An optical waveguide and a method for preparing the same

Abstract

The present invention relates to an optical waveguide and a method for manufacturing the same. The optical waveguide includes 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, and a first protective layer covers the modulation layer. The optical waveguide further includes: 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 encapsulated 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. In the optical waveguide of the present invention, the modulation of light by the modulation layer is more stable. Correspondingly, the present invention also provides a method for manufacturing the foregoing optical waveguide.

Description

Technical Field

[0001] The present invention relates to an optical waveguide, and more particularly to an optical waveguide including a modulation layer and a method for manufacturing the same. Background Art

[0002] In a photonic circuit, light can be controllably guided through an optical waveguide network by various optical switching devices and power splitting devices. Such devices typically operate by controlling the phase of light in the waveguide. For example, by tuning the phase of a Silicon-On-Insulator (SOI) waveguide, a Micro Ring Resonator (MRR) and a Mach-Zehnder Interferometer (MZIs) can achieve optical switching and power splitting functions. Additionally, a directional coupler can transiently couple different amounts of light between closely spaced waveguides by tuning its relative phase. Phase shift mechanisms are typically based on the thermo-optic effect or the free carrier dispersion effect. However, due to the weak perturbation of the refractive index, the waveguide length in such devices is relatively long for achieving the desired phase shift. For example, an MZI can achieve the desired π phase shift at approximately 500 μm. Micro rings are small in size, but their operating bandwidth is limited by the resonance condition. Another approach is to use Micro-Electromechanical System (MEMS) switches in a photonic circuit, where the coupled waveguides 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), an uncompact structure, and relatively high manufacturing cost and complexity. Importantly, the above technologies suffer from instability and short service life, that is, the state of the device for controlling the light phase needs to be maintained at a constant power consumption, and the MEMS has a limited life due to its own mechanical structure.

[0003] Phase-Change Materials (PCMs) are intrinsically 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 be switched back and forth between the amorphous and crystalline states at high speed and with long-term stability. When switching between the amorphous and crystalline states, the refractive index changes sharply. It has been confirmed that a compact optical switch with Ge2Sb2Te5 (GST) and Ge2Sb2Se4Te1 (GSST) on top of a waveguide coupler has a high switching speed (100 ns) and low power consumption. Therefore, PCM-based photonic devices have several advantages over traditional photonic switching schemes and are promising for the development of large-scale non-volatile reprogrammable photonic routing systems, such as field-programmable coupler arrays, etc.

[0004] Based on this, the prior art has proposed an optical waveguide with a PCM. For example, in the Chinese patent application for invention with the application number CN202180043314.8, a phase change material layer with low absorption loss (i.e., the extinction coefficient is basically less than 0.1) in the amorphous state and a large optical coefficient difference between the crystalline state and the amorphous state is provided on the optical waveguide, and this phase change material layer can be switched between at least two stable solid states: the amorphous state and the crystalline state. However, for the existing optical waveguide with a PCM, due to the limitations of its structure, there are instability problems when the PCM switches between the amorphous state and the crystalline state. Summary of the Invention

[0005] The object of the present invention is to provide an optical waveguide and a preparation method thereof, which partially solve or alleviate the above deficiencies in the prior art, and the stability of the modulation layer in the optical waveguide when switching between the amorphous state and the crystalline state is more reliable.

[0006] In order to solve the above-mentioned technical problems, the present invention specifically adopts the following technical solutions:

[0007] In the first aspect of the present invention, there is provided an optical waveguide, which includes: 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, 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 is a phase change material layer or the modulation layer includes a phase change material layer.

[0008] In some embodiments of the present invention, 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.

[0009] In some embodiments of the present invention, 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 opposite sidewalls of the first groove gradually decreases in the direction close to the waveguide layer, while the distance between the opposite sidewalls of the second groove gradually increases in the direction away from the waveguide layer. The openings of the first groove and the second groove are oppositely arranged, so that the sidewalls of the first groove and the sidewalls of the second groove are smoothly connected and enclose the sealed cavity in the shape of a bowl or a horn or a funnel.

[0010] In some embodiments of the present invention, the first isolation layer is the cavity bottom with a top opening formed by etching the second protective layer and the second isolation layer pre-coated on the optical waveguide layer by a regional etching method.

[0011] In some embodiments of the present invention, the phase change material layer is obtained by sputtering a phase change material on the first isolation layer.

[0012] In some embodiments of the present invention, the first protective layer is deposited on the modulation layer by physical vapor deposition or chemical vapor deposition process.

[0013] In some embodiments of the present invention, the upper surface of the first protective layer is flush with the upper surface of the second protective layer.

[0014] In some embodiments of the present invention, the thickness of the first isolation layer is 1 nm to 100 nm.

[0015] In some embodiments of the present invention, the length of the first isolation layer extending along the waveguide length direction is 1 μm to 10 μm.

[0016] In some embodiments of the present invention, the thickness of the first protective layer is 0.1 μm to 3 μm.

[0017] In some embodiments of the present invention, the length of the first isolation layer extending along the waveguide length direction is 1 μm to 10 μm.

[0018] In some embodiments of the present invention, the thickness of the modulation layer is 1 nm to 1 μm; and / or, the length of the modulation layer extending along the waveguide length direction is 1 μm to 10 μm.

[0019] In some embodiments of the present invention, 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, wherein 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 compounds of an elemental combination containing germanium, antimony, selenium, and vanadium oxide compounds; the compounds include; NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

[0020] In some embodiments of the present invention, the optical waveguide layer includes a third region and a fourth region located outside the third region; the modulation layer is located above the fourth region. Herein, the third region refers to the region including the metal interconnect layer and the region including the channels connected to the metal interconnect layer; the fourth region refers to the region not including the metal interconnect layer and the region not including the channels connected to the metal interconnect layer.

[0021] In some embodiments of the present invention, the cross-section of the optical waveguide layer is rectangular or convex-shaped.

[0022] In some embodiments of the present invention, the first protective layer and / or the second protective layer is made of any one or more of SO2, Al2O3, and ITO.

[0023] In some embodiments of the present invention, the first isolation layer and / or the second isolation layer is made of one or two of Si3N4 and TiN.

[0024] In a second aspect of the present invention, there is provided a method for manufacturing the above optical waveguide, which includes the steps:

[0025] S1011, integrating an optical waveguide layer on a substrate to form an optical waveguide platform;

[0026] 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, 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;

[0027] S1015, perform the window opening process for the second stop layer and the second oxide layer through a regional etching method, so as to form a first stop layer with a fourth thickness in the optical waveguide layer, and the second stop layer surrounding the first stop layer, where the fourth thickness is less than the first thickness;

[0028] S1017, use a first thin film deposition process to deposit a phase change material on the surface of the first stop layer exposed in the window by physical vapor deposition method 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;

[0029] S1019, 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 oxide layer with a sixth thickness.

[0030] Advantages of the present invention: Currently, the main method for fabricating integrated optical devices based on phase change materials on a mature and available commercial SOI substrate is as follows: depositing various phase change materials directly on the upper surface of the optical waveguide layer (i.e., using an upward coupling method) through advanced magnetron sputtering or thermal evaporation processes, or depositing on the upper surface and sidewalls of the waveguide (compared with the upward coupling method; when depositing a phase change material layer on the sidewalls of the optical waveguide layer at the same time, there will be an uneven problem, which will lead to many uncertain factors in the subsequent optical coupling and phase change material modulation processes). The sputtering of the phase change material can be achieved by 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 energetic particles to bombard the target surface in a vacuum, so that the bombarded particles are deposited on the substrate. After sputtering a phase change material thin film on the surface using magnetron sputtering technology, then sputtering an oxide layer for protection. Although this method can achieve the heterogeneous integration of the phase change material and the optical waveguide, there are still the following two problems:

[0031] 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 - 30nm), and the oxide layer is sputtered immediately after the phase change material, and only covers the upper surface of the phase change material layer and cannot completely wrap the phase change material, so its protection effect is relatively low. 2. After the phase change material is modulated (melted / recrystallized), especially after melting, it has fluidity and will move a certain distance. Also, because there is only a thin oxide layer on its surface, in fact, it cannot control the change area of the phase change material after modulation, which may lead to material separation or even volatilization problems, and further lead to unstable problems when the modulation layer switches between the amorphous state and the crystalline state.

[0032] On the other hand, it is difficult to achieve commercial implementation (e.g., industrial production) and it can only be used for scientific research. Because in industrial production, the chip generally also includes an oxide layer on the surface of the optical waveguide and a metal interconnect layer embedded in the oxide layer. Limited by the existing front-end and back-end processes, the phase change material cannot be directly added to the chip manufacturing process, that is, the method of directly sputtering the phase change material layer on the waveguide layer cannot be directly applied to industrial production. Specifically, the existing chip manufacturing process mainly includes front-end processes and back-end processes. The front-end processes include wafer processing, oxidation process, lithography, etching, deposition, and doping / ion implantation, etc., and the back-end process is mainly to form the metal interconnect layer on the chip. Due to the many technical difficulties and complex operations in the front-end processes, in order to avoid contamination, the phase change material is not allowed to be integrated on the waveguide in the front-end processes. The dielectric layer and metallization in the back-end processes require a relatively high working temperature, and the stability of the phase change material integration will be affected in this high-temperature environment. Therefore, the phase change material is not allowed to be placed before metallization. That is to say, the industrial production of the optical waveguide with this structure is more difficult.

[0033] Based on this, the present invention provides an optical waveguide with a new structure, which has higher structural stability and is conducive to commercial implementation. Specifically, in order to avoid damage to the optical waveguide layer during the window opening process, therefore, a first isolation layer is provided between the optical waveguide layer and the modulation layer, and the modulation layer is disposed in a cavity formed by enclosing the first isolation layer and the second isolation layer and covered by the first protective layer, that is, the movement space of the modulation layer during the switching process between different states (i.e., amorphous state and crystalline state) is defined by the first isolation layer, the second isolation layer, the first protective layer, and the second protective layer (for example, the second grooves formed by the first isolation layer and the second isolation layer respectively semi-wrap the part of the modulation layer close to the optical waveguide layer, and at the same time, the first grooves formed by the first protective layer and the second protective layer semi-wrap the other part of the modulation layer far from the optical waveguide layer, and due to the tightness between the second isolation layer and the second protective layer and the tightness between the first protective layer and the second protective layer during the deposition process, the movement space of the modulation layer during the switching process between different states is defined), thereby ensuring the integrity and stability of the modulation layer, further reducing the irreversible damage to the phase change material, and prolonging the service life of the modulation layer.

[0034] Further, a bowl-shaped or horn-shaped sealed cavity with a larger upper cross-section and a smaller lower cross-section is formed by enclosing the modulation layer with the first isolation layer, the second isolation layer, the first protection layer, and the second protection layer. On the one hand, in the window opening process, the top opening of the formed window is larger, expanding the sputtering coverage area of the subsequent sputtered phase change material. The inclined window sidewalls also enable the phase change material to more easily 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 inclined or curved sidewalls around, that is, non-vertical etching, the difficulty is lower compared to vertical etching. Brief Description of the Drawings

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn to scale. Obviously, the following-described drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0036] Figure 1a Cross-sectional structure schematic diagram of an optical waveguide according to an exemplary embodiment of the present invention;

[0037] Figure 1b is Figure 1a exploded view of the optical waveguide shown;

[0038] Figure 1c Cross-sectional structure schematic diagram of an optical waveguide according to another exemplary embodiment of the present invention;

[0039] Figure 1d is Figure 1c exploded view of the optical waveguide shown;

[0040] Figure 1e Cross-sectional structure schematic diagram of an optical waveguide according to still another exemplary embodiment of the present invention;

[0041] Figure 1f is Figure 1e exploded view of the optical waveguide shown;

[0042] Figure 2a Flowchart of a method for manufacturing an optical waveguide according to an exemplary embodiment of the present invention;

[0043] Figure 2b is for manufacturing an optical waveguide with the structure shown Figure 1a using the method for manufacturing an optical waveguide of the present invention;

[0044] Figure 2cFlow chart for preparing an optical waveguide with the structure shown in Figure 1c the following using the method for preparing an optical waveguide of the present invention;

[0045] Figures 3a to 3e Schematic diagram for preparing an optical waveguide taking the strip waveguide layer as an example according to the method shown in Figure 2;

[0046] Figures 3f to 3j Schematic diagram for preparing an optical waveguide taking the strip waveguide layer as an example according to the method shown in Figure 2;

[0047] Figure 4 Optical power diagram for cyclic modulation of an optical waveguide prepared by using an existing integrated phase change material method (i.e., the control group);

[0048] Figure 5 For Figures 3a to 3e the optical power diagram for cyclic modulation of an optical waveguide obtained by using the method shown in

[0049] Summary of reference numeral identification: 01 substrate; 02 optical waveguide layer; 03 phase change material layer; 04 first stop layer; 05 first oxide layer; 06 second stop layer; 07 second oxide layer; 5 metal interconnection layer; 001 sealing cavity, 0011 first groove, 0012 second groove; H0 height (or called preset thickness) of the phase change material layer extending along the Z-axis direction; H1, H3 heights (or called first thickness, third thickness) of the second stop layer extending along the Z-axis direction in different embodiments; H2 height (or called second thickness) of the second oxide layer extending along the Z-axis direction in different embodiments; H4 height (or called fourth thickness) of the first stop layer extending along the Z-axis direction; H6 height (or called sixth thickness) of the first oxide layer extending along the Z-axis direction; h1 height of the notch of the first groove; h2 height of the notch of the second groove (h2 > h1). Detailed implementation manners

[0050] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0051] In this article, suffixes such as "module", "component" or "unit" used to represent elements are only for the convenience of describing the present invention and have no specific meaning in themselves. Therefore, "module", "component" or "unit" can be used interchangeably.

[0052] In this document, terms such as "upper", "lower", "inner", "outer", "front", "rear", "one end", "the other end", etc. indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0053] In this document, unless otherwise clearly specified and defined, terms such as "installed", "provided with", "connected", etc. should be understood in a broad sense. For example, "connected" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection, a direct connection, or an indirect connection through an intermediate medium, and can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0054] As used in this document, "and / or" includes any and all combinations of one or more of the listed related items. As used in this document, "a plurality" means two or more, that is, it includes two, three, four, five, etc.

[0055] As used in this specification, the term "about" typically represents + / -5% of the stated value, more typically + / -4% of the stated value, more typically + / -3% of the stated value, more typically + / -2% of the stated value, even more typically + / -1% of the stated value, and even more typically + / -0.5% of the stated value.

[0056] In this specification, certain embodiments may be disclosed in a format within a certain range. It should be understood that this description of "within a certain range" is only for convenience and brevity and should not be construed as a rigid limitation on the disclosed range. Therefore, the description of the range should be considered to have specifically disclosed all possible sub-ranges and the individual numerical values within this range. For example, the description of the range 1 to 6 should be considered to have specifically disclosed sub-ranges 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., and the individual numbers within this range, such as 1, 2, 3, 4, 5, and 6. The above rules apply regardless of the breadth of the range.

[0057] As used in this document, "light" refers to electromagnetic radiation or electromagnetic waves within the range from ultraviolet (UV) to infrared (IR) (for example, between 10 nm and 100 μm), which can propagate in free space and be guided by waveguides.

[0058] In this text, "steady state" may mean being substantially stable under the standard temperature and pressure conditions specified by the National Institute of Standards and Technology (NIST).

[0059] In this text, "optical waveguide layer" refers to any structure that confines light within or adjacent to its surface in one or more dimensions, thereby guiding light in a propagation direction parallel to its axis. The waveguide is formed by a series of layers / regions with different refractive indices, usually including an inner layer / region or a core layer / region. The inner layer / region or core layer / region is made of a material with a higher refractive index compared to the surrounding (outer) layer / region or cladding layer / region. In this case, the waveguide confines light in two dimensions in the thickness / growth direction and the transverse / width direction perpendicular to the thickness / growth direction, for example, within a channel. The core layer / region and / or the cladding layer / region can be referred to as the guiding layer that actively confines and guides light.

[0060] In this text, "modulation layer" refers to any entity that has an impact on the properties of light. Among them, the properties of light include transmission, refraction, absorption, etc. In some embodiments, the light modulation layer includes a phase change material layer made of a phase change material, or can be made of a phase change material.

[0061] The present invention proposes an optical waveguide with high stability and capable of industrial production, which includes: 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 the optical waveguide layer from being damaged during the window opening process, and a first protective layer covers the modulation layer. Among them, the modulation layer is made of a phase change material, or includes a phase change material layer (for the convenience of description, in subsequent embodiments, the phase change material layer is taken as an example of the modulation layer).

[0062] In the window opening link of current industrial production, it is very difficult to directly and perfectly open above the optical waveguide layer, that is, directly sputter or deposit the modulation layer on the optical waveguide layer without any loss of the waveguide layer during the window opening process. Therefore, in each example in this text, while protecting the optical waveguide layer (such as a first stop layer) by setting an isolation layer on the optical waveguide layer, the modulation layer is also wrapped. For example, by pre-setting a stop layer and an oxide layer with specified thicknesses on the optical waveguide layer (for example: a stop layer with a first thickness H1 or a third thickness H3, and an oxide layer with a second thickness H2), and then in the window opening process, by controlling the process parameters of the window opening process to control the etching depth on the stop layer, so that a stop layer with a specified thickness (for example, a fourth thickness H4) is retained on the optical waveguide layer, thereby avoiding certain damage to the optical waveguide while wrapping the modulation layer and ensuring its stability.

[0063] 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.

[0064] Of course, a predetermined thickness, such as an H4 isolation layer, can also be pre-deposited directly on the optical waveguide layer. During the subsequent windowing process, the oxide layer can be directly etched away. Specifically, etching can be stopped when the isolation layer is visible. Because 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 facilitates the modulation layer's effect on the evanescent field of light in the optical waveguide layer. In particular, when existing windowing processes prevent the thickness of the stop layer between the modulation layer and the optical waveguide layer from being reduced (e.g., less than 1 nm) by directly adjusting etching parameters, pre-depositing the isolation layer to a predetermined thickness (e.g., the minimum value of the range: 1 nm) can further reduce the thickness of the isolation layer by slightly overetching the pre-deposited oxide layer.

[0065] 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).

[0066] Example 1: See Figure 1a, is a schematic diagram of an optical waveguide structure according to an exemplary embodiment of the present invention. Specifically, the optical waveguide structure includes: 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 stop layer 04 (i.e., a first isolation layer) is provided between the optical waveguide layer 02 and the phase change material layer 03 (i.e., the modulation layer), and a first oxide layer 05 (i.e., a first protective layer) covers the phase change material layer 03. Preferably, the width of the first stop layer 04 (i.e., the length extending in the X-axis direction), the width of the optical waveguide layer 02 (i.e., the length extending in the X-axis direction), and the width of the phase change material layer 03 (i.e., the length extending in the X-axis direction) are the same.

[0067] See Figure 1a , on the substrate 01, a second stop layer 06 is provided around the first stop layer 04 and a first region on the phase change material layer 03 close to the first stop layer 04 (i.e., a partial sidewall region around the bottom of the phase change material layer 03 in contact with the first stop layer 04). The first thickness (i.e., the length extending in the Z-axis direction) H1 of the second stop layer 06 is greater than the fourth thickness H4 of the first stop 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), so that the first stop layer and the second stop layer enclose and form a wrapping layer that wraps upward (i.e., the surrounding edge of the wrapping component extends upward along the height direction of the surrounding sidewall from the bottom of the component to be wrapped) the first region on the side of the phase change material layer close to the optical waveguide layer; and a second oxide layer 07 is provided around the first oxide layer 05, the second region on the phase change material layer 03 close to the first oxide layer 05 (i.e., a partial sidewall region around the top of the phase change material layer 03 in contact with the first oxide layer 05), the second stop layer 06, and the optical waveguide layer 02, so that the first oxide layer and the second oxide layer corresponding to the above second region enclose and form a wrapping layer that wraps downward (i.e., the surrounding edge of the wrapping component extends downward along the height direction of the surrounding sidewall from the top of the component to be wrapped) the second region on the side of the phase change material layer away from the optical waveguide layer, that is, the above phase change material layer 03 is wrapped in a sealed cavity 001 formed by enclosing the first oxide layer 05, the second oxide layer 07, the first stop layer 04, and the second stop layer 06.

[0068] In some embodiments, a stop layer (for example, a second stop layer 06 having a first thickness H1 and a first width L1, where L1 is greater than the width L0 of the optical waveguide layer) and an oxide layer (for example, a second oxide layer 07 having a second thickness H2) can be pre-set on the optical waveguide layer. See Figure 3b and Figure 3gIn order to set the phase change material layer 03 on the optical waveguide layer 02, the oxide layer and the stop layer pre-covered on the optical waveguide layer 02 can be etched by a regional etching method to form a cavity with a top opening (or an open window), in preparation for the subsequent wrapping of the phase change material layer. For example, a regional etching method is used to open a window, and a stop layer with a fourth thickness H4 is retained directly above the optical waveguide layer, so that a first stop layer is formed between the bottom of the cavity or window and the optical waveguide layer. At the same time, a second stop layer with a second thickness H2 remains around the first stop layer. That is, when the phase change material is subsequently sputtered or deposited in the cavity or window, the first stop layer becomes the first isolation layer 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 with a fourth thickness H4 (for example, 1nm to 100nm) remains on the optical waveguide, thereby avoiding damage to the optical waveguide layer during the etching process or the window opening process, see. Figure 1b 、 Figure 3c and Figure 3h .

[0069] 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 of a specified thickness H0 (for example, 1nm to 1um) can be provided on the first stop 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 necessary to cover it with a sixth protective layer of thickness H6, for example, a first oxide layer 05. In order to ensure stability and avoid the situation where the oxide layer covering the phase change material layer 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 physical vapor deposition (PVD) or chemical vapor deposition (CVD) method.

[0070] Since the first stop layer 04 is obtained by performing regional etching on the original oxide layer and stop layer, and the phase change material is sputtered or deposited on the first stop layer, when the first oxide layer 05 with a sixth thickness H6 is further covered on the phase change material layer, the first oxide layer 05 (i.e., the oxide layer newly covered on the phase change material layer) and the second oxide layer 07 (i.e., the remaining partial oxide layer after the original oxide layer is etched) surrounding the first oxide layer 05 enclose a first groove 0011 with an opening facing the phase change material layer; while the first stop layer 04 and the second stop layer (i.e., the remaining partial stop layer after the original stop layer is etched) surrounding the first stop layer 04 enclose a second groove 0012 with an opening facing the phase change material layer 03, and the openings of the first groove 0011 and the second groove 0012 are oppositely arranged, such that the first groove 0011 and the second groove 0012 enclose a sealed cavity 001 (i.e., the sum of the height h1 of the first groove opening and the height h2 of the second groove opening is the height of the sealed cavity, 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 and the second groove are both rectangular, that is, the cross-section of the sealed cavity is rectangular.

[0071] In some embodiments, the upper surface of the first oxide layer 05 is flush with the upper surface of the second oxide layer 07. Of course, in other embodiments, the upper surface of the first oxide layer 05 is not flush with the upper surface of the second oxide layer 07; or, the first oxide layer covers a part of the upper surface of the second oxide (preferably, the part of the second oxide layer around the opening at the top of the cavity) or the entire upper surface.

[0072] 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-shaped).

[0073] In some embodiments, the above substrate can also be an SOI substrate, as long as the substrate enables the optical waveguide layer to have an optical bandgap of at least 1 eV.

[0074] Embodiment 2: In order to better protect and encapsulate the phase change material layer and at the same time reduce the process difficulty, the present invention also provides an optical waveguide with another exemplary structure, which includes each component in the above Embodiment 1. The difference is that in this exemplary optical waveguide, the sealed cavity 001 is only enclosed by the first oxide layer 05 (i.e., the first protective layer) located on the top of the phase change material layer 03, the first stop layer 04 (i.e., the first isolation layer) located at the bottom of the phase change material layer 03 (i.e., the modulation layer), and the second stop layer 06 (i.e., the second isolation layer) surrounding the phase change material layer 03 and the first stop layer 04, see Figure 1c and Figure 1d ; and the second protective layer 07 surrounds the first oxide layer 05, the second stop layer 06 and the optical waveguide layer 02 to form an almost fully encapsulated protection.

[0075] In some embodiments, the cross section of the second stop layer 06 surrounding the phase change material layer 03 and the first stop layer 04 is in an inverted L-shape, and the upper surface of the second stop layer 06 is flush with or slightly higher than the upper surface of the phase change material layer.

[0076] In some embodiments, when preparing the optical waveguide of the exemplary structure, a second oxide layer 07 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, wherein the top of the second stop layer 06 extends a wing along the width direction of the optical waveguide, so that the cross section of the second stop layer 06 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 The etching parameters of the regional etching method are set to form a cavity for accommodating the phase change material layer, that is, the second groove 0012 formed in the second stop layer 06 (that is, the first stop layer serves as the bottom of the second groove, and the second stop layer serves as the sidewall of the second groove) serves as a cavity for accommodating the phase change material layer, 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 stop layer, thereby making the prepared optical waveguide more stable and the processing technology less difficult.

[0077] In other embodiments, the second stop layer pre-installed on and around the optical waveguide layer 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.

[0078] Embodiment 3: For the optical waveguide with the above structure, the requirements for the size of the window opening in the window opening process are relatively strict. And since the side walls of the cavities obtained by etching all extend in the vertical direction (or are slightly inclined), when sputtering the phase change material, it may deposit on other surrounding positions. It is necessary to additionally remove this part of the phase change material or cover the same first protective layer on the phase change material deposited on the surrounding positions, which not only makes the window opening process difficult but also the operation more complex. Based on this, this article also provides an optical waveguide with another exemplary structure, which includes each component in the above Embodiment 1. The difference is that in this example, the phase change material layer 03 is wrapped in a closed cavity 001 with a horn-shaped or bowl-shaped cross-section formed by enclosing the first protective layer 05, the second protective layer 07, the first isolation layer 04, and the second isolation layer 06.

[0079] In some embodiments, the first protective layer 05 and the second protective layer 06 surrounding the second region of the first protective layer 05 and the phase change material layer 03 away from the optical waveguide layer enclose a first groove with an inverted U-shaped cross-section; the first isolation layer 04 and the second isolation layer 06 surrounding the first region of the first isolation layer and the phase change material layer 03 close to the optical waveguide layer enclose a second groove with a U-shaped cross-section. And in the same cross-section, the distance between the relatively arranged side walls of the first groove gradually decreases along the direction close to the optical waveguide layer (or along the downward vertical direction), while the distance between the relatively arranged side walls of the second groove gradually increases along the direction away from the optical waveguide layer (or along the upward vertical direction), and the openings of the first groove and the second groove are relatively arranged, so that the side walls of the first groove and the side walls of the second groove are smoothly connected and enclose to form a closed cavity.

[0080] In some embodiments, as described above, a stop layer and an oxide layer can be pre-set on the optical waveguide layer in advance, and then a bowl-shaped or horn-shaped cavity with a top opening is formed by regional etching. On the one hand, since the top opening of this cavity is large, that is, it expands the coverage area of the subsequent sputtering of the phase change material. The inclined window side walls 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, since the top opening is large and the surrounding side walls have a certain inclination or curvature, that is, non-vertical etching, compared with the etching process of the optical waveguide structure in Embodiment 1 or Embodiment 2, its difficulty is lower.

[0081] Embodiment 4: Method for manufacturing an optical waveguide. Refer to Figure 2a , which is a flowchart of the method for manufacturing an optical waveguide according to an exemplary embodiment of the present invention. Specifically, the method includes the steps:

[0082] S101, Integrate an optical waveguide layer on a substrate to form an optical waveguide platform.

[0083] In some embodiments, step S101 is completed using the conventional pulsed laser deposition technique (PLD), such as the process method disclosed in Chinese Patent CN1487636A, which will not be elaborated herein. Refer to Figure 3a , taking a strip waveguide as an example, an optical waveguide layer 02 is integrated on a substrate 01 to form an optical chip with an optical waveguide platform.

[0084] 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 is selected from: silicon, silicon nitride, gallium nitride, gallium arsenide, aluminum nitride, magnesium oxide, and diamond (polycrystalline or single crystal).

[0085] S103, a stop layer and an oxide layer are formed on the outer surface of the optical waveguide layer exposed above the substrate by physical vapor deposition or chemical vapor deposition, wherein the stop layer is located above the optical waveguide and has a width greater than that of the optical waveguide layer.

[0086] In some embodiments, a stop layer and a thicker oxide layer are sequentially formed on the outer surface of the optical waveguide layer exposed above the substrate. Among them, the function of the stop layer is to provide an isolation layer above the waveguide layer to isolate the dry etching process of the oxide layer. When performing dry etching of the oxide layer, the dry etching reaction will stop when reaching the stop layer, thus achieving the effect of etching the oxide layer without affecting the waveguide itself; at the same time, it also forms a wrapping effect on the modulation layer, improving the stability of the modulation layer when switching between amorphous and crystalline states. And the function of the thicker oxide layer is to protect the waveguide and the metal interconnection layer, and at the same time play a role in insulating silicon from the metal interconnection layer and between metal interconnection layers.

[0087] In some embodiments, the material of the oxide layer is one of silicon oxide (SiO2), aluminum oxide (Al2O3), or ITO. Preferably, the material of the oxide layer is silicon oxide (SiO2). The material of the stop layer is one or more of silicon nitride (Si3N4), titanium nitride (TiN). Preferably, the material of the stop layer is silicon nitride (Si3N4).

[0088] In some embodiments, both the stop layer and the oxide layer adopt basic film coating processes, which include many types, including vacuum evaporation, ion beam sputtering, magnetron sputtering, chemical vapor deposition CVD, etc. The specific process parameters of this film coating process vary to some extent in different silicon photonics wafer factories, which is a relatively common existing technology and will not be elaborated herein. It should be noted that when depositing the oxide layer, a conventional physical vapor deposition (PVD) or chemical vapor deposition (CVD) process is used to simultaneously embed the metal interconnection layer 5 therein, and the metal interconnection layer 5 is connected to the optical waveguide layer through a via hole.

[0089] Refer to Figure 2bAnd Figure 3b Taking the strip waveguide as an example, on the outer surface of the optical waveguide layer 02 exposed on the substrate 01, a second stop layer 06 with a first thickness H1 and a second oxide layer 07 with a second thickness H2 are sequentially formed (i.e., S1013). In order to wrap the phase change material layer (for example, partial wrapping and almost full wrapping), the width of the second stop layer is greater than the width of the optical waveguide layer, so that a groove can be formed on the second stop layer in the subsequent window opening process. The bottom of the groove between the phase change material layer and the optical waveguide layer is the first isolation layer, and the groove wall surrounding the first isolation layer is the second isolation layer.

[0090] See Figure 2c In some other embodiments, in order to ensure that the phase change material layer is almost wrapped by the stop layer, for example, the upper surface of the phase change material layer is almost flush with the upper surface of the second stop layer, so that the second stop layer remains around the periphery of the phase change material layer. A second oxide layer 07 and a second stop layer with a T-shaped cross-section can be first formed on the outer surface of the optical waveguide layer 02 exposed on the substrate 01 (i.e., S1023). Among them, the width L1 of the vertical part in the T shape is greater than the width L0 of the optical waveguide layer 02, so as to ensure that during the subsequent etching process, when etching to the second stop layer, a part of the stop layer can be reserved around and at the bottom of the phase change material layer. The part located between the optical waveguide layer and the phase change material layer is the first stop layer (with a thickness of H4). Of course, in some other embodiments, a second oxide layer 07 and a second stop layer with a concave-shaped cross-section are also first formed on the outer surface of the optical waveguide layer 02 exposed on the substrate 01, and the width of the concave shape is greater than the width of the optical waveguide layer 02, so as to ensure that during the subsequent etching process, when etching to the second stop layer, a part of the stop layer can be reserved around and at the bottom of the phase change material layer. Among them, the part located between the optical waveguide layer and the phase change material layer is the first stop layer (with a thickness of H4).

[0091] S105, perform the window opening process of the stop layer and the oxide layer by a regional etching method, so that a stop layer remains on the optical waveguide layer.

[0092] In some embodiments, perform the window opening process of the stop layer and the oxide layer by a regional etching method to expose a part of the stop layer covered on the optical waveguide layer.

[0093] The current conventional regional etching window opening process is a combination of dry etching + wet etching or dry etching + dry etching. When performing etching by dry etching, the oxide layer of the part that needs to be windowed is etched until reaching the stop layer. By dry etching or wet etching, the stop layer of the part that needs to be windowed is etched to above the waveguide. The specific parameters vary in different silicon photonics chip factories, but mainly depend on the oxide layer process, stop layer process, dry etching process, and wet etching process. It is also a relatively common existing technology and will not be elaborated here.

[0094] In some embodiments, in S105, it should be noted that: the regional etching and windowing process must avoid the metal interconnect layer 5 and the vias, that is, the metal interconnect layer 5 and the vias cannot be exposed in the window, and the metal interconnect layer and the vias need to have a certain distance from the etched area of the windowing process. The specific distance size is determined according to the process level of different silicon photonics wafer factories.

[0095] As mentioned above, due to the limitations of the etching process in existing industrial production, it is very difficult for the windowing process to directly and perfectly open above the optical waveguide, that is: on the premise of not causing any damage to the optical waveguide, there is no excess stop layer and / or oxide layer remaining on the optical waveguide layer. Therefore, in this method, in step S103 in advance, by pre-setting a stop layer with a first thickness H1 or a third H3 and an oxide layer with a second thickness H2 on the optical waveguide layer 02, and then performing windowing on the oxide layer and the stop layer through the regional etching and windowing process, and retaining a stop layer with a fourth thickness H4 on the optical waveguide layer 02, that is, in the windowing area, the stop layer on the optical waveguide layer is not completely etched away, but a groove is etched out on the stop layer (see Figure 2b S1015 in Figure 2c or S1025 in

[0096] On the other hand, as mentioned above, considering the influence of the stop layer on the evanescent field range of light in the optical waveguide layer by the phase change material layer, preferably, the fourth thickness H4 of the formed first stop layer is 1 nm to 100 nm.

[0097] In some embodiments, the area of the stop layer exposed in the windowing process is determined by the area of the phase change material to be deposited. Preferably, the area of the exposed stop layer is the same as the area of the phase change material layer.

[0098] See Figure 3c , taking the strip waveguide as an example, through the regional etching method for the windowing process of the stop layer and the oxide layer, a part of the stop layer with a fourth thickness H4 (H4 < H1) covered on the optical waveguide layer is exposed, that is, the first stop layer 04; and the area of the first stop layer is the same as the area of the phase change material layer to be set subsequently.

[0099] To ensure that the area of the exposed stop layer is the same as or not much different from the area of the phase change material layer, the control parameters of the etching process are required to be very precise, that is, the processing difficulty is relatively high, and the requirements for the subsequent sputtering process are also relatively high. In view of this, when etching in step S105 or S1015, the windowing is not performed according to the above 1:1 (or close to 1:1) area, but a bowl-shaped or horn-shaped cavity (or window) is etched out, and then the phase change material is sputtered therein, and finally a first oxide layer 05 with a sixth thickness H6 is deposited, thereby obtaining Figure 1eAn optical waveguide with the structure shown.

[0100] S107. Deposit the phase change material onto the surface of the stop layer exposed within the window by physical vapor deposition using the first thin film deposition process to form a phase change material thin film.

[0101] In some embodiments, sputter the phase change material onto the upper surface of the stop layer exposed within the window using the first sputtering process to form a phase change material thin film (i.e., the phase change material layer 03).

[0102] In some embodiments, the phase change material can be formed of or include a chalcogenide containing antimony or selenium, such as antimony selenide (Sb2Se3 or SbSe), antimony sulfide (Sb2S3 or SbS), Ge2Sb2Se4Te (GSST); or the phase change material can include or be composed of a compound or alloy of an element combination selected from GeSbTe, VOx, NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

[0103] Of course, the phase change material can also include a mixture of the above compounds, or the phase change material can be a superlattice.

[0104] In some embodiments, the above first thin film deposition process is a magnetron sputtering process, and its specific process is as follows: After placing the optical chip in step S105 into the vacuum chamber, start pumping the vacuum chamber. After reaching a vacuum degree of 1×10 -6 Torr, introduce argon gas and continue pumping the vacuum to keep the process vacuum degree lower than 3.5×10 -3 Torr; turn on the magnetron sputtering RF power supply, control the power at 10 - 100W, and control the formed phase change material thin film to be between 1nm and 1μm.

[0105] See Figure 3d , taking the strip waveguide as an example, directly sputter the phase change material in the cavity to obtain a phase change material layer with a thickness of 1nm - 1μm.

[0106] In some embodiments, deposit a phase change material layer with a preset thickness H0 within the window such that the sum of the preset thickness H0 and the fourth thickness H4 is greater than the first thickness H1, so that the groove etched on the stop layer wraps the bottom of the modulation layer and the first region close to the optical waveguide layer (see S1017 in Figure 2b and Figure 1a , Figure 1b and Figure 1e , Figure 1f), that is, an etch stop layer forms a wrapping layer that wraps part of the modulation layer after etching.

[0107] In some other embodiments, a phase change material layer with a preset thickness H0 is deposited within the window, such 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 grooves etched in the etch stop layer wrap the bottom and all sidewalls of the etch stop layer (see Figure 2c S1027 in Figure 1c and Figure 1d ), that is, an etch stop layer forms a wrapping layer that almost entirely wraps the modulation layer (except for the top surface of the modulation layer not being wrapped) after etching.

[0108] 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 to achieve coverage, realizing the heterogeneous integration of the phase change material and the optical waveguide platform, thereby obtaining an optical waveguide.

[0109] 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 to achieve coverage, and then realizes the heterogeneous integration of the phase change material and the optical waveguide platform, 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.

[0110] In some embodiments, the specific process of depositing an oxide layer on the phase change material layer using physical vapor deposition (PVD) includes: after placing the optical chip that has undergone step S107 into the vacuum chamber, starting to evacuate the vacuum chamber, and after reaching a vacuum degree of 1×10-6 Torr, introducing argon gas and continuing to evacuate the vacuum, maintaining the process vacuum degree below 3.5×10-3 Torr, turning on the magnetron sputtering RF power supply, controlling the power at 10-200 W, and controlling the thickness of the formed oxide layer film to be between 0.1 and 3 μm.

[0111] In some other embodiments, the specific process of depositing an oxide layer on the phase change material layer using chemical vapor deposition (CVD) includes: after placing the optical chip that has undergone step S107 into the vacuum chamber, starting to evacuate the vacuum chamber, and after reaching a vacuum degree of 1×10 -6 Torr, heating the substrate to between 150°C and 350°C, introducing N2, SiH4, and N2O gases, maintaining the deposition pressure between 0.2 Torr and 2.0 Torr, turning on the RF power supply, controlling the power at 20 W-150 W, and controlling the thickness of the formed oxide layer film to be between 0.1 μm and 3 μm.

[0112] See Figure 3e, taking a strip waveguide as an example, an oxide layer made of the same material as in step S103 is deposited onto the phase change material layer 03 through a second thin film deposition process to obtain a first oxide layer 05 with a thickness of H6, thereby realizing the heterogeneous integration of the phase change material and the optical waveguide platform.

[0113] Example 5: Stability test. Generally, a voltage pulse can be used to cause a reversible phase change between the crystalline state and the amorphous state in the phase change material layer on the waveguide. Among them, when the phase change material layer is in the crystalline state, the optical power passing through the waveguide is relatively low, while when the phase change material layer is in the amorphous state, the optical power passing through the waveguide is relatively high. Therefore, the stability of the phase change material layer can be represented by the optical power transmitted through the optical waveguide containing the phase change material.

[0114] Taking the optical waveguide prepared by the existing conventional integrated phase change material method as the control group below, and taking the optical waveguide of Example 1 above in this article as the experimental group, by performing cyclic modulation of melting and crystallization on the phase change material layer in the optical waveguides of the control group and the experimental group, and respectively obtaining the optical power of the two groups of optical waveguides during the cyclic modulation, the respective cyclic modulation optical power diagrams are obtained. See Figure 4 (control group) and Figure 5 (experimental group).

[0115] Specifically, during the cyclic modulation process, the materials of the phase change material layers in the two groups of optical waveguides are the same, and the thicknesses are the same (both are 30 nm), and the modulation parameters of the same modulator are used; the pulse voltage for melting the phase change material layer (changing from the crystalline state to the amorphous state) is 9 V, and the duration is 200 ns; the pulse voltage for crystallization (changing from the amorphous state to the crystalline state) is 3 V, and the duration is 1 μs.

[0116] Control group: See Figure 4 , under the existing integrated phase change material method, cyclic modulation of melting-crystallization is performed on the phase change material layer integrated on the optical waveguide. After the phase change material layer is remelted or recrystallized, the optical power cannot be maintained at the same level, and the optical power fluctuates greatly during the cyclic modulation process (that is, during the cyclic modulation process, the optical powers in the two states deviate far from their respective mean lines: the mean line S1 of the optical power in the crystalline state and the mean line S2 of the optical power in the amorphous state), indicating 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.

[0117] Experimental group: See Figure 5, in the optical waveguide shown in the above Embodiment 1, during the cyclic modulation process of the phase change material layer between melting and crystallization, 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 (that is, during the cyclic modulation process, the optical power in the two states almost coincides with their respective mean lines: the mean optical power line S3 in the crystalline state and the mean optical power line S4 in the amorphous state, or the deviation is very small), indicating that the phase change material is stable during the cyclic modulation process and the state of the phase change material can be stably modulated under the existing structure.

[0118] In this article, shape descriptors such as L-shaped, T-shaped, concave-shaped, etc. using words (such as Chinese or English, etc.) include the shapes of the words in various font forms, and also include structures with non-standard character shapes. For example, the top of the L-shaped can have a protruding short side extending horizontally (shorter than the bottom), as long as its general structure looks like the corresponding character shape. Similarly, various structures described by geometric shapes in this article include standard geometric shapes and non-standard geometric shapes (or called similar or approximate shapes). For example, the rectangle in this article includes the standard rectangle in geometric shapes and can also be a non-standard approximate rectangle. For example, due to factors such as process limitations, the side walls of the sealed cavity formed by the butt joint of the side walls of the first groove and the second groove have a slight inclination, or there is a slight deviation when the side walls of the first groove and the second groove are butted, but overall, the structure still looks close to a rectangle.

[0119] It should be noted that in this article, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or also includes elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including one..." does not exclude the existence of another identical element in the process, method, article or device including that element.

[0120] The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present invention, those of ordinary skill in the art can also make many forms without departing from the spirit and scope protected by the claims of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A method for preparing an optical waveguide, characterized in that, Including the steps: 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 H4 and a second oxide layer with a second thickness H2 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; 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 H4 on the optical waveguide layer, and a second isolation layer surrounding the first isolation layer; the thickness of the first isolation layer is 1 nm - 100 nm; S1017, depositing a phase change material onto the surface of the first isolation layer exposed in the window by a first thin film deposition process through physical vapor deposition 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 made 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.

2. The method for preparing an optical waveguide according to claim 1, wherein, The length of the first isolation layer extending along the waveguide length direction is 1 μm - 10 μm.

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

4. A method for preparing an 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.

5. A method for preparing an optical waveguide according to any one of claims 1 to 3, characterized in that, 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, Ge2Sb2Se4Te.

6. A method for preparing an optical waveguide according to any one of claims 1 to 3, characterized in that, The phase change material includes a compound or alloy or a mixture of the compound containing an elemental combination of germanium, antimony, selenium, and vanadium oxide; the compound includes NbOx, GeTe, GeSb, GaSb, AgInSbTe, InSb, InSbTe, InSe, SbTe, TeGeSbS, AgSbSe, SbSe, GeSbMnSn, AgSbTe, AuSbTe, and AlSb.

7. A method for preparing an optical waveguide according to any one of claims 1 to 3, characterized in that, The second oxide layer is made of any one or more of SO2, Al2O3, and ITO.

8. A method for preparing an optical waveguide according to any one of claims 1 to 3, characterized in that, The second stop layer is made of one or two of Si3N4 and TiN.

9. An optical waveguide prepared by the method for preparing an optical waveguide according to any one of claims 1 to 8, 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. It further includes: 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 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; the area of the phase change material layer is the same as the area of the first isolation layer; Wherein, the thickness of the first isolation layer is 1 nm to 100 nm.

10. The optical waveguide according to claim 9, 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; 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, 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 waveguide layer, while the distance between the opposite 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 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 trumpet shape.

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