High-speed electro-optical modulator based on lead zirconate titanate film and preparation method of high-speed electro-optical modulator

Abstract

The invention discloses a lead zirconate titanate film-based high-speed electro-optical modulator and a preparation method thereof, and belongs to the technical field of planar optical waveguide devices. The modulator is composed of a silicon substrate, a silicon dioxide oxide layer, discrete metal electrodes, a silicon dioxide spacer layer, an inverted ridge type lead zirconate titanate flat plate core layer and a polymer upper cladding layer from bottom to top. The silicon dioxide spacing layer forms a recess due to the spacing of the discrete electrodes, and the lead zirconate titanate material naturally forms an inverted ridge type slab waveguide, so that a light field is more effectively controlled in the lead zirconate titanate film with a large electro-optical coefficient. In addition, the electro-optical polymer is adopted as the polymer upper cladding, the electro-optical polymer has an electro-optical effect and has a larger dielectric constant, an electric field is distributed more uniformly in gaps of the discrete metal electrodes, the electric field effect on lead zirconate titanate is larger, and the electro-optical phase modulation efficiency is further improved. The manufacturing process is greatly simplified, the manufacturing difficulty of the device is reduced, and the method has the advantages of low production cost, high efficiency and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of planar optical waveguide devices, and particularly relates to a high-speed electro-optic modulator based on lead zirconate titanate thin film and a preparation method thereof. Background Art

[0002] With the rapid development of technologies such as the Internet, big data, cloud computing, and artificial intelligence, the global data traffic has increased explosively, and the demand for high-speed, efficient, and low-power optical communication systems has become increasingly urgent. As a core device in an optical communication system, an electro-optic modulator can convert an electrical signal into an optical signal, thereby realizing the efficient transmission of information, and its performance directly affects the transmission rate, bandwidth, and energy consumption of the optical communication system. In order to meet the growing technological requirements, electro-optic modulators need to continuously improve their own performance.

[0003] In order to achieve higher-performance electro-optic modulators, a variety of integrated electro-optic platforms have been reported and developed, mainly including silicon-based platforms, thin-film lithium niobate (LNOI) platforms, organic electro-optic polymer platforms, and lead zirconate titanate (PZT) platforms. Among them, the silicon-based platform has the characteristics of low propagation loss, compatibility with CMOS processes, and high thermal stability. However, the electro-optic effect of silicon is weak, so its modulation efficiency is low and its electrical bandwidth is also low, which limits its development in high-speed optical communication. LNOI is the most widely used crystalline thin-film electro-optic material at present, with a wide transparent wavelength range and good chemical and thermal stability. However, its high propagation loss, complex process, and poor compatibility with CMOS processes have hindered its development process. In contrast, organic electro-optic polymers can be prepared by spin coating, providing a flexible and scalable alternative for integrated electro-optic modulation. However, the preparation process of electro-optic polymer materials is complex and their stability is poor, resulting in easy attenuation of their electro-optic performance. Therefore, many challenges still remain in the field of electro-optic modulation.

[0004] PZT materials have a high electro-optic coefficient, which significantly improves the modulation efficiency of PZT electro-optic modulators. Therefore, they have received extensive attention and developed rapidly. However, dry etching is required in the current preparation process of PZT waveguides, which will greatly increase the process complexity and cost of the device. Summary of the Invention

[0005] In order to further improve the modulation efficiency of the electro-optic modulator and simplify the process manufacturing process, the present invention proposes a high-speed electro-optic modulator based on lead zirconate titanate thin film and a preparation method thereof.

[0006] The present invention grows a silicon dioxide oxide layer on a silicon substrate, evaporates discrete metal electrodes on the silicon dioxide oxide layer, then grows a silicon dioxide spacer layer on the surfaces of the silicon dioxide oxide layer and the discrete metal electrodes, spin-coats lead zirconate titanate on the silicon dioxide spacer layer as a waveguide core layer, and uses the shape of the electrodes themselves to form an inverted ridge waveguide without etching lead zirconate titanate, so that the optical field is confined in the waveguide core layer, significantly reducing the complexity of the process and also improving the electro-optic overlap factor of the electro-optic modulator, making full use of the advantage of the large electro-optic coefficient of lead zirconate titanate. The electro-optic modulator fabricated by this process also has advantages such as high modulation efficiency and has broad application prospects for meeting high-speed and large-capacity data transmission and other aspects. In addition, the present invention uses a polymer material with a relatively high dielectric constant and a relatively low refractive index as the polymer upper cladding of the waveguide, making full use of the advantages of easy processing of the polymer material and compatibility with semiconductor processes, giving the device important practical application value.

[0007] As shown in the Figure 1 accompanying drawings, a high-speed electro-optic modulator based on a lead zirconate titanate thin film according to the present invention comprises, from bottom to top, a silicon substrate 1, a silicon dioxide oxide layer 2 grown on the upper surface of the substrate, discrete metal electrodes 4 evaporated on both sides of the upper surface of the silicon dioxide oxide layer 2, a silicon dioxide spacer layer 3 grown on the surfaces of the silicon dioxide oxide layer 2 and the discrete metal electrodes 4, an inverted ridge lead zirconate titanate flat core layer 5 spin-coated on the silicon dioxide spacer layer 3, and a polymer upper cladding 6 spin-coated on the lead zirconate titanate flat core layer 5; the lengths a1 of the discrete metal electrodes 4, the silicon dioxide spacer layer 3, the lead zirconate titanate flat core layer 5, and the polymer upper cladding 6 are equal, being 4 - 8 mm, and the material of the polymer upper cladding 6 is a series of materials including polyimide (PI), polymethyl methacrylate (PMMA), SU-8 2002, SU-8 2005, etc.

[0008] As shown in the Figure 2 accompanying drawings (for the cross-section at the A - A' position in the Figure 1 accompanying drawings), the thickness of the silicon substrate 1 is 480 - 520 μm, the thickness of the silicon dioxide oxide layer 2 is 4 - 14 μm, the thickness of the discrete metal electrodes 4 is 0.2 - 2 μm, the thickness of the silicon dioxide spacer layer 3 is 0.1 - 0.3 μm, the thickness of the lead zirconate titanate flat core layer 5 (being the thickness of the flat region, not the thickness of the inverted ridge region formed due to the electrode shape) is 0.1 - 0.4 μm, and the thickness of the polymer upper cladding 6 is 1 - 5 μm; the two electrode structures in the discrete metal electrodes 4 are completely the same, the width b1 is 10 - 20 μm, and the distance gap between the two parts is 2 - 20 μm.

[0009] A method for preparing a high-speed electro-optic modulator based on a lead zirconate titanate thin film according to the present invention, as Figure 3 shown in the accompanying drawings, comprises the following steps:

[0010] A: Cleaning treatment of the silicon wafer substrate 1

[0011] First, clean the silicon substrate 1 with a thickness of 480 - 520 μm 2 - 4 times in sequence using acetone, methanol, and isopropyl alcohol, and dry it with nitrogen to determine that the surface of the silicon substrate 1 is clean;

[0012] B: Preparation of the silicon dioxide lower cladding

[0013] Grow the silicon dioxide lower cladding 2 by thermal oxidation method. That is, first clean the silicon substrate 1 with deionized water, then soak it in a hydrofluoric acid solution with a mass fraction of 1 - 5% for 1 - 2 min to remove the native oxide layer, and then oxidize the silicon substrate 1 without the native oxide layer in a high-purity water vapor atmosphere at 900 - 1200 °C for 1 - 6 h. After oxidation, naturally cool it to room temperature, thereby growing a silicon dioxide oxide layer 2 with a thickness of 4 - 14 μm on the surface of the silicon substrate 1;

[0014] C: Preparation of the electro-optic modulator electrode

[0015] Evaporate a gold electrode layer 7 with a thickness of 0.2 - 2 μm on the silicon dioxide lower cladding 2 by vacuum evaporation method. Then spin-coat the photoresist BP212 on the surface of the gold electrode layer 7 at a rotation speed of 1000 - 8000 revolutions per minute to make the thickness of BP212 1 - 10 μm; Bake the device with spin-coated photoresist BP212 at a temperature of 50 - 300 °C for 10 - 50 minutes, and then cool it to room temperature for mask lithography; The structure of the mask is the same as the structure of the discrete metal electrode 4 to be prepared. Expose it under ultraviolet light with a wavelength of 300 - 500 nm for 10 - 20 s to expose the photoresist in the area other than the electrode; Immerse the device in a NaOH solution with a mass concentration of 2 - 5‰ for 5 - 20 minutes to remove the exposed photoresist, then rinse it with deionized water and dry it with nitrogen, bake the device at 80 - 300 °C for 5 - 40 minutes and then cool it to room temperature; Finally, expose the whole device for 2 - 5 s, and then immerse the device in ethanol for 1 - 8 minutes to obtain the discrete metal electrode 4 with the required structure;

[0016] D: Preparation of the silicon dioxide spacer layer

[0017] The silicon dioxide spacer layer is grown by PECVD technology. First, the silicon substrate 1 obtained in step C is sequentially cleaned with deionized water and a hydrofluoric acid solution with a mass fraction of 1-5% to remove the surface oxide layer. Then, the cleaned silicon substrate 1 is placed in a PECVD device, the temperature is set to 300-400 °C, the radio frequency power supply is turned on to 100-300 W, and deposition is carried out for 10-30 minutes after generating plasma. The high-energy electrons of the plasma will excite SiH4 and O2 molecules to decompose them into active groups. After the temperature of the silicon substrate 1 drops to room temperature, nitrogen is slowly introduced into the PECVD device chamber, so as to prepare a silicon dioxide spacer layer 3 with a thickness of 0.1-0.3 μm on the surface of the silicon dioxide oxide layer 2 and the discrete metal electrodes 4;

[0018] E: Preparation of the lead zirconate titanate flat core layer

[0019] The PZT precursor solution is synthesized by the sol-gel method, and then the PZT precursor solution is spin-coated on the surface of the silicon dioxide spacer layer 3 at a rotation speed of 1000-8000 revolutions per minute, baked at 100-500 °C for 20-50 minutes and then cooled to room temperature, so as to prepare an inverted ridge-shaped lead zirconate titanate flat core layer 5 with a thickness of 0.1-0.4 μm;

[0020] F: Preparation of the polymer upper cladding

[0021] By the spin-coating process, the polymer upper cladding material is coated on the prepared lead zirconate titanate flat core layer 5 at a rotation speed of 1000-6000 revolutions per minute, baked at 100-500 °C for 20-50 minutes and then cooled to room temperature, and a polymer upper cladding 6 with a thickness of 1-5 μm is prepared, thereby preparing a high-speed electro-optic modulator based on zirconium titanate thin film.

[0022] Compared with the existing device structures and technologies, the beneficial effects of the present invention are as follows: The present invention first evaporates metal electrodes on the silicon dioxide oxide layer, and then grows a silicon dioxide spacer layer, so that the silicon dioxide spacer layer forms a depression due to the spacing of the discrete electrodes. The lead zirconate titanate material is spin-coated on the silicon dioxide spacer layer to naturally form an inverted ridge-shaped planar waveguide, so as to more effectively control the optical field in the lead zirconate titanate thin film with a large electro-optic coefficient. In addition, an electro-optic polymer is used as the polymer upper cladding. Compared with silicon dioxide, the electro-optic polymer has an electro-optic effect and a larger dielectric constant. When an external electric field is applied, the electric field is more evenly distributed in the gap between the discrete metal electrodes, and the lead zirconate titanate is also more affected by the electric field, further improving the electro-optic phase modulation efficiency. To sum up, compared with the etched lead zirconate titanate electro-optic modulator, the present invention greatly simplifies the manufacturing process flow, reduces the manufacturing difficulty of the device, and has the advantages of low production cost and high efficiency. Description of the drawings

[0023] Figure 1: Schematic diagram of the structure of a high-speed electro-optic modulator based on lead zirconate titanate thin film;

[0024] Figure 2 : Figure 1 Schematic diagram of the A-A' cross-section of the electro-optic modulator;

[0025] Figure 3 : Process flow chart for the preparation of a high-speed electro-optic modulator based on lead zirconate titanate thin film;

[0026] Figure 4 (a): Figure 1 Optical field distribution diagram of the A-A' cross-section in

[0027] Figure 4 (b): Figure 1 Electric field distribution diagram of the A-A' cross-section in

[0028] Figure 5 (a): Curve of the product of the half-wave voltage and length of the electro-optic modulator varying with the thickness of the PZT flat core layer;

[0029] Figure 5 (b): Curve of the loss of the electro-optic modulator varying with the thickness of the PZT flat core layer;

[0030] Figure 5 (c): Curve of the product of the half-wave voltage and length of the electro-optic modulator varying with the gap;

[0031] Figure 5 (d): Curve of the loss of the electro-optic modulator varying with the gap;

[0032] Figure 6 : Curve of the reflection coefficient and transmission coefficient of the electro-optic modulator varying with frequency.

[0033] As shown in the appendix Figure 1 The schematic diagram of the structure of a high-speed electro-optic modulator based on lead zirconate titanate thin film is shown. The names of each component are: silicon substrate 1, silicon dioxide oxide layer 2 deposited on the upper surface of the substrate, discrete metal electrodes 4 evaporated on both sides of the upper surface of the silicon dioxide oxide layer 2, silicon dioxide spacer layer 3 spin-coated on the upper surface of the discrete metal electrodes 4, inverted ridge-shaped lead zirconate titanate flat core layer 5 spin-coated on the silicon dioxide spacer layer 3, and polymer upper cladding 6 spin-coated on the lead zirconate titanate flat core layer 5.

[0034] As shown in the appendix Figure 2 For the cross-section of the electro-optic modulator (appendix Figure 1(Schematic diagram of the cross-section at the A-A' position) The names of each part are as follows: silicon substrate 1, silicon dioxide oxide layer 2 deposited on the upper surface of the substrate, discrete metal electrodes 4 evaporated on both sides of the upper surface of the silicon dioxide oxide layer 2, silicon dioxide spacer layer 3 spin-coated on the upper surface of the discrete metal electrodes 4, inverted ridge-shaped lead zirconate titanate planar core layer 5 spin-coated on the silicon dioxide spacer layer 3, and polymer upper cladding 6 spin-coated on the lead zirconate titanate planar core layer 5.

[0035] As Figure 3 is the process flow chart for the preparation of a high-speed electro-optic modulator based on lead zirconate titanate thin film. In the figure, 1 is the silicon substrate, 2 is the silicon dioxide oxide layer, 3 is the silicon dioxide spacer layer, 4 is the discrete metal electrode, 5 is the inverted ridge-shaped lead zirconate titanate planar waveguide, 6 is the polymer upper cladding, and 7 is the metal layer.

[0036] As Figure 4 (a) is the simulation diagram of the fundamental mode optical field distribution in the waveguide of the A-A' cross-section of the high-speed electro-optic modulator based on lead zirconate titanate thin film Figure 1 ; It can be seen from the figure that most of the optical field is distributed in the lead zirconate titanate core layer waveguide and the electro-optic silicon dioxide spacer layer. While ensuring the effective transmission of light, the overlapping area of the optical field and the electric field is increased, and the modulation efficiency is improved;

[0037] As Figure 4 (b) is the simulation diagram of the fundamental mode electric field distribution in the waveguide of the A-A' cross-section of the high-speed electro-optic modulator based on lead zirconate titanate thin film Figure 1 ; The arrows on the surface in the figure represent the electric field distribution. It can be seen that the electric field distribution is uniform, and the electric field is relatively large at the boundaries of the electrode and the lower cladding, the electrode and the silicon dioxide spacer layer, and the silicon dioxide spacer layer and lead zirconate titanate. According to Maxwell's equations, the polymer upper cladding with a relatively large relative dielectric constant at the dielectric boundary can increase the electric field strength inside the lead zirconate titanate waveguide, thereby improving the modulation efficiency.

[0038] As Figure 5 shown, are the curves of the electro-optic modulation efficiency and loss of the high-speed electro-optic modulator based on lead zirconate titanate thin film varying with the thickness of the lead zirconate titanate planar core layer and gap;

[0039] (a) is the relationship curve of the half-wave voltage-length product of the electro-optic modulator in Example 1 varying with the thickness of the lead zirconate titanate planar core layer; It can be seen that as the core layer thickness increases, the half-wave voltage-length product of the electro-optic modulator decreases, and the modulation efficiency becomes higher. When its thickness reaches about 0.4 μm, the modulation efficiency no longer increases. This is because when the thickness of lead zirconate titanate is too large, its optical field gradually extends to both sides, resulting in a smaller electro-optic overlap factor;

[0040] (b) is the relationship curve of the loss of the electro-optic modulator in Example 1 varying with the thickness of the lead zirconate titanate flat core layer; it can be seen that as the core layer thickness increases, the loss of the electro-optic modulator remains basically unchanged. Due to the presence of the silica spacer layer, the loss of the electro-optic modulator is greatly reduced, and the thickness of the lead zirconate titanate thin film basically does not affect the loss of the electro-optic modulator;

[0041] (c) is the relationship curve of the half-wave voltage-length product of the electro-optic modulator in Example 1 varying with the metal electrode spacing gap; it can be seen that as the metal electrode spacing gap increases, the half-wave voltage-length product of the electro-optic modulator increases and the modulation efficiency becomes lower;

[0042] (d) is the relationship curve of the loss of the electro-optic modulator in Example 1 varying with the metal electrode spacing gap; it can be seen that as the metal electrode spacing gap increases, the loss of the electro-optic modulator decreases.

[0043] As Figure 6 shown, it is the electro-optic modulator characteristic curve under the electrode structure of Example 1 of the high-speed electro-optic modulator based on lead zirconate titanate thin film. From the relationship curve of the transmission coefficient varying with frequency, it can be seen that the transmission coefficient is lower in the high-frequency region and higher in the low-frequency region, and the bandwidth of the device can reach 100 GHz. From the relationship curve of the reflection parameter varying with frequency, it can be seen that the reflection parameter is small, below -30 dB. Specific embodiments

[0044] Example 1

[0045] The present invention will be further described below with reference to the drawings and examples.

[0046] As shown in the Figure 1 drawings, an electro-optic phase electro-optic modulator based on lead zirconate titanate thin film according to the present invention comprises, from bottom to top, a silicon substrate 1, a silica oxide layer 2 deposited on the upper surface of the substrate, discrete metal electrodes 4 evaporated on both sides of the upper surface of the silica oxide layer 2, a silica spacer layer 3 grown on the upper surface of the discrete metal electrodes 4, an inverted ridge-shaped lead zirconate titanate flat core layer 5 spin-coated on the silica spacer layer 3, and a polymer upper cladding 6 spin-coated on the lead zirconate titanate flat core layer 5: the lengths a1 of the discrete metal electrodes 4, the silica spacer layer 3, the lead zirconate titanate flat core layer 5, and the polymer upper cladding 6 are equal to 5 mm, and the material of the polymer upper cladding 6 is a series of materials including polyimide (PI), polymethyl methacrylate (PMMA), SU-8 2002, SU-8 2005, etc. In this example, polymethyl methacrylate (PMMA) is selected as the material of the polymer upper cladding 6.

[0047] As shown in the Figure 2 drawings (for the Figure 1(Cross-section at the position A-A’), the thickness of the silicon substrate 1 is 500 μm, the thickness of the silicon dioxide oxide layer 2 is 6 μm, the thickness of the discrete metal electrode 4 is 0.8 μm, the thickness of the silicon dioxide spacer layer 3 is 0.2 μm, the thickness of the lead zirconate titanate flat core layer 5 (only the thickness of the flat plate area) is 0.3 μm, and the thickness of the polymer upper cladding 6 is 2 μm. The two parts of the electrode in the discrete metal electrode 4 are exactly the same, the width b1 is 20 μm, and the distance gap between the two parts is 5 μm.

[0048] Under the above parameter conditions, through the simulation software Comsol Multiphysics calculation, the phase modulation efficiency of this electro-optic modulator can be obtained as 1.2 V·cm, and the loss is 0.2 dB / cm. The HFSS software is used to simulate the radio frequency situation of the electro-optic modulator. Among them, the transmission parameters (S 12 and S 21 ) are larger, and the reflection parameters (S 11 and S 22 ) are smaller. The results show that in the relatively wide frequency range of 0-100 GHz, the traveling wave electrodes of this structure have smaller reflectivity and larger transmittance.

[0049] A preparation method of a high-speed electro-optic modulator based on lead zirconate titanate thin film according to the present invention is as follows:

[0050] A: Cleaning treatment of the silicon wafer substrate 1

[0051] First, clean the silicon substrate 1 with a thickness of 500 μm twice in sequence with acetone, methanol, and isopropanol, and dry it with nitrogen to determine that the surface of the silicon substrate 1 is clean;

[0052] B: Preparation of the silicon dioxide lower cladding

[0053] The silicon dioxide lower cladding 2 is grown by thermal oxidation. First, clean the silicon substrate 1 with deionized water, then soak it in a hydrofluoric acid solution with a mass fraction of 3% for 2 minutes to remove the natural oxide layer, and then oxidize the silicon substrate 1 without the natural oxide layer in a high-purity water vapor atmosphere at 1000 °C for 2 hours. After oxidation, it is naturally cooled to room temperature, so as to grow a silicon dioxide oxide layer 2 with a thickness of 6 μm on the surface of the silicon substrate 1;

[0054] C: Preparation of the electro-optic modulator electrode

[0055] A 0.8-μm-thick gold electrode layer 7 is evaporated on the silica lower cladding 2 by means of vacuum evaporation; then, photoresist BP212 is spin-coated on the surface of the gold electrode layer 7 at a rotation speed of 2500 revolutions per minute to obtain a thickness of 2 μm for BP212; the device with spin-coated photoresist BP212 is baked at a temperature of 150 °C for 20 minutes and then cooled to room temperature for mask lithography; the structure of the mask is the same as that of the metal electrode to be fabricated, and it is exposed under an ultraviolet lamp with a wavelength of 365 nm for 15 s so that the photoresist in the area other than the electrode is exposed; the device is placed in a NaOH solution with a mass concentration of 3‰ for 5 minutes to remove the exposed photoresist, then rinsed thoroughly with deionized water and dried with nitrogen, baked at 95 °C for 10 minutes and then cooled to room temperature; finally, the whole device is exposed for 2 s, and then the device is immersed in ethanol for 1 minute to obtain discrete metal electrodes 4 with the required structure, where the two parts of the electrodes are exactly the same, the width b1 is 20 μm, and the spacing gap between the two parts is 5 μm;

[0056] D: Preparation of the silica spacer layer

[0057] The silica spacer layer is grown by PECVD technology, that is, first, the silicon substrate 1 obtained in step C is successively cleaned with deionized water and a hydrofluoric acid solution with a mass fraction of 3% to remove the surface oxide layer; then, the cleaned silicon substrate 1 is placed in a PECVD device, the temperature is set to 300 °C, the radio frequency power supply is turned on to 100 W, and deposition is carried out for 20 minutes after plasma is generated; the high-energy electrons of the plasma will excite SiH4 and O2 molecules to decompose them into active groups; after the temperature of the silicon substrate 1 drops to room temperature, nitrogen is slowly introduced into the chamber of the PECVD device, so as to obtain a silica spacer layer 3 with a thickness of 0.2 μm on the surface of the silica oxide layer 2 and the discrete metal electrodes 4;

[0058] E: Preparation of the lead zirconate titanate planar core layer

[0059] A PZT precursor solution is synthesized by the sol-gel method (Can Huang, Electro-optic effect mechanism and energy storage performance regulation of lanthanum-doped lead zirconate titanate dielectric materials, China University of Geosciences, 2021), and the PZT precursor solution is spin-coated on the surface of the silica spacer layer 3 at a rotation speed of 3000 revolutions per minute, baked at 200 °C for 30 minutes and then cooled to room temperature to obtain an inverted-ridge-shaped lead zirconate titanate planar core layer 5 with a thickness of 0.3 μm;

[0060] F: Preparation of the polymer upper cladding

[0061] Using the spin coating process, the polymer upper cladding material is coated on the prepared lead zirconate titanate flat core layer 5 at a rotation speed of 4000 revolutions per minute, baked at 120 °C for 20 minutes and then cooled to room temperature to obtain a polymer upper cladding 6 with a thickness of 2 μm, thereby preparing a high-speed electro-optic modulator based on lead zirconate titanate thin film.

[0062] In this way, a high-speed electro-optic modulator based on lead zirconate titanate thin film that meets the requirements is prepared. It should be noted that although this patent document contains descriptions of many details, it should not be construed as a limitation on the scope of any disclosed technology or what may be claimed, but should be construed as a description of the features of specific embodiments that may be specific to the disclosed technology. The present invention can also have many variations, such as using electro-optic materials such as barium titanate and lithium niobate. Those skilled in the art, which are clearly disclosed in the present invention or obtained without any objection according to the written description of the document, fall within the scope of protection of this patent.

Claims

1. A high-speed electro-optic modulator based on lead zirconate titanate thin film, characterized in that: The invention is composed of, from bottom to top, a silicon substrate (1), a silicon dioxide oxide layer (2) grown on the upper surface of the substrate, discrete metal electrodes (4) evaporated on both sides of the upper surface of the silicon dioxide oxide layer (2), a silicon dioxide spacer layer (3) grown on the surface of the silicon dioxide oxide layer (2) and the discrete metal electrode (4), an inverted ridge-type lead zirconate titanate flat core layer (5) formed by spin coating on the silicon dioxide spacer layer (3), and a polymer upper cladding layer (6) spin coated on the lead zirconate titanate flat core layer (5); the discrete metal electrodes (4), the silicon dioxide spacer layer (3), the lead zirconate titanate flat core layer (5), and the polymer upper cladding layer (6) are of equal length.

2. A high-speed electro-optic modulator based on lead zirconate titanate thin film as claimed in claim 1, characterized in that: The length a1 of the discrete metal electrode 4, the silicon dioxide spacer layer 3, the lead zirconate titanate flat core layer 5, and the polymer upper cladding layer 6 is equal to 4 to 8 mm; the thickness of the silicon substrate (1) is 480 to 520 μm, the thickness of the silicon dioxide oxide layer (2) is 4 to 14 μm, the thickness of the discrete metal electrode (4) is 0.2 to 2 μm, the thickness of the silicon dioxide spacer layer (3) is 0.1 to 0.3 μm, the thickness of the flat region of the lead zirconate titanate flat core layer (5) is 0.1 to 0.4 μm, and the thickness of the polymer upper cladding layer (6) is 1 to 5 μm; the two parts of the discrete metal electrode (4) have exactly the same electrode structure, the width b1 is 10 to 20 μm, and the gap between the two parts is 2 to 20 μm.

3. A high-speed electro-optic modulator based on lead zirconate titanate thin film as claimed in claim 1, characterized in that: The material of the polymer upper cladding layer (6) is one of polyimide, polymethyl methacrylate, SU-8 2002 or SU-8 2005.

4. A method for preparing a high-speed electro-optic modulator based on a lead zirconate titanate thin film according to any one of claims 1 to 3, wherein the steps are as follows: A: Cleaning of silicon wafer substrate (1) First, the silicon substrate (1) is cleaned 2 to 4 times with acetone, methanol, and isopropanol in sequence, and then blown dry with nitrogen gas to ensure that the surface of the silicon substrate (1) is clean; B: Preparation of silica lower cladding A silicon dioxide lower cladding layer (2) is grown by a thermal oxidation method, that is, firstly, the silicon substrate (1) is cleaned with deionized water, then immersed in a hydrofluoric acid solution with a mass fraction of 1 to 5% for 1 to 2 minutes to remove the natural oxide layer, and then the silicon substrate (1) with the natural oxide layer removed is oxidized in a high-purity water vapor atmosphere at 900 to 1200° C. for 1 to 6 hours, and after the oxidation is completed, the silicon dioxide oxide layer (2) is grown on the surface of the silicon substrate (1); C: Electro-optic modulator electrode preparation A gold electrode layer (7) is evaporated on a silicon dioxide lower cladding layer (2) by a vacuum evaporation method, and then a photoresist BP212 is coated on the surface of the gold electrode layer (7) by a spin coating process, with a rotation speed of 1000 to 8000 revolutions per minute, so that the thickness of the BP212 is 1 to 10 μm; the device with the spin-coated photoresist BP212 is baked at a temperature of 50 to 300° C. for 10 to 50 minutes, and then cooled to room temperature for mask photolithography; the structure of the mask is the same as that of the discrete metal electrode (4) to be prepared, Expose the device under ultraviolet light with a wavelength of 300 to 500 nm for 10 to 20 seconds to expose the photoresist in areas other than the electrode; place the device in a NaOH solution with a mass concentration of 2 to 5‰ for 5 to 20 minutes to remove the exposed photoresist, then rinse it with deionized water and blow it dry with nitrogen, bake the device at 80 to 300° C. for 5 to 40 minutes and then cool it to room temperature; finally, expose the entire device for 2 to 5 seconds, and then soak the device in ethanol for 1 to 8 minutes to obtain discrete metal electrodes (4) of the required structure; D: Preparation of SiO2 spacer layer First, the silicon substrate (1) obtained in step C is cleaned in sequence with deionized water and a hydrofluoric acid solution with a mass fraction of 1 to 5% to remove the surface oxide layer; then, the cleaned silicon substrate (1) is placed in a PECVD device, the temperature is set to 300 to 400° C., the radio frequency power is turned on to 100 to 300 W, and after plasma is generated, deposition is performed for 10 to 30 minutes; after the temperature of the silicon substrate (1) drops to room temperature, nitrogen is slowly filled into the chamber of the PECVD device, thereby forming a silicon dioxide spacer layer (3) on the surface of the silicon dioxide oxide layer (2) and the discrete metal electrode (4); E: Preparation of lead zirconate titanate flat core layer A PZT precursor solution is applied to the surface of the silicon dioxide spacer layer (3) by a spin coating process at a rotation speed of 1000 to 8000 revolutions per minute, baked at 100 to 500° C. for 20 to 50 minutes, and then cooled to room temperature, thereby obtaining an inverted ridge-type lead zirconate titanate flat core layer (5); F: Preparation of polymer upper cladding The polymer upper cladding material is coated on the prepared lead zirconate titanate flat core layer (5) by a spin coating process at a rotation speed of 1000 to 6000 rpm, baked at 100 to 500° C. for 20 to 50 minutes and then cooled to room temperature to obtain a polymer upper cladding layer (6), thereby preparing a high-speed electro-optical modulator based on zirconate titanate film.

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