An electro-optical modulator heterogeneously integrated with silicon and ferroelectric materials

Abstract

An electro-optical modulator heterogeneously integrated with silicon-based and ferroelectric materials belongs to the field of optical modulator technology. From bottom to top, it consists of a silicon-based substrate, a lower cladding, an optical waveguide core layer, and an upper cladding layer. The optical waveguide core layer is an MZI-type structure based on a Bessel-type multimode interference coupler, consisting of an upper optical waveguide core layer and a lower optical waveguide core layer. Both the upper and lower optical waveguide core layers are enclosed in the upper cladding layer, and the upper and lower optical waveguide core layers are separated by the upper cladding layer. The present invention uses ferroelectric materials such as lead zirconate titanate, lanthanum-modified lead zirconate titanate, and barium titanate as the upper optical waveguide core layer, and uses silicon nitride or silicon with a higher refractive index as the lower optical waveguide core layer. This not only helps reduce driving voltage and realize multifunctional, low-power, and large-scale integrated photonic devices, but also simplifies the device preparation process and has a compact structure, achieving a smaller device size and lower excess loss at a larger bandwidth.

Description

Technical Field

[0001] The present invention belongs to the technical field of optical modulators, and in particular relates to an electro-optical modulator heterogeneously integrated with a silicon base and a ferroelectric material. Background Art

[0002] In recent years, with the rapid development of high-tech technologies such as AI, 5G communications, big data, and the Internet of Things, the communications market has entered a new chapter. As a core component of optical modules, electro-optical modulators play a key role in optical communication networks. As market demand evolves, higher requirements are being placed on the bandwidth, transmission rate, and signal quality of optical modules.

[0003] Thanks to its compatibility with microelectronics' CMOS processes and relatively mature fabrication processes, silicon-based photonics platforms have become widely researched and have achieved large-scale integration. However, due to the inherent limitations of silicon-based materials, they lack first-order electro-optical properties (the Pockels effect), making it difficult to fabricate low-power, high-speed, and small-sized electro-optic modulators. To leverage the advantages of silicon-based photonics while achieving efficient modulation performance, heterogeneous integrated electro-optic modulators can be fabricated by integrating other electro-optical materials.

[0004] Compared with traditional electro-optical materials such as lithium niobate, lanthanum-modified lead zirconate titanate (Pb 1-x La x (Zr y Ti 1-y )O3, referred to as PLZT), lead zirconate titanate (PbZr x Ti 1-x New ferroelectric materials such as zirconium zirconia oxide (PZT) and barium titanate (BaTiO3, BTO) have an electro-optic coefficient of >100pm / V, making them ideal materials for making electro-optic modulators. These materials can be used to develop high-quality electro-optic devices, such as electro-optic modulators and electro-optic switches, and have good prospects in the fields of optical communications and optical interconnection. Summary of the Invention

[0005] In order to achieve a low-power, high-performance electro-optic modulator, the present invention combines the mature and advanced preparation technology of the silicon-based photonic platform with high-performance electro-optical materials, overcoming the problem of the incompatibility between ferroelectric materials and the silicon-based platform, and ultimately obtains a low-power, high-performance electro-optic modulator that heterogeneously integrates silicon-based and ferroelectric materials.

[0006] The electro-optical modulator heterogeneously integrated with silicon-based and ferroelectric materials described in the present invention is composed of a silicon-based substrate, a lower cladding, an optical waveguide core layer, and an upper cladding layer from bottom to top. The optical waveguide core layer adopts a three-dimensional integration method and is a two-layer structure of an upper optical waveguide core layer and a lower optical waveguide core layer; the upper optical waveguide core layer and the lower optical waveguide core layer are both coated in the upper cladding layer, and the upper optical waveguide core layer and the lower optical waveguide core layer are separated by the upper cladding layer; as shown in the attached figure, Figure 1 As shown, the optical waveguide core layer is an MZI type structure, which is composed of an input straight waveguide (1) located in the lower optical waveguide core layer, a 1×2 input Bezier-shaped multimode interference coupler (Multimode Interference, abbreviated as MMI) (2), a first input S-bend waveguide (3), a second input S-bend waveguide (4), a first input lower layer wedge-shaped waveguide (5), a second input lower layer wedge-shaped waveguide (6), a first output lower layer wedge-shaped waveguide (16), a second output lower layer wedge-shaped waveguide (17), a first output S-bend waveguide (18), a second output S-bend waveguide (19), a 2×1 output Bezier-shaped multimode interference coupler (20), an output straight waveguide (2 The optical waveguide core layer comprises a first input upper layer wedge-shaped waveguide (7), a second input upper layer wedge-shaped waveguide (8), a first modulation straight waveguide (9), a second modulation straight waveguide (10), a first output upper layer wedge-shaped waveguide (14), and a second output upper layer wedge-shaped waveguide (15); the input straight waveguide (1) and the output straight waveguide (21) are located on the same straight line, and the upper optical waveguide core layer and the lower optical waveguide core layer are both symmetrical structures with respect to the input straight waveguide (1) and the output straight waveguide (21).

[0007] In the lower optical waveguide core layer, the input straight waveguide (1) is connected to the input end of the input 1×2 Bessel-shaped multimode interference coupler (2), the input ends of the first input S-bend waveguide (3) and the second input S-bend waveguide (4) are respectively connected to the two output ends of the 1×2 input Bessel-shaped multimode interference coupler (2), the output end of the first input S-bend waveguide (3) is connected to the first input lower layer wedge-shaped waveguide (5), and the output end of the second input S-bend waveguide (4) is connected to the second input lower layer wedge-shaped waveguide (6); The first output lower layer wedge-shaped waveguide (16) is connected to the input end of the first output S-bend waveguide (18), the second output lower layer wedge-shaped waveguide (17) is connected to the input end of the second output S-bend waveguide (19), the output ends of the first output S-bend waveguide (18) and the second output S-bend waveguide (19) are respectively connected to the two input ends of a 2×1 output Bessel-shaped multimode interference coupler (20), and the output end of the 2×1 output Bessel-shaped multimode interference coupler (20) is connected to an output straight waveguide (21).

[0008] In the upper optical waveguide core layer, a first modulation straight waveguide (9) and a second modulation straight waveguide (10) are arranged in parallel as modulation arms; a first input upper layer wedge-shaped waveguide (7) is connected to the input end of the first modulation straight waveguide (9); and the output end of the first modulation straight waveguide (9) is connected to the first output upper layer wedge-shaped waveguide (14); a second input upper layer wedge-shaped waveguide (8) is connected to the input end of the second modulation straight waveguide (10); and the output end of the second modulation straight waveguide (10) is connected to the second output upper layer wedge-shaped waveguide (15).

[0009] All wedge-shaped waveguides have the same size. The first input lower layer wedge-shaped waveguide (5), the second input lower layer wedge-shaped waveguide (6), the first output lower layer wedge-shaped waveguide (16), and the second output lower layer wedge-shaped waveguide (17) in the lower optical waveguide core layer respectively form upper and lower parallel interlayer coupling structures with the first input upper layer wedge-shaped waveguide (7), the second input upper layer wedge-shaped waveguide (8), the first output upper layer wedge-shaped waveguide (14), and the second output upper layer wedge-shaped waveguide (15) in the upper waveguide core layer.

[0010] In the upper optical waveguide core layer, a first grounding metal electrode (11), a signal metal electrode (13), and a second grounding metal electrode (12) are respectively arranged on the outside of the first modulation straight waveguide (9), between the first modulation straight waveguide (9) and the second modulation straight waveguide (10), and on the outside of the second modulation straight waveguide (10).

[0011] As attached Figure 2 As shown, they are Figure 1 Schematic diagram of the cross section at the a-a' position, b-b' position and c-c' position. Figure 2 As shown in (a), the device is composed of a silicon-based substrate (22), a lower cladding layer (23), a lower optical waveguide core layer (25), and an upper cladding layer (24) from bottom to top. At this time, the lower optical waveguide core layer (25) corresponds to Figure 1 The input straight waveguide (1) in Figure 2 As shown in (b), the device is composed of a silicon-based substrate (22), a lower cladding layer (23), a lower optical waveguide core layer (25), a metal electrode layer (27), an upper optical waveguide core layer (26), and an upper cladding layer (24) from bottom to top. At this time, the lower optical waveguide core layer (25) corresponds to Figure 1 The first input lower layer wedge-shaped waveguide (5) and the second input lower layer wedge-shaped waveguide (6), the metal electrode layer (27) correspond to Figure 1 The first grounding metal electrode (11), the signal metal electrode (13) and the second grounding metal electrode (12), the upper optical waveguide core layer (26) correspond to Figure 1 The first input upper layer wedge-shaped waveguide (7) and the second input upper layer wedge-shaped waveguide (8) in the embodiment; Figure 2As shown in (c), the device is composed of a silicon-based substrate (22), a lower cladding layer (23), a metal electrode layer (27), an upper optical waveguide core layer (26), and an upper cladding layer (24) from bottom to top. The metal electrode layer (27) corresponds to Figure 1 The first grounding metal electrode (11), the signal metal electrode (13) and the second grounding metal electrode (12), the upper optical waveguide core layer (26) correspond to Figure 1 The first modulated straight waveguide (9) and the second modulated straight waveguide (10) are arranged in a first optical waveguide. The lower cladding layer (23) and the upper cladding layer (24) are made of silicon dioxide with a low refractive index; the lower optical waveguide core layer (25) uses silicon nitride or silicon with a higher refractive index; the upper optical waveguide core layer (26) uses a ferroelectric material, which can be one of lead zirconate titanate, lanthanum-modified lead zirconate titanate, and barium titanate; the metal electrode layer (27) can be one of aluminum, gold, silver, tungsten, and titanium.

[0012] In order to obtain a smaller device size and lower additional loss under a larger bandwidth, the structure of the 1×2 input Bessel-shaped multimode interference coupler (2) of the present invention is as shown in the attached figure. Figure 3 As shown, the invention comprises a Bessel input straight waveguide (28) as an input end, a Bessel-shaped multimode interference region (29), a first Bessel-shaped output wedge-shaped converter (30) and a second Bessel-shaped output wedge-shaped converter (31), a first Bessel output straight waveguide (32) and a second Bessel output straight waveguide (33) as output ends; the Bessel input straight waveguide (28) is connected to the input straight waveguide (1), the first Bessel-shaped output wedge-shaped converter (30), the first Bessel output straight waveguide (32) and the second input S-bend waveguide (4) are connected in sequence, the second Bessel-shaped output wedge-shaped converter (31), the second Bessel output straight waveguide (33) and the first input S-bend waveguide (3) are connected in sequence, The 1×2 input Bessel-shaped multimode interference coupler (2) is a symmetrical structure about the central axis of the Bessel input straight waveguide (28), the Bessel bending curves on both sides of the Bessel-shaped multimode interference region (29) are symmetrical about the central axis of the Bessel input straight waveguide (28), and the Bessel bending curves of the first Bessel-shaped output wedge converter (30) and the second Bessel-shaped output wedge converter (31) are symmetrical about the central axis of the first Bessel-shaped output wedge converter (30) and the second Bessel-shaped output wedge converter (31); the 2×1 output Bessel-shaped multimode interference coupler (20) and the 1×2 input Bessel-shaped multimode interference coupler (2) are symmetrical about the central axis of the electro-optic modulator ( Figure 1 The symmetrical structure of the c-c' position).

[0013] To leverage the excellent electro-optical modulation properties of ferroelectric materials, the present invention employs wedge-shaped waveguides for interlayer coupling, coupling light from the lower optical waveguide core layer into the upper optical waveguide core layer, where it is then electro-optically modulated by the ferroelectric material. The wedge-shaped waveguides in the upper and lower layers are identical in size and arranged in parallel, forming an interlayer coupling structure. (The so-called interlayer coupling structure, in addition to being identical in size and arranged in parallel, also has the same starting and ending positions; the lower wedge-shaped waveguide gradually narrows, while the upper wedge-shaped waveguide gradually widens.) This structure improves the efficiency of light coupling between layers.

[0014] The working principle of the electro-optic modulator of the present invention, which is heterogeneously integrated with silicon-based and ferroelectric materials, is as follows:

[0015] When the device is working, 1550nm light is input from the input straight waveguide (1) and then enters the 1×2 input Bessel-shaped multimode interference coupler (2). Due to the self-imaging principle of the multimode interference coupler, the light is divided into two lights with completely equal power in the multimode interference coupler, and outputted respectively by the first input S-bend waveguide (3) and the second input S-bend waveguide (4). Then, the light enters the first input lower layer wedge-shaped waveguide (5) and the second input lower layer wedge-shaped waveguide (6), and is gradually coupled into the first input upper layer wedge-shaped waveguide (7) and the second input upper layer wedge-shaped waveguide (8), and then enters the first modulation straight waveguide (9) and the second modulation straight waveguide (10). The first grounding metal electrode (11) and the second grounding metal electrode (12) are grounded at the same time, and a signal voltage is applied to the signal metal electrode (13). When the polarization directions of the modulation arms are different and the signal voltage is positive or negative, the refractive index of the first modulation straight waveguide (9) or the second modulation straight waveguide (10) changes due to the Pockels effect, causing a refractive index difference between the two modulation straight waveguides, and ultimately causing a phase difference in the light in the two modulation straight waveguides. The two beams of light with the phase difference then enter the first output upper layer wedge waveguide (14) and the second output upper layer wedge waveguide (15) at the output end respectively and gradually couple into the first output lower layer wedge waveguide (16) and the second output lower layer wedge waveguide (17) respectively, and then enter the 2×1 output Bessel-shaped multimode interference coupler (20) and finally output from the output straight waveguide (21), thereby achieving intensity modulation of the light beam.

[0016] Compared with the prior art, the innovation of the present invention is:

[0017] 1) The present invention uses ferroelectric materials such as lead zirconate titanate, lanthanum-modified lead zirconate titanate, and barium titanate for electro-optic modulation. Compared with traditional electro-optic materials, these materials have high electro-optic coefficients, which is beneficial for reducing driving voltage;

[0018] 2) The present invention heterogeneously integrates ferroelectric materials with high electro-optic coefficients with silicon-based photonic platforms, which is beneficial for realizing multifunctional, low-power, and large-scale integrated photonic devices;

[0019] 3) The present invention uses a three-dimensional integration method when performing heterogeneous integration of multi-layer waveguide materials. This method has a simple process and a compact structure, which is beneficial for realizing multifunctional, low-power, and large-scale integrated photonic devices;

[0020] 4) The present invention adopts a Bessel-type multimode interference coupler, which can achieve a smaller device size and lower additional loss under a larger bandwidth. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is a schematic diagram of the optical waveguide core structure of an electro-optical modulator heterogeneously integrated with silicon-based and ferroelectric materials according to the present invention;

[0022] Figure 2 This is a cross-sectional schematic diagram of an electro-optical modulator heterogeneously integrated with a silicon-based and ferroelectric material according to the present invention. Figure 2 (a) Figure 1 Schematic diagram of the cross section at the a-a' position, Figure 2 (b) Figure 1 Schematic diagram of the cross section at the b-b' position, Figure 2 (c) Figure 1 Schematic diagram of the cross section at the c-c' position;

[0023] Figure 3 Schematic diagram of the structure of the 1×2 input Bessel-type multimode interference coupler of the present invention;

[0024] Figure 4 This is a transmission spectrum diagram of the 1×2 input Bessel-shaped multimode interference coupler of the present invention;

[0025] Figure 5 This is a transmission light field diagram of the 1×2 input Bessel-shaped multimode interference coupler of the present invention;

[0026] Figure 6 This is a transmission spectrum diagram of the wedge-shaped waveguide of the present invention;

[0027] Figure 7 This is a transmission light field diagram of the wedge-shaped waveguide of the present invention;

[0028] Figure 8 Curves showing changes in modulation voltage and optical transmission loss over time for an electro-optical modulator heterogeneously integrated with silicon-based and ferroelectric materials according to the present invention;

[0029] Figure 9 This is a process flow chart of a silicon-based and ferroelectric material heterogeneously integrated electro-optical modulator according to the present invention. DETAILED DESCRIPTION

[0030] The following describes the embodiments of the present invention in detail in conjunction with the embodiments and accompanying drawings. The embodiments described below are not exhaustive. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. In this embodiment, the upper ferroelectric material is fully etched. In other embodiments, partial etching can be used to form a ridge waveguide.

[0031] In order to better describe and introduce this embodiment, some components in some drawings may be omitted, enlarged or reduced, and therefore the drawings may not represent the actual size of the device.

[0032] Example 1

[0033] The electro-optic modulator heterogeneously integrated with silicon-based and ferroelectric materials described in the present invention is composed of a silicon-based substrate, a lower cladding, an optical waveguide core layer, and an upper cladding layer from bottom to top. The optical waveguide core layer adopts a three-dimensional integration method and has a two-layer structure of an upper optical waveguide core layer and a lower optical waveguide core layer; the upper optical waveguide core layer and the lower optical waveguide core layer are both coated in the upper cladding layer, and the upper optical waveguide core layer and the lower optical waveguide core layer are separated by the upper cladding layer.

[0034] As attached Figure 1As shown, the optical waveguide core layer is an MZI type structure, which is composed of an input straight waveguide (1) located in the lower optical waveguide core layer, a 1×2 input Bezier-shaped multimode interference coupler (Multimode Interference, abbreviated as MMI) (2), a first input S-bend waveguide (3), a second input S-bend waveguide (4), a first input lower layer wedge-shaped waveguide (5), a second input lower layer wedge-shaped waveguide (6), a first output lower layer wedge-shaped waveguide (16), a second output lower layer wedge-shaped waveguide (17), a first output S-bend waveguide (18), a second output S-bend waveguide (19), a 2×1 output Bezier-shaped multimode interference coupler (20), an output straight waveguide (2 The optical waveguide core layer comprises a first input upper layer wedge-shaped waveguide (7), a second input upper layer wedge-shaped waveguide (8), a first modulation straight waveguide (9), a second modulation straight waveguide (10), a first output upper layer wedge-shaped waveguide (14), and a second output upper layer wedge-shaped waveguide (15); the input straight waveguide (1) and the output straight waveguide (21) are located on the same straight line, and the upper optical waveguide core layer and the lower optical waveguide core layer are symmetrical structures with respect to the input straight waveguide (1) and the output straight waveguide (21). The thickness of the upper optical waveguide core layer and the lower optical waveguide core layer are equal, set to 0.3 μm; the width of the input straight waveguide (1), the first input S-bend waveguide (3), the second input S-bend waveguide (4), the first output S-bend waveguide (18), the second output S-bend waveguide (19), the output straight waveguide (21), the first modulation straight waveguide (9), and the second modulation straight waveguide (10) are equal, set to 0.9 μm; the thickness of the upper cladding layer (24) between the upper optical waveguide core layer and the lower optical waveguide core layer is 0.2 μm.

[0035] Except for the wedge-shaped waveguide and the 1×2 input Bessel-shaped multimode interference coupler (2), there is no special requirement for the length of the remaining waveguides, as long as the normal connection between the various parts is ensured.

[0036] In the upper optical waveguide core layer, a first grounding metal electrode (11), a signal metal electrode (13), and a second grounding metal electrode (12) are respectively arranged parallel to each other on the outside of the first modulation straight waveguide (9), between the first modulation straight waveguide (9) and the second modulation straight waveguide (10), and on the outside of the second modulation straight waveguide (10). This embodiment uses rectangular ground-signal-ground electrodes, each of which has a width of 20 μm, a length of 5 mm, and a thickness of 400 nm.

[0037] As attached Figure 2As shown, the silicon-based substrate (22) can be made of one of silicon and silicon nitride. In this embodiment, silicon material is selected. The lower cladding layer (23) and the upper cladding layer (24) can be made of one of silicon dioxide and polymer with a lower refractive index. In this embodiment, silicon dioxide is selected as the upper and lower cladding layers, and its refractive index at a wavelength of 1550nm is 1.444. The modulator of the present invention adopts a three-dimensional integration method. The waveguide structure is divided into two layers. The lower optical waveguide core layer (25) can be made of materials such as silicon nitride, silicon, doped silicon dioxide, polymer with a higher refractive index. In this embodiment, silicon nitride material is used, and its refractive index at a wavelength of 1550nm is 1.933. The upper optical waveguide core layer (26) uses a ferroelectric material, which can be lead zirconate titanate, lanthanum-modified lead zirconate titanate, barium titanate, etc. In this embodiment, lead zirconate titanate (PZT) material is used, and its refractive index at a wavelength of 1550nm is 2.37. The metal electrode layer (27) can be made of one of aluminum, gold, silver, tungsten and titanium. In this embodiment, an aluminum electrode is used.

[0038] As attached Figure 3 The figure shows a schematic diagram of the structure of the 1×2 input Bessel-shaped multimode interference coupler used in the present invention, which is composed of a Bessel input straight waveguide (28), a Bessel-shaped multimode interference region (29), a first Bessel-shaped output wedge converter (30), a second Bessel-shaped output wedge converter (31), a first Bessel output straight waveguide (32), and a second Bessel output straight waveguide (33). The Bessel bending curves on the upper and lower sides of the Bessel-shaped multimode interference coupler are symmetrical about the central axis of the Bessel input straight waveguide (28); the Bessel bending curves on the upper and lower sides of the Bessel-shaped wedge converter are symmetrical about the central axis of the Bessel-shaped wedge converter; the Bessel-shaped multimode interference couplers on the left and right sides of the entire electro-optical modulator are of the same size and are symmetrical about the central axis of the device ( Figure 1 The Bessel-shaped multimode interference coupler has a smaller footprint and lower excess loss at a wide bandwidth than ordinary multimode interference couplers.

[0039] The thickness of the 1×2 input Bessel-shaped multimode interference coupler is 0.3 μm, the lengths of the Bessel input straight waveguide (28), the first Bessel output straight waveguide (32) and the second Bessel output straight waveguide (33) are equal to 1.6 μm, and the widths are equal to 0.9 μm; the length of the Bessel-shaped multimode interference region (29) is 49 μm, and the width gradually changes from 0.9 μm to 11 μm; the lengths of the first Bessel-shaped output wedge-shaped converter (30) and the second Bessel-shaped output wedge-shaped converter (31) are equal to 10.6 μm, and the width gradually changes from 4 μm to 0.9 μm, and the spacing between the central axes is 3.4 μm.

[0040] As attached Figure 4Figure 2 shows the transmission spectrum of the Bessel-type multimode interference coupler used in the present invention. The transmission loss is as low as 3.2dB under a light source with a wavelength of 1550nm, and the transmission loss of both channels is less than 3.3dB in the wavelength range of 1500nm to 1600nm.

[0041] As attached Figure 5 The figure shows the transmission light field of the Bessel-type multimode interference coupler used in the present invention. As can be seen from the figure, the transmission light field is symmetrical about the central axis, and the two output channels have uniform light splitting, which has a good transmission effect.

[0042] As attached Figure 6 The figure shows the transmission spectrum of the wedge-shaped waveguide used in the present invention. Under a light source with a wavelength of 1550nm, the transmission loss is as low as 0.0045dB, and in the wavelength range of 1500nm to 1600nm, the transmission loss of the coupling device is less than 0.014dB. The lengths of the first input lower layer wedge waveguide (5), the second input lower layer wedge waveguide (6), the first output upper layer wedge waveguide (14) and the second output upper layer wedge waveguide (15) are equal to 65.556 μm, and their widths gradually change from 0.9 μm to 0; the lengths of the first input upper layer wedge waveguide (7), the second input upper layer wedge waveguide (8), the first output lower layer wedge waveguide (16) and the second output lower layer wedge waveguide (17) are equal to 65.556 μm, and their widths gradually change from 0 to 0.9 μm; and the spacing between the upper and lower layers of the wedge waveguides, i.e., the thickness of the upper cladding layer (24) between the upper optical waveguide core layer and the lower optical waveguide core layer, is 0.2 μm.

[0043] As attached Figure 7 As shown in FIG, the transmission light field diagram of the wedge-shaped waveguide used in the present invention is shown. As can be seen from the figure, the light in the optical waveguide is gradually directionally coupled from the lower silicon nitride wedge-shaped coupling structure into the upper PZT wedge-shaped coupling structure and enters the modulation region.

[0044] As attached Figure 8 The figure shows the curve of the modulation voltage and light transmission loss of the modulator of the present invention over time. The wavelength of light is 1550nm and the electrode spacing is 5μm. The half-wave voltage V π is 3.58V, the modulation efficiency V π L = 1.79 V·cm, extinction ratio ER = 5.5 dB.

[0045] As attached Figure 9 As shown, the method for preparing the electro-optical modulator of the present invention is as follows:

[0046] First, a silicon nitride film is deposited on a silicon wafer with a 3μm-thick silicon dioxide layer and chemically mechanically polished (CMP) to a thickness of 300nm. Then, inductively coupled plasma etching (ICP) is used to produce the lower silicon nitride waveguide core structure. Next, a silicon dioxide film is deposited as an upper cladding layer, and the surface is CMPed to a thickness of 500nm. On this basis, a lead zirconate titanate (PZT) solution is spin-coated and annealed at 550°C using rapid thermal annealing (RTA) technology to form a PZT film. The surface is also CMPed to a thickness of 300nm. A mask is formed by photolithography, and ICP etching is performed to obtain the upper PZT waveguide core structure. Then, aluminum electrodes are prepared, and a silicon dioxide film is spin-coated as an upper cladding layer. The silicon dioxide is etched to expose the electrodes and form contact holes.

Claims

1. An electro-optical modulator heterogeneously integrated with silicon and ferroelectric materials, characterized by: From bottom to top, it is composed of a silicon-based substrate, a lower cladding layer, an optical waveguide core layer, and an upper cladding layer. The optical waveguide core layer adopts a three-dimensional integration method and is a two-layer structure of an upper optical waveguide core layer and a lower optical waveguide core layer. The upper optical waveguide core layer and the lower optical waveguide core layer are both coated in the upper cladding layer, and the upper optical waveguide core layer and the lower optical waveguide core layer are separated by the upper cladding layer. The optical waveguide core layer is an MZI type structure, which is composed of an input straight waveguide (1) located in the lower optical waveguide core layer, a 1×2 input Bessel-shaped multimode interference coupler (2), a first input S-bend waveguide (3), a second input S-bend waveguide (4), a first input lower layer wedge waveguide (5), a second input lower layer wedge waveguide (6), a first output lower layer wedge waveguide (16), a second output lower layer wedge waveguide (17), a first output S-bend waveguide (18), a second output S-bend waveguide (19), a 2×1 output Bessel-shaped multimode interference coupler (20), an output straight waveguide (21), and a first input upper layer wedge waveguide located in the upper optical waveguide core layer. The invention relates to an optical waveguide comprising a first modulation straight waveguide (9), a second modulation straight waveguide (10), a first output upper wedge-shaped waveguide (14), and a second output upper wedge-shaped waveguide (15); the input straight waveguide (1) and the output straight waveguide (21) are located on the same straight line, and the upper optical waveguide core layer and the lower optical waveguide core layer are symmetrical structures with respect to the input straight waveguide (1) and the output straight waveguide (21); in the lower optical waveguide core layer, the input straight waveguide (1) is connected to the input end of the input 1×2 Bessel-shaped multimode interference coupler (2), and the output ends of the first input S-bend waveguide (3) and the second input S-bend waveguide (4) are connected. The input ends are respectively connected to the two output ends of the 1×2 input Bessel-shaped multimode interference coupler (2); the output end of the first input S-bend waveguide (3) is connected to the first input lower layer wedge-shaped waveguide (5); the output end of the second input S-bend waveguide (4) is connected to the second input lower layer wedge-shaped waveguide (6); the first output lower layer wedge-shaped waveguide (16) is connected to the input end of the first output S-bend waveguide (18); the second output lower layer wedge-shaped waveguide (17) is connected to the input end of the second output S-bend waveguide (19); the output ends of the first output S-bend waveguide (18) and the second output S-bend waveguide (19) are respectively connected to the 2×1 output Bessel-shaped multimode interference coupler (2); The two input ends of the coupler (20) and the output end of the 2×1 output Bessel-shaped multimode interference coupler (20) are connected to the output straight waveguide (21); in the upper optical waveguide core layer, the first modulation straight waveguide (9) and the second modulation straight waveguide (10) are arranged in parallel as modulation arms, the first input upper layer wedge-shaped waveguide (7) is connected to the input end of the first modulation straight waveguide (9), and the output end of the first modulation straight waveguide (9) is connected to the first output upper layer wedge-shaped waveguide (14); the second input upper layer wedge-shaped waveguide (8) is connected to the input end of the second modulation straight waveguide (10), and the output end of the second modulation straight waveguide (10) is connected to the second output upper layer wedge-shaped waveguide (15);All wedge-shaped waveguides have the same size, and the first input lower layer wedge-shaped waveguide (5), the second input lower layer wedge-shaped waveguide (6), the first output lower layer wedge-shaped waveguide (16), and the second output lower layer wedge-shaped waveguide (17) in the lower optical waveguide core layer respectively form upper and lower parallel interlayer coupling structures with the first input upper layer wedge-shaped waveguide (7), the second input upper layer wedge-shaped waveguide (8), the first output upper layer wedge-shaped waveguide (14), and the second output upper layer wedge-shaped waveguide (15) in the upper waveguide core layer; In the upper optical waveguide core layer, a first grounding metal electrode (11), a signal metal electrode (13), and a second grounding metal electrode (12) are respectively provided on the outside of the first modulation straight waveguide (9), between the first modulation straight waveguide (9) and the second modulation straight waveguide (10), and on the outside of the second modulation straight waveguide (10). The lower optical waveguide core layer (25) is one of silicon nitride or silicon, and the upper optical waveguide core layer (26) is one of lead zirconate titanate, lanthanum-modified lead zirconate titanate, or barium titanate.

2. The electro-optical modulator heterogeneously integrated with silicon and ferroelectric materials according to claim 1, characterized in that: The silicon-based substrate (22) is silicon; the lower cladding layer (23) and the upper cladding layer (24) are silicon dioxide, and in the same device, the lower cladding layer (23) and the upper cladding layer (24) are made of the same material; and the metal electrode is one of aluminum, gold, silver, tungsten or titanium.

3. The electro-optical modulator heterogeneously integrated with silicon and ferroelectric materials according to claim 1, characterized in that: The 1×2 input Bessel-shaped multimode interference coupler (2) is composed of a Bessel-shaped input straight waveguide (28) as an input end, a Bessel-shaped multimode interference region (29), a first Bessel-shaped output wedge-shaped converter (30) and a second Bessel-shaped output wedge-shaped converter (31) as output ends, a first Bessel-shaped output straight waveguide (32) and a second Bessel-shaped output straight waveguide (33); the Bessel-shaped input straight waveguide (28) is connected to the input straight waveguide (1); the first Bessel-shaped output wedge-shaped converter (30), the first Bessel-shaped output straight waveguide (32) and the first input S-bend waveguide (3) are connected in sequence; the second Bessel-shaped output wedge-shaped converter (31), the second Bessel-shaped output straight waveguide (33) and the second The input S-bend waveguides (4) are connected in sequence; the 1×2 input Bessel-shaped multimode interference coupler (2) is a symmetrical structure about the central axis of the Bessel-shaped input straight waveguide (28); the Bessel-shaped bending curves on both sides of the Bessel-shaped multimode interference region (29) are symmetrical about the central axis of the Bessel-shaped input straight waveguide (28); the Bessel-shaped bending curves of the first Bessel-shaped output wedge converter (30) and the second Bessel-shaped output wedge converter (31) are symmetrical about the central axis of the first Bessel-shaped output wedge converter (30) and the second Bessel-shaped output wedge converter (31); and the 2×1 output Bessel-shaped multimode interference coupler (20) and the 1×2 input Bessel-shaped multimode interference coupler (2) are symmetrical structures.

4. The electro-optical modulator heterogeneously integrated with silicon and ferroelectric materials according to claim 3, characterized in that: The lengths of the Bessel input straight waveguide (28), the first Bessel output straight waveguide (32) and the second Bessel output straight waveguide (33) are equal to 1.6 μm, and the widths are equal to 0.9 μm; the length of the Bessel-shaped multimode interference region (29) is 49 μm, and the width gradually changes from 0.9 μm to 11 μm; the lengths of the first Bessel-shaped output wedge-shaped converter (30) and the second Bessel-shaped output wedge-shaped converter (31) are equal to 10.6 μm, and the width gradually changes from 4 μm to 0.9 μm, and the spacing between the central axes is 3.4 μm.

5. The electro-optical modulator heterogeneously integrated with silicon and ferroelectric materials according to any one of claims 1 to 4, characterized in that: The thickness of the upper optical waveguide core layer and the lower optical waveguide core layer are equal to 0.3 μm, the thickness of the upper cladding layer (24) between the upper optical waveguide core layer and the lower optical waveguide core layer is 0.2 μm, the width of the input straight waveguide (1), the first input S-bend waveguide (3), the second input S-bend waveguide (4), the first output S-bend waveguide (18), the second output S-bend waveguide (19), the output straight waveguide (21), the first modulation straight waveguide (9), and the second modulation straight waveguide (10) are equal to 0.9 μm; the first The lengths of the input lower layer wedge-shaped waveguide (5), the second input lower layer wedge-shaped waveguide (6), the first output upper layer wedge-shaped waveguide (14) and the second output upper layer wedge-shaped waveguide (15) are all equal to 65.556 μm, and their widths gradually change from 0.9 μm to 0 μm; the lengths of the first input upper layer wedge-shaped waveguide (7), the second input upper layer wedge-shaped waveguide (8), the first output lower layer wedge-shaped waveguide (16) and the second output lower layer wedge-shaped waveguide (17) are all equal to 65.556 μm, and their widths gradually change from 0 to 0.9 μm.

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