Electro-optical modulator and preparation method thereof

Abstract

The invention discloses an electro-optical modulator and a preparation method thereof, and belongs to the technical field of optical sensing. The electro-optical modulator comprises a waveguide layer, a mixed electrode layer, a substrate, a buffer layer, an electro-optical material layer and a protective layer, the substrate, the buffer layer, the electro-optical material layer and the protective layer are sequentially stacked, and the waveguide layer is arranged on the surface of the side, away from the buffer layer, of the electro-optical material layer and embedded in the protective layer; the mixed electrode layer comprises a first electrode layer and a second electrode layer which are stacked; the first electrode layer is arranged in the electro-optical material layer in a penetrating manner; the second electrode layer is arranged on the surface of one side, deviating from the buffer layer, of the electro-optical material layer and is embedded in the protective layer; or the second electrode layer is arranged on the surface of one side, facing the buffer layer, of the electro-optical material layer and is embedded in the buffer layer; the hardness of the first electrode layer is greater than that of the electro-optical material layer. According to the invention, the structure of the mixed electrode layer is adopted, and room-temperature bonding thinning and waveguide loading are combined, so that the high-performance electro-optical modulator is prepared at low cost.

Description

Technical Field

[0001] This application relates to an electro-optic modulator and its fabrication method, belonging to the field of optical sensing technology. Background Technology

[0002] Electro-optic modulators are key devices that modulate optical signals based on the linear electro-optic effect. Their development began with the application of lithium niobate crystals in the 1960s and, with the rise of fiber optic communication, became a core component of high-speed optical networks. Currently, mainstream modulators include material platforms such as lithium niobate, silicon-based modulators, and indium phosphide modulators. Among them, lithium niobate modulators dominate the long-distance backbone network market due to their advantages such as high bandwidth (>100GHz) and low loss, while silicon-based modulators are widely used in short-distance data center communications due to their CMOS process compatibility.

[0003] Currently, the mainstream manufacturing technology for thin-film lithium niobate wafers is Smart-Cut technology, an advanced single-crystal thin-film fabrication technique. First, a nanoscale defect layer is formed beneath the surface of the lithium niobate wafer through high-energy helium ion implantation. Then, precise thermal processing creates a microbubble layer in the implanted area. Finally, the ultrathin single-crystal lithium niobate layer (thickness controllable from 300nm to 1μm ± 10nm) is transferred to a silicon or silicon dioxide substrate through wafer bonding and mechanical lift-off. Submicron-scale waveguide structures are then fabricated on the thin-film lithium niobate wafer using nanolithography. However, thin-film lithium niobate wafers fabricated using Smart-Cut technology still face multiple challenges, such as defects caused by ion implantation, rough lift-off surfaces, warping or cracking caused by interfacial stress, and increased production costs due to capacity limitations. Furthermore, etching the lithium niobate thin-film waveguide using nanolithography easily leads to sidewall roughness and dimensional deviations, resulting in significant optical losses. Summary of the Invention

[0004] To address the challenges of achieving high yield, low cost, and high performance in existing electro-optic modulator technologies, this application proposes a structural design and fabrication technology for an electro-optic modulator. Based on a hybrid under-electrode structure, a thin-film electro-optic modulator is fabricated using a room-temperature bonding thinning process and a loaded waveguide.

[0005] The technical solution adopted in this application is as follows:

[0006] According to a first aspect of this application, an electro-optic modulator is provided, comprising a substrate, a buffer layer, an electro-optic material layer, a waveguide layer, a hybrid electrode layer, and a protective layer;

[0007] The substrate, the buffer layer, the electro-optic material layer, and the protective layer are stacked sequentially.

[0008] The waveguide layer is disposed on the surface of the electro-optic material layer opposite to the buffer layer and is embedded in the protective layer;

[0009] The hybrid electrode layer includes a first electrode layer and a second electrode layer stacked together.

[0010] The first electrode layer is disposed throughout the electro-optic material layer;

[0011] The second electrode layer is disposed on the side surface of the electro-optic material layer facing away from the buffer layer and is embedded in the protective layer; or, the second electrode layer is disposed on the side surface of the electro-optic material layer facing the buffer layer and is embedded in the buffer layer.

[0012] The hardness of the first electrode layer is greater than the hardness of the electro-optic material layer.

[0013] Optionally, the width of the second electrode layer along the length direction of the hybrid electrode layer is greater than the width of the first electrode layer.

[0014] And / or, the thickness of the second electrode layer is greater than the thickness of the first electrode layer.

[0015] Optionally, the absolute difference between the refractive index of the waveguide layer and the refractive index of the electro-optic material layer is less than or equal to 0.4.

[0016] Optionally, the hybrid electrode layer and the waveguide layer do not overlap in their orthogonal projections onto the electro-optic material layer.

[0017] Optionally, the waveguide layer includes an input waveguide, a beam splitter, a modulated straight waveguide, a beam combiner, and an output waveguide connected in sequence.

[0018] Optionally, the modulated straight waveguide includes a first modulated straight waveguide and a second modulated straight waveguide;

[0019] The hybrid electrode layer includes a first traveling wave ground electrode, a traveling wave signal electrode, and a second traveling wave ground electrode;

[0020] The first traveling wave ground electrode, the first modulation straight waveguide, the traveling wave signal electrode, the second modulation straight waveguide, and the second traveling wave ground electrode are arranged in parallel in sequence, and their orthogonal projections on the electro-optic material layer are equally spaced.

[0021] Optionally, along the length direction of the hybrid electrode layer, the first electrode layer and the second electrode layer in the traveling wave signal electrode are centered and aligned with the orthogonal projections onto the electro-optic material layer.

[0022] Optionally, along the length of the hybrid electrode layer, the orthographic projections of the first electrode layer and the second electrode layer of the first traveling wave ground electrode and the second traveling wave ground electrode onto the electro-optic material layer are aligned on the side away from the traveling wave signal electrode. Optionally, the buffer layer is made of a resin adhesive material.

[0023] According to a second aspect of this application, a method for fabricating the above-mentioned electro-optic modulator is provided, comprising:

[0024] An electro-optic material substrate is provided, and a groove is formed on the electro-optic material substrate;

[0025] A metal material is deposited on the electro-optic material substrate to fill the groove, and the portion of the metal material outside the groove is removed to form the first electrode layer on the electro-optic material substrate;

[0026] The surface of the electro-optic material substrate facing the first electrode layer is bonded to the substrate through the buffer layer;

[0027] The electro-optic material layer is formed by thinning the surface of the electro-optic material substrate away from the first electrode layer until the first electrode layer is exposed.

[0028] The waveguide layer is fabricated on the surface of the electro-optic material layer opposite to the buffer layer;

[0029] A second electrode layer is prepared on the surface of the electro-optic material layer opposite to the buffer layer to cover the first electrode layer and form the hybrid electrode layer;

[0030] The protective layer is prepared on the surface of the electro-optic material layer, and the second electrode layer and the waveguide layer are embedded in the protective layer.

[0031] According to a third aspect of this application, another method for fabricating the above-mentioned electro-optic modulator is provided, comprising:

[0032] An electro-optic material substrate is provided, and a groove is formed on the electro-optic material substrate;

[0033] A metal material is deposited on the electro-optic material substrate to fill the groove, and the portion of the metal material outside the groove is removed to form the first electrode layer on the electro-optic material substrate;

[0034] A second electrode layer is fabricated on the electro-optic material substrate to cover the first electrode layer and form the hybrid electrode layer;

[0035] The surface of the electro-optic material substrate facing the first electrode layer is bonded to the substrate through the buffer layer, and the second electrode layer is embedded in the buffer layer;

[0036] The electro-optic material layer is formed by thinning the surface of the electro-optic material substrate away from the first electrode layer until the first electrode layer is exposed.

[0037] The waveguide layer is fabricated on the surface of the electro-optic material layer opposite to the buffer layer;

[0038] The protective layer is prepared on the surface of the electro-optic material layer, and the waveguide layer is embedded in the protective layer.

[0039] The beneficial effects of this application include:

[0040] (1) The electro-optic modulator provided in this application innovatively adopts a hybrid under-electrode structure, combining room-temperature bonding and thinning technology. The lower layer of the hybrid electrode uses a high-hardness chromium material, which is embedded in the electro-optic material as a support for the film thickness. Thinning automatically stops when the chromium material is reached. This method avoids problems such as defects caused by sub-implantation and warping or cracking caused by interface stress, while enabling the thickness of the electro-optic material to reach the sub-micron level through room-temperature thinning. This reduces process costs and requirements, and provides a new approach for achieving high-performance thin-film electro-optic modulators. Under room-temperature bonding and thinning conditions, it also provides more combinations of stacked layer materials, offering more choices for high-performance electro-optic modulators.

[0041] (2) The electro-optic modulator provided in this application innovatively adopts a hybrid under-electrode structure, wherein the lower part of the hybrid electrode is made of chromium material and the upper part of the hybrid electrode is made of gold material. This hybrid material electrode can simultaneously take advantage of the advantages of both materials and complement their disadvantages. Chromium material provides excellent adhesion, ensuring that the electrode and the electro-optic material are tightly bonded and avoiding peeling, effectively solving the problem of poor adhesion of gold material. At the same time, gold has advantages such as low resistivity, oxidation resistance, and low optical loss. Depositing gold material on the surface of chromium material effectively solves the problem of easy oxidation of chromium material, and makes the thickness and width of gold material greater than that of chromium material, increasing the distance between chromium material and waveguide structure, reducing the impact of high resistance and high optical loss of chromium material on the high-frequency signal loss and bandwidth of modulator. This hybrid electrode structure balances the cost and performance of modulator while ensuring process stability.

[0042] (3) The electro-optic modulator provided in this application uses a material with a refractive index close to that of the electro-optic material as the waveguide layer, which avoids the significant optical loss caused by sidewall roughness and dimensional deviation when directly etching the electro-optic material. At the same time, the waveguide layer with a refractive index close to that of the electro-optic material can effectively guide the optical mode field, reduce the absorption loss of the transmitted light by the hybrid electrode structure, and improve the high-frequency performance of the modulator. Attached Figure Description

[0043] Figure 1 This application provides a three-dimensional structural schematic diagram of an electro-optic modulator;

[0044] Figure 2 for Figure 1 Top view of the electro-optic modulator;

[0045] Figure 3A flowchart of a method for fabricating an electro-optic modulator provided in this application;

[0046] Figure 4 for Figure 3 A schematic diagram of the device structure corresponding to step S1 in the diagram;

[0047] Figure 5 for Figure 3 A schematic diagram of the device structure corresponding to step S2 in the diagram;

[0048] Figure 6 for Figure 3 A schematic diagram of the device structure corresponding to step S3 in the process;

[0049] Figure 7 for Figure 3 A schematic diagram of the device structure corresponding to step S4 in the process;

[0050] Figure 8 for Figure 3 A schematic diagram of the device structure corresponding to step S5 in the process;

[0051] Figure 9 for Figure 3 A schematic diagram of the device structure corresponding to step S6 in the process;

[0052] Figure 10 for Figure 3 A schematic diagram of the device structure corresponding to step S7 in the diagram;

[0053] Figure 11 A flowchart illustrating another method for fabricating an electro-optic modulator provided in this application;

[0054] Figure 12 for Figure 11 A schematic diagram of the device structure corresponding to step S1 in the diagram;

[0055] Figure 13 for Figure 11 A schematic diagram of the device structure corresponding to step S2 in the diagram;

[0056] Figure 14 for Figure 11 A schematic diagram of the device structure corresponding to step S3 in the process;

[0057] Figure 15 for Figure 11 A schematic diagram of the device structure corresponding to step S4 in the process;

[0058] Figure 16 for Figure 11 A schematic diagram of the device structure corresponding to step S5 in the process;

[0059] Figure 17 for Figure 11 A schematic diagram of the device structure corresponding to step S6 in the process;

[0060] Figure 18 for Figure 11 A schematic diagram of the device structure corresponding to step S7 in the diagram;

[0061] Figure 19 This is a frequency-S21 transmission response curve of the electro-optic modulator in Embodiment 1 of this application;

[0062] Figure 20 This is a frequency-S21 transmission response curve of the electro-optic modulator in Embodiment 3 of this application;

[0063] Figure 21 This is a top view of the electro-optic modulator with a T-shaped electrode structure in Embodiment 5 of this application;

[0064] Figure 22 This is a frequency-S21 transmission response curve of the electro-optic modulator in Embodiment 5 of this application.

[0065] Attached Figure Labels

[0066] 1. Substrate; 2. Buffer layer; 3. Electro-optic material layer; 30. Electro-optic material substrate;

[0067] 4. Waveguide layer; 41. Input waveguide; 42. Beam splitter; 43. Modulated straight waveguide; 43a. First modulated straight waveguide; 43b. Second modulated straight waveguide; 44. Beam combiner; 45. Output waveguide;

[0068] 5. Hybrid electrode layer; 51. First electrode layer; 52. Second electrode layer;

[0069] 5a. First traveling wave ground electrode; 5b. Traveling wave signal electrode; 5c. Second traveling wave ground electrode;

[0070] 51a, First traveling wave ground electrode I; 51b, Traveling wave signal electrode I; 51c, Second traveling wave ground electrode I; 52a, First traveling wave ground electrode II; 52b, Traveling wave signal electrode II; 52c, Second traveling wave ground electrode II;

[0071] 6. Protective layer. Detailed Implementation

[0072] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0073] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0074] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0075] This application proposes an electro-optic modulator and its fabrication method. It adopts a hybrid under-electrode structure, combines room temperature bonding and thinning process to fabricate thin-film electro-optic modulator, and uses a loaded waveguide to achieve low-cost fabrication of high-performance electro-optic modulator.

[0076] According to one embodiment of this application, an electro-optic modulator includes a substrate, a buffer layer, an electro-optic material layer, a waveguide layer, a hybrid electrode layer, and a protective layer.

[0077] The substrate, the buffer layer, the electro-optic material layer, and the protective layer are stacked sequentially.

[0078] The waveguide layer is disposed on the surface of the electro-optic material layer opposite to the buffer layer and is embedded in the protective layer;

[0079] The hybrid electrode layer includes a first electrode layer and a second electrode layer stacked together.

[0080] The first electrode layer is disposed throughout the electro-optic material layer;

[0081] The second electrode layer is disposed on the side surface of the electro-optic material layer facing away from the buffer layer and is embedded in the protective layer; or, the second electrode layer is disposed on the side surface of the electro-optic material layer facing the buffer layer and is embedded in the buffer layer.

[0082] The hardness of the first electrode layer is greater than the hardness of the electro-optic material layer.

[0083] In one embodiment, the material of the electro-optic material layer is selected from lithium niobate and / or lithium tantalate.

[0084] In one embodiment, the thickness of the electro-optic material layer ranges from 0.2 μm to 1 μm, preferably from 0.2 μm to 0.6 μm.

[0085] In one embodiment, the width of the second electrode layer along the length direction of the hybrid electrode layer is greater than the width of the first electrode layer.

[0086] In one embodiment, the width of the second electrode layer along the length direction of the hybrid electrode layer is twice the width of the first electrode layer.

[0087] In one embodiment, along the length of the hybrid electrode layer, the first electrode layer and the second electrode layer are centered or aligned to one side of the orthogonal projection onto the electro-optic material layer.

[0088] And / or, the thickness of the second electrode layer is greater than the thickness of the first electrode layer. The thickness and width of the second electrode layer are greater than the thickness and width of the first electrode layer, which aims to increase the distance between the first electrode layer and the waveguide structure, reduce the impact of the high resistance and high optical loss of the first electrode layer on the high-frequency signal loss and bandwidth of the modulator. This hybrid electrode structure balances the cost and performance of the modulator while ensuring process stability.

[0089] In one embodiment, the thickness of the first electrode layer is 0.2 μm to 1 μm, preferably 0.2 μm to 0.6 μm.

[0090] In one embodiment, the thickness of the first electrode layer is consistent with the thickness of the electro-optic material layer.

[0091] In one embodiment, the thickness of the second electrode layer is 0.4 μm to 2 μm, preferably 0.6 μm to 1.2 μm.

[0092] The materials of the first electrode layer and the second electrode layer can be selected by those skilled in the art according to the device and processing requirements.

[0093] In one embodiment, the first electrode layer is preferably made of chromium and / or titanium. Chromium has high hardness, which allows it to act as a self-stopping layer during the thinning process. At the same time, chromium provides excellent adhesion, ensuring a tight bond between the electrode and the electro-optic material and preventing peeling, effectively solving the problem of poor adhesion of gold materials. When the first electrode layer is made of titanium, the same effect can be achieved.

[0094] In one embodiment, the material of the second electrode layer is preferably selected from at least one of gold, silver, and aluminum. Gold has advantages such as low resistivity, oxidation resistance, and low optical loss, which can effectively solve the problem of easy oxidation of chromium materials. To reduce costs, the material of the second electrode layer can also be selected from silver or aluminum. Silver has better electrical properties than gold, but silver material has relatively insufficient stability, and aluminum material has relatively high optical loss, both of which will affect the performance of the modulator.

[0095] In one embodiment, the absolute difference between the refractive index of the waveguide layer and the refractive index of the electro-optic material layer is less than or equal to 0.4. The waveguide layer is made of a material with a refractive index similar to that of the electro-optic material layer, such as silicon nitride, tantalum oxide, or titanium oxide. Using a material with a similar refractive index aims to replace the method of directly etching the electro-optic material, avoiding significant optical losses caused by sidewall roughness and dimensional deviations during direct etching. The waveguide layer can also be referred to as a waveguide layer.

[0096] In one embodiment, the refractive index of the waveguide layer is 1.9 to 2.4.

[0097] In one embodiment, the hybrid electrode layer and the waveguide layer do not overlap in their orthogonal projections onto the electro-optic material layer.

[0098] In one embodiment, the waveguide layer includes an input waveguide, a beam splitter, a modulated straight waveguide, a beam combiner, and an output waveguide connected in sequence.

[0099] In one embodiment, the input waveguide and the output waveguide are conical waveguide structures.

[0100] In one embodiment, the beam splitter and beam combiner are multimode interference coupler structures.

[0101] In one embodiment, the length of the modulated straight waveguide is 0.5cm to 2cm, and the width of the modulated straight waveguide is 2μm.

[0102] In one embodiment, the thickness of the waveguide layer is 0.2 μm to 1 μm, preferably 0.2 μm to 0.6 μm.

[0103] In one embodiment, the thickness of the waveguide layer is the same as the thickness of the electro-optic material layer.

[0104] In one embodiment, the modulated straight waveguide includes a first modulated straight waveguide and a second modulated straight waveguide;

[0105] The hybrid electrode layer includes a first traveling wave ground electrode, a traveling wave signal electrode, and a second traveling wave ground electrode;

[0106] The first traveling wave ground electrode, the first modulation straight waveguide, the traveling wave signal electrode, the second modulation straight waveguide, and the second traveling wave ground electrode are arranged in parallel in sequence, and their orthogonal projections on the electro-optic material layer are equally spaced.

[0107] In one embodiment, the distance between the traveling wave signal electrode and the first traveling wave ground electrode and the second traveling wave ground electrode on the electro-optic material layer is 6μm to 10μm.

[0108] In one embodiment, the widths of the first traveling wave grounding electrode and the second traveling wave grounding electrode are 50 μm to 200 μm.

[0109] In one embodiment, the lengths of the first traveling wave grounding electrode and the second traveling wave grounding electrode are 0.5 cm to 2 cm.

[0110] In one embodiment, the width of the traveling wave signal electrode is 10 μm to 50 μm.

[0111] In one embodiment, the length of the traveling wave signal electrode is 0.5cm to 2cm.

[0112] In one embodiment, the first traveling wave ground electrode, the second traveling wave ground electrode, and the traveling wave signal electrode have the same length as the modulated straight waveguide.

[0113] In one embodiment, along the length of the hybrid electrode layer, the first electrode layer and the second electrode layer of the traveling wave signal electrode are centered and aligned on the orthogonal projection of the electro-optic material layer.

[0114] In one embodiment, along the length of the hybrid electrode layer, the orthographic projections of the first electrode layer and the second electrode layer of the first traveling wave ground electrode and the second traveling wave ground electrode onto the electro-optic material layer are aligned on the side away from the traveling wave signal electrode.

[0115] In one embodiment, the buffer layer is made of a resin adhesive material.

[0116] In one embodiment, the resin adhesive is selected from at least one of epoxy acrylate, polyurethane acrylate, polyester acrylate, amino acrylate, acryloyloxy resin, methacryloyloxy resin, vinyl resin and allyl resin.

[0117] In one embodiment, the thickness of the buffer layer is 3 μm to 500 μm.

[0118] In one embodiment, the refractive index of the buffer layer is in the range of 1.3 to 1.6.

[0119] In one embodiment, the substrate includes at least one of a silicon substrate or a quartz substrate.

[0120] In one embodiment, the thickness of the protective layer ranges from 2 μm to 5 μm.

[0121] In one embodiment, the protective layer is made of the same material as the buffer layer.

[0122] According to one embodiment of this application, a method for fabricating the above-mentioned electro-optic modulator includes:

[0123] An electro-optic material substrate is provided, and a groove is formed on the electro-optic material substrate;

[0124] A metal material is deposited on the electro-optic material substrate to fill the groove, and the portion of the metal material outside the groove is removed to form the first electrode layer on the electro-optic material substrate;

[0125] The surface of the electro-optic material substrate facing the first electrode layer is bonded to the substrate through the buffer layer;

[0126] The electro-optic material layer is formed by thinning the surface of the electro-optic material substrate away from the first electrode layer until the first electrode layer is exposed.

[0127] The waveguide layer is fabricated on the surface of the electro-optic material layer opposite to the buffer layer;

[0128] A second electrode layer is prepared on the surface of the electro-optic material layer opposite to the buffer layer to cover the first electrode layer and form the hybrid electrode layer;

[0129] The protective layer is prepared on the surface of the electro-optic material layer, and the second electrode layer and the waveguide layer are embedded in the protective layer.

[0130] According to one embodiment of this application, another method for fabricating the above-mentioned electro-optic modulator includes:

[0131] An electro-optic material substrate is provided, and a groove is formed on the electro-optic material substrate;

[0132] A metal material is deposited on the electro-optic material substrate to fill the groove, and the portion of the metal material outside the groove is removed to form the first electrode layer on the electro-optic material substrate;

[0133] A second electrode layer is fabricated on the electro-optic material substrate to cover the first electrode layer and form the hybrid electrode layer;

[0134] The surface of the electro-optic material substrate facing the first electrode layer is bonded to the substrate through the buffer layer, and the second electrode layer is embedded in the buffer layer;

[0135] The electro-optic material layer is formed by thinning the surface of the electro-optic material substrate away from the first electrode layer until the first electrode layer is exposed.

[0136] The waveguide layer is fabricated on the surface of the electro-optic material layer opposite to the buffer layer;

[0137] The protective layer is prepared on the surface of the electro-optic material layer, and the waveguide layer is embedded in the protective layer.

[0138] In one embodiment, the process for preparing the groove can be a micro / nano fabrication process such as dry etching or wet etching.

[0139] In one embodiment, the process for depositing the metal material can be electron beam evaporation or magnetron sputtering.

[0140] In one embodiment, the thinning is room temperature thinning, such as ion beam thinning, chemical mechanical polishing, or mechanical thinning.

[0141] In one embodiment, the thinning process to expose the first electrode layer includes a self-stopping thinning process, that is, the hardness of the first electrode layer is greater than the hardness of the electro-optic material layer. When the grinding wheel of the thinning machine contacts the first electrode layer, the grinding wheel current parameter suddenly increases and the thinning automatically stops after reaching the set critical threshold, thereby greatly reducing the error generated in the thin film preparation process and obtaining the preset thickness.

[0142] In one embodiment, the process for fabricating the waveguide may involve forming a waveguide layer on the surface of an electro-optic material layer using deposition and photolithography techniques, such as depositing waveguide material by chemical vapor deposition or magnetron sputtering, and then forming the waveguide structure by dry etching.

[0143] In one embodiment, the process for preparing the second electrode layer may involve using a physical vapor deposition method and a stripping process to cover the surface of the first electrode layer with the second electrode layer to form the hybrid electrode layer.

[0144] In one embodiment, the protective layer can be prepared by uniformly coating a layer of resin material onto the surface of the electro-optic material layer and then curing it.

[0145] When the second electrode layer 52 is disposed on the side surface of the electro-optic material layer 3 facing away from the buffer layer 2 in the structure of the electro-optic modulator, the three-dimensional structural schematic diagram of the electro-optic modulator is as follows. Figure 1 As shown, it includes a substrate 1, a buffer layer 2, an electro-optic material layer 3, a waveguide layer 4, a hybrid electrode layer 5, and a protective layer 6;

[0146] The substrate 1, the buffer layer 2, the electro-optic material layer 3, and the protective layer 6 are stacked sequentially.

[0147] The waveguide layer 4 is disposed on the surface of the electro-optic material layer 3 on the side opposite to the buffer layer 2, and is embedded in the protective layer 6;

[0148] The hybrid electrode layer 5 includes a first electrode layer 51 and a second electrode layer 52 stacked together.

[0149] The first electrode layer 51 is disposed through the electro-optic material layer 3;

[0150] The second electrode layer 52 is disposed on the side surface of the electro-optic material layer 3 facing away from the buffer layer 2 and is embedded in the protective layer 6;

[0151] The hybrid electrode layer 5 and the waveguide layer 4 do not overlap in their orthogonal projections onto the electro-optic material layer 3;

[0152] The width of the second electrode layer 52 along the length direction of the hybrid electrode layer 5 is twice the width of the first electrode layer 51.

[0153] The thickness of the second electrode layer 52 is greater than the thickness of the first electrode layer 51.

[0154] The thickness of the first electrode layer 51 is consistent with the thickness of the electro-optic material layer 3.

[0155] The waveguide layer 4 includes an input waveguide 41, a beam splitter 42, a modulation straight waveguide 43, a beam combiner 44, and an output waveguide 45 connected in sequence.

[0156] The input waveguide 41 and the output waveguide 45 are positive conical waveguide structures.

[0157] The beam splitter 42 and beam combiner 44 are multimode interference coupler structures.

[0158] The thickness of the waveguide layer 4 is the same as the thickness of the electro-optic material layer 3.

[0159] The modulation straight waveguide 43 includes a first modulation straight waveguide 43a and a second modulation straight waveguide 43b.

[0160] The hybrid electrode layer 5 includes a first traveling wave ground electrode 5a, a traveling wave signal electrode 5b, and a second traveling wave ground electrode 5c;

[0161] The first traveling wave ground electrode 5a, the first modulation straight waveguide 43a, the traveling wave signal electrode 5b, the second modulation straight waveguide 43b, and the second traveling wave ground electrode 5c are arranged in parallel in sequence, and their orthogonal projections on the electro-optic material layer 3 are equally spaced.

[0162] The first traveling wave grounding electrode 5a, the second traveling wave grounding electrode 5c, and the traveling wave signal electrode 5b have the same length as the modulation straight waveguide 43.

[0163] Along the length of the hybrid electrode layer 5, the first electrode layer 51 of the traveling wave signal electrode is a traveling wave signal electrode I51b and the second electrode layer 52 is a traveling wave signal electrode II52b. The orthogonal projections of the traveling wave signal electrode I51b and the traveling wave signal electrode II52b on the electro-optic material layer 3 are centered and aligned.

[0164] Along the length direction of the hybrid electrode layer 5, the first electrode layer 51 of the first traveling wave ground electrode 5a is the first traveling wave ground electrode I51a, and the second electrode layer 52 is the first traveling wave ground electrode II52a. The orthogonal projections of the first traveling wave ground electrode I51a and the first traveling wave ground electrode II52a on the electro-optic material layer 3 are aligned on the side away from the traveling wave signal electrode 5b.

[0165] Along the length direction of the hybrid electrode layer 5, the first electrode layer 51 of the second traveling wave ground electrode 5c is the second traveling wave ground electrode I51c, and the second electrode layer 52 is the second traveling wave ground electrode II52c. The orthogonal projections of the second traveling wave ground electrode I51c and the second traveling wave ground electrode II52c on the electro-optic material layer 3 are aligned on the side away from the traveling wave signal electrode 5b.

[0166] A bottom view of the electro-optic modulator. Figure 2 As shown, during operation, the input light enters from the input waveguide 41, and the optical mode field transitions from a wide waveguide with low loss to a narrow waveguide. After passing through the beam splitter 42, the light is split into two beams, which enter the first modulation straight waveguide 43a and the second modulation straight waveguide 43b respectively. A modulation signal is applied to the traveling wave signal electrode 5b, and the first traveling wave ground electrode 5a and the second traveling wave ground electrode 5c are connected to the external ground terminal to modulate the light in the first modulation straight waveguide 43a and the second modulation straight waveguide 43b. The two modulated beams are combined into one beam by the beam combiner 44 and output from the output waveguide 45 to the external optical fiber.

[0167] The fabrication steps of the electro-optic modulator are as follows: Figure 3 As shown, the specific steps are as follows:

[0168] Step S1, as follows Figure 4 As shown, a cleaned electro-optic material substrate 30 is provided, and a groove is formed on the electro-optic material substrate 30;

[0169] Step S2, as follows Figure 5 As shown, a metal material is deposited on the electro-optic material substrate 30 to fill the groove, and the portion of the metal material outside the groove is removed to form the first electrode layer 51 on the electro-optic material substrate 30;

[0170] Step S3, as follows Figure 6 As shown, the surface of the electro-optic material substrate 30 facing the first electrode layer 51 is bonded to the substrate 1 through the buffer layer 2;

[0171] Step S4, as follows Figure 7 As shown, the electro-optic material layer 3 is formed by thinning the surface of the electro-optic material substrate 30 away from the first electrode layer 51 to expose the first electrode layer 51;

[0172] Step S5, as follows Figure 8 As shown, the waveguide layer 4 is fabricated on the surface of the electro-optic material layer 3 opposite to the buffer layer 2;

[0173] Step S6, as follows Figure 9 As shown, a second electrode layer 52 is prepared on the surface of the electro-optic material layer 3 opposite to the buffer layer 2 to cover the first electrode layer 51 to form the hybrid electrode layer 5;

[0174] Step S7, as follows Figure 10 As shown, the protective layer 6 is prepared on the surface of the electro-optic material layer 3, so that the second electrode layer 52 and the waveguide layer 4 are embedded in the protective layer 6.

[0175] When the second electrode layer 52 is disposed on the surface of the electro-optic material layer 3 facing the buffer layer 2 in the structure of the electro-optic modulator, the three-dimensional structure of the electro-optic modulator is similar to... Figure 1 Similar to the previous method, the only difference is that the second electrode layer 52 is disposed on the side surface of the electro-optic material layer 3 facing the buffer layer 2 and embedded in the buffer layer 2, and its working principle is the same. Figure 2 The same schematic diagram illustrates the fabrication steps of the electro-optic modulator as follows: Figure 11 As shown, the specific steps are as follows:

[0176] Step S1, as follows Figure 12 As shown, a cleaned electro-optic material substrate 30 is provided, and a groove is formed on the electro-optic material substrate 30;

[0177] Step S2, as follows Figure 13 As shown, a metal material is deposited on the electro-optic material substrate 30 to fill the groove, and the portion of the metal material outside the groove is removed to form the first electrode layer 51 on the electro-optic material substrate 30;

[0178] Step S3, as follows Figure 14 As shown, the second electrode layer 52 is prepared on the electro-optic material substrate 30 to cover the first electrode layer 51 to form the hybrid electrode layer 5;

[0179] Step S4, as follows Figure 15 As shown, the surface of the electro-optic material substrate 30 facing the first electrode layer 51 is bonded to the substrate 1 through the buffer layer 2, and the second electrode layer 52 is embedded in the buffer layer 2;

[0180] Step S5, as follows Figure 16 As shown, the electro-optic material layer 3 is formed by thinning the surface of the electro-optic material substrate 30 away from the first electrode layer 51 to expose the first electrode layer 51;

[0181] Step S6, as follows Figure 17 As shown, the waveguide layer 4 is fabricated on the surface of the electro-optic material layer 3 opposite to the buffer layer 2;

[0182] Step S7, as follows Figure 18 As shown, the protective layer 6 is prepared on the surface of the electro-optic material layer 3, and the waveguide layer 4 is embedded in the protective layer 6.

[0183] Example 1

[0184] Electro-optic modulator structure as follows Figure 10 As shown, substrate 1 is a silicon substrate; buffer layer 2 is made of epoxy acrylate resin with a thickness of 20 μm; electro-optic material layer 3 is made of lithium niobate with a thickness of 300 nm; waveguide layer 4 is made of silicon nitride with a thickness of 300 nm; first electrode layer 51 has a thickness of 300 nm, second electrode layer 52 has a thickness of 800 nm; and protective layer 6 has a thickness of 2 μm.

[0185] The traveling wave signal electrode II52b has a width of 20 μm, the first traveling wave ground electrode II52a and the second traveling wave ground electrode II52c have a width of 100 μm, the distance between the traveling wave signal electrode II52b and the first traveling wave ground electrode II52a, and the distance between the traveling wave signal electrode II52b and the second traveling wave ground electrode II52c are 6.5 μm, and the lengths of the traveling wave signal electrode II52b, the traveling wave signal electrode I51b, the first traveling wave ground electrode II52a, the first traveling wave ground electrode I51a, the second traveling wave ground electrode II52c, the second traveling wave ground electrode I51c, the first modulation straight waveguide 43a and the second modulation straight waveguide 43b are 1 cm.

[0186] The half-wave voltage length product of the electro-optic modulator provided in this embodiment is 2.0182V.cm, which means that the modulation voltage required for an electro-optic modulator with a modulation length of 1cm is 2.02V, thus exhibiting low modulation voltage performance. Figure 19 This is a frequency-S21 transmission response curve of an electro-optic modulator according to an embodiment of this application. Figure 19 As shown, the electro-optic modulator in this embodiment has a bandwidth of 62GHz and an operating frequency greater than 60GHz, thus possessing large bandwidth modulation performance.

[0187] Example 2

[0188] The fabrication method of the electro-optic modulator in Example 1 is described in reference to... Figure 3 According to the parameters set in Example 1, the preparation method includes the following steps S1 to S7:

[0189] Step S1: Clean the surface of the electro-optic material substrate 30, and use dry etching to create grooves on the electro-optic material substrate 30. The electro-optic material substrate is a lithium niobate substrate.

[0190] Step S2: A layer of chromium is deposited on the surface of the lithium niobate substrate 30 by electron beam evaporation, and excess chromium outside the groove is removed by a stripping process to form the first electrode layer 51. The thickness of the first electrode layer 51 is 300 nm.

[0191] Step S3: The side of the lithium niobate substrate 30 containing the first electrode layer 51 is bonded to the silicon substrate 1 using epoxy acrylate resin. The epoxy acrylate resin buffer layer 2 has a thickness of 20 μm.

[0192] Step S4: By mechanically thinning the lithium niobate substrate 30 to a thickness of 300 nm, using the location of the high-hardness chromium material as a self-stopping layer, an electro-optic material layer 3 is formed.

[0193] Step S5: Silicon nitride is deposited on the surface of lithium niobate electro-optic material layer 3 by plasma-enhanced chemical vapor deposition, and a waveguide structure is formed by dry etching. The thickness of silicon nitride waveguide layer 4 is 300 nm.

[0194] Step S6: A gold electrode is deposited on the chromium surface using electron beam evaporation and stripping processes to form a second electrode layer 52. The thickness of the second electrode layer 52 is 800 nm.

[0195] Step S7: A layer of epoxy acrylate resin is uniformly coated onto the surface of the lithium niobate electro-optic material layer 3 to cover the silicon nitride waveguide layer 4 and the hybrid electrode layer 5, forming a protective layer 6. The thickness of the protective layer 6 is 2 μm.

[0196] Example 3

[0197] Electro-optic modulator structure as follows Figure 18 As shown, substrate 1 is a silicon substrate; buffer layer 2 is made of epoxy acrylate resin with a thickness of 20 μm; electro-optic material layer 3 is made of lithium niobate with a thickness of 300 nm; waveguide layer 4 is made of silicon nitride with a thickness of 300 nm; first electrode layer 51 has a thickness of 300 nm, second electrode layer 52 has a thickness of 800 nm; and protective layer 6 has a thickness of 2 μm.

[0198] The traveling wave signal electrode II52b has a width of 20 μm, the first traveling wave ground electrode II52a and the second traveling wave ground electrode II52c have a width of 100 μm, the distance between the traveling wave signal electrode II52b and the first traveling wave ground electrode II52a, and the distance between the traveling wave signal electrode II52b and the second traveling wave ground electrode II52c are 6.5 μm, and the lengths of the traveling wave signal electrode II52b, the traveling wave signal electrode I51b, the first traveling wave ground electrode II52a, the first traveling wave ground electrode I51a, the second traveling wave ground electrode II52c, the second traveling wave ground electrode I51c, the first modulation straight waveguide 43a and the second modulation straight waveguide 43b are 1 cm.

[0199] The half-wave voltage length product of the electro-optic modulator provided in this embodiment is 2.0033V.cm, which means that the modulation voltage required for an electro-optic modulator with a modulation length of 1cm is 2.00V, thus exhibiting low modulation voltage performance. Figure 20 This is a frequency-S21 transmission response curve of an electro-optic modulator according to an embodiment of this application. Figure 20 As shown, the electro-optic modulator in this embodiment has a bandwidth of 60 GHz, that is, an operating frequency of 60 GHz, and has a large bandwidth modulation performance.

[0200] Example 4

[0201] Example 3: Fabrication method of the electro-optic modulator, refer to Figure 11 According to the parameters set in Example 3, the preparation method includes the following steps S1 to S7:

[0202] Step S1: Clean the surface of the electro-optic material substrate 30, and use dry etching to create grooves on the electro-optic material substrate 30. The electro-optic material substrate is a lithium niobate substrate.

[0203] Step S2: A layer of chromium is deposited on the surface of the lithium niobate substrate 30 by electron beam evaporation, and excess chromium outside the groove is removed by a stripping process to form the first electrode layer 51. The thickness of the first electrode layer 51 is 300 nm.

[0204] Step S3: A gold electrode is deposited on the chromium surface using electron beam evaporation and stripping processes to form a second electrode layer 52. The thickness of the second electrode layer 52 is 800 nm.

[0205] Step S4: The side of the lithium niobate substrate 30 containing the mixed electrode layer 5 is bonded to the silicon substrate 1 using epoxy acrylate resin. The epoxy acrylate resin buffer layer 2 has a thickness of 20 μm.

[0206] Step S5: Thin the lithium niobate substrate 30 to a thickness of 300 nm by using an ion beam to thin it, with the location of the hard chromium material as the self-stopping layer, to form the electro-optic material layer 3.

[0207] Step S6: Silicon nitride is deposited on the surface of lithium niobate electro-optic material layer 3 by plasma-enhanced chemical vapor deposition, and a waveguide structure is formed by dry etching. The thickness of silicon nitride waveguide layer 4 is 300 nm.

[0208] Step S7: A layer of epoxy acrylate resin is uniformly coated onto the surface of the lithium niobate electro-optic material layer 3 to cover the silicon nitride waveguide layer 4 and the hybrid electrode layer 5, forming a protective layer 6. The thickness of the protective layer 6 is 2 μm.

[0209] Example 5

[0210] Electro-optic modulator structure as follows Figure 10 As shown, substrate 1 is a silicon substrate; buffer layer 2 is made of epoxy acrylate resin with a thickness of 20 μm; electro-optic material layer 3 is made of lithium niobate with a thickness of 300 nm; waveguide layer 4 is made of silicon nitride with a thickness of 300 nm; first electrode layer 51 has a thickness of 300 nm, second electrode layer 52 has a thickness of 800 nm; and protective layer 6 has a thickness of 2 μm.

[0211] The second electrode layer 52 has a T-shaped electrode structure. Figure 21 This is a top view of the electro-optic modulator with a T-shaped electrode structure in Embodiment 5 of this application, as shown below. Figure 21 As shown, the T-type electrode consists of three parts: T_TOP, T_BOM, and traveling wave electrode. The period of T_TOP and T_BOM is 50μm. The width and length of T_TOP are 3μm and 45μm, respectively, and the width and length of T_BOM are 5μm and 3μm, respectively. The width of the traveling wave signal electrode is 8μm. The width of the traveling wave ground electrode is 100μm. The distance between the traveling wave signal electrode II52b and the first traveling wave ground electrode II52a, and between the traveling wave signal electrode II52b and the second traveling wave ground electrode II52c is 6μm. The lengths of the traveling wave signal electrode II52b, traveling wave signal electrode I51b, first traveling wave ground electrode II52a, first traveling wave ground electrode I51a, second traveling wave ground electrode II52c, second traveling wave ground electrode I51c, first modulation straight waveguide 43a, and second modulation straight waveguide 43b are 1cm.

[0212] The half-wave voltage length product of the electro-optic modulator provided in this embodiment is 1.8491V.cm, which means that the modulation voltage required for an electro-optic modulator with a modulation length of 1cm is 1.85V, thus exhibiting low modulation voltage performance. Figure 22 This is a frequency-S21 transmission response curve of an electro-optic modulator according to an embodiment of this application. Figure 22 As shown, the electro-optic modulator in this embodiment has a bandwidth of 101 GHz and an operating frequency greater than 100 GHz, thus possessing large bandwidth modulation performance.

[0213] This embodiment uses the same stacking structure as in Embodiment 1 and the same preparation method as in Embodiment 2. The electro-optic modulators with the same structure and preparation method as in Embodiment 3 are similar. The modulation bandwidth of the electro-optic modulator can be further improved by using a T-shaped electrode structure and optimizing the structural parameters of the hybrid electrode layer, that is, to achieve a high-performance electro-optic modulator with a 3dB bandwidth of over 100GHz.

[0214] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and all fall within the scope of the technical solution.

Claims

1. An electro-optic modulator, characterized by The substrate, the buffer layer, the electro-optical material layer, and the protective layer are sequentially stacked. The waveguide layer is arranged on the surface of the electro-optical material layer away from the buffer layer and embedded in the protective layer. The mixed electrode layer includes a first electrode layer and a second electrode layer which are stacked. The first electrode layer is arranged in the electro-optical material layer. The second electrode layer is arranged on the surface of the electro-optical material layer away from the buffer layer and embedded in the protective layer. The second electrode layer is arranged on the surface of the electro-optical material layer toward the buffer layer and embedded in the buffer layer. The hardness of the first electrode layer is greater than the hardness of the electro-optical material layer. The width of the second electrode layer is greater than the width of the first electrode layer along the length direction of the mixed electrode layer.

2. The electro-optic modulator of claim 1, wherein, The thickness of the second electrode layer is greater than the thickness of the first electrode layer. The absolute difference between the refractive index of the waveguide layer and the refractive index of the electro-optical material layer is less than or equal to 0.

4.

3. The electro-optic modulator of claim 1, wherein, The mixed electrode layer and the waveguide layer have no overlap in the orthographic projection on the electro-optical material layer.

4. The electro-optic modulator of claim 1, wherein, The waveguide layer includes an input waveguide, a beam splitter, a modulation straight waveguide, a beam combiner, and an output waveguide which are sequentially connected.

5. The electro-optic modulator of claim 1, wherein, The modulation straight waveguide includes a first modulation straight waveguide and a second modulation straight waveguide.

6. The electro-optic modulator of claim 5, wherein, The mixed electrode layer includes a first row wave ground electrode, a row wave signal electrode, and a second row wave ground electrode. The first row wave ground electrode, the first modulation straight waveguide, the row wave signal electrode, the second modulation straight waveguide, and the second row wave ground electrode are sequentially arranged in parallel and arranged at equal intervals in the orthographic projection on the electro-optical material layer. Along the length direction of the mixed electrode layer, the orthographic projection of the first electrode layer and the second electrode layer in the row wave signal electrode on the electro-optical material layer is centrally aligned.

7. The electro-optic modulator of claim 6, wherein, Along the length direction of the mixed electrode layer, the orthographic projection of the first electrode layer and the second electrode layer in the first row wave ground electrode and the second row wave ground electrode on the electro-optical material layer is aligned on the side away from the row wave signal electrode.

8. The electro-optic modulator of claim 6, wherein, The method includes:

9. A method of fabricating an electro-optic modulator as claimed in any one of claims 1 to 8, characterized in that providing an electro-optical material substrate and preparing a slot in the electro-optical material substrate; depositing a metal material on the electro-optical material substrate to fill the slot, removing the metal material part outside the slot to form the first electrode layer on the electro-optical material substrate; bonding the surface of the electro-optical material substrate away from the first electrode layer to the substrate through the buffer layer; thinning the surface of the electro-optical material substrate away from the first electrode layer to expose the first electrode layer to form the electro-optical material layer; preparing the waveguide layer on the surface of the electro-optical material layer away from the buffer layer; preparing the second electrode layer on the surface of the electro-optical material layer away from the buffer layer to cover the first electrode layer to form the mixed electrode layer; preparing the protective layer on the surface of the electro-optical material layer to embed the second electrode layer and the waveguide layer in the protective layer. The method includes:

10. A method of fabricating an electro-optic modulator as claimed in any one of claims 1 to 8, characterized in that ​ A substrate of electro-optical material is provided, and a groove is prepared in the substrate of electro-optical material; A metal material is deposited on the substrate of electro-optical material to fill the groove, and a portion of the metal material outside the groove is removed to form the first electrode layer on the substrate of electro-optical material; The second electrode layer is prepared on the substrate of electro-optical material to cover the first electrode layer to form the mixed electrode layer; The surface of the substrate of electro-optical material on the side facing the first electrode layer is bonded to the substrate through the buffer layer, and the second electrode layer is embedded in the buffer layer; The surface of the substrate of electro-optical material on the side away from the first electrode layer is thinned to expose the first electrode layer to form the electro-optical material layer; The waveguide layer is prepared on the surface of the electro-optical material layer on the side away from the buffer layer; The protective layer is prepared on the surface of the electro-optical material layer, and the waveguide layer is embedded in the protective layer.

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