A method for preparing barium titanate thin film for phase shift unit of electro-optic modulator and application thereof

Abstract

The application relates to a preparation method and application of a barium titanate film for a phase shift unit of an electro-optical modulator, and particularly relates to the technical field of optoelectronic devices. The preparation method comprises the following steps: mixing a titanium source, a barium source, a solvent and a chelating agent, hydrolyzing and aging to obtain a barium titanate sol precursor; spin coating the barium titanate sol precursor on the surface of a substrate, preheating and crystallizing to form a barium titanate film; and annealing the barium titanate film to form a single-oriented barium titanate film. The barium titanate sol is prepared by a sol-gel method, and the film is prepared by a spin coating method, so that the process is simple, the cost is low, and the method is suitable for large-scale mass production; through specific preheating, crystallization and annealing treatment, the film is induced to form (001) preferred orientation and reversible a / c domain structure, optical scattering loss is reduced, and the thermo-optic coefficient and performance stability are improved.

Description

Technical Field

[0001] This application relates to the field of optoelectronic device technology, and in particular to a method for preparing and applying a barium titanate thin film for a phase-shifting unit of an electro-optic modulator. Background Technology

[0002] Electro-optic modulators are core devices for controlling the phase and amplitude of optical signals in fields such as optical communication, optical interconnection, and optical sensing. The phase-shifting unit, as a core component of the electro-optic modulator, directly determines the modulator's modulation efficiency, response speed, insertion loss, and long-term stability. With the rapid iteration of 5G / 6G communication, quantum communication, and integrated photonic chips, the industry has placed stringent demands on the phase-shifting unit of electro-optic modulators, requiring "high modulation efficiency, low insertion loss, fast response speed, and high integration," especially placing higher performance requirements on the core functional layer of the phase-shifting unit—the electro-optic thin film material.

[0003] In related technologies, the electro-optic thin film materials used in the phase-shifting unit of electro-optic modulators mainly include lithium niobate and barium titanate. Although lithium niobate thin films have mature electro-optic modulation characteristics, they have drawbacks such as complex fabrication processes, low electro-optic coefficients, and insufficient phase-shift modulation efficiency, which cannot meet the application scenarios of low power consumption and high-speed modulation.

[0004] Barium titanate (BTO) films, among ferroelectric materials, have become the preferred functional layer material for electro-optic modulators due to their excellent electro-optic effect (electro-optic coefficient can reach over 200 pm / V), good dielectric properties, and potential integration compatibility with silicon substrates. However, existing barium titanate thin films and related preparation technologies used in phase-shifting units of electro-optic modulators still face many technical bottlenecks that urgently need to be addressed, severely limiting their practical application in phase-shifting units: First, the poor orientation of the thin films, mostly random or mixed orientations, leads to high light scattering loss, which in turn affects the insertion loss performance of the phase-shifting unit and fails to meet the low-loss requirements; Second, the internal domain structure of the thin film is difficult to control and has poor reversibility, resulting in a significant decrease in phase-shifting stability after multiple control cycles; Third, the annealing process in the preparation process is not optimized for thermo-optical phase-shifting characteristics, leading to an imbalance in the a / c domain ratio in the thin film, which fails to fully utilize its thermo-optical effect, making it difficult to achieve efficient phase control and balance phase-shifting efficiency with real-time response; Fourth, traditional vapor deposition methods (such as MBE, sputtering, etc.) have complex preparation processes, high equipment costs, long preparation cycles, and difficulty in controlling the uniformity of the thin films, which cannot meet the needs of large-scale industrial production of phase-shifting units for electro-optic modulators.

[0005] Therefore, developing a barium titanate thin film with a simple preparation process, low cost, scalable production, high orientation, stable reversible domain structure, and low light scattering loss, as well as a high-efficiency, low-loss, and high-stability electro-optic modulator phase-shifting unit based on the thin film, to solve the aforementioned technical bottlenecks in the prior art, has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] This application provides a method for preparing barium titanate thin films for use in phase-shifting units of electro-optic modulators and its application, aiming to solve the problems of disordered orientation, poor domain structure reversibility, high preparation cost, high power consumption and insufficient stability of existing barium titanate thin films and electro-optic modulator phase-shifting units.

[0007] The technical solution provided by this invention is as follows: In a first aspect, this application provides a method for preparing a barium titanate thin film for a phase-shifting unit of an electro-optic modulator, comprising the following steps: A barium titanate sol precursor is obtained by mixing a titanium source, a barium source, a solvent, and a chelating agent, followed by hydrolysis and aging. The barium titanate sol precursor is spin-coated onto the substrate surface, and after preheating and crystallization, a barium titanate thin film is formed. The barium titanate film is annealed to form a barium titanate film with a single orientation.

[0008] In some embodiments, the barium titanate film has a (001) orientation and contains an α-domain and β-domain structure that can be reversibly switched with temperature.

[0009] In some embodiments, the thickness of the barium titanate film is 100~500 nm.

[0010] In some embodiments, the titanium source includes tetrabutyl titanate.

[0011] In some embodiments, the barium source includes barium acetate.

[0012] In some embodiments, the solvent includes ethylene glycol methyl ether.

[0013] In some embodiments, the chelating agent includes acetylacetone.

[0014] In some embodiments, the molar ratio of barium in the barium source to titanium in the titanium source is 1:(1.0~1.1).

[0015] In some embodiments, the concentration of the barium titanate sol precursor is 0.1-0.5 mol / L.

[0016] In some embodiments, the preheating temperature is 200-300°C and the time is 8-10 minutes.

[0017] In some embodiments, the crystallization treatment is performed at a temperature of 500-600°C for a time of 10-30 minutes.

[0018] In some embodiments, the annealing temperature is 600-800°C and the time is 5-30 minutes.

[0019] Secondly, this application provides a barium titanate thin film, which is prepared by the method described above.

[0020] Thirdly, this application provides an electro-optic modulator phase-shifting unit, the electro-optic modulator phase-shifting unit comprising: Substrate; A platinum electrode layer is disposed on the substrate; A lanthanum nickelate buffer layer is disposed on the side of the platinum electrode layer away from the substrate; A phase-shifting functional layer is disposed on the side of the lanthanum nickelate buffer layer away from the platinum electrode layer; The phase-shifting functional layer includes the barium titanate thin film described above.

[0021] In some embodiments, a heating unit is further included, disposed in a region adjacent to the phase-shifting functional layer, for providing temperature regulation to the phase-shifting functional layer.

[0022] In some embodiments, the operating wavelength of the electro-optic modulator phase-shifting unit includes the C-band of 1530-1565 nm.

[0023] Compared with existing technologies, the beneficial effects of this application include: 1. High modulation efficiency and low power consumption: The (001) oriented barium titanate film prepared by sol-gel spin coating has excellent a / c domain conversion capability after being controlled by a specific annealing process. The modulation depth can reach 55% at a wavelength of 1550nm. Its thermo-optic coefficient is twice that of traditional silicon-based materials, so that the power consumption of the phase shift unit of the electro-optic modulator based on this film is only 50% of that of the traditional silicon-based modulator, which is suitable for the needs of low power integration scenarios.

[0024] 2. Excellent modulation stability: The regulated (001) orientation structure reduces the light scattering loss of the thin film to below 0.5dB / cm, and the domain structure has good reversibility. After 1000 cycles in the temperature range of 25-50℃, the modulation depth fluctuation is less than 3%, and the attenuation rate is less than 2% after 1000 hours of long-term operation, which meets the reliability requirements of optical communication systems.

[0025] 3. Compatible with silicon-based integration and low-cost fabrication: The sol-gel combined spin coating process is simple and convenient to operate, and the fabrication cost is much lower than that of the traditional vapor deposition method. It is suitable for large-scale mass production, improves integration efficiency, and reduces device fabrication costs.

[0026] 4. Strong adaptability to multiple scenarios: The phase shift unit of this electro-optic modulator has a response time of 0.1376ms / 0.3008ms; combined with micro heater optimization, the response speed can be improved to the microsecond level, which has the potential to be extended to high-speed optical communication scenarios. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a schematic flowchart illustrating the preparation method of barium titanate thin film according to an embodiment of this application.

[0029] Figure 2 This is a schematic diagram of the phase shift unit of the electro-optic modulator in an embodiment of this application.

[0030] Reference numerals: Electro-optic modulator phase shift unit 100, substrate 10, platinum electrode layer 20, lanthanum nickelate buffer layer 30, phase shift functional layer 40. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0032] This application provides a method for preparing barium titanate thin films for use in phase-shifting units of electro-optic modulators and its application, aiming to solve the problems of disordered orientation, poor domain structure reversibility, high preparation cost, high power consumption and insufficient stability of existing barium titanate thin films and electro-optic modulator phase-shifting units.

[0033] In a first aspect, this application provides a method for preparing a barium titanate thin film for a phase-shifting unit of an electro-optic modulator, such as... Figure 1 As shown, it includes the following steps: S100: A barium titanate sol precursor is obtained by mixing a titanium source, a barium source, a solvent, and a chelating agent, followed by hydrolysis and aging. S200: The barium titanate sol precursor is spin-coated onto the substrate surface, and after preheating and crystallization treatment, a barium titanate thin film is formed. S300: Anneal the barium titanate film to form a barium titanate film.

[0034] In this embodiment, the S100 sol precursor is prepared by mixing titanium source, barium source, solvent, and chelating agent, followed by hydrolysis and aging to form a stable barium titanate sol precursor. This provides a uniform and well-dispersed raw material basis for subsequent thin film deposition, ensuring the accuracy of the thin film stoichiometry. The S200 spin coating and pretreatment involves uniformly coating the sol onto the substrate surface using spin coating, followed by low-temperature desizing to gradually remove organic matter and small molecules and initially form a crystal structure. Simultaneously, high-temperature crystallization forms a specific orientation structure. The S300 annealing treatment, through specific temperature and atmosphere control, promotes the perfection of the thin film crystal structure, inducing the formation of (001) preferred orientation and reversibly switchable a / c domain structures. This reduces scattering loss during light transmission and improves the stability and control reliability of the thin film's thermo-optical properties.

[0035] It should be explained that the "reversibly switchable a / c domain structure" refers to the existence of two types of domains (i.e., a-domains and c-domains) with different spontaneous polarization directions within the barium titanate film. These two domains can interconvert under external excitation (electric field or temperature), and the transition process exhibits good reversibility and repeatability. Here, a-domains refer to domains whose spontaneous polarization direction is parallel to the film surface (film facet), and c-domains refer to domains whose spontaneous polarization direction is perpendicular to the film surface (film facet). The coexistence structure of these two domains is called the a / c domain structure.

[0036] Specifically, the barium titanate sol precursor prepared by S100, with the stabilizing effect of the chelating agent and the aging process, avoids particle agglomeration and ensures the uniformity of film composition, thereby solving the performance fluctuation problem caused by the uneven composition of traditional films; the S200 spin coating process is simple to operate and low in cost, and is more suitable for large-scale mass production than the traditional vapor deposition method. Moreover, the step-by-step processing of preheating and crystallization can effectively reduce the internal stress and defects of the film and improve the adhesion between the film and the substrate; the S300 annealing treatment, by controlling the temperature and holding time, induces the (001) orientation, reduces the light scattering loss of the film to below 0.5dB / cm, and optimizes the a / c domain ratio, giving the film excellent domain structure reversibility. By using a continuous process from S100 to S300, the resulting barium titanate thin film possesses a high thermo-optic coefficient (twice that of traditional silicon-based materials), low optical loss, and high stability. This solves the technical bottlenecks of disordered orientation, poor domain structure reversibility, and high fabrication cost of traditional barium titanate thin films. It provides a high-performance core material for the fabrication of low-power, high-stability electro-optic modulator phase-shifting units, meeting the integrated application needs of multiple fields such as optical communication and optical sensing.

[0037] It should be noted that this application does not specifically limit the type of substrate, and commonly used substrate materials suitable for sol-gel spin coating processes can be selected.

[0038] Before spin coating, the substrate needs to be pretreated. The pretreatment process includes: ultrasonically cleaning the substrate in acetone, ethanol and deionized water in sequence. This step-by-step ultrasonic cleaning can effectively remove oil, dust and other impurities and surface oxide layer attached to the substrate surface. After cleaning, nitrogen is used to dry the substrate surface to ensure that there are no residual water stains, the cleanliness meets the standard and the flatness is good.

[0039] In some embodiments provided in this application, the barium titanate thin film has a (001) orientation and contains an a-domain and a c-domain structure that can reversibly switch with temperature. This preferred (001) orientation enables the thin film grains to be arranged in a regular manner, which can reduce light scattering loss, while the reversible switching characteristic of the a / c domains can ensure that it can achieve rapid and stable refractive index control, providing a structural basis for efficient thermo-optical phase shifting.

[0040] In some embodiments provided in this application, the thickness of the barium titanate film is 100~500 nm. This specific thickness range ensures that the film possesses both good mechanical stability and excellent thermo-optical modulation effects.

[0041] In some embodiments provided in this application, the titanium source includes tetrabutyl titanate, the barium source includes barium acetate, the solvent includes ethylene glycol methyl ether, and the chelating agent includes acetylacetone glacial acetate. By using the above combination of raw materials, the chelating effect of acetylacetone glacial acetate can be utilized to inhibit the excessively rapid hydrolysis of titanium ions, ensuring the stability of the precursor solution.

[0042] In some embodiments provided in this application, the molar ratio of barium in the barium source to titanium in the titanium source is 1:(1.0~1.1). Limiting the molar ratio of barium to titanium within the above range can effectively compensate for the slight volatilization of barium during the preparation process and ensure the accuracy of the stoichiometry of the barium titanate film.

[0043] In some embodiments provided in this application, the preparation process of the barium titanate sol precursor includes: slowly adding a titanium source dropwise into a solvent in a certain proportion, stirring, adding a chelating agent for chelation treatment, then adding a barium source solution dissolved in the solvent dropwise while continuously stirring; subsequently adding an appropriate amount of deionized water for hydrolysis reaction, and aging at room temperature to obtain a barium titanate sol precursor with a concentration of 0.1-0.5 mol / L. Through stepwise feeding, thorough stirring, and room temperature aging, the components can be uniformly mixed to form a stable sol system, avoiding particle agglomeration and laying the foundation for the subsequent preparation of films with good uniformity.

[0044] In some embodiments provided in this application, the parameters of the spin coating process are: rotation speed 3000 r / min, spin coating time 30s; after spin coating, the barium titanate film is placed on a hot stage and preheated at 200-300℃ for 8-10min to remove the solvent, thus completing one spin coating process; then, a crystallization treatment is performed at 500-600℃ for 10-30min to adjust the film thickness to 100-500nm.

[0045] In some embodiments provided in this application, the specific process of the annealing treatment is as follows: the barium titanate film is transferred to a tube furnace and heated to 600-800°C at a heating rate of 5°C / min in an oxygen atmosphere, held for 5-30 minutes, and then naturally cooled to room temperature. The oxygen atmosphere can prevent oxygen defects in the film at high temperatures, ensuring the chemical stability of barium titanate; the slow heating rate can avoid cracking of the film due to thermal stress; the specific annealing temperature and holding time can control the a / c domain ratio of the (001) oriented film, which is beneficial to the formation of a c-domain-dominated reversible domain structure, providing a guarantee for the realization of low-power thermo-optical phase shift.

[0046] Secondly, this application provides a barium titanate thin film, which is prepared by the method described above.

[0047] In this embodiment, the barium titanate film is prepared by a sol-gel spin-coating method and controlled by a specific annealing process to form a microstructure with (001) preferred orientation and c domain dominance. This not only ensures the uniformity of the film composition and the compactness of the structure, but also endows it with unique reversible a / c domain switching characteristics, providing material support for thermo-optical phase shift applications.

[0048] Thirdly, this application provides an electro-optic modulator phase-shifting unit 100, such as... Figure 2 As shown, the electro-optic modulator phase shift unit 100 includes: Substrate 10; A platinum electrode layer 20 is disposed on the substrate 10; A lanthanum nickelate buffer layer 30 is disposed on the side of the platinum electrode layer 20 away from the substrate 10; A phase-shifting functional layer 40 is disposed on the side of the lanthanum nickelate buffer layer 30 away from the platinum electrode layer 20; The phase-shifting functional layer 40 includes the aforementioned barium titanate thin film.

[0049] In this embodiment, a structurally stable electro-optic modulator phase-shifting unit 100 can be obtained by stacking a substrate 10, a platinum electrode layer 20, a lanthanum nickelate buffer layer 30, and a phase-shifting functional layer 40. The phase-shifting functional layer 40 is a barium titanate (BTO) thin film, prepared using the aforementioned method, and has a preferred (001) crystal plane orientation and a reversibly switchable a / c domain structure. The (001) orientation of this barium titanate thin film and the a / c domain ratio controlled by the annealing process can reduce scattering loss during light transmission and fully utilize the thermo-optical effect of the barium titanate thin film, ensuring the stability and reliability of phase-shifting modulation.

[0050] In some embodiments provided in this application, the electro-optic modulator phase-shifting unit 100 further includes a heating unit disposed in the adjacent region of the phase-shifting functional layer 40, for providing temperature control to the phase-shifting functional layer 40. The heating unit is preferably a micro-resistance heating unit. By adjusting the temperature of the micro-heating unit (25-50℃), the a / c domains of the BTO thin film are reversibly switched, allowing the thermo-optical effect of the barium titanate thin film to be fully utilized, ensuring the stability and reliability of the phase-shifting control.

[0051] In some embodiments provided in this application, the operating band of the electro-optic modulator phase shift unit 100 includes the C-band of 1530-1565nm, which is a commonly used band in the field of optical communication, enabling the modulator to be adapted to mainstream optical communication systems.

[0052] In some embodiments provided in this application, the electro-optic modulator phase-shifting unit 100 further includes an optical fiber coupling module and an optical power detection module. The optical fiber coupling module is used to achieve efficient coupling between the external optical signal and the optical waveguide, and the optical power detection module is used to monitor the optical signal power after phase shift in real time to ensure the stable operation of the device.

[0053] The technical solutions provided in this application will be described in detail below with reference to the embodiments.

[0054] Unless otherwise specified, all raw materials used in the examples and comparative examples are commercially available analytical grade reagents. The substrate is a silicon substrate (Si), the electrode is a platinum electrode (Pt), the buffer layer is a lanthanum nickelate buffer layer (LaNiO3), and the substrate pretreatment method is uniformly as follows: ultrasonic cleaning with acetone, ethanol, and deionized water for 10 minutes each, followed by drying with nitrogen gas for later use.

[0055] Example 1 Embodiment 1 of this application provides a barium titanate thin film and an electro-optic modulator phase-shifting unit based on the thin film. The specific preparation methods of both are as follows: 1. Preparation of barium titanate thin films: 1) Preparation of barium titanate sol precursor: Tetrabutyl titanate was selected as the titanium source, barium acetate as the barium source, ethylene glycol methyl ether as the solvent, and acetylacetone as the chelating agent, and they were mixed at a Ba:Ti molar ratio of 1:1.05. Tetrabutyl titanate was slowly added dropwise to ethylene glycol methyl ether (tetrabutyl titanate to ethylene glycol methyl ether volume ratio 1:4), and stirred at room temperature for 30 min. Then, acetylacetone (acetylacetone to tetrabutyl titanate molar ratio 1:1) was added for chelation for 10 min. Then, a barium acetate solution dissolved in ethylene glycol methyl ether (barium acetate concentration 0.2 mol / L) was added dropwise, and the mixture was stirred continuously for 2 h. Subsequently, an appropriate amount of deionized water was added at a deionized water to tetrabutyl titanate molar ratio of 2:1 for hydrolysis, and the mixture was aged at room temperature for 24 h to obtain a barium titanate sol precursor with a concentration of 0.2 mol / L.

[0056] 2) Preparation of barium titanate thin film: BTO sol precursor was drop-coated onto the substrate surface and then spin-coated at 3000 r / min for 30 s to form a uniform wet film (the dry film thickness of a single spin coating is about 100 nm). After spin coating, the film was placed on a hot stage and preheated at 250℃ for 10 min to remove the solvent. Then the temperature was raised to 550℃ and held for 20 min for crystallization treatment. This process of spin coating-preheating-crystallization was repeated three times to obtain a film thickness of about 300 nm.

[0057] 3) Annealing treatment: The substrate was transferred to a tube furnace and kept in an oxygen atmosphere (oxygen flow rate 50 sccm). The temperature was increased to 750°C at a rate of 5°C / min and held for 30 min. Then the heat source was turned off and the substrate was naturally cooled to room temperature in an oxygen atmosphere to obtain a barium titanate film with a thickness of 300 nm, (001) orientation and reversible a / c domain structure.

[0058] 2. Fabrication of the phase-shifting unit of the electro-optic modulator: The above-mentioned barium titanate thin film is used as the phase-shifting functional layer and integrated onto a substrate structure composed of a silicon substrate, a platinum electrode layer and a lanthanum nickelate buffer layer by spin coating. Micro-resistive heating units (material Ti / Pt, width 2μm) are fabricated in the adjacent areas on both sides of the phase-shifting functional layer. A single-mode fiber coupling module (coupling loss ≤0.5dB) and an optical power detection module (accuracy ±0.1dB) are assembled to form a complete phase-shifting unit of the electro-optic modulator.

[0059] Example 2 Same as Example 1, except that the concentration of barium titanate sol precursor is 0.1 mol / L and the Ba:Ti molar ratio is 1:1.0.

[0060] Example 3 Same as Example 1, except that the concentration of barium titanate sol precursor is 0.5 mol / L and the Ba:Ti molar ratio is 1:1.

[0061] Example 4 Same as Example 1, except that the spin coating cycle is 2 times and the film thickness is 200 nm.

[0062] Example 5 Same as Example 1, except that the spin coating cycle is 5 times and the film thickness is 500 nm.

[0063] Example 6 Same as Example 1, except that the preheating temperature is 200°C, the preheating time is 10 min, the crystallization temperature is 500°C, the crystallization time is 30 min, the annealing temperature is 600°C, and the holding time is 20 min.

[0064] Example 7 Similar to Example 1, except that the preheating temperature is 300°C and the preheating time is 8 min, the crystallization temperature is 600°C and the crystallization time is 10 min, the annealing temperature is 800°C and the holding time is 5 min.

[0065] Comparative Example 1 Comparative Example 1 provides a conventional silicon-based modulator.

[0066] Comparative Example 2 Same as Example 1, except that no annealing treatment was performed after the spin-coating-crystallization cycle.

[0067] Performance testing Performance tests were conducted on the modulators of Example 1 and Comparative Example 1. The test results show that the (001) oriented barium titanate thin film prepared in Example 1 using a sol-gel method combined with spin coating exhibits excellent a / c domain conversion capability; at a wavelength of 1550 nm, its modulation depth reaches 55%, its thermo-optic coefficient is twice that of Comparative Example 1, and its modulation power consumption is only 50% of that of Comparative Example 1, making it more suitable for low-power integrated applications. Furthermore, the light scattering loss of the barium titanate thin film obtained in Example 1 is reduced to below 0.5 dB / cm, and its domain structure reversibility is excellent; after 1000 cycles of testing within a temperature range of 25–50 °C, the modulation depth fluctuation is less than 3%; and the performance degradation rate after 1000 hours of continuous operation is less than 2%, meeting the reliability requirements of optical communication systems.

[0068] In the description of this specification, the references to terms such as "one embodiment / mode," "some embodiments / modes," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment / mode or example is included in at least one embodiment / mode or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment / mode or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments / modes or examples. Furthermore, without contradiction, those skilled in the art can combine and integrate the different embodiments / modes or examples described in this specification, as well as the features of different embodiments / modes or examples.

[0069] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element. In this application, "a plurality of" means at least two, such as two, three, etc., unless otherwise expressly specified.

[0070] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for preparing a barium titanate thin film for a phase-shifting unit of an electro-optic modulator, characterized in that, Includes the following steps: A barium titanate sol precursor is obtained by mixing a titanium source, a barium source, a solvent, and a chelating agent, followed by hydrolysis and aging. The barium titanate sol precursor is spin-coated onto the substrate surface, and after preheating and crystallization, a barium titanate thin film is formed. The barium titanate film is annealed to form a barium titanate film with a single orientation.

2. The preparation method according to claim 1, characterized in that, The barium titanate thin film has a (001) orientation and contains an α-domain and β-domain structure that can reversibly switch with temperature; and / or, The thickness of the barium titanate film is 100~500nm.

3. The preparation method according to claim 1, characterized in that, The titanium source includes tetrabutyl titanate; and / or, The barium source includes barium acetate; and / or, The solvent includes ethylene glycol methyl ether; and / or, The chelating agent includes acetylacetone; and / or, The molar ratio of barium in the barium source to titanium in the titanium source is 1:(1.0~1.1).

4. The preparation method according to claim 1, characterized in that, The concentration of the barium titanate sol precursor is 0.1-0.5 mol / L.

5. The preparation method according to claim 1, characterized in that, The preheating temperature is 200-300℃, and the time is 8-10 minutes; and / or, The crystallization process is carried out at a temperature of 500-600℃ for 10-30 minutes.

6. The preparation method according to claim 1, characterized in that, The annealing temperature is 600-800℃ and the time is 5-30 minutes.

7. A barium titanate thin film, characterized in that, The barium titanate thin film is prepared by the method described in any one of claims 1-6.

8. A phase-shifting unit for an electro-optic modulator, characterized in that, include: Substrate; A platinum electrode layer is disposed on the substrate; A lanthanum nickelate buffer layer is disposed on the side of the platinum electrode layer away from the substrate; A phase-shifting functional layer is disposed on the side of the lanthanum nickelate buffer layer away from the platinum electrode layer; The phase-shifting functional layer includes the barium titanate thin film as described in claim 7.

9. The phase-shifting unit of the electro-optic modulator according to claim 8, characterized in that, Also includes: A heating unit is disposed in the adjacent area of ​​the phase-shifting functional layer and is used to provide temperature regulation to the phase-shifting functional layer.

10. The phase-shifting unit of the electro-optic modulator according to claim 8 or 9, characterized in that, The operating wavelength of the phase-shifting unit of the electro-optic modulator includes the C-band of 1530-1565nm.

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