Polymer silicon nitride heterogeneous integrated M-Z optical waveguide acousto-optic switch

Abstract

The invention provides a polymer silicon nitride heterogeneous integrated M-Z optical waveguide acousto-optic switch, and the switch comprises a substrate chip which comprises an inorganic substrate layer, an inorganic waveguide lower cladding layer, and a waveguide core layer; an M-Z optical waveguide structure layer is formed on the waveguide core layer; a polymer cladding is arranged on the M-Z optical waveguide structure layer, the polymer cladding is of a dome structure, and a driving layer is arranged on the polymer cladding; wherein the waveguide core layer is a silicon nitride waveguide core layer with an M-Z structure, and is obtained by etching a silicon nitride layer in the substrate chip. According to the M-Z optical waveguide acousto-optic switch, heterogeneous integration is carried out by taking silicon nitride as an optical waveguide core layer and taking a polymer material as an optical waveguide cladding layer, so that multiple optimization in the aspects of stress utilization rate, stress conversion efficiency, device preparation cost, anti-crosstalk structure compatibility and the like is realized, and the effects of performance improvement and low power consumption of the M-Z optical waveguide acousto-optic switch are further achieved.

Description

Technical Field

[0001] This invention relates to the field of hybrid integrated photonic chip technology of polymer optical waveguides and silicon nitride waveguides, and specifically to an MZ optical waveguide acousto-optic switch of polymer silicon nitride heterogeneous integration. Background Technology

[0002] Optical switch chips are core components of optical communication and optical networks, used to realize optical signal conversion, splitting, attenuation, multiplexing, and wavelength division multiplexing functions. Currently, they can be categorized into electro-optic, thermo-optic, all-optic, and acousto-optic switches. Silicon-based electro-optic switches offer a significant advantage in switching speed, ranging from picoseconds (ps) to nanoseconds (ns), but limitations such as carrier absorption loss result in relatively high loss characteristics. Thermo-optic switches possess mature modulation techniques, but their millisecond (ms) switching speeds cannot meet the demands of scenarios requiring rapid switching. All-optic switches offer driving methods suitable for all-optical networks, but their light control power consumption and losses are relatively high. Acousto-optic switches employ acousto-optic modulation technology, which boasts broad compatibility, is applicable to commercially available chip materials like silicon nitride that lack tuning properties, and allows piezoelectric films to be mounted on the surface of photonic chips without introducing additional device losses. Furthermore, they offer high speed and low power consumption. Therefore, in large-scale switch array applications, acousto-optic switches are the preferred solution due to their low loss, high compatibility, low power consumption, and high modulation speed.

[0003] In terms of device structure, existing technologies employ microring resonators or optical Mach-Zehnder interferometers (MZIs). While integrating microring resonators yields a compact microring structure, it suffers from significant process tolerances and bending losses. Large-scale switch array applications must balance the process tolerances and integration requirements of optical chips. Compared to microring resonators, MZIs can operate over a wider optical bandwidth, particularly in optical modulators, where this characteristic provides higher modulation bandwidth and facilitates wavelength division multiplexing (WDM) in optical communications. Furthermore, MZIs can serve as on-chip beam splitters, fundamental for building optical neural networks and optical quantum computing. Especially for programmable photonic chips, the high tunability of MZIs enables the reconfiguration of complex computational tasks, such as unitary transformations. Therefore, MZIs are the preferred solution for large-scale switch array applications.

[0004] Most existing MZI devices rely on thermo-optical tuning, but due to limitations in size, power consumption, and crosstalk in practical applications, piezoelectric tuning has become the preferred solution. In the piezoelectric tuning scheme, the MZI acousto-optic switch is implemented by combining a photonic chip and a piezoelectric actuator. The phase shift of the MZI can be enhanced by optimizing the design of the piezoelectric actuator.

[0005] In existing optimization schemes, a dome-shaped actuator is introduced that effectively concentrates stress on the waveguide. This involves forming a 1-micron-high surface protrusion structure after silicon nitride etching, with the dome formed by uniformly depositing a silicon dioxide top cladding layer on the waveguide. Furthermore, the waveguide structure is optimized by designing an asymmetric dual-band waveguide to tightly confine the optical modes. This reduces the thickness of the top cladding layer from 8 microns to 3 microns, thereby improving device performance. These designs significantly increase the overlap between the optical modes and stress distribution, resulting in device performance that is up to twice that of conventional planar PZT actuators.

[0006] In summary, the dome and waveguide structures effectively improve the utilization efficiency of the stress field, enabling low power consumption when applied to piezoelectric acousto-optic switches. However, from a materials perspective, the use of silicon nitride core and silicon dioxide cladding as the fixing materials limits the potential for further material-based performance enhancements. Therefore, a polymer-silicon nitride heterogeneous integration solution is urgently needed to improve the performance of MZ optical waveguide acousto-optic switches. Summary of the Invention

[0007] This invention provides a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch, which is mainly used to solve the optimization problem of existing optical switches in large-scale switch array applications. By heterogeneously integrating silicon nitride as the optical waveguide core layer and polymer material as the optical waveguide cladding, multiple optimizations are achieved in terms of stress utilization, stress conversion efficiency, device fabrication cost, and anti-crosstalk structural compatibility, thereby achieving performance improvement and low power consumption of the MZ optical waveguide acousto-optic switch.

[0008] The present invention achieves the above objectives through the following technical solutions: A polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch includes: The substrate chip includes an inorganic substrate layer, an inorganic waveguide cladding layer, and a waveguide core layer, wherein an MZ optical waveguide structure layer is formed on the waveguide core layer.

[0009] The MZ optical waveguide structure layer is provided with a polymer cladding, which is a dome structure, and a driving layer is provided on it.

[0010] The waveguide core layer is a silicon nitride waveguide core layer with an MZ structure, which is obtained by etching a silicon nitride layer in the substrate chip.

[0011] According to the present invention, a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch is provided, wherein the substrate chip is provided with the waveguide core layer, the inorganic waveguide lower cladding layer and the inorganic substrate layer in sequence from top to bottom, thereby forming a silicon nitride waveguide chip.

[0012] The waveguide core layer is a high-refractive-index silicon nitride layer with a refractive index of 1.9 to 2.5.

[0013] The inorganic waveguide cladding is a low-refractive-index silicon dioxide layer with a refractive index of 1.44 to 1.45.

[0014] The substrate layer is made of silicon, glass, or silicon dioxide.

[0015] According to the present invention, a polymer silicon nitride hetero-integrated MZ optical waveguide acousto-optic switch is provided, wherein the fabrication steps of the silicon nitride waveguide core layer having an MZ structure include: A substrate chip is selected, which is rectangular when projected in the vertical direction.

[0016] To obtain the silicon nitride layer with a high refractive index.

[0017] A silicon nitride waveguide mask layer is fabricated on the substrate chip to form the silicon nitride waveguide core layer.

[0018] Photoresist is spin-coated onto the silicon nitride waveguide mask layer to form a photoresist thin film layer.

[0019] An MZ pattern is introduced onto the photoresist thin film layer, and then photolithography and development are performed using an MZ photomask to obtain a photoresist mask layer.

[0020] The MZ pattern is a branched, parallel, and coupled structure based on silicon nitride waveguides.

[0021] According to the present invention, a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch is provided, wherein the MZ photolithography plate includes an input / output region, a Y-branch region and a straight waveguide pattern, wherein the input / output region is a strip-shaped straight waveguide and the length of the strip-shaped straight waveguide in the z-direction is greater than the long side of the substrate chip.

[0022] The waveguide width of the Y-branch region is the same as that of the strip waveguide, the length of the Y-branch region is its length along the propagation direction of the input / output region, and its width is the distance between the two strip waveguides.

[0023] The long side of the straight waveguide pattern is arranged parallel to the long side of the substrate chip.

[0024] According to the present invention, a polymer silicon nitride hetero-integrated MZ optical waveguide acousto-optic switch is provided, wherein the fabrication steps of the silicon nitride waveguide core layer having the MZ structure further include: The photoresist mask layer is used for masking.

[0025] The silicon nitride waveguide mask layer is etched with a corresponding mask etching reagent to obtain a waveguide mask pattern, which is the same as the pattern of the photoresist mask layer.

[0026] The silicon nitride layer is obtained by plasma etching or ICP etching, and the etching depth is equal to the thickness of the silicon nitride layer.

[0027] The waveguide mask pattern and the photoresist mask layer are removed to obtain the silicon nitride waveguide core layer with an MZ structure.

[0028] According to the present invention, a polymer silicon nitride hetero-integrated MZ optical waveguide acousto-optic switch is provided, wherein the preparation steps of the polymer cladding include: Polymer cladding material is spin-coated or imprinted onto the silicon nitride waveguide chip.

[0029] The appropriate curing method is selected based on the material properties of the polymer coating material to prepare the polymer coating film.

[0030] The polymer-clad film forms a dome structure on the top layer.

[0031] The polymer cladding film is photolithographically etched and then developed to form a polymer cladding covering the silicon nitride waveguide core MZ structure.

[0032] According to the present invention, a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch is provided, wherein the driving layer includes an electrode layer, the electrode layer being formed with an electrode pattern layer, the steps of which include: A photoresist layer is spin-coated onto the electrode layer to obtain an electrode material mask layer.

[0033] An electrode pattern mask with electrode patterns is placed on the electrode material mask layer, and photolithography is performed.

[0034] Remove the electrode pattern mask, and use a corresponding photoresist developer to remove the photoresist layer and a corresponding electrode etchant to etch the electrode material mask layer, thereby obtaining the electrode pattern layer.

[0035] According to the present invention, a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch is provided, wherein the electrode pattern mask has a strip structure in the middle, which is used to make the straight electrodes of the electrode layer parallel and cover the silicon nitride modulation arm in the MZ optical waveguide structure layer.

[0036] The electrode pins of the straight electrode adopt a same-side lead-out structure, with both ends extending outward along the extension direction perpendicular to the straight electrode.

[0037] According to the present invention, a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch is provided, wherein the driving layer further includes an adhesive layer and a piezoelectric layer, which are integrated by process A or process B.

[0038] The piezoelectric layer is a piezoelectric film, which includes an adhesive surface for contacting the adhesive layer and an exposed surface.

[0039] If process A is used, the lower electrode layer, the adhesive layer, the piezoelectric layer and the upper plate electrode layer are sequentially integrated above the driving layer; if process B is used, the adhesive layer, the lower plate electrode layer, the piezoelectric layer and the upper electrode layer are sequentially integrated above the driving layer.

[0040] Wherein, the lower electrode layer or the upper electrode layer is the electrode layer on which the electrode pattern layer is formed.

[0041] According to the present invention, a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch is provided, wherein the step of process A includes: The lower electrode layer, with a single-surface structure, is formed on the polymer coating.

[0042] The lower electrode layer obtains the lower electrode pattern according to the formation steps of the electrode pattern layer.

[0043] A single-surface structure upper plate electrode layer is prepared on the exposed surface of the piezoelectric film.

[0044] The adhesive surface of the piezoelectric film is adhered to the surface of the polymer coating through the adhesive layer and then cured at low temperature.

[0045] The steps of process B include: Electrodes are pre-formed on both sides of the piezoelectric film.

[0046] Using one side of the piezoelectric film as the adhesive surface, it is adhered to the surface of the polymer coating through the adhesive layer and then cured at low temperature.

[0047] Using the other side of the piezoelectric film as the upper electrode layer, the upper electrode pattern is obtained according to the steps of forming the electrode pattern layer.

[0048] Therefore, the present invention has the following beneficial effects: 1. This invention introduces a polymer layer into the heterogeneously integrated MZ optical waveguide acousto-optic switch. Compared to the silicon dioxide layer used in traditional solutions, the elastic-optical effect of the polymer cladding is several times to two orders of magnitude greater than that of silicon dioxide. By enhancing the elastic-optical effect, the conversion efficiency from stress to refractive index is improved, thereby increasing the conversion efficiency between the stress field and the optical field. Secondly, since the polymer naturally forms a dome structure during spin-coating to prepare the cladding, the stress distribution of the device is mainly concentrated in the waveguide core layer, which further enhances the overlap between the optical field and the stress field, improving the coupling efficiency between the stress field and the optical field. Finally, since the refractive index of the polymer is adjustable, more light can be concentrated in the polymer material with a high elastic-optical coefficient, further improving the stress conversion efficiency. Therefore, compared to traditional acousto-optic modulation technology, this invention is more conducive to achieving low-power design of the acousto-optic switch in terms of both the coupling efficiency between the stress field and the optical field and the conversion efficiency from the stress field to the optical field.

[0049] 2. The polymer and silicon nitride materials used in this invention have advantages in terms of cost and manufacturing process. Polymer materials are generally low in cost and simple to manufacture, making them suitable for large-scale production. Silicon nitride materials have the characteristics of low transmission loss and low coupling loss, which is conducive to realizing the low-cost and high-performance design of acousto-optic switches.

[0050] 3. The dome microstructure of the polymer in this invention is compatible with the cladding air groove structure and can be fabricated simultaneously, thereby reducing the manufacturing cost of the switch chip and reducing the crosstalk effect of large-scale switch array applications.

[0051] 4. This invention, through the submicron-sized design of silicon nitride waveguides, can shorten the propagation path of sound waves, enabling the response speed of the acousto-optic switch to reach the microsecond level.

[0052] 5. The silicon nitride of this invention is compatible with polymer processes and is suitable for CMOS production lines. Therefore, it can be manufactured directly through existing semiconductor production lines without additional equipment or steps, which significantly reduces manufacturing costs and enhances device reliability.

[0053] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of the first structure of the substrate chip in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0055] Figure 2 This is a schematic diagram of the second structure of the substrate chip in an embodiment of a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch of the present invention.

[0056] Figure 3This is a schematic diagram of the structure of the MZ photolithography plate in an embodiment of the polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0057] Figure 4 This is a schematic diagram of the principle of the MZ patterned photomask in an embodiment of a polymer silicon nitride hetero-integrated MZ optical waveguide acousto-optic switch of the present invention. Figure 5 This is a schematic diagram of the first structure of the MZ optical waveguide structure layer in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0058] Figure 6 This is a schematic diagram of the first structure after polymer cladding is applied in an embodiment of the polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0059] Figure 7 This is a schematic diagram of the electrode layer coverage in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0060] Figure 8 This is a schematic diagram of the photoresist patterning (including electrodes) structure in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0061] Figure 9 This is a schematic diagram of the structure of the strip electrode pattern mask in an embodiment of the polymer silicon nitride heterogeneous integrated MZ optical waveguide acousto-optic switch of the present invention.

[0062] Figure 10 This is a planar schematic diagram of a mask plate with electrode patterns in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0063] Figure 11 This is a schematic diagram of the etching and photoresist residue cleaning (including electrodes) in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0064] Figure 12 This is a schematic diagram of the first structure of the polymer cladding package (including electrodes) in an embodiment of the polymer silicon nitride heterogeneous integrated MZ optical waveguide acousto-optic switch of the present invention.

[0065] Figure 13 This is a schematic diagram of the electrode base structure in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0066] Figure 14 This is a schematic diagram of the electrode-piezoelectric layer composite structure in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0067] Figure 15 This is a schematic diagram of the multilayer stacked structure (including electrodes and piezoelectric layers) in an embodiment of a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch of the present invention.

[0068] Figure 16 This is a schematic diagram of the structure of the piezoelectric layer covering electrode in an embodiment of the polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0069] Figure 17 This is a schematic diagram of the structure after electrode-piezoelectric layer encapsulation in an embodiment of the polymer silicon nitride heterogeneous integrated MZ optical waveguide acousto-optic switch of the present invention.

[0070] Figure 18 This is a schematic diagram of the photoresist patterning (including electrodes and piezoelectric layer) structure in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0071] Figure 19 This is a schematic diagram of the structure of the strip electrode and the matching pattern mask in an embodiment of the polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0072] Figure 20 This is a schematic diagram of the etched structure (including electrodes, a backing plate, and a piezoelectric layer) of an MZ optical waveguide acousto-optic switch with polymer silicon nitride heterostructure integration according to the present invention.

[0073] Figure 21 This is a schematic diagram of the multilayer structure (including electrodes, a mating plate, and a piezoelectric layer) in an embodiment of a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch of the present invention.

[0074] Figure 22 This is a schematic diagram of the structure of the multilayer structure (including electrodes, a mounting plate, and a piezoelectric layer) covering the electrode in an embodiment of the polymer silicon nitride heterogeneous integrated MZ optical waveguide acousto-optic switch of the present invention.

[0075] Figure 23 This is a schematic diagram of the second structure of the MZ optical waveguide structure layer in an embodiment of a polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0076] Figure 24 This is a schematic diagram of the second structure after polymer cladding in an embodiment of the polymer silicon nitride heterointegrated MZ optical waveguide acousto-optic switch of the present invention.

[0077] Figure 25 This is a schematic diagram of the second structure of the polymer cladding package (including electrodes) in an embodiment of the polymer silicon nitride heterogeneous integrated MZ optical waveguide acousto-optic switch of the present invention. Detailed Implementation

[0078] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0079] Example 1 of a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch See Figure 1 The present invention relates to a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch, comprising: The substrate chip includes an inorganic substrate layer, an inorganic waveguide cladding layer, and a waveguide core layer, wherein an MZ optical waveguide structure layer is formed on the waveguide core layer.

[0080] The MZ optical waveguide structure layer is provided with a polymer cladding, which is a dome structure, and a driving layer is provided on it.

[0081] The waveguide core layer is a silicon nitride waveguide core layer with an MZ structure, which is obtained by etching a silicon nitride layer in the substrate chip.

[0082] In this embodiment, the substrate chip is formed by sequentially comprising the waveguide core layer, the inorganic waveguide cladding layer, and the inorganic substrate layer from top to bottom, thereby forming a silicon nitride waveguide chip.

[0083] The waveguide core layer is a high-refractive-index silicon nitride layer with a refractive index of 1.9 to 2.5 and a thickness of 0.1 to 2 micrometers.

[0084] The inorganic waveguide cladding is a low-refractive-index silicon dioxide layer with a refractive index of 1.44~1.45 and a thickness of 3~15µm.

[0085] The substrate layer is a silicon-based silicon dioxide layer with a thickness greater than 3µm, a refractive index of 1.44~1.45, and a total thickness of 100~1000µm.

[0086] In this embodiment, the fabrication steps of the silicon nitride waveguide core layer with the MZ structure include: selecting a substrate chip, wherein the substrate chip is projected as a rectangle in the vertical direction; obtaining the silicon nitride layer with a high refractive index; fabricating a silicon nitride waveguide mask layer of the silicon nitride waveguide core layer on the substrate chip; spin-coating photoresist on the silicon nitride waveguide mask layer to form a photoresist thin film layer; importing an MZ pattern onto the photoresist thin film layer, and performing photolithography and development using an MZ photomask to obtain the photoresist mask layer.

[0087] The MZ pattern is a branched, parallel, and coupled structure based on silicon nitride waveguides.

[0088] Specifically, in this embodiment, a chromium (Cr) film with a thickness of 10-200 nm is deposited on the substrate chip using electron beam evaporation as a mask layer for subsequent silicon nitride waveguide etching. A photoresist film layer is then formed by spin-coating with parameters of 1000-10000 rpm for 30-90 s, resulting in a thickness of 0.1-5 µm. Pre-baking is performed at 60-90°C for 1-30 min. A pattern is then applied to the photoresist film layer using a photomask or a maskless lithography machine for photolithography. After development, a photoresist mask layer is obtained, and the integrity of the mask pattern is observed.

[0089] In this embodiment, the MZ photomask includes an input / output region, a Y-branch region, and a straight waveguide pattern. The input / output region is a strip-shaped straight waveguide, and the length of the strip-shaped straight waveguide in the z-direction is greater than the long side of the substrate chip.

[0090] Specifically, in this embodiment, the length of the strip-shaped straight waveguide is 0.02~10mm and the width is 0.5μm~8μm.

[0091] The waveguide width of the Y-branch region is the same as that of the strip waveguide, the length of the Y-branch region is its length along the propagation direction of the input / output region, and its width is the distance between the two strip waveguides.

[0092] Specifically, in this embodiment, the length of the Y-branch region is 500μm-20000μm and the width is 10-100μm. The ratio of half of its width to its length must be less than arctan(0.5°). The corresponding Y-branch curve shape is arcsine and arccosine. Once its length and width are fixed, the curve structure is fixed.

[0093] The long side of the straight waveguide pattern is arranged parallel to the long side of the substrate chip.

[0094] Specifically, in this embodiment, the straight waveguide pattern is a rectangle with a length of 50μm to 20000μm and a width of 0.5μm to 8μm. The long side of the rectangular waveguide is parallel to the long side of the substrate chip, and the distance between its long side and the long side of the substrate chip in the x-direction is 50μm to 200μm, while its length in the z-direction is greater than the length of the long side of the substrate chip.

[0095] Specifically, the structure of the MZ photomask in this embodiment also includes alignment marks located at the four corners of the photomask, 150μm from the long edge of the substrate and 150μm from the short edge; the structure is cross-shaped, with an outer frame size of 40μm×40μm and a line width of 4μm.

[0096] In this embodiment, the fabrication steps of the silicon nitride waveguide core layer with the MZ structure further include: The photoresist mask layer is used for masking.

[0097] The silicon nitride waveguide mask layer is etched with a corresponding mask etching reagent to obtain a waveguide mask pattern, which is the same as the pattern of the photoresist mask layer.

[0098] The silicon nitride layer is obtained by plasma etching or ICP etching, and the etching depth is equal to the thickness of the silicon nitride layer, ranging from 0.1 to 2 micrometers.

[0099] Remove the waveguide mask pattern and the photoresist mask layer to obtain the silicon nitride waveguide core layer with the MZ structure.

[0100] Specifically, in this embodiment, the photoresist mask layer is removed using a corresponding photoresist developer, the waveguide mask pattern is removed using a corresponding solution such as a chromium etching solution for chromium or a phosphoric acid mixture for aluminum, the chip is rinsed three times with deionized water, and dried with nitrogen gas to obtain a silicon nitride waveguide chip.

[0101] In this embodiment, the preparation steps of the polymer coating include: Polymer cladding material is spin-coated or imprinted onto the silicon nitride waveguide chip, and a polymer cladding film is prepared by selecting a thermosetting or photocuring method according to the material properties.

[0102] The polymer cladding film is photolithographically etched and then developed to form a polymer cladding covering the silicon nitride waveguide core MZ structure.

[0103] Specifically, the polymer coating film described in this embodiment has a thickness of 1~10µm and forms a dome structure on the top layer.

[0104] In this embodiment, the spin-coated polymer coating material is cured to obtain the polymer coating film.

[0105] Specifically, in this embodiment, the spin coating speed of the polymer coating material is 2500~10000 rpm, and the spin coating time is 30~300s. For thermosetting materials, the initial baking temperature is 50-80℃ for 1-20 minutes, followed by a post-baking temperature of 80-120℃ for 1-20 minutes; for photocurable materials, the exposure intensity is 10-100mW / cm². 2 Expose for 10-600 seconds. If using anaerobic adhesive, nitrogen gas can be introduced for protection according to the adhesive requirements. The cladding thickness formed in the flat plate area is 0.4-10µm, which is 1-10µm greater than the height of the silicon nitride waveguide layer, so that the cladding forms a dome-shaped protrusion structure directly above the waveguide. The thickness of the cladding is verified by step tester in the flat plate area.

[0106] Specifically, the thickness of the polymer cladding in this embodiment is 1.5~12µm thicker than that of the silicon nitride waveguide.

[0107] In this embodiment, the driving layer includes an electrode layer, and the electrode layer is formed with an electrode pattern layer. The steps include: A photoresist layer is spin-coated onto the electrode layer to obtain an electrode material mask layer.

[0108] An electrode pattern mask with electrode patterns is placed on the electrode material mask layer, and photolithography is performed.

[0109] Remove the electrode pattern mask, and use a corresponding photoresist developer to remove the photoresist layer and a corresponding electrode etchant to etch the electrode material mask layer, thereby obtaining the electrode pattern layer.

[0110] Specifically, in this embodiment, the thickness of the electrode layer is 20~500nm. After obtaining the polymer coating, an integration process between the electrode layer and the piezoelectric thin film is required.

[0111] In this embodiment, the electrode pattern mask has a strip structure in the middle, the width and length of the strip structure are 0.5~50μm and 50μm~20000μm respectively, which is used to make the straight electrodes of the electrode layer parallel and cover the silicon nitride modulation arm in the MZ optical waveguide structure layer.

[0112] The straight electrode has two pins on the same side to form a strip electrode. The pin structure is a rectangle with a length and width of 8~200μm and 8~200μm respectively in the z direction. Its two ends extend outward along the extension direction perpendicular to the straight electrode, which is the x direction. The distance between the inner edge of the electrode pin and the outer edge of the straight electrode is 1~500μm.

[0113] In this embodiment, the driving layer further includes an adhesive layer and a piezoelectric layer, which are integrated through process A or process B.

[0114] The piezoelectric layer is a piezoelectric film, which includes an adhesive surface for contacting the adhesive layer and an exposed surface.

[0115] If process A is used, the lower electrode layer, the adhesive layer, the piezoelectric layer and the upper plate electrode layer are sequentially integrated above the driving layer; if process B is used, the adhesive layer, the lower plate electrode layer, the piezoelectric layer and the upper electrode layer are sequentially integrated above the driving layer.

[0116] Wherein, the lower electrode layer or the upper electrode layer is the electrode layer on which the electrode pattern layer is formed.

[0117] In this embodiment, the steps of process A include: The lower electrode layer, with a single-surface structure, is formed on the polymer coating.

[0118] The lower electrode layer obtains the lower electrode pattern according to the formation steps of the electrode pattern layer.

[0119] A single-surface structure upper plate electrode layer is prepared on the exposed surface of the piezoelectric film.

[0120] The adhesive surface of the piezoelectric film is adhered to the surface of the polymer coating through the adhesive layer and then cured at low temperature.

[0121] Specifically, in process A of this embodiment, the thickness of the piezoelectric film is 0.5-100 micrometers, and its vertical projection is a rectangle. The length and width of the rectangle are both smaller than the substrate chip, and its length is greater than the length of the silicon nitride modulation arm to cover it. Its width covers the straight electrode and satisfies the requirement that the pins of the straight electrode are exposed during alignment.

[0122] Specifically, in this embodiment, an aluminum layer is deposited in the preset electrode area of ​​the device as the lower electrode layer material using a vacuum evaporation process. The thickness of the aluminum layer is set according to the conductivity requirements, typically 50-500nm. The lower electrode layer is formed only on the upper surface of the chip, i.e., on the cladding surface. It is a single-surface electrode with an electrode on only one surface, and no electrodes on other surfaces.

[0123] Specifically, in this embodiment, a photoresist layer is spin-coated onto a thin layer of the lower electrode layer to obtain an electrode material mask layer with a thickness of 0.2~2µm. Subsequently, an electrode pattern mask with electrode patterns is overlaid on the photoresist layer for alignment photolithography. The middle strip structure of the electrode pattern mask has a width x7 of 0.5~50µm and a length L6 of 50µm~20000µm, ensuring that the straight electrode portion is completely parallel and covers one arm of the MZ waveguide structure.

[0124] Specifically, in this embodiment, the electrode pins adopt a same-side structure, which is a rectangular structure with a length of 8~200μm and a width of 8~200μm in the z-direction. The alignment marks are located at the four corners of the photomask, 150μm from the long edge and 150μm from the short edge of the substrate; the marks are cross-shaped, with an outer frame size of 40μm×40μm and a line width of 4μm.

[0125] Specifically, in this embodiment, after photolithography, the electrode pattern mask is removed. The photoresist layer and the lower electrode layer material are etched using a sodium hydroxide aqueous solution with a mass concentration of 4-6‰ at 25°C for 30 seconds. This etching time needs to be adjusted according to the electrode thickness. Immediately after etching, the material is rinsed five times with deionized water, then neutralized with 0.1% dilute hydrochloric acid for 10 seconds, rinsed again with deionized water, and dried with nitrogen. The photoresist layer on the lower electrode layer is removed by soaking in acetone for 10 minutes or by using a special photoresist remover that does not react with the upper cladding material, thus obtaining the lower electrode layer pattern.

[0126] Specifically, in this embodiment, the piezoelectric film is a functional material such as lithium niobate or PZT, with a thickness of 500 nm to 50 μm. An upper electrode, made of aluminum and with a thickness of 50-500 nm, is deposited on its upper surface via vapor deposition to form a single-surface electrode structure, meaning the electrode is only present on the non-adhesive side. During adhesion, the electrode-free side of the piezoelectric film is adhered to the upper surface of the chip using a 0.1-1 μm thick low-temperature curing adhesive. Precise alignment with the lower electrode layer is not required, but it must be ensured that the upper electrode is completely within the film's area. Low-temperature curing is then performed. It is important to note that double-sided electrode piezoelectric films are prohibited to avoid short circuits or signal interference.

[0127] The steps of process B include: Electrodes are prefabricated on both sides of the piezoelectric film, and metal leads are bonded to the edge of one side.

[0128] The side of the piezoelectric film bonded with metal leads is used as the adhesive surface, and the film is adhered to the surface of the polymer coating through the adhesive layer and then cured at low temperature.

[0129] Using the other side of the piezoelectric film as the upper electrode layer, the upper electrode pattern is obtained according to the steps of forming the electrode pattern layer.

[0130] Specifically, in process B of this embodiment, the thickness of the piezoelectric film is 0.5-100 micrometers, and its vertical projection is a rectangle. The length and width of the rectangle are both smaller than the substrate chip, and its length is greater than the length of the silicon nitride modulation arm to cover it. Its width is large enough to meet the size requirements of the electrode pattern mask, so that during the alignment process, the straight electrode and its pins can be completely photolithographically etched onto the upper electrode layer.

[0131] Specifically, in this embodiment, the pre-fabricated electrode materials on both sides of the piezoelectric film can be aluminum or silver, with a thickness of 50nm~500nm. The piezoelectric film, made of materials such as lithium niobate or PZT, possesses piezoelectric properties and has a thickness of 500nm~50μm. One surface of the piezoelectric film is used as the bonding surface, and it is bonded to the chip surface using a low-temperature curing adhesive with a thickness of 0.1~1μm. Precise alignment is not required, ensuring low-temperature curing after covering the device modulation area. Compared to process A, process B eliminates the electrode evaporation step, avoiding the impact of the high temperature of the evaporation process on the properties of the piezoelectric film.

[0132] Specifically, in this embodiment, the upper surface of the cured piezoelectric film is the exposed surface, on which an upper electrode layer needs to be fabricated, and a lower electrode layer has been pre-fabricated at the bottom of the piezoelectric layer below it. When spin-coating photoresist on its exposed surface, a commonly used positive photoresist is selected, and the thickness is controlled between 0.5-20 μm according to the linewidth requirements of the upper electrode layer. When the linewidth is large, a thicker photoresist layer is used to enhance the etching resistance, and when the linewidth is small, a thinner photoresist layer is used to improve the resolution.

[0133] The spin coating process is carried out in two stages. First, the photoresist is spread evenly at a low speed for 5-10 seconds. Then, it is spin coated at a high speed for 30-60 seconds to control the thickness. After that, it is baked at 90-110℃ for 1-2 minutes to enhance the adhesion of the photoresist layer.

[0134] Next, ultraviolet exposure is performed using an electrode pattern mask corresponding to the upper electrode layer pattern. Alignment is completed on a dedicated alignment device, with the electrode pattern markings and device structure markings on the mask observed under a microscope. The position and angle are finely adjusted to ensure the upper electrode layer to be retained is directly above the waveguide modulation arm, with an alignment deviation not exceeding 1 μm. After alignment, exposure is performed, with the exposure energy adjusted to 80-150 mJ / cm² depending on the photoresist thickness. After exposure, the mask is treated with the accompanying developer and developed at room temperature for 30-60 seconds to remove unwanted photoresist areas, forming a patterned photoresist layer. The mask is then rinsed and dried.

[0135] Subsequently, the exposed prefabricated upper electrode layer is etched using patterned photoresist as a mask. The upper and lower electrodes are typically made of metal or transparent conductive materials, with a thickness of 100-500 nm. The etching is performed at 25-40°C for 10-90 seconds, and the reaction is terminated immediately after etching by rinsing.

[0136] Finally, remove the remaining photoresist by soaking in acetone or treating with a special stripping solution. After rinsing and drying, the pre-set upper electrode layer pattern is formed, and the fabrication is completed. The resulting electrode must ensure linewidth accuracy and surface conductivity.

[0137] Specifically, in this embodiment, after the above-mentioned electrodes and piezoelectric thin film are integrated, the MZ optical waveguide structure is directly cut using a diamond dicing machine at a cutting speed of 5 mm / s and a blade thickness of 0.1 mm. The cutting is perpendicular to the input and output straight waveguides along the projection direction and intersects perpendicularly with the La segment input waveguide, thus obtaining a silicon nitride hetero-integrated optical waveguide acousto-optic switch.

[0138] Specifically, in this embodiment, a single-mode optical fiber, a photodetector, a signal generator, and an oscilloscope are connected to a silicon nitride heterointegrated optical waveguide acousto-optic switch for testing, and the switching time and power consumption are recorded.

[0139] Example 2 of a polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch See Figure 1-2 In this embodiment, a commercial Rockchip substrate wafer with a three-layer film structure projected as a rectangle in the vertical direction is selected as the substrate chip. The substrate wafer has a thickness of 693µm, a length L1 of 3cm, and a width x1 of 2cm. The three-layer film structure consists of three layers from top to bottom: the top layer is high-refractive-index silicon nitride with a refractive index of 2.0 and a thickness of d3=1µm; the second layer is low-refractive-index silicon dioxide with a refractive index of 1.445 and a thickness of d2=8µm; and the third layer is a silicon-based silicon dioxide layer with a thickness of 675µm.

[0140] In this embodiment, a mask layer is evaporated on the wafer. The mask layer material is aluminum (Al) with a thickness of d4=2nm. Photoresist is then spin-coated to form a photoresist thin film layer with a thickness of 1.5µm. The spin-coating speed is 3000rpm and the time is 30s.

[0141] This embodiment uses a photomask and a photolithography machine, or a maskless photolithography machine, to import the pattern for photolithography. The photomask is a straight waveguide pattern; see the model below. Figure 4 Its waveguide length L2 = 1000µm and waveguide structure width x2 = 1µm. The long side of the waveguide is parallel to the long side of the wafer structure. The distance between the long side of the waveguide and the long side of the wafer in the x direction is 100µm. In the z direction, it intersects the two short sides perpendicularly, that is, the length in the z direction is greater than the length of the long side of the wafer.

[0142] In this embodiment, the photolithography exposure intensity is 20mW / cm² and the time is 8s. The photoresist is then developed in the corresponding developer for 30s to obtain a photoresist mask layer.

[0143] See Figure 3 In this embodiment, a photoresist mask layer is used as a shield, and then a NaOH solution with a concentration of 2.5-10‰ is used as a mask etching reagent to etch the silicon nitride waveguide mask layer into the corresponding pattern. The development time depends on the thickness of the silicon nitride waveguide mask layer. Then, the photoresist mask layer is rinsed with isopropanol and deionized water to obtain the waveguide mask pattern.

[0144] See Figure 23 In this embodiment, the waveguide core layer is obtained by ICP etching, and the etching depth is d3=1µm.

[0145] In this embodiment, the photoresist mask layer is removed using a corresponding photoresist developer, and the waveguide mask pattern is removed using a corresponding solution. The development time is 5 seconds, resulting in a silicon nitride waveguide chip. (See [link to previous document]). Figure 5 .

[0146] In this embodiment, a thermosetting epoxy polymer cladding material is spin-coated onto a silicon nitride waveguide chip. The spin-coating speed is 2500~10000 rpm, and the spin-coating time is 30~300 s. (See also...) Figure 6 The figure shows a spin coating speed of 5000 rpm and a spin coating time of 60 s.

[0147] In this embodiment, a thermosetting polymer cladding material is spin-coated onto a silicon nitride waveguide chip and then cured. The curing oven is set with parameters of 60°C, 5 min, 90°C, and 10 min to obtain a polymer cladding film. The film thickness d6 = 3 µm, which is 2 µm higher than d3. (See [link to relevant documentation]). Figure 24 .

[0148] See Figure 6-15 In this embodiment, a chromium adhesion layer, a lithium niobate piezoelectric layer, and a silver upper electrode are sequentially deposited on a 500nm thick aluminum lower electrode. The chromium adhesion layer has a thickness of 8nm, the lithium niobate piezoelectric layer has a thickness of 4μm, and the silver upper electrode has a thickness of d9=150nm, thus ensuring that the alignment deviation between the upper and lower electrodes is ≤0.6μm, covering the silicon nitride modulation arm. The front view of the multilayer stacked structure is shown below. Figure 15 As shown.

[0149] In this embodiment, after cleaning the lower electrode, a 0.4 μm thick low-temperature curing adhesive was used to bond the piezoelectric layer to the polymer dome, covering it 6 μm beyond the electrode edge. After curing at 90°C, there were no interlayer gaps. The front view of the structure after the piezoelectric layer covers the electrode is shown below. Figure 16 As shown.

[0150] In this embodiment, a 1.8 μm thick polymer encapsulation layer was spin-coated at 6500 rpm, and the lead and port encapsulation material was removed by photolithography. The front view of the structure after electrode-piezoelectric layer encapsulation is shown below. Figure 17 As shown.

[0151] In this embodiment, a 1.8 μm thick positive photoresist is spin-coated onto the surface of the upper electrode. After pre-baking, alignment, exposure, and development, the exposure energy is 100 mJ / cm². The front view of the patterned photoresist structure is shown below. Figure 18 As shown.

[0152] See Figure 25In this embodiment, the thickness of the spin-coated polymer coating is d7 = 4.5µm, which is 1.5µm thicker than d6. Electrode material is then deposited onto the coating material to obtain an electrode material layer with a thickness d8 = 500nm. The front view after spin-coating the coating material and depositing the electrode material is shown below. Figure 17 As shown.

[0153] See Figure 18 In this embodiment, a photoresist layer is spin-coated onto the electrode material layer at a spin speed of 5000 rpm for 60 s to obtain an electrode material mask layer with a thickness of 2 µm. Subsequently, a mask plate with electrode patterns is covered on the photoresist, or the electrode patterns are introduced using a maskless lithography machine, and alignment is performed on a maskless lithography machine.

[0154] See Figure 10 , Figure 19-20 In this embodiment, the middle strip structure of the mask with electrode patterns has a width of x7 = 3µm and a length of L6 = 0.5mm, ensuring that the straight electrode portion is completely parallel and covers one arm of MZ. The electrode leads adopt a same-side structure, with two identical leads extending outward from the two endpoints of the straight electrode structure. The distance between the lead structure and the strip structure in the x-direction is x8 = 1.5µm, and the electrode leads are rectangular in the z-direction with a length of L7 = 10µm and a width of x9 = 10µm. Photolithography is then performed with an exposure intensity of 25mW / cm² and a time of 8s. After photolithography, the mask is removed, and the photoresist material layer and electrode layer are etched using a 5‰ sodium hydroxide aqueous solution. The photoresist layer on the electrodes is removed using acetone to obtain the electrode pattern layer.

[0155] See Figure 21-22 In this embodiment, a dicing machine is used to directly cut the waveguide perpendicular to the input and output straight waveguides (a) along the projection direction and parallel to L. a The input waveguides intersect perpendicularly to form a silicon nitride heterogeneous acousto-optic switch with input and output interfaces. Finally, it is connected to an optical fiber, photodetector, signal generator, and oscilloscope for testing to verify the feasibility of the results.

[0156] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch, characterized in that, include: A substrate chip, comprising an inorganic substrate layer, an inorganic waveguide cladding layer, and a waveguide core layer, wherein an MZ optical waveguide structure layer is formed on the waveguide core layer; The MZ optical waveguide structure layer is provided with a polymer cladding, which is a dome structure and has a driving layer on it. The waveguide core layer is a silicon nitride waveguide core layer with an MZ structure, which is obtained by etching a silicon nitride layer in the substrate chip.

2. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 1, characterized in that: The substrate chip is formed by sequentially comprising the waveguide core layer, the inorganic waveguide cladding layer and the inorganic substrate layer from top to bottom, thereby forming a silicon nitride waveguide chip. The waveguide core layer is a high-refractive-index silicon nitride layer with a refractive index of 1.9 to 2.

5. The inorganic waveguide cladding is a low-refractive-index silicon dioxide layer with a refractive index of 1.44~1.

45. The substrate layer is made of silicon, glass, or silicon dioxide.

3. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 2, characterized in that, The fabrication steps of the silicon nitride waveguide core layer with the MZ structure include: A substrate chip is selected, wherein the substrate chip is rectangular when projected in the vertical direction; To obtain the silicon nitride layer with a high refractive index; A silicon nitride waveguide mask layer for fabricating the silicon nitride waveguide core layer is fabricated on the substrate chip. Photoresist is spin-coated onto the silicon nitride waveguide mask layer to form a photoresist thin film layer; An MZ pattern is introduced onto the photoresist thin film layer, and photolithography and development are performed using an MZ photomask to obtain a photoresist mask layer. The MZ pattern is a branched, parallel, and coupled structure based on silicon nitride waveguides.

4. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 3, characterized in that: The MZ photomask includes an input / output region, a Y-branch region, and a straight waveguide pattern. The input / output region is a strip-shaped straight waveguide, and the length of the strip-shaped straight waveguide in the z-direction is greater than the long side of the substrate chip. The waveguide width of the Y-branch region is the same as that of the strip waveguide, the length of the Y-branch region is its length along the propagation direction of the input / output region, and its width is the distance between the two strip waveguides. The long side of the straight waveguide pattern is arranged parallel to the long side of the substrate chip.

5. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 3, characterized in that, The fabrication steps of the silicon nitride waveguide core layer with the MZ structure further include: The photoresist mask layer is used for masking; The silicon nitride waveguide mask layer is etched with a corresponding mask etching reagent to obtain a waveguide mask pattern, which is the same as the pattern of the photoresist mask layer. The silicon nitride layer is obtained by plasma etching or ICP etching, and the etching depth is equal to the thickness of the silicon nitride layer. The waveguide mask pattern and the photoresist mask layer are removed to obtain the silicon nitride waveguide core layer with an MZ structure.

6. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 2, characterized in that, The preparation steps of the polymer coating include: A polymer cladding material is spin-coated or imprinted onto the silicon nitride waveguide chip; The appropriate curing method is selected based on the material properties of the polymer coating material to prepare the polymer coating film; The polymer cladding film forms a dome structure on the top layer; The polymer cladding film is photolithographically etched and then developed to form a polymer cladding covering the silicon nitride waveguide core MZ structure.

7. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 1, characterized in that, The driving layer includes an electrode layer, the electrode layer having an electrode pattern layer formed thereon, and the steps include: A photoresist layer is spin-coated onto the electrode layer to obtain an electrode material mask layer; An electrode pattern mask with electrode patterns is placed on the electrode material mask layer, and photolithography is performed. Remove the electrode pattern mask, and use a corresponding photoresist developer to remove the photoresist layer and a corresponding electrode etchant to etch the electrode material mask layer, thereby obtaining the electrode pattern layer.

8. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 7, characterized in that: The electrode pattern mask has a strip structure in the middle, which is used to make the straight electrodes of the electrode layer parallel and cover the silicon nitride modulation arm in the MZ optical waveguide structure layer. The electrode pins of the straight electrode adopt a same-side lead-out structure, with both ends extending outward along the extension direction perpendicular to the straight electrode.

9. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 7, characterized in that: The driving layer also includes an adhesive layer and a piezoelectric layer, which are integrated through process A or process B. The piezoelectric layer is a piezoelectric thin film, which includes an adhesive surface for contacting the adhesive layer and an exposed surface. If process A is used, the lower electrode layer, the adhesive layer, the piezoelectric layer and the upper plate electrode layer are sequentially integrated above the driving layer; if process B is used, the adhesive layer, the lower plate electrode layer and the piezoelectric layer and the upper electrode layer are sequentially integrated above the driving layer. Wherein, the lower electrode layer or the upper electrode layer is the electrode layer on which the electrode pattern layer is formed.

10. The polymer silicon nitride heterogeneously integrated MZ optical waveguide acousto-optic switch according to claim 9, characterized in that: The steps of process A include: A lower electrode layer with a single-surface structure is formed on the polymer coating; The lower electrode layer obtains the lower electrode pattern according to the formation steps of the electrode pattern layer; A single-surface structure upper plate electrode layer is prepared on the exposed surface of the piezoelectric thin film; The adhesive surface of the piezoelectric film is adhered to the surface of the polymer coating through the adhesive layer and then cured at low temperature. The steps of process B include: Electrodes are pre-formed on both sides of the piezoelectric thin film; Using one side of the piezoelectric film as the adhesive surface, it is adhered to the surface of the polymer coating through the adhesive layer and then cured at low temperature. Using the other side of the piezoelectric film as the upper electrode layer, the upper electrode pattern is obtained according to the steps of forming the electrode pattern layer.

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