Thin film lithium niobate electro-optical modulator, functional device, regulation and manufacturing method

Abstract

The invention relates to a thin-film lithium niobate electro-optical modulator, a functional device and a regulation and manufacturing method. The thin-film lithium niobate electro-optical modulator comprises a chip main body. The chip main body comprises a substrate layer, a lithium niobate waveguide structure located on the substrate layer, an electro-optical regulation and control electrode and a magnetic regulation and control structure. The lithium niobate waveguide structure comprises an optical signal input section, an electro-optical modulation section and an optical signal output section; the electro-optical regulation and control electrodes are located on the two sides of the electro-optical modulation section Wherein the magnetic regulation and control structures are positioned on two sides of the optical signal input section and are used for generating a modulation magnetic field; and after the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated based on the modulation magnetic field, the polarization state of the optical signal entering the electro-optical modulation section is matched with the polarity of the corresponding lithium niobate material. According to the scheme, the working efficiency and the integration degree of the thin-film lithium niobate modulator are improved, the device performance is stable, and the thin-film lithium niobate modulator is suitable for various application scenes such as optical communication, radar systems, medicine and quantum photonics.

Description

Technical Field

[0001] The present disclosure relates to the technical field of optical communication devices, and particularly to a thin-film lithium niobate electro-optic modulator, a functional device, and a control and manufacturing method thereof. Background Art

[0002] Due to the continuous exponential growth of Internet traffic driven by 5G technology, video streaming, cloud services, data centers, the iterative updates of various applications, and the demand for artificial intelligence (AI) tools, etc., the bandwidth bottleneck of traditional electronic devices has become increasingly prominent. Photonic integrated circuits (PICs) have emerged as a result. The data volume of optical communication networks continues to grow at a high speed, posing higher requirements for the device performance and integration level of optical communication networks. Electro-optic modulators can achieve high-speed modulation of optical signals (from 10 Gbps to several Tbps), becoming the core components of high-speed optical communication networks, and can also be widely applied to radar systems, optical coherence tomography, sensing, and quantum photonics, etc. Currently, electro-optic modulators are classified into three categories according to materials: lithium niobate-based modulators, compound semiconductor modulators, and silicon-based modulators. Since lithium niobate materials have a window for optical fiber communication and stable performance, they are regarded as one of the most promising materials for optoelectronic modulators. The corresponding lithium niobate-based modulators have the characteristics of high modulation rate, low power consumption, low half-wave voltage, and high material stability, and are suitable for fields such as data centers, backbone network communication transmission, microwave photonic links, and inter-satellite communication.

[0003] However, the inventors found in the research and development that the following problems need to be urgently solved in the related technologies of lithium niobate-based electro-optic modulators: polarization control of optical modes in lithium niobate waveguides is one of the key difficulties that must be overcome in thin-film lithium niobate modulators and device integration; most of the existing control technologies perform optical path control by additionally adding an external control component, introducing new materials or structural asymmetry, which easily leads to noise sources and mismatches, and there is a risk of failure and aging of external components, increasing costs; some solutions achieve polarization state control by enhancing the vertical asymmetry of the waveguide structure or using a shallow-etched ridge waveguide structure. This method requires a very high degree of process controllability, and the device qualification rate is low, increasing the cost and risk of chip manufacturing. Summary of the Invention

[0004] In order to solve the above technical problems or at least partially solve the above technical problems, embodiments of the present disclosure provide a thin-film lithium niobate electro-optic modulator, a functional device, and a control and manufacturing method thereof.

[0005] In a first aspect, an embodiment of the present disclosure provides a thin-film lithium niobate electro-optic modulator. The thin-film lithium niobate electro-optic modulator includes: a chip body. The chip body includes: a substrate layer, a lithium niobate waveguide structure, an electro-optic control electrode, and a magnetic control structure located above the substrate layer. The lithium niobate waveguide structure includes: an optical signal input section, an electro-optic modulation section, and an optical signal output section; the electro-optic control electrodes are located on both sides of the electro-optic modulation section. Among them, the magnetic control structure is located on both sides of the optical signal input section and is used to generate a modulation magnetic field; after the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated based on the modulation magnetic field, the polarization state of the optical signal entering the electro-optic modulation section matches the polarity of the corresponding lithium niobate material.

[0006] In some embodiments, the magnetic control structure includes: a target structure layer and a magneto-optic control electrode connected to the target structure layer. Among them, the target structure layer has the following characteristics: it exhibits anisotropy and has the Faraday rotation effect under the action of a magnetic field. The magneto-optic control electrode is used to load an electrical control signal to generate a magnetic field in the target structure layer, and the magnetic field is regulated based on the modulation of the electrical control signal, thereby regulating the polarization state of the optical signal passing through the magnetic field.

[0007] In some embodiments, the target structure layer is a single-layer structure or a multi-layer structure. The magnetic materials or structures used in the target structure layer include one or more of the following: yttrium iron garnet YIG, bismuth-substituted yttrium iron garnet BIG, europium oxide EuO, gadolinium gallium garnet GGG, manganese-zinc ferrite, an ultra-thin ferromagnetic metal multi-layer film structure with a thickness less than 10 nanometers, a magnetic topological insulator, a magnetoelectric composite structure, a two-dimensional magnetic material, a perovskite-type oxide.

[0008] In some embodiments, the target structure layer contains a magneto-optic material, and the rotation angle of the linearly polarized light after passing through the target structure layer is affected by the following factors: the gyromagnetic characteristics of the magneto-optic material, the distance of the optical signal passing through the corresponding material layer of the magneto-optic material, the magnetic field direction, and the magnetic field strength.

[0009] In some embodiments, the substrate layer includes one of the following structures:

[0010] A silicon-on-insulator SOI substrate, including: a silicon substrate and a lower cladding layer located on the silicon substrate; or,

[0011] A first type of lithium niobate-on-insulator LNOI substrate, including: a silicon substrate, a lower cladding layer located on the silicon substrate, and a lithium niobate layer located on the lower cladding layer; or,

[0012] A second type of lithium niobate-on-insulator LNOI substrate, including: a lithium niobate substrate, a lower cladding layer located on the lithium niobate substrate, and a lithium niobate layer located on the lower cladding layer.

[0013] In some embodiments, the above-mentioned lithium niobate waveguide structure is one of the following waveguide structures: strip waveguide structure, ridge waveguide structure or heterogeneous integrated waveguide structure. Among them, the above-mentioned strip waveguide structure is a convex structure compared with the surface of the silica layer or the lithium niobate layer on the top of the base layer, and the two side walls are vertical structures. The above-mentioned ridge waveguide structure is a convex structure compared with the surface of the silica layer or the lithium niobate layer on the top of the base layer, and the two side walls have inclined slopes. The above-mentioned heterogeneous integrated waveguide structure includes: a lithium niobate thin film layer located on the SOI substrate, a heterogeneous layer located on the above-mentioned lithium niobate thin film layer and having a convex structure, the above-mentioned heterogeneous layer and the lithium niobate thin film layer form a heterojunction, and the refractive index of the material corresponding to the above-mentioned heterogeneous layer is equal to or higher than the refractive index of the above-mentioned lithium niobate thin film layer.

[0014] In some embodiments, there is also a target coating layer between the above-mentioned base layer and the above-mentioned magnetic modulation structure. The above-mentioned target coating layer coats the side walls and the top of the above-mentioned lithium niobate waveguide structure. The above-mentioned target coating layer is used as a protective layer for the above-mentioned lithium niobate waveguide structure during the process of fabricating the above-mentioned magnetic modulation structure, and serves as a cladding waveguide outside the above-mentioned lithium niobate waveguide structure in the above-mentioned thin film lithium niobate electro-optic modulator to first couple and transfer the optical signal into the above-mentioned lithium niobate waveguide structure. Among them, the above-mentioned target coating layer is a single-layer structure or a multi-layer structure, and the material of the above-mentioned target coating layer is one or more of the following: silica, silicon nitride, silicon oxynitride, SU-8 polymer, magnesium oxide, tantalum oxide, aluminum oxide, titanium oxide.

[0015] In a second aspect, an embodiment of the present disclosure provides a modulation method for the above-mentioned thin film lithium niobate electro-optic modulator. The above-mentioned modulation method includes: generating a modulation magnetic field based on the control of the magnetic modulation structure; based on the above-mentioned modulation magnetic field, controllably modulating the polarization state of the optical signal transmitted in the above-mentioned optical signal input section, so that the polarization state of the optical signal entering the above-mentioned electro-optic modulation section matches the polarity of the corresponding lithium niobate material; in the above-mentioned electro-optic modulation section, based on the input control of the electro-optic modulation electrode, controllably modulating the refractive index of the above-mentioned lithium niobate waveguide structure and affecting the phase, intensity or polarization state of the passing optical signal to achieve electro-optic modulation.

[0016] Thirdly, embodiments of the present disclosure provide a method for manufacturing a thin-film lithium niobate electro-optic modulator. The above manufacturing method includes: preparing a substrate; fabricating a lithium niobate waveguide structure, an electro-optic control electrode, and a magnetic control structure on the above substrate based on thin-film preparation and patterning processes. Among them, the above lithium niobate waveguide structure includes: an optical signal input section, an electro-optic modulation section, and an optical signal output section; the above electro-optic control electrodes are located on both sides of the above electro-optic modulation section; the above magnetic control structure is located on both sides of the above optical signal input section and is used to generate a modulation magnetic field; after controllably modulating the polarization state of the optical signal transmitted in the above optical signal input section based on the above modulation magnetic field, the polarization state of the optical signal entering the above electro-optic modulation section matches the polarity of the corresponding lithium niobate material.

[0017] In some embodiments, the above substrate includes one of the following structures: a silicon-on-insulator (SOI) substrate, a first type of LNOI substrate including a silicon substrate, a second type of LNOI substrate including a lithium niobate substrate; the first type of LNOI substrate includes: a silicon substrate, a lower cladding layer located on the above silicon substrate, and a lithium niobate layer located on the above lower cladding layer; the second type of LNOI substrate includes: a lithium niobate substrate, a lower cladding layer located on the above lithium niobate substrate, and a lithium niobate layer located on the above lower cladding layer;

[0018] Fabricating a lithium niobate waveguide structure, an electro-optic control electrode, and a magnetic control structure on the above substrate based on thin-film preparation and patterning processes includes:

[0019] For the SOI substrate, fabricating a lithium niobate thin film on the above silicon-on-insulator (SOI) substrate based on ion cutting technology, specifically including: bombarding a lithium niobate (LN) wafer with high-energy ions to form an ion implantation layer at a preset depth; bonding the ion-implanted lithium niobate (LN) wafer to the SOI substrate and performing annealing treatment. During the annealing treatment, the implanted ions expand, causing the bonded structure to detach from the position at the preset depth, and peeling to obtain an SOI substrate with a lithium niobate thin film;

[0020] For the LNOI substrate or the SOI substrate with a lithium niobate thin film, fabricating a patterned lithium niobate waveguide structure based on diamond cutting, chemical mechanical polishing, dry etching, or photolithography processes;

[0021] Based on thin-film preparation processes, forming a target cladding layer structure on the substrate including the patterned lithium niobate waveguide structure; the above target cladding layer structure covers the sidewalls and the top of the above lithium niobate waveguide structure; the above target cladding layer structure serves as a protective layer for the above lithium niobate waveguide structure during the process of fabricating the magnetic control structure; after fabrication, in the above thin-film lithium niobate electro-optic modulator, it serves as a cladding waveguide to first couple and couple the optical signal into the above lithium niobate waveguide structure;

[0022] Based on thin film preparation and lithography processes, a patterned electro-optic modulation electrode is fabricated on the above-mentioned cladding layer structure;

[0023] Based on thin film preparation and lithography processes, a patterned magnetic modulation structure is fabricated on a substrate including a patterned lithium niobate waveguide structure and an electro-optic modulation electrode; wherein, during the process of fabricating the patterned magnetic modulation structure, photoresist is used as the outermost protective layer of the already fabricated patterned lithium niobate waveguide structure and electro-optic modulation electrode, and regional exposure is adopted.

[0024] In a fourth aspect, embodiments of the present disclosure provide a functional device including the above-mentioned thin film lithium niobate electro-optic modulator. The above-mentioned functional device is one or more of the following devices: a coherent optical module for long-distance optical fiber communication; a silicon-based heterogeneous integrated optical chip; an optical wireless communication device for 5G / 6G base station fronthaul; a silicon photonics heterogeneous integrated device; a modulation chip for quantum communication or quantum computing; a chirp modulator in lidar; an intensity modulator in lidar; a tunable laser; a photonic radio frequency front-end device for radar detection and electronic countermeasure; a high-speed swept-source for medical optical coherence tomography; a phase-sensitive modulation module for pipeline, bridge, and building monitoring.

[0025] The above technical solutions provided by the embodiments of the present disclosure have at least some or all of the following advantages:

[0026] In the above-mentioned thin-film lithium niobate electro-optic modulator, the core mechanism for realizing electro-optic modulation is based on the linear electro-optic effect (Pockels effect). By applying an external electric field, the refractive index of the crystal changes, thereby changing the phase, intensity, or polarization state of the light wave. Since the lithium niobate material is a polar anisotropic crystal, the electro-optic coefficients in different directions are different, resulting in different modulation efficiencies for light. In the device structure provided by the embodiments of the present disclosure, by integrating a lithium niobate waveguide structure, an electro-optic control electrode, and a magnetic control structure in the chip body, the magnetic control structure for generating a modulation magnetic field is introduced to both sides of the optical signal input section of the lithium niobate waveguide structure. Utilizing the Faraday rotation effect, when light passes through the magnetic field, the polarization plane parallel to the magnetic field vector direction will rotate. In this way, the polarization state of the optical signal in the optical signal input section can be controllably modulated. After the polarization state of the optical signal transmitted in the above-mentioned optical signal input section is controllably modulated based on the above-mentioned modulation magnetic field, the polarization state of the optical signal entering the above-mentioned electro-optic modulation section matches the polarity of the corresponding lithium niobate material. In this way, the electro-optic modulation efficiency of the thin-film lithium niobate electro-optic modulator can be improved. Moreover, the principle of the magnetic control polarization technology belongs to the intrinsic phenomenon of the electromagnetic field, and the influence of the external mechanical environment on the optical path is small, which can be applied to various application scenarios (such as optical communication, quantum communication and quantum computing, radar systems, optical coherence tomography, etc.), with stable performance and high reliability. The magnetic control structure, the lithium niobate waveguide structure, and the electro-optic control electrode can be packaged and tested synchronously on the same chip, which improves the integration degree of the thin-film lithium niobate electro-optic modulator and reduces the difficulty of optical path calibration or control caused by externally introduced devices. In the future optoelectronic integrated technology system, it has obvious advantages and application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings herein are incorporated into the specification and constitute a part of this specification, showing embodiments consistent with the present disclosure and used together with the specification to explain the principles of the present disclosure.

[0028] To more clearly illustrate the technical solutions in the embodiments of the present disclosure or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or related technologies. Obviously, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without creative efforts.

[0029] Figure 1 Schematically shows a structural block diagram of a chip body in a thin-film lithium niobate electro-optic modulator according to some embodiments of the present disclosure;

[0030] Figure 2A Schematically shows a structural schematic diagram after being cut along the A1-A2 section according to some embodiments of the present disclosure;

[0031] Figure 2BSchematically shows another structural schematic diagram after being cut along the A1-A2 section according to some embodiments of the present disclosure;

[0032] Figure 2C Schematically shows yet another structural schematic diagram after being cut along the A1-A2 section according to some embodiments of the present disclosure;

[0033] Figure 3 Schematically shows a flowchart of a control method for a thin-film lithium niobate electro-optic modulator according to some embodiments of the present disclosure;

[0034] Figures 4A to 4M2 Schematically shows a schematic diagram of the manufacturing process of fabricating a patterned lithium niobate waveguide structure based on a lithography process according to some embodiments of the present disclosure;

[0035] Figure 4A Schematic cross-sectional structure diagram of a substrate prepared according to an embodiment of the present disclosure;

[0036] Figure 4B1 Schematic structural diagram after depositing a hard mask material layer on the substrate from the perspective of being cut along the A1-A2 section according to an embodiment of the present disclosure;

[0037] Figure 4B2 Schematic structural diagram after depositing a hard mask material layer on the substrate from the perspective of being cut along the B1-B2 section according to an embodiment of the present disclosure;

[0038] Figure 4C1 Schematic structural diagram after continuously depositing photoresist on the substrate from the perspective of being cut along the A1-A2 section after depositing a hard mask material layer according to an embodiment of the present disclosure;

[0039] Figure 4C2 Schematic structural diagram after continuously depositing photoresist on the substrate from the perspective of being cut along the B1-B2 section after depositing a hard mask material layer according to an embodiment of the present disclosure;

[0040] Figure 4D1 Schematic structural diagram of obtaining a patterned photoresist by exposure, development, and etching from the perspective of being cut along the A1-A2 section according to an embodiment of the present disclosure;

[0041] Figure 4D2 Schematic structural diagram of obtaining a patterned photoresist by exposure, development, and etching from the perspective of being cut along the B1-B2 section according to an embodiment of the present disclosure;

[0042] Figure 4E1 Schematic structural diagram of obtaining a patterned hard mask after hard mask etching based on the patterned photoresist from the perspective of being cut along the A1-A2 section according to an embodiment of the present disclosure;

[0043] Figure 4E2Schematic structural diagram of a patterned hard mask obtained after hard mask etching based on a patterned photoresist from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0044] Figure 4F1 Schematic structural diagram of a patterned lithium niobate waveguide structure obtained after etching based on a patterned hard mask from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0045] Figure 4F2 Schematic structural diagram of a patterned lithium niobate waveguide structure obtained after etching based on a patterned hard mask from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0046] Figure 4G1 Schematic structural diagram of a target cladding layer formed on a patterned lithium niobate waveguide structure from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0047] Figure 4G2 Schematic structural diagram of a target cladding layer formed on a patterned lithium niobate waveguide structure from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0048] Figure 4H1 Schematic structural diagram of an electro-optic modulation electrode formed based on a lithography process from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0049] Figure 4H2 Schematic structural diagram of an electro-optic modulation electrode formed based on a lithography process from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0050] Figure 4I1 Schematic structural diagram of a photoresist deposited on a chip with a prepared lithium niobate waveguide structure and electro-optic modulation electrode from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0051] Figure 4I2 Schematic structural diagram of a photoresist deposited on a chip with a prepared lithium niobate waveguide structure and electro-optic modulation electrode from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0052] Figure 4J1 Schematic structural diagram of a patterned photoresist obtained after regional exposure of the deposited photoresist from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0053] Figure 4J2 Schematic structural diagram of a patterned photoresist obtained after regional exposure of the deposited photoresist from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0054] Figure 4K1 Schematic diagram of depositing a target structure layer thin film on a wafer with patterned photoresist from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0055] Figure 4K2 Schematic diagram of depositing a target structure layer thin film on a wafer with patterned photoresist from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0056] Figure 4L1 Schematic diagram of obtaining a target structure layer after etching and photoresist removal from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0057] Figure 4L2 Schematic diagram of obtaining a target structure layer after etching and photoresist removal from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure;

[0058] Figure 4M1 Schematic diagram of forming a magneto - optical modulation electrode by a photolithography process on a wafer containing a target structure layer from the perspective of a cross-section along A1 - A2 according to an embodiment of the present disclosure;

[0059] Figure 4M2 Schematic diagram of forming a magneto - optical modulation electrode by a photolithography process on a wafer containing a target structure layer from the perspective of a cross-section along B1 - B2 according to an embodiment of the present disclosure. Detailed implementation manners

[0060] To make the objectives, technical solutions, and advantages of the embodiments of the present disclosure clearer, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are some, but not all, of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present disclosure. In the embodiments of the present disclosure, different embodiments, different structural components, and structural layers can be combined with each other to form new embodiments.

[0061] The main structure of a thin-film lithium niobate electro-optic modulator consists of two parts: one is the electrical part, and the other is the optical part. The main function of the electrical part is to load the radio frequency signal onto the optical carrier. There have been a large number of research and technological achievements, focusing on aspects such as traveling-wave electrodes and impedance matching, to increase the matching degree of the electric field and the optical field in the device, reduce losses, and further improve the bandwidth of the device. The main function of the optical part is to achieve the response and transmission of the modulated optical signal. Currently, the conventional basic structure of the modulator is the Mach-Zehnder structure, and multiple MZ interference structures can be combined to form an electro-optic (IQ) modulator for coherent optical modules.

[0062] In the research and development, it is found that there are the following problems in the related technologies for lithium niobate-based electro-optic modulators that need to be solved urgently: In an electro-optic modulator, the core mechanism for realizing electro-optic modulation is based on the linear electro-optic effect (Pockels effect). By applying an external electric field, the refractive index of the crystal changes, and then the phase, intensity, or polarization state of the light wave is changed; Since lithium niobate material is a polar anisotropic crystal, the electro-optic coefficients in different directions are different, resulting in different modulation efficiencies for light; Therefore, the polarization control of the optical mode in the lithium niobate waveguide is one of the key difficulties that must be overcome in thin-film lithium niobate modulators and device integration. However, most of the existing control technologies are to perform optical path control by adding an additional external control component, introducing new materials or structural asymmetries, which easily lead to noise sources and mismatches, and there is a risk of failure and aging of the external components, increasing the cost; Some solutions are to achieve polarization state control by enhancing the vertical asymmetry of the waveguide structure or adopting a shallow-etched ridge waveguide structure. This method requires a very high degree of process controllability, and the device qualification rate is low, increasing the cost and risk of chip production.

[0063] In view of this, embodiments of the present disclosure provide a thin-film lithium niobate electro-optic modulator, a functional device, a control and manufacturing method. By integrating a lithium niobate waveguide structure, an electro-optic control electrode, and a magnetic control structure in a chip body, the magnetic control structure for generating a modulation magnetic field is introduced to both sides of the optical signal input section of the lithium niobate waveguide structure. Utilizing the Faraday rotation effect, when light passes through a magnetic field, the polarization plane parallel to the magnetic field vector direction will rotate. In this way, the polarization state of the optical signal in the optical signal input section can be controllably modulated. After the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated based on the above modulation magnetic field, the polarization state of the optical signal entering the electro-optic modulation section matches the polarity of the corresponding lithium niobate material. In this way, the electro-optic modulation efficiency of the thin-film lithium niobate electro-optic modulator can be improved. Moreover, the principle of the magneto-controlled polarization technology belongs to the intrinsic phenomenon of the electromagnetic field, and the influence of the external mechanical environment on the optical path is small, which can be applied to various application scenarios (such as optical communication, quantum communication and quantum computing, radar systems, optical coherence tomography, etc.), with stable performance and high reliability; at the same time, the above thin-film lithium niobate electro-optic modulator is compatible with the CMOS process, and a new functional area is added on the same chip to prepare the magnetic control structure to achieve high-efficiency integration, effectively improving the integration degree of the thin-film lithium niobate electro-optic modulator; reducing the optical path calibration difficulty or control difficulty caused by externally introduced devices. In the future optoelectronic integrated technology system, it has obvious advantages and application prospects.

[0064] The following will be introduced in detail with specific embodiments.

[0065] The first exemplary embodiment of the present disclosure provides a thin-film lithium niobate electro-optic modulator.

[0066] Figure 1 Schematically shows a structural block diagram of a chip body in a thin-film lithium niobate electro-optic modulator according to some embodiments of the present disclosure.

[0067] Referring to Figure 1 As shown, the above thin-film lithium niobate electro-optic modulator includes: a chip body. The above chip body includes: a base layer 1, a lithium niobate waveguide structure 2, an electro-optic control electrode 3, and a magnetic control structure 4 located above the base layer.

[0068] Referring to Figure 1 As shown in the segmented area indicated by the dashed line in

[0069] In an embodiment of the present disclosure, the tangential direction of the thin-film lithium niobate (LN) corresponding to the above thin-film lithium niobate electro-optic modulator can be x-cut (x-cut means that the wafer plane is parallel to the z-axis of the crystal and perpendicular to the x-axis of the crystal), y-cut (y-cut means that the wafer plane is parallel to the z-axis of the crystal and perpendicular to the y-axis of the crystal), and x-cut or y-cut means that the crystal axis (z-axis) is parallel to the wafer plane. The tangential direction of the above thin-film lithium niobate (LN) can also be z-cut (z-cut means that the wafer plane is perpendicular to the z-axis of the crystal).

[0070] Correspondingly, the electric field loading direction corresponding to the thin-film lithium niobate with different tangential directions can be adjusted accordingly. For the z-cut thin-film lithium niobate, a vertical electrode structure is adopted, the electric field is along the z-axis direction (vertical direction), and the transverse magnetic (TM) mode is selected for the transmission mode in the waveguide. This structure can add a dielectric buffer layer between the waveguide and the metal electrode to reduce the optical loss while increasing the electro-optic interaction strength. For the z-cut thin-film lithium niobate, the lithium niobate waveguide structure 2 can adopt a microstrip line or a coplanar waveguide structure. For the x-cut thin-film lithium niobate, a horizontal electrode structure is adopted, and the transverse electric (TE) mode is selected for the transmission mode in the waveguide at the same time.

[0071] Refer to Figure 1 As shown, taking the lithium niobate waveguide structure 2 corresponding to the x-cut thin-film lithium niobate (LN) as an example, the matching form between the electro-optic modulation section 22 and the electro-optic control electrode 3 is a ground-signal-ground (GSG) configuration. For the x-cut thin-film lithium niobate, the above electro-optic control electrode 3 is located on both sides of the above electro-optic modulation section 22. For example, it presents a symmetric distribution form of a ground electrode G, a signal electrode S, and a ground electrode G, constituting a TE mode.

[0072] For the z-cut thin-film lithium niobate (LN), the electro-optic control electrode 3 includes, in addition to the electrodes (as ground electrodes G) located on both sides of the above electro-optic modulation section 22, a signal electrode S located in the vertical direction of the electro-optic modulation section and above the electro-optic modulation section (not shown in the figure), which forms a TM mode with the ground electrode G on each side of the electro-optic modulation section.

[0073] In an embodiment of the present disclosure, a magnetic control structure 4 is integrated in the chip body. The magnetic control structure 4 is located on both sides of the optical signal input section 21 and is used to generate a modulation magnetic field. Using the Faraday rotation effect, the polarization plane parallel to the magnetic field vector direction rotates when light passes through the magnetic field. In this way, the polarization state of the optical signal in the optical signal input section 21 can be controllably modulated. After the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated based on the above modulation magnetic field, the polarization state of the optical signal entering the electro-optic modulation section 22 matches the polarity of the corresponding lithium niobate material. In this way, the electro-optic modulation efficiency of the thin-film lithium niobate electro-optic modulator can be improved.

[0074] In some embodiments, with reference to Figure 1 as shown, the magnetic regulation structure 4 includes: a target structure layer 41 and a magneto-optical regulation electrode 42 connected to the target structure layer 41.

[0075] Among them, the target structure layer 41 has the following characteristics: it exhibits anisotropy under the action of a magnetic field and has the Faraday rotation effect.

[0076] The magneto-optical regulation electrode 42 is used to load an electric control signal, generate a magnetic field in the target structure layer 41, regulate the magnetic field based on the modulation of the electric control signal, and further regulate the polarization state of the optical signal passing through the magnetic field.

[0077] In some embodiments, the target structure layer is a single-layer structure or a multi-layer structure.

[0078] In some limited examples, the magnetic materials or structures used for the target structure layer include, but are not limited to, one or more of the following: yttrium iron garnet YIG, bismuth-substituted yttrium iron garnet BIG, europium oxide EuO, gadolinium gallium garnet GGG, manganese zinc ferrite, an ultra-thin ferromagnetic metal multi-layer film structure with a thickness less than 10 nanometers, a magnetic topological insulator, a magnetoelectric composite structure, a two-dimensional magnetic material, a perovskite-type oxide. Any improved or novel functional material, or other magnetic materials or structures not yet listed, that exhibit anisotropy under the action of a magnetic field and have the Faraday rotation effect are within the protection scope of the present disclosure. In some embodiments, when the magnitude of the applied external magnetic field changes, the magnetic permeability corresponding to the target structure layer changes.

[0079] In some embodiments, the target structure layer contains a magneto-optical material, and the rotation angle of the linearly polarized light after passing through the target structure layer is affected by the following factors: the gyromagnetic characteristics of the magneto-optical material, the distance of the optical signal passing through the corresponding material layer of the magneto-optical material, the magnetic field direction, and the magnetic field strength.

[0080] As an example, in this embodiment, the magnetic material used for the target structure layer is yttrium iron garnet (YIG, Y3Fe5O 12 ), and the electric control signal is a radio frequency signal. By regulating the phase difference of the radio frequency signal loaded on the magneto-optical regulation electrode, the magnetic field direction is regulated, and further the polarization state of the optical signal passing through the magnetic field is regulated.

[0081] In other embodiments, the magnetic materials used for the target structure layer include, but are not limited to:

[0082] bismuth-substituted yttrium iron garnet (BIG, Bi3Fe5O 12 );

[0083] Europium oxide (EuO), which has limited usage scenarios, is ferromagnetic (Curie temperature is about 69K), exhibits strong magnetocrystalline anisotropy at low temperatures, has a significant magneto-optical response in the visible light band, and is suitable for low-temperature regulation scenarios;

[0084] Gadolinium gallium garnet (GGG, Gd3Ga5O 12 );

[0085] Manganese-zinc ferrites, whose magnetic anisotropy is optimized through composition regulation (such as the Mn:Zn ratio); this material has certain applications in the mid-infrared band, but the efficiency is lower than that of YIG;

[0086] Ultra-thin ferromagnetic metal multilayer film structures, such as Fe / Pt, Co / Pd; interface-induced perpendicular magnetic anisotropy (PMA), where the magnetization direction is perpendicular to the film surface; the Faraday rotation effect can be observed through ultra-thin design (thickness < 10nm);

[0087] Magnetic topological insulators (such as Cr-doped (Bi,Sb)2Te3), characteristics: the combination of surface state spin-momentum locking and bulk magnetic order realizes anisotropic magnetic response; the topological surface state enhances the magneto-optical effect and is suitable for terahertz band regulation;

[0088] Magnetoelectric composite structures (such as BiFeO3 / CoFe heterojunctions), anisotropy: the polarization direction of the multiferroic material BiFeO3 regulates the magnetic anisotropy of the CoFe layer; Faraday effect: the magnetization direction is controlled by an electric field to indirectly modulate the optical polarization rotation;

[0089] Two-dimensional and novel materials, such as: two-dimensional magnetic materials (such as CrI3, Fe3GeTe2 or their doped structures), anisotropy: interlayer antiferromagnetic coupling (CrI3) or in-plane ferromagnetic order (Fe3GeTe2) leads to strong direction dependence; Faraday effect: monolayer or few-layer structures exhibit tunable magneto-optical response in the visible light band; perovskite oxides (such as LaSrMnO3), which are ferromagnetic (Curie temperature is about 370K), lattice distortion induces magnetic anisotropy, and have magneto-optical modulation ability in the infrared band.

[0090] Figure 2A Schematically shows a schematic diagram of a structure after being cut along the A1-A2 section according to some embodiments of the present disclosure. Figure 2B Schematically shows another schematic diagram of a structure after being cut along the A1-A2 section according to some embodiments of the present disclosure.

[0091] In some embodiments, the above-mentioned base layer 1 includes one of the following structures:

[0092] Silicon-on-insulator (SOI) substrate, comprising: a silicon substrate, a silicon dioxide layer (as an example of a lower cladding layer) located on the silicon substrate; or,

[0093] Lithium niobate on insulator (LNOI) substrate of the first type, comprising: a silicon substrate, a silicon dioxide layer (as an example of a lower cladding layer) located on the silicon substrate, a lithium niobate layer located on the silicon dioxide layer; or,

[0094] Lithium niobate on insulator (LNOI) substrate of the second type, comprising: a lithium niobate substrate, a silicon dioxide layer (as an example of a lower cladding layer) located on the lithium niobate substrate, a lithium niobate layer located on the silicon dioxide layer.

[0095] In some embodiments, the lithium niobate material is bonded and peeled onto the surface of the silicon substrate or the lithium niobate substrate to form a thin-film lithium niobate wafer (for example, corresponding to the first type of LNOI substrate or the second type of LNOI substrate). By utilizing the refractive index difference between the silicon substrate and the cladding layer (a low-refractive-index cladding material, such as silicon dioxide), a thin-film lithium niobate modulator with more beneficial performance is prepared, which has the characteristics of high modulation rate, low power consumption, low half-wave voltage, and high material stability, and is applicable to fields such as data centers, backbone network communication transmission, microwave photonic links, and satellite-to-satellite communication, etc., and has good market prospects and economic value.

[0096] In the above embodiments, the process of preparing the thin-film lithium niobate modulator based on the SOI substrate and the LNOI substrate can be compatible with the existing CMOS process, and is suitable for large-scale production and promotion.

[0097] Referring to Figure 2A and Figure 2B As shown, the base layer 1 comprises: a substrate layer 11, which is a silicon substrate or a lithium niobate substrate; a lower cladding layer 12, here taking the silicon dioxide layer as an example, and some materials with a low refractive index (having a refractive index difference from the substrate) can be selected here, not limited to silicon dioxide. In Figure 2A the patterned first lithium niobate protrusion structure 221, the second lithium niobate protrusion structure 222, and the lithium niobate planar layer 131 remaining after etching are exemplified. This lithium niobate planar layer 131 can be the unetched substrate part in the two types of LNOI substrates, or the remaining part after etching of the lithium niobate thin film layer deposited on the SOI substrate.

[0098] In some embodiments, the above lithium niobate waveguide structure includes, but is not limited to, one of the following waveguide structures: strip waveguide structure, ridge waveguide structure, or heterogeneous integrated waveguide structure. In this embodiment, some waveguide structures are used as examples. The embodiments of the present disclosure mainly focus on integrating the magnetic modulation structure 4 in the chip body. The magnetic modulation structure 4 polarizes the optical signal input section of the lithium niobate waveguide structure in advance. The specific modulation waveguide structure can be various known or improved structural forms, and is not limited by the structural forms described in the embodiments.

[0099] Referring to Figure 2A As shown, a schematic diagram of the lithium niobate waveguide structure as a strip waveguide structure is illustrated. The above strip waveguide structure is a convex structure compared to the surface of the silica layer or the lithium niobate layer on top of the base layer, and the two sidewalls are vertical structures. In Figure 2A It also schematically shows the electro-optic modulation electrodes 3 disposed on both sides of the lithium niobate waveguide structure 2, including: a first ground electrode 31, a signal electrode 32, and a second ground electrode 33.

[0100] The above ridge waveguide structure is a convex structure compared to the surface of the silica layer or the lithium niobate layer on top of the base layer, and the two sidewalls have inclined slopes.

[0101] Referring to Figure 2B As shown, a schematic diagram of the lithium niobate waveguide structure as a heterogeneous integrated waveguide structure is illustrated. The above heterogeneous integrated waveguide structure includes: a lithium niobate thin film layer 20 located on the SOI substrate, a heterogeneous layer 5 located on top of the above lithium niobate thin film layer 20 and having a convex structure. The above heterogeneous layer 5 and the lithium niobate thin film layer 20 form a heterojunction, and the refractive index of the material of the above heterogeneous layer is equal to or higher than the refractive index of the above lithium niobate thin film layer.

[0102] In some embodiments, the material of the heterogeneous layer includes, but is not limited to, one or more of the following materials: silicon nitride, tantalum pentoxide, chalcogenide glass, silicon.

[0103] Figure 2C Another schematic diagram cut along the A1-A2 cross-section according to some embodiments of the present disclosure is schematically shown.

[0104] In some embodiments, there is also a target cladding layer 6 between the above base layer 1 and the above magnetic modulation structure 4. As shown in FIGS. 2 and Figure 2C As shown, the above target cladding layer 6 covers the sidewalls and the top of the above lithium niobate waveguide structure 2. The above target cladding layer 6 is used as a protective layer for the above lithium niobate waveguide structure during the process of fabricating the above magnetic modulation structure, and serves as a cladding waveguide (upper cladding) outside the above lithium niobate waveguide structure in the above thin film lithium niobate electro-optic modulator to first couple and transfer the optical signal into the above lithium niobate waveguide structure.

[0105] For example, in an exemplary manufacturing process, first, a patterned lithium niobate waveguide structure 2 and an electro-optic modulation electrode 3 are fabricated on a base layer 1, and then the material corresponding to the target cladding layer 6 is deposited for protection. After that, a patterned photoresist is formed based on a lithography process. Then, a magnetic material layer is deposited, and the patterned target structure layer is obtained by etching based on the pattern of the photoresist. After that, deposition and patterning are continued to obtain a magneto-optic modulation electrode. In another exemplary manufacturing process, first, a patterned lithium niobate waveguide structure 2 and an electro-optic modulation electrode 3 are fabricated on a base layer 1. Then, based on the lithography process, first, a photoresist is deposited, and only area exposure and development are used for this photoresist during subsequent exposure, for example, only the two side regions corresponding to the optical signal input section 21 are exposed, and no exposure is performed in the electro-optic modulation section 22. The photoresist deposited on the patterned lithium niobate waveguide structure 2 and the electro-optic modulation electrode 3 can also act as a protective layer, which can prevent dust or impurities from entering the already fabricated patterned lithium niobate waveguide structure 2 during subsequent manufacturing processes, ensuring the stable performance of the fabricated device.

[0106] In some embodiments, the above-mentioned target cladding layer is a single-layer structure or a multi-layer structure, and the material of the above-mentioned target cladding layer is one or more of the following: silicon dioxide, silicon nitride, silicon oxynitride, SU-8 polymer (a negative, near-ultraviolet-resistant, and thermosetting polymer), magnesium oxide, tantalum oxide, aluminum oxide, titanium oxide.

[0107] The above-mentioned target cladding layer has the following three functions: by setting the target cladding layer as a cladding waveguide, the light in the optical fiber will first be coupled into the cladding waveguide, and then based on the tapered distribution at the transmission end, the light in the cladding waveguide will be coupled into the LNOI waveguide in the form of mode evolution, thereby improving the coupling efficiency; this target cladding layer also serves as a protective layer for the already fabricated chip main body part, effectively sealing the LNOI waveguide during the process of fabricating the magnetic modulation structure, avoiding impurity contamination or damage to the LNOI waveguide caused by subsequent processes such as magnetic material deposition and lithography; in addition, by optimizing the selection of the material of the target cladding layer, such as choosing the same material for the lower cladding and the upper cladding or choosing materials with similar refractive indices, such as silicon dioxide, silicon nitride, etc., the refractive index difference between the upper and lower claddings of the optical waveguide can be reduced, the existence of high-order optical waveguide modes in the lithium niobate thin-film optical waveguide can be reduced, the coupling loss can be reduced, and the spatial distribution size of the optical waveguide mode can be increased.

[0108] In some embodiments, the above-mentioned thin-film lithium niobate electro-optic modulator further includes: packaging components (such as heat sinks, housings, objective lenses, etc.), which are used to package the chip body, and correspondingly connect the circuit of the chip body and communicate with the corresponding optical path. For example, after the chip body is prepared, the radio frequency characteristics of the device are simulated and designed based on circuit simulation software (such as HFSS simulation software) to obtain key structural parameters. Based on these structural parameters, materials for packaging components such as heat sinks, housings, and lenses are selected. Then, wire bonding and packaging are carried out to package the optical and electrical structures of the thin-film lithium niobate chip into the designed housing, which includes multiple general technical steps such as wire bonding, chip mounting, dispensing, curing, coupling, fixing, and sealing. Finally, a packaged modulator is formed. Devices such as vector network analyzers, spectrometers, and spectrum analyzers are used to test the performance of the packaged modulator to obtain key parameters such as loss, bandwidth, and half-wave voltage.

[0109] In summary, in the thin-film lithium niobate electro-optic modulator provided in this embodiment, the core mechanism for realizing electro-optic modulation is based on the linear electro-optic effect (Pockels effect). By applying an external electric field, the refractive index of the crystal changes, thereby changing the phase, intensity, or polarization state of the light wave. Since the lithium niobate material is a polar anisotropic crystal, the electro-optic coefficients in different directions are different, resulting in different modulation efficiencies for light. In the device structure provided in this disclosure embodiment, by integrating a lithium niobate waveguide structure, an electro-optic control electrode, and a magnetic control structure in the chip body, the magnetic control structure for generating a modulation magnetic field is introduced to both sides of the optical signal input section of the lithium niobate waveguide structure. Using the Faraday rotation effect, the polarization plane of light parallel to the magnetic field vector direction will rotate when passing through the magnetic field. In this way, the polarization state of the optical signal in the optical signal input section can be controllably modulated. After the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated based on the above modulation magnetic field, the polarization state of the optical signal entering the electro-optic modulation section matches the polarity of the corresponding lithium niobate material. In this way, the electro-optic modulation efficiency of the thin-film lithium niobate electro-optic modulator can be improved. Moreover, the principle of the magnetic control polarization technology adopted belongs to the intrinsic phenomenon of the electromagnetic field, and the influence of the external mechanical environment on the optical path is small, and it can be applied to various application scenarios (such as optical communication, quantum communication and quantum computing, radar systems, optical coherence tomography, etc.), with stable performance and high reliability.

[0110] Since the magnetic modulation structure, the lithium niobate waveguide structure, and the electro-optic modulation electrode are integrated on the same chip and highly compatible with semiconductor micro-nano processing technology, adding a new functional area on the chip can achieve the integration of the magnetic modulation structure without the need to add external modulation devices outside the chip, avoiding the noise sources and mismatches introduced by adding external modulation devices. The magnetic modulation structure, the lithium niobate waveguide structure, and the electro-optic modulation electrode can be packaged and tested synchronously on the same chip, improving the integration of the thin-film lithium niobate electro-optic modulator and reducing the difficulty of optical path calibration or modulation caused by externally introduced devices. It has obvious advantages and application prospects in the future optoelectronic integration technology system.

[0111] The second exemplary embodiment of the present disclosure provides a modulation method for the above-mentioned thin-film lithium niobate electro-optic modulator.

[0112] Figure 3 A flowchart of a modulation method for a thin-film lithium niobate electro-optic modulator according to some embodiments of the present disclosure is schematically shown.

[0113] Refer to Figure 3 As shown, the modulation method for the thin-film lithium niobate electro-optic modulator includes the following steps: S310, S320, and S330.

[0114] In step S310, a modulation magnetic field is generated based on the control of the magnetic modulation structure.

[0115] In some embodiments, the target structural layer of the above-mentioned magnetic modulation structure includes a magneto-optical material, and the rotation angle of the linearly polarized light after passing through the above-mentioned target structural layer is affected by the following factors: the gyromagnetic property of the magneto-optical material, the distance of the optical signal passing through the corresponding material layer of the magneto-optical material, the magnetic field direction, and the magnetic field intensity. The magnetic field is modulated by controlling the intensity and phase of the electrical signal applied to the magneto-optical modulation electrode connected to the magnetic modulation structure.

[0116] As an example, in this embodiment, the magnetic material used for the target structural layer is yttrium iron garnet (YIG, Y3Fe5O 12 ), and the electrical control signal is a radio frequency signal. The polarization state of the optical signal passing through the magnetic field is modulated by controlling the phase difference of the radio frequency signal applied to the magneto-optical modulation electrode.

[0117] In step S320, after the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated based on the above-mentioned modulation magnetic field, the polarization state of the optical signal entering the electro-optic modulation section is matched with the polarity of the corresponding lithium niobate material.

[0118] For example, if the polarity of the lithium niobate material is x-cut, the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated by modulating the magnetic field, so that the polarization state of the optical signal entering the electro-optic modulation section is along the z-axis direction with the largest electro-optic coefficient, realizing the polarization state matching the polarity of the lithium niobate material.

[0119] In step S330, in the above-mentioned electro-optic modulation section, based on the input control of the electro-optic control electrode, the refractive index of the above-mentioned lithium niobate waveguide structure is controllably adjusted and the phase, intensity or polarization state of the passing optical signal is affected, realizing electro-optic modulation.

[0120] In the electro-optic modulation section, the refractive index of the lithium niobate crystal changes due to the applied external electric field, thereby changing the phase, intensity or polarization state of the light wave, etc.; through the input control of the electro-optic control electrode, the modulation of the optical signal is realized based on the Pockels effect. In some specific application scenarios, it can be the modulation of at least one of the polarization, intensity or phase of the optical signal.

[0121] For more details of this embodiment, reference can be made to the relevant description of the first embodiment, which will not be elaborated here.

[0122] The third exemplary embodiment of the present disclosure provides a manufacturing method of a thin-film lithium niobate electro-optic modulator.

[0123] The above manufacturing method includes: preparing a substrate; based on thin-film preparation and patterning processes, fabricating a lithium niobate waveguide structure, an electro-optic control electrode and a magnetic control structure on the above substrate. Among them, the above lithium niobate waveguide structure includes: an optical signal input section, an electro-optic modulation section and an optical signal output section; the above electro-optic control electrode is located on both sides of the above electro-optic modulation section; the above magnetic control structure is located on both sides of the above optical signal input section for generating a modulation magnetic field; after controllably modulating the polarization state of the optical signal transmitted in the above optical signal input section based on the above modulation magnetic field, the polarization state of the optical signal entering the above electro-optic modulation section matches the polarity of the corresponding lithium niobate material.

[0124] In some embodiments, the above substrate includes one of the following structures: a silicon-on-insulator (SOI) substrate, a first type of LNOI substrate including a silicon substrate, a second type of LNOI substrate including a lithium niobate substrate; the first type of LNOI substrate includes: a silicon substrate, a lower cladding layer located on the above silicon substrate, here taking a silicon dioxide layer as an example of the lower cladding layer, and a lithium niobate layer located on the above silicon dioxide layer; the second type of LNOI substrate includes: a lithium niobate substrate, a lower cladding layer located on the above lithium niobate substrate, and a lithium niobate layer located on the above silicon dioxide layer.

[0125] Based on thin-film preparation and patterning processes, fabricating a lithium niobate waveguide structure, an electro-optic control electrode and a magnetic control structure on the above substrate includes:

[0126] For an SOI substrate, a lithium niobate thin film is fabricated on the silicon-on-insulator (SOI) substrate based on the ion cutting technology, specifically including: bombarding a lithium niobate (LN) wafer with high-energy ions to form an ion implantation layer at a preset depth; bonding the ion-implanted lithium niobate (LN) wafer to the SOI substrate and performing annealing treatment. During the annealing treatment, the implanted ions expand, causing the bonded structure to detach from the position at the preset depth, and peeling to obtain an SOI substrate with a lithium niobate thin film.

[0127] For an LNOI substrate or an SOI substrate with a lithium niobate thin film, a patterned lithium niobate waveguide structure is fabricated based on diamond cutting, chemical mechanical polishing, dry etching, or photolithography processes.

[0128] Based on the thin film preparation process, a target cladding layer structure is formed on the substrate including the patterned lithium niobate waveguide structure; the above target cladding layer structure coats the sidewalls and the top of the above lithium niobate waveguide structure; the above target cladding layer structure serves as a protective layer for the above lithium niobate waveguide structure during the process of fabricating the magnetic modulation structure; after fabrication, in the above thin film lithium niobate electro-optic modulator, it first couples and transfers optical signals to the above lithium niobate waveguide structure as a cladding waveguide.

[0129] Based on the thin film preparation and photolithography processes, a patterned electro-optic modulation electrode is fabricated on the above cladding layer structure.

[0130] Based on the thin film preparation and photolithography processes, a patterned magnetic modulation structure is fabricated on the substrate including the patterned lithium niobate waveguide structure and the electro-optic modulation electrode; wherein, during the process of fabricating the patterned magnetic modulation structure, the photoresist serves as the outermost protective layer for the already fabricated patterned lithium niobate waveguide structure and the electro-optic modulation electrode, and regional exposure is adopted.

[0131] In this embodiment, the fabricated lithium niobate waveguide structure is one of the following waveguide structures: strip waveguide structure, ridge waveguide structure, or heterogeneous integrated waveguide structure.

[0132] In some embodiments, based on the photolithography process, a lithium niobate waveguide structure is fabricated, including:

[0133] Forming a hard mask material layer on the lithium niobate thin film; for example, using deposition methods such as PECVD / LPCVE to deposit a multi-layer material structure with different refractive indices, including a stack structure composed of silicon dioxide thin film and silicon nitride thin film, or depositing a silicon nitride thin film.

[0134] Forming a photoresist on the hard mask material layer and performing exposure, development, and etching to obtain a photoresist pattern.

[0135] Using the photoresist pattern as a mask to etch the hard mask material layer to obtain a patterned hard mask.

[0136] Based on the patterned hard mask, the lithium niobate thin film is etched to obtain a strip waveguide structure; the strip waveguide structure is a convex structure compared to the surface of the silicon dioxide layer or the lithium niobate layer on top of the base layer, and the two sidewalls are vertical structures.

[0137] Next, with reference to Figures 4A to 4M2 to describe Figure 1 and Figure 2C the manufacturing process of the corresponding structure of the thin-film lithium niobate electro-optic modulator shown. The manufacturing processes of other structures can be understood by reference or the refinement process can be adjusted, and semiconductor micro-nano manufacturing technology can be used. This electro-optic modulator is compatible with the existing CMOS process.

[0138] Figures 4A to 4M2 Schematically shows a schematic diagram of the manufacturing process of a patterned lithium niobate waveguide structure based on a lithography process according to some embodiments of the present disclosure.

[0139] Figure 4A A cross-sectional structure diagram of a substrate prepared for an embodiment of the present disclosure. With reference to Figure 4A shown, first prepare a substrate. Here, a first type of LNOI substrate is taken as an example. Here, the substrate can also be the SOI substrate with a lithium niobate thin film formed by the aforementioned ion implantation and lift-off. The above substrate includes, from bottom to top: a silicon substrate 11, a silicon dioxide layer (as an example of a lower cladding layer) 12, and a lithium niobate layer 13.

[0140] Figure 4B1 A structure diagram of the substrate after depositing a hard mask material layer along the cross-section A1-A2 perspective of an embodiment of the present disclosure; Figure 4B2 A structure diagram of the substrate after depositing a hard mask material layer along the cross-section B1-B2 perspective of an embodiment of the present disclosure.

[0141] Combined with Figure 4B1 and Figure 4B2 shown, using deposition methods such as PECVD (plasma-enhanced chemical vapor deposition) / LPCVE (low-pressure chemical vapor deposition), deposit a hard mask material layer 14 on the substrate, and the hard mask material layer 14 covers the entire wafer.

[0142] Figure 4C1 A structure diagram of the substrate after depositing a hard mask material layer and then depositing a photoresist along the cross-section A1-A2 perspective of an embodiment of the present disclosure; Figure 4C2 A structure diagram of the substrate after depositing a hard mask material layer and then depositing a photoresist along the cross-section B1-B2 perspective of an embodiment of the present disclosure.

[0143] Next, combined with Figure 4C1And Figure 4C2 As shown, continue to deposit the first photoresist 15 on the hard mask material layer 14, and the first photoresist 15 covers the entire wafer.

[0144] Figure 4D1 It is a schematic structural diagram of the patterned photoresist obtained by exposure, development, and etching from the perspective of the cross-section along A1-A2 of an embodiment of the present disclosure; Figure 4D2 It is a schematic structural diagram of the patterned photoresist obtained by exposure, development, and etching from the perspective of the cross-section along B1-B2 of an embodiment of the present disclosure.

[0145] Combined with Figure 4D1 and Figure 4D2 As shown, perform exposure, development, and etching to remove the exposed / unexposed (corresponding to positive or negative photoresist) portions of the photoresist, and obtain the first patterned photoresist 151. The shape corresponding to the first patterned photoresist can refer to the shape of the lithium niobate waveguide structure 2 from the top-down perspective in Figure 1 , presenting a shape where the input end is connected to two branch arms and then to the output end. In this step, high-precision projection lithography is used. On the one hand, it is necessary to achieve the accuracy of the minimum design pattern, and on the other hand, it is necessary to ensure the smooth implementation of etching the pattern in the next step using the photoresist as a mask.

[0146] Figure 4E1 It is a schematic structural diagram of the patterned hard mask obtained by etching the hard mask based on the patterned photoresist from the perspective of the cross-section along A1-A2 of an embodiment of the present disclosure; Figure 4E2 It is a schematic structural diagram of the patterned hard mask obtained by etching the hard mask based on the patterned photoresist from the perspective of the cross-section along B1-B2 of an embodiment of the present disclosure.

[0147] Combined with Figure 4E1 and Figure 4E2 As shown, adopt a two-step etching method. First, based on etching techniques such as ICP / RIE, using the first patterned photoresist 151 as a masking structure, etch the deposited hard mask material layer 14, and remove the first patterned photoresist 151 to obtain the patterned hard mask 141, that is, obtain a masking structure that can meet the standards both in the plane and in the vertical direction (for the subsequent preparation of the patterned lithium niobate waveguide structure); the main role of the patterned hard mask in the plane is to ensure the dimensions of the lines (such as the dimensions along the Figure 1 x direction and z direction in Figure 1 ), and in the vertical direction (such as along the

[0148] Figure 4F1 y direction in

[0148] Figure 4F1 ), it is mainly used for the steepness of pattern transfer. In this embodiment, through the two-step etching method, the shape of the sidewall can be relatively accurately transferred, facilitating the fabrication of a strip waveguide structure with a vertical sidewall or a ridge waveguide structure with an inclined slope on the sidewall.It is a schematic structural diagram of a patterned lithium niobate waveguide structure obtained after etching based on a patterned hard mask from the perspective of cutting along the A1-A2 cross section according to an embodiment of the present disclosure; Figure 4F2 It is a structural schematic diagram of a patterned lithium niobate waveguide structure obtained after etching based on a patterned hard mask from the perspective of cutting along the B1-B2 cross section of an embodiment of the present disclosure.

[0149] Combination Figure 4F1 and Figure 4F2 As shown, the patterned hard mask 141 is used as a masking structure, and the lithium niobate layer 13 is etched and the hard mask is removed based on an etching method such as ICP / RBE / RIE (specifically, the residual substances on the surface of the lithium niobate can be removed by plasma bombardment, wet dissolution, dry etching, or a combination of processes to leave a clean lithium niobate surface) to obtain a patterned lithium niobate waveguide structure 2, for example, Figure 4F1 The first lithium niobate protrusion structure 221 and the second lithium niobate protrusion structure 222 (corresponding to Figure 1 The two extension arms in the optical signal input section 21 and the third lithium niobate protrusion structure 211 in the optical signal input section 21; the remaining portion of the lithium niobate layer 13 after etching or the portion not etched is described as a lithium niobate planar layer 131.

[0150] Figure 4G1 It is a schematic structural diagram of forming a target cladding layer on a patterned lithium niobate waveguide structure from the perspective of cutting along the A1-A2 cross section according to an embodiment of the present disclosure; Figure 4G2 It is a schematic structural diagram of forming a target cladding layer on a patterned lithium niobate waveguide structure from the perspective of a B1-B2 cross section according to an embodiment of the present disclosure.

[0151] In some embodiments, in combination Figure 4G1 and Figure 4G2 As shown, based on deposition methods such as PECVD / LPCVE, a target coating layer 6 is formed on the patterned lithium niobate waveguide structure 2. The target coating layer 6 is coated on the side wall and top of the lithium niobate waveguide structure 2, and serves as a protective layer during device manufacturing and can retain at least part of the thickness (part of the thickness may be lost or not lost during etching) to the final device.

[0152] The above-mentioned target cladding layer has the following three functions: By setting the target cladding layer as a cladding waveguide, the light in the optical fiber will first be coupled into the cladding waveguide, and then based on the tapered distribution at the transmission end, the light in the cladding waveguide will be coupled into the LNOI waveguide in the form of mode evolution, thereby improving the coupling efficiency; this target cladding layer also serves as a protective layer for the already prepared chip main body, effectively sealing the LNOI waveguide during the process of fabricating the magnetic control structure, avoiding impurity contamination or damage caused to the LNOI waveguide by subsequent processes such as magnetic material deposition and lithography; in addition, by optimizing the selection of the material of the target cladding layer, such as choosing the same material for the lower cladding and the upper cladding or choosing materials with similar refractive indices, such as silica, silicon nitride, etc., the refractive index difference between the upper and lower claddings of the optical waveguide can be reduced, the existence of high-order optical modes in the lithium niobate thin film optical waveguide can be reduced, the coupling loss can be reduced, and the spatial distribution size of the optical mode can be increased.

[0153] Figure 4H1 FIG. is a schematic structural diagram of forming an electro-optic modulation electrode based on a lithography process from the perspective of a cross-section along A1-A2 of an embodiment of the present disclosure; Figure 4H2 FIG. is a schematic structural diagram of forming an electro-optic modulation electrode based on a lithography process from the perspective of a cross-section along B1-B2 of an embodiment of the present disclosure.

[0154] According to a similar lithography process as above, a patterned electro-optic modulation electrode can be continuously formed, and the detailed process will not be elaborated in detail. Combining Figure 1 、 Figure 4H1 and Figure 4H2 As shown, the prepared patterned electro-optic modulation electrode 3 includes: a first ground electrode 31, a signal electrode 32, and a second ground electrode 33. Specifically, metal thin films with a certain ratio and thickness can be deposited by techniques such as electron beam evaporation and sputtering. On the one hand, the Schottky barrier of the electrode is considered, and on the other hand, the stability of the electrode structure needs to be considered. In the embodiments of the present disclosure, a composite thin film with a Ti / Pt / Au multi-layer structure is used as the electro-optic modulation electrode.

[0155] Figure 4I1 FIG. is a schematic structural diagram of depositing photoresist on a chip with a prepared lithium niobate waveguide structure and electro-optic modulation electrode from the perspective of a cross-section along A1-A2 of an embodiment of the present disclosure; Figure 4I2 FIG. is a schematic structural diagram of depositing photoresist on a chip with a prepared lithium niobate waveguide structure and electro-optic modulation electrode from the perspective of a cross-section along B1-B2 of an embodiment of the present disclosure.

[0156] Next, a magnetic control structure is continuously fabricated on the chip with the prepared lithium niobate waveguide structure and electro-optic modulation electrode. Combining Figure 4I1 and Figure 4I2As shown, a second photoresist 16 is deposited on the prepared lithium niobate waveguide structure and electro-optic modulation electrodes. The second photoresist covers the entire wafer, and the photoresist located on the electro-optic modulation electrodes and the lithium niobate waveguide region corresponding to the electro-optic modulation section 22 can protect the formed structure during the manufacturing process.

[0157] Figure 4J1 FIG. 4 is a schematic structural diagram of the patterned photoresist obtained after regional exposure of the deposited photoresist from the perspective of the cross-section along A1-A2 of an embodiment of the present disclosure; Figure 4J2 FIG. 6 is a schematic structural diagram of the patterned photoresist obtained after regional exposure of the deposited photoresist from the perspective of the cross-section along B1-B2 of an embodiment of the present disclosure.

[0158] The deposited second photoresist 16 is subjected to regional exposure, development, and partial photoresist removal processes to obtain a second patterned photoresist 161. Referring to FIGS. 13 and 14, the photoresist located on the first formed structure (the lithium niobate waveguide structure corresponding to the electro-optic modulation electrodes 3 and the electro-optic modulation section 22) is retained until after the magnetic modulation structure is fabricated and then removed, which is used to continue protecting the formed structure and prevent the impact on the electro-optic modulation electrodes and the lithium niobate waveguide structure during the subsequent deposition of the target structure layer film. Figure 4J1 and Figure 4J2 As shown in FIGS. 13 and 14, the photoresist located on the first formed structure (the lithium niobate waveguide structure corresponding to the electro-optic modulation electrodes 3 and the electro-optic modulation section 22) is retained until after the magnetic modulation structure is fabricated and then removed, which is used to continue protecting the formed structure and prevent the impact on the electro-optic modulation electrodes and the lithium niobate waveguide structure during the subsequent deposition of the target structure layer film.

[0159] For the second formed structure (the lithium niobate waveguide structure corresponding to the optical signal input section 21 and the optical signal output section 23), since there is a target coating layer 6, the second photoresist deposited above this part can be removed. In embodiments without the target coating layer, for the retention of the photoresist above the second formed structure, the retention method shown by the dashed box in FIG. 18 can be referred to, that is, there is a photoresist mask part 161a used as a mask for fabricating the target structure layer and a photoresist protection layer part 161b used as a protection layer for the lithium niobate waveguide structure above the lithium niobate planar layer 131 corresponding to the second formed structure. Figure 4J2 As shown by the dashed box in FIG. 18, that is, there is a photoresist mask part 161a used as a mask for fabricating the target structure layer and a photoresist protection layer part 161b used as a protection layer for the lithium niobate waveguide structure above the lithium niobate planar layer 131 corresponding to the second formed structure.

[0160] In this embodiment, due to the presence of the target coating layer 6, the impact of subsequent manufacturing processes on the lithium niobate waveguide structure can be avoided based on the target coating layer; in other embodiments without the target coating layer, simply based on the second photoresist 16 deposited in this step and the corresponding photoresist removal settings, the photoresist located on the formed structure is retained. In this case, referring to the structure shown by the dashed box in FIG. 23, the target coating layer 6 does not exist, and the replaced structure is: there is a photoresist mask part 161a used as a mask for fabricating the target structure layer and a photoresist protection layer part 161b used as a protection layer for the lithium niobate waveguide structure above the lithium niobate planar layer 131. In this case, based on the photoresist protection layer part 161b, the prepared electro-optic modulation electrodes and the lithium niobate waveguide structure can also be protected. Figure 4J2 As shown by the dashed box in FIG. 23, the target coating layer 6 does not exist, and the replaced structure is: there is a photoresist mask part 161a used as a mask for fabricating the target structure layer and a photoresist protection layer part 161b used as a protection layer for the lithium niobate waveguide structure above the lithium niobate planar layer 131. In this case, based on the photoresist protection layer part 161b, the prepared electro-optic modulation electrodes and the lithium niobate waveguide structure can also be protected.

[0161] Figure 4K1 Schematic diagram of depositing a target structure layer film on a wafer with patterned photoresist from the perspective of being cut along the A1 - A2 section according to an embodiment of the present disclosure; Figure 4K2 Schematic diagram of depositing a target structure layer film on a wafer with patterned photoresist from the perspective of being cut along the B1 - B2 section according to an embodiment of the present disclosure.

[0162] Referring to Figure 4K1 and Figure 4K2 as shown, a target structure layer film 40 is deposited on the second patterned photoresist 161. Referring to Figure 4K1 as shown, due to the presence of the photoresist pattern retained on the first formed structure, there is an interlayer (photoresist) between the deposited target structure layer film 40 and the electro - optical modulation electrode 3, effectively protecting the already fabricated first formed structure during the fabrication process of the magnetic modulation structure, achieving high - efficiency integration while ensuring the stable performance of the device. The protection form for the second formed structure has been described in detail previously and will not be elaborated here.

[0163] Figure 4L1 Schematic diagram of the target structure layer obtained after etching and photoresist removal from the perspective of being cut along the A1 - A2 section according to an embodiment of the present disclosure; Figure 4L2 Schematic diagram of the target structure layer obtained after etching and photoresist removal from the perspective of being cut along the B1 - B2 section according to an embodiment of the present disclosure.

[0164] After depositing the target structure layer film 40 on the second patterned photoresist 161, a patterned target structure layer is obtained based on etching and the photoresist is removed, and a target structure layer is obtained in the region corresponding to the optical signal input section. Combining Figure 1 、 Figure 4L1 and Figure 4L2 as shown, it shows the first magnetic structure layer 411 and the second magnetic structure layer 412 distributed on both sides of the third lithium niobate protrusion structure 211 in the optical signal input section 21; at the same time, the photoresist pattern covering the first formed structure still remains (as shown by the second patterned photoresist 161 in the perspective of Figure 4L1 ) until the fabrication of the magneto - optical modulation electrode is completed.

[0165] Figure 4M1 Schematic diagram of forming a magneto - optical modulation electrode on a wafer containing a target structure layer through a photolithography process from the perspective of being cut along the A1 - A2 section according to an embodiment of the present disclosure; Figure 4M2 Schematic diagram of forming a magneto - optical modulation electrode on a wafer containing a target structure layer through a photolithography process from the perspective of being cut along the B1 - B2 section according to an embodiment of the present disclosure.

[0166] Based on a similar lithography process, a magneto-optical modulation electrode 42 can be continuously formed on the wafer containing the target structure layer. Referring to Figure 4M1 and Figure 4M2 , a first magneto-optical modulation electrode 421 and a second magneto-optical modulation electrode 421 are shown on both sides of the third lithium niobate protrusion structure 211 distributed in the optical signal input section 21. Subsequently, each side of the magneto-optical modulation electrode and the corresponding magnetic structure layer can be connected by wire bonding in micro-nano processing. During the fabrication of the patterned magneto-optical modulation electrode, the photoresist pattern covering the first formed structure remains (see the second patterned photoresist 161 shown in the perspective view in Figure 4M1 ).

[0167] Next, the photoresist pattern covering the first formed structure is removed to obtain the chip body of the thin-film lithium niobate electro-optic modulator.

[0168] After the chip body is prepared, the radio frequency characteristics of the device are simulated and designed based on circuit simulation software (such as HFSS simulation software) to obtain key structural parameters. Based on these structural parameters, packaging components such as heat sinks, packages, and lenses are selected. Then wire bonding packaging is carried out to package the optical and electrical structures of the thin-film lithium niobate chip into the designed package, which includes multiple general technical processes such as wire bonding, chip mounting, dispensing, curing, coupling, fixing, and sealing. Finally, a packaged modulator is formed. Devices such as a vector network analyzer, a spectrometer, and a spectrum analyzer are used to test the performance of the packaged modulator to obtain key parameters such as loss, bandwidth, and half-wave voltage.

[0169] In the manufacturing method provided in this embodiment, by controlling the retention period of the photoresist, the formed structure is effectively protected and high-efficiency integration of the thin-film lithium niobate electro-optic modulator is achieved. It is compatible with CMOS technology and micro-nano processing technology and can be applied industrially. By using a secondary etching method in lithography, precise pattern transfer and flatness control of the sidewalls are realized. By setting the target cladding layer as a cladding waveguide, the light in the optical fiber will first be coupled into the cladding waveguide, and then based on the tapered distribution at the transmission end, the light in the cladding waveguide will be coupled into the LNOI waveguide in the form of mode evolution, thereby improving the coupling efficiency. This target cladding layer also serves as a protective layer for the already prepared chip body part, effectively sealing the LNOI waveguide during the process of fabricating the magnetic control structure, avoiding impurity contamination or damage to the LNOI waveguide caused by subsequent magnetic material deposition, lithography, etc. In addition, by optimizing the selection of the material of the target cladding layer, such as choosing the same material for the lower cladding and the upper cladding or choosing materials with similar refractive indices, such as silicon dioxide, silicon nitride, etc., the refractive index difference between the upper and lower claddings of the optical waveguide can be reduced, the existence of high-order optical waveguide modes in the lithium niobate thin-film optical waveguide can be reduced, the coupling loss can be reduced, and the spatial distribution size of the optical waveguide mode can be increased.

[0170] The fourth exemplary embodiment of the present disclosure provides a functional device including the above-mentioned thin-film lithium niobate electro-optic modulator.

[0171] The above functional device includes, but is not limited to, one or more of the following devices:

[0172] A coherent optical module for long-distance optical fiber communication (a specific application of an optical communication device);

[0173] A silicon-based heterogeneous integrated optical chip;

[0174] An optical radio frequency wireless communication device for 5G / 6G base station fronthaul;

[0175] A silicon photonics heterogeneous integrated device (e.g., for a data center);

[0176] A modulation chip for quantum communication or quantum computing;

[0177] A chirp modulator in lidar;

[0178] An intensity modulator in lidar;

[0179] A tunable laser;

[0180] A photonic radio frequency front-end device for radar detection and electronic countermeasure;

[0181] A high-speed swept-source for medical optical coherence tomography;

[0182] A phase-sensitive modulation module for pipeline, bridge, and building monitoring, etc.

[0183] By introducing a magnetic control structure corresponding to a magnetic material such as YIG (yttrium iron garnet) into the thin-film lithium niobate electro-optic modulator, the polarization state of the transmitted light is modulated by using the Faraday rotation effect in which the plane of polarization parallel to the magnetic field vector direction rotates when light passes through a magnetic field; at the same time, the magnetic field is modulated by controlling the input signal applied to the magnetic control structure, so as to realize the modulation of the polarization direction of the transmitted light, and further improve the working efficiency and integration degree of the thin-film lithium niobate modulator.

[0184] It should be noted that, without further limitations, elements defined by the statement "comprising one..." do not exclude the existence of additional identical elements in the process, method, article or device comprising the said elements. It should be noted that, in the drawings or the main body of the specification, implementation manners that are not illustrated or described are all forms known to those of ordinary skill in the art and are not described in detail. In addition, the above definitions of the various elements are not limited to the specific forms mentioned in the embodiments, and those of ordinary skill in the art can simply modify or replace them. It should be noted that, in the drawings or the description of the specification, similar or identical parts are all denoted by the same reference numerals. Implementation manners that are not illustrated or described in the drawings are forms known to those of ordinary skill in the art. Additionally, although this document may provide examples of parameters containing specific values, it should be understood that the parameters do not necessarily have to be exactly equal to the corresponding values, but may approximate the corresponding values within an acceptable error tolerance or design constraint.

[0185] Moreover, for the purpose of keeping the drawings neat, some well-known and commonly used structures and components may be illustrated in a simplified schematic manner in the drawings. Additionally, some features in the drawings of this case may be slightly enlarged or have their proportions or dimensions changed to facilitate understanding and viewing of the technical features of this disclosure, but this is not used to limit this disclosure. It is hereby declared that the actual size and specifications of the products manufactured in accordance with the content disclosed in this disclosure can be adjusted according to the requirements during production, the characteristics of the products themselves, and in combination with the content disclosed below in this disclosure.

[0186] The above are only specific implementation manners of this disclosure, enabling those skilled in the art to understand or implement this disclosure. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of this disclosure. Therefore, this disclosure will not be limited to these embodiments shown herein, but rather will conform to the broadest scope consistent with the principles and novel features claimed herein.

Claims

1. A thin film lithium niobate electro-optic modulator, characterized in that: include: A chip body, the chip body comprising: a substrate layer, a lithium niobate waveguide structure, an electro-optical control electrode and a magnetic control structure located on the substrate layer; The lithium niobate waveguide structure comprises: an optical signal input section, an electro-optical modulation section and an optical signal output section; the electro-optical control electrodes are located on both sides of the electro-optical modulation section; Among them, the magnetic control structure is located on both sides of the optical signal input segment, and is used to generate a modulation magnetic field; after the polarization state of the optical signal transmitted in the optical signal input segment is controllably modulated based on the modulation magnetic field, the polarization state of the optical signal entering the electro-optical modulation segment matches the polarity of the corresponding lithium niobate material.

2. The thin film lithium niobate electro-optic modulator according to claim 1, characterized in that: The magnetic regulation structure comprises: a target structure layer, and a magneto-optical regulation electrode connected to the target structure layer; Wherein, the target structure layer has the following characteristics: it exhibits anisotropy under the action of a magnetic field and has a Faraday rotation effect; The magneto-optical control electrode is used to load an electrical control signal to generate a magnetic field in the target structure layer, and the magnetic field is controlled based on the modulation of the electrical control signal, thereby controlling the polarization state of the optical signal passing through the magnetic field; Wherein, the target structure layer is a single-layer structure or a multi-layer structure; The magnetic material or structure used in the target structure layer includes one or more of the following: Yttrium Iron Garnet YIG, Bismuth substituted yttrium iron garnet BIG, Europium oxide EuO, Gadolinium Gallium Garnet GGG, Manganese zinc ferrite, Ultra-thin ferromagnetic metal multilayer film structure with a thickness of less than 10 nanometers, Magnetic topological insulators, Magnetoelectric composite structure, Two-dimensional magnetic materials, Perovskite oxides.

3. The thin film lithium niobate electro-optic modulator according to claim 2, characterized in that: The target structure layer contains magneto-optical material, and the rotation angle of the linearly polarized light after passing through the target structure layer is affected by the following factors: the gyromagnetic properties of the magneto-optical material, the distance the light signal passes through the material layer corresponding to the magneto-optical material, the magnetic field direction and the magnetic field strength.

4. The thin film lithium niobate electro-optic modulator according to claim 1, characterized in that: The base layer includes one of the following structures: A silicon-on-insulator (SOI) substrate comprises: a silicon substrate, a lower cladding layer located on the silicon substrate; or The first type of lithium niobate on insulator LNOI substrate comprises: a silicon substrate, a lower cladding layer located on the silicon substrate, and a lithium niobate layer located on the lower cladding layer; or, The second type of lithium niobate on insulator (LNOI) substrate comprises: a lithium niobate substrate, a lower cladding layer located on the lithium niobate substrate, and a lithium niobate layer located on the lower cladding layer.

5. The thin film lithium niobate electro-optic modulator according to claim 1 or 4, characterized in that: The lithium niobate waveguide structure is one of the following waveguide structures: a strip waveguide structure, a ridge waveguide structure or a heterogeneous integrated waveguide structure; Wherein, the strip waveguide structure is a convex structure compared to the surface of the silicon dioxide layer or the surface of the lithium niobate layer on the top of the base layer, and the two side walls are vertical structures; The ridge waveguide structure is a convex structure compared to the surface of the silicon dioxide layer or the surface of the lithium niobate layer on the top of the base layer, and the two side walls have an inclined slope; The heterogeneous integrated waveguide structure includes: a lithium niobate thin film layer located on an SOI substrate, and a heterogeneous layer located on the lithium niobate thin film layer and having a convex structure, wherein the heterogeneous layer and the lithium niobate thin film layer form a heterojunction, and the refractive index corresponding to the material of the heterogeneous layer is equal to or higher than the refractive index of the lithium niobate thin film layer.

6. The thin film lithium niobate electro-optic modulator according to claim 1, characterized in that: A target cladding layer is also provided between the base layer and the magnetic control structure, and the target cladding layer is coated on the side wall and the top of the lithium niobate waveguide structure. The target cladding layer is used as a protective layer of the lithium niobate waveguide structure in the process of manufacturing the magnetic control structure, and in the thin-film lithium niobate electro-optic modulator, as a cladding waveguide located outside the lithium niobate waveguide structure, to first couple the optical signal and couple and transmit it to the lithium niobate waveguide structure; The target coating layer is a single-layer structure or a multi-layer structure, and the material of the target coating layer is one or more of the following: silicon dioxide, silicon nitride, silicon oxynitride, SU-8 polymer, magnesium oxide, tantalum oxide, aluminum oxide, and titanium oxide.

7. A control method for a thin-film lithium niobate electro-optic modulator according to any one of claims 1 to 6, characterized in that: include: Based on the control of the magnetic control structure, a modulated magnetic field is generated; Based on the modulation magnetic field, the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated so that the polarization state of the optical signal entering the electro-optical modulation section matches the polarity of the corresponding lithium niobate material; In the electro-optic modulation section, based on the input control of the electro-optical control electrode, the refractive index of the lithium niobate waveguide structure is controllably controlled and the phase, intensity or polarization state of the optical signal passing through is affected to achieve electro-optical modulation.

8. A method for manufacturing a thin film lithium niobate electro-optic modulator, characterized in that: include: Prepare the substrate; Based on the thin film preparation and patterning process, a lithium niobate waveguide structure, an electro-optical control electrode and a magnetic control structure are manufactured on the substrate; The lithium niobate waveguide structure comprises: an optical signal input section, an electro-optical modulation section and an optical signal output section; the electro-optical control electrodes are located on both sides of the electro-optical modulation section; the magnetic control structure is located on both sides of the optical signal input section, and is used to generate a modulation magnetic field; based on the modulation magnetic field, the polarization state of the optical signal transmitted in the optical signal input section is controllably modulated, so that the polarization state of the optical signal entering the electro-optical modulation section matches the polarity of the corresponding lithium niobate material.

9. The manufacturing method according to claim 8, characterized in that: The substrate comprises one of the following structures: a silicon-on-insulator SOI substrate, a first type of LNOI substrate comprising a silicon substrate, and a second type of LNOI substrate comprising a lithium niobate substrate; the first type of LNOI substrate comprises: a silicon substrate, a lower cladding layer located on the silicon substrate, and a lithium niobate layer located on the lower cladding layer; the second type of LNOI substrate comprises: a lithium niobate substrate, a lower cladding layer located on the lithium niobate substrate, and a lithium niobate layer located on the lower cladding layer; Based on the thin film preparation and patterning process, a lithium niobate waveguide structure, an electro-optical control electrode and a magnetic control structure are manufactured on the substrate, including: For the SOI substrate, a lithium niobate film is fabricated on the silicon-on-insulator SOI substrate based on an ion cutting technology, specifically comprising: using high-energy ion bombardment on a lithium niobate LN wafer to form an ion implantation layer at a preset depth; bonding the ion-implanted lithium niobate LN wafer to the SOI substrate and annealing the wafer; during the annealing process, the implanted ions expand so that the bonded structure is separated from the position of the preset depth, and the SOI substrate with the lithium niobate film is peeled off; For LNOI substrate or SOI substrate with lithium niobate film, patterned lithium niobate waveguide structure is made based on diamond cutting, chemical mechanical polishing, dry etching or photolithography process; Based on the thin film preparation process, a target cladding layer structure is formed on a substrate including a patterned lithium niobate waveguide structure; the target cladding layer structure is coated on the sidewalls and the top of the lithium niobate waveguide structure; the target cladding layer structure is used as a protective layer of the lithium niobate waveguide structure in the process of manufacturing the magnetic control structure; after the manufacturing is completed, the target cladding layer structure is used as a cladding waveguide in the thin film lithium niobate electro-optic modulator to first couple the optical signal and couple and transmit it to the lithium niobate waveguide structure; Based on thin film preparation and photolithography technology, a patterned electro-optical control electrode is manufactured on the coating layer structure; Based on thin film preparation and photolithography technology, a patterned magnetic control structure is manufactured on a substrate containing a patterned lithium niobate waveguide structure and an electro-optical control electrode; wherein, in the process of manufacturing the patterned magnetic control structure, the photoresist is used as the outermost protective layer of the completed patterned lithium niobate waveguide structure and the electro-optical control electrode, and regional exposure is adopted.

10. A functional device, characterized in that: include: The thin film lithium niobate electro-optic modulator according to any one of claims 1 to 6; The functional device is one or more of the following devices: Coherent optical modules for long-distance fiber-optic communications; Silicon-based heterogeneous integrated optical chip; Optical wireless communication equipment for 5G / 6G base station fronthaul; Silicon photonic heterogeneous integrated devices; Modulation chips for quantum communication or quantum computing; Chirp modulators in LiDAR; Intensity modulators in LiDAR; Tunable lasers; Photonic RF front-end equipment used in radar detection and electronic countermeasures; High-speed swept light source for medical optical coherence tomography; Phase sensitive modulation module for pipeline, bridge and building monitoring.

Images