Optical waveguide and preparation method therefor

Abstract

An optical waveguide and a preparation method therefor. The optical waveguide comprises: an optical waveguide layer (02), and a modulation layer (03) located on the optical waveguide layer (02), wherein a first isolation layer (04) is provided between the optical waveguide layer (02) and the modulation layer (03), the modulation layer (03) being covered with a first protective layer (05). The optical waveguide further comprises: a second isolation layer (06) surrounding the first isolation layer (04) and the modulation layer (03), and a second protective layer (07) surrounding the first protective layer (05), the second isolation layer (06), and the optical waveguide layer (02). The modulation layer (03) is wrapped in a sealed cavity formed by enclosure of the first protective layer (05), the first isolation layer (04) and the second isolation layer (06), and the modulation layer (03) is a phase-change material layer or the modulation layer (03) comprises a phase-change material layer.

Description

Optical waveguide and preparation method thereof

[0001] Priority application

[0002] This application claims priority to the Chinese invention patent application [Application Number: 202311846859X] [Invention Title: An optical waveguide and its preparation method] filed on December 29, 2023; and the Chinese invention patent application [Application Number: 2023118490201] [Invention Title: An optical waveguide and its preparation method] filed on December 29, 2023. Both priority invention patent applications are incorporated by reference in their entirety. Technical Field

[0003] The present invention relates to an optical waveguide, and in particular to an optical waveguide and a preparation method thereof. Background Art

[0004] In photonic circuits, light can be controllably guided through optical waveguide networks using various optical switching and power splitting devices. Such devices typically operate by controlling the phase of light in the waveguide. For example, microring resonators and Mach-Zehnder interferometers (MZIs) can achieve optical switching and power splitting functions by tuning the phase of a silicon-on-insulator (SOI) waveguide. In addition, directional couplers can temporarily couple different amounts of light between closely spaced waveguides by tuning their relative phase. Phase shifting mechanisms are typically based on thermo-optical effects or free-carrier dispersion effects. However, due to the weak perturbation of the refractive index, the waveguide length in such devices is relatively long to achieve the desired phase shift. For example, an MZI can achieve the desired π phase shift at approximately 500 μm. Microrings are small in size, but their operating bandwidth is limited by the resonance conditions. Another approach is to use a micro-electromechanical system (MEMS) switch in a photonic circuit, in which each coupled waveguide can be mechanically moved to adjust the coupling efficiency. However, compared to traditional non-mechanical methods, this method has a slow switching speed (on the order of milliseconds), is not compact, and has relatively high manufacturing costs and complexity. Importantly, the above technology has problems with instability and short service life. That is, the state of the device that controls the phase of light needs to be maintained at a constant power consumption, and the lifespan of the MEMS is limited due to its inherent mechanical structure. Phase-change materials (PCMs) are inherently non-volatile and have been widely used in photonic applications, including photonic storage devices, rewritable optical discs, filters, displays, and optical switches. PCMs can be easily deposited on any substrate using standard methods and can switch back and forth between amorphous and crystalline states at high speed and for a long time. When switching between the amorphous and crystalline states, the refractive index changes dramatically. Compact optical switches with Ge2Sb2Te5 (GST) and Ge2Sb2Se4Te1 (GSST) on top of waveguide couplers have been demonstrated to have high switching speeds (100 nanoseconds) and low power consumption. Therefore, PCM-based photonic devices offer several advantages over conventional photonic switching schemes and are promising for the development of large-scale non-volatile, reprogrammable photonic routing systems, such as field-programmable coupler arrays.

[0005] Based on this, the prior art has proposed a new optical waveguide. For example, the Chinese invention patent application with application number CN202180043314.8 provides a phase change material layer on the optical waveguide that has low absorption loss in the amorphous state (i.e., the extinction coefficient is substantially less than 0.1) and a large difference in optical coefficients between the crystalline and amorphous states. The phase change material layer can switch between at least two stable solid states: amorphous and crystalline. However, the stability of the optical waveguide with this structure still needs to be improved.

[0006] Summary of the Invention

[0007] The object of the present invention is to provide an optical waveguide and a method for preparing the same, which partially solve or alleviate the above-mentioned deficiencies in the prior art. The stability of the modulation layer in the optical waveguide when switching between the amorphous state and the crystalline state is more reliable.

[0008] To solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions: In a first aspect, the present invention provides an optical waveguide, comprising: an optical waveguide layer; a modulation layer located on the optical waveguide layer; a first isolation layer disposed between the optical waveguide layer and the modulation layer; and a first protective layer covering the modulation layer. The present invention also includes: a second isolation layer surrounding the first isolation layer and the modulation layer and having an inverted L-shaped cross-section; and a second protective layer surrounding the first protective layer, the second isolation layer, and the optical waveguide layer. The modulation layer is enclosed in a sealed cavity formed by the first protective layer, the first isolation layer, and the second isolation layer, and the modulation layer is a phase change material layer or includes a phase change material layer.

[0009] In some embodiments, the first and second isolation layers together form a second groove opening toward the first protective layer. The height from the bottom of the second groove to the top opening is greater than or equal to the thickness of the modulation layer. In some embodiments, the second groove is formed by regionally etching the second isolation layer, which has a T-shaped or concave cross-section and is pre-overlaid on the optical waveguide layer, and the second protective layer overlying the optical waveguide layer and the second isolation layer. In some embodiments, the phase change material layer is formed by sputtering the phase change material onto the first isolation layer; and / or the first protective layer is deposited onto the phase change material layer by physical vapor deposition or chemical vapor deposition. In some embodiments, the upper surface of the first protective layer is flush with the upper surface of the second protective layer. In some embodiments, the thickness of the first isolation layer is 1 nm to 100 nm. In some embodiments, the length of the first isolation layer extending along the length of the optical waveguide is 1 μm to 10 μm. In some embodiments, the thickness of the first protective layer is 0.1 μm to 3 μm. In some embodiments, the thickness of the modulation layer is 1 nm to 1 μm. In some embodiments, the modulation layer extends along the length of the optical waveguide for a length of 1 μm to 10 μm. In some embodiments, the phase-change material layer is made of a superlattice material. In some embodiments, the phase-change material layer is formed of a chalcogenide containing antimony or selenium. In some embodiments, the phase-change material layer comprises the chalcogenide, wherein the chalcogenide comprises Sb2Se3 or SbSe, Sb2S3 or SbS, or Ge2Sb2Se4Te. In some embodiments, the phase-change material of the phase-change material layer comprises a compound or alloy containing an elemental combination of germanium, antimony, selenium, and vanadium oxide, or a mixture of the compounds; the compounds include: NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb. In some embodiments, the optical waveguide includes a metal interconnect layer embedded in the second protective layer; and / or the optical waveguide layer has a rectangular or convex cross-section. In some embodiments, the first protective layer is made of one or more of SiO2, Al2O3, and ITO. In some embodiments, the second protective layer is made of one or more of SiO2, Al2O3, and ITO. In some embodiments, the first isolation layer is made of one or both of Si3N4 and TiN.

[0010] A second aspect of the present invention is to provide a method for preparing the above-mentioned optical waveguide, comprising the steps of: S1021, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1023, forming a second stop layer of a third thickness and a second oxide layer of a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition; wherein the second stop layer is located above the optical waveguide layer, and its cross-section is T-shaped or concave-shaped, and the width of the vertical portion of the T-shaped second stop layer is greater than the width of the optical waveguide layer, or the width of the concave-shaped second stop layer is greater than the width of the optical waveguide layer; S1025, performing a windowing process on the second stop layer and the second oxide layer by a regional etching method, so that The second stop layer forms a first isolation layer of the fourth thickness on the optical waveguide layer, and a second isolation layer surrounding the first isolation layer and having an inverted L-shaped cross-section; wherein the fourth thickness is less than the third thickness; S1027, a first thin film deposition process is used to deposit a phase change material onto the surface of the first isolation layer by a physical vapor deposition method, so as to form a phase change material layer of a preset thickness in a window formed by the first isolation layer and the second isolation layer around it; the preset thickness is less than or equal to the difference between the third thickness and the fourth thickness; S1029, a second thin film deposition process is used to deposit an oxide layer of the same material as that in step S1013 onto the phase change material layer to cover it, thereby obtaining a first protective layer of the sixth thickness.

[0011] A third aspect of the present invention provides an optical waveguide, comprising: an optical waveguide layer; a modulation layer located on the optical waveguide layer; a first isolation layer disposed between the optical waveguide layer and the modulation layer; and a first protective layer covering the modulation layer. The optical waveguide layer further comprises: a second isolation layer surrounding the first isolation layer and a first region of the modulation layer proximate to the first isolation layer; and a second protective layer surrounding the first protective layer, a second region of the modulation layer proximate to the first protective layer, the second isolation layer, and the optical waveguide layer. The modulation layer is enclosed in a sealed cavity formed by the first protective layer, the second protective layer, the first isolation layer, and the second isolation layer, and the modulation layer includes or is a phase change material layer.

[0012] In some embodiments, the first protective layer and the second protective layer surrounding the first protective layer and the second region of the modulation layer together form a first groove with an inverted concave cross-section; the first isolation layer and the second isolation layer surrounding the first isolation layer and the first region of the modulation layer together form a second groove with a concave cross-section, and the opening of the first groove and the opening of the second groove are arranged opposite each other, such that the first groove and the second groove together form the sealed cavity with a rectangular cross-section. In some embodiments, the first protective layer and the second protective layer surrounding the first protective layer and the second region of the modulation layer together form a first groove with an inverted U-shaped cross-section; the first isolation layer and the second isolation layer surrounding the first isolation layer and the first region of the modulation layer together form a second groove with a U-shaped cross-section, and in the same cross-section, the spacing between the opposing sidewalls of the first groove gradually decreases toward the optical waveguide layer, while the spacing between the opposing sidewalls of the second groove gradually increases away from the optical waveguide layer, and the opening of the first groove and the opening of the second groove are arranged opposite each other, such that the sidewalls of the first groove and the sidewalls of the second groove are smoothly connected, enclosing the sealed cavity with a bowl or trumpet shape. In some embodiments, the first isolation layer is formed by etching the second protective layer and the second isolation layer, which are pre-coated on the optical waveguide layer, using a regional etching method to form a cavity bottom with an open top. In some embodiments, the phase-change material layer is formed by sputtering a phase-change material onto the first isolation layer. In some embodiments, the first protective layer is deposited on the modulation layer using physical vapor deposition or chemical vapor deposition. In some embodiments, the upper surface of the first protective layer is flush with the upper surface of the second protective layer. In some embodiments, the thickness of the first isolation layer is 1 nm to 100 nm. In some embodiments, the length of the first isolation layer extending along the length of the optical waveguide is 1 μm to 10 μm. In some embodiments, the thickness of the first protective layer is 0.1 μm to 3 μm. In some embodiments, the thickness of the modulation layer is 1 nm to 1 μm. In some embodiments, the length of the modulation layer extending along the length of the optical waveguide is 1 μm to 10 μm. In some embodiments, the phase-change material layer is made of a superlattice material. In some embodiments, the phase-change material layer is formed of a chalcogenide containing antimony or selenium. In some embodiments, the phase change material layer contains the chalcogenide compound, wherein the chalcogenide compound includes Sb2Se3 or SbSe, Sb2S3 or SbS, Ge2Sb2Se4Te.In some embodiments, the phase change material of the phase change material layer includes a compound or alloy containing a combination of elements such as germanium, antimony, selenium, and vanadium oxide, or a mixture of such compounds; the compounds include: NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb. In some embodiments, the optical waveguide includes a metal interconnect layer embedded in the second protective layer; and / or the cross-section of the optical waveguide layer is rectangular or convex. In some embodiments, the first protective layer is made of any one or more of SiO2, Al2O3, and ITO. In some embodiments, the second protective layer is made of any one or more of SiO2, Al2O3, and ITO. In some embodiments, the first isolation layer is made of one or both of Si3N4 and TiN. In some embodiments, the second isolation layer is made of one or both of Si3N4 and TiN.

[0013] A fourth aspect of the present invention is to provide a method for preparing the above-mentioned optical waveguide, comprising the steps of: S1011, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1013, forming a second stop layer of a first thickness and a second oxide layer of a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition, wherein the second stop layer is located above the optical waveguide layer and has a width greater than that of the optical waveguide layer; S1015, performing a windowing process on the second stop layer and the second oxide layer by a regional etching method, so that the second stop layer is The stop layer forms a first isolation layer of a fourth thickness on the optical waveguide layer, and a second isolation layer surrounding the first isolation layer, wherein the fourth thickness is less than the first thickness; S1017, using a first thin film deposition process to deposit a phase change material onto the surface of the first isolation layer exposed in the window by a physical vapor deposition method, to form a phase change material layer of a preset thickness; the sum of the preset thickness and the fourth thickness is greater than the first thickness; S1019, using a second thin film deposition process to deposit an oxide layer of the same material as in step S1013 onto the phase change material layer to cover it, to obtain a first protective layer of a sixth thickness.

[0014] A fifth aspect of the present invention is to provide a method for preparing an optical waveguide, comprising the steps of: S1021, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1023, forming a second stop layer of a fourth thickness and a second oxide layer of a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition; wherein the second stop layer is located above the optical waveguide layer, and its cross-section is T-shaped or concave-shaped, and the width of the vertical portion of the T-shaped second stop layer is greater than the width of the optical waveguide layer, or the width of the concave-shaped second stop layer is greater than the width of the optical waveguide layer; wherein the fourth thickness is 1 nm to 100 nm; S1025, etching the second stop layer and the second oxide layer by a regional etching method. The windowing process of the second oxide layer is performed, so that the second stop layer forms a first isolation layer having a thickness less than the fourth thickness on the optical waveguide layer, and a second isolation layer surrounding the first isolation layer and having an inverted L-shaped cross-section. In step S1027, a phase change material is deposited onto the surface of the first isolation layer by physical vapor deposition using a first thin film deposition process to form a phase change material layer of a predetermined thickness within the window formed by the first isolation layer and the surrounding second isolation layer. The predetermined thickness is less than or equal to the difference between the fourth thickness and the thickness of the first isolation layer. In step S1029, an oxide layer of the same material as in step S1013 is deposited onto the phase change material layer using a second thin film deposition process to cover the phase change material layer, thereby forming a first protective layer of a sixth thickness. In some embodiments, the fourth thickness is pre-determined through simulation. In some embodiments, the length of the first isolation layer extending along the length of the optical waveguide is 1 μm to 10 μm. In some embodiments, the thickness of the phase change material layer is 1 nm to 1 μm. In some embodiments, the length of the phase change material layer extending along the length of the optical waveguide is 1 μm to 10 μm.

[0015] A sixth aspect of the present invention is to provide an optical waveguide prepared using the above-mentioned method for preparing an optical waveguide, comprising: an optical waveguide layer; a modulation layer located on the optical waveguide layer; a first isolation layer disposed between the optical waveguide layer and the modulation layer; a first protective layer covering the modulation layer; and a second isolation layer surrounding the first isolation layer and the modulation layer, the second isolation layer having an inverted L-shaped cross-section, and a second protective layer surrounding the first protective layer, the second isolation layer, and the optical waveguide layer. The modulation layer is enclosed in a sealed cavity formed by the first protective layer, the first isolation layer, and the second isolation layer, and the modulation layer is a phase change material layer or includes a phase change material layer. The thickness of the first isolation layer is less than a fourth thickness, and the fourth thickness is between 1 nm and 100 nm. In some embodiments, the first isolation layer and the second isolation layer together form a second groove opening toward the first protective layer, and the height from the bottom to the top opening of the second groove is greater than or equal to the thickness of the modulation layer.

[0016] A seventh aspect of the present invention is to provide a method for preparing an optical waveguide, comprising the steps of: S1011, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1013, forming a second stop layer of a fourth thickness and a second oxide layer of a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition, wherein the second stop layer is located above the optical waveguide layer and has a width greater than that of the optical waveguide layer; the fourth thickness is 1 nm to 100 nm; S1015, performing windowing on the second stop layer and the second oxide layer by a regional etching method. process, so that the second stop layer forms a first isolation layer having a thickness less than the fourth thickness on the optical waveguide layer, and the second isolation layer surrounding the first isolation layer; S1017, using a first thin film deposition process to deposit a phase change material onto the surface of the first isolation layer exposed in the window by a physical vapor deposition method, to form a phase change material layer of a preset thickness; the sum of the preset thickness and the thickness of the first isolation layer is greater than the fourth thickness; S1019, using a second thin film deposition process to deposit an oxide layer of the same material as in step S1013 onto the phase change material layer to achieve coverage, thereby obtaining a first protective layer of the sixth thickness.

[0017] In some embodiments, the length of the first isolation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm. In some embodiments, the thickness of the phase change material layer is 1 nm to 1 μm; and / or the length of the phase change material layer extending along the length direction of the optical waveguide is 1 μm to 10 μm. In some embodiments, the phase change material layer is made of a superlattice material. In some embodiments, the phase change material layer is formed of a chalcogenide containing antimony or selenium, or the phase change material layer contains the chalcogenide, wherein the chalcogenide includes Sb2Se3 or SbSe, Sb2S3 or SbS, or Ge2Sb2Se4Te. In some embodiments, the phase-change material comprises a compound or alloy containing a combination of elements selected from the group consisting of germanium, antimony, selenium, and vanadium oxides, or a mixture thereof; the compound comprises NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb. In some embodiments, the second oxide layer is made of one or more of SO2, Al2O3, and ITO. In some embodiments, the second stop layer is made of one or both of Si3N4 and TiN.

[0018] An eighth aspect of the present invention provides an optical waveguide prepared using the above-mentioned method for preparing an optical waveguide, comprising: an optical waveguide layer; a modulation layer located on the optical waveguide layer; a first isolation layer disposed between the optical waveguide layer and the modulation layer; and a first protective layer covering the modulation layer; and further comprising: a second isolation layer surrounding the first isolation layer and a first region of the modulation layer proximate to the first isolation layer; and a second protective layer surrounding the first protective layer, a second region of the modulation layer proximate to the first protective layer, the second isolation layer, and the optical waveguide layer; wherein the modulation layer is enclosed in a sealed cavity formed by the first protective layer, the second protective layer, the first isolation layer, and the second isolation layer, and the modulation layer includes a phase change material layer or is a phase change material layer; wherein the thickness of the first isolation layer is less than the fourth thickness, and the fourth thickness is in the range of 1 nm to 100 nm. In some embodiments, the first protective layer and the second protective layer surrounding the first protective layer and the second region of the modulation layer together form a first groove having an inverted concave cross-section; the first isolation layer and the second isolation layer surrounding the first isolation layer and the first region of the modulation layer together form a second groove having a concave cross-section, and the opening of the first groove and the opening of the second groove are arranged opposite each other, such that the first groove and the second groove together form the sealed cavity having a rectangular cross-section. In some embodiments, the first protective layer and the second protective layer surrounding the first protective layer and the second region of the modulation layer together form a first groove having an inverted U-shaped cross-section; the first isolation layer and the second isolation layer surrounding the first isolation layer and the first region of the modulation layer together form a second groove having a U-shaped cross-section, and in the same cross-section, the spacing between the opposing sidewalls of the first groove gradually decreases toward the waveguide layer, while the spacing between the opposing sidewalls of the second groove gradually increases away from the waveguide layer, and the opening of the first groove and the opening of the second groove are arranged opposite each other, such that the sidewalls of the first groove and the sidewalls of the second groove are smoothly connected, thereby enclosing the sealed cavity having a bowl or trumpet shape.

[0019] Beneficial effects: Currently, the main method for preparing integrated optical devices based on phase change materials on mature and available commercial SOI substrates is to deposit a variety of phase change materials directly on the upper surface of the optical waveguide layer (i.e., using an upward coupling method) or on the upper surface and sidewalls of the waveguide through advanced magnetron sputtering or thermal evaporation processes (compared to the upward coupling method; the phase change material layer is also deposited on the sidewalls of the optical waveguide layer, which will cause unevenness, resulting in many uncertainties in the subsequent optical coupling and phase change material modulation process). The sputtering of phase change materials can be achieved using a single target or co-sputtering of multiple targets (the composition and doping can be adjusted). Magnetron sputtering technology is a technology that uses charged particles to bombard the target surface in a vacuum, so that the bombarded particles are deposited on the substrate. After sputtering a layer of phase change material thin film on the surface using magnetron sputtering technology, an oxide layer is sputtered for protection. Although this method can achieve heterogeneous integration of phase change materials and optical waveguides, there are still two problems:

[0020] On the one hand, the stability of the structure itself needs to be improved. 1. The oxide layer sputtered after the phase change material is very thin (10nm to 30nm), and the oxide layer is sputtered immediately after the phase change material. It only covers the upper surface of the phase change material layer and cannot completely wrap the phase change material. Naturally, its protective effect is low. 2. After modulation (melting / recrystallization), the phase change material has fluidity after melting and will move a certain distance. It is precisely because there is only a thin oxide layer on its surface that it is actually impossible to control the change area of ​​the phase change material after modulation. As a result, there may be problems of material separation or even volatilization, which in turn leads to instability when the modulation layer in the structure switches between the amorphous and crystalline states. On the other hand, it is difficult to achieve commercialization (for example, industrial production) and can only be used for scientific research. Because in industrial production, the chip generally also contains an oxide layer on the surface of the optical waveguide and a metal interconnection layer embedded in the oxide layer. Due to the limitations of the existing front-end and back-end processes, phase change materials cannot be directly added to the chip manufacturing process, that is, the above-mentioned method of sputtering the phase change material layer directly on the waveguide layer cannot be directly applied to industrial production. Specifically, the existing chip manufacturing process is mainly divided into front-end and back-end processes. The front-end process includes wafer processing, oxidation process, photolithography, etching, deposition and doping / ion implantation, while the back-end process mainly forms the metal interconnection layer on the chip. Due to the many technical difficulties and complex operations of the front-end process, in order to avoid pollution, phase change materials are not allowed to be integrated on the waveguide in the front-end process. The dielectric layer and metallization in the back-end process require a higher operating temperature, which will affect the stability of the phase change material integration in this high temperature environment. Therefore, the phase change material is not allowed to be placed before the metallization. In other words, the industrial production of optical waveguides with this structure is more difficult.

[0021] Based on this, the present invention provides a new structure of optical waveguide, which has higher structural stability and is conducive to commercialization. Specifically, in order to avoid damage to the optical waveguide layer during the windowing process, a first isolation layer is provided between the optical waveguide layer and the modulation layer. Moreover, in order to better wrap the modulation layer, the modulation layer is provided in a cavity formed by the first isolation layer and the second isolation layer, and is covered by the first protective layer. That is, the first isolation layer, the second isolation layer and the first protective layer define the movement space of the modulation layer during the switching of different states (for example, the first isolation layer and the second isolation layer form a wrapping layer that almost completely wraps the modulation layer, and is covered by the first protective layer to define the movement space of the modulation layer during the switching of different states), thereby ensuring the integrity and stability of the modulation layer, thereby reducing the irreversible damage of the phase change material and extending the service life of the phase change material. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the embodiments or the description of the prior art. In all drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the various elements or parts are not necessarily drawn according to the actual scale. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without inventive work.

[0023] FIG1a is a schematic diagram of a cross-sectional structure of an optical waveguide according to an exemplary embodiment of the present invention;

[0024] FIG1b is an exploded view of the optical waveguide shown in FIG1a;

[0025] FIG1c is a schematic diagram of a cross-sectional structure of an optical waveguide according to another exemplary embodiment of the present invention;

[0026] FIG1d is an exploded view of the optical waveguide shown in FIG1c;

[0027] FIG1e is a schematic diagram of the cross-sectional structure of an optical waveguide according to another exemplary embodiment of the present invention;

[0028] FIG1f is an exploded view of the optical waveguide shown in FIG1e;

[0029] FIG2 a is a flow chart of a method for preparing an optical waveguide according to an exemplary embodiment of the present invention;

[0030] FIG2b is a flow chart of preparing the optical waveguide of the structure shown in FIG1a using the optical waveguide preparation method of the present invention;

[0031] FIG2c is a flow chart of preparing the optical waveguide of the structure shown in FIG1c using the optical waveguide preparation method of the present invention;

[0032] 3a to 3e are schematic diagrams of preparing an optical waveguide according to the method shown in FIG2 , taking a strip waveguide layer as an example;

[0033] 3f to 3j are schematic diagrams of preparing an optical waveguide according to the method shown in FIG2 , taking a strip waveguide layer as an example;

[0034] FIG4 is a diagram of optical power of a cyclically modulated optical waveguide (i.e., a control group) prepared using an existing integrated phase change material method;

[0035] FIG5 is a diagram of optical power obtained by cyclically modulating the optical waveguide (ie, the experimental group) using the method shown in FIG3a to FIG3e.

[0036] Summary of reference numerals: 01 substrate; 02 optical waveguide layer; 03 phase-change material layer: 031 second region, 032 first region; 04 first isolation layer; 05 first protective layer; 06 second isolation layer; 07 second protective layer; 5 metal interconnection layer; 001 sealed cavity, 0011 first groove, 0012 second groove; H0 height of the phase-change material layer extending along the Z-axis direction (or preset thickness); H1, H3 height of the second stop layer extending along the Z-axis direction (or first thickness, third thickness) in different embodiments; H2 height of the second oxide layer extending along the Z-axis direction (or second thickness) in different embodiments; H4 height of the first stop layer (or first isolation layer) extending along the Z-axis direction (or fourth thickness); H6 height of the first oxide layer extending along the Z-axis direction (or sixth thickness); h1 height of the opening of the first groove; h2 height of the opening of the second groove (h2>h1). DETAILED DESCRIPTION

[0037] To further clarify the objectives, technical solutions, and advantages of the embodiments of the present invention, the technical solutions of the embodiments of the present invention will be described in detail below, in conjunction with the accompanying drawings. It should be understood that the described embodiments represent only a portion of the embodiments of the present invention, and not all of them. 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. The use of suffixes such as "module," "component," or "unit" to designate components herein is solely for the purpose of facilitating the description of the present invention and does not inherently have specific meanings. Therefore, "module," "component," or "unit" may be used interchangeably. Terms such as "upper," "lower," "inner," "outer," "front," "rear," "one end," and "the other end" herein, indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are intended solely to facilitate and simplify the description of the present invention. They are not intended to indicate or imply that the devices or components referred to must have, be constructed, or operate in a specific orientation, and are therefore not to be construed as limiting the present invention. Furthermore, the terms "first" and "second" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance. As used herein, unless otherwise expressly specified or limited, the terms "mounted," "disposed with," "connected," and the like should be broadly construed. For example, "connected" can refer to fixed, removable, or integral connections; it can refer to mechanical connections, direct connections, indirect connections via an intermediary, or internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention. As used herein, "and / or" includes any and all combinations of one or more of the listed items. As used herein, "plurality" means two or more, including two, three, four, five, and so on. As used herein, the term "approximately" typically means + / -5% of the stated value, more typically + / -4%, more typically + / -3%, even more typically + / -2%, even more typically + / -1%, and even more typically + / -0.5%. In this specification, certain embodiments may be disclosed in a range format. It should be understood that such descriptions of "being in a range" are merely for convenience and brevity and should not be construed as rigid limitations on the disclosed ranges. Thus, the description of a range should be considered to have specifically disclosed all possible subranges and individual numerical values ​​within that range. For example, the description of a range of 1-6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., as well as individual numbers within that range, such as 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0038] As used herein, "light" refers to electromagnetic radiation or electromagnetic waves with wavelengths in the ultraviolet (UV) to infrared (IR) range (e.g., between 10 nm and 100 μm) that can propagate in free space and be guided by a waveguide. "Stable state" as used herein means substantially stable under the standard temperature and pressure conditions specified by the National Institute of Standards and Technology (NIST). As used herein, an "optical waveguide layer" refers to any structure that confines light in one or more dimensions within or adjacent to its surface, thereby guiding the light in a direction of propagation parallel to its axis. A waveguide is formed from a series of layers / regions with different refractive indices, typically including an inner layer / region or core layer / region. The inner layer / region or core layer / region is made of a material with a higher refractive index than the surrounding (outer) layers / regions or cladding layers / regions. In this case, the waveguide confines light in two dimensions, for example, within a channel, in the thickness / growth direction and in the lateral / width direction perpendicular to the thickness / growth direction. The core layer / region and / or the cladding layer / region may be referred to as guiding layers that actively confine and guide light. As used herein, a "modulation layer" refers to any entity that affects the properties of light. Light properties include transmission, refraction, absorption, and the like. In some embodiments, the light modulation layer includes, or may be, a phase change material layer made of a phase change material.

[0039] The present invention proposes an optical waveguide with high stability and industrial production capabilities, comprising: an optical waveguide layer; and a modulation layer located on the optical waveguide layer. A first isolation layer is provided between the optical waveguide layer and the modulation layer to prevent damage to the optical waveguide layer during the windowing process, and the modulation layer is covered with a first protective layer. The modulation layer is made of a phase change material, or includes a phase change material layer (for ease of description, the phase change material layer is used as the modulation layer in the subsequent embodiments). In current industrial windowing processes, it is difficult to directly and perfectly open the window above the optical waveguide layer, that is, to sputter or deposit the modulation layer directly on the optical waveguide layer without completely damaging the waveguide layer during the windowing process. Therefore, each example herein employs an isolation layer provided on the optical waveguide layer to protect the optical waveguide layer (e.g., a first stop layer) while simultaneously encapsulating the modulation layer. For example, a first stop layer and a first oxide layer of specified thicknesses (e.g., a first stop layer of the first thickness H1 or the third thickness H3, and a first oxide layer of the second thickness H2) are pre-formed on the optical waveguide layer. Then, during the windowing process, the etching depth of the first stop layer is controlled by controlling the process parameters of the windowing process. This allows the first stop layer of the specified thickness (e.g., the fourth thickness H4) to remain on the optical waveguide layer, thereby forming a first isolation layer. This prevents certain damage to the optical waveguide while encapsulating the modulation layer to ensure its stability.

[0040] Generally speaking, when coupling upward, a modulation layer is directly applied to the upper surface of the optical waveguide layer. This optimizes the evanescent field range of the light in the waveguide, thereby optimizing the power range of the modulated optical signal. However, as previously mentioned, due to limitations in existing processes, it is difficult to perfectly apply the modulation layer directly without damaging the waveguide layer. Therefore, to avoid damage to the waveguide layer, an isolation layer is provided on the waveguide layer for protection. However, the placement of the isolation layer must also consider the modulation layer's effect on the evanescent field of the light in the waveguide. If the isolation layer is too thick, even with the same thickness and state, the evanescent field range it can influence will be reduced, thereby reducing the power range of the modulated optical signal. If the isolation layer is too thin, it is difficult to achieve a very thin thickness due to the limitations of existing windowing processes. Therefore, considering the modulation layer's effect on the evanescent field range of the light in the waveguide and damage to the waveguide layer, the thickness of the isolation layer is explored to ensure that the modulation layer is protected without significantly reducing the evanescent field range of the light in the waveguide layer. For example, the specific thickness is determined by simulation according to actual needs. Preferably, the thickness H4 of the isolation layer between the optical waveguide layer and the modulation layer is 1 nm to 100 nm.

[0041] Of course, it is also possible to pre-define a desired thickness, such as an isolation layer of thickness H4, directly on the optical waveguide layer. In the subsequent windowing process, the oxide layer can be directly etched away, that is, etching can be stopped when the isolation layer is visible. Since the isolation layer has a certain thickness, even a slight etching away of the isolation layer will not affect the optical waveguide. Instead, it reduces the thickness of the isolation layer, which is beneficial to the modulation layer's effect on the evanescent field of light in the optical waveguide layer. In particular, when the existing windowing process is limited and the thickness of the stop layer between the modulation layer and the optical waveguide layer cannot be directly reduced (e.g., less than 1 nm) by adjusting etching parameters, by pre-depositing the isolation layer to a specified thickness (e.g., the minimum value of the range: 1 nm), the thickness of the isolation layer can be further reduced by slightly over-etching the previously provided oxide layer. To facilitate description of the positional relationships between the various components of an optical waveguide, a three-dimensional coordinate system is constructed herein with the length of the optical waveguide as the Y-axis, the height as the Z-axis, and the width as the X-axis. A cross section refers to a section obtained by cutting the corresponding region of the optical waveguide along a vertical plane (i.e., the XZ plane).

[0042] Example 1: Referring to FIG1a , a schematic diagram of an optical waveguide structure according to an exemplary embodiment of the present invention is shown. Specifically, the optical waveguide structure comprises: a silicon oxide substrate 01, an optical waveguide layer 02, and a phase-change material layer 03 located on the optical waveguide layer 02. A first isolation layer 04 is disposed between the optical waveguide layer 02 and the phase-change material layer 03 (i.e., the modulation layer), and the phase-change material layer 03 is covered with a first protective layer 05. Preferably, the width of the first isolation layer 04 (i.e., the length extending along the X-axis), the width of the optical waveguide layer 02 (i.e., the length extending along the X-axis), and the width of the phase-change material layer 03 (i.e., the length extending along the X-axis) are identical.

[0043] Referring to FIG. 1a , a second isolation layer 06 is provided on a substrate 01 around a first isolation layer 04 and a first region 032 on a phase-change material layer 03 close to the first isolation layer 04 (i.e., a portion of the sidewall region around the bottom where the phase-change material layer 03 contacts the first isolation layer 04). A first thickness H1 of the second isolation layer 06 (i.e., a length extending in the Z-axis direction) is greater than a fourth thickness H4 of the first isolation layer 04, but less than the sum of the thicknesses of the phase-change material layer 03 and the first isolation layer 04 (i.e., the sum of H0 and H4). Thus, the first isolation layer 04 and the second isolation layer 06 enclose a first region 032 on the side of the phase-change material layer 03 close to the optical waveguide layer 02, which is wrapped upward (i.e., the peripheral edge of the wrapping component extends upward from the bottom of the wrapped component along the peripheral sidewall height direction thereof to form an enclosing sidewall). 2; and a second protective layer 07 is provided on the first protective layer 05, the phase-change material layer 03, and the second region 031 near the first protective layer 05 (i.e., a portion of the sidewall region around the top where the phase-change material layer 03 contacts the first protective layer 05), the second isolation layer 06, and the optical waveguide layer 02, so that the first protective layer 05 and the second protective layer 07 corresponding to the second region together form a wrapping layer that wraps downwardly (i.e., the peripheral edge of the wrapping component extends downwardly from the top of the wrapped component along the height direction of its peripheral sidewall to form an enclosing sidewall) the second region 031 of the phase-change material layer 03 away from the optical waveguide layer 02. In other words, the phase-change material layer 03 is wrapped in the closed cavity 001 formed by the first protective layer 05, the second protective layer 07, the first isolation layer 04, and the second isolation layer 06.

[0044] In some embodiments, a stop layer (e.g., a second stop layer having a first thickness H1 and a first width L1, where L1 is greater than the width L0 of the optical waveguide layer 02) and an oxide layer (e.g., a second oxide layer having a second thickness H2) may be pre-determined on the optical waveguide layer 02, as shown in FIG3b and FIG3g. To dispose the phase-change material layer 03 on the optical waveguide layer 02, the oxide layer and the stop layer pre-covering the optical waveguide layer 02 may be etched using a regional etching method to form a cavity with a top opening (or an open window), thereby preparing for the subsequent encapsulation of the phase-change material layer 03. For example, a regional etching method is used to create a window, and a stop layer of fourth thickness H4 is retained directly above the optical waveguide layer 02, thereby forming a first stop layer between the bottom of the cavity or window and the optical waveguide layer 02. Simultaneously, a second stop layer of first thickness H1 remains around the first stop layer. That is, after the phase change material is subsequently sputtered or deposited within the cavity or window, the first stop layer becomes the first isolation layer 04 between the phase change material layer 03 and the optical waveguide layer 02. Specifically, by setting the etching parameters of the regional etching method, a stop layer of fourth thickness H4 (e.g., 1 nm to 100 nm) is retained on the optical waveguide layer 02, thereby forming the first isolation layer 04. This prevents damage to the optical waveguide layer 02 during the etching process or the window creation process, as shown in Figures 1b, 3c, and 3h. For another example, as previously described, during the fabrication of an optical waveguide, an isolation layer of a predetermined desired thickness, such as a fourth thickness H4, may be pre-determined directly on the optical waveguide layer 02. Consequently, when a regional etching method is used to create a window, a stop layer having a thickness less than the fourth thickness H4 is retained directly above the optical waveguide layer 02, thereby forming a first stop layer between the bottom of the cavity or window and the optical waveguide layer 02. Simultaneously, a second stop layer having a fourth thickness H4 remains around this first stop layer. In other words, when a phase change material is subsequently sputtered or deposited within the cavity or window, this first stop layer serves as the first isolation layer 04 between the phase change material layer 03 and the optical waveguide layer 02. Specifically, by setting the etching parameters of the regional etching method, a stop layer having a thickness less than the fourth thickness H4 (e.g., 1 nm to 100 nm) remains on the optical waveguide layer 02, thereby forming the first isolation layer 04. This prevents damage to the optical waveguide layer 02 during the etching process or the window creation process, as shown in Figures 1b, 3c, and 3h. That is, in other embodiments, in the optical waveguide structure having the aforementioned closed cavity 001 , the thickness of the first isolation layer 04 located between the phase change material layer 03 and the optical waveguide layer 02 is less than the fourth thickness H4 .

[0045] In some embodiments, after the above-mentioned cavity is opened on the oxide layer and the stop layer by a regional etching method, a phase change material layer 03 of a specified thickness H0 (for example, 1nm to 1um) can be provided on the first isolation 04 layer by a process such as sputtering or deposition (physical vapor deposition or chemical vapor deposition), thereby obtaining a modulation layer. Of course, in order to protect the modulation layer, it is also necessary to cover it with a first protective layer 05 of a sixth thickness H6, for example, a first oxide layer. In order to ensure stability and avoid the situation where the first oxide layer covering the phase change material layer 03 is too thin and the change area of ​​the phase change material after modulation cannot be controlled, preferably, the sixth thickness H6 of the first oxide layer is 0.1um to 3um. More preferably, the first oxide layer is deposited on the phase change material layer by a physical vapor deposition (PVD) or chemical vapor deposition (CVD) method.

[0046] Since the first isolation layer 04 is obtained by regional etching on the original oxide layer and the stop layer, and the phase change material is sputtered or deposited on the first isolation layer 04, when the first protective layer 05 of the sixth thickness H6 is covered on the phase change material layer, the first protective layer 05 (i.e., the first oxide layer re-covered on the phase change material layer 03) and the second protective layer 07 surrounding the first protective layer 05 (i.e., the portion of the oxide layer retained after the original oxide layer is etched, such as the original second oxide layer) enclose a first groove 0011 with an opening facing the phase change material layer 03; and the first isolation layer 0 4 and the second isolation layer 06 surrounding the first isolation layer 04 (i.e., the portion of the stop layer retained after the original stop layer is etched) enclose a second groove 0012 with an opening facing the phase change material layer 03, and the opening of the first groove 0011 and the opening of the second groove 0012 are arranged relative to each other, so that the first groove 0011 and the second groove 0012 enclose a sealed cavity 001 as described above (i.e., the sum of the height h1 of the notch of the first groove 0011 and the height h2 of the notch of the second groove 0012 is the height of the sealed cavity 001, which is equal to or slightly greater than the thickness H0 of the phase change material layer). Preferably, the cross-sections of the first groove 0011 and the second groove 0012 are both rectangular, that is, the cross-section of the sealed cavity 001 is rectangular. In some embodiments, the upper surface of the first protective layer 05 is flush with the upper surface of the second protective layer 07. Of course, in other embodiments, the upper surface of the first protective layer 05 is not flush with the upper surface of the second protective layer 07; alternatively, the first protective layer 05 covers part of the upper surface of the second protective layer 07 (preferably, the second oxide layer portion surrounding the cavity top opening) or the entire upper surface. In some embodiments, the optical waveguide layer is strip-shaped (i.e., its cross-section is rectangular). Of course, the optical waveguide layer can also be a ridge waveguide (i.e., its cross-section is convex). In some embodiments, the aforementioned substrate can also be an SOI substrate, as long as the substrate ensures that the optical waveguide layer has an optical bandgap of at least 1 eV.

[0047] Example 2: In order to better protect and wrap the phase change material layer 03 and reduce the process difficulty, the present invention also provides another exemplary structure of an optical waveguide, which includes the various components in the above-mentioned Example 1. The difference is that the sealed cavity 001 in this exemplary optical waveguide is only formed by the first oxide layer (i.e., the first protective layer 05) located on the top of the phase change material layer 03, the first isolation layer 04 (i.e., the first stop layer) located at the bottom of the phase change material layer 03 (i.e., the modulation layer), and the second stop isolation layer 06 (i.e., the second stop layer) surrounding the phase change material layer 03 and the first isolation layer 04, see Figure 1c and Figure 1d; and the second protective layer 07 surrounds the first protective layer 05, the second isolation layer 06 and the optical waveguide layer 02, forming an almost fully wrapped protection.

[0048] In some embodiments, the cross-section of the second isolation layer 06 surrounding the phase change material layer 03 and the first isolation layer 04 is an inverted L-shape, and the upper surface of the second isolation layer 06 is flush with or slightly higher than the upper surface of the phase change material layer 03.

[0049] In some embodiments, when preparing the optical waveguide of the exemplary structure, a second oxide layer of a second thickness H2 and a second stop layer of a third thickness H3 may be pre-arranged on and around the optical waveguide layer 02, wherein the top of the second stop layer extends with flanks along the width direction of the optical waveguide, so that the cross section of the second stop layer is T-shaped, and the first width L1 of the vertical portion thereof extending along the Z-axis direction is greater than the width L0 of the optical waveguide layer 02; then, the second oxide layer and the second stop layer are etched by a regional etching method to form a cavity with a top opening. Specifically, by setting the regional etching method, The etching parameters are such that a cavity is formed for accommodating the phase change material layer 03, that is, the second groove 0012 formed in the second stop layer (that is, the first isolation layer 04 serves as the bottom of the second groove 0012, and the second isolation layer 06 serves as the sidewall of the second groove 0012) serves as a cavity for accommodating the phase change material layer 03, and the height h2 from the bottom of the groove to the top opening is equal to or slightly greater than the preset thickness H0 of the sealed cavity / modulation layer, so that the periphery and bottom of the modulation layer are both wrapped by the second stop layer, thereby making the prepared optical waveguide more stable and the processing technology less difficult.

[0050] In other embodiments, the second stop layer pre-installed on and around the optical waveguide layer 02 has a concave cross-section. Specifically, the concave shape includes the standard Chinese character "kou" (concave); or a non-standard Chinese character "kou" (concave) that is similar to the concave shape of a Chinese character (for example, with sidewalls having a certain slope, or with sidewall widths varying along the Z-axis, or with top edges of sidewalls extending a certain width along the width of the optical waveguide). Accordingly, the third thickness H3 refers to the height from the top to the bottom of the sidewalls of the second stop layer having a concave cross-section; and the thickness of the groove bottom is greater than or equal to the fourth thickness.

[0051] As previously mentioned, when preparing an optical waveguide, an isolation layer having a predetermined desired thickness, i.e., a fourth thickness H4, may also be pre-deposited directly on the optical waveguide layer 02. For example, a second stop layer having a fourth thickness H4 may be deposited on the optical waveguide layer 02, rather than a second stop layer having a third thickness H3. Furthermore, during the windowing process, the oxide layer and the second oxide layer may be over-etched, thereby leaving a second stop layer having a thickness less than the fourth thickness H4 on the optical waveguide layer 02, thereby obtaining a first isolation layer 04 having a thickness less than the fourth thickness H4. In other words, in other embodiments, when preparing an optical waveguide having the aforementioned structure, the thickness of the first isolation layer 04 located between the phase change material layer 03 and the optical waveguide layer 02 is less than the fourth thickness H4.

[0052] Example 3: The optical waveguide of the above structure has strict requirements on the size of the window in the window opening process, and because the side walls of the cavity obtained by etching extend in the vertical direction (or are slightly inclined), when sputtering the phase change material, it may be deposited in other peripheral locations. It is necessary to additionally remove this part of the phase change material or cover the phase change material deposited in the peripheral locations with the same first protective layer, which not only makes the window opening process more difficult but also more complicated to operate. Based on this, this article also provides an optical waveguide of another exemplary structure, which includes the various components of the above embodiment 1, except that in this example, the phase change material layer 03 is enclosed in a closed cavity 001 with a trumpet-shaped or bowl-shaped cross-section formed by the first protective layer 05, the second protective layer 07, the first isolation layer 04 and the second isolation layer 06.

[0053] In some embodiments, referring to FIG. 1e and FIG. 1f , the first protective layer 05 and the second protective layer 06 surrounding the first protective layer 05 and the second region of the phase-change material layer 03 away from the optical waveguide layer 02 together form a first groove 0011 having an inverted U-shaped cross section; the first isolation layer 04 and the second isolation layer 06 surrounding the first isolation layer 04 and the first region of the phase-change material layer 03 close to the optical waveguide layer 02 together form a second groove 0012 having a U-shaped cross section. In the same cross section, the spacing between the opposite sidewalls of the first groove 0011 gradually decreases in a direction approaching the optical waveguide layer 02 (or in a vertically downward direction), while the spacing between the opposite sidewalls of the second groove 0012 gradually increases in a direction away from the optical waveguide layer 02 (or in a vertically upward direction). The opening of the first groove 0011 and the opening of the second groove 0012 are arranged opposite to each other, so that the sidewalls of the first groove 0011 and the sidewalls of the second groove 0012 are smoothly connected, thereby enclosing a closed cavity 001.

[0054] In some embodiments, as described above, a stop layer and an oxide layer may be pre-deposited on the optical waveguide layer 02, and then a regional etching method may be used to form a bowl-shaped or horn-shaped cavity with a top opening. On the one hand, the larger top opening of the cavity expands the coverage area of ​​the subsequent sputtering of the phase-change material. The inclined window sidewalls also make it easier for the phase-change material to enter the window and deposit at the bottom of the window, reducing the difficulty of the sputtering process. On the other hand, due to the larger top opening and the certain inclination or curvature of the surrounding sidewalls, that is, non-vertical etching, the etching process is less difficult than the etching process of the optical waveguide structure in Example 1 or Example 2.

[0055] As previously mentioned, during the fabrication of an optical waveguide, an isolation layer having a predetermined thickness, such as a fourth thickness H4, may also be pre-deposited directly on the optical waveguide layer 02. For example, a second stop layer having a fourth thickness H4 is deposited on the optical waveguide layer 02. Then, during the windowing process, the oxide layer and the second stop layer are over-etched, thereby leaving a second stop layer having a thickness less than H4 on the optical waveguide layer 02, thereby obtaining a first isolation layer 04 having a thickness less than the fourth thickness H4. In other words, in other embodiments, in the aforementioned optical waveguide structure having a closed cavity 001 with a trumpet-shaped or bowl-shaped cross-section, the thickness of the first isolation layer 04 located between the phase change material layer 03 and the optical waveguide layer 02 is less than the fourth thickness H4.

[0056] Example 4: Optical waveguide fabrication method. Referring to FIG. 2a , which is a flow chart of an optical waveguide fabrication method according to an exemplary embodiment of the present invention, the method includes the following steps: S101, integrating an optical waveguide layer 02 on a substrate to form an optical waveguide platform. In some embodiments, step S101 is performed using conventional pulsed laser deposition (PLD) technology, such as the process disclosed in Chinese patent CN1487636A, which will not be described in detail here. Referring to FIG. 3a , taking a strip waveguide as an example, an optical waveguide layer 02 is integrated on a substrate 01 to form an optical chip having an optical waveguide platform. In some embodiments, the substrate is a silicon nitride substrate or an SOI substrate; and the optical waveguide layer 02 has an optical bandgap of at least 1 eV. Preferably, the material of the optical waveguide layer 02 is selected from the group consisting of silicon, silicon nitride, gallium nitride, gallium arsenide, aluminum nitride, magnesium oxide, and diamond (polycrystalline or single crystal).

[0057] S103, forming a second stop layer and a second oxide layer on the outer surface of the optical waveguide layer 02 exposed above the substrate by physical vapor deposition or chemical vapor deposition, wherein the second stop layer is located above the optical waveguide layer 02 and has a width greater than the width of the optical waveguide layer 02. In some embodiments, the outer surface of the optical waveguide layer 02 exposed above the substrate is sequentially covered with a second stop layer and a thicker second oxide layer. The second stop layer serves as an isolation layer above the optical waveguide layer 02 for isolating the dry etching process of the oxide layer. When the oxide layer is dry-etched, the dry etching reaction stops after etching the second stop layer, thereby achieving the effect of etching the second oxide layer without affecting the optical waveguide layer itself; it also forms a wrapping effect on the modulation layer, improving the stability of the modulation layer when switching between the amorphous state and the crystalline state. The thicker second oxide layer serves to protect the waveguide and the metal interconnect layer, and at the same time, it serves to insulate the silicon from the metal interconnect layer and the metal interconnect layer from each other. In some embodiments, the material of the second oxide layer is one of silicon oxide (SiO2), aluminum oxide (Al2O3) or ITO. Preferably, the material of the second oxide layer is silicon oxide (SiO2). The material of the second stop layer is one or more of silicon nitride (Si3N4) and titanium nitride (TiN). Preferably, the material of the second stop layer is silicon nitride (Si3N4). In some embodiments, the second stop layer and the second oxide layer are both formed using a basic coating process, which includes many types, including vacuum evaporation, ion beam sputtering, magnetron sputtering, chemical vapor deposition (CVD), etc. The specific process parameters of this coating process vary to a certain extent in different silicon optical flow factories. It is a relatively common existing technology and will not be described in detail here. It should be noted that when the second oxide layer is deposited, a conventional physical vapor deposition (PVD) or chemical vapor deposition (CVD) process will be used to simultaneously deposit the metal interconnection layer 5 and embed it therein, and the metal interconnection layer 5 and the optical waveguide layer 02 are connected by a through hole.

[0058] 2b and 3b , taking a strip waveguide as an example, a second stop layer having a first thickness H1 and a second oxide layer having a second thickness H2 are sequentially formed on the outer surface of the optical waveguide layer 02 exposed above the substrate 01 (i.e., S1013). To wrap the phase change material layer 03 (e.g., partially wrap or nearly completely wrap), the width of the second stop layer is greater than the width of the optical waveguide layer 02. This allows a subsequent windowing process to form a groove in the second stop layer. The bottom of the groove between the phase change material layer 03 and the optical waveguide layer 02 is the first isolation layer 04, and the groove wall surrounding the first isolation layer 04 is the second isolation layer 06.

[0059] 2c , in other embodiments, in order to ensure that the phase-change material layer 03 is almost entirely enclosed by the second stop layer, for example, the upper surface of the phase-change material layer 03 is almost flush with the upper surface of the second stop layer, thereby leaving the second stop layer around the periphery of the phase-change material layer 03, the outer surface of the optical waveguide layer 02 exposed above the substrate 01 may be first covered with a second oxide layer and a second stop layer having a T-shaped cross-section (i.e., S1023). The width L1 of the vertical portion of the T-shape is greater than the width L0 of the optical waveguide layer 02, thereby ensuring that, in the subsequent etching process, when the second stop layer is etched, portions of the second stop layer remain around and at the bottom of the phase-change material layer 03. The portion between the optical waveguide layer 02 and the phase-change material layer 03 is the first isolation layer 04 (having a thickness of H4). Of course, in other embodiments, the outer surface of the optical waveguide layer 02 exposed above the substrate 01 is first covered with a second oxide layer and a second stop layer having a concave cross-section, and the width of the concave cross-section is greater than the width of the optical waveguide layer 02. This ensures that in the subsequent etching process, when the second stop layer is etched, a portion of the second stop layer can be retained around and at the bottom of the phase change material layer 03. The portion located between the optical waveguide layer 02 and the phase change material layer 03 is the first isolation layer 04 (whose thickness is H4).

[0060] As previously described, a first isolation layer 04 having a predetermined fourth thickness H4 can be pre-determined and directly disposed on the optical waveguide layer 02. Therefore, in other embodiments, in step S103, a second stop layer having a fourth thickness H4 (i.e., 1 nm to 100 nm) and a second oxide layer having a second thickness H2 can be sequentially formed on the outer surface of the optical waveguide layer 02 exposed above the substrate 01. A recess can then be formed in the second stop layer through a windowing process. The bottom of the recess between the phase-change material layer 03 and the optical waveguide layer 02 serves as the first isolation layer 04, while the recess walls surrounding the first isolation layer 04 serve as the second isolation layer 06.

[0061] S105: A windowing process is performed on the second stop layer and the second oxide layer using a regional etching method, so that a layer of the second stop layer remains on the optical waveguide layer 02. In some embodiments, the windowing process is performed on the second stop layer and the second oxide layer using a regional etching method to expose a portion of the second stop layer covering the optical waveguide layer 02. Currently, conventional regional etching windowing processes are a combination of dry etching and wet etching or dry etching and dry etching. When dry etching is performed, the second oxide layer in the portion to be windowed is etched until the second stop layer is reached. Dry etching or wet etching is then performed to extend the second stop layer in the portion to be windowed to above the optical waveguide layer. The specific parameters vary among different silicon optical flow factories, but are mainly determined by the oxide layer process, stop layer process, dry etching process, and wet etching process. This is also a relatively common existing technology and will not be described in detail here. In some embodiments, it is important to note that in S105, the regional etching windowing process must avoid the metal interconnect layer 5 and the vias. This means that the metal interconnect layer 5 and the vias must not be exposed in the windowing process, and the metal interconnect layer and the vias must be a certain distance from the area being etched by the windowing process. The specific distance is determined by the process capabilities of different silicon optical flow factories. As previously mentioned, due to the limitations of existing industrial etching processes, it is difficult to directly and perfectly open the windowing process above the optical waveguide layer 02. Specifically, without causing any damage to the optical waveguide layer 02, no excess stop layer and / or oxide layer remains on the optical waveguide layer 02. Therefore, in this method, in step S103, a second stop layer of a first thickness H1 or a third thickness H3 and a second oxide layer of a second thickness H2 are pre-formed on the optical waveguide layer 02. A window is then formed in the second oxide layer and the second stop layer through a regional etching windowing process, while the second stop layer of a fourth thickness H4 is retained on the optical waveguide layer 02. That is, in the windowing area, the second stop layer on the optical waveguide layer 02 is not completely etched away, but a groove is etched in the second stop layer (see S1015 in FIG. 2 b or S1025 in FIG. 2 c).

[0062] On the other hand, as mentioned above, considering the influence of the stop layer on the evanescent field range of the phase change material layer 03 on the light in the optical waveguide layer 02 , preferably, the fourth thickness H4 of the first isolation layer 04 is formed to be 1 nm to 100 nm.

[0063] As previously described, since a second stop layer having a predetermined thickness, i.e., a fourth thickness H4, is pre-deposited on the optical waveguide layer 02, the second oxide layer can be directly etched away during the windowing process. Etching can be stopped when the second stop layer is visible, thereby leaving the second stop layer having the fourth thickness H4, i.e., the first isolation layer 04, on the optical waveguide layer 02. Of course, over-etching can also be performed, leaving the second stop layer having a thickness less than the fourth thickness H4 on the optical waveguide layer 02, i.e., the thickness of the first isolation layer 04 is less than the fourth thickness H4.

[0064] In some embodiments, the area of ​​the second stop layer exposed during the window opening process (ie, the area of ​​the first isolation layer 04 ) is determined by the area of ​​the phase change material to be deposited. Preferably, the area of ​​the exposed second stop layer is the same as the area of ​​the phase change material layer 03 .

[0065] Referring to FIG. 3 c , taking a strip waveguide as an example, a window opening process is performed on the second stop layer and the second oxide layer by a regional etching method, exposing a portion of the second stop layer having a fourth thickness H4 (H4

[0066] To ensure that the area of ​​the exposed portion of the second stop layer, i.e., the first isolation layer 04, is the same as, or not significantly different from, the area of ​​the phase-change material layer 03, the etching process requires very precise control parameters, which in turn makes the process more difficult and places high demands on the subsequent sputtering process. Therefore, during etching in steps S105 or S1015, the window is not opened according to the aforementioned 1:1 (or near 1:1) area ratio. Instead, a bowl-shaped or trumpet-shaped cavity (or window) is etched, and then the phase-change material is sputtered within it. Finally, a first oxide layer of a sixth thickness H6 is deposited to form the first protective layer 05, thereby obtaining the optical waveguide structure shown in FIG1e.

[0067] S107, using a first thin film deposition process to deposit a phase change material onto the surface of the second stop layer exposed in the window by physical vapor deposition, forming a phase change material thin film. In some embodiments, a first sputtering process is used to sputter the phase change material onto the upper surface of the second stop layer exposed in the window, forming a phase change material thin film (i.e., phase change material layer 03). In some embodiments, the phase change material can be formed from or contain a chalcogenide containing antimony or selenium, such as antimony selenide (Sb2Se3 or SbSe), antimony sulfide (Sb2S3 or SbS), or Ge2Sb2Se4Te (GSST). Alternatively, the phase change material can include or be composed of a compound or alloy of a combination of elements selected from GeSbTe, VOx; NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb. Of course, the phase change material may also include a mixture of the above compounds, or the phase change material may be a supercrystal. In some embodiments, the first thin film deposition process is a magnetron sputtering process, and its specific process is as follows: after the optical chip in step S105 is placed in the vacuum chamber, the vacuum chamber is evacuated to a vacuum of 1×10 -6 ​After the vacuum reaches 3.5×10 Torr, argon is introduced and the vacuum is continued to be maintained to keep the process vacuum below 3.5×10 -3 Torr; turn on the magnetron sputtering RF power supply, control the power at 10W-100W, and control the formed phase change material film to be between 1nm and 1μm.

[0068] Referring to FIG3d , taking a strip waveguide as an example, a phase change material is directly sputtered within the cavity to obtain a phase change material layer 03 having a thickness of 1 nm to 1 μm. In some embodiments, a phase change material layer 03 having a predetermined thickness H0 is deposited within the window, such that the sum of the predetermined thickness H0 and a fourth thickness H4 is greater than the first thickness H1. This allows the groove etched in the second stop layer to wrap around the bottom of the modulation layer and the first region 032 near the optical waveguide layer 02 (see S1017 in FIG2b , as well as FIG1a , FIG1b , FIG1e , and FIG1f ). This means that the etched second stop layer forms a wrapping layer that partially wraps around the modulation layer.

[0069] In other embodiments, a phase change material layer 03 with a preset thickness H0 is deposited in the window, so that the preset thickness H0 is less than or equal to the difference between the third thickness H3 and the fourth thickness H4, so that the groove etched on the second stop layer wraps the bottom of the modulation layer and all its side walls (see S1027 in Figure 2c, and Figure 1c and Figure 1d), that is, the second stop layer after etching forms a wrapping layer that almost completely wraps the modulation layer (except for the top surface of the modulation layer).

[0070] In other embodiments, as described above, due to over-etching performed on the second stop layer having a thickness of H4 through a windowing process, a phase change material layer 03 having a predetermined thickness of H0 is deposited within the window. When the sum of the predetermined thickness H0 and the thickness of the first isolation layer is greater than the fourth thickness H4, the groove etched in the second stop layer wraps around the bottom of the modulation layer and the first region 032 adjacent to the optical waveguide layer 02 (see S1017 in FIG. 2b , and FIG. 1a , FIG. 1b , FIG. 1e , and FIG. 1f ). In other words, the etched second stop layer forms a wrapping layer that partially wraps around the modulation layer. Alternatively, if the predetermined thickness H0 is less than or equal to the difference between the fourth thickness H4 and the thickness of the first isolation layer, the groove etched in the second stop layer wraps around the bottom of the modulation layer and all of its sidewalls (see S1027 in FIG. 2c , and FIG. 1c and FIG. 1d ). In other words, the etched second stop layer forms a wrapping layer that substantially completely wraps around the modulation layer (except for the top surface of the modulation layer).

[0071] S109, using a second thin film deposition process to deposit an oxide layer of the same material as in step S103 onto the phase change material layer 03 to achieve coverage, thereby achieving heterogeneous integration of the phase change material and the optical waveguide platform, thereby obtaining an optical waveguide. In some embodiments, the second thin film deposition process deposits an oxide layer of the same material as in step S103 onto the phase change material layer 03 to achieve coverage, thereby achieving heterogeneous integration of the phase change material and the optical waveguide platform, thereby obtaining an exemplary optical waveguide of the present invention. Preferably, the second thin film deposition process is a physical vapor deposition (PVD) or chemical vapor deposition (CVD) process. In some embodiments, the specific process of depositing an oxide layer on the phase change material layer 03 using physical vapor deposition (PVD) includes: after placing the optical chip that has passed step S107 into a vacuum chamber, starting to evacuate the vacuum chamber to a vacuum of 1×10 -6 After the vacuum reaches 3.5×10 Torr, argon is introduced and the vacuum is continued to be maintained to keep the process vacuum below 3.5×10 -3 Torr, turn on the magnetron sputtering RF power supply, control the power at 10W-200W, and control the thickness of the formed oxide layer film to be between 0.1μm and 3μm.

[0072] In other embodiments, the specific process of depositing an oxide layer on the phase change material layer by chemical vapor deposition (CVD) includes: placing the optical chip after step S107 into a vacuum chamber, and then evacuating the vacuum chamber to a vacuum of 1×10 -6 After achieving a vacuum of 0.1 to 1.5 Torr, the substrate is heated to 150°C-350°C. N2, SiH4, and N2O gases are introduced, maintaining the deposition pressure at 0.2 Torr-2.0 Torr. The RF power is then turned on, controlled at 20W-150W, and the thickness of the formed oxide film is controlled to be between 0.1μm and 3μm. Referring to Figure 3e, using a strip waveguide as an example, a second thin-film deposition process is used to deposit an oxide layer made of the same material as in step S103 onto the phase-change material layer O3, resulting in a first protective layer O5 with a thickness of H6, thereby achieving heterogeneous integration of the phase-change material and the optical waveguide platform.

[0073] Example 5: Stability Test. Typically, a voltage pulse can be used to cause the phase-change material layer 03 on a waveguide to undergo a reversible phase transition between a crystalline state and an amorphous state. When the phase-change material layer 03 is in the crystalline state, the optical power passing through the waveguide is low, while when the phase-change material layer 03 is in the amorphous state, the optical power passing through the optical waveguide is high. Therefore, the optical power passing through the optical waveguide containing the phase-change material can be used to indicate the stability of the phase-change material layer.

[0074] The following examples use an optical waveguide fabricated using conventional methods for integrating phase-change materials as a control group, and the optical waveguide of Example 1 described above as an experimental group. The phase-change material layers in the control and experimental groups undergo cyclic modulation of melting and crystallization, and the optical power of the two groups during cyclic modulation is measured, yielding respective cyclic modulation optical power diagrams (see Figures 4 (control group) and 5 (experimental group). Specifically, during the cyclic modulation process, the phase-change material layer 03 in both groups of optical waveguides was composed of the same material and had the same thickness (30 nm), with the same modulator modulation parameters. The pulse voltage for melting (transforming from crystalline to amorphous) the phase-change material layer 03 was 9 V, with a duration of 200 ns; the pulse voltage for crystallization (transforming from amorphous to crystalline) was 3 V, with a duration of 1 μs.

[0075] Control group: Referring to FIG4 , under the existing method for integrating phase change materials, the phase change material layer 03 integrated on the optical waveguide is subjected to cyclic modulation of melting and crystallization. After the phase change material layer 03 re-melts or re-crystallizes, the optical power cannot be maintained at the same level, and its optical power fluctuates greatly during the cyclic modulation process (i.e., during the cyclic modulation process, the optical powers in the two states deviate from their respective mean lines: the optical power mean line S1 in the crystalline state and the optical power mean line S2 in the amorphous state are farther away). This indicates that the properties of the phase change material itself have changed during the modulation process, resulting in the inability to stably modulate the state of the phase change material.

[0076] Experimental group: Referring to FIG5 , during the melting-crystallization cyclic modulation process of the phase change material layer 03 in the optical waveguide shown in Example 1, the optical power remains at the same level after re-melting or re-crystallization, and the optical power fluctuation is very small during the cyclic modulation process (i.e., during the cyclic modulation process, the optical powers in the two states almost coincide with their respective mean lines: the optical power mean line S3 in the crystalline state and the optical power mean line S4 in the amorphous state, or the deviation is very small). This indicates that the phase change material is stable during the cyclic modulation process and that the state of the phase change material can be stably modulated under the existing structure.

[0077] The L-shape, T-shape, concave shape, etc. described in this article using text (such as Chinese or English, etc.) shape description words include the shape of the text in various font forms, and also include structures with non-standard text shapes. For example, the top of the L-shape can have a protruding short side extending laterally (shorter than the bottom), and its general structure only needs to look like the corresponding text shape. Similarly, the various structures described in this article using geometric shapes include standard geometric shapes and non-standard geometric shapes (or similar or close shapes). For example, the rectangle in this article includes a standard rectangle in geometric shapes, and can also be a non-standard approximate rectangle. For example, due to process limitations and other factors, the side wall of the sealed cavity formed by the docking of the first groove and the second groove side wall has a slight tilt, or there is a slight deviation when the first groove and the second groove side wall are docked, but the overall structure is still close to a rectangle.

[0078] It should be noted that, in this document, the terms "comprises," "includes," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus comprising a series of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not exclude the presence of other identical elements in the process, method, article, or apparatus comprising the element.

[0079] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation methods. The above-mentioned specific implementation methods are merely illustrative and not restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are protected by the present invention.

Claims

1. An optical waveguide, characterized in that, Comprising: An optical waveguide layer, a modulation layer located on the optical waveguide layer, a first isolation layer disposed between the optical waveguide layer and the modulation layer, and a first protective layer covering the modulation layer. Further comprising: a second isolation layer surrounding the first isolation layer and the modulation layer and having an inverted L-shaped cross section, and a second protective layer surrounding the first protective layer, the second isolation layer, and the optical waveguide layer; wherein, the modulation layer is enclosed in a sealed cavity formed by enclosing the first protective layer, the first isolation layer, and the second isolation layer, and the modulation layer is a phase change material layer or the modulation layer includes a phase change material layer.

2. The optical waveguide according to claim 1, wherein The first isolation layer and the second isolation layer enclose a second groove with an opening facing the first protective layer, and the height from the bottom of the inner groove of the second groove to the top opening is greater than or equal to the thickness of the modulation layer.

3. The optical waveguide according to claim 2, wherein The second groove is formed by etching the second isolation layer with a cross section in a T shape or a concave shape pre-covered on the optical waveguide layer and the second protective layer covering the optical waveguide layer and the second isolation layer by a regional etching method.

4. The optical waveguide according to any one of claims 1 to 3, characterized in that The phase change material layer is obtained by sputtering a phase change material on the first isolation layer; and / or, the first protective layer is deposited on the phase change material layer by a physical vapor deposition or chemical vapor deposition process.

5. The optical waveguide according to any one of claims 1 to 3, characterized in that, The upper surface of the first protective layer is flush with the upper surface of the second protective layer.

6. The optical waveguide according to any one of claims 1 to 3, characterized in that, The thickness of the first isolation layer is 1 nm to 100 nm; and / or, the length of the first isolation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm; and / or, the thickness of the first protective layer is 0.1 μm to 3 μm; and / or, the thickness of the modulation layer is 1 nm to 1 μm; and / or, the length of the modulation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm.

7. The optical waveguide according to any one of claims 1 to 3, characterized in that, The phase change material layer is made of a superlattice material; or, the phase change material layer is formed by a chalcogenide containing antimony or selenium; or, the phase change material layer contains a chalcogenide, wherein the chalcogenide includes Sb2Se3 or SbSe, Sb2S3 or SbS, Ge2Sb2Se4Te; or, the phase change material of the phase change material layer includes a compound or alloy or a mixture of the compound of an element combination containing germanium, antimony, selenium, and vanadium oxide; the compounds include: NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

8. The optical waveguide according to any one of claims 1 to 3, characterized in that, The optical waveguide includes a metal interconnection layer embedded in the second protective layer; and / or, the cross section of the optical waveguide layer is rectangular or convex-shaped.

9. The optical waveguide according to any one of claims 1 to 3, characterized in that The first protective layer is made of any one or more of SiO2, Al2O3, and ITO; and / or, the second protective layer is made of any one or more of SiO2, Al2O3, and ITO; and / or, the first isolation layer is made of one or both of Si3N4 and TiN; and / or, the second isolation layer is made of one or both of Si3N4 and TiN.

10. A method for preparing the optical waveguide according to any one of claims 1 to 9, characterized in that, Including the steps: S1021, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1023, forming a second stop layer with a third thickness and a second oxide layer with a second thickness on the outer surface of the optical waveguide layer exposed above the substrate through physical vapor deposition or chemical vapor deposition; wherein, the second stop layer is located above the optical waveguide layer, and its cross-section is in a T shape or a concave shape, and the width of the vertical part of the second stop layer in the T shape is greater than the width of the optical waveguide layer, or the width of the second stop layer in the concave shape is greater than the width of the optical waveguide layer; S1025, performing a window opening process on the second stop layer and the second oxide layer by a regional etching method, so that the second stop layer forms a first isolation layer with a fourth thickness on the optical waveguide layer, and a second isolation layer with an inverted L-shaped cross-section surrounding the first isolation layer; wherein, the fourth thickness is less than the third thickness; S1027, using a first thin film deposition process to deposit a phase change material onto the surface of the first isolation layer by physical vapor deposition to form a phase change material layer with a preset thickness within the window formed by the first isolation layer and the second isolation layer surrounding it; the preset thickness is less than or equal to the difference between the third thickness and the fourth thickness; S1029, using a second thin film deposition process to deposit an oxide layer of the same material as in step S1013 onto the phase change material layer to achieve coverage, obtaining a first protective layer with a sixth thickness.

11. An optical waveguide, characterized in that, Including: An optical waveguide layer, a modulation layer located on the optical waveguide layer, a first isolation layer is provided between the optical waveguide layer and the modulation layer, and a first protective layer covers the modulation layer. It further includes: a second isolation layer surrounding the first isolation layer and the first region of the modulation layer close to the first isolation layer, and a second protective layer surrounding the first protective layer, the second region of the modulation layer close to the first protective layer, the second isolation layer, and the optical waveguide layer; wherein, the modulation layer is wrapped in a sealed cavity formed by enclosing the first protective layer, the second protective layer, the first isolation layer, and the second isolation layer, and the modulation layer includes a phase change material layer or the modulation layer is a phase change material layer.

12. The optical waveguide according to claim 11, characterized in that, The first protective layer and the second protective layer surrounding the second region of the first protective layer and the modulation layer enclose a first groove with an inverted concave cross-section; the first isolation layer and the second isolation layer surrounding the first region of the first isolation layer and the modulation layer enclose a second groove with a concave cross-section, and the openings of the first groove and the second groove are arranged opposite to each other, so that the first groove and the second groove enclose the sealed cavity with a rectangular cross-section.

13. The optical waveguide according to claim 11, characterized in that, The first protective layer and the second protective layer surrounding the second region of the first protective layer and the modulation layer enclose a first groove with an inverted U-shaped cross-section; the first isolation layer and the second isolation layer surrounding the first region of the first isolation layer and the modulation layer enclose a second groove with a U-shaped cross-section, and in the same cross-section, the distance between the opposite side walls of the first groove gradually decreases along the direction close to the optical waveguide layer, while the distance between the opposite side walls of the second groove gradually increases along the direction away from the optical waveguide layer, and the openings of the first groove and the second groove are arranged opposite to each other, so that the side walls of the first groove and the side walls of the second groove are smoothly connected and enclose the sealed cavity in a bowl shape or a horn shape.

14. The optical waveguide according to any one of claims 11 to 13, characterized in that, The first isolation layer is the bottom of a cavity with a top opening formed by regionally etching the second protective layer and the second isolation layer pre-coated on the optical waveguide layer; and / or, the phase change material layer is obtained by sputtering a phase change material on the first isolation layer; and / or, the first protective layer is deposited on the modulation layer by physical vapor deposition or chemical vapor deposition process.

15. The optical waveguide according to any one of claims 11 to 13, characterized in that, The upper surface of the first protective layer is flush with the upper surface of the second protective layer.

16. The optical waveguide according to any one of claims 11 to 13, characterized in that The thickness of the first isolation layer is 1 nm to 100 nm; and / or, the length of the first isolation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm; and / or, the thickness of the first protective layer is 0.1 μm to 3 μm; and / or, the thickness of the modulation layer is 1 nm to 1 μm; and / or, the length of the modulation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm.

17. The optical waveguide according to any one of claims 11 to 13, characterized in that, The phase change material layer is made of a superlattice material; alternatively, the phase change material layer is formed of a chalcogenide compound containing antimony or selenium, or the phase change material layer contains the chalcogenide compound, where the chalcogenide compound includes Sb2Se3 or SbSe, Sb2S3 or SbS, Ge2Sb2Se4Te; alternatively, the phase change material of the phase change material layer includes a compound or alloy or a mixture of the compound of an elemental combination containing germanium, antimony, selenium, and vanadium oxide compound; the compound includes: NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

18. The optical waveguide according to any one of claims 11 to 13, characterized in that The optical waveguide includes a metal interconnect layer embedded in the second protective layer; and / or, the cross-section of the optical waveguide layer is rectangular or convex-shaped.

19. The optical waveguide according to any one of claims 11 to 13, characterized in that, The first protective layer is made of any one or more of SiO2, Al2O3, and ITO; and / or, the second protective layer is made of any one or more of SiO2, Al2O3, and ITO; and / or, the first isolation layer is made of one or two of Si3N4 and TiN; and / or, the second isolation layer is made of one or two of Si3N4 and TiN.

20. A method for preparing the optical waveguide according to claim 12, characterized in that, Including steps: S1011, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1013, forming a second stop layer with a first thickness and a second oxide layer with a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition, where the second stop layer is located above the optical waveguide layer, and the width of the second stop layer is greater than the width of the optical waveguide layer; S1015, performing a window opening process on the second stop layer and the second oxide layer by a regional etching method, so that the second stop layer forms a first isolation layer with a fourth thickness on the optical waveguide layer, and the second isolation layer surrounding the first isolation layer, and the fourth thickness is less than the first thickness; S1017, depositing a phase change material onto the surface of the first isolation layer exposed in the window by physical vapor deposition using a first thin film deposition process to form a phase change material layer with a preset thickness; the sum of the preset thickness and the fourth thickness is greater than the first thickness; S1019, depositing an oxide layer of the same material as in step S1013 onto the phase change material layer by a second thin film deposition process to achieve coverage, obtaining a first protective layer with a sixth thickness.

21. A method for preparing an optical waveguide, characterized in that, Including steps: S1021, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1023. Form a second stop layer with a fourth thickness and a second oxide layer with a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition. Among them, the second stop layer is located above the optical waveguide layer, and its cross-section is in a T shape or a concave shape. The width of the vertical part of the T-shaped second stop layer is greater than the width of the optical waveguide layer, or the width of the concave-shaped second stop layer is greater than the width of the optical waveguide layer. Among them, the fourth thickness is 1 nm to 100 nm. S1025. Perform a window opening process on the second stop layer and the second oxide layer by a regional etching method, so that the second stop layer forms a first isolation layer with a thickness less than the fourth thickness on the optical waveguide layer, and a second isolation layer with an inverted L-shaped cross-section surrounding the first isolation layer. S1027. Use a first thin film deposition process to deposit a phase change material on the surface of the first isolation layer by physical vapor deposition method to form a phase change material layer with a preset thickness within the window formed by the first isolation layer and the second isolation layer around it. The preset thickness is less than or equal to the difference between the fourth thickness and the thickness of the first isolation layer. S1029. Use a second thin film deposition process to deposit an oxide layer of the same material as in step S1013 on the phase change material layer to achieve coverage, and obtain a first protective layer with a sixth thickness.

22. A method for preparing an optical waveguide according to claim 21, characterized in that, The fourth thickness H4 is obtained by simulation in advance.

23. A method for preparing an optical waveguide according to claim 21, characterized in that, The length of the first isolation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm.

24. A method for preparing an optical waveguide according to claim 21, characterized in that, The thickness of the phase change material layer is 1 nm to 1 μm; and / or, the length of the phase change material layer extending along the length direction of the optical waveguide is 1 μm to 10 μm.

25. A method for preparing an optical waveguide according to any one of claims 21 to 24, characterized in that, The phase change material layer is made of a superlattice material.

26. A method for preparing an optical waveguide according to any one of claims 21 to 24, characterized in that, The phase change material layer is formed by a chalcogenide containing antimony or selenium, or the phase change material layer contains the chalcogenide. Among them, the chalcogenide includes Sb2Se3 or SbSe, Sb2S3 or SbS, Ge2Sb2Se4Te.

27. A method for preparing an optical waveguide according to any one of claims 21 to 24, characterized in that, The phase change material includes a compound or alloy or a mixture of the compounds containing an element combination of germanium, antimony, selenium, and vanadium oxide. The compounds include NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

28. A method for preparing an optical waveguide according to any one of claims 21 to 24, characterized in that, The second stop layer is made of one or two of Si3N4 and TiN.

29. An optical waveguide prepared by the method for preparing an optical waveguide according to any one of claims 21 to 28, characterized in that, Including: An optical waveguide layer, a modulation layer located on the optical waveguide layer, a first isolation layer disposed between the optical waveguide layer and the modulation layer, and a first protective layer covering the modulation layer. Further included are: a second isolation layer surrounding the first isolation layer and the modulation layer and having an inverted L-shaped cross section, and a second protective layer surrounding the first protective layer, the second isolation layer, and the optical waveguide layer. Wherein, the modulation layer is encapsulated in a sealed cavity formed by enclosing the first protective layer, the first isolation layer, and the second isolation layer, and the modulation layer is a phase change material layer or the modulation layer includes a phase change material layer. Wherein, the thickness of the first isolation layer is less than a fourth thickness, and the fourth thickness is 1 nm to 100 nm.

30. The optical waveguide according to claim 29, characterized in that, The first isolation layer and the second isolation layer enclose a second groove with an opening facing the first protective layer, and the height from the bottom of the inner groove of the second groove to the top opening is greater than or equal to the thickness of the modulation layer.

31. A method for preparing an optical waveguide, characterized in that, Including the steps of: S1011, integrating an optical waveguide layer on a substrate to form an optical waveguide platform; S1013, forming a second stop layer with a fourth thickness and a second oxide layer with a second thickness on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition. Wherein, the second stop layer is located above the optical waveguide layer, and the width of the second stop layer is greater than the width of the optical waveguide layer; the fourth thickness is 1 nm to 100 nm; S1015, performing a window opening process on the second stop layer and the second oxide layer by a regional etching method, so that the second stop layer forms a first isolation layer with a thickness less than the fourth thickness on the optical waveguide layer, and the second isolation layer surrounding the first isolation layer; S1017, depositing a phase change material onto the surface of the first isolation layer exposed in the window by physical vapor deposition using a first thin film deposition process to form a phase change material layer with a preset thickness; the sum of the preset thickness and the thickness of the first isolation layer is greater than the fourth thickness; S1019, depositing an oxide layer of the same material as in step S1013 onto the phase change material layer by a second thin film deposition process to achieve coverage, obtaining a first protective layer with a sixth thickness.

32. A method for preparing an optical waveguide according to claim 31, characterized in that, The length of the first isolation layer extending along the length direction of the optical waveguide is 1 μm to 10 μm.

33. A method for preparing an optical waveguide according to claim 31, characterized in that, The thickness of the phase change material layer is 1 nm to 1 μm; and / or, the length of the phase change material layer extending along the length direction of the optical waveguide is 1 μm to 10 μm.

34. A method for preparing an optical waveguide according to any one of claims 31 to 33, characterized in that, The phase change material layer is made of a superlattice material.

35. A method for preparing an optical waveguide according to any one of claims 31 to 33, characterized in that, The phase change material layer is formed of a chalcogenide compound containing antimony or selenium, or the phase change material layer contains the chalcogenide compound, where the chalcogenide compound includes Sb2Se3 or SbSe, Sb2S3 or SbS, Ge2Sb2Se4Te.

36. A method for preparing an optical waveguide according to any one of claims 31 to 33, characterized in that, The phase change material includes a compound or alloy containing an element combination of germanium, antimony, selenium, and vanadium oxide, or a mixture of the compounds; the compounds include NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

37. A method for preparing an optical waveguide according to any one of claims 31 to 33, characterized in that, The second oxide layer is made of any one or more of SO2, Al2O3, and ITO.

38. A method for preparing an optical waveguide according to any one of claims 31 to 33, characterized in that, The second stop layer is made of one or two of Si3N4 and TiN.

39. An optical waveguide prepared by the method for preparing an optical waveguide according to any one of claims 31 to 38, characterized in that, Comprising: An optical waveguide layer, a modulation layer located on the optical waveguide layer, a first isolation layer is disposed between the optical waveguide layer and the modulation layer, and a first protective layer covers the modulation layer. Further included are: a second isolation layer surrounding the first isolation layer and a first region of the modulation layer close to the first isolation layer, and a second protective layer surrounding the first protective layer, a second region of the modulation layer close to the first protective layer, the second isolation layer, and the optical waveguide layer; wherein, the modulation layer is enclosed in a sealed cavity formed by the first protective layer, the second protective layer, the first isolation layer, and the second isolation layer, and the modulation layer includes a phase change material layer or the modulation layer is a phase change material layer; wherein, the thickness of the first isolation layer is less than a fourth thickness, and the fourth thickness is 1 nm to 100 nm.

40. The optical waveguide according to claim 39, wherein, The first protective layer and the second protective layer surrounding the second region of the first protective layer and the modulation layer enclose a first groove with an inverted concave cross-section; the first isolation layer and the second isolation layer surrounding the first region of the first isolation layer and the modulation layer enclose a second groove with a concave cross-section, and the openings of the first groove and the second groove are oppositely arranged, so that the first groove and the second groove enclose the sealed cavity with a rectangular cross-section; or, The first protective layer and the second protective layer surrounding the second region of the first protective layer and the modulation layer enclose a first groove with an inverted U-shaped cross-section; the first isolation layer and the second isolation layer surrounding the first region of the first isolation layer and the modulation layer enclose a second groove with a U-shaped cross-section. In the same cross-section, the distance between the oppositely arranged side walls of the first groove gradually decreases along the direction close to the waveguide layer, while the distance between the oppositely arranged side walls of the second groove gradually increases along the direction away from the waveguide layer, and the openings of the first groove and the second groove are oppositely arranged, so that the side walls of the first groove and the side walls of the second groove are smoothly connected and enclose the sealed cavity in a bowl shape or a horn shape.

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