Sensing structure of hyperbolic metamaterial for enhancing transverse magneto-optical Kerr effect

Abstract

The invention discloses a sensing structure for enhancing a transverse magneto-optical Kerr effect (TMOKE) based on a hyperbolic metamaterial. The sensing structure is characterized by comprising a magnetic material bismuth iron garnet: yttrium iron garnet (BIG: YIG) with a grating structure, a multilayer hyperbolic metamaterial silver / silicon (Ag / Si) and a silicon dioxide (SiO2) substrate, the bottom layer of the structure is a SiO2 base, and the upper layer of the structure is BIG: YIG deposited on Ag / Si. The method has the beneficial effects that when light enters the surface of the structure at a specific angle, a magnetic dipole mode between the light and a magnetic material can be excited, and the mode not only improves the response capability of the material to an external magnetic field, but also increases the coupling strength between the light and the material, so that the TMOKE is remarkably enhanced; besides, the polarization state of the incident light can be effectively adjusted through the well-designed artificial hyperbolic structure, the interaction between the light and the magnetic material is further optimized, and the ideal TMOKE with the amplitude close to 1 is finally achieved.

Description

Technical Field

[0001] The present invention relates to the field of magneto-optical sensing technology, and in particular to a sensing structure based on hyperbolic metamaterials to enhance the transverse magneto-optical Kerr effect. Background Art

[0002] With the advancement of science and technology, the demand for high-performance sensors is growing, especially in the fields of environmental monitoring, biomedicine and material testing. Traditional magneto-optical sensors have the advantages of excellent real-time response, label-free detection and wide range of applications, which make them show great application potential in biomolecular interactions, drug screening and disease diagnosis. However, they still face challenges in reducing costs, simplifying operations and improving detection limits. Summary of the invention

[0003] The technical problem solved by the present invention is to provide a sensing structure with simple structure and low cost, which utilizes hyperbolic metamaterials to enhance the transverse magneto-optical Kerr effect, thereby achieving high-performance sensing.

[0004] The technical solution adopted by the present invention to solve the above technical problems is: a sensing structure based on hyperbolic metamaterial to enhance the transverse magneto-optical Kerr effect, characterized in that it includes a magnetic material BIG:YIG with a grating structure, a hyperbolic metamaterial Ag / Si and a SiO2 substrate; the bottom layer of the structure is a SiO2 substrate, and the upper layer is BIG:YIG deposited on Ag / Si. The sensing structure is in the solution to be tested, and a magnetic field propagating along the Y-axis direction is applied. Under the action of the magnetic field, the optical properties of the material (such as refractive index and absorption) will change. This change can be described by TMOKE, thereby causing the polarization state of the incident light to rotate; when light is incident on the surface of the structure, when the energy splitting between the light of a specific frequency and the magnetic dipole matches, a magnetic dipole resonance is generated, and the reflectivity of the light will change significantly. When the sensing structure contacts the liquid to be tested, its refractive index change affects the resonance condition, thereby causing a change in the intensity of the reflected light. By detecting the change in the polarization state of the reflected light, real-time information about the environment can be obtained, and high-sensitivity biosensing can be achieved.

[0005] The method for preparing a sensing structure based on a hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect described in the present invention is characterized by comprising the following specific steps:

[0006] S0: The structure adopts a bottom-up design approach. First, chemical vapor deposition technology is used to vaporize the silicon source and introduce it into the reaction chamber. It reacts with oxygen at high temperature to generate a SiO2 film. The deposition time and gas flow rate are controlled to achieve the desired thickness.

[0007] S1: Use deionized water and ultrasonic cleaning to remove impurities on the surface of the SiO2 substrate; in a vacuum environment, ensure that the pressure in the reaction chamber is moderate, heat the silicon target, evaporate silicon and deposit it on the SiO2 substrate, and monitor the deposition rate and time to achieve the designed thickness; similar to the deposition of the silicon layer, use a silver target to evaporate in a vacuum environment; according to the designed hyperbolic structure, repeat the above deposition steps, alternately depositing silicon layers and silver layers until the desired number of layers and total thickness are reached; anneal the deposited multilayer material to improve interlayer bonding and material properties.

[0008] S2: Use spin coating technology to evenly coat the photoresist on the surface of BIG:YIG material to obtain a uniform film. Pre-bake between 90℃-120℃ to remove the solvent in the photoresist. Use the designed mask for exposure to form the desired stripe pattern. Immerse the exposed BIG:YIG in the developer to remove the unexposed photoresist and form an etched pattern; place the developed BIG:YIG in the ion beam etching equipment, set appropriate etching parameters, including ion beam energy, etching gas and etching time, and use ion beam to bombard the BIG:YIG material. Control the energy and incident angle of the ion beam to achieve the desired etching depth and shape, and finally monitor the etching process to ensure etching accuracy and consistency.

[0009] The beneficial effects of the present invention are:

[0010] 1. The present invention proposes a sensing structure based on hyperbolic metamaterials to enhance the transverse magneto-optical Kerr effect. The structure introduces an external magnetic field to excite magnetic dipole resonance, thereby enhancing the TMOKE effect and achieving high-performance detection of magnetic field changes.

[0011] 2. The present invention significantly improves the optical properties of the material, including the refractive index and light field distribution, through the negative refractive index characteristics of the Ag / Si multilayer hyperbolic structure, thereby enhancing the interaction between light and the material, making the amplitude of TMOKE close to the theoretical maximum value of 1.

[0012] 3. The present invention also has the advantages of simple structure, low cost and easy implementation. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 A schematic diagram of the overall structure of a specific embodiment of the present invention.

[0014] Figure 2 Schematic diagram of the hyperbolic metamaterial structure of the present invention.

[0015] Figure 3 TMOKE signal enhancement diagram of the present invention.

[0016] Figure 4 Flowchart of the manufacturing process of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0018] See also Figure 1 , the embodiment of the present invention includes a magnetic material BIG:YIG (1), a hyperbolic metamaterial Ag / Si (2 / 3) and a substrate SiO2 (4);

[0019] The BIG:YIG (1) is a medium with magnetic properties that can interact with light to produce magnetic dipole resonance, which can not only enhance the material's responsiveness to light, but also significantly enhance TMOKE. The main goals of etching BIG:YIG into a grating structure are: first, the grating structure has the ability to modulate the phase and intensity of light, so that it can effectively promote the interaction between light and materials. When light passes through the grating, the changes in its phase and intensity can enhance the local field of light and produce stronger coupling with the material, thereby improving the transmission efficiency of light. Secondly, the periodic characteristics of the grating can effectively guide and limit the propagation direction of light. When the incident light interacts with the material, it can propagate with higher efficiency and more favorable angles, thereby improving the overall incident efficiency. Finally, by adjusting the parameters of the grating (such as period, depth, material composition, etc.), tuning and enhancement of light of different wavelengths can be achieved.

[0020] The Ag / Si (2 / 3) multilayer hyperbolic structure has a negative refractive index characteristic, which can realize the reverse propagation of light waves, so that the light field forms a local enhancement phenomenon inside the material. This phenomenon not only increases the interaction between light and magnetic materials, but also improves the magneto-optical response ability of the material, thereby significantly improving the intensity of the TMOKE effect. In addition, the hyperbolic material supports the propagation of multiple light modes, enabling it to optimize the propagation path and modulation method of light.

[0021] The SiO2(4) substrate material is used as a substrate material due to its excellent surface flatness, which helps the uniform growth of the film and maintains the integrity of the structure. Good surface flatness can reduce defects that may occur during the film growth process, thereby ensuring the excellent performance and stability of the final material.

[0022] See also Figure 2 The present invention precisely customizes the hyperbolic material by adjusting the thickness of the Ag(2) and Si(3) films to achieve the maximum enhancement of TMOKE, including the following steps:

[0023] The finite element software COMSOL Multiphysics was used to establish the geometric model of the hyperbolic structure and perform simulations to study its unique physical properties. The equivalent dielectric tensor of the hyperbolic material has different signs in certain frequency ranges. Specifically, the dielectric constant in one direction is positive (ε ⊥ >0), the dielectric constant in the other direction is negative (ε ‖ <0), in order to reveal the properties of hyperbolic metamaterials, we give the parallel (ε ‖ ) and vertical (ε ⊥ )The dielectric constant component formula in the xy plane is:

[0024]

[0025] Among them, ε Ag and t Ag are the dielectric constant and thickness of Ag(2), ε Si and t Si is the dielectric constant and thickness of Si(3). By adjusting t Ag =30nm and t Si =50nm, achieving the maximum enhancement of TMOKE.

[0026] See also Figure 3 The present invention discusses the enhancement effect of TMOKE under different refractive indices, comprising the following steps:

[0027] The geometric model of the sensing structure based on hyperbolic metamaterial-enhanced TMOKE was established using the finite element software COMSOL Multiphysics. By comparing the simulation results of multiple refractive index values, it can be found that when the refractive index is in the range of 1.33 to 1.38, the amplitude of TMOKE is significantly improved, showing an enhancement effect close to the theoretical maximum value of 1. This shows that within this refractive index range, the optical properties of the hyperbolic metamaterial interact more effectively with the external magnetic field, greatly improving the magneto-optical response performance of the material.

[0028] See also Figure 4 The present invention proposes a sensing structure based on hyperbolic metamaterials to enhance the transverse magneto-optical Kerr effect, including the following manufacturing processes and implementation steps:

[0029] First, the structure is designed from the bottom up, using chemical vapor deposition technology to vaporize the silicon source and introduce it into the reaction chamber, where it reacts with oxygen at high temperature to generate a SiO2(4) film. The deposition time and gas flow rate are controlled to achieve the desired thickness.

[0030] Use deionized water and ultrasonic cleaning to remove impurities on the surface of the SiO2(4) substrate; in a vacuum environment, ensure that the pressure in the reaction chamber is moderate, heat the silicon target, evaporate silicon and deposit it on the SiO2(4) substrate, and monitor the deposition rate and time to achieve the designed thickness; similar to the deposition of the silicon layer, use a silver target to evaporate in a vacuum environment; according to the designed hyperbolic structure, repeat the above deposition steps, alternately depositing Si(3) layers and Ag(2) layers until the desired number of layers and total thickness are reached; anneal the deposited multilayer material to improve interlayer bonding and material properties.

[0031] Use spin coating technology to evenly coat the photoresist on the surface of BIG:YIG(1) material to obtain a uniform film. Pre-bake at 90℃-120℃ to remove the solvent in the photoresist. Use the designed mask for exposure to form the desired stripe pattern. Immerse the exposed BIG:YIG(1) in the developer to remove the unexposed photoresist and form an etched pattern; place the developed BIG:YIG(1) in the ion beam etching equipment, set appropriate etching parameters, including ion beam energy, etching gas and etching time, and use ion beam to bombard the BIG:YIG(1) material. Control the energy and incident angle of the ion beam to achieve the desired etching depth and shape, and finally monitor the etching process to ensure etching accuracy and consistency.

[0032] The sensing structure is placed in the solution to be tested, and a magnetic field propagating along the Y-axis is applied. Under the action of the magnetic field, the optical properties of the material (such as refractive index and absorption) will change. This change can be described by TMOKE, which causes the polarization state of the incident light to rotate; when light is incident on the surface of the structure, when the energy splitting between the light of a specific frequency and the magnetic dipole matches, magnetic dipole resonance is generated, and the reflectivity of the light changes significantly. When the sensing structure contacts the liquid to be tested, its refractive index change affects the resonance condition, resulting in a change in the intensity of the reflected light. By detecting the change in the polarization state of the reflected light, real-time information about the environment can be obtained, and high-sensitivity biosensing can be achieved.

[0033] The above embodiments are only used to illustrate the design ideas and features of the present invention, and their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. The protection scope of the present invention is not limited to the above embodiments. Therefore, any equivalent changes or modifications made based on the principles and design ideas disclosed by the present invention are within the protection scope of the present invention.

Claims

1. A sensing structure based on hyperbolic metamaterials to enhance transverse magneto-optical Kerr effect, characterized in that: The invention comprises a magnetic material BIG:YIG with a grating structure, a hyperbolic metamaterial Ag / Si and a SiO2 substrate; the bottom layer of the structure is the SiO2 substrate, and the upper layer is the BIG:YIG deposited on the Ag / Si. The BIG:YIG is a medium with magnetic properties that can interact with light to produce magnetic dipole resonance, which not only enhances the material's responsiveness to light, but also significantly enhances TMOKE. The main goals of etching BIG:YIG into a grating structure are: first, the grating structure has the ability to modulate the phase and intensity of light, so that it can effectively promote the interaction between light and materials. When light passes through the grating, the changes in its phase and intensity can enhance the local field of light and produce stronger coupling with the material, thereby improving the transmission efficiency of light. Secondly, the periodic characteristics of the grating can effectively guide and limit the propagation direction of light. When the incident light interacts with the material, it can propagate with higher efficiency and more favorable angles, thereby improving the overall incident efficiency. Finally, by adjusting the parameters of the grating (such as period, depth, material composition, etc.), tuning and enhancement of light of different wavelengths can be achieved. The Ag / Si multilayer hyperbolic structure has a negative refractive index characteristic, which can realize the reverse propagation of light waves, so that the light field forms a local enhancement phenomenon inside the material. This phenomenon not only increases the interaction between light and magnetic materials, but also improves the magneto-optical response ability of the material, thereby significantly improving the intensity of the TMOKE effect. In addition, the hyperbolic material supports the propagation of multiple light modes, enabling it to optimize the propagation path and modulation method of light. The SiO2 substrate material is used due to its excellent surface flatness, which helps the uniform growth of the film and maintains the integrity of the structure. Good surface flatness can reduce the defects that may occur during the film growth process, thereby ensuring the excellent performance and stability of the final material.

2. The sensing structure based on hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect according to claim 1, characterized in that: The optical properties of the BIG:YIG are determined using the data experimentally measured by Girón-Sedas et al. (Doi: 10.1103 / physrevb.96.075415). The material surface is etched by an ion beam. After etching, the shape of the grating is parallel stripes with a stripe width w = 180 nm, a depth d1 = 40 nm and a period P = 320 nm, wherein the unetched bottom height d2 = 30 nm.

3. The sensing structure based on hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect according to claim 1, characterized in that: The hyperbolic structure Ag / Si is composed of Ag and Si stacked alternately, and the film is prepared by physical vapor deposition (PVD) technology, where the thickness of the Ag / Si film is (h1, h2) = (30, 50) nm. The optical properties of Ag are based on the experimental data measured by Johnson and Christy et al. (Doi: 10.1103 / PhysRevB.6.4370), while the refractive index of Si is 3.5, and the number of Ag / Si layers n = 1.

4. The sensing structure based on hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect according to claim 1, characterized in that: Using chemical vapor deposition technology, SiO2 is deposited layer by layer at the atomic layer level by alternately exposing the substrate to different gases, with a thickness fixed at 200nm to prevent the transmission of light from affecting the structural performance.

5. The sensing structure based on hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect according to claim 1, characterized in that: The finite element software COMSOL Multiphysics was used to establish the geometric model of the hyperbolic structure and perform simulations to study its unique physical properties. The equivalent dielectric tensor of the hyperbolic material has different signs in certain frequency ranges. Specifically, the dielectric constant in one direction is positive (ε ⊥ >0), the dielectric constant in the other direction is negative (ε ‖ <0), in order to reveal the properties of hyperbolic metamaterials, we give the parallel (ε ‖ ) and vertical (ε ⊥ )The dielectric constant component formula in the xy plane is: Among them, ε Ag and t Ag are the dielectric constant and thickness of Ag, ε Si and t Si is the dielectric constant and thickness of Si. By adjusting the thickness of Ag and Si, the hyperbolic material can be precisely tailored to enhance TMOKE.

6. A sensing structure based on the hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect according to any one of claims 1 to 5, comprising the following specific steps: S0: The structure adopts a bottom-up design approach. First, chemical vapor deposition technology is used to vaporize the silicon source and introduce it into the reaction chamber. It reacts with oxygen at high temperature to generate a SiO2 film. The deposition time and gas flow rate are controlled to achieve the desired thickness. S1: Use deionized water and ultrasonic cleaning to remove impurities on the surface of the SiO2 substrate; in a vacuum environment, ensure that the pressure in the reaction chamber is moderate, heat the silicon target, evaporate silicon and deposit it on the SiO2 substrate, and monitor the deposition rate and time to achieve the designed thickness; similar to the deposition of the silicon layer, use a silver target to evaporate in a vacuum environment; according to the designed hyperbolic structure, repeat the above deposition steps, alternately depositing silicon layers and silver layers until the desired number of layers and total thickness are reached; anneal the deposited multilayer material to improve interlayer bonding and material properties. S2: Use spin coating technology to evenly coat the photoresist on the surface of BIG:YIG material to obtain a uniform film. Pre-bake between 90℃-120℃ to remove the solvent in the photoresist. Use the designed mask for exposure to form the desired stripe pattern. Immerse the exposed BIG:YIG in the developer to remove the unexposed photoresist and form an etched pattern; place the developed BIG:YIG in the ion beam etching equipment, set appropriate etching parameters, including ion beam energy, etching gas and etching time, and use ion beam to bombard the BIG:YIG material. Control the energy and incident angle of the ion beam to achieve the desired etching depth and shape, and finally monitor the etching process to ensure etching accuracy and consistency.

7. The sensing structure based on hyperbolic metamaterial enhanced transverse magneto-optical Kerr effect as claimed in claim 1, characterized in that: The specific process of application in biomolecule specific recognition detection is as follows: the sensing structure is placed in the solution to be tested, and a magnetic field propagating along the Y-axis is applied. Under the action of the magnetic field, the optical properties of the material (such as refractive index and absorption) will change. This change can be described by TMOKE, which causes the polarization state of the incident light to rotate; when light is incident on the surface of the structure, when the energy splitting between the light of a specific frequency and the magnetic dipole matches, magnetic dipole resonance is generated, and the reflectivity of the light changes significantly. When the sensing structure contacts the liquid to be tested, its refractive index change affects the resonance condition, resulting in a change in the intensity of the reflected light. By detecting the change in the polarization state of the reflected light, real-time information about the environment can be obtained, achieving high-sensitivity biosensing.

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