Achieving polarization-selective absorption and liquid-immersion tunable bimetallic hybrid metasurface

Abstract

This invention discloses a bimetallic hybrid metasurface that achieves polarization-selective absorption and tunable liquid immersion. The metasurface consists of a three-layer structure: a bimetallic hybrid layer, a silicon dioxide layer, and a silver reflective layer. The bimetallic hybrid layer is composed of aluminum and titanium nanoribbons. The bimetallic hybrid metasurface achieves perfect absorption of incident light under x-polarized light at the resonant wavelength and specular reflection of incident light under y-polarized light, thus exhibiting a high extinction ratio. Furthermore, the absorption peak wavelength of the metasurface can be continuously and dynamically tuned by adjusting the unit period of the metasurface or by utilizing active tuning through liquid immersion. The bimetallic hybrid metasurface proposed in this invention achieves high-contrast polarization-selective absorption and possesses advantages such as simple structure, ease of integration, and dynamic tunability, thus it can be widely applied in practical applications such as novel optical polarizers and photodetectors.

Description

Technical Field

[0001] This invention relates to the field of metasurface optics, specifically to a bimetallic hybrid metasurface that achieves polarization-selective absorption and tunable liquid immersion. Background Technology

[0002] Metasurface technology enables unprecedented degrees of freedom in manipulating light at the subwavelength scale, manifesting in various functions such as structural color, perfect absorption, beam steering, metaholography, and emission control. In these functional research areas, metasurface-based perfect absorbers form the foundation of light control technology, profoundly impacting applications in photovoltaics, photoelectric detection, optical filtering, and biomedical sensing. With the continuous deepening of micro-nano photonics research and technological advancements, nanostructure-based metasurfaces have shown enormous potential in light manipulation, particularly in multifunctional absorption. Metal-insulator-metal structures, as commonly used structures for metasurface spectral manipulation, have been extensively studied through various physical principles (such as plasmon resonance, Fabry-Perot resonance, and bound states in continuums) and applied to perfect absorption at different frequency bands. For example, a three-layer film with a metal-insulator-metal structure can absorb light at a specific frequency, and its resonant wavelength can be precisely tuned by adjusting the thickness of the insulating layer.

[0003] Although numerous studies have focused on dynamic perfect absorption on metasurfaces, achieving high-contrast polarization-dependent absorption and maintaining optical performance stability during active tuning remains a critical technical challenge that urgently needs to be addressed. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a bimetallic hybrid metasurface that achieves polarization-selective absorption and tunable liquid immersion, thereby overcoming the deficiencies in maintaining stable optical performance during high-contrast polarization-correlated absorption and tuning processes, and achieving efficient, stable, and flexibly tunable perfect infrared polarization-selective absorption.

[0005] To achieve the above objectives, the technical solution provided by the present invention is as follows:

[0006] In a first aspect, this invention provides a bimetallic hybrid metasurface, which is based on a bimetallic hybrid layer-insulating layer-metal layer architecture. The bimetallic hybrid layer is located at the top and is composed of a first metal nanoribbon and a second metal nanoribbon. Both the first and second metal nanoribbons extend infinitely along the y-axis and are periodically arranged at intervals along the x-axis. The metal layer is located at the bottom, and the insulating layer is located between the top and bottom metal layers.

[0007] In the preferred embodiment, the bimetallic hybrid metasurface that achieves polarization-selective absorption and immersion-tunable properties has a top metal layer composed of titanium nanoribbons and aluminum nanoribbons that are infinitely long along the y-axis. The synergistic effect of these two metal nanoribbons is the key to achieving the polarization-selective function.

[0008] The bottom of the bimetallic hybrid metasurface is a thick silver layer with a thickness of 100-120 nm (preferably 100 nm). In specific implementation, an appropriate thickness can be selected to ensure light reflection. This silver layer can reflect electromagnetic waves that have passed through the intermediate layer back into the structure, increasing the propagation path of electromagnetic waves in the structure and thus improving absorption efficiency.

[0009] The insulating layer in the middle of the bimetallic hybrid metasurface is any one of silicon dioxide, aluminum oxide, or plexiglass (preferably silicon dioxide), and its thickness is on the subwavelength scale. By changing the thickness of the insulating layer, the resonant frequency of the absorption device can be adjusted to the desired frequency band.

[0010] Secondly, the present invention provides a liquid-tunable infrared polarization-selective absorption device comprising the aforementioned bimetallic hybrid metasurface. The absorption peak wavelength in the x-polarized infrared band can be adjusted by changing the metasurface cell period or by immersing the metasurface in liquids with different refractive indices.

[0011] Furthermore, the application of the bimetallic hybrid metasurface that achieves polarization-selective absorption and tunable liquid immersion is as follows: the bimetallic hybrid metasurface can perfectly absorb and reflect x-polarized infrared light and y-polarized infrared light respectively at its resonant wavelength, realizing the integration of the functions of two optical devices at the subwavelength scale. In a specific preferred embodiment, the device can achieve an absorption rate of 99.9% for x-polarized light and reflect y-polarized light at the resonant wavelength, thus functioning as a high-performance linear polarizer.

[0012] The reason is that by adjusting the periodicity of the metasurface unit cells, the absorption peak wavelength of x-polarized light can be continuously tuned in the near-infrared range. At the resonant wavelength, the average absorption rate of x-polarized light exceeds 99%, and while maintaining a high absorption rate of x-polarized light, the reflectivity of y-polarized light remains above 75%. By immersing the metasurface in liquids with different refractive indices, the absorption peak wavelength of the metasurface can be actively tuned: when deionized water, glycerol, and liquid crystal are used as the immersion liquids, the absorption peak wavelength can be continuously and actively switched in the near-infrared range. At the resonant wavelength, the average absorption rate of x-polarized light exceeds 99.5%, and the reflectivity of y-polarized light remains above 76%.

[0013] Thirdly, the present invention provides a design method for a bimetallic hybrid metasurface that achieves polarization-selective absorption and liquid immersion tunability, characterized by comprising the following steps:

[0014] S1: The structure of the bimetallic hybrid metasurface is determined to be a bimetallic hybrid layer, a silicon dioxide layer, and a silver reflective layer arranged sequentially from top to bottom.

[0015] S2: Simulate and calculate the reflection and absorption spectra of bimetallic hybrid metasurfaces under different polarized light illumination;

[0016] S3: By changing the unit cell period, structural parameters, etc., we study the variation law of optical performance of metasurface and optimize the performance of the device under x and y polarized light;

[0017] S4: Immerse the metasurface in liquids with different refractive indices and simulate its optical performance under different immersion conditions to verify the tunability of the absorption peak wavelength and polarization selectivity.

[0018] The advantages and beneficial effects of this invention are as follows:

[0019] 1. The device of the present invention can exhibit distinctly different optical responses to x-polarized and y-polarized light at its resonant wavelength, achieving high-contrast perfect absorption and reflection of infrared polarization selection. This effectively solves the problem of difficulty in achieving high-contrast polarization-related absorption in the prior art and can be widely used in optical systems that require precise polarization control.

[0020] 2. By changing the unit period or immersion strategy, this invention can continuously tune the absorption peak wavelength of x-polarized light in the near-infrared band, providing flexible wavelength customization capabilities for optical applications in the near-infrared band and meeting the specific operating wavelength requirements of different application scenarios.

[0021] 3. The bimetallic hybrid architecture of the present invention achieves excellent optical performance while avoiding the problem of difficult photolithography stripping caused by excessive metal layer thickness. By rationally designing structural parameters, such as oxide layer thickness, metal thickness and duty cycle, the optical performance of the metasurface is further optimized, enabling it to maintain a stable and efficient absorption rate under different working conditions. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the liquid-tunable infrared polarization-selective perfect absorption device based on a bimetallic hybrid metasurface in this invention. The width of the aluminum nanoribbon is w1, the width of the titanium nanoribbon is w2, and P is the unit period of the bimetallic hybrid metasurface.

[0023] Figure 2 This is a simulation diagram of the reflectivity of the metasurface under different polarization conditions, when it is composed of a single metal or a bimetal.

[0024] Figure 3This is a simulation diagram of the absorption performance of the bimetallic hybrid metasurface under different polarization conditions in the case of normal incidence, according to an embodiment of the present invention.

[0025] Figure 4 These are simulation diagrams of the absorption performance of the bimetallic hybrid metasurface under x-polarized and y-polarized light irradiation at different periods in this embodiment of the invention.

[0026] Figure 5 This is a simulation diagram of the absorption performance of the bimetallic hybrid metasurface under liquid immersion conditions with different refractive indices in an embodiment of the present invention. Detailed Implementation

[0027] To more clearly illustrate the structure of the present invention and its functions, the present invention will be further described below with reference to specific embodiments and accompanying drawings.

[0028] Example 1

[0029] This embodiment describes the specific design process and performance characterization of a bimetallic hybrid metasurface that achieves polarization-selective absorption and immersion-tunable properties. The preparation process for the bottom and intermediate thin films involves placing a clean substrate in a vacuum deposition system and depositing a 100nm silver layer and a 40nm silicon dioxide layer from bottom to top, respectively. The preparation process for the top bimetallic hybrid layer involves performing a process of spin coating, electron beam exposure, development, aluminothermic evaporation, and stripping on the aforementioned thin film structure, followed by another spin coating, electron beam exposure, development, titanium thermoelectric evaporation, and stripping.

[0030] As an example, to more clearly illustrate the structural design and performance of the invention, specific dielectric and metallic materials will be selected, and the structural parameters will be designed and optimized using electromagnetic field simulation software, and the performance of the device will be characterized.

[0031] Figure 1 This is a schematic diagram of the structure of a bimetallic hybrid metasurface that achieves polarization-selective absorption and tunable immersion. At its resonant wavelength, this metasurface structure absorbs 99.9% of x-polarized incident light and reflects y-polarized incident light. The absorption and reflection behavior of the metasurface under different polarized light illumination is clearly shown. The upper bimetallic hybrid layer has a set thickness of 35 nm, the intermediate silicon dioxide dielectric layer has a set thickness of 40 nm, and the bottom silver reflective layer has a set thickness of 100 nm.

[0032] To illustrate and demonstrate the structural advantages of this bimetallic hybrid metasurface, we simulated and calculated the optical properties of monometallic and bimetallic hybrid metasurfaces, such as... Figure 2 As shown, compared to monometallic metasurfaces, bimetallic hybrid metasurfaces exhibit an absorption rate of 99.9% at the resonant wavelength. The unit cell period of both monometallic and bimetallic hybrid metasurfaces is 600 nm.

[0033] When the unit cell period of the bimetallic hybrid metasurface is set to 400 nm, the simulated spectrum is as follows: Figure 3 As shown, the designed bimetallic hybrid metasurface structure clearly reflects the difference in absorption performance under x-polarized and y-polarized light, exhibiting a peak around 1400 nm. Under x-polarized light irradiation, due to the strong resonance between the titanium and aluminum nanoribbons, the light field is highly localized at the nanoribbon gaps, resulting in strong energy absorption with an absorption rate of up to 99.9%, thus achieving perfect absorption. Under y-polarized light irradiation, most of the light is directly reflected by the bottom silver layer, resulting in high reflectivity. This allows the metasurface to reflect y-polarized light like a mirror, meaning the design also fulfills the function of a high-performance linear polarizer.

[0034] By keeping the thickness of the top aluminum / titanium layer, the middle silicon dioxide layer, and the bottom silver layer constant, and changing the period P, the optical resonance characteristics of the metasurface can be effectively altered. For example... Figure 4 As shown, when the period P changes from 140 nm to 800 nm, the absorption peak wavelength of x-polarized light undergoes a significant redshift, continuously changing from 1200 nm to 1850 nm, and the average absorption rate remains greater than 99% throughout this process. Simultaneously, the reflectivity of y-polarized light at the corresponding resonant wavelength remains above 75%. This ensures that while achieving wavelength tuning of the x-polarized light absorption peak, the reflection characteristics of y-polarized light are not affected, maintaining the polarization selectivity of the overall structure.

[0035] Figure 5 To achieve continuous active tuning of the absorption peak wavelength of a bimetallic hybrid metasurface using a liquid immersion tuning strategy, the metasurface was immersed in liquids with different refractive indices for testing. The principle is that changes in the liquid's refractive index alter the light propagation characteristics at the metasurface-liquid interface, thus affecting the metasurface's optical resonance. For example, using common substances such as deionized water (n1 = 1.33), glycerol (n2 = 1.475), and liquid crystal (n3 = 1.9) as immersion liquids, the absorption peak wavelength of the bimetallic hybrid metasurface could continuously and actively switch between 1385 nm and 2150 nm, with an average absorptivity exceeding 99.5%. Throughout the liquid tuning process, the reflection of y-polarized light remained above 76%, ensuring the metasurface maintained the performance stability of a linear polarizer under different liquid immersion conditions.

[0036] The present invention presents a liquid-tunable infrared polarization-selective absorption device based on a bimetallic hybrid metasurface. The proposed bimetallic hybrid metasurface structure can be replaced with other figures by those skilled in the art without any creative effort.

Claims

1. A bimetallic hybrid superstructure based on the structure of claim 1, characterized in that: a metal layer is located at the bottom; an insulating layer is formed on the metal layer; and a bimetallic hybrid layer is formed on the insulating layer, the bimetallic hybrid layer is composed of a first metal nanobelt and a second metal nanobelt, both the first metal nanobelt and the second metal nanobelt extend infinitely along the y-axis, and the first metal nanobelt and the second metal nanobelt are arranged periodically along the x-axis with a certain interval. 2.The bimetallic hybrid superstructure based on the structure of claim 1, characterized in that: the first metal nanobelt is a titanium nanobelt; and the second metal nanobelt is an aluminum nanobelt. 3.The bimetallic hybrid superstructure based on the structure of claim 2, characterized in that: the metal layer is a silver layer with a thickness of 100-120 nm. 4.The bimetallic hybrid superstructure based on the structure of claim 3, characterized in that: the material of the insulating layer is any one of silicon dioxide, aluminum oxide or organic glass. A device comprising the bimetallic hybrid superstructure based on the structure of claim 4. The device has an absorption rate of more than 99% for x-polarized light at the resonance wavelength, and reflects y-polarized light, thereby serving as a high-performance linear polarizer. By adjusting the period of the superstructure unit, the absorption peak wavelength of x-polarized light can be continuously tuned in the near-infrared range, and the absorption rate of x-polarized light at the resonance wavelength is more than 99%, and the reflectivity of y-polarized light is always maintained at more than 75% while maintaining the high absorption rate of x-polarized light. By immersing the superstructure in different refractive index immersion liquids, the absorption peak wavelength of the superstructure can be actively tuned. 9.The tunable infrared polarization selective absorption device of claim 8, characterized in that: When the immersion liquid is deionized water, glycerol and liquid crystal respectively, the absorption peak wavelength can be continuously and actively switched in the near-infrared range, and the absorption rate of x-polarized light at the resonance wavelength is more than 99%, and the reflectivity of y-polarized light is maintained at more than 76%. A device using the bimetallic hybrid superstructure based on the structure of claim 4, comprising the following steps:

5. A liquid tunable infrared polarization selective absorption device, characterized by: S1: determining that the structure of the bimetallic hybrid superstructure is a bimetallic hybrid layer-insulating layer-metal layer arranged in order from top to bottom; 6. The tunable infrared polarization selective absorption device of claim 5, wherein: S2: simulating the reflection and absorption spectrum of the bimetallic hybrid superstructure under different polarized light irradiation; 7. The tunable infrared polarization selective absorption device of claim 6, wherein: S3: changing the unit period and structure parameters to study the change rule of the optical performance of the superstructure, and optimizing the performance of the device under x and y polarized light; 8. The tunable infrared polarization selective absorption device of claim 7, wherein: S4: immersing the superstructure in different refractive index liquids to simulate and calculate the optical performance of the superstructure under different immersion conditions, and verify the tunability of the absorption peak wavelength and the polarization selective property. ​ ​ 10. A method of liquid tunable infrared polarization selective absorption based on bimetallic hybrid superstructured surfaces, characterized in that: ​ ​ ​ ​ ​

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