Ultra-wideband electro-optical modulator integrated with time domain and frequency domain equalization and preparation method of ultra-wideband electro-optical modulator

Abstract

The invention provides an ultra-wideband electro-optical modulator integrating time domain and frequency domain equalization and a preparation method thereof. The ultra-wideband electro-optical modulator comprises a silicon substrate, a silicon dioxide buried oxide layer, a silicon nitride waveguide, a lead zirconate titanate thin film waveguide, a first coplanar traveling wave electrode and a silicon dioxide embedded layer, the lead zirconate titanate film waveguides form two parallel arms, the first sections of the two parallel arms are positively polarized, the second sections of the two parallel arms are reversely polarized, and the silicon nitride waveguide layer is arranged in the section, connected with the second section, of the first sections; the first coplanar traveling wave electrode is used for transmitting a microwave signal; performing forward phase modulation on the optical signal in the forward polarization section based on the microwave signal, and performing reverse phase modulation on the optical signal in the reverse polarization section; the silicon nitride waveguide introduces time domain delay between a microwave signal and an optical signal; the microwave loss difference of forward phase modulation and reverse phase modulation of the optical signal is improved based on the time domain delay, so that high-frequency modulation response attenuation is compensated, and combined equalization of the time domain and the frequency domain is realized.

Description

Technical Field

[0001] This application relates to the fields of optoelectronic integration and optical communication technology, and more specifically, to an ultrawideband electro-optic modulator with integrated time-domain and frequency-domain equalization and its fabrication method. Background Technology

[0002] With the development of silicon photonics technology, on-chip high-speed modulators have become key devices in optical communication and optical interconnect systems. Traditional modulators based on silicon or silicon nitride waveguides mostly adopt the Mach-Zehnder structure, achieving light intensity control through phase modulation. However, due to the weak electro-optic effect and limited bandwidth, these devices are prone to problems such as reduced modulation depth and group delay mismatch under high-frequency conditions.

[0003] In recent years, hybrid integrated modulators fabricated using the strong electro-optic effect of lead zirconate titanate have attracted attention. These materials possess high electro-optic coefficients and good integrability. However, existing structures still suffer from problems such as insufficient speed matching between optical and microwave waves, phase distortion at high frequencies, and non-uniform frequency response, limiting further improvements in system bandwidth. Summary of the Invention

[0004] In view of this, this application provides an ultrawideband electro-optic modulator integrating time-domain and frequency-domain equalization and its fabrication method.

[0005] One aspect of this application provides an ultra-wideband electro-optic modulator with integrated time-domain and frequency-domain equalization. From bottom to top, the modulator comprises: a silicon substrate, a silicon dioxide buried oxide layer, a silicon nitride waveguide, a lead zirconate titanate thin-film waveguide, a first coplanar traveling-wave electrode, and a silicon dioxide buried layer. The lead zirconate titanate thin-film waveguide forms two parallel arms. A first segment of the two parallel arms is positively polarized, and a second segment is negatively polarized. The silicon nitride waveguide is disposed in the segment of the first segment that connects to the second segment. The first coplanar traveling-wave electrode is used to transmit micro-wave signals. The wave signal; the microwave signal is used to perform forward phase modulation of the optical signal in the forward polarization section of the lead zirconate titanate thin film waveguide, and reverse phase modulation of the optical signal in the reverse polarization section of the lead zirconate titanate thin film waveguide; the silicon nitride waveguide is coupled to the lead zirconate titanate thin film waveguide to introduce a controlled time-domain delay between the microwave signal and the optical signal after forward phase modulation; during reverse phase modulation, based on the time-domain delay, the difference in microwave loss between forward and reverse phase modulation of the optical signal is increased, thereby compensating for the attenuation of high-frequency modulation response, and finally achieving joint equalization in the time and frequency domains to expand the modulation bandwidth.

[0006] According to an embodiment of this application, it further includes: a second coplanar traveling wave electrode disposed on a second segment of the lead zirconate titanate thin film waveguide, the second coplanar traveling wave electrode being covered by a silicon dioxide buried layer; the second coplanar traveling wave electrode is used to apply a reverse voltage to the second segment of the lead zirconate titanate thin film waveguide for reverse polarization before the ultra-wideband electro-optic modulator is activated; the first coplanar traveling wave electrode is also used to apply a forward voltage to the lead zirconate titanate thin film waveguide for forward polarization before the ultra-wideband electro-optic modulator is activated.

[0007] According to an embodiment of this application, the two parallel arms are single-mode optical waveguide structures.

[0008] According to embodiments of this application, the material of the lead zirconate titanate thin-film waveguide is lead zirconate titanate or lanthanum-doped lead zirconate titanate.

[0009] According to an embodiment of this application, the first coplanar traveling wave electrode and the second coplanar traveling wave electrode are impedance matched with the external microwave transmission line.

[0010] Another aspect of this application provides a fabrication method for an ultrawideband electro-optic modulator with integrated time-domain and frequency-domain equalization as described in any of the preceding aspects, comprising: forming a silicon dioxide buried oxide layer on a silicon substrate; depositing a silicon nitride waveguide layer on the silicon dioxide buried oxide layer and patterning it by photolithography and etching processes to form a silicon nitride waveguide; locally depositing and patterning a lead zirconate titanate thin film on a predetermined section of two parallel arms to form a lead zirconate titanate thin film waveguide including two parallel arms; depositing and patterning a first metal layer on the lead zirconate titanate thin film waveguide to form a first coplanar traveling wave electrode; and depositing a silicon dioxide buried layer on a substrate on which the first coplanar traveling wave electrode is formed.

[0011] According to embodiments of this application, the step of depositing a lead zirconate titanate thin film further includes doping the lead zirconate titanate thin film with lanthanides to form a lanthanum-doped lead zirconate titanate thin film.

[0012] According to an embodiment of this application, in the step of forming two parallel arms, the two parallel arms are fabricated into a single-mode optical waveguide structure by controlling the photolithography and etching processes.

[0013] According to an embodiment of this application, the method further includes: depositing a silicon dioxide isolation layer on a silicon nitride waveguide layer before depositing a lead zirconate titanate thin film waveguide.

[0014] According to an embodiment of this application, the method further includes: depositing and patterning a second metal layer downstream of a lead zirconate titanate thin film waveguide to form a second coplanar traveling wave electrode before depositing a silicon dioxide embedded layer.

[0015] According to the embodiments of this application, because the technology of integrating the time-domain and frequency-domain equalizers and the electro-optic modulator on the chip is adopted, the technical problems of system complexity, long signal path, and easy reflection and distortion caused by the reliance on external equalization circuits in traditional modulators are at least partially overcome. Thus, the technical effects of simplifying peripheral circuits, shortening signal path, reducing signal reflection and distortion, and realizing device miniaturization are achieved.

[0016] According to the embodiments of this application, because a technology based on a silicon substrate, a silicon dioxide buried oxide layer and a silicon nitride waveguide layer, and hybrid integration with a lead zirconate titanate thin film is adopted, the technical problems of the incompatibility between strong electro-optic materials and standard silicon photonics processes, as well as the difficulty in large-scale integration of modulators, are at least partially overcome. This achieves the technical effect of ensuring that the device is compatible with mainstream silicon photonics processes and is suitable for large-scale, high-performance integration on silicon-based photonic chips.

[0017] According to the embodiments of this application, because a joint equalization technique is adopted that introduces a controlled time-domain delay through the speed mismatch region and uses the reverse modulation region to perform phase compensation for the forward modulation, the technical problem of bandwidth limitation caused by high-frequency modulation response attenuation in traditional traveling wave electrode modulators is at least partially overcome, thereby achieving the technical effect of significantly widening the modulator's 3 dB bandwidth and enabling it to break through the traditional rate limit. Attached Figure Description

[0018] The above and other objects, features and advantages of this application will become clearer from the following description of embodiments with reference to the accompanying drawings, in which:

[0019] Figure 1 This schematically illustrates a planar view of an ultrawideband electro-optic modulator with integrated time-domain and frequency-domain equalization according to an embodiment of this application.

[0020] Figure 2 This illustration schematically shows a three-dimensional diagram of an ultrawideband electro-optic modulator with integrated time-domain and frequency-domain equalization according to an embodiment of this application.

[0021] Figure 3 The schematic diagram illustrates a process flow diagram of a preparation method according to an embodiment of this application.

[0022] Explanation of reference numerals in the attached figures:

[0023] 1-Basic modulation region;

[0024] 2- Forward modulation region;

[0025] 3-Velocity mismatch zone;

[0026] 4-Reverse modulation region;

[0027] 5 - First coplanar traveling wave electrode;

[0028] Lead zirconate titanate thin film waveguide;

[0029] 7-Silicon nitride waveguide;

[0030] 8-Second coplanar traveling wave electrode. Detailed Implementation

[0031] The embodiments of this application will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of this application. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of this application for ease of explanation. However, it will be apparent that one or more embodiments may be implemented without these specific details. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concepts of this application.

[0032] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of this application. The terms “comprising,” “including,” etc., as used herein indicate the presence of the stated features, steps, operations, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, or components.

[0033] All terms used herein (including technical and scientific terms) have the meanings commonly understood by those skilled in the art, unless otherwise defined. It should be noted that the terms used herein are to be interpreted in a manner consistent with the context of this specification, and not in an idealized or overly rigid way.

[0034] When using expressions such as "at least one of A, B and C", they should generally be interpreted in accordance with the meaning that is commonly understood by those skilled in the art (e.g., "a system having at least one of A, B and C" should include, but is not limited to, a system having A alone, a system having B alone, a system having C alone, a system having A and B, a system having A and C, a system having B and C, and / or a system having A, B and C, etc.).

[0035] This application provides an ultrawideband electro-optic modulator with integrated time-domain and frequency-domain equalization, comprising, from bottom to top, a silicon substrate, a silicon dioxide buried oxide layer, a silicon nitride waveguide 7, a lead zirconate titanate thin film waveguide 6, a first coplanar traveling wave electrode layer 5, a second coplanar traveling wave electrode layer 8, and a silicon dioxide buried layer. The silicon dioxide buried oxide layer is formed on the silicon substrate; the silicon nitride waveguide 7 is formed on the silicon dioxide buried oxide layer; the lead zirconate titanate thin film waveguide 6 constitutes two parallel arms of a Mach-Zehnder interferometer, with a first segment of the two parallel arms being positively polarized and a second segment being negatively polarized; the silicon nitride waveguide 7 is disposed in the segment of the first segment that connects to the second segment; the first coplanar traveling wave electrode 5 is disposed on the lead zirconate titanate thin film waveguide 6; the second coplanar traveling wave electrode 8 is disposed on the second segment downstream of the lead zirconate titanate thin film waveguide 6; and the silicon dioxide buried layer covers the first coplanar traveling wave electrode 5 and the second coplanar traveling wave electrode 8.

[0036] The first coplanar traveling wave electrode is used to transmit microwave signals. The microwave signals are used to perform forward phase modulation of the optical signal in the forward polarization section of the lead zirconate titanate thin film waveguide and reverse phase modulation of the optical signal in the reverse polarization section of the lead zirconate titanate thin film waveguide. The silicon nitride waveguide is coupled to the lead zirconate titanate thin film waveguide by an evanescent wave to introduce a controlled time-domain delay between the microwave signal and the optical signal after forward phase modulation. When performing reverse phase modulation, the high-frequency modulation response attenuation caused by the difference in microwave loss between forward and reverse phase modulation is compensated based on the time-domain delay, thereby achieving joint equalization in the time and frequency domains to expand the modulation bandwidth.

[0037] In this embodiment, the lead zirconate titanate thin-film waveguide 6 is polarized by a first coplanar traveling-wave electrode 5 and a second coplanar traveling-wave electrode 8. Before the ultra-wideband electro-optic modulator is activated, a forward voltage is applied to the lead zirconate titanate thin-film waveguide 6 through the first coplanar traveling-wave electrode 5 for forward polarization. The second coplanar traveling-wave electrode 8 is used to apply a reverse voltage to the second segment of the lead zirconate titanate thin-film waveguide 6 for reverse polarization before the ultra-wideband electro-optic modulator is activated.

[0038] See Figure 1 and Figure 2The ultra-wideband electro-optic modulator with integrated time-domain and frequency-domain equalization provided in this application can be divided into a basic modulation region 1, a forward modulation region 2, a velocity mismatch region 3, and a reverse modulation region 4. The basic modulation region 1, forward modulation region 2, and velocity mismatch region 3 are located in the first segment of the lead zirconate titanate thin-film waveguide; the reverse modulation region 4 is located in the second segment of the lead zirconate titanate thin-film waveguide. The basic modulation region 1 is used to achieve primary phase modulation of the optical signal; the velocity mismatch region 3 is used to introduce controlled velocity mismatch between the microwave signal and the optical signal to achieve time-domain delay; the forward modulation region 2 and the reverse modulation region 4 respectively achieve phase modulation and reverse phase compensation to achieve joint equalization of the time and frequency domains under high-frequency conditions, thereby expanding the device bandwidth and improving frequency response characteristics. It should be noted that the basic modulation region 1 and the forward modulation region 2 are in the same continuous region in physical space, and their modulation effect on the optical signal is also consistent. This application... Figure 1 The division of regions in this process is actually a functional distinction of the modulator. On the one hand, the modulator can realize the basic phase modulation function as described in the basic modulation region 1. On the other hand, the modulator can achieve joint equalization in the time domain and frequency domain based on the synergistic effect of the forward modulation region 2, the speed mismatch region 3 and the reverse modulation region 4 to expand the modulation bandwidth.

[0039] In this embodiment, the forward modulation region 2 and the reverse modulation region 4 achieve opposite polarities through secondary polarization using two layers of metal electrodes (a first coplanar traveling wave electrode 5 and a second coplanar traveling wave electrode 8). After polarization on the first coplanar traveling wave electrode 5, an opposite voltage is applied to the second coplanar traveling wave electrode 8 for polarization, achieving a reverse polarization effect in the modulator's reverse region. The lengths of the forward modulation region 2 and the reverse modulation region 4 can be set to 500-1000 micrometers. When the electrode microwave loss of the reverse modulation region 4 is higher than that of the forward modulation region 2 at high frequencies, the system achieves phase compensation at the frequency domain end through reverse phase modulation, keeping the overall response of the modulator balanced in the high-frequency range, thereby effectively expanding the modulation bandwidth.

[0040] This application aims to address the performance degradation problem of modulators at high frequencies by introducing an equalization mechanism. It should be understood that the "high frequency" mentioned in this application is not an absolute numerical limit, but rather refers to the frequency band where the modulation depth of traditional modulators begins to decrease significantly due to factors such as microwave loss and speed mismatch. This is also the frequency band in which the phase compensation mechanism of the inverse modulation region 4 in this application can effectively produce an equalization effect.

[0041] In this embodiment, the two parallel arms are single-mode optical waveguide structures to achieve low-loss optical propagation and stable mode constraint.

[0042] In this embodiment, the lead zirconate titanate thin film waveguide 6 can be made of lead zirconate titanate or lanthanum-doped lead zirconate titanate to improve ferroelectric stability and enhance the electro-optic coefficient, thereby increasing the modulation depth.

[0043] In this embodiment, the first coplanar traveling wave electrode 5 and the second coplanar traveling wave electrode 8 can be made of gold, silver, aluminum, or copper. The geometry and spacing of the electrodes are optimized to ensure efficient transmission of high-frequency electrical signals and low reflection characteristics.

[0044] In this embodiment, the lead zirconate titanate thin-film waveguide 6 and the underlying silicon nitride waveguide 7 exchange optical power via evanescent wave coupling. A velocity mismatch region 3 is established between the lead zirconate titanate thin-film waveguide 6 and the silicon nitride waveguide 7 with a specific coupling length and spacing. Light is coupled from the lead zirconate titanate thin-film waveguide 6 to the silicon nitride waveguide 7 via the evanescent wave coupling structure. By adjusting the length of the silicon nitride waveguide, a controllable group velocity mismatch is generated, causing a time-domain delay between the microwave and the light wave during propagation.

[0045] Furthermore, the geometry of the first coplanar traveling wave electrode 5 and the second coplanar traveling wave electrode 8 is optimized to match the impedance of the external microwave transmission line. This impedance matching design minimizes microwave signal reflection during input and transmission, ensuring that high-frequency electrical signals can be efficiently fed into and act on the optical waveguide, which is a key guarantee for achieving ultra-wideband modulation performance.

[0046] This application also provides a method for fabricating an ultrawideband electro-optic modulator with integrated time-domain and frequency-domain equalization. A flowchart of this method is shown below. Figure 3 .

[0047] like Figure 3 As shown, the fabrication method of the ultra-wideband electro-optic modulator with integrated time-domain and frequency-domain equalization includes the following steps.

[0048] The first step is to form a buried oxide layer of silicon dioxide (SiO2) on a silicon substrate (Si) by thermal oxidation.

[0049] The second step involves depositing a silicon nitride waveguide layer (SiN) on a silicon dioxide buried oxide layer using plasma-enhanced chemical vapor deposition or low-pressure chemical vapor deposition, and then patterning it using photolithography and etching processes to form the silicon nitride waveguide 7.

[0050] In the embodiments of this application, the silicon nitride waveguide layer is deposited using plasma-enhanced chemical vapor deposition or low-pressure chemical vapor deposition, with a deposition temperature of approximately 300–800°C and a thickness ranging from 300–500 nm. It is defined as a single-mode waveguide structure by photolithography and dry etching processes to achieve low-loss light propagation and stable mode confinement.

[0051] The third step involves depositing a silicon dioxide isolation layer on the silicon nitride waveguide 7 before depositing the lead zirconate titanate thin film waveguide 6 (PZT) to modulate the photoelectric field distribution.

[0052] The fourth step involves depositing and patterning lead zirconate titanate thin films locally on the preset sections of the two parallel arms using sol-gel or magnetron sputtering methods, and obtaining a ferroelectric crystal structure after high-temperature annealing. The lead zirconate titanate thin film waveguide 6, including two parallel arms, is then formed by photolithography etching.

[0053] In the sol-gel process, organometallic precursors of lead, zirconium, and titanium are first dissolved and uniformly stirred to form a precursor solution. After spin-coating deposition, the solution is annealed and crystallized at 600–700℃ to obtain a perovskite structure with ferroelectric properties. In the magnetron sputtering process, lead zirconate titanate thin-film waveguide 6 ceramic target is used to deposit a thin film in an oxygen / argon mixed atmosphere. After deposition, the film is annealed to improve crystallinity and electro-optic response performance.

[0054] When depositing lead zirconate titanate films, lanthanide elements can be incorporated to form lanthanum-doped lead zirconate titanate films, thereby improving ferroelectric stability and enhancing the electro-optic coefficient, thus increasing the modulation depth.

[0055] The fifth step is to deposit and pattern the first metal layer on the lead zirconate titanate thin film waveguide 6 to form the first coplanar traveling wave electrode 5.

[0056] The sixth step involves depositing and patterning a second metal layer downstream of the lead zirconate titanate thin film waveguide 6 to form the second coplanar traveling wave electrode 8.

[0057] The first and second metal layers are made of gold, silver, aluminum, or copper and formed through photolithography and metal deposition processes. Figure 3 In the illustrated embodiment, aluminum (Al) is used as the metal material. In the traveling wave electrode design, a metal film of approximately 1 μm thickness is deposited using electron beam evaporation or sputtering, followed by photolithography and ion beam etching to form a coplanar waveguide structure with a characteristic impedance of 50 Ω. The electrode geometry and spacing are optimized to ensure efficient transmission of high-frequency electrical signals and low reflection characteristics.

[0058] Step 7: On the substrate on which the first coplanar traveling wave electrode 5 and the second coplanar traveling wave electrode 8 are formed, a silicon dioxide embedded layer is deposited by chemical vapor deposition.

[0059] Therefore, by integrating time-domain and frequency-domain equalization structures into a lead zirconate titanate thin-film modulator, high-speed, broadband, and low-loss optical signal modulation characteristics are achieved. This structure is compatible with silicon photonics platforms and can be widely used in optical communication and high-speed optical signal processing.

[0060] Based on the above technical solutions, the ultra-wideband electro-optic modulator with integrated time-domain and frequency-domain equalization of this application requires equalization at the driving circuit or system end, unlike traditional modulators which require equalization at the driving circuit or system end. This application integrates the equalization function into the modulator itself, reducing the complexity of the external circuit, reducing the signal path length, and reducing reflection and distortion.

[0061] The overall structure of the integrated time-domain and frequency-domain balanced ultrawideband electro-optic modulator of this application is compatible with mainstream silicon photonics processes and can be massively integrated on Si-based photonic chips. Lead zirconate titanate films can be deposited through sol-gel and sputtering processes, exhibiting controllable thickness and good crystal orientation.

[0062] The ultra-wideband electro-optic modulator with integrated time-domain and frequency-domain equalization proposed in this application can significantly broaden the modulation bandwidth. Through the coupling of the velocity mismatch region 3 and the inverse modulation region 4, phase compensation of the optical field at high frequencies is achieved, thereby overcoming the bandwidth limitation of traditional traveling-wave electrode modulators. It can effectively improve the bandwidth by 3 dB, breaking through the traditional rate limit.

[0063] The embodiments of this application have been described above. However, these embodiments are merely illustrative and not intended to limit the scope of this application. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. Without departing from the scope of this application, those skilled in the art can make various substitutions and modifications, all of which should fall within the scope of this application.

Claims

1. An ultra-wideband electro-optic modulator integrating time-domain and frequency-domain equalization, characterized in that, From bottom to top, it comprises: a silicon substrate, a silicon dioxide buried oxygen layer, a silicon nitride waveguide, a lead zirconate titanate thin film waveguide, a first coplanar traveling wave electrode and a silicon dioxide embedding layer. The lead zirconate titanate thin film waveguide comprises two parallel arms, a first section of the two parallel arms is forward-polarized, and a second section of the two parallel arms is reverse-polarized, and the silicon nitride waveguide is arranged in a section of the first section and adjacent to the second section. The first coplanar traveling wave electrode is used for transmitting a microwave signal, the microwave signal is used for forward phase modulation of an optical signal in the forward-polarized section of the lead zirconate titanate thin film waveguide and reverse phase modulation of the optical signal in the reverse-polarized section of the lead zirconate titanate thin film waveguide, the silicon nitride waveguide is used for introducing a controlled time-domain delay between the microwave signal and the optical signal after the forward phase modulation, and the microwave loss difference between the forward phase modulation and the reverse phase modulation of the optical signal is improved based on the time-domain delay when the reverse phase modulation is performed, so as to compensate for high-frequency modulation response attenuation, and finally realize joint equalization in time domain and frequency domain to expand the modulation bandwidth.

2. The electro-optic modulator of claim 1, wherein, Further comprising: A second coplanar traveling wave electrode is arranged on the second section of the lead zirconate titanate thin film waveguide, and the silicon dioxide embedding layer covers the second coplanar traveling wave electrode. The second coplanar traveling wave electrode is used for applying a reverse voltage to the second section of the lead zirconate titanate thin film waveguide to perform reverse polarization before the ultra-wideband electro-optical modulator is enabled. The first coplanar traveling wave electrode is also used for applying a forward voltage to the lead zirconate titanate thin film waveguide to perform forward polarization before the ultra-wideband electro-optical modulator is enabled.

3. The electro-optic modulator of claim 1, wherein, The two parallel arms are single-mode optical waveguide structures.

4. The electro-optic modulator of claim 1, wherein, The material of the lead zirconate titanate thin film waveguide is lead zirconate titanate or lanthanum-doped lead zirconate titanate.

5. The electro-optic modulator of claim 1, wherein, The first coplanar traveling wave electrode and the second coplanar traveling wave electrode are impedance-matched with an external microwave transmission line.

6. A method of manufacture for an integrated time and frequency domain equalized electro- optical modulator according to any one of claims 1 to 5, characterized in that, Comprising: forming a silicon dioxide buried oxygen layer on a silicon substrate; depositing a silicon nitride waveguide layer on the silicon dioxide buried oxygen layer, patterning by photolithography and etching process to form a silicon nitride waveguide; depositing and patterning a lead zirconate titanate thin film on the two parallel arms to form a lead zirconate titanate thin film waveguide comprising the two parallel arms; depositing and patterning a first metal layer on the lead zirconate titanate thin film waveguide to form a first coplanar traveling wave electrode; depositing a silicon dioxide embedding layer on the substrate on which the first coplanar traveling wave electrode is formed.

7. The preparation method according to claim 6, characterized in that, In the step of depositing the lead zirconate titanate thin film, lanthanide elements are doped into the lead zirconate titanate thin film to form a lanthanum-doped lead zirconate titanate thin film.

8. The preparation method according to claim 6, characterized in that, In the step of forming the two parallel arms, the two parallel arms are prepared as single-mode optical waveguide structures by controlling the photolithography and etching process.

9. The preparation method according to claim 6, characterized in that, The method further comprises: depositing a silicon dioxide isolation layer on the silicon nitride waveguide layer before depositing the lead zirconate titanate thin film waveguide.

10. The method of claim 6, wherein, The method further comprises: depositing and patterning a second metal layer downstream of the lead zirconate titanate thin film waveguide to form a second coplanar traveling wave electrode before depositing the silicon dioxide embedding layer.

Images