Electro-optic modulator and method of manufacturing and use thereof

Abstract

The application belongs to the technical field of electro-optical devices, and particularly relates to an electro-optical modulator, a preparation method and application thereof. The electro-optical modulator provided by the application is a Mach-Zehnder electro-optical modulator, which comprises a symmetrical and parallel double-arm structure. Any single arm has the following structure: any single arm of the electro-optical modulator comprises a substrate layer, a silicon dioxide layer and a photoelectric material layer which are sequentially stacked; the surface of the photoelectric material layer is provided with a ground electrode, a signal electrode and a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is located between the ground electrode and the signal electrode, and the length of the modulation zone is 100-300 microns; the silicon nitride photonic crystal waveguide has a triangular lattice crystal hole structure; and the silicon dioxide layer has a cavity structure at a position perpendicular to the silicon nitride photonic crystal waveguide. The electro-optical modulator can solve the problems of processing loss, electro-optical bandwidth and device size limitation caused by direct etching of conventional photoelectric thin film materials.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electro-optical devices, and particularly relates to an electro-optical modulator and a preparation method and application thereof. BACKGROUND

[0002] With the vigorous development of optical communication networks, the communication capacity of modern society is growing, and higher requirements are put forward for the transmission and processing speed of communication systems. The electro-optical modulator is a key device for loading high-speed electrical signals onto optical signals and plays an important role in high-speed optical communication systems. Lithium niobate is considered to be an ideal material for making electro-optical modulators due to its large electro-optical coefficient and ultra-wide transparent window. Compared with traditional bulk electro-optical materials, thin films have higher refractive index difference contrast, lower optical loss and stronger integration compatibility.

[0003] Taking lithium niobate as an example, based on thin film lithium niobate, an electro-optical modulator with a bandwidth greater than 50 GHz has been designed. However, the thin film lithium niobate modulators reported so far cannot meet the requirements of large modulation efficiency, high bandwidth and miniaturization at the same time. SUMMARY

[0004] The purpose of the present application is to provide an electro-optical modulator and a preparation method and application thereof. The electro-optical modulator provided by the present application has the characteristics of large modulation efficiency, high bandwidth and miniaturization.

[0005] In order to achieve the purpose of the present application, the present application provides the following technical solutions:

[0006] An electro-optical modulator, which is a Mach-Zehnder electro-optical modulator; the Mach-Zehnder electro-optical modulator comprises a symmetrical and parallel double-arm structure; any single arm of the double-arm structure has the following structure:

[0007] Any single arm of the electro-optical modulator comprises a substrate layer, a silicon dioxide layer and a photoelectric material layer which are sequentially stacked;

[0008] The surface of the photoelectric material layer is provided with a ground electrode, a signal electrode and a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is located between the ground electrode and the signal electrode and is in contact with the ground electrode and the signal electrode; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; the length of the modulation region of the electro-optical modulator is 100-300 μm;

[0009] The silicon dioxide layer has a cavity structure at a position perpendicular to the silicon nitride photonic crystal waveguide.

[0010] Preferably, the material of the ground electrode and the signal electrode is independently gold or aluminum, and the thickness is independently greater than 550 nm; the distance between the ground electrode and the signal electrode is 8-10 mu m.

[0011] Preferably, the thickness of the silicon nitride photonic crystal waveguide is 400-600 nm.

[0012] The lattice constant of the crystal hole structure is 540-560 nm, and the ratio of the hole radius to the lattice constant is 0.21-0.26.

[0013] Preferably, the material of the photoelectric material layer is lithium niobate, and the thickness is 100-175 nm.

[0014] Preferably, the material of the substrate layer is silicon, quartz or lithium niobate.

[0015] Preferably, the thickness of the silicon dioxide layer is 2.7-4.7 mu m; and the thickness of the cavity structure is 500 nm-4.7 mu m.

[0016] The application also provides a preparation method of the electro-optical modulator.

[0017] The silicon nitride photonic crystal waveguide is obtained by sequentially performing silicon nitride deposition and first etching on the surface of the photoelectric material layer of the thin-film lithium niobate wafer; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; the thin-film lithium niobate wafer has a sandwich structure, and the photoelectric material layer, the intermediate silicon dioxide layer and the bottom substrate layer are sequentially arranged from top to bottom.

[0018] The ground electrode and the signal electrode are prepared on both sides of the silicon nitride photonic crystal waveguide to obtain a photoelectric material layer provided with the ground electrode, the signal electrode and the silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is adjacent to the ground electrode and the signal electrode.

[0019] The second etching is performed on the silicon dioxide layer to obtain a silicon dioxide layer with a cavity structure, so that the cavity structure is located at a position perpendicular to the silicon nitride photonic crystal waveguide, thereby obtaining the electro-optical modulator.

[0020] Preferably, the silicon nitride deposition is plasma-enhanced chemical vapor deposition.

[0021] The first etching is performed by sequentially performing electron beam exposure and inductively coupled plasma etching.

[0022] Preferably, the reagent used in the second etching is a buffered oxide etching solution.

[0023] The application further provides application of the electro-optical modulator in the technical solution or the electro-optical modulator prepared by the preparation method in the field of optical communication.

[0024] The application provides an electro-optical modulator, which is a Mach-Zehnder electro-optical modulator. The electro-optical modulator comprises a substrate layer, a silicon dioxide layer and an optoelectric material layer which are sequentially stacked; a surface of the optoelectric material layer is provided with a ground electrode, a signal electrode and a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is located between the ground electrode and the signal electrode and is in contact with the ground electrode and the signal electrode; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; a modulation region length of the electro-optical modulator is 100-300 μm; and the silicon dioxide layer has a cavity structure at a position perpendicular to the silicon nitride photonic crystal waveguide. The electro-optical modulator provided by the application uses a two-dimensional photonic crystal slow light waveguide structure, can enhance electro-optical interaction, improve modulation efficiency, thereby reducing the size of the device; due to the small size of the device, a lumped electrode structure is adopted, without the need to consider speed matching and impedance matching, and when the modulation region length is 100 μm, the electro-optical bandwidth can exceed 150 GHz. BRIEF DESCRIPTION OF DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the application or in the prior art, the following will briefly introduce the drawings needed in the embodiments. Obviously, the drawings in the following description only only some embodiments of the application, and for those skilled in the art, other drawings can be obtained from these drawings without creative labor.

[0026] Figure 1 The electro-optical modulator provided by the application is shown in the structure diagram, which comprises a ground electrode 1, a signal electrode 2, a silicon nitride photonic crystal waveguide 3, an optoelectric material layer 4, a silicon dioxide layer 5 with a cavity structure and a substrate layer 6, and L is the length of the photonic crystal modulation region.

[0027] Figure 2 The side view of the single arm of the electro-optical modulator provided by the application is shown in the drawing.

[0028] Figure 3A triangular lattice structure diagram of a silicon nitride photonic crystal waveguide of an electro-optical modulator provided by the present application;

[0029] Figure 4 An optical field transmission diagram of an electro-optical modulator provided by the present application;

[0030] Figure 5 A curve diagram of the relationship between the length of a modulation region and the capacitance of an electro-optical modulator obtained in Example 1;

[0031] Figure 6 A curve diagram of the relationship between the length of a modulation region and the electrical bandwidth of an electro-optical modulator obtained in Example 1;

[0032] Figure 7 A photonic crystal band structure diagram of an electro-optical modulator obtained in Example 1;

[0033] Figure 8 A sub-crystal group refractive index curve diagram of an electro-optical modulator obtained in Example 1;

[0034] Figure 9 An optical field transmission diagram of an electro-optical modulator obtained in Example 1;

[0035] Figure 10 A curve diagram of the phase change of slow light along a waveguide of an electro-optical modulator obtained in Example 1. DETAILED DESCRIPTION

[0036] The present application provides an electro-optical modulator, which is a Mach-Zehnder electro-optical modulator; the Mach-Zehnder electro-optical modulator comprises a symmetric and parallel double-arm structure; any single arm of the double-arm structure has the following structure:

[0037] The electro-optical modulator comprises a substrate layer, a silicon dioxide layer and a photoelectric material layer which are sequentially stacked;

[0038] The surface of the photoelectric material layer is provided with a ground electrode, a signal electrode and a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is located between the ground electrode and the signal electrode and borders the ground electrode and the signal electrode; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; the length of the modulation region of the electro-optical modulator is 100-300 μm;

[0039] The silicon dioxide layer has a cavity structure at a position perpendicular to the silicon nitride photonic crystal waveguide.

[0040] In the present application, all the raw material types are commercially available products well known to those skilled in the art, unless otherwise specified.

[0041] In the present application, the material of the ground electrode and the signal electrode is independently preferably gold or aluminum, more preferably gold; the thickness is independently preferably greater than 550 nm, more preferably 600-650 nm; the distance between the ground electrode and the signal electrode is preferably 8-10 μm, more preferably 8-9 μm.

[0042] In the present application, the thickness of the silicon nitride photonic crystal waveguide is preferably 400-600 nm, more preferably 500-600 nm; the lattice constant of the crystal hole structure is preferably 540-560 nm, more preferably 550-560 nm; the ratio of the hole radius to the lattice constant is preferably 0.21-0.26, more preferably 0.22-0.25; the length of the modulation region of the electro-optical modulator is 100-300 μm, preferably 100-200 μm, more preferably 150-200 μm.

[0043] In the present application, the material of the photoelectric material layer is preferably lithium niobate; the thickness is preferably 100-175 nm, more preferably 120-150 nm.

[0044] In the present application, the thickness of the silicon dioxide layer is preferably 2.7-4.7 μm, more preferably 3-4 μm; the thickness of the cavity structure is preferably 500 nm-4.7 μm, more preferably 500 nm-2 μm.

[0045] In the present application, the material of the substrate layer is preferably silicon, quartz or lithium niobate.

[0046] The electro-optical modulator provided by the present application uses a two-dimensional photonic crystal slow light waveguide structure, can enhance electro-optical interaction, improve modulation efficiency, thereby reducing the device size; due to the small device size, the structure of the lumped electrode is adopted, without considering the speed matching and impedance matching, when the device size is 100 μm, the electro-optical bandwidth can be more than 150 GHz. Meanwhile, the present application integrates the silicon nitride two-dimensional photonic crystal waveguide which is easy to etch and has a slightly lower refractive index than lithium niobate on the photoelectric material layer, uses etched silicon nitride to replace etched traditional electro-optical material, and can also reduce the difficulty in processing and reduce the manufacturing cost. It can be seen that the electro-optical modulator provided by the present application can solve the trade-off restriction problem of processing loss, electro-optical bandwidth and device size caused by directly etching thin film lithium niobate.

[0047] The present application also provides a preparation method of the electro-optical modulator of the above technical solution, comprising the following steps:

[0048] The surface of the photoelectric material layer of the thin film lithium niobate wafer is sequentially subjected to silicon nitride deposition and first etching to obtain a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; the thin film lithium niobate wafer has a sandwich structure, and from top to bottom, the photoelectric material layer, the intermediate silicon dioxide layer and the bottom substrate layer are sequentially arranged.

[0049] Ground electrodes and signal electrodes are respectively prepared on both sides of the silicon nitride photonic crystal waveguide to obtain a photoelectric material layer provided with the ground electrodes, the signal electrodes and the silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is in contact with the ground electrodes and the signal electrodes.

[0050] The silicon dioxide layer is subjected to second etching to obtain a silicon dioxide layer with a cavity structure, so that the cavity structure is located at a position perpendicular to the silicon nitride photonic crystal waveguide, and the electro-optical modulator is obtained.

[0051] The surface of the photoelectric material layer of the thin film lithium niobate wafer is sequentially subjected to silicon nitride deposition and first etching to obtain a silicon nitride photonic crystal waveguide.

[0052] In the present application, if the thickness of the photoelectric material layer of the thin film lithium niobate wafer is greater than the thickness range in the above technical solution, the photoelectric material layer is preferably subjected to a thinning treatment before the silicon nitride deposition; the thinning treatment is preferably chemical polishing, mechanical polishing or focused ion beam etching.

[0053] In the present application, the silicon nitride deposition is preferably plasma enhanced chemical vapor deposition; the first etching is preferably electron beam exposure and inductively coupled plasma etching; the first etching is to obtain the triangular lattice crystal hole structure of the silicon nitride photonic crystal waveguide.

[0054] After obtaining the silicon nitride photonic crystal waveguide, ground electrodes and signal electrodes are respectively prepared on both sides of the silicon nitride photonic crystal waveguide to obtain a photoelectric material layer provided with the ground electrodes, the signal electrodes and the silicon nitride photonic crystal waveguide.

[0055] In the present application, the method for preparing the ground electrodes and the signal electrodes is independently preferably electron beam evaporation deposition, electroplating or magnetron sputtering; the present application does not have any special limitation on the process of the electron beam evaporation deposition, electroplating or magnetron sputtering, and the conventional method well known to those skilled in the art can be used.

[0056] The present application subjects the intermediate silicon dioxide layer of the thin film lithium niobate wafer to second etching to obtain a silicon dioxide layer with a cavity structure, so that the cavity structure is located at a position perpendicular to the silicon nitride photonic crystal waveguide, and the electro-optical modulator is obtained.

[0057] In the present application, when the thickness of the cavity structure and the thickness of the middle silicon dioxide layer are inconsistent, the cavity structure is preferably located on the side of the thin film lithium niobate; the length and width of the cavity structure are preferably consistent with the length and width of the silicon nitride photonic crystal waveguide.

[0058] In the present application, the reagent used in the second etching is preferably a buffered oxide etching solution.

[0059] The preparation method provided by the present application can effectively solve the problem of etching lithium niobate, improve the etching sidewall angle and roughness of the waveguide, and the preparation method of the electro-optical modulator is compatible with the standard complementary metal oxide semiconductor (CMOS) process, can be mass-produced, and has lower preparation cost.

[0060] The present application also provides the application of the electro-optical modulator in the field of optical communication.

[0061] The present application does not have any special limitation on the application process of the electro-optical modulator in the field of optical communication, and the method known to those skilled in the art can be used.

[0062] In order to further illustrate the present application, the electro-optical modulator, its preparation method and application provided by the present application are described in detail below in combination with the drawings and examples, but they should not be understood as limiting the scope of protection of the present application.

[0063] The structure diagram of the electro-optical modulator provided by the present application is shown in Figure 1 , and the side view of the single arm is shown in Figure 2 , wherein, it includes a ground electrode 1, a signal electrode 2, a silicon nitride photonic crystal waveguide 3, a photoelectric material layer 4, a silicon dioxide layer 5 with a cavity structure and a substrate layer 6, and L is the length of the photonic crystal modulation area.

[0064] The triangular lattice structure diagram of the silicon nitride photonic crystal waveguide of the electro-optical modulator provided by the present application is shown in Figure 3 , wherein, r is the hole radius, and a is the lattice constant.

[0065] The optical field transmission diagram of the electro-optical modulator provided by the present application is shown in Figure 4 , wherein, the arrow represents the vector direction of the electric field. Figure 4It can be seen that, because the refractive index of silicon nitride is about 2 and the refractive index of lithium niobate is about 2.2 near the working wavelength of 1550 nm, the difference between the two refractive indexes is small. When light is transmitted in the structure, part of the light is distributed in lithium niobate, and because the photonic crystal waveguide of the silicon nitride layer has a slow light effect, the corresponding slow light mode is transmitted in lithium niobate at the same time, thereby generating a photonic crystal electro-optic modulation effect of lithium niobate. The photonic crystal waveguide is a slow light waveguide, which can further enhance the electro-optic effect, and the enhancement factor is:

[0066]

[0067] wherein is the group velocity of lithium niobate material (m / s), and is the group velocity of the photonic crystal structure (m / s).

[0068] Because the design size L of the embodiment is 100-300 μm, which is smaller than the terahertz wavelength, a lumped electrode structure is used for the electrode. The electrical bandwidth is defined as the load resistance R and the capacitance C0:

[0069]

[0070] Embodiment 1

[0071] A standard thin-film lithium niobate wafer is used, which is a sandwich structure: from top to bottom, the top layer is thin-film lithium niobate, the middle layer is silicon dioxide, and the bottom layer is a silicon substrate;

[0072] A silicon nitride film is deposited on the photoelectric material layer (thin-film lithium niobate surface) of the above lithium niobate film by PECVD (deposition temperature is usually between 0-400 ℃), and then the pattern is transferred to the SiN layer by electron beam lithography (EBL) (accelerating voltage is usually between 25-100 kV) and inductively coupled plasma (ICP) (etching working pressure is less than 50 mTorr), to obtain a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure;

[0073] Ground electrodes and signal electrodes are prepared on both sides of the silicon nitride photonic crystal waveguide by electron beam evaporation deposition, to obtain a photoelectric material layer provided with ground electrodes, signal electrodes and a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is adjacent to the ground electrodes and the signal electrodes;

[0074] The middle silicon dioxide layer in the thin film lithium niobate wafer is etched by using a buffered oxide etching solution (BOE) to obtain a silicon dioxide layer with a cavity structure, and the cavity structure is located at a position perpendicular to the silicon nitride photonic crystal waveguide to obtain the electro-optical modulator. In the embodiment, the PECVD deposition, electron beam lithography (EBL), inductively coupled plasma (ICP), and electron beam evaporation deposition steps are not particularly limited except for the above specified conditions.

[0075] The dimensions of the various structural layers of the electro-optical modulator obtained in the embodiment are shown in Table 1:

[0076] Table 1: Dimension data of the various structural layers of the electro-optical modulator obtained in Embodiment 1

[0077] Parameter H gold ]] Gap P [R air ]] H LN ]]> Value 150 μm 8 μm 560 nm 140 nm 150 nm Parameter H SiN ]] H SiO2 ]]> H sub ]]> L H aircavity <!-- 5 -->]]> Value 550 nm 2.7 μm 500 μm 100 μm 500 nm

[0078] wherein H gold is the height of the electrode, Gap is the electrode spacing, P is the photonic crystal period, R air is the photonic crystal hole radius, H LN is the thickness of the lithium niobate thin film, H SiN is the thickness of the silicon nitride thin film, H SiO2 is the thickness of the silicon dioxide layer, H sub is the thickness of the substrate, L is the modulation region length, H aircavity is the cavity height in the silicon dioxide thin film.

[0079] An electrical simulation experiment was performed on the electro-optical modulator obtained in the embodiment, and the obtained variation curve of the modulation region length and the capacitance is shown in Figure 5 , and the variation curve of the modulation region length and the electrical bandwidth is shown in Figure 6 . As can be seen from Figure 5 and Figure 6 , when the electrode spacing is 8 μm, the capacitance increases with the increase of the modulation region length, and when the modulation region length L is 100 μm, the capacitance C0 is 3.73 fF; when L is 100 μm, the electrical bandwidth is 858.3 GHz.

[0080] The lithium niobate thin film is located below the photonic crystal waveguide, and if the electro-optical overlap integral is to be increased, the thickness of the lithium niobate thin film needs to be reasonably designed. If the thickness of LN is small, the electro-optical overlap integral will decrease, thereby reducing the modulation efficiency; if the thickness of LN is thick enough, the leakage rate will be too high, resulting in a decrease in the binding of the photonic crystal plate to light and a decrease in the transmittance. In the embodiment, the thickness of the lithium niobate thin film is 150 nm, and the photonic crystal band structure is shown in Figure 7 . As can be seen from Figure 7 , when the wave vector moves from the light cone region to the boundary of the Brillouin zone, the energy band will gradually become flat, at which time the group velocity v g of the slow light mode approaches 0, which also indicates that the group velocity dispersion is divergent at the boundary.

[0081] The group refractive index curve of the sub-crystal of the electro-optical modulator obtained in the embodiment is shown in Figure 8 It can be seen from Figure 8 that the refractive index curve is flat near the working wavelength of 1550 nm, which represents that the device has better performance at this time. According to the curve, the group refractive index is calculated to be 8.85.

[0082] The simulated optical field transmission diagram of the electro-optical modulator obtained in the embodiment is shown in Figure 9 It can be seen from Figure 9 that the slow light mode formed under the structure is stable.

[0083] In the simulation, the electric field is added, and the voltage is changed, and the phase change curve of the slow light along the waveguide transmission is shown in Figure 10 It can be seen from Figure 10 that the modulation efficiency is estimated to be 0.25 cm. When the length of the modulation region is 100 μm, the optical bandwidth is calculated to be 169 GHz, and since the electrical bandwidth is much larger than the optical bandwidth, the electro-optical bandwidth depends on the optical bandwidth, which is 169 GHz.

[0084] Embodiment 2

[0085] The electro-optical modulator is prepared according to the preparation method provided in Embodiment 1. The size of each structural layer of the electro-optical modulator obtained in the embodiment is shown in Table 2:

[0086] Table 2 Size data of each structural layer of the electro-optical modulator obtained in Embodiment 2

[0087] Parameter H gold ]]> Gap P [R air ]]> H LN ]]> Value 150 μm 8 μm 560 nm 140 nm 100 nm Parameter H SiN ]]> H SiO2 ]]> H sub ]]> L H aircavity ]]> Value 550 nm 2.7 μm 500 μm 150 μm 500 nm

[0088] In the electro-optical modulator obtained in the embodiment, the photonic crystal group refractive index is 8.15, the modulation efficiency is 0.45 V·cm, and when the length L of the modulation region is 150 μm, the electro-optical bandwidth is calculated to be 120 GHz.

[0089] Although the above embodiment has made a detailed description of the present application, it is only a part of the embodiments of the present application, but not all the embodiments, and other embodiments can be obtained according to the embodiment without creativity, which all belong to the protection scope of the present application.

Claims

1. An electro-optic modulator, characterized by The electro-optical modulator is a Mach-Zehnder electro-optical modulator; the Mach-Zehnder electro-optical modulator comprises a symmetrical and parallel double-arm structure; any single arm of the double-arm structure has the following structure: Any single arm of the electro-optical modulator comprises a substrate layer, a silicon dioxide layer and a photoelectric material layer arranged in sequence; the material of the photoelectric material layer is lithium niobate; The surface of the photoelectric material layer is provided with a ground electrode, a signal electrode and a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide is located between the ground electrode and the signal electrode and borders the ground electrode and the signal electrode; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; the length of the modulation region of the electro-optical modulator is 100-300 μm; The silicon dioxide layer has a cavity structure at a position perpendicular to the silicon nitride photonic crystal waveguide.

2. The electro-optic modulator of claim 1, wherein, The material of the ground electrode and the signal electrode is independently gold or aluminum, and the thickness is independently greater than 550 nm; the spacing of the ground electrode and the signal electrode is 8-10 μm.

3. The electro-optic modulator of claim 1, wherein, The thickness of the silicon nitride photonic crystal waveguide is 400-600 nm; The lattice constant of the crystal hole structure is 540-560 nm, and the ratio of the hole radius to the lattice constant is 0.21-0.

26.

4. The electro-optic modulator of claim 1, wherein, The thickness of the photoelectric material layer is 100-175 nm.

5. The electro-optic modulator of claim 1, wherein, The material of the substrate layer is silicon, quartz or lithium niobate.

6. The electro-optic modulator of claim 1, wherein, The thickness of the silicon dioxide layer is 2.7-4.7 μm; the thickness of the cavity structure is 500 nm-4.7 μm.

7. A method of fabricating an electro-optic modulator as claimed in any one of claims 1 to 6, characterized in that Comprise the following steps: Depositing silicon nitride and first etching on the surface of the photoelectric material layer of a thin film lithium niobate wafer in sequence to obtain a silicon nitride photonic crystal waveguide; the silicon nitride photonic crystal waveguide has a crystal hole structure perpendicular to the substrate; the crystal hole structure is a triangular lattice crystal hole structure; the thin film lithium niobate wafer is a sandwich structure, and from top to bottom, it comprises a photoelectric material layer, an intermediate silicon dioxide layer and a bottom substrate layer; Prepared ground electrodes and signal electrodes on both sides of the silicon nitride photonic crystal waveguide to obtain a photoelectric material layer provided with the ground electrodes, the signal electrodes and the silicon nitride photonic crystal waveguide; The silicon nitride photonic crystal waveguide borders the ground electrodes and the signal electrodes; Second etching is performed on the silicon dioxide layer to obtain a silicon dioxide layer with a cavity structure, so that the cavity structure is located at a position perpendicular to the silicon nitride photonic crystal waveguide, thereby obtaining the electro-optical modulator.

8. The preparation method according to claim 7, characterized in that, The deposition of silicon nitride is plasma enhanced chemical vapor deposition; The first etching is performed by electron beam exposure and inductively coupled plasma etching in sequence.

9. The preparation method according to claim 7, characterized in that, The reagent used in the second etching is a buffered oxide etching solution.

10. The electro-optical modulator of any one of claims 1-6 or the electro-optical modulator obtained by the preparation method of any one of claims 7-9 for use in the field of optical communication.

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