Thin film lithium niobate electro-optic modulator and method of making the same

Abstract

The application discloses a thin film lithium niobate electro-optic modulator and a preparation method thereof. The modulator comprises, from bottom to top, a substrate layer, a first high refractive index layer, a low refractive index layer, a metal electrode layer and a second high refractive index layer. The low refractive index layer is a thin film lithium niobate layer. The widths of the substrate layer, the first high refractive index layer and the low refractive index layer are equal. Light forms a hybrid plasmonic waveguide mode in the metal electrode layer and all the layers below the metal electrode layer. The light field is localized in the low refractive index layer, and the nonlinear interaction is enhanced. The widths of the metal electrode layer and the second high refractive index layer are equal and smaller than that of the substrate layer. Light forms a conventional plasmonic mode in the metal electrode layer and the second high refractive index layer. The light field is distributed between the interface of the metal electrode layer and the second high refractive index layer. The light field in the two modes interferes out of phase to form a coupling hybrid plasmonic mode, which concentrates the light field in the low refractive index layer, reduces the proportion of the light field in the metal electrode layer and further reduces the propagation loss.

Description

Technical Field

[0001] This invention relates to the field of integrated optoelectronic devices, and more particularly to a thin-film lithium niobate electro-optic modulator and its fabrication method. Background Technology

[0002] Electro-optic modulators are key components in optical communication, optical computing, and photonic integrated circuits. Lithium niobate, due to its excellent electro-optic effect and low optical loss, is one of the most commonly used materials in electro-optic modulators and has relatively mature and widespread commercial applications. However, traditional bulk lithium niobate modulators are difficult to meet the requirements of modern on-chip photonic integration due to their large device size.

[0003] With the maturation of thin-film lithium niobate fabrication technology, high-quality thin-film lithium niobate can be bonded to insulating substrates, leading to a rapid growth in electro-optic modulators based on thin-film lithium niobate. This is because thin-film lithium niobate not only inherits the excellent optoelectronic properties of bulk lithium niobate, but also significantly reduces the size of thin-film lithium niobate-based waveguides, substantially improving the localization of the optical field and the device integration, laying the foundation for the development of highly integrated micro / nano electro-optic devices.

[0004] However, in conventional thin-film lithium niobate electro-optic modulators, the dielectric waveguide mode volume is still relatively large and the electro-optic spatial overlap is relatively weak. How to further reduce the mode volume to shrink the device size and improve the electro-optic coupling to enhance the device performance is the current key research direction in this field.

[0005] In recent years, photonic crystals and plasmons have been introduced into modulators to improve optical field localization and electro-optic coupling efficiency. Plasmon structures, in particular, significantly enhance the interaction strength between light and matter by generating a large electric field at the subwavelength scale, which is beneficial for the miniaturization of electro-optic devices. However, the localization of the plasmon optical field in the metal electrode layer inevitably leads to significant transmission losses. Summary of the Invention

[0006] The main objective of this invention is to provide a thin-film lithium niobate electro-optic modulator and its preparation method that can reduce plasmonic optical field transmission loss and enhance electro-optic modulation efficiency.

[0007] The technical solution adopted in this invention is:

[0008] A thin-film lithium niobate electro-optic modulator is provided, comprising, from bottom to top, a substrate layer, a first high refractive index layer, a low refractive index layer, a metal electrode layer, and a second high refractive index layer, wherein the low refractive index layer is a thin-film lithium niobate layer;

[0009] The substrate layer, the first high refractive index layer and the low refractive index layer have equal widths. Light forms a hybrid plasmonic waveguide mode in the metal electrode layer and all layers below it. The light field is localized in the low refractive index layer, which enhances the nonlinear interaction.

[0010] The widths of the metal electrode layer and the second high refractive index layer are the same and smaller than those of the substrate layer. Light forms conventional plasmon modes in the metal electrode layer and the second high refractive index layer, and the light field is distributed at the interface between the metal electrode layer and the second high refractive index layer.

[0011] The out-of-phase interference of the light fields under the two modes forms a coupled hybrid plasmon mode, which concentrates the light field in the low refractive index layer and reduces the proportion of the light field in the metal electrode layer.

[0012] According to the above technical solution, the metal electrode layer includes two strip-shaped signal electrodes, and a second high refractive index layer is provided on the strip-shaped signal electrodes. The voltage magnitudes of the two strip-shaped signal electrodes are equal and the directions are opposite.

[0013] According to the above technical solution, the strip signal electrode is divided into two types according to the power supply method: coplanar electrode and microstrip line. When coplanar electrode is used for power supply, the metal electrode layer also includes three strip ground electrodes, and the three strip ground electrodes and the two strip signal electrodes are placed alternately at equal intervals. When microstrip line is used for power supply, the material of the first high refractive index layer is highly doped silicon, which serves as the ground electrode.

[0014] Following the above technical solution, the material of the metal electrode layer is gold.

[0015] Following the above technical solution, the material of the low refractive index layer is Z-cut lithium niobate.

[0016] Following the above technical solution, the substrate material is silicon dioxide.

[0017] Following the above technical solution, the materials of the first high refractive index layer and the second high refractive index layer are silicon.

[0018] The present invention also provides a method for fabricating a thin-film lithium niobate electro-optic modulator, comprising the following steps:

[0019] Forming a substrate layer;

[0020] A first high refractive index layer and a low refractive index layer are sequentially formed on the substrate, wherein the low refractive index layer is a thin film lithium niobate layer;

[0021] A metal electrode layer and a second high refractive index layer are deposited on a low refractive index layer;

[0022] The second high refractive index layer and the metal electrode layer are etched to form two strip waveguides, which also serve as signal electrodes.

[0023] Three metal ground electrodes are deposited at equal intervals in the middle and on both sides of the two strip signal electrodes.

[0024] The present invention also provides a method for fabricating a thin-film lithium niobate electro-optic modulator, comprising the following steps:

[0025] Forming a substrate layer;

[0026] A first high-refractive-index layer is formed on the substrate using highly doped silicon, which serves as the ground electrode.

[0027] A low-refractive-index layer is formed on a highly doped silicon layer, wherein the low-refractive-index layer is a thin-film lithium niobate layer;

[0028] A metal electrode layer and a second high refractive index layer are deposited on a low refractive index layer;

[0029] The etching of the second high refractive index layer and the metal electrode layer pattern forms two strip waveguides, which also serve as signal electrodes.

[0030] Following the above technical solution, two strip waveguides are formed by etching the second high refractive index layer and the metal electrode layer pattern through multiple electron beam overlay and reactive ion beam etching.

[0031] The beneficial effects of this invention are as follows: This invention combines low-loss plasmonic modes with thin-film lithium niobate exhibiting strong electro-optic effects, resulting in a more integrated novel lithium niobate electro-optic modulator. Specifically, a conventional plasmonic waveguide structure and a hybrid plasmonic waveguide structure are formed in the electro-optic modulator. When light propagates within these structures, two modes are generated, and the light from these two modes interferes with each other to form coupled hybrid plasmonic modes. An unexpected effect is that this composite structure can concentrate the light field on a low-refractive-index thin-film lithium niobate layer, reducing the proportion of the light field in the metal and simultaneously improving the spatial coupling between the electric and optical fields. Therefore, this invention has advantages such as low device transmission loss and high modulation efficiency. Furthermore, the strong electric field of the lithium niobate layer overlaps significantly with the optical field, resulting in high device modulation efficiency and facilitating device miniaturization.

[0032] Furthermore, by forming spaced signal electrodes and ground electrodes on the metal electrode layer, with the voltages of adjacent signal electrodes being opposite, an unexpected effect is that the optical field is more localized in the thin film lithium niobate layer by using two coupled hybrid plasmon waveguides formed by adjacent signal electrodes and the first high-refractive-index layer and the low-refractive-index thin film lithium niobate layer. Under the action of the electric field, the refractive index of the thin film lithium niobate layer changes. Since the electric field directions on both sides are opposite, the phase changes of the two waveguides are opposite, which can achieve double phase difference, forming the same effect as the push-pull effect, which can improve the modulation efficiency and device integration.

[0033] Furthermore, the first high refractive index layer is set to be highly doped silicon as the ground electrode. The metal electrode layer includes two signal electrodes with opposite voltages. Unexpectedly, using highly doped silicon as the ground electrode can effectively reduce waveguide loss. At the same time, the optical field is localized in the lithium niobate layer by using two coupled hybrid plasmon waveguides formed by the two signal electrodes. Under the action of the electric field, the refractive index of lithium niobate changes. The two signal electrodes have opposite voltages and share a ground electrode, which can improve the modulation efficiency and reduce the device size.

[0034] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a three-dimensional schematic diagram of a thin-film lithium niobate electro-optic modulator according to an embodiment of the present invention;

[0037] Figure 2 yes Figure 1 A schematic diagram of the coupled hybrid plasmon light field of a thin-film lithium niobate electro-optic modulator, where the light field is concentrated in the lithium niobate region;

[0038] Figure 3 This is a cross-sectional structural schematic diagram of a thin-film lithium niobate electro-optic modulator according to an embodiment of the present invention;

[0039] Figure 4 yes Figure 3 Schematic diagram of the optical field of a lithium niobate-plasmon modulator;

[0040] Figure 5 yes Figure 3 Schematic diagram of the electric field of the lithium niobate-plasmon modulator structure;

[0041] Figure 6 A cross-sectional structural schematic diagram of a thin-film lithium niobate electro-optic modulator according to another embodiment of the present invention;

[0042] Figure 7 yes Figure 6 Schematic diagram of the optical field of a lithium niobate-plasmon modulator;

[0043] Figure 8 yes Figure 6 A schematic diagram of the electric field of a lithium niobate-plasmon modulator.

[0044] In the figure: 10, substrate layer; 20, first high refractive index layer; 30, low refractive index layer; 40, metal electrode layer; 41, ground electrode; 42, signal electrode; 50, second high refractive index layer. Detailed Implementation

[0045] 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.

[0046] It should be noted that the illustrations provided in the embodiments of the present invention are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the number, shape and size of the components in actual implementation. In actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0047] In this invention, it should also be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first" and "second" are used only for descriptive and distinguishing purposes and should not be construed as indicating or implying relative importance.

[0048] Furthermore, it should be noted that the features of the various embodiments of the present invention can be combined or integrated in whole or in part, and as those skilled in the art will understand, they can interact and operate in different ways. Each embodiment can be implemented independently of each other or in association with one another.

[0049] This invention features both extremely small optical field mode volume and extremely low transmission loss. By integrating thin-film lithium niobate with a hybrid plasmonic waveguide, the structural parameters are adjusted to allow the mode optical field to be significantly concentrated in the nonlinear lithium niobate material layer, thereby further improving the performance of the electro-optic modulation device and providing an effective solution for on-chip high-density photonic integration.

[0050] like Figure 1 As shown, the thin-film lithium niobate electro-optic modulator of this embodiment of the invention includes, from bottom to top, a substrate layer, a first high refractive index layer, a low refractive index layer, a metal electrode layer, and a second high refractive index layer, wherein the low refractive index layer is a thin-film lithium niobate layer.

[0051] The substrate, the first high-refractive-index layer and the low-refractive-index layer have equal widths. Light forms a hybrid plasmonic waveguide mode in the metal electrode layer and all layers below it. The optical field is localized in the low-refractive-index layer, which enhances the nonlinear interaction.

[0052] The metal electrode layer and the second high refractive index layer have the same width and are smaller than the substrate layer. Light forms a conventional plasmon mode in the metal electrode layer and the second high refractive index layer, and the light field is distributed at the interface between the metal electrode layer and the second high refractive index layer.

[0053] The out-of-phase interference of the light fields under the two modes forms a coupled hybrid plasmon mode, which concentrates the light field in the low refractive index layer and reduces the proportion of the light field in the metal electrode layer.

[0054] like Figure 1 As shown, the thin-film lithium niobate electro-optic modulator of this embodiment includes, from bottom to top, a substrate layer 10, a first high refractive index layer 20, a low refractive index layer 30, a metal electrode layer 40, and a second high refractive index layer 50.

[0055] In this design, the substrate layer 10, the first high-refractive-index layer 20, and the low-refractive-index layer 30 have equal widths, while the metal electrode layer 40 and the second high-refractive-index layer 50 have the same width, which is smaller than the width of the substrate layer. Light forms a hybrid plasmonic waveguide mode in the metal electrode layer 40 and all layers below it, with the light field localized in the low-refractive-index layer, enhancing nonlinear interactions. The metal electrode layer 40 and the second high-refractive-index layer 50 have the same width, which is smaller than the substrate layer, and light forms a conventional plasmonic mode in both layers, with the light field distributed at the interface between the metal electrode layer 40 and the second high-refractive-index layer 50. The out-of-phase interference of the light fields in the two modes forms a coupled hybrid plasmonic mode, concentrating the light field in the low-refractive-index layer 30 and reducing the proportion of the light field in the metal electrode layer 40.

[0056] Specifically, the substrate layer 10 can be made of silicon dioxide; the first high-refractive-index layer 20 can be made of silicon; the low-refractive-index layer 30 can be made of Z-cut lithium niobate; the metal electrode layer 40 can be made of gold; and the second high-refractive-index layer 50 can be made of silicon. The width of the substrate layer 10 is equal to the width of the first high-refractive-index layer 20 and the low-refractive-index layer 30, and the width of the metal electrode layer 40 is equal to the width of the second high-refractive-index layer 50. The second high-refractive-index layer 50 and the metal electrode layer 40 exhibit a conventional surface plasmon polariton (SPP) mode, with its optical field distributed at the metal-silicon interface. The first high-refractive-index layer 20, the low-refractive-index layer 30, and the metal electrode layer 40 form a hybrid plasmonic waveguide (HPW) mode, with its optical field localized in the low-refractive-index layer 30 (i.e., the lithium niobate layer) to enhance nonlinear interactions.

[0057] The two modes interfere with each other to form coupled hybrid plasmon modes, which reduces the proportion of the light field in the metal. Therefore, while reducing device transmission loss, the light field is concentrated in the lithium niobate layer, improving device control efficiency. Figure 2 This is a schematic diagram of the optical field of a coupled hybrid plasmonic waveguide (CHPW), with a loss of 0.15 dB / μm, which is significantly lower than the previous results (0.35 dB / μm).

[0058] To construct a complete Mach-Zehnder type electro-optic modulation device, this invention designs two electrode arrangement schemes. Design Scheme 1: A two-dimensional structure diagram of the coplanar electrode type is shown below. Figure 3 As shown, the structure from bottom to top consists of a substrate layer 10, a first high-refractive-index layer 20, a low-refractive-index layer 30, a metal electrode layer 40, and a second high-refractive-index layer 50, corresponding to a silicon dioxide substrate, a high-refractive-index silicon layer, a low-refractive-index Z-cut lithium niobate layer, a gold electrode layer, and a high-refractive-index silicon layer, respectively. Electrodes 2 and 4 in the middle are signal electrodes 42 (represented by the letter S), and electrodes 1, 3, and 5 are ground electrodes 41 (represented by the letter G), forming a GGSSG electrode structure. The voltages of signal electrode 2 and electrode 4 are opposite but equal. Above the signal electrodes is a high-refractive-index silicon layer, and the metal layer has the same width as the high-refractive-index silicon layer above it. The device operates by using two coupled hybrid plasmon waveguides to localize the optical field more extensively within the thin-film lithium niobate layer. Under the influence of an electric field, the refractive index of the thin-film lithium niobate layer changes. Because the electric field directions on both sides are opposite, the phase changes of the two waveguides are opposite, achieving a double phase difference, forming an effect similar to the push-pull effect, which can improve modulation efficiency and device integration.

[0059] In a preferred embodiment, the structure from bottom to top consists of: a substrate made of silicon dioxide, 5.5 μm wide and 500 nm thick; a first high-refractive-index layer made of silicon, 5.5 μm wide and 200 nm thick; a low-refractive-index layer made of Z-cut lithium niobate, 5.5 μm wide and 110 nm thick; a metal layer serving as electrodes made of gold, with electrodes 2 and 4 in the middle being signal electrodes, and electrodes 1, 3, and 5 being ground electrodes, all with equal spacing, a width of 200 nm, a thickness of 40 nm, and a spacing of 1 μm; and a second high-refractive-index layer made of silicon above electrodes 2 and 4, 200 nm wide and 300 nm thick. Under this structure, V π L is 0.17 volt-cm, and the overall transmission loss of the device is 0.37 dB / μm. A schematic diagram of the optical field is shown below. Figure 4 As shown, the light field can be localized within the lithium niobate layer. A schematic diagram of the electric field is shown below. Figure 5As shown, the lithium niobate layer has a strong electric field that overlaps significantly with the optical field, resulting in high device modulation efficiency and facilitating device miniaturization.

[0060] The fabrication method of the thin-film lithium niobate electro-optic modulator in this scheme mainly includes the following steps:

[0061] Step 1: Form the substrate layer;

[0062] Step 2: Deposit a metal electrode layer and a second high refractive index layer on the low refractive index layer;

[0063] Step 3: Multiple electron beam overlay etching and reactive ion beam etching are used to pattern the second high refractive index layer and the metal electrode layer to form two strip waveguides, which also serve as signal electrodes.

[0064] Step 4: Evaporate three metal ground electrodes at equal intervals in the middle and on both sides of the two signal electrodes.

[0065] Design Scheme 2: A schematic diagram of the two-dimensional structure of the microstrip line is shown below. Figure 6 As shown, the structure from bottom to top consists of a substrate 10, a ground electrode 41 (i.e., the first high refractive index layer), a low refractive index layer 30, a signal electrode 42, and a second high refractive index layer 50, corresponding to the silicon dioxide substrate, the highly doped silicon ground electrode layer (first high refractive index layer), the low refractive index Z-cut lithium niobate layer, the gold electrode layer, and the high refractive index silicon layer, respectively. The ground electrode layer, the first high refractive index layer 20, and the low refractive index layer 30 are not etched and have the same width as the substrate 10. The signal electrode 42 and the second high refractive index layer 50 have the same width but are smaller than the width of the substrate 10. The device operates as follows: using a highly doped silicon layer as the ground electrode effectively reduces waveguide loss and increases the electric field application efficiency. Simultaneously, two coupled hybrid plasmon waveguides localize the optical field within the lithium niobate layer. Under the influence of the electric field, the refractive index of the lithium niobate changes, the voltages of the two signal electrodes are opposite, and they share a single ground electrode, which improves modulation efficiency and reduces device size.

[0066] In a preferred embodiment, the structure from bottom to top consists of a substrate made of silicon dioxide, with a width of 5.5 micrometers and a thickness of 500 nanometers; and a first high-refractive-index layer made of a material with a doping concentration of 10. 20 cm -3 A highly doped silicon layer, 5.5 μm wide and 200 nm thick, serves as the ground electrode; a low refractive index layer, made of Z-cut lithium niobate, is 5.5 μm wide and 100 nm thick; a metal layer, made of gold, serves as the electrode, with a 0.35 μm spacing between electrodes 1 and 2, and an electrode width of 200 nm and a thickness of 40 nm; a second high refractive index layer, made of silicon, is 200 nm wide and 300 nm thick, above the signal electrodes 1 and 2. Under this structure, V π L is 0.1 volt-cm, and the transmission loss is 0.12 dB / μm. A schematic diagram of the optical field is shown below. Figure 7As shown, the electric field diagram is as follows: Figure 8 As shown, the small electrode spacing of this device is more conducive to device miniaturization.

[0067] The fabrication method of the thin-film lithium niobate electro-optic modulator in this scheme includes the following steps:

[0068] Step 1: Form the substrate layer;

[0069] Step 2: Form a first high refractive index layer on the substrate using highly doped silicon, which serves as the ground electrode;

[0070] Step 3: Form a low refractive index layer on the highly doped silicon layer, wherein the low refractive index layer is a thin film lithium niobate layer;

[0071] Step 4: Evaporate a metal electrode layer and a second high refractive index layer onto the low refractive index layer;

[0072] Step 5: Multiple electron beam etching and reactive ion beam etching are used to pattern the second high refractive index layer and the metal electrode layer to form two strip waveguides, which also serve as signal electrodes.

[0073] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0074] The order of the steps in the above embodiments does not imply the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0075] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A thin-film lithium niobate electro-optic modulator, characterized in that, From bottom to top, it includes a substrate layer, a first high refractive index layer, a low refractive index layer, a metal electrode layer, and a second high refractive index layer, wherein the low refractive index layer is a thin film lithium niobate layer; The substrate layer, the first high refractive index layer and the low refractive index layer have equal widths. Light forms a hybrid plasmonic waveguide mode in the metal electrode layer and all layers below it. The light field is localized in the low refractive index layer, which enhances the nonlinear interaction. The widths of the metal electrode layer and the second high refractive index layer are the same and smaller than those of the substrate layer. Light forms conventional plasmon modes in the metal electrode layer and the second high refractive index layer, and the light field is distributed at the interface between the metal electrode layer and the second high refractive index layer. The out-of-phase interference of the light fields under the two modes forms a coupled hybrid plasmon mode, which concentrates the light field in the low refractive index layer and reduces the proportion of the light field in the metal electrode layer.

2. The thin-film lithium niobate electro-optic modulator according to claim 1, characterized in that, The metal electrode layer includes two strip-shaped signal electrodes, each with a second high-refractive-index layer, and the voltages of the two strip-shaped signal electrodes are equal in magnitude and opposite in direction.

3. The thin-film lithium niobate electro-optic modulator according to claim 2, characterized in that, The strip signal electrodes are divided into two types according to the power supply method: coplanar electrodes and microstrip lines. When coplanar electrodes are used for power supply, the metal electrode layer also includes three strip ground electrodes, and the three strip ground electrodes and the two strip signal electrodes are placed alternately at equal intervals. When microstrip lines are used for power supply, the material of the first high refractive index layer is highly doped silicon, which serves as the ground electrode.

4. The thin-film lithium niobate electro-optic modulator according to claim 1, characterized in that, The material of the metal electrode layer is gold.

5. The thin-film lithium niobate electro-optic modulator according to claim 1, characterized in that, The low-refractive-index layer is made of Z-cut lithium niobate.

6. The thin-film lithium niobate electro-optic modulator according to claim 1, characterized in that, The substrate is made of silicon dioxide.

7. The thin-film lithium niobate electro-optic modulator according to claim 1, characterized in that, The first and second high-refractive-index layers are made of silicon.

8. A method for fabricating a thin-film lithium niobate electro-optic modulator, characterized in that, Includes the following steps: Forming a substrate layer; A first high refractive index layer and a low refractive index layer are sequentially formed on the substrate, wherein the low refractive index layer is a thin film lithium niobate layer; A metal electrode layer and a second high refractive index layer are deposited on a low refractive index layer; The second high refractive index layer and the metal electrode layer are etched to form two strip waveguides, which also serve as signal electrodes. Three metal ground electrodes are deposited at equal intervals in the middle and on both sides of the two strip signal electrodes.

9. A method for fabricating a thin-film lithium niobate electro-optic modulator, characterized in that, Includes the following steps: Forming a substrate layer; A first high-refractive-index layer is formed on the substrate using highly doped silicon, which serves as the ground electrode. A low-refractive-index layer is formed on a highly doped silicon layer, wherein the low-refractive-index layer is a thin-film lithium niobate layer; A metal electrode layer and a second high refractive index layer are deposited on a low refractive index layer; The etching of the second high refractive index layer and the metal electrode layer pattern forms two strip waveguides, which also serve as signal electrodes.

10. The method for fabricating a thin-film lithium niobate electro-optic modulator according to claim 8 or 9, characterized in that, Specifically, two strip waveguides are formed by etching the second high refractive index layer and the metal electrode layer using multiple electron beam overlay and reactive ion beam etching processes.

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