High-passband composite electro-optical modulator

Abstract

The invention provides a high-passband composite electro-optical modulator. The high-passband composite electro-optical modulator comprises a substrate, a buffer layer arranged on the substrate, an electro-optical material layer arranged on the buffer layer, an electrode layer arranged on the electro-optical material layer and a covering layer which is arranged on the electro-optical material layer and wraps the electrode layer. Wherein the electro-optical material layer comprises an electro-optical substrate arranged on the buffer layer and an electro-optical modulation layer integrally formed with the electro-optical substrate on the surface of the electro-optical substrate, and the electro-optical modulation layer comprises at least one grating coupling structure and an embedded strip-shaped waveguide arranged at an interval with the grating coupling structure; the electrode layer comprises two electrode plates which are arranged at intervals, and the two electrode plates are arranged on the electro-optical substrate and are distributed in a mirror symmetry mode relative to the central axis of the embedded strip-shaped waveguide. According to the high-passband composite electro-optical modulator provided by the invention, the high-efficiency coupling advantage of the grating, the low transmission loss characteristic of the embedded strip-shaped waveguide and the precise electric field regulation and control capability of the electrode layer are integrated, so that the transmission loss is reduced, and meanwhile, the modulation bandwidth is widened and the modulation depth is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor photoelectric detectors, and in particular to a high-passband composite electro-optical modulator and a preparation method thereof. Background Art

[0002] An electro-optic modulator (EOM) utilizes the electro-optic effect of an electro-optic crystal to electrically control the amplitude, phase, and polarization of light. The electro-optic effect states that when a voltage is applied to an EO crystal, the crystal's refractive index changes, resulting in changes in the properties of the light wave passing through the crystal, modulating the phase, amplitude, intensity, and polarization of the optical signal. Single-arm EO modulators primarily function as phase modulators. By applying an electrical signal to the electrodes, the electro-optic effect changes the waveguide's refractive index with respect to the incident light, thereby controlling the phase of light traveling through the waveguide.

[0003] To mitigate the losses caused by mode mismatch and effective refractive index mismatch between optical fibers and optical chip waveguides in electro-optical modulators (EOMs), various solutions have been proposed, such as grating coupling and embedded strip waveguide-electrode structures. While both structures possess significant advantages, they inevitably suffer from drawbacks that significantly impact EO modulator performance. Currently developed uniform grating couplers still suffer from relatively low coupling efficiency (maximum 50%). Compared to other coupling methods, such as end-face coupling, optical losses during transmission remain significant, impacting overall performance and limiting bandwidth. This is due to the inherent characteristics of grating structures, which limit bandwidth performance outside of certain wavelength ranges, making them unsuitable for multi-wavelength or broadband applications. Furthermore, the embedded strip waveguide-electrode structure currently exhibits limitations in optical signal input and output, particularly in coupling with free-space optical signals. This is due to the difficulty in matching the mode fields of the optical waveguide and the fiber, resulting in significant coupling losses.

[0004] Therefore, there is an urgent need for a high-passband composite electro-optical modulator to solve the above technical problems. Summary of the Invention

[0005] The object of the present invention is to provide a high-passband composite electro-optical modulator to solve the technical problems of the prior art electro-optical modulators, such as low coupling efficiency and difficulty in balancing modulation depth and bandwidth.

[0006] To solve the above technical problems, the present invention provides a high-passband composite electro-optical modulator, comprising: substrate; a buffer layer disposed on the substrate; an electro-optical material layer disposed on the buffer layer; an electrode layer disposed on the electro-optical material layer; and a covering layer, disposed on the electro-optical material layer and wrapping the electrode layer; Among them, the electro-optical material layer includes an electro-optical substrate arranged on the buffer layer and an electro-optical modulation layer integrally formed with the electro-optical substrate on its surface, the electro-optical modulation layer includes at least one grating coupling structure and an embedded strip waveguide spaced apart from the grating coupling structure; the electrode layer includes two electrode plates spaced apart, both electrode plates are arranged on the electro-optical substrate, and are distributed in a mirror-symmetrical manner about the central axis of the embedded strip waveguide.

[0007] Preferably, the high-passband composite electro-optical modulator includes a first type of sub-modulator and a second type of sub-modulator, the first incident light of the first type of sub-modulator is incident along the side of the grating coupling structure, and the second incident light in the second type of sub-modulator is incident along the side of the embedded strip waveguide.

[0008] Preferably, the grating parameters of the first type of sub-modulators are different from the grating parameters of the second type of sub-modulators.

[0009] Preferably, the electro-optic modulation layer includes two grating coupling structures, and the embedded strip waveguide is located between the two adjacent grating coupling structures.

[0010] Preferably, in the grating coupling structure, the period length is 0.3-2 μm, the duty cycle is 0.3-0.7, the depth is 50-500 nm, and the grating length is 50-500 nm.

[0011] Preferably, the thickness of the embedded strip waveguide is the same as the depth of the grating coupling structure.

[0012] Preferably, the embedded strip waveguide has a thickness of 100-500 nm, a length of 50-5000 μm, and a width of 0.5-5 μm.

[0013] Preferably, the thickness of the electrode plate is greater than the thickness of the embedded strip waveguide, the length of the electrode plate is less than the length of the embedded strip waveguide, and the width of the electrode plate is less than the width of the embedded strip waveguide.

[0014] Preferably, the material of the electro-optical material layer includes BaTiO 3 or LiNbO 3 , and the material of the electrode layer includes any one of Cu, Pt, Ag and Au.

[0015] Preferably, the material of the substrate includes Si, the material of the buffer layer includes any one of MgO, SiO 2 , Al 2 O 3 and SrTiO 3 , and the material of the cover layer includes SiO 2 or silicon nitride.

[0016] The beneficial effects of the present invention are as follows: Different from the prior art, the present invention provides a high-passband composite electro-optical modulator, comprising a substrate, a buffer layer arranged on the substrate, an electro-optical material layer arranged on the buffer layer, an electrode layer arranged on the electro-optical material layer, and a covering layer arranged on the electro-optical material layer and wrapping the electrode layer; wherein the electro-optical material layer comprises an electro-optical base arranged on the buffer layer and an electro-optical modulation layer integrally formed with the electro-optical base on its surface, the electro-optical modulation layer comprising at least one grating coupling structure and an embedded strip waveguide spaced apart from the grating coupling structure; the electrode layer comprises two electrode plates spaced apart, both electrode plates being arranged on the electro-optical base and distributed in a mirror-symmetrical manner about the central axis of the embedded strip waveguide. The high-passband composite electro-optical modulator provided by the present invention can accurately match the optical signal mode by utilizing the periodic optical field coupling characteristics of the grating coupling structure, thereby significantly reducing the injection loss of light from free space to the waveguide; at the same time, through the combination of the embedded strip waveguide and the mirror-symmetrical electrode plate, the uniformity of the refractive index modulation of the electro-optical material is enhanced through the symmetrical electric field distribution of the electrode plate on the central axis of the waveguide; in addition, the integrated composite architecture of "grating coupling structure-embedded strip waveguide-electrode layer" reduces the interface reflection loss between the structures, and the protection of the electrode layer by the covering layer reduces the performance fluctuation caused by environmental interference; finally, the high-passband composite electro-optical modulator provided by the present invention integrates the efficient coupling advantages of the grating, the low transmission loss characteristics of the embedded strip waveguide and the precise electric field control capability of the electrode layer, thereby reducing the transmission loss while simultaneously achieving the broadening of the modulation bandwidth and the improvement of the modulation depth, making it suitable for high-speed, high-bandwidth optical communication and optical signal processing applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 A schematic cross-sectional view of the high-passband composite electro-optical modulator provided in Example 1 of the present invention; Figure 2 A top view of the high-passband composite electro-optic modulator provided in Example 1 of the present invention without a covering layer; Figure 3 A schematic cross-sectional view of the high-passband composite electro-optical modulator provided in Example 2 of the present invention; Figure 4 A schematic cross-sectional view of the high-passband composite electro-optical modulator provided in Example 3 of the present invention; In the accompanying drawings: 100—high-passband composite electro-optic modulator; 10—substrate; 20—buffer layer; 30—electro-optic material layer; 31—electro-optic base; 32—electro-optic modulation layer; 321—grating coupling structure; 322—embedded strip waveguide; 40—electrode layer; 41—electrode layer; 50—covering layer. DETAILED DESCRIPTION

[0018] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0019] To address the technical challenges of existing high-passband composite electro-optical modulators, which suffer from low coupling efficiency and difficulty balancing modulation depth and bandwidth, the present invention leverages the unique advantages and inherent bottlenecks of both the grating coupling structure and the embedded strip waveguide-electrode structure in electro-optical modulation. By combining these two waveguide structures, a novel "grating-waveguide-electrode composite modulation structure" is constructed. This structure reduces lightwave transmission losses in the modulator, increases modulation bandwidth and depth, and ultimately achieves a synergistic effect between efficient optical coupling and electro-optical modulation. Furthermore, by optimizing the parameters of the composite modulation structure, the stability and reliability of the modulator can be further improved, making it suitable for high-speed, high-bandwidth optical communications and optical signal processing applications.

[0020] The technical solution of this application is now described in conjunction with specific embodiments.

[0021] Example 1: See also Figure 1 and Figure 2 The high-passband composite electro-optic modulator 100 provided in the first embodiment includes a substrate 10, a buffer layer 20 disposed on the substrate 10, an electro-optic material layer 30 disposed on the buffer layer 20, an electrode layer 40 disposed on the electro-optic material layer 30, and a cover layer 50 disposed on the electro-optic material layer 30 and wrapping the electrode layer 40. Among them, the electro-optical material layer 30 includes an electro-optical substrate 31 arranged on the buffer layer 20 and an electro-optical modulation layer 32 integrally formed on its surface with the electro-optical substrate 31, and the electro-optical modulation layer 32 includes at least one grating coupling structure 321 and an embedded strip waveguide 322 spaced apart from the grating coupling structure 321; the electrode layer 40 includes two spaced-apart electrode plates 41, both of which are arranged on the electro-optical substrate 31 and are distributed in a mirror-symmetrical manner about the central axis of the embedded strip waveguide 322.

[0022] The high-passband composite electro-optic modulator 100 provided in this embodiment 1 has the following advantages: First, the electro-optic material layer 30 adopts the design of "electro-optic substrate 31 + electro-optic modulation layer 32 integrally formed therewith", which avoids the interface defects caused by traditional layered preparation and reduces the scattering loss of light transmitted between layers; second, the interval arrangement of the grating coupling structure 321 and the embedded strip waveguide 322 in the electro-optic modulation layer 32 not only utilizes the periodic structure of the grating to achieve efficient coupling input of the optical signal, but also reduces the attenuation of light in the modulation path through the continuous transmission characteristics of the embedded strip waveguide 322. , which solves the contradiction between "coupling efficiency" and "transmission loss" in a single structure; secondly, the two electrode plates 41 of the electrode layer 40 are mirror-symmetrical about the central axis of the embedded strip waveguide 322, which can form a uniform and intensity-controllable transverse electric field in the waveguide area, and cooperate with the electro-optical effect of the electro-optical material to significantly improve the modulation depth of the optical signal; finally, the design of the covering layer 50 wrapping the electrode layer 40, on the one hand, isolates the interference of the external environment on the electrode (such as humidity, impurities), and on the other hand, reduces the mechanical friction loss between the electrode and other structures through physical protection, thereby improving the long-term working stability of the device. In summary, this structure achieves the unity of low transmission loss, high modulation efficiency and high reliability through the combination of inter-layer integration, functional unit collaboration and protection design, meeting the stringent requirements of high-speed optical communication scenarios for device performance.

[0023] In this first embodiment, the substrate 10 is made of Si. As a mature semiconductor material, Si exhibits high crystallinity, good mechanical stability, and excellent thermal conductivity, providing a solid support base for the entire modulator structure. Si is naturally compatible with the material combination of the subsequent buffer layer 20 (e.g., silicon dioxide). High-quality epitaxial growth of the substrate 10 and buffer layer 20 can be achieved using the established CMOS (Complementary Metal-Oxide-Semiconductor) process, reducing structural defects caused by interlayer stress and indirectly reducing light reflection losses at the interface between the substrate 10 and buffer layer 20. Furthermore, the high thermal conductivity of the Si substrate 10 helps to quickly dissipate Joule heat generated during electrode operation, preventing the impact of localized overheating on electro-optical material properties (e.g., refractive index stability). This, in conjunction with the protective effect of the capping layer 50, enhances the device's thermal stability.

[0024] In Example 1, buffer layer 20 is an oxide such as MgO, SiO2, Al2O3, or SrTiO3. SiO2 is used in this embodiment. This is because SiO2 offers better lattice matching, interfacial stress, and defect control with the substrate and BaTiO3 (BTO), significantly improving the electro-optical coefficient of BaTiO3 single-crystal thin films on silicon. This involves equipment such as magnetron sputtering, CVD (Chemical Vapor Deposition), and PLD (Pulsed Laser Deposition).

[0025] In this first embodiment, the electro-optic material layer 30 is made of BaTiO3 or LiNbO3. BaTiO3 is chosen for this embodiment because its theoretical electro-optic coefficient is over ten times that of LiNbO3, and its stability and ease of processing into waveguides make it a valuable research material for applications in ultra-high-speed, low-voltage electro-optic modulation devices. Electro-optic material layer 30 is fabricated using a magnetron sputtering machine or CVD deposition process. Furthermore, the design and fabrication of the grating coupling structure 321 and embedded strip waveguide 322 utilize a photolithography machine and an ion etcher.

[0026] Specifically, the electro-optical material layer 30 includes an electro-optical substrate 31 arranged on the buffer layer 20 and an electro-optical modulation layer 32 integrally formed with the electro-optical substrate 31 on its surface. The electro-optical modulation layer 32 includes at least one grating coupling structure 321 and an embedded strip waveguide 322 spaced apart from the grating coupling structure 321. The integrally formed design of the electro-optical substrate 31 and the electro-optical modulation layer 32 eliminates the lattice mismatch and impurity defects at the layered interface, minimizes the scattering and reflection losses in light transmission, and ensures the integrity of the long-distance transmission of the optical signal. The grating coupling structure 321 efficiently injects external optical signals through periodic light field regulation, solving the problem of high loss in traditional coupling methods, while the embedded strip waveguide 322 serves as a continuous transmission channel, reducing mode leakage with its uniform structure, ensuring stable transmission of the optical signal. At the same time, the integrated process simplifies the preparation process, avoids multi-step processing errors, and the consistent material thermal expansion characteristics enhance the mechanical stability of the device under temperature fluctuations, ultimately providing a low-loss, high-sensitivity, and long-life core structural support for the electro-optical modulator.

[0027] In this embodiment 1, the high-passband composite electro-optical modulator 100 is a first-type sub-modulator, and the first incident light of the first-type sub-modulator is incident laterally along the grating coupling structure 321; wherein, the first incident light enters the first-type sub-modulator and first passes through the grating coupling structure 321, which can significantly reduce the loss of the incident light wave in the coupling process and reduce the loss of the input signal, and then enters the embedded strip waveguide-electrode structure to realize efficient conversion and modulation between optical signals and electrical signals.

[0028] In the grating coupling structure 321 of this embodiment 1, the period length is 0.3-2 μm, the duty cycle is 0.3-0.7, the depth is 50-500 nm, and the grating length is 50-500 nm. The wide range of period and duty cycle coverage enables efficient coupling of multiple wavelengths of light by precisely matching different incident light wavelengths (e.g., short periods adapt to the near-infrared band, and long periods are compatible with mid-infrared signals), breaking through the bottleneck of the limited frequency band adaptation of a single period structure. The gradient design of the depth parameter (50-500 nm) It can flexibly adjust the interaction strength between the light field and the electro-optical material - deep gratings (such as 500nm) can enhance the light field binding ability, and cooperate with strong electric field control to significantly improve the modulation depth, while shallow gratings (such as 50nm) can reduce light scattering loss and adapt to low-loss transmission needs; and the length range of 50~500nm can balance the coupling efficiency and device integration. Long gratings (such as 500nm) reduce coupling loss by extending the light-grating action time, and short gratings (such as 50nm) reduce device size to meet the needs of high-density integration scenarios.

[0029] In the embedded strip waveguide 322 of this embodiment 1, the embedded strip waveguide 322 has a thickness of 100-500 nm, a length (parallel to the propagation direction of the incident light) of 50-5000 μm, and a width (perpendicular to the propagation direction of the incident light) of 0.5-5 μm. This thickness range satisfies single-mode transmission conditions (avoiding signal crosstalk caused by high-order mode excitation) and matches the depth of the grating coupling structure 321 (50-500 nm), ensuring a smooth mode transition when light enters the waveguide from the grating coupling structure 321 and reducing mode mismatch loss. This length range can be adapted to different modulation requirements. A long waveguide extends the interaction time between light and the electrode electric field to increase the modulation depth, while a short waveguide shortens signal transmission delay and is suitable for high-frequency modulation scenarios. The 0.5-5 μm width design ensures effective confinement of the light field within the waveguide (avoiding light leakage) while providing ample space for symmetrical electrode distribution, ensuring that the electric field generated by the electrodes uniformly covers the waveguide area and enhances electro-optical modulation efficiency. In addition, this size range is compatible with the lithography and etching accuracy of the CMOS process, reducing the difficulty of preparation. At the same time, it cooperates with the parameters of the grating coupling structure 321 to achieve low-loss connection from coupling to transmission of optical signals, laying a structural foundation for the wide-band adaptation and high-performance output of the modulator.

[0030] Specifically, the thickness of the embedded strip waveguide 322 is the same as the depth of the grating coupling structure 321; the precise matching of the two sizes makes the longitudinal distribution of the light field in the grating coupling area and the waveguide transmission area highly consistent, avoiding the sudden change of the light field mode due to the thickness difference, minimizing the mode conversion loss, and significantly improving the energy transfer efficiency of the optical signal from coupling to transmission.

[0031] In this embodiment 1, the electrode layer 40 includes two electrode plates 41 arranged at intervals, and the two electrode plates 41 are both arranged on the electro-optical substrate 31 and are distributed in a mirror-symmetrical manner about the central axis of the embedded strip waveguide 322; wherein, the symmetrically distributed electrode plates 41 can form a uniform and symmetrical transverse electric field in the embedded strip waveguide 322 area, ensuring that the electro-optical materials at different positions in the embedded strip waveguide 322 are subjected to consistent electric field regulation, avoiding modulation signal distortion caused by uneven electric field distribution, and greatly improving the uniformity of modulation depth; at the same time, the symmetrical structure maximizes the electric field intensity at the central axis of the embedded strip waveguide 322, precisely overlapping with the light field confinement area of ​​the embedded strip waveguide 322, enhancing the interaction efficiency between light and electric field, and solving the problem of low electric field utilization of traditional asymmetric electrodes. In addition, this layout and the dimensional adaptability (such as width matching) of the embedded strip waveguide 322 and the grating coupling structure 321 can achieve precise alignment of the electrode and the waveguide through the same set of lithography references, reducing the impact of process deviations on the electric field coverage effect, and coordinating with the "waveguide-grating size matching" design to further ensure the full-link performance stability of the electro-optical modulator from optical coupling to electro-optical control.

[0032] Specifically, the thickness of the electrode plate 41 is greater than the thickness of the embedded strip waveguide 322, the length of the electrode plate 41 is less than the length of the embedded strip waveguide 322, and the width of the electrode plate 41 is less than the width of the embedded strip waveguide 322; wherein, the greater thickness of the electrode plate 41 can enhance the current carrying capacity, reduce the resistance loss of the electrode itself, and at the same time provide a stronger electric field constraint for the embedded strip waveguide 322 area, ensuring that the electric field is concentrated on the core transmission area of ​​the waveguide, avoiding the decrease in modulation efficiency caused by excessive diffusion of the electric field to the substrate 10; the length of the electrode plate 41 is less than the length of the embedded strip waveguide 322, so that the electric field action range accurately covers the embedded strip waveguide 322. The effective modulation section of the waveguide 322 reduces the electric field interference in the non-modulation area, shortens the ineffective overlapping part of the electrode and the waveguide, reduces the delay effect of the parasitic capacitance on the high-frequency modulation signal, and adapts to the high-speed modulation requirements; the width of the electrode plate 41 is smaller than the width of the embedded strip waveguide 322, which reserves space for the light field constraint at the edge of the waveguide, avoids light leakage loss caused by the electrode being too wide to squeeze the light field distribution, and at the same time ensures the symmetry accuracy of the electrode plate 41 about the central axis of the embedded strip waveguide 322, enhances the uniformity of the electric field distribution, and finally achieves a balance between efficient electric field regulation and low-loss transmission of optical signals, further improving the sensitivity and high-speed response performance of the electro-optical modulator.

[0033] In Example 1, the material of electrode layer 40 includes any one of Cu, Pt, Ag, and Au. In this embodiment, the patterned structure of electrode layer 40 is formed using ALD (Atomic Layer Deposition) or MS (Molecular Beam Epitaxy) combined with lift-off technology. Copper was chosen in Example 1 because of its excellent electrical conductivity, processability, corrosion resistance, and affordability.

[0034] In Example 1, the material of the covering layer 50 includes SiO2 or silicon nitride; wherein, the covering layer 50 ensures the device performance in the high-passband composite electro-optical modulator 100 through three core functions: optically, the differentiated refractive indices of SiO2 and silicon nitride are used to adapt the grating and waveguide structures of the two types of sub-modulators, thereby reducing the optical signal loss in a wide frequency band and constraining the light field; electrically, it acts as an insulating isolation layer to stabilize the electrode state to maintain the uniformity of the modulation performance; structurally, it is compatible with the multi-layer preparation process and prevents structural deformation at high and low temperatures through stress regulation, ultimately providing key support for the device's wide frequency band coverage, high-sensitivity modulation and long-term stable operation. Example 2: See also Figure 3 , Figure 3This is a schematic cross-sectional view of the high-passband composite electro-optical modulator 100 provided in Example 2 of the present invention. The structure of the high-passband composite electro-optical modulator 100 provided in Example 2 is substantially the same as that of the high-passband composite electro-optical modulator 100 provided in Example 1, with the only difference being that: In this embodiment 2, the high-passband composite electro-optical modulator 100 is a second-type sub-modulator, and the second incident light in the second-type sub-modulator is incident laterally along the embedded strip waveguide 322; wherein, the second incident light first passes through the embedded strip waveguide 322 to achieve optical signal pre-constraint and low-loss transmission, ensuring that the light field stably enters the modulation link, and then uses the differentiated parameters of the grating coupling mechanism to accurately shape the transmitted optical signal and efficiently couple it to the external optical path, thereby solving the high loss problem at the output end and adapting to the output requirements of a specific frequency band.

[0035] Specifically, the grating parameters of the second type of sub-modulator are different from those of the first type of sub-modulator, and the electric field parameters generated between the two electrode plates 41 of the second type of sub-modulator are also different from those of the first type of sub-modulator.

[0036] Furthermore, the high-passband hybrid electro-optic modulator 100 achieves significant advantages through the differentiated design of two types of sub-modulators. The first and second types of sub-modulators, respectively, employ a grating coupling structure 321 and an embedded strip waveguide 322 for lateral incidence. Combined with differentiated configurations of grating parameters (such as period and duty cycle), these sub-modulators can specifically match incident light of different wavelengths or modes, broadening the device's adaptability to optical signals. Furthermore, the electric field parameters (such as intensity and distribution) generated by the electrode plates 41 in the two types of sub-modulators differ. This differentiated electric field control optimizes the refractive index modulation effect of the electro-optic material, enhancing the modulation depth at a single wavelength while enabling independent and efficient modulation of signals across multiple frequency bands. This dual-dimensional "structure-electric field" differentiated design, combined with the low-loss characteristics of the integrated electro-optic material layer 30 and the stable transmission advantages of the waveguide, ultimately achieves low-loss transmission and highly sensitive modulation across a wide frequency band, meeting the requirements for parallel processing of multiple signals in high-speed optical communications.

[0037] Example 3: See also Figure 4 , Figure 4 This is a schematic diagram of the cross-sectional structure of the high-passband composite electro-optical modulator 100 provided in Example 3 of the present invention; the structure of the high-passband composite electro-optical modulator 100 provided in this Example 3 is substantially the same as the structure of the high-passband composite electro-optical modulator 100 provided in this Example 1, with the only difference being that the electro-optical modulation layer 32 includes two grating coupling structures 321, and the embedded strip waveguide 322 is located between the two adjacent grating coupling structures 321.

[0038] Specifically, a complete optical signal link of "input-transmission-output" is formed between the two adjacent grating coupling structures 321 and the embedded strip waveguide 322. The front grating coupling structure 321 can efficiently couple the external incident light into the embedded strip waveguide 322, and the rear grating coupling structure 321 accurately outputs the modulated optical signal to the external optical path (such as optical fiber). Through the differentiated parameters of the dual gratings (such as period and duty cycle to adapt to input / output requirements), low-loss transmission of the entire optical signal link is achieved, avoiding the loss of coupling efficiency caused by the input and output multiplexing of the traditional single grating coupling structure 321; secondly, the embedded strip waveguide 322 is located between the dual grating coupling structures 321, so that the optical signal The signal can fully interact with the electric field generated by the electrode during transmission. Combined with the one-piece molding structure of the embedded strip waveguide 322 and the grating coupling structure 321, the light field mode transition is smooth in the process of coupling-transmission-recoupling, reducing the scattering loss caused by structural mutations, and ensuring the stability of the optical signal intensity during the modulation process; at the same time, this compact layout strengthens the synergistic effect of the two types of gratings and waveguides. The front grating optimizes the light injection efficiency, the rear grating improves the light output accuracy, and the middle waveguide ensures the modulation uniformity. It is compatible with the one-piece molding process of the electro-optical modulation layer 32, further simplifying the structural design and improving the device integration, providing structural support for the wide-band adaptation and efficient modulation of the high-passband composite modulator.

[0039] To address the problems and difficulties in existing electro-optic modulator structures, the present invention adopts the following innovative designs: 1. Device structure optimization: This application uses a grating-waveguide-electrode composite modulation structure. As is well known, the grating coupling structure 321 has advantages such as easy alignment, flexible I / O port (Input / Output Port) placement, and significant reduction in light wave loss during the coupling process. However, the currently developed uniform structure grating couplers still have problems such as low coupling efficiency (maximum only 50%) and small coupling bandwidth. The close contact between the waveguide and the electrode in the embedded strip waveguide-electrode structure, as well as the ability to optimize the matching between the waveguide mode and the electrode electric field, enables it to provide strong light field confinement and a high refractive index difference, achieving efficient conversion and modulation between optical and electrical signals. However, the current embedded strip waveguide-electrode structure has certain limitations in terms of optical signal input and output, especially in terms of coupling with free-space optical signals. The grating-waveguide-electrode composite modulation structure can reduce the transmission loss of light waves in the modulator, improve the modulation bandwidth and modulation depth, as well as the input and output optical signals, and ultimately achieve the synergistic effect of efficient light coupling and electro-optical modulation. It is of great significance to promote the design and optimization of miniaturized, highly integrated and high-performance modulators, and is expected to provide strong support for technological innovation and application expansion in the field of optoelectronics.

[0040] 2. Process Optimization: The present invention utilizes CMOS technology to study the influence of BaTiO3 thin film etching parameters on the structural characteristics of the BaTiO3 / buffer layer 20 ridge waveguide structure, and to study the influence of magnetron sputtering technology, MOCVD (Metal-Organic Chemical Vapor Deposition), photolithography, and etching process parameters on the structural morphology of the SiO2 layer serving as the cover layer 50 and the embedded electrode groove. The present invention also explores the role of annealing, polishing, and surface loading in eliminating defects within the crystal and on the surface / interface. The present invention also carries out matching of the film thicknesses and structural design of the cladding (Si or SiO2, etc.) / core layer-BaTiO3 / upper cladding (air or SiO2, etc.) substrate, thereby obtaining an effective method for improving the electro-optic coefficient of the BaTiO3 single crystal thin film and the refractive index difference between the BaTiO3 / cladding.

[0041] Furthermore, the present invention also utilizes the ALD method (or MS method) combined with the stripping technology to form metal electrodes such as Al (or ITO) to prepare BaTiO3-based embedded strip waveguide-electrode structures with different ridge widths, ridge heights, and different electrode widths and spacings to ensure good contact between the electrode plate 41 and the BaTiO3 film, and that the electrode pattern matches the waveguide structure; a reasonable electrode shape, position, and size can be designed based on the electro-optic coefficient of BaTiO3 to optimize the electric field distribution in the waveguide and improve the electro-optic modulation efficiency; the high-level waveguide cross-sectional characteristics of the waveguide ridge can be characterized and analyzed by a step profiler and a SEM (Scanning Electron Microscope), and the optical fiber-waveguide coupling platform can be used to characterize the test structure optical waveguide guided mode mode and insertion loss and other characteristics.

[0042] Furthermore, the present invention utilizes methods such as ion beam etching and CMP (Chemical Mechanical Polishing) to modify the surface of the substrate 10 (or buffer layer 20), and combines this with in-situ monitoring technology (such as laser interferometry) during the epitaxial growth of the thin film to achieve lattice matching, interface stress, and defect control, thereby improving the electro-optic coefficient of silicon-based BaTiO3 single crystal thin films and breaking through the bottleneck of their electro-optic modulation performance. This is a beneficial exploration at the forefront of electro-optic modulator technology.

[0043] The present invention combines the previously improved BaTiO3 epitaxial process to study the effects of design parameters, structures, and materials such as the grating, waveguide, and electrode in the grating coupling structure 321 and the embedded strip waveguide-electrode structure on the coupling efficiency, lightwave transmission, and electro-optical modulation efficiency of the incident light. Combining the advantages of the two structures, a new BaTiO3-based grating-waveguide-electrode composite modulation structure is designed and manufactured. Through optical simulation and structural test result fitting, the matching of the composite modulation structure's process and structural design is optimized, and a high-performance electro-optical modulator unit is prepared that can achieve the synergistic effect of efficient light coupling and electro-optical modulation. Compared with the existing technology, the present invention has the following advantages: In a first aspect, the high-passband composite electro-optical modulator 100 provided by the present invention has a grating-waveguide-electrode composite modulation structure, which can reduce the transmission loss of light waves in the electro-optical modulator, improve the modulation bandwidth and modulation depth, and ultimately achieve the synergistic effect of efficient light coupling and electro-optical modulation; Secondly, the electro-optic material layer 30 of the high-passband composite electro-optic modulator 100 provided by the present invention uses BaTiO3 material, which can break through the bottleneck of its electro-optic modulation performance by improving the electro-optic coefficient of the BaTiO3 single crystal thin film. It can also achieve lattice matching, interface stress and defect control by adjusting the refractive index difference between BaTiO3 and the buffer layer 20 or the cover layer 50; Thirdly, the high-passband composite electro-optical modulator 100 provided by the present invention can further improve the stability and reliability of the modulator by optimizing the parameters of the composite modulation structure, making it suitable for high-speed, high-bandwidth optical communications and optical signal processing applications. The grating-waveguide-electrode composite modulation structure enables efficient coupling of optical signals and the synergistic effect of electro-optical modulation. This is of great significance for promoting the design and optimization of miniaturized, highly integrated, and high-performance modulators, and is expected to provide strong support for technological innovation and application expansion in the field of optoelectronics.

[0044] It should be noted that the above embodiments all belong to the same inventive concept, and the description of each embodiment has its own focus. For any details not described in individual embodiments, reference may be made to the description in other embodiments.

[0045] The above embodiments merely illustrate the implementation methods of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent. It should be noted that a person skilled in the art could make various modifications and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention shall be determined by the appended claims.

Claims

1. A high-passband composite electro-optical modulator, characterized in that: include: substrate; a buffer layer, disposed on the substrate; an electro-optical material layer, disposed on the buffer layer; an electrode layer, disposed on the electro-optical material layer; as well as a covering layer, disposed on the electro-optical material layer and wrapping the electrode layer; Among them, the electro-optical material layer includes an electro-optical substrate arranged on the buffer layer and an electro-optical modulation layer integrally formed with the electro-optical substrate on its surface, the electro-optical modulation layer includes at least one grating coupling structure and an embedded strip waveguide spaced apart from the grating coupling structure; the electrode layer includes two electrode plates spaced apart, both of which are arranged on the electro-optical substrate and are distributed in a mirror-symmetrical manner about the central axis of the embedded strip waveguide.

2. The high-passband composite electro-optical modulator according to claim 1, characterized in that: The high-passband composite electro-optical modulator includes a first type of sub-modulator and a second type of sub-modulator, the first incident light of the first type of sub-modulator is incident along the side of the grating coupling structure, and the second incident light in the second type of sub-modulator is incident along the side of the embedded strip waveguide.

3. The high-passband composite electro-optical modulator according to claim 2, characterized in that: The grating parameters of the first type of sub-modulator are different from the grating parameters of the second type of sub-modulator.

4. The high-passband composite electro-optic modulator according to claim 1, characterized in that: The electro-optic modulation layer includes two grating coupling structures, and the embedded strip waveguide is located between two adjacent grating coupling structures.

5. The high-passband composite electro-optic modulator according to claim 1, characterized in that: In the grating coupling structure, the period length is 0.3-2 μm, the duty cycle is 0.3-0.7, the depth is 50-500 nm, and the grating length is 50-500 nm.

6. The high-passband composite electro-optic modulator according to claim 5, characterized in that: The thickness of the embedded strip waveguide is the same as the depth of the grating coupling structure.

7. The high-passband composite electro-optic modulator according to claim 1, characterized in that: The embedded strip waveguide has a thickness of 100-500 nm, a length of 50-5000 μm, and a width of 0.5-5 μm.

8. The high-passband composite electro-optic modulator according to claim 7, characterized in that: The thickness of the electrode plate is greater than the thickness of the embedded strip waveguide, the length of the electrode plate is smaller than the length of the embedded strip waveguide, and the width of the electrode plate is smaller than the width of the embedded strip waveguide.

9. The high-passband composite electro-optic modulator according to claim 1, characterized in that: The material of the electro-optical material layer includes BaTiO3 or LiNbO3, and the material of the electrode layer includes any one of Cu, Pt, Ag and Au.

10. The high-passband composite electro-optic modulator according to claim 1, characterized in that: The material of the substrate includes Si, the material of the buffer layer includes any one of MgO, SiO2, Al2O3 and SrTiO3, and the material of the cover layer includes SiO2 or silicon nitride.

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