A PZT wafer film and a preparation method thereof, and a Mach-Zehnder electro-optic modulator and a preparation method thereof

Abstract

The application discloses a PZT wafer film and a preparation method thereof, and a Mach-Zehnder electro-optic modulator and a preparation method thereof, and belongs to the technical field of optical material preparation. The application utilizes a sol-gel method to first prepare a seed layer on a SiO2 / Si substrate, then prepare a PZT dry film, and then perform a high-pressure oxygen atmosphere heat treatment process in an oxygen atmosphere to obtain the PZT wafer film. The application solves the problem that the PZT wafer prepared by a traditional normal-pressure heat treatment process has a low electro-optic coefficient and is difficult to meet the demand of high-performance photoelectric devices. The electro-optic coefficient of the PZT wafer film is significantly improved from 69pm / V of the traditional normal-pressure heat treatment to 130pm / V, the optical performance of the PZT wafer film is effectively improved, the process is simple, the cost is controllable, and the application has a wide application prospect in the fields of optical communication, optical storage, electro-optic modulators and the like.

Description

Technical Field

[0001] This invention belongs to the field of optical material preparation technology, and specifically relates to a PZT wafer thin film and its preparation method, and a Mach-Zehnder electro-optic modulator and its preparation method. Background Technology

[0002] PZT (Lead Zirconate Titanate) is a typical ferroelectric ceramic material with excellent piezoelectric, ferroelectric, and electro-optic properties, and it has been widely used in many fields such as sensors, actuators, memories, and electro-optic modulators. Among them, the electro-optic coefficient is a key indicator for measuring the electro-optic performance of PZT materials and directly affects its application effect in optoelectronic devices.

[0003] Currently, some studies have attempted to improve the electro-optic properties of PZT materials through methods such as electric field polarization and altering fabrication process parameters. However, these methods often suffer from complex processes, cumbersome steps, and long preparation cycles, leading to low production efficiency and insignificant results. Traditional PZT thin film fabrication methods typically employ atmospheric pressure heat treatment. This heat treatment method results in a large number of oxygen vacancies within the film, a pronounced "pinning effect," and difficulty in ferroelectric domain inversion during electric field polarization, resulting in a low electro-optic coefficient. PZT wafers fabricated using this process have relatively low electro-optic coefficients, typically around 70 pm / V, which is insufficient to meet the requirements of high-performance optoelectronic devices.

[0004] Patent CN120949469A discloses a lead zirconate titanate composite thin film with a high electro-optic coefficient, its preparation method, and an electro-optic modulator. It employs a sol-gel method to prepare a La-doped PZT buffer layer and a PZT ferroelectric host layer on an insulating substrate. The buffer layer induces a (001) / (100) mixed orientation in the ferroelectric host layer, thereby improving the electro-optic coefficient to a certain extent. However, this prior art solution still has the following technical defects:

[0005] First, the existing technology uses an atmospheric pressure heat treatment process to prepare PZT thin films, resulting in a high concentration of oxygen vacancies within the film and a still significant "pinning effect." Although this existing technology improves the electro-optic coefficient to some extent through buffer layer-induced orientation optimization, the limited oxygen supply due to the atmospheric pressure atmosphere during the heat treatment process fails to adequately suppress oxygen vacancies generated by oxygen deficiency in the PZT crystal. Excessive oxygen vacancy concentration makes it difficult for ferroelectric domains to reverse polarization, limiting further improvement in the electro-optic coefficient. The highest electro-optic coefficient of the composite thin film prepared by this existing technology is 275.3 pm / V (measured by the Teng-Man method), but the actual device performance is still constrained by the oxygen vacancy problem.

[0006] Second, the existing technology uses the Teng-Man method to test the electro-optic coefficients, and the test results deviate significantly from the actual performance of the device. All electro-optic coefficient data in this existing technology are measured using the Teng-Man method, but the values ​​obtained by the Teng-Man method are often too high and cannot directly reflect the true electro-optic performance of the device in practical applications. When the thin film is fabricated as an actual electro-optic modulator device, the actual electro-optic coefficient will be significantly lower than the Teng-Man test value due to factors such as device structure, electrode configuration, and electric field distribution. This existing technology does not provide measured electro-optic coefficient data for the device, making it impossible to accurately assess its application performance in actual devices.

[0007] Therefore, how to effectively reduce the oxygen vacancy concentration and improve the electro-optic coefficient of PZT wafers has become a hot and difficult research topic in this field. Summary of the Invention

[0008] To address the aforementioned problems, this invention provides a PZT wafer thin film and its fabrication method, as well as a Mach-Zehnder electro-optic modulator and its fabrication method. The PZT wafer thin film fabrication method provided by this invention is simple to operate, low in cost, and can significantly improve the electro-optic coefficient of the wafer thin film, thereby enhancing its optical performance.

[0009] To achieve the above-mentioned objectives, the present invention adopts the following technical solution:

[0010] This invention provides a method for fabricating a Mach-Zehnder electro-optic modulator, comprising the following steps: etching a PZT wafer thin film to obtain a ridge waveguide; depositing a gold thin film on both sides of the ridge waveguide to form coplanar electrodes, thereby obtaining the Mach-Zehnder electro-optic modulator;

[0011] The method for preparing the PZT wafer thin film includes the following steps:

[0012] S1. Spin-coat the seed layer precursor solution onto the substrate and anneal it to obtain a seed layer film;

[0013] S2. Spin-coating the PZT precursor solution onto the seed layer film to obtain a wet film, followed by pyrolysis to obtain a dry PZT film, and then performing high-pressure oxygen atmosphere heat treatment to obtain a PZT film. Repeating spin-coating, pyrolysis and high-pressure oxygen atmosphere heat treatment to obtain a PZT wafer film.

[0014] The high-pressure oxygen atmosphere heat treatment is as follows: oxygen pressure is 2.0 to 5.0 MPa, heating rate is 15 to 20 °C / min, heating to 600 to 650 °C, and holding for 10 min;

[0015] In step S1, the seed layer precursor solution is prepared by dissolving lanthanum nitrate hexahydrate in ethylene glycol monomethyl ether.

[0016] Furthermore, in step S1, the annealing treatment is performed at a temperature of 400°C for 10 minutes.

[0017] Further, in step S2, the PZT precursor solution is prepared by dissolving lead acetate trihydrate, zirconium propoxide, and titanium isopropoxide in ethylene glycol monomethyl ether; the molar ratio of lead acetate trihydrate, zirconium propoxide, and titanium isopropoxide is (1.8-2.3):1:(0.54-0.91).

[0018] Furthermore, in step S2, the temperature of the pyrolysis treatment is 250–350°C.

[0019] The present invention also provides a Mach-Zehnder electro-optic modulator prepared by the above preparation method, wherein the width of the ridge waveguide on the Mach-Zehnder electro-optic modulator is 1.3 to 1.7 μm, the spacing between the coplanar electrodes is 4.5 to 5.5 μm, and the electrode thickness is 280 to 320 nm.

[0020] Compared with the prior art, the present invention has the following advantages and technical effects:

[0021] This invention utilizes the sol-gel method to first prepare a seed layer on a SiO2 / Si substrate, then prepare a PZT dry film, and subsequently perform a high-pressure oxygen atmosphere heat treatment process to obtain a PZT wafer thin film. This solves the problem that the electro-optic coefficient of PZT wafers prepared by traditional atmospheric pressure heat treatment is low, making it difficult to meet the requirements of high-performance optoelectronic devices. Furthermore, existing improved methods cannot guarantee film quality while simplifying the process. This invention significantly improves the electro-optic coefficient of PZT wafers from 69 pm / V of traditional atmospheric pressure heat treatment to 130 pm / V, effectively improving the optical performance of PZT wafers. Moreover, the process is simple and cost-controllable, and it has broad application prospects in optical communication, optical storage, electro-optic modulators, and other fields.

[0022] The PZT wafer thin film prepared by this invention has high electro-optic coefficient, high transparency and good electro-optic performance. Its electro-optic coefficient reaches 130 pm / V, which is more than 4 times that of thin film lithium niobate (30 pm / V). It can realize low power consumption and high speed on-chip electro-optic modulation and is suitable for multiple fields such as optical communication and energy storage devices. Detailed Implementation

[0023] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0024] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0025] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0026] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0027] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0028] To facilitate understanding, the following explanations will first cover several technical terms.

[0029] The room temperature in this invention refers to 25±2℃.

[0030] Example 1

[0031] 1) Preparation of seed layer precursor solution:

[0032] Weigh 0.866 g (2.0 mmol) of lanthanum nitrate hexahydrate, dissolve it in 20 mL of ethylene glycol monomethyl ether at room temperature, stir for 12 h, filter, and obtain a clear and transparent solution, which is the seed layer precursor solution.

[0033] 2) Preparation of PZT precursor solution:

[0034] Weigh 12 g (31.63 mmol) of lead acetate trihydrate, dissolve it in 20 mL of ethylene glycol monomethyl ether, heat to 120 °C and stir for 1.0 h. Then add 6.41 g (13.71 mmol) of 70 wt.% zirconium propoxide solution and stir for 10 min. Then add 3.56 g (12.5 mmol) of titanium isopropoxide and stir for 0.5 h. Cool to room temperature, add 20 mL of ethylene glycol monomethyl ether, stir overnight, filter, and obtain a clear and transparent solution, which is the PZT precursor solution.

[0035] 3) Preparation of PZT wafers:

[0036] The seed layer precursor solution prepared in step 1) was spin-coated onto a SiO2 / Si substrate at a spin speed of 3000 rpm for 15 s. After annealing at 400℃ for 10 min, a seed layer film with a thickness of 10 nm was prepared.

[0037] The PZT precursor solution prepared in step 2) was spin-coated onto the seed layer film at a spin speed of 1500 rpm for 15 s, then adjusted to 3000 rpm for 20 s to prepare a wet film. The wet film was then pyrolyzed at 300 °C for 10 min to obtain a dry PZT film (100 nm thick). The film was then subjected to high-pressure oxygen atmosphere heat treatment under the following conditions: oxygen pressure of 2.0 MPa, heating rate of 20 °C / min, heating to 600 °C, holding for 10 min, and then naturally cooling to room temperature to obtain a PZT film. By repeating spin-coating, pyrolysis, and high-pressure oxygen atmosphere heat treatment twice, a PZT wafer film with a thickness of 300 nm was obtained.

[0038] 4) Fabrication of Mach-Zehnder electro-optic modulator

[0039] Using the PZT wafer thin film prepared in step 3), a Mach-Zehnder electro-optic modulator was prepared using the following steps:

[0040] S1. Photolithography patterning: Photoresist is spin-coated onto the surface of the PZT wafer thin film prepared in step 3), and ultraviolet lithography is used to define the ridge waveguide pattern;

[0041] S2. Etching to form a ridge waveguide: Using photoresist as a mask, inductively coupled plasma etching technology is used to selectively etch the PZT wafer thin film to a depth of 100nm, forming a ridge waveguide structure with a height of 100nm and a width of 1.5μm. After etching, the residual photoresist is removed.

[0042] S3. Fabrication of coplanar electrodes: Using electron beam evaporation and lift-off processes, a thin gold film is deposited on both sides of the ridge waveguide prepared in step S2 to form coplanar electrodes. The electrode spacing of the coplanar electrodes is 5.0 μm and the electrode thickness is 300 nm.

[0043] S4. Device Polarization: The Mach-Zehnder electro-optic modulator prepared in step S3 is polarized. Specifically, a DC polarization electric field (300 kV / cm, perpendicular to the waveguide) is applied to both ends of the coplanar electrodes. The electric field strength is greater than the coercive field of the PZT thin film (50 kV / cm), so that the ferroelectric domains of the PZT wafer thin film are oriented along the direction of the electric field to obtain stable electro-optic response characteristics.

[0044] Example 2

[0045] 1) Preparation of seed layer precursor solution:

[0046] Weigh 0.866 g (2.0 mmol) of lanthanum nitrate hexahydrate, dissolve it in 20 mL of ethylene glycol monomethyl ether at room temperature, stir for 12 h, filter, and obtain a clear and transparent solution, which is the seed layer precursor solution.

[0047] 2) Preparation of PZT precursor solution:

[0048] Weigh 12 g (31.63 mmol) of lead acetate trihydrate, dissolve it in 20 mL of ethylene glycol monomethyl ether, heat to 110 °C and stir for 3.0 h. Then add 8.01 g (17.13 mmol) of 70 wt.% zirconium propoxide solution and stir for 10 min. Then add 2.59 g (9.22 mmol) of titanium isopropoxide and stir for 0.5 h. Cool to room temperature, add 20 mL of ethylene glycol monomethyl ether, stir overnight, filter, and obtain a clear and transparent solution, which is the PZT precursor solution.

[0049] 3) Preparation of PZT wafers:

[0050] The seed layer precursor solution prepared in step 1) was spin-coated onto a SiO2 / Si substrate at a spin speed of 3000 rpm for 15 s. After annealing at 400℃ for 10 min, a seed layer film with a thickness of 10 nm was prepared.

[0051] The PZT precursor solution prepared in step 2) was spin-coated onto the seed layer film at a spin speed of 1500 rpm for 15 s, then adjusted to 3000 rpm for 20 s to prepare a wet film. The wet film was then pyrolyzed at 300 °C for 10 min to obtain a dry PZT film (100 nm thick). The film was then subjected to high-pressure oxygen atmosphere heat treatment under the following conditions: oxygen pressure of 2.0 MPa, heating rate of 15 °C / min, heating to 650 °C, holding for 10 min, and then cooling naturally to obtain a PZT film. By repeating spin-coating, pyrolysis, and high-pressure oxygen atmosphere heat treatment twice, a PZT wafer film with a thickness of 300 nm was obtained.

[0052] 4) Fabrication of Mach-Zehnder electro-optic modulator

[0053] Using the PZT wafer thin film prepared in step 3), a Mach-Zehnder electro-optic modulator was prepared using the following steps:

[0054] S1. Photolithography patterning: Photoresist is spin-coated onto the surface of the PZT wafer thin film prepared in step 3), and ultraviolet lithography is used to define the ridge waveguide pattern;

[0055] S2. Etching to form a ridge waveguide: Using photoresist as a mask, inductively coupled plasma etching technology is used to selectively etch the PZT wafer thin film to a depth of 120 nm, forming a ridge waveguide structure with a height of 120 nm and a width of 1.5 μm. After etching, the residual photoresist is removed.

[0056] S3. Fabrication of coplanar electrodes: Using electron beam evaporation and metal lift-off processes, gold thin films are deposited on both sides of the ridge waveguide prepared in step S2 to form coplanar electrodes; the electrode spacing of the coplanar electrodes is 5.0 μm and the electrode thickness is 300 nm.

[0057] S4. Device Polarization: The Mach-Zehnder electro-optic modulator prepared in step S3 is polarized. Specifically, a DC polarization electric field (300 kV / cm, perpendicular to the waveguide) is applied to both ends of the coplanar electrodes. The electric field strength is greater than the coercive field of the PZT thin film (50 kV / cm), so that the ferroelectric domains of the PZT wafer thin film are oriented along the direction of the electric field to obtain stable electro-optic response characteristics.

[0058] Example 3

[0059] 1) Preparation of seed layer precursor solution:

[0060] Weigh 0.866 g (2.0 mmol) of lanthanum nitrate hexahydrate, dissolve it in 20 mL of ethylene glycol monomethyl ether at room temperature, stir for 12 h, filter, and obtain a clear and transparent solution, which is the seed layer precursor solution.

[0061] 2) Preparation of PZT precursor solution:

[0062] Weigh 12 g (31.63 mmol) of lead acetate trihydrate, dissolve it in 20 mL of ethylene glycol monomethyl ether, heat to 110 °C and stir for 3 h, then add 6.41 g (13.71 mmol) of 70 wt.% zirconium propoxide solution, stir for 10 min, then add 3.56 g (12.5 mmol) of titanium isopropoxide and stir for 0.5 h, cool to room temperature, add 20 mL of ethylene glycol monomethyl ether, stir overnight, filter, and obtain a clear and transparent solution, which is the PZT precursor solution;

[0063] 3) Preparation of PZT wafers:

[0064] The seed layer precursor solution prepared in step 1) was spin-coated onto a SiO2 / Si substrate at a spin speed of 3000 rpm for 15 s. After annealing at 400℃ for 10 min, a seed layer film with a thickness of 10 nm was prepared.

[0065] The PZT precursor solution prepared in step 2) was spin-coated onto the seed layer film at a spin speed of 1500 rpm for 15 s, then adjusted to 3000 rpm for 20 s to prepare a wet film. The wet film was then pyrolyzed at 300 °C for 10 min to obtain a dry PZT film (100 nm thick). The film was then subjected to high-pressure oxygen atmosphere heat treatment under the following conditions: oxygen pressure of 5.0 MPa, heating rate of 15 °C / min, heating to 600 °C, holding for 10 min, and then naturally cooled to obtain a PZT film. By repeating the spin-coating, pyrolysis, and high-pressure oxygen atmosphere heat treatment twice, a PZT wafer film with a thickness of 300 nm was obtained.

[0066] 4) Fabrication of Mach-Zehnder electro-optic modulator

[0067] Using the PZT wafer thin film prepared in step 3), a Mach-Zehnder electro-optic modulator was prepared using the following steps:

[0068] S1. Photolithography patterning: Photoresist is spin-coated onto the surface of the PZT wafer thin film prepared in step 3), and ultraviolet lithography is used to define the ridge waveguide pattern;

[0069] S2. Etching to form a ridge waveguide: Using photoresist as a mask, inductively coupled plasma etching technology is used to selectively etch the PZT wafer thin film to a depth of 150 nm, forming a ridge waveguide structure with a height of 150 nm and a width of 1.5 μm. After etching, the residual photoresist is removed.

[0070] S3. Fabrication of coplanar electrodes: Using electron beam evaporation and metal lift-off processes, gold films are deposited on both sides of the ridge waveguide prepared in step S2 to form coplanar electrodes; the electrode spacing of the coplanar electrodes is 5.0 μm and the electrode thickness is 300 nm, thus fabricating a Mach-Zehnder electro-optic modulator;

[0071] S4. Device Polarization: The Mach-Zehnder electro-optic modulator prepared in step S3 is polarized. Specifically, a DC polarization electric field (300 kV / cm, perpendicular to the waveguide) is applied to both ends of the coplanar electrodes. The electric field strength is greater than the coercive field of the PZT thin film (50 kV / cm), so that the ferroelectric domains of the PZT wafer thin film are oriented along the direction of the electric field to obtain stable electro-optic response characteristics.

[0072] Comparative Example 1

[0073] Same as Example 1, except that in step 3), atmospheric pressure heat treatment is used, and the specific operation is as follows:

[0074] 1) Preparation of seed layer precursor solution: Same as in Example 1;

[0075] 2) Preparation of PZT precursor solution: Same as in Example 1;

[0076] 3) Preparation of PZT thin films:

[0077] The seed layer precursor solution prepared in step 1) was spin-coated onto a SiO2 / Si substrate at a spin speed of 3000 rpm for 15 s. After annealing at 400℃ for 10 min, a seed layer film was prepared.

[0078] The PZT precursor solution prepared in step 2) was spin-coated onto the seed layer film at a spin speed of 1500 rpm for 15 s, then adjusted to 3000 rpm for 20 s to prepare a wet film. The wet film was then pyrolyzed at 300℃ for 10 min to obtain a dry PZT film. This dry film was then subjected to atmospheric pressure heat treatment. The atmospheric pressure heat treatment conditions were as follows: the dry PZT film was placed in a tube furnace under atmospheric pressure, with an oxygen flow rate of 50 mL / min and a heating rate of 20℃ / min, reaching 600℃ and holding for 10 min, followed by natural cooling to obtain the PZT thin film. By repeating the spin-coating, pyrolysis, and atmospheric pressure heat treatment twice, a PZT wafer thin film with a thickness of 300 nm was obtained.

[0079] 4) Fabrication of the electro-optic modulator: Same as in Example 1.

[0080] Performance testing

[0081] 1) Electro-optic coefficient measurement: This invention utilizes an alternating voltage signal (from -15V to +15V, frequency 1kHz), the modulator output light is coupled to a photodetector, the photodetector is connected to an oscilloscope, the waveform of the oscilloscope is read, and the half-wave voltage is read under overmodulation. The Mach-Zehnder electro-optic modulators prepared in Examples 1-3 and Comparative Example 1 were tested, and the electro-optic coefficient of the PZT wafer thin film was calculated according to formula (1). The measurement results are shown in Table 1.

[0082] (1)

[0083] In the formula, λ: operating wavelength (1550nm);

[0084] g: Electrode spacing (5.0 μm);

[0085] n: Effective refractive index (1.92);

[0086] Γ: Electric field overlap factor (0.55);

[0087] V π Half-wave voltage (measured using single-arm drive mode, unit: V);

[0088] L: Mach-Zehnder modulator length (0.5 mm).

[0089] The half-wave voltages of Examples 1-3 and Comparative Example 1 are 30.52V, 36.07V, 31.7V and 57.5V respectively; corresponding to electro-optic coefficients of 130 pm / V, 110 pm / V, 125 pm / V and 69 pm / V respectively.

[0090] 2) Oxygen vacancy concentration determination: The oxygen vacancy concentration of the PZT wafer thin films prepared in Examples 1-3 and Comparative Example 1 was determined by EPR (electron paramagnetic resonance). The results are shown in Table 1.

[0091] Table 1 Oxygen vacancy concentration and electro-optic coefficient

[0092]

[0093] As can be seen from Table 1, the electro-optic coefficients of Examples 1-3 are significantly improved compared with Comparative Example 1.

[0094] Patent CN120949469A uses the Teng-Man method to test the electro-optic coefficient of the composite thin film. In order to prove that the photoelectric performance of the PZT wafer thin film prepared by this invention is superior to that of the prior art, this invention does not use the PZT wafer thin film prepared in Example 1 as an electro-optic modulator, but uses the Teng-Man method to test its electro-optic coefficient. The electro-optic coefficient obtained by the test is 300 pm / V. Compared with the data in Table 1 (130 pm / V), it shows that the Teng-Man method for testing the electro-optic coefficient is too large and its actual application in devices is relatively small. The electro-optic coefficients of the composite films prepared in Examples 1-4 of patent CN120949469A are 275.3 pm / V, 245.2 pm / V, 212 pm / V, and 233.5 pm / V, respectively. These coefficients are all lower than those of the PZT wafer film prepared in Example 1 of this invention. This proves that the PZT wafer film prepared by the high-pressure oxygen atmosphere heat treatment process of this invention exhibits a higher electro-optic coefficient. In this invention, the PZT wafer film is prepared under a high-pressure oxygen atmosphere, which can provide a sufficient environment for film oxidation, reduce the probability of oxygen vacancies generated by oxygen deficiency in PZT crystals, and thus reduce the "pinning effect". The higher the oxygen vacancy concentration, the more obvious this effect is. The ferroelectric domain structure of the PZT wafer film is more likely to reverse during polarization, ultimately achieving the purpose of improving the electro-optic performance of PZT.

[0095] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for fabricating a Mach-Zehnder electro-optic modulator, characterized in that, Includes the following steps: Etching of PZT wafer thin films yields ridge waveguides; A thin gold film is deposited on both sides of the ridge waveguide to form coplanar electrodes, thus obtaining the Mach-Zehnder electro-optic modulator; The method for preparing the PZT wafer thin film includes the following steps: S1. Spin-coat the seed layer precursor solution onto the substrate and anneal it to obtain a seed layer film; S2. Spin-coating the PZT precursor solution onto the seed layer film to obtain a wet film, followed by pyrolysis to obtain a dry PZT film, and then performing high-pressure oxygen atmosphere heat treatment to obtain a PZT film. Repeating spin-coating, pyrolysis and high-pressure oxygen atmosphere heat treatment to obtain a PZT wafer film. The high-pressure oxygen atmosphere heat treatment is as follows: oxygen pressure is 2.0 to 5.0 MPa, heating rate is 15 to 20 °C / min, heating to 600 to 650 °C, and holding for 10 min; In step S1, the seed layer precursor solution is prepared by dissolving lanthanum nitrate hexahydrate in ethylene glycol monomethyl ether.

2. The method for fabricating the Mach-Zehnder electro-optic modulator according to claim 1, characterized in that, In step S1, the annealing temperature is 400℃ and the time is 10 minutes.

3. The method for fabricating the Mach-Zehnder electro-optic modulator according to claim 1, characterized in that, In step S2, the PZT precursor solution is prepared by dissolving lead acetate trihydrate, zirconium propoxide and titanium isopropoxide in ethylene glycol monomethyl ether; the molar ratio of lead acetate trihydrate, zirconium propoxide and titanium isopropoxide is (1.8-2.3):1:(0.54-0.91).

4. The method for fabricating the Mach-Zehnder electro-optic modulator according to claim 1, characterized in that, In step S2, the temperature of the pyrolysis treatment is 250–350°C.

5. A Mach-Zehnder electro-optic modulator prepared by the method according to claims 1 to 4, characterized in that, The width of the ridge waveguide on the Mach-Zehnder electro-optic modulator is 1.3–1.7 μm, the spacing between the coplanar electrodes is 4.5–5.5 μm, and the electrode thickness is 280–320 nm.

Images