sensor.

[0006] The Chinese utility model patent with publication number CN215894384U discloses a high-sensitivity sensor based on terahertz metamaterials, which includes a quartz substrate layer, a SU-8 photoresist layer, and a metal metamaterial layer from the bottom to the top; the SU-8 photoresist layer and the metal metamaterial layer are periodically arranged on the quartz substrate layer, and the hollow pattern of the metal metamaterial layer is a ring with a cross notch. When in different refractive index environments, the transmission resonance peak will drift to achieve refractive index sensing. The refractive index sensitivity of the sensor reaches 0.668THz / RIU. Although the sensitivity has been improved, its detection sensitivity needs to be further improved in the field of biological detection.

[0007] Usually, the fixed refractive index of the metamaterial sensor substrate will affect the overall refractive index sensitivity of the sensor. The influence of the underlying substrate on the sensing ability of terahertz metamaterial sensors has become an important issue that needs to be solved in terahertz sensor research in recent years. Therefore, it is of great significance to design a terahertz metamaterial sensor that is easy to process, small in size, low in cost, and highly sensitive. Summary of the invention

[0008] The technical problem to be solved by the present invention is to provide a highly sensitive suspended terahertz metamaterial sensor and its application, which has a simple structure, low cost, small size, and is easy to process, and can improve the sensitivity of the terahertz metamaterial sensor.

[0009] The present invention includes: a highly sensitive suspended terahertz metamaterial sensor, comprising N×M periodically arranged unit structures, wherein N and M are natural numbers greater than 0, and the unit structure comprises a substrate, a dielectric support layer, and a metal layer arranged on the dielectric support layer; the dielectric support layer and the metal layer are both in a "V" shape, and there are two "V" shapes, which are symmetrically arranged mouth to mouth; the line width of the "V" shape is 4-8μm, preferably 6μm, and the length of the two sides of the "V" shape is 30-45μm, Preferably, the length of both sides is 40 μm, the angle of the "V" figure is 30°-50°, and the preferred angle is 40°; the bottom width of the "V" figure is 8-10 μm, and the preferred bottom width is 9 μm; the interval between the "V" figures is 4-8 μm, and the preferred interval is 6 μm; the dielectric support layer is a photoresist with a refractive index of 1.50-1.60, and the preferred refractive index is 1.56; the thickness ratio of the dielectric support layer to the metal layer is 70-80:1, and the preferred thickness ratio is 75:1.

[0010] Furthermore, the material of the substrate is gallium arsenide.

[0011] Furthermore, the thickness of the substrate is 15 μm, and the substrate is rectangular with side lengths of 55 μm and 120 μm respectively.

[0012] Furthermore, the material of the metal layer is gold.

[0013] Furthermore, the N×M≥100.

[0014] Another object of the present invention is to provide an application of the above-mentioned sensor, wherein the high-sensitivity suspended terahertz metamaterial sensor is applied in the field of biomedical detection.

[0015] Beneficial effects of the present invention:

[0016] (1) The suspended terahertz metamaterial sensor of the present invention obtains a highly sensitive sensor by exploring the arrangement of the "V"-shaped patterns, the line width, the length of the two sides, the angle, the bottom width, the interval between the patterns, and the material and thickness ratio of each layer, and the sensitivity reaches 828GHz / RIU, which is much higher than other sensors of the same type;

[0017] (2) The metal layer of the unit structure of the present invention is a symmetrical "V"-shaped structure. Under the excitation of electromagnetic waves, a surface current flowing in the opposite direction is generated on the surface of the symmetrical "V"-shaped metal arm and oscillates along the metal arm, which is a typical dipole resonance, and a resonance peak is generated at a frequency of about 1.964 THz;

[0018] (3) The substrate material of the suspended terahertz metamaterial sensor of the present invention is gallium arsenide, whose fixed refractive index has little effect on the overall refractive index of the sensor, thereby further improving the sensitivity of the sensor;

[0019] (4) The suspended terahertz metamaterial sensor of the present invention adopts the existing mature photolithography process, which has high precision and efficiency. It does not require complex semiconductor processes or expensive deep ultraviolet photolithography equipment, which will greatly reduce the difficulty of production and the requirements for instruments and equipment, and can realize the mass production of the sensors of this project. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 A three-dimensional diagram of a unit structure provided in Example 1 of the present invention;

[0021] Figure 2 A top view of a unit structure provided in Example 1 of the present invention;

[0022] Figure 3 A side view of a unit structure provided in Example 1 of the present invention;

[0023] Figure 4 The surface current of the sensor provided in Example 1 of the present invention at 1.964 THz;

[0024] Figure 5 This is a schematic diagram of the influence of different analyte thickness sensors in Example 2 of the present invention;

[0025] Figure 6 A diagram of the resonant frequency shift of different thickness sensors provided in Example 2 of the present invention;

[0026] Figure 7 This is a schematic diagram of the influence of different refractive index sensors in Example 2 of the present invention;

[0027] Figure 8 A graph of resonance frequency shifts of different refractive index sensors provided in Example 2 of the present invention;

[0028] Fig. 9 The effect of the thickness of the dielectric support layer provided in Example 2 of the present invention on the refractive index sensitivity of the sensor;

[0029] Fig.10 Cell sensing transmission spectra with different refractive indices provided in Example 3 of the present invention;

[0030] Fig.11 Characteristic diagrams of sensors with different “V” arrangements provided for Comparative Example 1 of the present invention. DETAILED DESCRIPTION

[0031] Example 1

[0032] Prepare a suspended terahertz metamaterial sensor, which is composed of a plurality of basic units arranged periodically, wherein the x-direction and the y-direction are both periodically arranged, and the number is not less than 20×10, that is, the number is not less than 200, and the x-direction and the y-direction are two directions of the base layer 1 respectively. Figure 1 The three-dimensional diagram of the unit structure and Figure 2 As shown in the top view of the unit structure, the unit structure includes three layers, which are a substrate, a dielectric support layer, and a metal layer from bottom to top. The patterns of the dielectric support layer and the metal layer are composed of a group of symmetrical "V" shapes.

[0033] As can be seen from the figure, the substrate is rectangular, the material of the substrate is gallium arsenide, the dielectric constant is 12.9, wherein the substrate dimensions Px and Py are 55 μm and 120 μm respectively, and the thickness T1 is 15 μm.

[0034] The material of the dielectric support layer is photoresist, the refractive index is 1.56, and the thickness T2 is 15 μm.

[0035] The material of the metal layer is gold, the electrical conductivity thereof is 4.561×10 7 S / m, and the thickness T3 is 0.2 μm.

[0036] The dielectric support layer and the metal layer are provided with two symmetrical "V" shapes with a line width W of 6 μm, a line length L of 40 μm, an angle θ of 40°, a bottom width D of 9 μm, and a symmetrical "V" interval G of 6 μm.

[0037] The metal layer of the unit of the present invention is a symmetrical "V" shaped structure. Figure 3 It can be seen that under the excitation of electromagnetic waves, surface currents flowing in opposite directions are generated on the surface of the symmetrical "V"-shaped metal arms and oscillate along the metal arms. This is a typical dipole resonance, thus generating a resonance peak at a frequency of around 1.942 THz.

[0038] Example 2

[0039] In order to determine the sensitivity of the sensor and the effect of the analyte thickness on the sensor, the thickness and refractive index of the analyte were fixed. First, the refractive index of the analyte was fixed to 2.0, and the thickness range of the analyte was set to 10-40 μm. Figure 4 , Figure 5 It can be seen that the frequency shift is fastest when the thickness is between 15μm and 20μm. This is because the object to be measured is getting closer and closer to the thickness of the dielectric support layer, and the sensor coupling is gradually enhanced. At this time, the growth rate of the sensor's sensitivity to the thickness of the object to be measured increases. When the thickness of the analyte reaches more than 30μm, the increase in frequency shift gradually saturates.

[0040] Then, the thickness of the analyte was set to 30 μm, and the refractive index range was set to 1.0-2.0. Due to the increase in the refractive index, the resonance frequency continued to move toward low frequencies. The specific results are shown in Figure 6 Schematic diagram of the effect of different refractive indices on the sensor. Linear fitting of the frequency offset of each refractive index is: y = 828.42x + 64.67. The slope of the linear equation is the sensitivity of the sensor. Therefore, the sensitivity of the sensor is 828GHz / RIU. The results are shown in Figure 7 .

[0041] Depend on Figure 8 It can be seen that as the thickness of the dielectric support layer increases, the sensitivity of the sensor also increases. When it increases to T2 = 15μm, the sensitivity can reach up to 828GHz / RIU. This is because the near field of the suspended terahertz metamaterial sensor is constantly weakened in the substrate, and the influence of the substrate on the effective refractive index of the surrounding medium is gradually weakened. At this time, the effective refractive index is mainly affected by the refractive index of the analyte.

[0042] Example 3

[0043] In order to verify the detection ability of the designed sensor for normal cells and cancer cells, this embodiment specifically performs sensing calculations on five different cells with refractive indices of 1.35, 1.39, 1.392, 1.395, and 1.399: normal cells, Hela, PCL2, MDA-MB-231, and MCF-7. The latter four are different cancer cells. The results are shown in Fig. 9, it can be seen that as the refractive index of the sample increases, the resonance frequency gradually moves to a low frequency. Cancer cells have a larger refractive index, so the offset is greater than that of normal cells, indicating that this sensor can distinguish between normal cells and cancer cells. In practical applications, different cells can be detected by using the drop casting method on the sensor surface.

[0044] The suspended terahertz metamaterial sensor of the present invention has ultra-high refractive index sensitivity, mainly by detecting slight changes in the dielectric constant of the material through the shift of the resonant frequency, and determining the required information through the dielectric constants of different substances, such as the distinction between normal cells and cancer cells, different concentrations of the same substance, etc.

[0045] The present invention can also use the sensor to measure the concentration of tumor markers. The principle is that tumor markers with different concentrations have different dielectric constants, and the resonance peaks of the sensor appear at different frequencies.

[0046] Comparative Example 1

[0047] In order to compare sensors with different “V” shaped distributions, two other different “V” shapes were set up; one was a “V” with a symmetrical arrangement at the bottom, and the other was a “V” arrangement in the same direction, and the rest was the same as in Example 1.

[0048] The sensors arranged symmetrically at the bottom of the "V" are simulated and fitted linearly to obtain the linear equation: y = 776.28x + 57.43. Fig.11 a.

[0049] The linear equation of the sensors arranged in the same direction as the "V" shape is y=796.42x+48.73. Fig.11 b.

[0050] Therefore, the refractive index sensitivities of the two sensors are 776 GHz / RIU and 796 GHz / RIU, respectively, both lower than the sensor of the present invention.

[0051] Depend on Fig.11 c It can be seen that when the sensor is not provided with a dielectric support layer, the transmission coefficient of the sensor resonance peak is very shallow, and the sensitivity obtained through simulation calculation is only 85GHz / RIU. Moreover, in actual applications, the resonance peak disappears after attenuation, and the sensing function cannot be realized. This is because the near field of the suspended terahertz metamaterial sensor is constantly weakened in the substrate, and the influence of the substrate on the effective refractive index of the surrounding medium is gradually weakened. At this time, the effective refractive index is mainly affected by the refractive index of the analyte.

[0052] Comparative Example 2

[0053] The dielectric support layer and the metal layer are provided with two symmetrical "V" shapes with a line width W of 6 μm, a line length L of 40 μm, an angle θ of 60°, a bottom width D of 9 μm, and a symmetrical "V" interval G of 6 μm; the rest is the same as in Example 1. The obtained sensor has a sensitivity of 780 GHz / RIU.

[0054] Comparative Example 3

[0055] The dielectric support layer and the metal layer are provided with two symmetrical "V" shapes with a line width W of 6 μm, a line length L of 40 μm, an angle θ of 40°, a bottom width D of 9 μm, and a symmetrical "V" interval G of 2 μm; the rest is the same as in Example 1. The obtained sensor has a sensitivity of 819 GHz / RIU.

[0056] Comparative Example 4

[0057] The material of the dielectric support layer is photoresist, with a refractive index of 1.65 and a thickness of 16 μm, and the rest is the same as in Example 1. The obtained sensor has a sensitivity of 793 GHz / RIU.

[0058] Comparative Example 5

[0059] The material of the substrate is silicon material, and the rest is the same as in Example 1. The obtained sensor has a sensitivity of 807 GHz / RIU.

[0060] Comparative Example 6

[0061] The dielectric support layer and the metal layer are provided with two symmetrical "V" shapes with a line width W of 10 μm, a line length L of 25 μm, an angle θ of 40°, a bottom width D of 9 μm, and a symmetrical "V" interval G of 6 μm, and the rest is the same as in Example 1. The obtained sensor has no obvious resonance peak and no sensing function.

[0062] A person skilled in the art should understand that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of protection of the present application is limited to these examples. In line with the concept of the present application, the technical features in the above embodiments or different embodiments may be combined, the steps may be implemented in any order, and there are many other variations of different aspects of one or more embodiments of the present application as described above, which are not provided in detail for the sake of simplicity.

[0063] One or more embodiments of the present application are intended to cover all such substitutions, modifications and variations that fall within the broad scope of the present application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of one or more embodiments of the present application should be included in the protection scope of the present application.

Claims

1. A highly sensitive suspended terahertz metamaterial sensor, characterized in that: The invention comprises N×M periodically arranged unit structures, wherein N and M are natural numbers greater than 0, and the unit structure comprises a substrate (1), a dielectric support layer (2), and a metal layer (3) arranged on the dielectric support layer; the dielectric support layer (2) and the metal layer (3) are both in the form of a "V"-shaped pattern, and there are two "V"-shaped patterns, which are symmetrically arranged mouth to mouth; the line width of the "V"-shaped pattern is 4-8 μm, the length of the two sides of the "V"-shaped pattern is 30-45 μm, the angle of the "V"-shaped pattern is 30°-50°, and the bottom width of the "V"-shaped pattern is 8-10 μm; the interval between the "V"-shaped patterns is 4-8 μm; the dielectric support layer (2) is a photoresist, and the refractive index is 1.50-1.60, and the ratio of the thickness of the dielectric support layer (2) to the thickness of the metal layer (3) is 70-80:

1.

2. The sensor according to claim 1, characterized in that: The material of the substrate (1) is gallium arsenide.

3. The sensor according to claim 1, characterized in that: The thickness of the substrate (1) is 15 μm, and the substrate (1) is rectangular, with side lengths of 55 μm and 120 μm respectively.

4. The sensor according to claim 1, characterized in that: The refractive index of the dielectric support layer (2) is 1.56, and the thickness ratio of the dielectric support layer (2) to the thickness of the metal layer (3) is 75:

1.

5. The sensor according to claim 1, characterized in that: The material of the metal layer (3) is gold.

6. The sensor according to claim 1, characterized in that: The line width of the "V"-shaped pattern is 6 μm, and the line lengths of both sides of the "V"-shaped pattern are 40 μm.

7. The sensor according to claim 1, characterized in that: The included angle of the "V" shape is 40°.

8. The sensor according to claim 1, characterized in that: The bottom width of the "V"-shaped pattern is 9 μm, and the interval between the "V"-shaped patterns is 6 μm.

9. The sensor according to any one of claims 1 to 8, characterized in that: The N×M≥100.

10. An application of the sensor according to any one of claims 1 to 9, characterized in that: The high-sensitivity suspended terahertz metamaterial sensor is applied in the field of biomedical detection.

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