Thin-film lithium niobate electro-optical modulator and preparation method thereof

Abstract

The invention discloses a thin-film lithium niobate electro-optical modulator and a preparation method thereof, and belongs to the technical field of high-speed electro-optical modulators, the electro-optical modulator comprises a substrate layer, a silicon oxide interlayer, a thin-film lithium niobate layer, a silicon oxide coating layer and an electrode layer, wherein the electrode layer comprises a signal electrode, a first ground electrode, a second ground electrode and a plurality of L-shaped interdigital slow wave electrode structures which are periodically arranged in a staggered manner; for any L-shaped interdigital slow wave electrode structure, the first L-shaped electrode and the third L-shaped electrode are arranged in a crossed manner, and the second L-shaped electrode and the fourth L-shaped electrode are arranged in a crossed manner. According to the thin-film lithium niobate electro-optical modulator and the preparation method thereof provided by the invention, the refractive index of a microwave signal is improved, the problem of speed mismatch caused by a low-loss substrate is solved, the technical difficulty that performance tradeoff between half-wave voltage and bandwidth is limited in the prior art is further broken through, and the electro-optical bandwidth of the modulator is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed electro-optic modulators, and in particular to a thin-film lithium niobate electro-optic modulator and a preparation method thereof. Background Art

[0002] As the core photoelectric conversion device in optical interconnect systems, the performance of electro-optical modulators directly determines the signal transmission efficiency and energy consumption of data centers, artificial intelligence computing clusters, and radio frequency photonic systems. Currently, with the upward evolution of single-channel communication rates and the urgent need for high-frequency (greater than 100 GHz) linear modulation in microwave photonics, the development of modulators with ultra-low drive voltage, ultra-wideband response, and compact size has become the key to breaking through the bottleneck of system integration.

[0003] However, traditional lithium niobate modulators are limited by the weak optical field confinement waveguide structure. In order to avoid the metal electrode absorption loss, a larger signal-ground electrode spacing is usually required, which leads to a significant attenuation of the microwave electric field intensity in the optical waveguide region. For C-band modulators, their half-wave voltage-length product is generally greater than 10V·cm, and the modulation efficiency is low. Although the thin-film lithium niobate platform compresses the electrode spacing to the micron level through high-refractive index difference waveguides, reducing the half-wave voltage-length product to 2V·cm, greatly improving the modulation efficiency, further reducing the spacing will cause the metal absorption loss to increase, becoming a physical bottleneck for efficiency improvement. At the same time, the high performance of TFLN modulators is still limited by the properties of the substrate material. Studies have found that in the structural design of traditional silicon-based thin-film lithium niobate electro-optical modulators, a thicker thermal silicon oxide layer can achieve speed matching between microwaves and light waves, but the dielectric properties of the silicon substrate (ε r ≈11.9) limits the optimization space of microwave performance. Using quartz substrate to design thin film lithium niobate electro-optical modulator can take advantage of the low dielectric constant (ε r ≈4.5) and low microwave loss (tanδ<10 -4 ) characteristics, suppressing RF energy dissipation, while its thermomechanical performance and wafer cost are compatible with large-scale manufacturing needs. However, in a typical quartz-based X-cut LN platform, the microwave refractive index of traditional GSG electrodes (1.7-1.9) is significantly lower than the optical refractive index (2.2-2.3), resulting in a velocity mismatch. This electro-optical velocity difference directly leads to cumulative microwave-optical phase deviation, becoming a key bottleneck restricting high-frequency performance improvements.

[0004] Therefore, to meet the higher performance requirements of modern communication systems, a new electro-optic modulator design is urgently needed. This design should simultaneously address the metal absorption loss problem caused by reducing component spacing and the speed mismatch problem caused by low-loss substrates, thereby breaking through the performance trade-off between half-wave voltage and bandwidth. Summary of the Invention

[0005] The present invention provides a thin-film lithium niobate electro-optic modulator and a preparation method thereof, which can solve the technical problem of the limited performance trade-off between half-wave voltage and bandwidth in the prior art, improve the refractive index of microwave signals, and realize the improvement of the electro-optic bandwidth of the modulator.

[0006] The present invention provides a thin-film lithium niobate electro-optic modulator, comprising a substrate layer, a silicon oxide interlayer, a thin-film lithium niobate layer, a silicon oxide coating layer, and an electrode layer, wherein:

[0007] The silicon oxide interlayer is arranged on the upper surface of the substrate layer;

[0008] A thin film lithium niobate layer is disposed on the upper surface of the silicon oxide interlayer;

[0009] The silicon oxide coating layer is arranged on the upper surface of the thin film lithium niobate layer;

[0010] The electrode layer includes a signal electrode, a first ground electrode, a second ground electrode, and a plurality of periodically staggered L-shaped interdigitated slow-wave electrode structures; the signal electrode, the first ground electrode, the second ground electrode, and the plurality of periodically staggered L-shaped interdigitated slow-wave electrode structures are all arranged on the upper surface of the silicon oxide coating layer;

[0011] For any L-shaped interdigitated slow-wave electrode structure, the L-shaped interdigitated slow-wave electrode structure includes a first L-shaped electrode extending from the first ground electrode, a second L-shaped electrode extending from the second ground electrode, a third L-shaped electrode extending from the signal electrode along the first direction, and a fourth L-shaped electrode extending from the signal electrode along the second direction;

[0012] The first L-shaped electrode and the third L-shaped electrode are arranged crosswise, and the second L-shaped electrode and the fourth L-shaped electrode are arranged crosswise.

[0013] The present invention provides a thin-film lithium niobate electro-optical modulator that addresses the challenge of phase velocity matching between lightwaves and microwaves in thin-film lithium niobate modulators. By providing a cross-arranged L-shaped electrode between a ground electrode and a signal electrode, a plurality of periodically staggered L-shaped interdigitated slow-wave electrode structures are formed. The interdigitated structure strengthens capacitive coupling between the electrodes and enhances the concentration of the electric field in the high-dielectric dielectric. This interdigitated capacitance is added to the modulator to reduce the electrical velocity and increase the electrical phase index, achieving electro-optical velocity matching in the electro-optical modulator. While maintaining low metal absorption loss, the microwave signal refractive index is increased, achieving velocity matching between lightwaves and microwaves and improving the electro-optical bandwidth of the electro-optical modulator. This solves the velocity mismatch problem caused by low-loss substrates and overcomes the technical difficulty of the prior art in limiting the performance trade-off between half-wave voltage and bandwidth.

[0014] Furthermore, the thin film lithium niobate layer includes a waveguide region and a non-waveguide region; wherein: the waveguide region is configured as a ridge-type optical waveguide structure; and the silicon oxide cladding layer is coated on the upper surface of the waveguide region and the non-waveguide region.

[0015] In the above scheme, the optical signal is transmitted by forming a ridge-type optical waveguide structure on the thin-film lithium niobate layer, and a silicon oxide cladding structure is covered thereon to enhance the light field confinement and reduce the transmission loss; and by designing the size of the ridge structure (ridge width, ridge height) and the thickness of the silicon oxide cladding layer, the mode characteristics of the waveguide can be precisely controlled, the electro-optical performance can be improved, and the functionality of the device can be enhanced. The rigidity of silicon oxide can also enhance the mechanical strength of the thin-film lithium niobate, reduce the waveguide deformation caused by stress, and improve the long-term working reliability of the device.

[0016] Furthermore, the substrate layer adopts a quartz substrate or a fused quartz substrate.

[0017] In the above scheme, by adopting a quartz substrate or a fused quartz substrate to design a thin-film lithium niobate electro-optic modulator, the extremely low dielectric constant and low microwave loss characteristics of the quartz material are fully utilized, so that the electro-optic modulator has the ability to more fully adjust the microwave refractive index, achieves efficient matching of microwave speed and light wave speed, and significantly suppresses radio frequency energy dissipation; at the same time, due to the excellent thermomechanical stability and mature wafer-level processing compatibility of the quartz substrate, it is highly adaptable to large-scale manufacturing needs, which is conducive to the large-scale preparation of the electro-optic modulator provided by the present invention; and overcomes the technical problem in the structural design of traditional silicon-based thin-film lithium niobate electro-optic modulators that the inherent high dielectric constant and loss tangent characteristics of the silicon substrate seriously limit the further optimization space of microwave performance.

[0018] Furthermore, it also includes a buried silicon oxide layer and a top electrode layer, wherein: the buried silicon oxide layer covers the upper surface of the electrode layer; the top electrode layer is arranged on the upper surface of the buried silicon oxide layer; and the top electrode layer is electrically connected to the electrode layer.

[0019] In the above scheme, by adding a buried silicon oxide layer and a top electrode layer, the microwave field distribution is optimized, the energy is concentrated in the high dielectric constant silicon oxide, the adverse effects of the negative dielectric constant of the metal are suppressed, and the electromagnetic wave propagation constant is increased, so as to achieve an increase in the effective dielectric constant of the composite structure, thereby further improving the microwave refractive index.

[0020] Furthermore, for any L-shaped interdigital slow-wave electrode structure, the L-shaped interdigital slow-wave electrode structure further includes a first indium tin oxide electrode, a second indium tin oxide electrode, a third indium tin oxide electrode and a fourth indium tin oxide electrode, wherein:

[0021] The first L-shaped electrode includes a first transverse electrode portion and a first longitudinal electrode portion that are fixedly connected; a first longitudinal notch is provided at the bottom of the first transverse electrode portion near one side of the first longitudinal electrode portion; a first transverse notch connected to the first longitudinal notch is provided at the bottom of the first longitudinal electrode portion; a first indium tin oxide electrode is provided in the first longitudinal notch and in a first filling region extending from the first longitudinal notch along a first direction to the first transverse notch;

[0022] The second L-shaped electrode includes a second transverse electrode portion and a second longitudinal electrode portion fixedly connected thereto; a second notch is provided at the bottom of the second transverse electrode portion near one side of the second longitudinal electrode portion; a second notch is provided at the bottom of the second longitudinal electrode portion and connected to the second notch; a second indium tin oxide electrode is provided at the second longitudinal notch and at a second filling region extending from the second longitudinal notch along a second direction to the second transverse notch;

[0023] The third L-shaped electrode includes a third transverse electrode portion and a third longitudinal electrode portion that are fixedly connected; a third longitudinal notch is provided at the bottom of the third transverse electrode portion near one side of the third longitudinal electrode portion; a third transverse notch is provided at the bottom of the third longitudinal electrode portion that is connected to the third longitudinal notch; a third indium tin oxide electrode is provided in the third longitudinal notch and in a third filling region extending from the third longitudinal notch along the second direction to the third transverse notch;

[0024] The fourth L-shaped electrode includes a fourth transverse electrode portion and a fourth longitudinal electrode portion that are fixedly connected; a fourth longitudinal notch is provided at the bottom of the fourth transverse electrode portion near one side of the fourth longitudinal electrode portion; a fourth transverse notch connected to the fourth longitudinal notch is provided at the bottom of the fourth longitudinal electrode portion; a fourth indium tin oxide electrode is provided in the fourth longitudinal notch and in a fourth filling area where the fourth longitudinal notch extends along the first direction to the fourth transverse notch.

[0025] In the above scheme, an indium tin oxide electrode is added to the innovative slow-wave electrode structure of the crossed L-shaped half-wave electrode. The electrode has lower absorption loss, can further shorten the electrode gap, and improve the modulation efficiency of the modulator.

[0026] The present invention provides a thin-film lithium niobate electro-optical modulator with an innovative slow-wave electrode structure. Unlike traditional slow-wave electrodes that use a T-shaped structure to add a flat capacitor to the modulator to reduce the electrical velocity and increase the electrical phase index, the present invention uses a crossed L-shaped half-wave electrode to add an interdigital capacitor to the modulator to reduce the electrical velocity and increase the electrical phase index, thereby achieving electro-optical velocity matching of the modulator. The quartz substrate material used has the ability to more fully adjust the microwave refractive index compared to traditional silicon-based solutions, thereby achieving efficient matching of microwave velocity and light wave velocity. A new slow-wave electrode electro-optical modulator is designed, which has a higher microwave refractive index, a characteristic impedance closer to 50 Ohm, and slightly higher transmission loss than traditional T-shaped slow-wave electrodes. In addition, a silicon oxide layer is added on top of the electrode layer and the thin-film lithium niobate layer to reduce metal absorption loss, thereby meeting the conditions required for high-speed operation of the modulator.

[0027] The present invention also provides a method for preparing a thin-film lithium niobate electro-optical modulator, which is used to prepare the above-mentioned thin-film lithium niobate electro-optical modulator, comprising:

[0028] Determining a substrate layer, and forming a silicon oxide interlayer on the upper surface of the substrate layer;

[0029] forming a thin film lithium niobate layer on the upper surface of the silicon oxide interlayer;

[0030] forming a silicon oxide coating layer on the upper surface of the thin film lithium niobate layer;

[0031] Spin coating a first photoresist layer on the upper surface of the silicon oxide coating layer;

[0032] An L-shaped interdigital electrode pattern is exposed and defined in the first photoresist layer, and a periodically staggered L-shaped interdigital slow-wave electrode structure, a signal electrode, a first ground electrode and a second ground electrode are formed on the upper surface of the silicon oxide coating layer based on the L-shaped interdigital electrode pattern.

[0033] The present invention provides a method for preparing a thin-film lithium niobate electro-optic modulator. By forming a periodically staggered L-shaped interdigitated slow-wave electrode structure on the upper surface of a silicon oxide coating layer, interdigitated capacitance is added to the electro-optic modulator to reduce electrical velocity and improve the electrical phase index. A new slow-wave electrode structure is constructed to achieve electro-optical velocity matching of the prepared electro-optical modulator, increase the microwave signal refractive index while maintaining low metal absorption loss, and enhance the electro-optical bandwidth of the modulator.

[0034] Furthermore, a thin-film lithium niobate layer is formed on the upper surface of the silicon oxide interlayer, including: the thin-film lithium niobate layer includes a lithium niobate wafer and a ridge-type optical waveguide structure; a lithium niobate wafer is formed on the upper surface of the silicon oxide interlayer; a waveguide area window and a non-waveguide area window are defined on the upper surface of the lithium niobate wafer; a second photoresist layer is spin-coated on the non-waveguide area window; a ridge waveguide pattern is defined in the second photoresist layer by exposure; a ridge-type optical waveguide structure is formed based on the second photoresist layer and the ridge waveguide pattern, and the second photoresist layer is removed.

[0035] In the above scheme, a ridge-type optical waveguide structure is formed on the thin-film lithium niobate layer to transmit optical signals, and a silicon oxide cladding structure is covered thereon to enhance the light field confinement and reduce the transmission loss; and by designing the size of the ridge structure (ridge width, ridge height) and the thickness of the silicon oxide cladding layer, the mode characteristics of the waveguide can be precisely controlled, the electro-optical performance can be improved, and the functionality of the device can be enhanced. The rigidity of silicon oxide can also enhance the mechanical strength of the thin-film lithium niobate, reduce the waveguide deformation caused by stress, and improve the long-term working reliability of the device.

[0036] Furthermore, the method further includes: forming a buried silicon oxide layer covering the upper surface of the electrode layer; forming a top electrode layer on the upper surface of the buried silicon oxide layer; and electrically connecting the top electrode layer to the electrode layer.

[0037] Furthermore, a via structure is provided in the buried silicon oxide layer, and the top electrode layer is electrically connected to the electrode layer through the via structure.

[0038] In the above scheme, by adding a buried silicon oxide layer and a top electrode layer on the upper surface of the electrode layer, the microwave field distribution is optimized, the energy is concentrated in the high dielectric constant silicon oxide, the adverse effects of the negative dielectric constant of the metal are suppressed, and the electromagnetic wave propagation constant is increased, so as to achieve an increase in the effective dielectric constant of the composite structure, thereby further improving the microwave refractive index.

[0039] Furthermore, it also includes: for any L-shaped electrode included in any L-shaped interdigitated slow-wave electrode structure: the L-shaped electrode includes a transverse electrode portion and a longitudinal electrode portion; a longitudinal notch is formed at the bottom of the transverse electrode portion close to one side of the longitudinal electrode portion; a transverse notch connected to the longitudinal notch is formed at the bottom of the longitudinal electrode portion; an indium tin oxide electrode is formed in the longitudinal notch and in the filling area where the longitudinal notch extends laterally to the transverse notch.

[0040] In the above scheme, an innovative slow-wave electrode structure is created based on the crossed L-shaped half-wave electrodes. The capacitive coupling between the electrodes is strengthened through the interdigital structure, and the concentration of the electric field in the high-dielectric dielectric is enhanced. The interdigital capacitance is added to the modulator to reduce the electric speed and increase the electric phase index, thereby achieving electro-optical speed matching of the modulator.

[0041] The present invention provides a method for preparing a thin-film lithium niobate electro-optical modulator. Unlike the traditional preparation method of slow-wave electrodes in a T-shaped structure that adds a flat plate capacitor to the modulator to reduce the electrical velocity and increase the electrical phase index, the method is based on the formation of crossed L-shaped half-wave electrodes, adding interdigital capacitors to the modulator to reduce the electrical velocity and increase the electrical phase index, thereby achieving electro-optical speed matching of the modulator. A new slow-wave electrode electro-optical modulator is prepared, which has a higher microwave refractive index, a characteristic impedance closer to 50 Ohm, and slightly higher transmission loss than the traditional T-shaped slow-wave electrode. In addition, a coating silicon oxide layer is added above the electrode layer and the thin-film lithium niobate layer to reduce metal absorption loss, thereby meeting the conditions required for high-speed operation of the modulator. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the implementation. Obviously, the drawings described below are only some implementation methods of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0043] Figure 1 3D structure diagram of a thin-film lithium niobate electro-optic modulator provided in this embodiment;

[0044] Figure 2 is a schematic cross-sectional structural diagram of a thin-film lithium niobate electro-optic modulator provided in this embodiment;

[0045] Figure 3 This is a schematic diagram of the cross-sectional structure of a lithium niobate electro-optical modulator with an added buried layer thin film provided in this embodiment;

[0046] Figure 4 This is a schematic diagram of the L-shaped electrode structure of a thin-film lithium niobate electro-optical modulator provided in this embodiment.

[0047] Figure 5 Schematic diagram of structural parameters of a thin-film lithium niobate electro-optic modulator provided in this embodiment;

[0048] Figure 6 Schematic diagram of a thin-film lithium niobate electro-optic modulator with an indium tin oxide electrode provided in this embodiment;

[0049] Figure 7 This is a schematic flow chart of a method for preparing a thin-film lithium niobate electro-optic modulator provided in this embodiment;

[0050] Figure 8 Schematic diagram comparing microwave refractive indices of a conventional T-type electrode modulator and an interdigitated capacitor slow-wave electrode provided in this embodiment;

[0051] Figure 91 is a schematic diagram comparing the characteristic impedances of a conventional T-type electrode modulator and an interdigitated capacitor type slow-wave electrode provided in this embodiment;

[0052] Figure 10 1 is a schematic diagram comparing transmission losses of a conventional T-type electrode modulator and an interdigitated capacitor type slow-wave electrode provided in this embodiment;

[0053] Figure 11 This is a schematic diagram of simulation results of a multi-length interdigitated capacitive slow-wave electrode modulator provided by this embodiment;

[0054] In the figure: 1. Substrate layer; 2. Silicon oxide interlayer; 3. Thin film lithium niobate layer; 4. Silicon oxide coating layer; 5. Electrode layer; 6. Buried silicon oxide layer; 7. Top electrode layer; 8. Indium tin oxide electrode; 01. First L-shaped electrode; 02. Second L-shaped electrode; 03. Third L-shaped electrode; 04. Fourth L-shaped electrode; 10. First signal longitudinal electrode; 11. First signal transverse electrode; 20. First ground longitudinal electrode; 21. First ground transverse electrode; 41. Ridge-type optical waveguide structure; 50. Signal electrode; 51. First ground electrode; 52. Second ground electrode; 71. First photoresist layer; 72. Second photoresist layer. DETAILED DESCRIPTION

[0055] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions in this application will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of this application.

[0056] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" and any variations thereof in the specification and claims of this application and the above-mentioned figure descriptions are intended to cover non-exclusive inclusions.

[0057] In the description of the embodiments of this application, the technical terms "first" and "second" are used only to distinguish different objects and should not be understood to indicate or imply relative importance or implicitly specify the quantity, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, the meaning of "plurality" is more than two, unless otherwise clearly and specifically defined.

[0058] References herein to "embodiments" mean that a particular feature, structure, or characteristic described in connection with the embodiments may be included in at least one embodiment of the present application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor does it constitute an independent or alternative embodiment that is mutually exclusive of other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0059] In the description of the embodiments of this application, the term "and / or" is simply a description of the association relationship between associated objects, indicating that three relationships can exist. For example, A and / or B can represent the following three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally indicates that the associated objects are in an "or" relationship.

[0060] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0061] In the description of the embodiments of the present application, unless otherwise expressly specified or limited, technical terms such as "installed," "connected," "connected," and "fixed" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integration; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; internal connections between two components or interactions between two components. Those skilled in the art can understand the specific meanings of the above terms in the embodiments of the present application based on specific circumstances.

[0062] Example 1:

[0063] This embodiment provides a thin-film lithium niobate electro-optic modulator, comprising a substrate layer 1, a silicon oxide interlayer 2, a thin-film lithium niobate layer 3, a silicon oxide coating layer 4, and an electrode layer 5, wherein:

[0064] The silicon oxide interlayer 2 is arranged on the upper surface of the substrate layer 1;

[0065] The thin film lithium niobate layer 3 is arranged on the upper surface of the silicon oxide interlayer 2;

[0066] The silicon oxide coating layer 4 is provided on the upper surface of the thin film lithium niobate layer 3;

[0067] The electrode layer 5 includes a signal electrode 50, a first ground electrode 51, a second ground electrode 52, and a plurality of periodically staggered L-shaped interdigitated slow-wave electrode structures; the signal electrode 50, the first ground electrode 51, the second ground electrode 52, and the plurality of periodically staggered L-shaped interdigitated slow-wave electrode structures are all disposed on the upper surface of the silicon oxide coating layer 4;

[0068] For any L-shaped interdigital slow-wave electrode structure, the L-shaped interdigital slow-wave electrode structure includes a first L-shaped electrode 01 extending from the first ground electrode 51, a second L-shaped electrode 02 extending from the second ground electrode 52, a third L-shaped electrode 03 extending from the signal electrode 50 along the first direction, and a fourth L-shaped electrode 04 extending from the signal electrode 50 along the second direction;

[0069] The first L-shaped electrode 01 and the third L-shaped electrode 03 are arranged crosswise, and the second L-shaped electrode 02 and the fourth L-shaped electrode 04 are arranged crosswise.

[0070] A thin-film lithium niobate electro-optical modulator provided in this embodiment focuses on the challenge of phase velocity matching between light waves and microwaves in a thin-film lithium niobate modulator. By providing a cross-arranged L-shaped electrode between the ground electrode and the signal electrode 50 to form a plurality of periodically staggered L-shaped interdigitated slow-wave electrode structures, and forming an electrode layer 5 with the signal electrode 50, the first ground electrode 51, and the second ground electrode 52, an interdigital capacitance is added to the modulator to reduce the electrical velocity and increase the electrical phase index, thereby achieving electro-optical velocity matching of the electro-optical modulator. While maintaining a low metal absorption loss, the refractive index of the microwave signal is increased, achieving velocity matching between light waves and microwaves, and realizing an improvement in the electro-optical bandwidth of the electro-optical modulator.

[0071] Optionally, the thin film lithium niobate layer 3 includes a waveguide region and a non-waveguide region; wherein: the waveguide region is configured as a ridge-type optical waveguide structure 41; and the silicon oxide cladding layer 4 is coated on the upper surface of the waveguide region and the non-waveguide region.

[0072] In the specific implementation process, the thin-film lithium niobate layer 3 in this embodiment adopts X-cut thin-film lithium niobate.

[0073] In the specific implementation process, the three-dimensional structure of the thin film lithium niobate electro-optic modulator provided in this embodiment is as follows: Figure 1 As shown, its cross-sectional view is Figure 2As shown, the structure, from bottom to top, includes a substrate layer 1 and an upper silicon oxide interlayer 2. A thin-film lithium niobate layer 3 is located above the silicon oxide interlayer 2, forming a ridge optical waveguide structure 41 to transmit optical signals. A silicon oxide cladding layer 4 is formed over the ridge optical waveguide structure 41 and the thin-film lithium niobate layer 3. An electrode layer 5, formed by a gold traveling wave electrode in a ground-signal-ground (GSG) structure and several periodically staggered L-shaped interdigitated slow-wave electrode structures, transmits high-speed electrical signals. The electrode layer, located at the top layer of the device, transmits high-speed electrical signals, enabling electrical signal transmission. The ridge optical waveguide structure 41 utilizes a lithium niobate ridge optical waveguide structure. Furthermore, a silicon oxide cladding structure introduced between the ridge optical waveguide structure 41 and the metal electrode effectively reduces metal absorption losses in the optical waveguide mode. In specific applications, the L-shaped interdigitated capacitor slow-wave electrode extending from the ground electrode and the signal electrode along the first direction or the second direction is extended from the ground electrode and the signal electrode along the direction of the ridge-type optical waveguide structure 41. The L-shaped interdigitated capacitor slow-wave electrode spans directly above the lithium niobate ridge waveguide and forms a periodic staggered arrangement with another pair of adjacent L-shaped electrodes.

[0074] Optionally, the substrate layer 1 is a quartz substrate or a fused quartz substrate.

[0075] In the specific implementation process, by using a quartz substrate or a fused quartz substrate to design a thin-film lithium niobate electro-optical modulator, the extremely low dielectric constant and low microwave loss characteristics of the quartz material are fully utilized, so that the electro-optical modulator has the ability to more fully adjust the microwave refractive index, achieve efficient matching of microwave speed and light wave speed, and significantly suppress RF energy dissipation; at the same time, due to the excellent thermomechanical stability and mature wafer-level processing compatibility of the quartz substrate, it is highly adaptable to large-scale manufacturing needs, which is conducive to the large-scale preparation of the electro-optical modulator provided by this embodiment; it overcomes the technical problem that in the traditional silicon-based thin-film lithium niobate electro-optical modulator structure design, the inherent high dielectric constant and loss tangent characteristics of the silicon substrate seriously limit the further optimization space of microwave performance.

[0076] Optionally, it also includes a buried silicon oxide layer 6 and a top electrode layer 7, wherein: the buried silicon oxide layer 6 covers the upper surface of the electrode layer 5; the top electrode layer 7 is arranged on the upper surface of the buried silicon oxide layer 6; and the top electrode layer 7 is electrically connected to the electrode layer 5.

[0077] In the specific implementation process, the cross-sectional structure of the lithium niobate electro-optical modulator with an added buried layer thin film provided in this embodiment is as follows: Figure 3As shown, its structure from bottom to top includes a substrate layer 1 and an upper silicon oxide interlayer 2; a thin film lithium niobate layer 3 is above the silicon oxide interlayer 2, and a ridge-type optical waveguide structure 41 is formed on the thin film lithium niobate layer 3 to transmit optical signals; the ridge-type optical waveguide structure 41 and the thin film lithium niobate layer 3 are covered with silicon oxide to form a silicon oxide coating layer 4; the electrode layer 5 formed based on the bottom ground-signal-ground gold traveling wave electrode transmits high-speed electrical signals. In order to realize the transmission of electrical signals, a buried silicon oxide layer 6 can be covered on the electrode layer 5 and a top gold electrode 7 can be added on the buried silicon oxide layer 6. The two layers of gold electrodes are electrically connected through vias.

[0078] Optionally, for any L-shaped interdigital slow-wave electrode structure, the L-shaped interdigital slow-wave electrode structure further includes a first indium tin oxide electrode, a second indium tin oxide electrode, a third indium tin oxide electrode, and a fourth indium tin oxide electrode, wherein:

[0079] The first L-shaped electrode 01 includes a first transverse electrode portion and a first longitudinal electrode portion that are fixedly connected; a first longitudinal notch is provided at the bottom of the first transverse electrode portion near one side of the first longitudinal electrode portion; a first transverse notch connected to the first longitudinal notch is provided at the bottom of the first longitudinal electrode portion; a first indium tin oxide electrode is provided in the first longitudinal notch and in a first filling region extending from the first longitudinal notch along a first direction to the first transverse notch;

[0080] The second L-shaped electrode 02 includes a second transverse electrode portion and a second longitudinal electrode portion fixedly connected thereto; a second notch is provided at the bottom of the second transverse electrode portion near one side of the second longitudinal electrode portion; a second notch is provided at the bottom of the second longitudinal electrode portion, connected to the second notch; a second indium tin oxide electrode is provided at the second longitudinal notch and at a second filling region extending from the second longitudinal notch along a second direction to the second transverse notch;

[0081] The third L-shaped electrode 03 includes a third transverse electrode portion and a third longitudinal electrode portion that are fixedly connected; a third longitudinal notch is provided at the bottom of the third transverse electrode portion near one side of the third longitudinal electrode portion; a third transverse notch is provided at the bottom of the third longitudinal electrode portion that is connected to the third longitudinal notch; a third indium tin oxide electrode is provided in the third longitudinal notch and in a third filling region extending from the third longitudinal notch along the second direction to the third transverse notch;

[0082] The fourth L-shaped electrode 04 includes a fourth transverse electrode portion and a fourth longitudinal electrode portion that are fixedly connected; a fourth longitudinal notch is provided at the bottom of the fourth transverse electrode portion near one side of the fourth longitudinal electrode portion; a fourth transverse notch connected to the fourth longitudinal notch is provided at the bottom of the fourth longitudinal electrode portion; a fourth indium tin oxide electrode is provided in the fourth longitudinal notch and in a fourth filling area where the fourth longitudinal notch extends along the first direction to the fourth transverse notch.

[0083] In the specific implementation process, this embodiment preferably uses gold as the material of the metal electrode. The top view of the thin film lithium niobate electro-optical modulator provided in this embodiment is as follows Figure 4 As shown, the electrode layer utilizes a GSG structure for conducting wave electrodes, including a signal electrode 50, a first ground electrode 51, and a second ground electrode 52, as well as L-shaped interdigitated capacitor slow-wave electrodes extending from the ground and signal electrodes along the first or second direction. The L-shaped interdigitated capacitor slow-wave electrodes span directly above the lithium niobate ridge waveguide and form a periodic staggered arrangement with another adjacent pair of L-shaped electrodes, namely, a staggered arrangement of a first L-shaped electrode 01, a second L-shaped electrode 02, a third L-shaped electrode 03, and a fourth L-shaped electrode 04. The L-shaped electrode extending from the ground electrode includes longitudinal and transverse branches, while the L-shaped electrode extending from the signal electrode also includes corresponding longitudinal and transverse branches. The L-shaped electrode extending from the signal electrode includes a first longitudinal signal electrode 10 and a first transverse signal electrode 11, and the L-shaped electrode extending from the first ground electrode includes a first longitudinal ground electrode 20 and a first transverse ground electrode 21. The L-shaped interdigitated capacitor slow-wave electrode structure comprises a periodic top-down structure of two L-shaped metal electrodes, forming a periodic interdigitated capacitor along the direction of high-speed electrical signal transmission. The periodic high-density capacitor loading effectively increases the equivalent capacitance between the electrodes, significantly reduces the phase velocity of the microwave, and achieves the expected slow-wave effect. Compared with the traditional T-type flat-plate capacitor slow-wave electrode, the interdigitated capacitor structure adopted in this embodiment can provide a significantly higher capacitance value per unit area. Therefore, the microwave effective refractive index of this structure is greatly improved, making it easier to achieve accurate phase velocity matching with the refractive index of the light wave of the optical waveguide mode. The tiny gap between the L-shaped electrodes and their geometric configuration across the waveguide ensure efficient and sufficient spatial overlap between the microwave excitation electric field and the optical waveguide light field, thereby greatly improving the electro-optical modulation efficiency.

[0084] In the specific implementation process, see Figure 5 The top view structural parameters of a thin film lithium niobate electro-optic modulator with a novel slow-wave electrode provided in this embodiment are shown as follows: Figure 5 (a) shows the dimensions of the interdigitated capacitive slow-wave electrode modulator as follows: the length of the first transverse electrode of the L-shaped electrode is d = 90 μm, the width is s = 2 μm, the length of the first longitudinal electrode is p = 3 μm, the width is t = 2 μm, the gap between the same pair of crossed L-shaped electrodes is g = 6 μm, the spacing between two pairs of crossed L-shaped electrodes is c = 5 μm, and the width of the signal electrode is W_signal = 88 μm. The schematic diagram of the ridge waveguide cross-section structural parameters of the thin-film lithium niobate electro-optical modulator of the novel slow-wave electrode provided in this embodiment is shown in FIG. Figure 5As shown in (b), the lithium niobate ridge waveguide has a height of t_LNrid = 350nm, an upper layer width of w1 = 2μm, and a tilt angle of θ = 60°. The thin-film lithium niobate electro-optic modulator consists, from bottom to top, of a quartz substrate with a thickness of t_quartz = 300μm, a silicon oxide interlayer with a thickness of t_SiO2bot = 2μm, a thin-film lithium niobate layer with a thickness of t_LN = 600nm, a silicon oxide cladding layer with a thickness of t_SiO2clad = 1μm, and an electrode layer with a thickness of t_signal = 800nm.

[0085] In the specific implementation process, an indium tin oxide (ITO) electrode is added to the L-shaped electrode. The ITO electrodes 8 are distributed on both sides of the L-shaped electrode near the lithium niobate ridge waveguide. The ITO electrodes 8 replace part of the L-shaped electrode and need to extend a certain width toward the lithium niobate ridge waveguide compared to the L-shaped electrode. The electrodes made of ITO material have lower absorption loss, which can further shorten the electrode gap and improve the modulation efficiency of the modulator. This embodiment provides a thin-film lithium niobate electro-optical modulator with an indium tin oxide electrode. Figure 6 As shown, Figure 6 (a) is a three-dimensional diagram of an interdigitated capacitive slow-wave electrode modulator with indium tin oxide electrodes added. Figure 6 (b) is a cross-sectional view of an interdigitated capacitive slow-wave electrode modulator with indium tin oxide electrodes added.

[0086] This embodiment provides a thin-film lithium niobate electro-optical modulator with an innovative slow-wave electrode structure. Unlike the traditional slow-wave electrode that uses a T-type structure to add a flat capacitor to the modulator to reduce the electrical velocity and increase the electrical phase index, this embodiment uses a cross-L-type half-wave electrode to add an interdigital capacitor to the modulator to reduce the electrical velocity and increase the electrical phase index, thereby achieving electro-optical velocity matching of the modulator. The quartz substrate material used has the ability to more fully adjust the microwave refractive index compared to traditional silicon-based solutions, thereby achieving efficient matching of microwave velocity and light wave velocity. A new slow-wave electrode electro-optical modulator is designed, which has a higher microwave refractive index, a characteristic impedance closer to 50 Ohm, and slightly higher transmission loss than the traditional T-type slow-wave electrode. In addition, a silicon oxide layer is added on top of the electrode layer 5 and the thin-film lithium niobate layer 3 to reduce metal absorption loss, thereby meeting the conditions required for high-speed operation of the modulator.

[0087] This example focuses on the challenges of phase velocity matching between light waves and microwaves in thin-film lithium niobate modulators. A novel slow-wave electrode structure design is proposed for thin-film lithium niobate modulators based on quartz substrates. This design aims to increase the refractive index of microwave signals while maintaining low metal absorption losses, thereby achieving speed matching between light waves and microwaves and ultimately increasing the electro-optical bandwidth of the modulator.

[0088] Example 2:

[0089] This embodiment further provides a method for preparing a thin-film lithium niobate electro-optic modulator, which is used to prepare the above-mentioned thin-film lithium niobate electro-optic modulator, comprising:

[0090] Determine a substrate layer 1, and form a silicon oxide interlayer 2 on the upper surface of the substrate layer 1;

[0091] forming a thin film lithium niobate layer 3 on the upper surface of the silicon oxide interlayer 2;

[0092] forming a silicon oxide coating layer 4 on the upper surface of the thin film lithium niobate layer 3;

[0093] A first photoresist layer is spin-coated on the upper surface of the silicon oxide coating layer 4;

[0094] An L-shaped interdigitated electrode pattern is exposed and defined in the first photoresist layer. Based on the L-shaped interdigitated electrode pattern, a periodically staggered L-shaped interdigitated slow-wave electrode structure, a signal electrode 50 , a first ground electrode 51 and a second ground electrode 52 are formed on the upper surface of the silicon oxide coating layer 4 .

[0095] This embodiment provides a method for preparing a thin-film lithium niobate electro-optical modulator. By forming a periodically staggered L-shaped interdigitated slow-wave electrode structure on the upper surface of the silicon oxide coating layer 4, interdigitated capacitance is added to the electro-optical modulator to reduce the electrical velocity and improve the electrical phase index, thereby constructing a new slow-wave electrode structure to realize the prepared electro-optical modulator, achieve electro-optical velocity matching of the prepared electro-optical modulator, increase the refractive index of the microwave signal while maintaining low metal absorption loss, and improve the electro-optical bandwidth of the modulator.

[0096] Optionally, a thin-film lithium niobate layer 3 is formed on the upper surface of the silicon oxide interlayer 2, including: the thin-film lithium niobate layer 3 includes a lithium niobate wafer and a ridge-type optical waveguide structure; a thin-film lithium niobate wafer is formed on the upper surface of the silicon oxide interlayer 2; a waveguide area window and a non-waveguide area window are defined on the upper surface of the thin-film lithium niobate wafer; a second photoresist layer is spin-coated on the non-waveguide area window of the thin-film lithium niobate wafer; a ridge waveguide pattern is defined in the second photoresist layer by exposure; a ridge-type optical waveguide structure is formed based on the second photoresist layer and the ridge waveguide pattern, and the second photoresist layer is removed.

[0097] During the specific implementation process, a ridge-type optical waveguide structure 41 is formed on the thin-film lithium niobate layer 3 to transmit optical signals, and a silicon oxide cladding structure is covered thereon to enhance the light field confinement and reduce the transmission loss; and by designing the size of the ridge structure (ridge width, ridge height) and the thickness of the silicon oxide cladding layer, the mode characteristics of the waveguide can be precisely controlled, the electro-optical performance can be improved, and the functionality of the device can be enhanced. The rigidity of silicon oxide can also enhance the mechanical strength of the thin-film lithium niobate, reduce the waveguide deformation caused by stress, and improve the long-term working reliability of the device.

[0098] Optionally, the method further includes: forming a buried silicon oxide layer 6 covering the upper surface of the electrode layer 5 ; forming a top electrode layer 7 on the upper surface of the buried silicon oxide layer 6 ; and electrically connecting the top electrode layer 7 to the electrode layer 5 .

[0099] Optionally, a via structure is provided in the buried silicon oxide layer 6 , and the top electrode layer 7 is electrically connected to the electrode layer 5 through the via structure.

[0100] In the specific implementation process, the process of preparing a thin film lithium niobate electro-optical modulator provided in this embodiment is as follows: Figure 7 As shown, where: Figure 7 (a) shows the cleaning process of a lithium niobate wafer on a quartz substrate, wherein the quartz substrate includes a substrate layer 1, a silicon oxide interlayer 2, and a thin film lithium niobate layer 3; Figure 7 (b) shows the formation of a first photoresist layer 71 by spin coating photoresist, followed by electron beam exposure and development to define a lithium niobate ridge waveguide pattern; Figure 7 (c) shows the formation of lithium niobate ridge waveguide 41 by reactive ion etching process; Figure 7 (d) shows that silicon oxide is deposited by chemical vapor deposition, annealed to optimize performance, and chemical mechanical polished to flatten the silicon oxide coating structure, which together with the lithium niobate ridge waveguide 41 forms the silicon oxide coating layer 4; Figure 7 (e) shows a second photoresist layer 72 formed by spin coating photoresist on the regions corresponding to the L-shaped interdigitated slow-wave electrode structures arranged in a staggered manner for a certain period, and performing electron beam exposure to define the electrode pattern, followed by electron beam evaporation to deposit metal 73 on the second photoresist layer 72 and the upper surface of the silicon oxide coating layer; Figure 7 (f) shows that after the metal is deposited, the electrode layer 5 is formed by a lift-off process, and the electro-optic modulator is successfully prepared.

[0101] Optionally, it also includes: for any L-shaped electrode included in any L-shaped interdigitated slow-wave electrode structure: the L-shaped electrode includes a transverse electrode portion and a longitudinal electrode portion; a longitudinal notch is formed at the bottom of the transverse electrode portion close to the side of the longitudinal electrode portion; a transverse notch connected to the longitudinal notch is formed at the bottom of the longitudinal electrode portion; an indium tin oxide electrode is formed in the longitudinal notch and in the filling area where the longitudinal notch extends laterally to the transverse notch.

[0102] During the specific implementation process, an innovative slow-wave electrode structure is developed based on the crossed L-shaped half-wave electrodes. The capacitive coupling between electrodes is strengthened through the interdigital structure, and the concentration of the electric field in the high-dielectric dielectric is enhanced. The interdigital capacitance is added to the modulator to reduce the electric speed and increase the electric phase index, thereby achieving electro-optical speed matching of the modulator.

[0103] This embodiment provides a method for preparing a thin-film lithium niobate electro-optical modulator. Different from the traditional slow-wave electrode preparation method that uses a T-shaped structure to add a flat plate capacitor to the modulator to reduce the electrical speed and increase the electrical phase index, this method is based on the formation of a cross-L-shaped half-wave electrode, adding an interdigital capacitor to the modulator to reduce the electrical speed and increase the electrical phase index, thereby achieving electro-optical speed matching of the modulator. A new slow-wave electrode electro-optical modulator is prepared, which has a higher microwave refractive index, a characteristic impedance closer to 50 Ohm, and slightly higher transmission loss than the traditional T-shaped slow-wave electrode. In addition, a coating silicon oxide layer is added on top of the electrode layer 5 and the thin-film lithium niobate layer 3 to reduce metal absorption loss, thereby meeting the conditions required for high-speed operation of the modulator.

[0104] Example 3:

[0105] This embodiment also provides a method for verifying the characteristics of a thin-film lithium niobate electro-optical modulator. To verify and compare the high-frequency characteristics of a conventional T-type electrode and the new interdigitated capacitor type slow-wave electrode proposed in this embodiment, a finite element method is used to simulate and compare the high-frequency characteristics of the conventional T-type electrode and the new interdigitated capacitor type slow-wave electrode. The microwave refractive index (n) of the two types of modulators is calculated. eff ), RF transmission loss (Z0, in Ohm) and port impedance (Loss, in dB / cm). The microwave refractive index comparison results of the traditional T-type electrode modulator and the interdigitated capacitor slow-wave electrode are as follows: Figure 8 As shown in the figure, the characteristic impedance comparison between the traditional T-type electrode modulator and the interdigitated capacitor slow-wave electrode is shown in the figure. Figure 9 As shown in the figure, the transmission loss comparison between the traditional T-type electrode modulator and the interdigitated capacitor type slow wave electrode is shown in Figure 10 As shown in the figure, the horizontal axis "Frequency (GHz)" represents frequency. By comparison, it can be seen that, while maintaining the same dimensions, the new interdigitated capacitive slow-wave electrode can achieve a higher microwave refractive index, a characteristic impedance closer to 50 Ohm, and slightly higher transmission loss than the traditional T-type slow-wave electrode. Simulation experiments were conducted to analyze the metal absorption loss of the thin-film lithium niobate electro-optic modulator with the new slow-wave electrode. By simulating the two-dimensional cross-sectional structure of the optical waveguide, it was found that at a wavelength of 1550nm, the optical waveguide mode loss was 0.0088dB / cm. This verifies that the electro-optic modulator with this structure reduces metal absorption loss by adding a silicon oxide coating to the metal electrode layer and the thin-film lithium niobate layer, thus meeting the conditions required for high-speed operation of the modulator.

[0106] Example 4:

[0107] This embodiment also provides a comparative analysis solution for interdigital capacitive slow-wave electrode modulators of various lengths, and achieves a better port impedance matching degree by changing the size parameters of the interdigital capacitive slow-wave electrode modulator. Figure 11 As shown, Figure 11 (a) shows the S21 comparison results of the interdigital capacitive slow-wave electrode modulator with lengths of 0.5mm, 1mm, and 2mm respectively. S21 represents the insertion loss from the input port to the output port in dB. Figure 11 (a) It can be seen that the electrode insertion loss will gradually increase with the increase of electrode length. The S11 comparison results of the interdigital capacitive slow-wave electrode modulator with lengths of 0.5mm, 1mm, and 2mm are shown in the figure. Figure 11 As shown in (b), S11 is the return loss of the device, which can be used to obtain the impedance matching quality of the input port. The lower the S11 value, the better the port impedance matching.

[0108] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A thin film lithium niobate electro-optic modulator, characterized in that: It includes a substrate layer, a silicon oxide interlayer, a thin film lithium niobate layer, a silicon oxide coating layer and an electrode layer, wherein: The silicon oxide interlayer is arranged on the upper surface of the substrate layer; The thin film lithium niobate layer is arranged on the upper surface of the silicon oxide interlayer; The silicon oxide coating layer is provided on the upper surface of the thin film lithium niobate layer; The electrode layer includes a signal electrode, a first ground electrode, a second ground electrode, and a plurality of periodically staggered L-shaped interdigital slow-wave electrode structures; the signal electrode, the first ground electrode, the second ground electrode, and the plurality of periodically staggered L-shaped interdigital slow-wave electrode structures are all arranged on the upper surface of the silicon oxide coating layer; For any L-shaped interdigitated slow-wave electrode structure, the L-shaped interdigitated slow-wave electrode structure includes a first L-shaped electrode extending from the first ground electrode, a second L-shaped electrode extending from the second ground electrode, a third L-shaped electrode extending from the signal electrode along the first direction, and a fourth L-shaped electrode extending from the signal electrode along the second direction; The first L-shaped electrode and the third L-shaped electrode are arranged crosswise, and the second L-shaped electrode and the fourth L-shaped electrode are arranged crosswise.

2. The thin-film lithium niobate electro-optic modulator according to claim 1, wherein: The thin film lithium niobate layer includes a waveguide region and a non-waveguide region; wherein: The waveguide region is configured as a ridge-type optical waveguide structure; The silicon oxide cladding layer covers the upper surfaces of the waveguide area and the non-waveguide area.

3. The thin-film lithium niobate electro-optic modulator according to claim 1, wherein: The substrate layer is a quartz substrate or a fused quartz substrate.

4. The thin film lithium niobate electro-optic modulator according to claim 1, wherein: Also included is a buried silicon oxide layer and a top electrode layer, wherein: The buried silicon oxide layer covers the upper surface of the electrode layer; The top electrode layer is disposed on the upper surface of the buried silicon oxide layer; The top electrode layer is electrically connected to the electrode layer.

5. The thin film lithium niobate electro-optic modulator according to claim 1, wherein: For any L-shaped interdigital slow-wave electrode structure, the L-shaped interdigital slow-wave electrode structure further includes a first indium tin oxide electrode, a second indium tin oxide electrode, a third indium tin oxide electrode and a fourth indium tin oxide electrode, wherein: The first L-shaped electrode includes a first transverse electrode portion and a first longitudinal electrode portion that are fixedly connected; a first longitudinal notch is provided at the bottom of the first transverse electrode portion near one side of the first longitudinal electrode portion; a first transverse notch connected to the first longitudinal notch is provided at the bottom of the first longitudinal electrode portion; the first indium tin oxide electrode is provided in the first longitudinal notch and in a first filling region extending from the first longitudinal notch along a first direction to the first transverse notch; The second L-shaped electrode includes a second transverse electrode portion and a second longitudinal electrode portion that are fixedly connected; a second notch is provided at the bottom of the second transverse electrode portion near one side of the second longitudinal electrode portion; a second notch is provided at the bottom of the second longitudinal electrode portion that is connected to the second notch; the second indium tin oxide electrode is provided in the second longitudinal notch and in a second filling region extending from the second longitudinal notch along a second direction to the second transverse notch; The third L-shaped electrode includes a third transverse electrode portion and a third longitudinal electrode portion that are fixedly connected; a third longitudinal notch is provided at the bottom of the third transverse electrode portion near one side of the third longitudinal electrode portion; a third transverse notch is provided at the bottom of the third longitudinal electrode portion and is connected to the third longitudinal notch; the third indium tin oxide electrode is provided in the third longitudinal notch and in a third filling region extending from the third longitudinal notch along the second direction to the third transverse notch; The fourth L-shaped electrode includes a fourth transverse electrode portion and a fourth longitudinal electrode portion that are fixedly connected; a fourth longitudinal notch is provided at the bottom of the fourth transverse electrode portion close to one side of the fourth longitudinal electrode portion; a fourth transverse notch connected to the fourth longitudinal notch is provided at the bottom of the fourth longitudinal electrode portion; the fourth indium tin oxide electrode is provided in the fourth longitudinal notch and in a fourth filling area where the fourth longitudinal notch extends along the first direction to the fourth transverse notch.

6. A method for preparing a thin film lithium niobate electro-optical modulator, characterized in that: A method for preparing a thin-film lithium niobate electro-optical modulator according to any one of claims 1 to 5, comprising: Determining a substrate layer, and forming a silicon oxide interlayer on the upper surface of the substrate layer; forming a thin film lithium niobate layer on the upper surface of the silicon oxide interlayer; forming a silicon oxide coating layer on the upper surface of the thin film lithium niobate layer; A first photoresist layer is spin-coated on the upper surface of the silicon oxide coating layer; An L-shaped interdigitated electrode pattern is exposed in the first photoresist layer, and based on the L-shaped interdigitated electrode pattern, the periodically staggered L-shaped interdigitated slow-wave electrode structure, the signal electrode, the first ground electrode and the second ground electrode are formed on the upper surface of the silicon oxide coating layer.

7. The method for preparing a thin film lithium niobate electro-optical modulator according to claim 6, wherein: The step of forming a thin film lithium niobate layer on the upper surface of the silicon oxide interlayer comprises: The thin film lithium niobate layer includes a lithium niobate wafer and a ridge-type optical waveguide structure; forming a lithium niobate wafer on the upper surface of the silicon oxide interlayer; Defining a waveguide region window and a non-waveguide region window on the upper surface of the lithium niobate wafer, and spin-coating a second photoresist layer on the non-waveguide region window; exposing a ridge waveguide pattern defined in the second photoresist layer; A ridge type optical waveguide structure is formed based on the second photoresist layer and the ridge waveguide pattern, and the second photoresist layer is removed.

8. The method for preparing a thin film lithium niobate electro-optic modulator according to claim 6, wherein: Also includes: forming a buried silicon oxide layer covering the upper surface of the electrode layer; forming a top electrode layer on the upper surface of the buried silicon oxide layer; The top electrode layer is electrically connected to the electrode layer.

9. The method for preparing a thin film lithium niobate electro-optical modulator according to claim 8, wherein: A via structure is provided in the buried silicon oxide layer, and the top electrode layer is electrically connected to the electrode layer through the via structure.

10. The method for preparing a thin film lithium niobate electro-optical modulator according to claim 6, wherein: Also includes: For any L-shaped electrode included in any L-shaped interdigitated slow-wave electrode structure: The L-shaped electrode includes a transverse electrode portion and a longitudinal electrode portion; A longitudinal notch is formed at the bottom of the transverse electrode portion close to one side of the longitudinal electrode portion; and a transverse notch connected to the longitudinal notch is formed at the bottom of the longitudinal electrode portion; An indium tin oxide electrode is formed in the longitudinal notch and in a filling region where the longitudinal notch extends laterally to the transverse notch.

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