Lithium niobate-liquid crystal integrated metasurface tunable narrow-band filter and preparation method thereof

Abstract

This invention relates to a tunable narrowband filter based on a lithium niobate-liquid crystal integrated metasurface and its fabrication method, overcoming the problems of large device size and limited modulation efficiency in existing technologies. This invention combines a LiNbO3 metasurface with a liquid crystal, synergistically leveraging the electro-optic modulation advantages of both. While achieving efficient control of the filtering wavelength, it significantly reduces the device size, achieving lightweight design. The technical solution adopted in this invention includes a substrate layer, an ITO electrode layer, a LiNbO3 thin layer, a LiNbO3 nanopillar array layer, and a liquid crystal. The ITO electrode layer is disposed on the upper side of the substrate layer, the LiNbO3 thin layer is disposed on the upper side of the ITO electrode layer, the LiNbO3 nanopillar array and the liquid crystal are disposed on the upper side of the LiNbO3 thin layer, the ITO electrode is disposed on the upper side of the nanopillar layer, and the liquid crystal and the LiNbO3 nanopillar array are located between the upper and lower ITO electrode layers.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic device technology, specifically relating to a tunable narrowband filter based on lithium niobate-liquid crystal integrated metasurface and its fabrication method. Background Technology

[0002] Optical filters can transmit or reflect light of certain specific wavelengths, thereby filtering out target signals. They are widely used in various fields such as communications, defense, and medicine. Adjustable narrowband filters, based on ordinary optical filters, adjust the filtering band by applying an external excitation. This allows for the switching and filtering of multi-band signals without replacing the filter, flexibly adapting to wavelength filtering requirements in different scenarios and significantly improving the system's flexibility and versatility.

[0003] The current mainstream methods for controlling the wavelength of filters can be categorized into: thermo-optical tuning, mechanical tuning, and electro-optical tuning, which are analyzed in detail below:

[0004] 1. Thermo-optical tuning: This method adjusts the filtering band by changing the refractive index of the material through Joule heating. However, it suffers from low energy efficiency, slow response speed, and poor temperature stability.

[0005] 2. Mechanical tuning: Band control is achieved by changing the mechanical structure. Due to the inertia of mechanical motion, the tuning speed is slow, and it also suffers from problems such as large size and weight, and is prone to mechanical wear leading to poor stability.

[0006] 3. Electro-optic modulation: By applying an external electric field to change the refractive index of the material, the filtering wavelength can be dynamically controlled. Electro-optic modulation is characterized by its flexibility, high efficiency, and high integration.

[0007] Currently, semiconductor-based filters meet the demands for miniaturization and integration, but suffer from drawbacks such as difficulty in balancing tuning range and quality factor, and poor adaptability to the visible light band. Liquid crystal-based filters, while offering wide tuning range and low driving voltage, are characterized by large component size and integration challenges. Lithium niobate (LiNbO3) possesses advantages such as a large electro-optic coefficient and a large transparency window, making it widely used in electro-optic tuning devices. However, the lithium niobate metasurface exhibits low light-matter interaction, limiting its tuning efficiency.

[0008] In summary, there is an urgent need for an adjustable narrowband filter technology that can stably and efficiently adjust the filtering band while ensuring high integration and wide band applicability. Summary of the Invention

[0009] The purpose of this invention is to provide a tunable narrowband filter based on lithium niobate-liquid crystal integrated metasurface and its fabrication method, which overcomes the problems of large component size and limited control efficiency in the prior art.

[0010] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0011] A tunable narrowband filter based on a lithium niobate-liquid crystal integrated metasurface is characterized by comprising a substrate layer, an ITO electrode layer, a LiNbO3 thin layer, a LiNbO3 nanopillar array layer, and a liquid crystal; the ITO electrode layer is disposed on the upper side of the substrate layer, the LiNbO3 thin layer is disposed on the upper side of the ITO electrode layer, the LiNbO3 nanopillar array and the liquid crystal are disposed on the upper side of the LiNbO3 thin layer, the ITO electrode is disposed on the upper side of the nanopillar layer, and the liquid crystal and the LiNbO3 nanopillar array are located between the upper and lower ITO electrode layers.

[0012] The LiNbO3 array, LiNbO3 thin layer, and substrate layer are vertically distributed from top to bottom; the liquid crystal is liquid and distributed between the LiNbO3 array; the ITO electrodes are distributed on the upper and lower sides of the LiNbO3 thin layer and the LiNbO3 nanopillar array layer-liquid crystal integrated metasurface.

[0013] The LiNbO3 nanopillar array layer consists of multiple periodically arranged LiNbO3 nanopillars, which are cylindrical nanopillars. Each nanopillar is arranged adjacent to another nanopillar in the x and y directions with a period of p, and the spacing between two adjacent nanopillars is p. Each nanopillar is oriented in the same direction. Liquid crystal fills the spaces between adjacent nanopillars. The liquid crystal and the metasurface formed by the periodically arranged LiNbO3 nanopillars work together to filter incident information.

[0014] The liquid crystal is a nematic liquid crystal, which is uniformly filled and distributed between the nanopillars through a perfusion process, with a thickness consistent with the height of the LiNbO3 nanopillars.

[0015] The unit structure dimensions of the cylindrical nanopillars are: height h ~ 300 nm, cylinder radius r ~ 333 nm, and spacing period p ~ 1200 nm.

[0016] The LiNbO3 thin layer is placed below the metasurface. The LiNbO3 cylindrical array is obtained by partially etching the upper part of the LiNbO3 thin layer. Both the LiNbO3 metasurface and the LiNbO3 thin layer are made of the same material, which is z-cut LiNbO3 material.

[0017] The ITO electrode layer is divided into upper and lower layers, each with a thickness of 100nm. The lower ITO electrode is tightly bonded to the bottom of the LiNbO3 thin layer, and the upper ITO electrode is tightly bonded to the top of the LiNbO3 cylindrical array. No additional interface states are introduced, thus avoiding optical signal transmission loss.

[0018] The substrate layer includes, but is not limited to, one of SiO2 and Al2O3.

[0019] A method for fabricating a tunable narrowband filter based on a lithium niobate-liquid crystal integrated metasurface, characterized by the following steps:

[0020] 1) First, a thin layer of ITO is deposited on the SiO2 substrate by magnetron sputtering as the bottom electrode;

[0021] 2) Bonding LiNbO3 thin layers onto ITO thin layers;

[0022] 3) A mask layer for forming metasurface patterns on a thin layer of LiNbO3 is formed using electron beam lithography.

[0023] 4) Using magnetron sputtering, Cr is deposited on the photoresist as a protective layer;

[0024] 5) The LiNbO3 layer was etched using inductively coupled plasma etching to obtain the metasurface pattern, and the protective layer was removed by cleaning.

[0025] 6) On another glass substrate, an ITO thin layer is deposited as the top electrode by magnetron sputtering to form the upper substrate;

[0026] 7) Coat the ITO surface of the upper substrate with an alignment layer made of Nylon-6 dissolved in 2,2,2-trichlor-oethanol;

[0027] 8) The upper substrate and the LiNbO3 metasurface are aligned and bonded using a high-precision pick-and-place machine;

[0028] 9) Fill the metasurface gaps in the liquid crystal cell with nematic liquid crystal.

[0029] In step 1), the ITO target is bombarded with high-energy Ar⁺ ions in the magnetron sputtering vacuum chamber to sputter out the target atoms, which are then deposited on a substrate heated to 400°C to form an ITO electrode.

[0030] In step 2), the LiNbO3 material is bonded to ITO, and then thermal annealing is performed to separate the LiNbO3 thin layer bonded to ITO from the LiNbO3 material.

[0031] In step 3), the bonded LiNbO3 thin layer is cleaned to remove surface impurities; then, the LiNbO3 thin layer is subjected to a spin coating process, and approximately 200 nm of PMMA is spin-coated; the designed metasurface pattern is transferred to the photoresist using an electron beam lithography method.

[0032] In step 4), a 70 nm thick layer of metal Cr is deposited on the photoresist by magnetron sputtering; the excess metal is stripped off, and the remaining Cr serves as a protective layer for etching.

[0033] Step 5) involves etching the LiNbO3 thin layer using inductively coupled plasma reactive ion etching; the etching gas is a mixture of CF4, Ar, and H2.

[0034] In step 6), an ITO electrode is prepared on another glass substrate by measurement and control sputtering, and the glass substrate forming the ITO electrode is the upper substrate.

[0035] In step 7), Nylon-6 is dissolved in 2,2,2-trichlor-oethanol and then spin-coated onto the ITO surface of the upper substrate. After a friction treatment, the substrate will have a low pre-tilt angle of about 0°. This substrate will serve as the upper substrate of the liquid crystal cell.

[0036] In step 8), the upper substrate and the LiNbO3 metasurface are aligned and bonded using a high-precision pick and place machine. After bonding, UV-curable epoxy frame adhesive is applied to the metasurface and the edge of the upper substrate. The frame adhesive is then thermally cured to form a sealed liquid crystal cell cavity.

[0037] In step 9), Merck E7 nematic liquid crystal with positive dielectric anisotropy is filled into the free space of the metasurface by means of capillary action.

[0038] Compared with the prior art, the advantages and effects of the present invention are as follows:

[0039] 1) This invention presents a LiNbO3-liquid crystal integrated metasurface tunable narrowband filter with outstanding electro-optic modulation intensity. Benefiting from the fact that the refractive indices of both LiNbO3 and liquid crystal change with the applied voltage, the modulation effect of the narrowband filter is significantly improved. Without the addition of liquid crystal, the modulation intensity of the tunable narrowband filter based on the lithium niobate metasurface is 0.03 nm / V; after integration with liquid crystal, the wavelength modulation intensity of the LiNbO3-liquid crystal integrated metasurface tunable narrowband filter reaches 0.6 nm / V.

[0040] 2) The tunable narrowband filter based on the LiNbO3-liquid crystal integrated metasurface achieves its filtering effect through resonance. The resonant mode is highly sensitive to the wavelength of the incident signal, which can greatly improve the resolution of the filtered signal. Resonance peak resolution (RPR) is an important indicator for evaluating the performance of a tunable narrowband filter. RPR is defined as the smallest distinguishable interval of transmitted wavelengths. The smaller the resonance peak resolution, the higher the accuracy that can be achieved in the filtering operation, and the better the filtering performance, which can better meet the application scenarios with stringent requirements for filtering effect. The narrowband filter based on the non-integrated LiNbO3 metasurface has an RPR of 0.2 nm, while the minimum RPR of the LiNbO3-liquid crystal integrated metasurface tunable narrowband filter can reach 0.1 nm, exhibiting higher modulation accuracy.

[0041] 3) The integrated design of the metasurface and liquid crystal effectively reduces the overall size of the filter, achieving miniaturization and integration of the device while ensuring its filtering performance. Currently reported liquid crystal integrated metasurfaces have relatively large structures, typically around 5 μm, due to the pursuit of high modulation efficiency. This invention integrates the LiNbO3 array with the liquid crystal, reducing the thickness to 0.4 μm while improving the modulation intensity.

[0042] 4) This invention combines a LiNbO3 metasurface with a liquid crystal, synergistically leveraging the electro-optic modulation advantages of both. This achieves efficient control of the filtering wavelength while significantly reducing device size, resulting in lightweight design. Furthermore, the fabrication process of this invention is simple and has the potential for large-scale application. Attached Figure Description

[0043] Figure 1 This is a front view of the narrowband filter structure based on the LiNbO3–liquid crystal integrated metasurface of the present invention.

[0044] Figure 2 This is a schematic diagram of the metasurface unit structure of the present invention.

[0045] Figure 3 This is a schematic diagram illustrating the fabrication process of the narrowband filter based on the integrated LiNbO3 metasurface of the present invention.

[0046] Figure 4 This is a top view of the narrowband filter structure based on the integrated LiNbO3 metasurface of the present invention.

[0047] In the figure, 1-substrate layer, 2-ITO electrode layer, 3-LiNbO3 thin layer, 4-LiNbO3 nanopillar array layer, 5-liquid crystal. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0049] Reference Figure 1 , Figure 2 The lithium niobate liquid crystal integrated metasurface tunable narrowband filter of the present invention includes: a substrate layer 1, an ITO electrode layer 2, a LiNbO3 thin layer 3, a LiNbO3 nanopillar array layer 4, and a liquid crystal 5;

[0050] The substrate layer 1, the ITO electrode layer 2, and the LiNbO3 thin layer 3 are vertically distributed from bottom to top, thus forming a multilayer structure from bottom to top.

[0051] ITO thin layer 2 serves as an electrode, located below LiNbO3 thin layer 3 and above LiNbO3 nanopillar array layer 4, respectively.

[0052] Both the LiNbO3 array layer 4 and the LiNbO3 thin layer 3 are made of LiNbO3 material, and both are z-cut LiNbO3 material. The LiNbO3 array layer 4 is obtained by etching the LiNbO3 thin layer 3.

[0053] The LiNbO3 array layer 4 consists of multiple periodically arranged LiNbO3 nanopillars, and the nanopillar structure is cylindrical nanopillars.

[0054] Each nanopillar is arranged adjacent to another nanopillar in the x and y directions with a period of p, and the spacing between two adjacent nanopillars is p. Each nanopillar has the same direction.

[0055] Liquid crystal 5 is filled between the LiNbO3 nanopillar array layers 4; the liquid crystal and the metasurface formed by the periodically arranged LiNbO3 nanopillars work together to filter the incident information.

[0056] Liquid crystal 5 is a nematic liquid crystal, which is uniformly filled and distributed between the nanopillars through a potting process, and its thickness is consistent with the height of the cylindrical nanopillars of the LiNbO3 nanopillar array layer 4.

[0057] The thickness of substrate 1 is 4.4 μm.

[0058] The thickness of electrode 2 is 50 ~ 300 nm.

[0059] The thickness of the LiNbO3 thin layer 3 is 100 nm, and the LiNbO3 is z-cut.

[0060] The dimensions of the cylindrical nanopillar unit structure in the LiNbO3 nanopillar array layer 4 are: height h ~ 300 nm, cylinder radius r ~ 333 nm, period p ~ 1200 nm; the circular nanopillars have a height of h, a cylinder radius of r, and are arranged at intervals of period p.

[0061] Substrate 1 is, but is not limited to, one of SiO2 or Al2O3;

[0062] Liquid crystal 5 is a nematic liquid crystal, which is uniformly filled and distributed between the nanopillars through a potting process, and its thickness is consistent with the height of the lithium niobate nanopillars.

[0063] The LiNbO3 array and liquid crystal form an integrated LiNbO3 metasurface, enabling the filtering of electromagnetic wave signals. This LiNbO3-liquid crystal integrated metasurface can excite resonant modes in specific frequency bands. Electromagnetic waves can efficiently transmit through the metasurface structure only when the frequency of the incident electromagnetic wave matches the resonant frequency of the metasurface unit. Electromagnetic waves deviating from the resonant frequency are significantly suppressed or attenuated, thus achieving frequency-selective filtering of electromagnetic waves. When an external driving voltage is applied to the ITO transparent electrodes located on the top and bottom of the metasurface, the refractive index of the liquid crystal and lithium niobate materials changes under the influence of the electric field, altering the equivalent optical parameters of the metasurface. This leads to a controllable shift in the resonant band of the metasurface, ultimately achieving real-time, dynamic modulation of the filter's operating wavelength.

[0064] The filter is a tunable band filter, allowing for adjustment of the filtering band. Using 1550nm as an example: the metasurface designed with the aforementioned dimensions can excite a resonance at 1550nm. When the wavelength of the incident light signal is 1550nm, the light energy can efficiently transmit through the metasurface structure. For incident light with wavelengths other than 1550nm, the transmission intensity is significantly suppressed, thus achieving frequency-selective filtering of electromagnetic waves. In this case, the filter's filtering wavelength is 1550nm. When an external driving voltage is applied to the ITO electrode, the refractive index of the liquid crystal and lithium niobate materials changes under the influence of the electric field, causing a shift in the resonant wavelength of the metasurface. For example, applying a 10V voltage changes the resonant wavelength of the metasurface to 1560nm, allowing only 1560nm light signals to pass through the structure. Therefore, the filter's filtering wavelength becomes 1560nm. By applying different voltage intensities, the filter wavelength based on this LiNbO3–liquid crystal integrated metasurface can be dynamically adjusted.

[0065] See Figure 4 The fabrication method of a tunable narrowband filter based on a LiNbO3–liquid crystal integrated metasurface includes the following specific steps:

[0066] 1) First, a thin layer of ITO is deposited on the SiO2 substrate (i.e., substrate layer 1) by magnetron sputtering to form the bottom ITO electrode layer 2;

[0067] 2) Bond the LiNbO3 thin layer (i.e., LiNbO3 thin layer 3) onto ITO (i.e., ITO electrode layer 2);

[0068] 3) A mask layer for forming metasurface patterns is formed on a LiNbO3 thin layer (i.e., LiNbO3 thin layer 3) using electron beam lithography.

[0069] 4) Using magnetron sputtering, Cr is deposited on the photoresist as a protective layer;

[0070] 5) Using inductively coupled plasma etching (ICP-C) to etch the LiNbO3 layer to obtain a metasurface pattern, and then cleaning to remove the protective layer, the LiNbO3 nanopillar array layer 4 is obtained. The LiNbO3 nanopillar array layer 4 is obtained by partially etching the LiNbO3 thin layer 3;

[0071] 6) On another glass substrate, an ITO thin layer is deposited as the top electrode by magnetron sputtering to form the upper substrate;

[0072] 7) Coat the ITO surface of the upper substrate with an alignment layer made of Nylon-6 dissolved in 2,2,2-trichlor-oethanol;

[0073] 8) The upper substrate and the LiNbO3 metasurface are aligned and bonded using a high-precision pick-and-place machine to form the top ITO electrode layer 2.

[0074] 9) The nematic liquid crystal is filled into the metasurface gap in the liquid crystal cell to form liquid crystal 5.

[0075] Example:

[0076] Fabrication of a Ga2O3 solar-blind ultraviolet photodetector based on a nonlinear metasurface.

[0077] The implementation steps of this embodiment are as follows:

[0078] Step 1) Deposit an ITO thin film as the bottom electrode

[0079] An ITO electrode is prepared by bombarding an ITO target with high-energy Ar⁺ ions in a magnetron sputtering vacuum chamber to sputter out target atoms, which are then deposited on a substrate heated to 400°C.

[0080] Step 2) Bond the LiNbO3 thin layer to the ITO layer.

[0081] The LiNbO3 material was bonded to ITO, and then thermal annealing was performed to separate the LiNbO3 thin layer bonded to ITO from the LiNbO3 material.

[0082] Step 3) Photolithography of LiNbO3 thin layer

[0083] The bonded LiNbO3 thin layer was cleaned to remove surface impurities. Subsequently, the LiNbO3 thin layer underwent a spin-coating process, followed by the spin-coating of approximately 200 nm of PMMA. The designed metasurface pattern was then transferred to the photoresist using electron beam lithography.

[0084] Step 4) Evaporate Cr to create a protective layer

[0085] A 70 nm thick layer of metallic Cr was deposited on the photoresist by magnetron sputtering. The excess metal was stripped away, leaving the Cr as a protective layer for etching.

[0086] Step 5) Etching to form a LiNbO3 metasurface

[0087] The LiNbO3 thin layer was etched using inductively coupled plasma reactive ion etching (ICP-IR). The etching gas was a mixture of CF4, Ar, and H2.

[0088] Step 6) Fabrication of the top ITO electrode

[0089] An ITO electrode was fabricated on another glass substrate by controlled sputtering, with the glass substrate forming the ITO electrode serving as the upper substrate.

[0090] Step 7) Spin-coating the alignment layer onto the top ITO electrode

[0091] Nylon-6 was dissolved in 2,2,2-trichlor-oethanol and then spin-coated onto the ITO surface of the upper substrate as an alignment layer. After a rubbing process, the substrate will have a low pre-tilt angle of about 0°. This substrate will serve as the upper substrate of the liquid crystal cell.

[0092] Step 8) Bonding the upper substrate to the LiNbO3 metasurface

[0093] A high-precision pick-and-place machine is used to align and bond the upper substrate to the LiNbO3 metasurface. After bonding, a UV-curable epoxy frame adhesive is applied to the edges of the metasurface and the upper substrate. The frame adhesive is then thermo-cured to form a sealed liquid crystal cell cavity.

[0094] Step 9) Liquid Crystal Filling

[0095] Merck E7 nematic liquid crystal with positive dielectric anisotropy is filled into the free space of the metasurface by means of capillary action.

[0096] The above descriptions are merely a few preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A tunable narrow-band filter based on lithium niobate-liquid crystal integrated metasurface, characterized in that: It includes a substrate layer (1), an ITO electrode layer (2), a LiNbO3 thin layer (3), a LiNbO3 nanopillar array layer (4), and a liquid crystal (5); the ITO electrode layer (2) is disposed on the upper side of the substrate layer (1), the LiNbO3 thin layer (3) is disposed on the upper side of the ITO electrode layer (2), the LiNbO3 nanopillar array layer (4) and the liquid crystal (5) are disposed on the upper side of the LiNbO3 thin layer (3), the ITO electrode layer (2) is disposed on the upper side of the LiNbO3 nanopillar array layer (4), and the liquid crystal (5) and the LiNbO3 nanopillar array layer (4) are located between the upper and lower ITO electrode layers (2).

2. The lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 1, characterized in that: The LiNbO3 nanopillar array layer (4), LiNbO3 thin layer (3), and substrate layer (1) are vertically distributed from top to bottom; the liquid crystal (5) is liquid and distributed between the LiNbO3 nanopillar array layer (4); the ITO electrode layer (2) is distributed on the upper and lower sides of the LiNbO3 thin layer (3) and the LiNbO3 nanopillar array layer-liquid crystal integrated metasurface.

3. The LiNO3-LC integrated metasurface tunable narrowband filter of claim 2, wherein: The LiNbO3 nanopillar array layer (4) is composed of multiple periodically arranged LiNbO3 nanopillars, and the nanopillar structure is a cylindrical nanopillar; each nanopillar is arranged adjacent to each other in the x and y directions with a period of p, and the spacing between two adjacent nanopillars is p, and each nanopillar is in the same direction; liquid crystal (5) fills the space between adjacent nanopillars, and the liquid crystal (5) and the metasurface formed by the periodically arranged LiNbO3 nanopillars work together to filter the incident information.

4. The lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 3, characterized in that: The liquid crystal (5) is a nematic liquid crystal, which is uniformly filled and distributed between the nanopillars by a potting process, and its thickness is consistent with the height of the LiNbO3 nanopillars.

5. The lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 4, characterized in that: The unit structure dimensions of the cylindrical nanopillars are: height h ~ 300 nm, cylinder radius r ~ 333 nm, and spacing period p ~ 1200 nm.

6. The lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 5, characterized in that: The LiNbO3 thin layer (3) is placed below the metasurface. The LiNbO3 cylindrical array is obtained by partially etching the upper part of the LiNbO3 thin layer. Both the LiNbO3 metasurface and the LiNbO3 thin layer (3) are made of the same material, which is z-cut LiNbO3 material.

7. The lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 6, characterized in that: The thickness of the two ITO layers (2) is 100 nm. The bottom ITO electrode is tightly bonded to the bottom of the LiNbO3 thin layer and the top ITO electrode is tightly bonded to the top of the LiNbO3 cylindrical array.

8. The lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 7, characterized in that: The substrate layer (1) includes, but is not limited to, one of SiO2 and Al2O3.

9. A method for fabricating a tunable narrowband filter based on a lithium niobate-liquid crystal integrated metasurface, characterized in that: Includes the following steps: 1) First, a thin layer of ITO is deposited on the SiO2 substrate by magnetron sputtering as the bottom electrode; 2) Bonding LiNbO3 thin layers onto ITO thin layers; 3) A mask layer for forming metasurface patterns on a thin layer of LiNbO3 is formed using electron beam lithography. 4) Using magnetron sputtering, Cr is deposited on the photoresist as a protective layer; 5) The LiNbO3 layer was etched using inductively coupled plasma etching to obtain the metasurface pattern, and the protective layer was removed by cleaning. 6) On another glass substrate, an ITO thin layer is deposited as the top electrode by magnetron sputtering to form the upper substrate; 7) Coat the ITO surface of the upper substrate with an alignment layer made of Nylon-6 dissolved in 2,2,2-trichlor-oethanol; 8) The upper substrate and the LiNbO3 metasurface are aligned and bonded using a high-precision pick-and-place machine; 9) Fill the metasurface gaps in the liquid crystal cell with nematic liquid crystal.

10. The fabrication method of the lithium niobate-liquid crystal integrated metasurface tunable narrowband filter according to claim 9, characterized in that: In step 1), the ITO target is bombarded with high-energy Ar⁺ ions in the magnetron sputtering vacuum chamber to sputter out the target atoms, which are then deposited on a substrate heated to 400°C to form an ITO electrode. In step 2), the LiNbO3 material is bonded to ITO, and then thermal annealing is performed to separate the LiNbO3 thin layer bonded to ITO from the LiNbO3 material. Step 3) involves cleaning the bonded LiNbO3 thin layer to remove surface impurities; Subsequently, the LiNbO3 thin layer was subjected to a homogenization process, and then approximately 200 nm of PMMA was spin-coated. The designed metasurface pattern is transferred to photoresist using electron beam lithography. In step 4), a 70 nm thick layer of metallic Cr is deposited on the photoresist by magnetron sputtering; Excess metal is stripped away, leaving Cr as a protective layer for etching; Step 5) involves etching the LiNbO3 thin layer using inductively coupled plasma reactive ion etching. The etching gas is a mixture of CF4, Ar, and H2; In step 6), an ITO electrode is prepared on another glass substrate by measurement and control sputtering, and the glass substrate forming the ITO electrode is the upper substrate. In step 7), Nylon-6 is dissolved in 2,2,2-trichlor-oethanol and then spin-coated onto the ITO surface of the upper substrate. After a friction treatment, the substrate will have a low pre-tilt angle of about 0°. This substrate will serve as the upper substrate of the liquid crystal cell. In step 8), the upper substrate and the LiNbO3 metasurface are aligned and bonded using a high-precision pick and place machine. After bonding, UV-curable epoxy frame adhesive is applied to the metasurface and the edge of the upper substrate. The frame adhesive is then thermally cured to form a sealed liquid crystal cell cavity. In step 9), Merck E7 nematic liquid crystal with positive dielectric anisotropy is filled into the free space of the metasurface by means of capillary action.

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