Processing technology of optical waveguide structure and preparation method of optical waveguide sheet

Abstract

The invention relates to a processing technology of an optical waveguide structure and a preparation method of an optical waveguide sheet, and the processing technology of the optical waveguide structure comprises the steps: processing a substrate, and carrying out the cleaning pretreatment of a substrate layer; a transition layer is deposited, specifically, the transition layer is deposited on the surface of the pretreated substrate layer, and the transition layer comprises at least one first bonding element bonded with the substrate layer and at least one second bonding element bonded with the optical waveguide layer; and optical waveguide layer deposition: depositing an optical waveguide layer on one side, far away from the substrate layer, of the transition layer, so that the refractive index of the optical waveguide layer is greater than that of the transition layer. The three layers of structures are overlapped to form the optical waveguide sheet, so that the technical effect of reducing the processing difficulty of the optical waveguide sheet is achieved.

Description

Technical Field

[0001] This application relates to the field of optical element technology, and in particular to a fabrication process for an optical waveguide structure and a method for preparing an optical waveguide sheet. Background Technology

[0002] Augmented reality (AR) glasses, as a new generation of smart wearable devices, rely on waveguides for their core functions. Waveguides are key optical components in AR glasses that are responsible for transmitting virtual imaging light and superimposing real natural light. They directly determine the field of view, imaging clarity, and wearing comfort of AR glasses. They are the core carrier for achieving the "virtual-real fusion" visual effect and are widely used in many fields such as consumer electronics, industrial assistance, and medical surveying.

[0003] In existing technologies, silicon carbide (SiC) is often used as the core substrate material for AR glasses waveguides. This is because silicon carbide possesses excellent optical and mechanical properties such as high refractive index, high thermal stability, and high hardness, which can meet the core requirements of waveguides for efficient transmission of virtual light and suppression of dispersion. However, the thickness of silicon carbide waveguides is usually around 650 μm. Silicon carbide waveguides with this thickness present significant processing challenges. Silicon carbide itself is extremely brittle and has low fracture toughness. During ultra-precision polishing, cutting, and edge chamfering, defects such as chipping, cracking, and breakage are very likely to occur. At the same time, thick silicon carbide substrates require semiconductor-grade ultra-precision processing technology, which is difficult to process and has a long cycle time. This results in low yield rate and high production cost of waveguides, which seriously restricts the large-scale mass production and widespread application of AR glasses.

[0004] Therefore, the technical problem with existing technologies is that optical waveguide sheets are difficult to process. Summary of the Invention

[0005] This application provides a processing technology for an optical waveguide structure and a method for fabricating an optical waveguide sheet. By stacking three layers to form an optical waveguide sheet, the technical effect of reducing the processing difficulty of the optical waveguide sheet is achieved.

[0006] Firstly, this application provides an optical waveguide structure that adopts the following technical solution: An optical waveguide structure, comprising: A base layer, wherein the base layer is a light-transmitting material; A transition layer is stacked on the base layer; An optical waveguide layer, wherein the optical waveguide layer is stacked on the transition layer; The substrate, the transition layer, and the optical waveguide layer are made of transparent materials; the substrate and the optical waveguide layer are connected by the transition layer, and the refractive index of the optical waveguide layer is greater than that of the transition layer; the transition layer contains at least one first bonding element that bonds with the substrate and at least one second bonding element that bonds with the optical waveguide layer.

[0007] Preferably, in the transition layer, the content of the first bonding element gradually decreases along the first direction, and the content of the second bonding element gradually increases along the first direction, wherein the first direction is the direction from the substrate layer to the optical waveguide layer.

[0008] Preferably, the optical waveguide layer is silicon carbide.

[0009] Preferably, the thickness of the optical waveguide layer is between 400 and 600 nm.

[0010] Preferably, the base layer is sapphire, and the transition layer is made of XN, where X is Al or Ga.

[0011] Preferably, in the transition layer, the X content gradually decreases along the first direction, and the N content gradually increases along the first direction until the atomic ratio of X to N is 1:1, wherein the first direction is the direction from the substrate layer to the optical waveguide layer.

[0012] Preferably, the base layer is sapphire, and the transition layer is made of Al. i Ga (1-i) N, where i∈(0,1).

[0013] Preferably, in the transition layer, i gradually decreases along a first direction, wherein the first direction is the direction from the substrate layer to the optical waveguide layer.

[0014] Preferably, the substrate layer is a single crystal quartz, the optical waveguide layer is silicon carbide, and the transition layer is made of Si3N4 or AlN-SiO2. x N y Composite layer; wherein, in the first direction of the transition layer, the Si element content in the Si3N4 layer gradually increases, and the N element content gradually decreases to an atomic ratio of 3:4; AlN-SiO x N y The proportion of AlN in the composite layer gradually increases, while that of SiO gradually decreases. x N y The proportion gradually decreases, and the Al content of AlN gradually decreases while the N content gradually increases to an atomic ratio of 1:1; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer is a single crystal of magnesium oxide, the optical waveguide layer is silicon carbide, and the transition layer is made of MgAl2O4 or a MgAl2O4-AlN composite layer; wherein, in the first direction of the transition layer, the proportion of MgAl2O4 in the MgAl2O4-AlN composite layer gradually decreases, the proportion of AlN gradually increases, and the Al content of AlN gradually decreases while the N content gradually increases, until the atomic ratio of Al to N is 1:1; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be high-alumina-silicon optical glass, the waveguide layer may be silicon carbide, and the transition layer may be made of amorphous AlO₂. x N y or SiO x N y； Wherein, AlO x N y In the layer, the oxygen content of Al gradually decreases while the nitrogen content gradually increases, and the SiO content gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be borosilicate glass, the optical waveguide layer may be silicon carbide, and the transition layer may be an amorphous SiO2-TiO2 composite layer or SiO2. x N y In the first direction of the transition layer, the proportion of TiO2 in the SiO2-TiO2 composite layer gradually increases, while the proportion of SiO2 gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be sapphire, the waveguide layer may be GaN, and the transition layer may be made of Al. i Ga (1-i) N; wherein, in the first direction of the transition layer, the value of i gradually decreases, and the atomic ratio of Al / Ga to N gradually transitions to 1:1; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be quartz glass, the optical waveguide layer may be TiO2, and the transition layer may be made of Si3N4 or TiO2. x N y In the first direction of the transition layer, the atomic ratio of Si to N in the Si3N4 layer gradually decreases until it reaches 3:4; TiO x N yThe oxygen content of Ti in the layer gradually decreases while the nitrogen content gradually increases until the atomic ratio of Ti to O is 1:2; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be soda-lime glass or high-alumina-silicon optical glass, the optical waveguide layer may be ZnO, and the transition layer may be made of ZnO. x AlN or AlO x N y Wherein, in the first direction of the transition layer, ZnO x In the AlN layer, the proportion of Zn gradually increases while the proportion of Al gradually decreases. x N y The oxygen content of Al in the layer gradually decreases while the nitrogen content gradually increases; the first direction is the direction from the substrate layer to the optical waveguide layer.

[0015] Secondly, the optical waveguide sheet provided in this application adopts the following technical solution: An optical waveguide sheet, comprising the aforementioned optical waveguide structure, further comprising: A coupling element, disposed on the optical waveguide layer, the coupling element comprising: A coupling unit is used to couple virtual imaging light into the optical waveguide layer, so that the virtual imaging light satisfies the total internal reflection condition and is propagated in the optical waveguide layer. The coupling unit is used to couple and emit virtual imaging light from the optical waveguide layer on the side of the optical waveguide layer away from the transition layer.

[0016] Preferably, the spatial region in which the coupling unit couples out virtual imaging light on the side of the optical waveguide layer away from the transition layer is an eyebox; Multiple coupling elements are disposed on the optical waveguide layer. In each group of coupling elements, the coupling-in unit and the coupling-out unit are matched one-to-one to form an eyebox array on the side of the optical waveguide layer away from the transition layer. The eyebox array is arranged along the direction perpendicular to the thickness of the waveguide sheet.

[0017] Thirdly, the lens provided in this application adopts the following technical solution: A lens comprising the aforementioned optical waveguide sheet.

[0018] Fourthly, the AR glasses provided in this application adopt the following technical solution: An AR glasses device, comprising the aforementioned lens.

[0019] Fifthly, the fabrication process of the optical waveguide structure provided in this application adopts the following technical solution: A fabrication process for an optical waveguide structure, used to prepare the optical waveguide structure, comprising: Substrate treatment: cleaning and pretreatment of the substrate layer; Transition layer deposition: A transition layer is deposited on the surface of a pretreated substrate layer, wherein the transition layer contains at least one first bonding element that bonds to the substrate layer and at least one second bonding element that bonds to the optical waveguide layer. Optical waveguide layer deposition: An optical waveguide layer is deposited on the side of the transition layer away from the substrate layer, such that the refractive index of the optical waveguide layer is greater than the refractive index of the transition layer.

[0020] Preferably, the transition layer deposition further includes: In a first direction, the content of the first bonding element is gradually reduced, and the content of the second bonding element is gradually increased; wherein, the first direction is the direction from the substrate layer to the optical waveguide layer.

[0021] Preferably, the optical waveguide layer deposition further includes: The optical waveguide layer is silicon carbide, which is deposited by low-pressure chemical vapor deposition or plasma-enhanced chemical vapor deposition.

[0022] Preferably, the silicon carbide deposition thickness is 400–600 nm.

[0023] Preferably, the substrate layer is a sapphire single crystal, and the transition layer is XN, wherein X is Al or Ga; The transition layer deposition further includes: depositing the transition layer using metal-organic chemical vapor deposition, by adjusting the flow rates of the X source and the N source, so that the X content gradually decreases along the first direction and the N content gradually increases along the first direction, until the atomic ratio of X to N is 1:1, wherein the first direction is the direction from the substrate layer to the optical waveguide layer.

[0024] Preferably, on a pretreated substrate, hydrogen gas and a trimethylaluminum pre-laid Al layer are introduced into the MOCVD reaction chamber at 40–60 mbar and 800–850 °C. Aluminum nitride layers were grown by introducing hydrogen, ammonia, and trimethylaluminum under conditions of 60–65 mbar and 1005–1255 °C. During the growth of the aluminum nitride layer, the gradient of Al content is reduced by adjusting the reaction chamber temperature, the flow rate of trimethylaluminum, and the inlet ratio, while the gradient of N content is increased by adjusting the flow rate of ammonia and the inlet ratio, so that the Al:N atomic ratio of the aluminum nitride transition layer near the optical waveguide layer reaches 1:1.

[0025] Preferably, the substrate layer is a sapphire single crystal, and the transition layer is Al. i Ga (1-i) N, where i∈(0,1); The transition layer deposition further includes: depositing the transition layer using metal-organic chemical vapor deposition, and adjusting the flow rates of the Al source, Ga source and N source to gradually decrease the i value along the first direction.

[0026] Preferably, after depositing the aluminum nitride transition layer, a silicon carbide optical waveguide layer is epitaxially grown on the surface of the aluminum nitride transition layer, including: Hydrogen gas was introduced into the reaction chamber as a carrier gas, and the surface of the aluminum nitride transition layer was etched in situ for 10 to 30 minutes at a pressure of 60 to 150 mbar and a temperature of 1500 to 1700 °C. While maintaining constant pressure and temperature in the reaction chamber, a Si source, a C source, and an optional doping source are introduced to control the carbon-to-silicon ratio at 0.6–1.2, and a silicon carbide layer with a thickness of 400–600 nm is grown. The doping source is diluted through at least one stage of dilution pipeline before entering the reaction chamber, and the doping concentration is controlled by adjusting the flow rate of the doping source dilution gas. Turn off the gas source, gradually cool the reaction chamber to 600-1000℃ and pressurize it to 900-1100mbar, purge with inert gas, and then cool and remove it.

[0027] Preferably, the substrate layer is a single crystal quartz, the optical waveguide layer is silicon carbide, and the transition layer is made of Si3N4 or AlN-SiO2. x N y Composite layer; wherein, in the first direction of the transition layer, the Si element content in the Si3N4 layer gradually increases, and the N element content gradually decreases to an atomic ratio of 3:4; AlN-SiO x N y The proportion of AlN in the composite layer gradually increases, while that of SiO gradually decreases. x N y The proportion gradually decreases, and the Al content of AlN gradually decreases while the N content gradually increases to an atomic ratio of 1:1; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer is a single crystal of magnesium oxide, the optical waveguide layer is silicon carbide, and the transition layer is made of MgAl2O4 or a MgAl2O4-AlN composite layer; wherein, in the first direction of the transition layer, the proportion of MgAl2O4 in the MgAl2O4-AlN composite layer gradually decreases, the proportion of AlN gradually increases, and the Al content of AlN gradually decreases while the N content gradually increases, until the atomic ratio of Al to N is 1:1; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be high-alumina-silicon optical glass, the waveguide layer may be silicon carbide, and the transition layer may be made of amorphous AlO₂. x N y or SiO x N y；Wherein, AlO x N y In the layer, the oxygen content of Al gradually decreases while the nitrogen content gradually increases, and the SiO content gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be borosilicate glass, the optical waveguide layer may be silicon carbide, and the transition layer may be an amorphous SiO2-TiO2 composite layer or SiO2. x N y In the first direction of the transition layer, the proportion of TiO2 in the SiO2-TiO2 composite layer gradually increases, while the proportion of SiO2 gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be sapphire, the waveguide layer may be GaN, and the transition layer may be made of Al. i Ga (1-i) N; wherein, in the first direction of the transition layer, the value of i gradually decreases, and the atomic ratio of Al / Ga to N gradually transitions to 1:1; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be quartz glass, the optical waveguide layer may be TiO2, and the transition layer may be made of Si3N4 or TiO2. x N y In the first direction of the transition layer, the atomic ratio of Si to N in the Si3N4 layer gradually decreases until it reaches 3:4; TiO x N y The oxygen content of Ti in the layer gradually decreases while the nitrogen content gradually increases until the atomic ratio of Ti to O is 1:2; the first direction is the direction from the substrate layer to the optical waveguide layer; Alternatively, the substrate layer may be soda-lime glass or high-alumina-silicon optical glass, the optical waveguide layer may be ZnO, and the transition layer may be made of ZnO. x AlN or AlO x N y Wherein, in the first direction of the transition layer, ZnO x In the AlN layer, the proportion of Zn gradually increases while the proportion of Al gradually decreases. x N y The oxygen content of Al in the layer gradually decreases while the nitrogen content gradually increases; the first direction is the direction from the substrate layer to the optical waveguide layer.

[0028] Sixthly, this application provides a method for fabricating an optical waveguide sheet, which adopts the following technical solution: A method for fabricating an optical waveguide sheet, comprising fabricating a coupling element on the surface of the optical waveguide layer of the optical waveguide structure, wherein fabricating the coupling element includes: Photolithography involves coating the surface of the optical waveguide layer with photoresist and fabricating a photoresist mask using electron beam lithography. Etching: Using the photoresist mask as a mask, the optical waveguide layer is etched using a dry etching process to form coupling-in units and coupling-out units. The coupling-in units are used to couple virtual imaging light into the optical waveguide layer, so that the virtual imaging light satisfies the total internal reflection condition and is propagated within the optical waveguide layer. The coupling-out units are used to couple and emit the virtual imaging light in the optical waveguide layer from the side of the optical waveguide layer away from the transition layer.

[0029] As a preferred option, it also includes: Fabricate multiple sets of photoresist masks; Multiple sets of coupling elements are formed by etching in a direction perpendicular to the thickness of the waveguide sheet. In each set of coupling elements, the coupling-in unit and the coupling-out unit are matched one-to-one, so that an eyebox array is formed on the side of the optical waveguide layer away from the transition layer. The eyebox array is arranged in a direction perpendicular to the thickness of the waveguide sheet.

[0030] In summary, this application includes at least one of the following beneficial technical effects: The three-layer structure of the optical waveguide structure in this application assumes the waveguide support function of the substrate layer and the light guiding function of the thin optical waveguide layer. Only the easily processed transparent substrate layer needs to be processed into a thick sheet, and the difficult-to-process silicon carbide only needs to be deposited in a thin layer. There is no need to perform ultra-precision processing such as cutting, polishing, and chamfering on the thick silicon carbide, which greatly reduces the overall processing difficulty. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the optical waveguide structure described in this application; Figure 2 This is a schematic diagram of the optical waveguide sheet described in this application; Figure 3 This is a schematic diagram of the coupling element of the optical waveguide sheet described in this application; Figure 4 This is a schematic flowchart of the fabrication process of the optical waveguide structure described in this application; Figure 5 This is a schematic flowchart of the fabrication method of the optical waveguide sheet described in this application.

[0032] Explanation of reference numerals in the attached figures: 110, Substrate layer; 120, Transition layer; 130, Optical waveguide layer; 140, Coupling element; 141, Coupler unit; 142, Coupler output unit; 200, Eyebox; 210, Eyebox array; 300, Optomechanical 300. Detailed Implementation

[0033] The serial numbers assigned to components in this document, such as "first" and "second," are used solely to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages). It should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are used solely for the convenience of describing this application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0034] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0035] To better understand the above technical solutions, a detailed description of the technical solutions will be provided below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit the scope of this application.

[0036] As smart wearable devices rapidly iterate towards lightweight, high-definition, and scenario-based applications, augmented reality (AR) glasses have gradually broken through the limitations of the consumer electronics field and widely penetrated into multiple core scenarios such as industrial assistance, medical surveying, outdoor navigation, and education and training, becoming a core interactive carrier connecting virtual information and the real world. The core competitiveness of AR glasses lies in the "virtual-real fusion" visual experience, and the realization of this experience depends entirely on the waveguide, a key optical component. The waveguide undertakes the core functions of efficient transmission of virtual imaging light, unobstructed transmission of real natural light, and precise superposition of the two. Its performance directly determines the field of view, image clarity, and light loss of AR glasses, and also affects the overall thickness of the device and wearing comfort. It is the core bottleneck for the miniaturization and practicality of AR glasses.

[0037] Silicon carbide (SiC) has become the mainstream choice for the core substrate material of waveguide sheets due to its excellent comprehensive performance. Compared with traditional light-transmitting materials such as quartz and glass, silicon carbide has an extremely high refractive index (up to 2.6 or higher), which can efficiently achieve total internal reflection of virtual imaging light and significantly reduce light loss. At the same time, it has excellent thermal stability and mechanical hardness, can adapt to temperature changes in different scenarios, and can withstand minor friction in daily use, meeting the requirements for long-term stable operation of waveguide sheets. It is especially suitable for the stringent requirements of high-end AR glasses for virtual light transmission efficiency and dispersion suppression.

[0038] However, the application of existing silicon carbide waveguides faces insurmountable processing technology bottlenecks. Limited by material properties and optical performance requirements, the thickness of existing silicon carbide waveguides is typically controlled at around 650 μm. This thickness presents a significant contradiction with the inherent brittleness and low fracture toughness of silicon carbide. During mass production of waveguides, key processes such as ultra-precision polishing, high-precision cutting, and edge chamfering all face severe challenges: the high brittleness of silicon carbide makes it prone to surface scratches and chipping during polishing, and cracking and breakage during cutting. Edge chamfering is particularly difficult to control in terms of precision, easily leading to corner breakage and product scrap. Furthermore, thick silicon carbide substrates require semiconductor-grade ultra-precision processing equipment and processes, which are not only extremely difficult to process but also have long processing cycles, further hindering the improvement of waveguide mass production yield (typically less than 60%) and keeping processing costs high.

[0039] The aforementioned processing challenges directly restrict the large-scale mass production and widespread application of AR glasses. On the one hand, high scrap rates and long processing cycles drive up the overall production cost of AR glasses, resulting in high prices for end products and making it difficult to enter the mass consumer market. On the other hand, processing defects can severely affect the optical performance of waveguide sheets, leading to problems such as blurred images and reduced field of view, thus reducing the user experience. In summary, the core technical problem facing AR glasses waveguide sheets in the current technology is that silicon carbide waveguide sheets are extremely difficult to process, making it difficult to achieve efficient and low-cost mass production, which restricts the industrialization of AR glasses.

[0040] Therefore, this application optimizes the structure of the optical waveguide sheet and achieves a stable connection between the substrate layer 110 and the optical waveguide layer 130 (i.e., silicon carbide layer) through the design of the bonding elements of the transition layer 120, while ensuring the overall light transmittance and light conduction performance. The optical waveguide layer 130 adopts an ultra-thin coating method instead of traditional silicon carbide processing, which increases the processing difficulty of the optical waveguide sheet.

[0041] This application provides an optical waveguide structure, such as Figure 1 As shown, it includes: a substrate 110, which is a light-transmitting material; a transition layer 120, which is stacked on the substrate 110; and an optical waveguide layer 130, which is stacked on the transition layer 120. The substrate 110, transition layer 120, and optical waveguide layer 130 are all light-transmitting materials. The substrate 110 and optical waveguide layer 130 are connected through the transition layer 120, and the refractive index of the optical waveguide layer 130 is greater than that of the transition layer 120. The transition layer 120 includes at least one first bonding element bonded to the substrate 110 and at least one second bonding element bonded to the optical waveguide layer 130.

[0042] Specifically, such as Figure 1 As shown, the optical waveguide structure includes three core layers: a base layer 110, a transition layer 120, and an optical waveguide layer 130. The three layers are stacked tightly in sequence in the order of base layer 110, transition layer 120, and optical waveguide layer 130 to form a complete integrated structure. There are no obvious gaps between the layers, which ensures the tightness of the interlayer bonding and avoids scattering and leakage of virtual imaging light at the interlayer interface.

[0043] like Figure 1As shown, the substrate layer 110 serves as the supporting carrier for the entire optical waveguide structure. Its main function is to provide stable mechanical support, ensuring the overall morphological stability and mechanical strength of the optical waveguide structure, and preventing deformation or damage during processing, assembly, and use. The substrate layer 110 is made of a light-transmitting material. Since virtual imaging light needs to pass through the substrate layer 110 and the transition layer 120 to enter the optical waveguide layer 130, or in special application scenarios, ambient light needs to pass through the substrate layer 110, the transition layer 120, and the optical waveguide layer 130 to enter the human eye, the light transmittance of the substrate layer 110 directly affects the display effect of the AR glasses and the visibility of the real scene. The light transmittance of the substrate layer 110 must meet the requirements of AR display, typically not less than 90%. Simultaneously, the substrate layer 110 must also possess good chemical and thermal stability, adapting to the deposition process conditions of the transition layer 120 and the optical waveguide layer 130, and not undergoing oxidation, decomposition, or deformation under high temperature and high pressure conditions.

[0044] like Figure 1 As shown, the transition layer 120 is stacked on the upper surface of the substrate layer 110 and is closely attached to the substrate layer 110. It is used to achieve a stable connection between the substrate layer 110 and the optical waveguide layer 130, alleviate the lattice mismatch and thermal expansion coefficient difference between the substrate layer 110 and the optical waveguide layer 130, and at the same time achieve a smooth transition of refractive index, reducing the light loss of virtual imaging light at the interlayer interface. The transition layer 120 is also made of a light-transmitting material with a light transmittance of not less than 90%, ensuring that the virtual imaging light can smoothly pass through the transition layer 120 and enter the optical waveguide layer 130 without significant scattering and absorption.

[0045] The transition layer 120 contains at least one first bonding element and at least one second bonding element. The first bonding element can form a strong chemical bond with the substrate layer 110, specifically a metallic bond, an ionic bond, or a covalent bond. Through this strong chemical bond, the bonding strength between the transition layer 120 and the substrate layer 110 can be significantly improved, avoiding the problem of delamination between the transition layer 120 and the substrate layer 110. The selection of the first bonding element is closely related to the material of the substrate layer 110 and needs to be matched according to the main element type of the substrate layer 110. For example, when the substrate layer 110 is sapphire, its main elements are Al and O. In this case, the first bonding element can be Al or Ga, which can form a strong chemical bond with Al and O in sapphire. When the substrate layer 110 is a quartz single crystal, its main elements are Si and O. In this case, the first bonding element can be Si, which can form a strong chemical bond with Si and O in quartz single crystal.

[0046] The second bonding element can form a strong chemical bond with the optical waveguide layer 130, which can also be a metallic bond, ionic bond, or covalent bond. Through the effect of this strong chemical bond, the bonding strength between the transition layer 120 and the optical waveguide layer 130 is improved, ensuring that the optical waveguide layer 130 can be stably stacked on the transition layer 120 and avoiding the problem of the optical waveguide layer 130 falling off or peeling off. The selection of the second bonding element is closely related to the material of the optical waveguide layer 130 and needs to be matched according to the main element type of the optical waveguide layer 130. For example, when the optical waveguide layer 130 is silicon carbide, its main elements are Si and C. At this time, the second bonding element can be N, which can form a strong chemical bond with Si and C in silicon carbide. When the optical waveguide layer 130 is GaN, its main elements are Ga and N. At this time, the second bonding element can be N or Ga, which can form a strong chemical bond with Ga and N in GaN.

[0047] An optical waveguide layer 130 is stacked on the upper surface of the transition layer 120 and is closely fitted to the transition layer 120. It is used to achieve stable total internal reflection transmission of the virtual imaging light, guiding the coupled virtual imaging light to a designated location, and then coupling it out through the coupling unit 142 to the human eye to display virtual information. The optical waveguide layer 130 is made of a light-transmitting material; for example, its transmittance is not less than 90%, ensuring that the virtual imaging light does not experience significant absorption loss during transmission, thus guaranteeing imaging brightness and clarity.

[0048] The refractive index of the optical waveguide layer 130 is greater than that of the transition layer 120, which is the core condition for achieving stable total internal reflection propagation of virtual imaging light within the optical waveguide layer 130. According to the principle of total internal reflection, when light travels from an optically denser medium to an optically less dense medium, and the angle of incidence is greater than the critical angle, total internal reflection will occur, preventing the light from passing through the interface between the two media. In the optical waveguide structure of this invention, the optical waveguide layer 130 is an optically denser medium, and the transition layer 120 is an optically less dense medium. After the virtual imaging light enters the optical waveguide layer 130, total internal reflection occurs at the interface between the optical waveguide layer 130 and the transition layer 120, thereby achieving stable light propagation and avoiding light loss and imaging blurring caused by light leakage.

[0049] The aforementioned optical waveguide structure, through the setting of the first and second bonding elements in the transition layer 120, forms strong chemical bonds with the substrate layer 110 and the optical waveguide layer 130 respectively, significantly improving the interlayer bonding force and solving the problems of weak interlayer bonding force and easy peeling in the prior art. At the same time, the substrate layer 110, the transition layer 120 and the optical waveguide layer 130 are all made of light-transmitting materials, and the refractive index of the optical waveguide layer 130 is greater than that of the transition layer 120, ensuring smooth transmission and low loss of virtual imaging light.

[0050] Furthermore, in the transition layer 120, the content of the first bonding element gradually decreases along a first direction, while the content of the second bonding element gradually increases along the first direction, which is the direction from the substrate layer 110 to the optical waveguide layer 130. Thus, the transition layer 120 is further optimized by setting a composition gradient. Gradient control enables continuous variation in the content of the first and second bonding elements, further mitigating the lattice mismatch and thermal expansion coefficient difference between the substrate layer 110 and the optical waveguide layer 130, improving interlayer bonding, and simultaneously achieving a smooth transition of refractive index, reducing optical loss.

[0051] Specifically, the substrate layer 110, transition layer 120, and waveguide layer 130 of the optical waveguide structure are stacked sequentially, all of which are transparent materials. The refractive index of the waveguide layer 130 is greater than that of the transition layer 120. The transition layer 120 contains at least one first bonding element that forms a strong chemical bond with the substrate layer 110 and at least one second bonding element that forms a strong chemical bond with the waveguide layer 130. A further improvement is that the content of the first and second bonding elements in the transition layer 120 exhibits a continuous gradient change along a first direction, where the first direction is defined as the direction from the substrate layer 110 to the waveguide layer 130, that is, the direction extending from the side of the transition layer 120 near the substrate layer 110 to the side of the transition layer 120 near the waveguide layer 130.

[0052] The materials of the substrate layer 110 and the optical waveguide layer 130 typically have significant differences in lattice constant and thermal expansion coefficient. Even if the transition layer 120 contains bonding elements capable of forming strong chemical bonds with both, if the composition of the transition layer 120 is uniform, abrupt changes in composition, lattice, and refractive index will still occur at the interfaces between the substrate layer 110 and the transition layer 120, and between the transition layer 120 and the optical waveguide layer 130. This leads to stress concentration at the interfaces, affecting the interlayer bonding force. Simultaneously, the virtual imaging light will experience some scattering and reflection at the interfaces, increasing light loss. To solve this problem, this invention sets a composition gradient, allowing the composition of the transition layer 120 to gradually transition from the side closer to the substrate layer 110 to the side closer to the optical waveguide layer 130, achieving seamless connection with the substrate layer 110 and the optical waveguide layer 130.

[0053] Specifically, the content of the first bonding element gradually decreases along the first direction, while the content of the second bonding element gradually increases along the first direction. The first bonding element is mainly used to form strong chemical bonds with the substrate 110. Therefore, on the side of the transition layer 120 close to the substrate 110, the content of the first bonding element is higher, which can form a more stable bond with the substrate 110 and improve the bonding strength between the transition layer 120 and the substrate 110. As it extends towards the optical waveguide layer 130, the content of the first bonding element gradually decreases to adapt to the gradual transition of the composition of the transition layer 120. On the side of the transition layer 120 close to the optical waveguide layer 130, the content of the first bonding element is reduced to the minimum to avoid excessive first bonding elements affecting the bonding between the transition layer 120 and the optical waveguide layer 130.

[0054] The second bonding element is mainly used to form strong chemical bonds with the optical waveguide layer 130. Therefore, the content of the second bonding element is relatively high on the side of the transition layer 120 close to the optical waveguide layer 130, which can form a more stable bond with the optical waveguide layer 130 and improve the bonding strength between the transition layer 120 and the optical waveguide layer 130. As it extends towards the substrate layer 110, the content of the second bonding element gradually decreases to adapt to the gradual transition of the composition of the transition layer 120. On the side of the transition layer 120 close to the substrate layer 110, the content of the second bonding element is reduced to the minimum to avoid excessive second bonding elements affecting the bonding between the transition layer 120 and the substrate layer 110.

[0055] The content changes of the first and second bonding elements are continuous and smooth, without abrupt changes. This continuous gradient change enables a smooth transition of the refractive index of the transition layer 120, allowing the refractive index of the substrate layer 110 to gradually transition to the refractive index of the optical waveguide layer 130 through the transition layer 120, avoiding light scattering and optical loss caused by abrupt changes in refractive index. Simultaneously, the continuous compositional gradient also alleviates the lattice mismatch and thermal expansion coefficient difference between the substrate layer 110 and the optical waveguide layer 130, disperses interfacial stress, and avoids problems such as interlayer delamination and cracking caused by stress concentration, further improving the overall stability and mechanical strength of the optical waveguide structure.

[0056] For example, when the substrate 110 is sapphire and the waveguide layer 130 is silicon carbide, the first bonding element in the transition layer 120 is Al and the second bonding element is N. Along the first direction, the content of Al gradually decreases and the content of N gradually increases. On the side of the transition layer 120 near the sapphire substrate 110, the content of Al is the highest, which can form strong chemical bonds with Al and O in sapphire and improve the bonding strength. On the side of the transition layer 120 near the silicon carbide waveguide layer 130, the content of N is the highest, which can form strong chemical bonds with Si and C in silicon carbide and improve the bonding strength. The content of Al and N in the middle region transitions continuously, achieving a smooth change in refractive index and reducing optical loss.

[0057] In one embodiment, the optical waveguide layer 130 is silicon carbide; the thickness of the optical waveguide layer 130 is 400–600 nm.

[0058] The advantages of silicon carbide materials are: First, high refractive index. The refractive index of silicon carbide is typically around 2.6, far higher than most transition layer 120 materials and substrate layer 110 materials. This allows it to meet the total internal reflection condition where the refractive index of the waveguide layer 130 is greater than that of the transition layer 120, achieving stable total internal reflection transmission of virtual imaging light and avoiding light leakage. Second, good light transmittance. Silicon carbide materials have high transmittance in the visible and near-infrared bands, reaching over 92%, ensuring that the virtual imaging light does not experience significant absorption loss during transmission, guaranteeing imaging brightness and clarity. Third, good mechanical properties. Excellent properties: Silicon carbide has high hardness and toughness, which can withstand mechanical stress during processing, assembly and use, avoiding problems such as deformation and breakage; Fourth, good chemical and thermal stability: Silicon carbide does not oxidize, decompose or degrade in harsh environments such as high temperature, high pressure and humidity, and can adapt to the deposition process conditions of transition layer 120, while extending the service life of optical waveguide structure; Fifth, it can be made into ultra-thin layers: Silicon carbide material can be made into ultra-thin layers with a thickness of only a few hundred nanometers through epitaxial growth and other processes, meeting the development trend of lightweight and thin AR glasses.

[0059] Based on the material properties of the silicon carbide waveguide layer 130, the first and second bonding elements of the transition layer 120 need to be specifically selected to ensure that the transition layer 120 can form strong chemical bonds with the substrate layer 110 and the silicon carbide waveguide layer 130. Since the main elements of silicon carbide are Si and C, the second bonding element must be selected from elements that can form strong chemical bonds with Si and C, with nitrogen (N) being the preferred choice. Nitrogen (N) can form Si-N covalent bonds with Si and CN covalent bonds with C, resulting in high bonding strength and effectively improving the bonding strength between the transition layer 120 and the silicon carbide waveguide layer 130. The first bonding element is selected based on the material of the substrate layer 110 to ensure that it can form strong chemical bonds with the substrate layer 110. For example, when the substrate layer 110 is sapphire, the first bonding element is Al; when the substrate layer 110 is a single crystal quartz, the first bonding element is Si.

[0060] The gradient setting of the transition layer 120 is adapted to the silicon carbide optical waveguide layer 130. Along the first direction, the content of the first bonding element gradually decreases, while the content of the second bonding element (N) gradually increases. On the side of the transition layer 120 close to the silicon carbide optical waveguide layer 130, the content of the N element reaches its maximum, enabling it to form a more stable bond with Si and C in silicon carbide. Simultaneously, it achieves a smooth transition of the refractive index of the transition layer 120 to that of silicon carbide, reducing optical loss. For example, when the substrate layer 110 is a quartz single crystal and the transition layer 120 is Si3N4, the first bonding element is Si, and the second bonding element is N. Along the first direction, the content of the Si element gradually increases, while the content of the N element gradually decreases until the atomic ratio of Si3N4 reaches 3:4. This ensures both a stable bond between the transition layer 120 and the quartz single crystal substrate layer 110 and a good connection with the silicon carbide optical waveguide layer 130.

[0061] Furthermore, the thickness of the silicon carbide optical waveguide layer 130 is limited to 400–600 nm. Within this thickness range, lightweight design, good optical and mechanical properties, and high process feasibility can be achieved simultaneously. Specifically, a thickness of 400–600 nm ensures a thinner optical waveguide structure, meeting the wearing requirements of AR glasses. Compared to existing optical waveguide layers 130 that are hundreds of micrometers or even millimeters thick, the weight is significantly reduced. At the same time, this thickness provides a sufficient transmission path for virtual imaging light, ensuring stable total internal reflection transmission of virtual imaging light within the silicon carbide optical waveguide layer 130, avoiding light leakage, and guaranteeing imaging brightness and clarity. In addition, this thickness range is compatible with the capabilities of existing epitaxial growth processes, allowing for precise fabrication using processes such as low-pressure chemical vapor deposition and plasma-enhanced chemical vapor deposition, ensuring the thickness uniformity and crystal quality of the silicon carbide optical waveguide layer 130, and improving product yield.

[0062] In this embodiment, the optimal thickness of the silicon carbide waveguide layer 130 is 500 nm. This thickness achieves the best balance between lightweight design and optical performance, ensuring both a thinner waveguide structure and stable total internal reflection transmission of virtual imaging light. It also effectively reduces light loss and improves imaging clarity. Furthermore, the 500 nm thickness better matches the gradient setting of the transition layer 120, which typically has a thickness between 200 and 300 nm. This reasonable thickness ratio further alleviates interlayer stress, enhances interlayer bonding, and prevents interlayer delamination. During actual fabrication, the thickness of the silicon carbide waveguide layer 130 can be fine-tuned according to specific application requirements. For example, in scenarios with high lightweight requirements, the thickness can be adjusted to 400–450 nm; in scenarios with high optical performance requirements and relatively low lightweight requirements, the thickness can be adjusted to 550–600 nm. However, regardless of the adjustment, it must be controlled within the range of 400–600 nm to ensure that the core performance of the waveguide structure is not affected.

[0063] In one embodiment, the base layer 110 is sapphire, and the transition layer 120 is made of XN, where X is Al or Ga.

[0064] Specifically, the material of the substrate layer 110 needs to possess good light transmittance, mechanical strength, chemical stability, and thermal stability, while also forming a good bond with the transition layer 120. Sapphire is a high-quality light-transmitting material with a light transmittance of over 90% in the visible and near-infrared bands, meeting the light transmittance requirements of AR displays. Simultaneously, sapphire possesses extremely high hardness and good toughness, exhibiting excellent mechanical strength, providing stable mechanical support for the optical waveguide structure and preventing deformation and breakage. Sapphire also boasts excellent chemical and thermal stability, remaining unaffected by oxidation, decomposition, or performance degradation under harsh environments such as high temperature, high pressure, and humidity. This allows it to adapt to the deposition process conditions of the transition layer 120 and the silicon carbide optical waveguide layer 130, especially withstanding the high-temperature environment of the MOCVD process, ensuring the precise deposition of the transition layer 120.

[0065] Furthermore, the main elements of sapphire are Al and O, which can form strong chemical bonds with the X element (Al or Ga) in the transition layer 120XN. Al and O can form Al-O ionic bonds, and Ga and O can form Ga-O ionic bonds. The high bonding strength can significantly improve the bonding strength between the transition layer 120 and the substrate layer 110, avoiding the problem of delamination between the transition layer 120 and the substrate layer 110. At the same time, the lattice constant of sapphire is relatively close to that of the XN transition layer 120, which can alleviate the lattice mismatch between the transition layer 120 and the substrate layer 110, reduce interfacial stress, and further improve the interlayer bonding and the overall stability of the optical waveguide structure.

[0066] The transition layer 120 needs to form strong chemical bonds with both the sapphire substrate 110 and the silicon carbide waveguide layer 130, while simultaneously achieving a smooth transition in refractive index and reducing optical loss. In XN, X is Al or Ga, and N is nitrogen. X acts as the first bonding element, forming strong chemical bonds with Al and O in the sapphire substrate 110. Al can form Al-O ionic bonds with O, and Ga can form Ga-O ionic bonds with O, ensuring a stable connection between the transition layer 120 and the sapphire substrate 110. N acts as the second bonding element, forming strong chemical bonds with Si and C in the silicon carbide waveguide layer 130, forming Si-N covalent bonds and CN covalent bonds, ensuring a stable connection between the transition layer 120 and the silicon carbide waveguide layer 130.

[0067] When X is Al, the transition layer 120 is AlN (aluminum nitride). AlN has good light transmittance, with a transmittance of not less than 90%, and a refractive index between 1.9 and 2.1, which is between that of sapphire (refractive index approximately 1.77) and silicon carbide (refractive index approximately 2.6). This allows for a smooth transition in refractive index, reducing light loss at the interlayer interface for virtual imaging. Simultaneously, the lattice constant of AlN is relatively close to that of sapphire and silicon carbide, effectively mitigating lattice mismatch, reducing interfacial stress, and improving interlayer bonding and the overall stability of the optical waveguide structure. AlN also exhibits good thermal and chemical stability, enabling it to withstand high-temperature deposition processes without oxidation or decomposition at high temperatures, ensuring the stable performance of the transition layer 120.

[0068] When X is Ga, the transition layer 120 is GaN (gallium nitride). GaN also has good light transmittance, with a transmittance of not less than 90% and a refractive index between 2.2 and 2.4, which is between sapphire and silicon carbide. This allows for a smooth transition in refractive index and reduces light loss. GaN has excellent mechanical properties and chemical stability, enabling it to form strong chemical bonds with the sapphire substrate layer 110 and the silicon carbide waveguide layer 130. At the same time, GaN has good crystal quality and fewer defects, which can further improve the performance of the transition layer 120 and ensure smooth transmission of virtual imaging light.

[0069] The gradient setting of the transition layer 120XN is adapted to the sapphire substrate 110 and the silicon carbide waveguide layer 130. Along the first direction, the content of element X (Al or Ga) gradually decreases, while the content of element N gradually increases, achieving a continuous transition in composition. On the side of the transition layer 120 near the sapphire substrate 110, the content of element X is higher, which can form a more stable bond with Al and O in the sapphire, improving the bonding strength between the transition layer 120 and the substrate 110. On the side of the transition layer 120 near the silicon carbide waveguide layer 130, the content of element N is higher, which can form a more stable bond with Si and C in the silicon carbide, improving the bonding strength between the transition layer 120 and the waveguide layer 130. The continuous transition of element X and element N in the middle region achieves a smooth change in refractive index and reduces optical loss.

[0070] Furthermore, in the transition layer 120, the X content gradually decreases along the first direction, and the N content gradually increases along the first direction until the atomic ratio of X to N is 1:1, wherein the first direction is the direction from the substrate layer 110 to the optical waveguide layer 130.

[0071] The core function of the XN transition layer 120 is to achieve a stable connection and smooth refractive index transition between the sapphire substrate layer 110 and the silicon carbide waveguide layer 130. The compositional uniformity and stoichiometric balance of the transition layer 120 directly affect its performance. When the atomic ratio of X to N reaches 1:1, the XN transition layer 120 achieves stoichiometric balance. At this point, the transition layer 120 has the best crystal quality, the fewest defects, and the best light transmittance and mechanical properties, enabling a smoother refractive index transition and reducing optical loss.

[0072] Meanwhile, the XN transition layer 120 with an X:N atom ratio of 1:1 can form a more robust bond with the silicon carbide waveguide layer 130. The silicon carbide waveguide layer 130 has a uniform composition and fewer defects. When the transition layer 120 reaches an X:N ratio of 1:1 near the waveguide layer 130, the compositional matching between the transition layer 120 and the waveguide layer 130 is highest, resulting in the lowest interfacial stress and the strongest bonding strength, effectively preventing problems such as interlayer delamination and cracking. Furthermore, the XN transition layer 120 with an X:N ratio of 1:1 has the most stable lattice constant, achieving optimal matching with the lattice constants of the sapphire substrate layer 110 and the silicon carbide waveguide layer 130, further mitigating lattice mismatch and improving the overall stability of the waveguide structure.

[0073] Taking Al as an example, when the transition layer 120 is AlN, the Al content is higher and the N content is lower on the side of the transition layer 120 near the sapphire substrate 110. At this time, the atomic ratio of Al to N is greater than 1:1, for example, 1.5:1, which can ensure that Al and O in the sapphire form enough Al-O ionic bonds, thereby improving the bonding strength between the transition layer 120 and the substrate 110. As it extends towards the silicon carbide optical waveguide layer 130, the Al content gradually decreases and the N content gradually increases, with the atomic ratio gradually decreasing, at 1.4:1, 1.3:1, and 1.2:1 respectively. On the side of the transition layer 120 near the silicon carbide optical waveguide layer 130, the Al content decreases to be equal to the N content, and the atomic ratio reaches 1:1. At this time, the AlN transition layer 120 reaches a stoichiometric equilibrium state, has the best crystal quality, and can form a stable bond with the silicon carbide optical waveguide layer 130, while achieving a smooth transition of refractive index.

[0074] This continuous gradient change process ensures that the composition of the transition layer 120 gradually transitions from the X-rich state near the substrate layer 110 to the stoichiometric equilibrium state near the optical waveguide layer 130. This not only guarantees a stable connection between the transition layer 120 and the substrate layer 110, but also achieves a perfect connection with the optical waveguide layer 130. At the same time, the continuous composition change enables a smooth transition of the refractive index, avoiding light scattering and light loss caused by abrupt changes in refractive index, ensuring smooth transmission of virtual imaging light, and improving imaging brightness and clarity.

[0075] When X is Ga, i.e. when the transition layer 120 is GaN, the gradient change process is similar to that of the AlN transition layer 120: on the side of the transition layer 120 near the sapphire substrate 110, the content of Ga element is higher and the content of N element is lower, and the Ga:N atomic ratio is greater than 1:1; along the first direction, the content of Ga element gradually decreases and the content of N element gradually increases, and the atomic ratio gradually decreases until the side of the transition layer 120 near the silicon carbide optical waveguide layer 130, where the Ga:N atomic ratio reaches 1:1, realizing the stoichiometric balance of the GaN transition layer 120 and improving the performance and interlayer bonding of the transition layer 120.

[0076] It should be noted that an atomic ratio of X to N of 1:1 is an ideal gradient endpoint. In actual preparation, due to factors such as process errors, slight deviations are allowed. For example, atomic ratios in the range of 0.95:1 to 1.05:1 are all within the scope of protection of this invention. Such slight deviations will not affect the core performance of the transition layer 120 and can still achieve a stable connection between the substrate layer 110 and the optical waveguide layer 130 and a smooth transition of refractive index.

[0077] Thus, by defining the gradient endpoint of the XN transition layer 120 as an X to N atomic ratio of 1:1, the gradient setting of the transition layer 120 is further optimized, improving the crystal quality, light transmittance, and mechanical properties of the transition layer 120. This ensures a stable connection and smooth refractive index transition between the transition layer 120 and the sapphire substrate layer 110 and the silicon carbide optical waveguide layer 130, reducing optical loss and interface stress, and making the performance of the optical waveguide structure more stable and superior.

[0078] In another embodiment, the substrate 110 is sapphire, and the transition layer 120 is made of Al. i Ga (1-i) N, where i∈(0,1).

[0079] A ternary solid solution composed of AlN and GaN, where i is the mole fraction of AlN and (1-i) is the mole fraction of GaN, and the value of i ranges from (0,1). By adjusting the value of i, the mole fraction of AlN can be flexibly controlled. i Ga (1-i) The refractive index and lattice constant of the N transition layer 120 enable it to achieve optimal matching with the sapphire substrate layer 110 and the silicon carbide optical waveguide layer 130, further alleviating lattice mismatch, reducing interfacial stress, and improving interlayer bonding.

[0080] Specifically, Al i Ga (1-i) The refractive index of the N ternary solid solution increases as the value of i decreases. When i=1, the transition layer 120 is AlN with a refractive index of approximately 1.9 to 2.1. When i=0, the transition layer 120 is GaN with a refractive index of approximately 2.2 to 2.4. When i is between (0,1), the refractive index of the transition layer 120 is between 1.9 and 2.4, which can flexibly adapt to the refractive index transition requirements between the sapphire substrate layer 110 (refractive index of approximately 1.77) and the silicon carbide optical waveguide layer 130 (refractive index of approximately 2.6), achieving a smooth transition of refractive index and reducing optical loss.

[0081] Meanwhile, Al i Ga (1-i) The lattice constant of the N-ternary solid solution also changes continuously with the value of i. By adjusting the value of i, the lattice constant of the transition layer 120 can be optimally matched with the lattice constants of the sapphire substrate layer 110 and the silicon carbide waveguide layer 130, thereby maximally mitigating lattice mismatch, reducing interfacial stress, and improving interlayer bonding and the overall stability of the waveguide structure. For example, when the lattice constants of the sapphire substrate layer 110 and the silicon carbide waveguide layer 130 differ significantly, the value of i can be adjusted to make Al i Ga (1-i) The lattice constant of the N transition layer 120 is between the two, achieving a smooth lattice transition.

[0082] Al i Ga (1-i) In the N-ternary solid solution, Al and Ga elements act as the first bonding elements, forming strong chemical bonds with O elements in the sapphire substrate 110. Al forms Al-O ionic bonds with O, and Ga forms Ga-O ionic bonds with O, ensuring a stable connection between the transition layer 120 and the sapphire substrate 110. N element acts as the second bonding element, forming strong chemical bonds with Si and C in the silicon carbide optical waveguide layer 130, forming Si-N covalent bonds and CN covalent bonds, ensuring a stable connection between the transition layer 120 and the silicon carbide optical waveguide layer 130.

[0083] Furthermore, in the transition layer 120, i gradually decreases along a first direction, wherein the first direction is the direction from the substrate layer 110 to the optical waveguide layer 130.

[0084] On the side of the transition layer 120 near the sapphire substrate 110, the i value is set to a relatively large value, typically between 0.9 and 1.0. At this point, the molar fraction of AlN in the transition layer 120 is relatively high, while the molar fraction of GaN is relatively low. The refractive index of the transition layer 120 is approximately 1.9–2.1, and the lattice constant is approximately 4.38–4.50 Å. The difference between the refractive index (1.77) and lattice constant (4.76 Å) of the transition layer 120 and the sapphire substrate 110 is relatively small. This allows the transition layer to form a stable bond with the sapphire substrate 110, while simultaneously achieving an initial transition in refractive index and lattice constant, thus reducing interfacial stress.

[0085] As the silicon carbide optical waveguide layer 130 extends along the first direction, the value of i gradually decreases, decreasing from 0.9 to 1.0 to 0.0 to 0.1. The mole fraction of AlN in the transition layer 120 gradually decreases, while the mole fraction of GaN gradually increases. The refractive index of the transition layer 120 also gradually increases, from 1.9 to 2.1 to 2.2 to 2.4. The lattice constant gradually decreases, from 4.38 to 4.50 Å to 4.36 to 4.50 Å. On the side of the transition layer 120 near the silicon carbide optical waveguide layer 130, the i value drops to 0.0–0.1. At this point, the molar fraction of GaN in the transition layer 120 is relatively high, while the molar fraction of AlN is relatively low. The refractive index of the transition layer 120 is approximately 2.2–2.4, and the lattice constant is approximately 4.36–4.50 Å. The difference between the refractive index (2.6) and lattice constant (4.36 Å) of the transition layer 120 and those of the silicon carbide optical waveguide layer 130 is relatively small. This allows the transition layer to form a stable bond with the silicon carbide optical waveguide layer 130, thus achieving the final transition in refractive index and lattice constant.

[0086] The continuous gradient change of the i-value ensures a smooth transition in the composition, refractive index, and lattice constant of the transition layer 120, without abrupt changes. This effectively disperses interfacial stress, preventing problems such as interlayer delamination and cracking caused by stress concentration, and significantly improves the bonding strength between the transition layer 120 and the sapphire substrate 110, and between the transition layer 120 and the silicon carbide waveguide layer 130. Simultaneously, the continuous smooth transition in refractive index effectively reduces the scattering and reflection losses of virtual imaging light at the interlayer interfaces, ensuring that virtual imaging light can smoothly enter the silicon carbide waveguide layer 130 from the transition layer 120, achieving stable total internal reflection propagation.

[0087] For example, when the value of i gradually decreases from 0.9 to 0.1, the refractive index of the transition layer 120 gradually increases from 2.0 to 2.3, and the lattice constant gradually decreases from 4.45 Å to 4.40 Å, which just achieves a smooth transition from the sapphire substrate layer 110 (refractive index 1.77, lattice constant 4.76 Å) to the silicon carbide optical waveguide layer 130 (refractive index 2.6, lattice constant 4.36 Å), minimizing interface stress, optimizing interlayer bonding, and minimizing optical loss.

[0088] It should be noted that the specific range of the i value can be fine-tuned according to actual application requirements and process conditions. As long as the i value gradually decreases along the first direction and i∈(0,1), it falls within the protection scope of this invention. At the same time, the rate of change of the i value can also be adjusted according to actual needs. Usually, a uniform decreasing method is adopted to ensure that the performance of the transition layer 120 is uniform and stable, and to avoid the problem of local performance abrupt changes.

[0089] In another embodiment, the transition layer 120 employs an XN layer and an Al layer. i Ga (1-i) The N-layer structure: an XN layer (where X is any one of Al, Si, or Ti) is positioned close to the substrate layer 110, Al i Ga (1-i) N is superimposed on the side of the XN layer away from the substrate 110. The dual gradient transition further alleviates lattice mismatch and enhances interlayer bonding. The gradient adjustment core follows the principle of continuous adaptation and smooth transition. The total thickness of the transition layer 120 is 50-200nm. The XN layer and Al i Ga (1-i) The thickness ratio of the N layer is 3:7 to 5:5; the X content gradually decreases along the first direction (from substrate 110 to waveguide layer 130), with the X content of the XN layer being 90%-95% on the side closer to substrate 110 and decreasing closer to Al. i Ga (1-i) The N-layer side decreases to 50%-60%; the i value changes synchronously and gradually, Al i Ga (1-i)The i-value of the N layer near the XN layer is 0.6-0.8, matching the X content of the XN layer, and decreases to 0.1-0.3 near the optical waveguide layer 130, adapting to the parameters of the optical waveguide layer 130. For example, the XN layer is AlN (50nm thick), with the Al content decreasing from 92% to 55%; Al... i Ga (1-i) The N layer (70nm thick) has an i-value that gradually changes from 0.7 to 0.2, with a total thickness of 120nm. The X content and i-value change gradually, achieving a continuous transition in refractive index and lattice constant, avoiding abrupt interface changes, further reducing optical loss, and adapting to the performance requirements of high-end optical waveguides.

[0090] In other embodiments, the substrate 110 may be made of other materials, and the optical waveguide may be made of silicon carbide.

[0091] For example, the substrate layer 110 is a single crystal quartz, the optical waveguide layer 130 is silicon carbide, and the transition layer 120 is made of Si3N4 or AlN-SiO. x N y Composite layer; wherein, in the first direction of the transition layer 120, the Si element content in the Si3N4 layer gradually increases, and the N element content gradually decreases to an atomic ratio of 3:4; AlN-SiO x N y The proportion of AlN in the composite layer gradually increases, AlN-SiO x N y The proportion gradually decreases, and the Al content of AlN gradually decreases while the N content gradually increases to an atomic ratio of 1:1; the first direction is from the substrate layer 110 to the optical waveguide layer 130; When the transition layer 120 is Si3N4, the Si element in Si3N4 acts as the first bonding element, forming strong chemical bonds with the Si and O elements in the quartz single-crystal substrate 110. Si and O form Si-O covalent bonds, ensuring a stable connection between the transition layer 120 and the quartz single-crystal substrate 110. The N element acts as the second bonding element, forming strong chemical bonds with the Si and C elements in the silicon carbide optical waveguide layer 130, forming Si-N and CN covalent bonds, ensuring a stable connection between the transition layer 120 and the silicon carbide optical waveguide layer 130. Along the first direction, the atomic ratio of Si to N elements in the Si3N4 layer gradually decreases until it reaches 3:4. Since the ideal atomic ratio of Si3N4 corresponds to 3:4, at this point, the crystal quality of Si3N4 is the best, with the fewest defects, and the optimal light transmittance and mechanical properties. On the side of the transition layer 120 near the quartz single-crystal substrate 110, the Si content is higher and the N content is lower, with an atomic ratio of Si to N greater than 3:4. This ensures that Si forms a sufficient number of Si-O covalent bonds with the O element in the quartz single crystal, enhancing the bonding strength between the transition layer 120 and the substrate 110. As it extends towards the silicon carbide optical waveguide layer 130, the Si content gradually decreases, the N content gradually increases, and the atomic ratio of Si to N gradually decreases until the side of the transition layer 120 near the silicon carbide optical waveguide layer 130 reaches an atomic ratio of Si to N of 3:4. This achieves stoichiometric equilibrium of the Si3N4 transition layer 120, enabling it to form a stable bond with the silicon carbide optical waveguide layer 130 and simultaneously achieving a smooth transition of refractive index.

[0092] When the transition layer 120 is AlN-SiO x N y When composite layers are used, AlN-SiO x N y It possesses good light transmittance and compatibility with quartz single crystals, with a refractive index of approximately 1.5–1.8. The composite of the two allows for better adaptation to the quartz single crystal substrate 110 and the silicon carbide optical waveguide layer 130. Along the first direction, the proportion of AlN gradually increases, while SiO... x N y The proportion of Al gradually decreases, achieving a continuous transition in composition. In the AlN portion, the content of Al gradually decreases, while the content of N gradually increases until the atomic ratio of Al to N reaches 1:1, ensuring optimal crystal quality and performance of the AlN portion. On the side of the transition layer 120 near the quartz single-crystal substrate 110, SiO... x N y The proportion of AlN is relatively high, while that of SiO is relatively low. x N yThe Si element in the substrate can form strong chemical bonds with Si and O in the quartz single crystal, enhancing the bonding strength between the transition layer 120 and the substrate 110. As it extends towards the silicon carbide optical waveguide layer 130, the proportion of AlN gradually increases, and the proportion of SiO... x N y The proportion of nitrogen in AlN gradually decreases, and the nitrogen element in AlN can form strong chemical bonds with Si and C in silicon carbide, thereby improving the bonding strength between the transition layer 120 and the optical waveguide layer 130. At the same time, the ratio of Al to N atoms in the AlN part transitions to 1:1, ensuring the crystal quality of the AlN part, achieving a smooth transition of refractive index, and reducing optical loss.

[0093] For example, the substrate 110 is a single crystal of magnesium oxide, the optical waveguide layer 130 is silicon carbide, and the transition layer 120 is made of MgAl2O4 or a MgAl2O4-AlN composite layer; wherein, in the first direction of the transition layer 120, the proportion of MgAl2O4 in the MgAl2O4-AlN composite layer gradually decreases, the proportion of AlN gradually increases, and the Al content of AlN gradually decreases and the N content gradually increases until the atomic ratio of Al to N is 1:1; the first direction is the direction from the substrate 110 to the optical waveguide layer 130; When the transition layer 120 is MgAl2O4, the Al element in MgAl2O4 acts as the first bonding element and can form Al-O ionic bonds with the O element in the magnesium oxide single crystal, ensuring a stable connection between the transition layer 120 and the substrate layer 110. The O element in MgAl2O4 can form Si-O covalent bonds with the Si in silicon carbide, playing an auxiliary bonding role and improving the bonding strength between the transition layer 120 and the optical waveguide layer 130.

[0094] When the transition layer 120 is a MgAl2O4-AlN composite layer, this composite layer combines the compatibility of MgAl2O4 with magnesium oxide single crystals and the compatibility of AlN with silicon carbide, enabling better integration between the two. Specifically, the gradient setting of the transition layer 120 is as follows: along the first direction, the proportion of MgAl2O4 gradually decreases, while the proportion of AlN gradually increases, achieving a continuous transition of composition; simultaneously, the content of Al in the AlN portion gradually decreases, while the content of N gradually increases, until the atomic ratio of Al to N reaches 1:1, ensuring optimal crystal quality and performance of the AlN portion. On the side of the transition layer 120 near the magnesium oxide single crystal substrate 110, the proportion of MgAl2O4 is relatively high and the proportion of AlN is relatively low. The Al element in MgAl2O4 can form strong chemical bonds with the O element in the magnesium oxide single crystal, thereby improving the bonding strength between the transition layer 120 and the substrate 110. As it extends towards the silicon carbide optical waveguide layer 130, the proportion of MgAl2O4 gradually decreases and the proportion of AlN gradually increases. The N element in AlN can form strong chemical bonds with the Si and C in silicon carbide, thereby improving the bonding strength between the transition layer 120 and the optical waveguide layer 130. The Al to N atomic ratio in the AlN part transitions to 1:1, ensuring the crystal quality of the AlN part, achieving a smooth transition of refractive index, and reducing optical loss.

[0095] For example, the substrate 110 is high-alumina-silicon optical glass, the optical waveguide layer 130 is silicon carbide, and the transition layer 120 is made of amorphous AlO. x N y or SiO x N y In the first direction of the transition layer 120, AlO x N y In the layer, the oxygen content of Al gradually decreases while the nitrogen content gradually increases, and the SiO content gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is from the substrate layer 110 to the optical waveguide layer 130. When the transition layer 120 is amorphous AlO x N y At that time, AlO x N y The light transmittance is not less than 90%, and the refractive index can be adjusted by the oxygen and nitrogen content of Al, ranging from approximately 1.6 to 2.0, which is between that of high-alumina-silicon optical glass (1.52 to 1.58) and silicon carbide (2.6). The gradient setting of the transition layer 120 is specifically as follows: along the first direction, the oxygen content of Al gradually decreases, and the nitrogen content gradually increases, thereby achieving a gradual increase in refractive index and a continuous transition of composition.

[0096] On the side of the transition layer 120 near the high-alumina-silicon optical glass substrate 110, the oxygen content of Al is relatively high and the nitrogen content is relatively low. The Al-O bond formed by the combination of Al and oxygen can form strong chemical bonds with Al and O in the high-alumina-silicon optical glass, improving the bonding strength between the transition layer 120 and the substrate 110. At this time, the refractive index of the transition layer 120 is low, close to the refractive index of the high-alumina-silicon optical glass, achieving an initial transition in refractive index. As it extends towards the silicon carbide optical waveguide layer 130, the oxygen content of Al gradually decreases and the nitrogen content gradually increases. The Al-N bond formed by the combination of Al and nitrogen can form strong chemical bonds with Si and C in silicon carbide, improving the bonding strength between the transition layer 120 and the optical waveguide layer 130. At the same time, the refractive index of the transition layer 120 gradually increases, gradually approaching the refractive index of silicon carbide, achieving a smooth transition in refractive index and reducing optical loss.

[0097] When the transition layer 120 is SiO x N y At that time, SiO x N y The transmittance is not less than 90%, and the refractive index can be adjusted by the oxygen and nitrogen content of Si, ranging from approximately 1.55 to 1.9, which is between that of high-alumina-silicon optical glass (1.52 to 1.58) and silicon carbide (2.6). Along the first direction, the oxygen content of Si gradually decreases, while the nitrogen content gradually increases, achieving a gradual increase in refractive index and a continuous transition in composition.

[0098] Near the substrate 110, Si has a high oxygen content, and Si-O bonds form strong chemical bonds with Si and O in the high-alumina-silicon optical glass, with a refractive index close to that of the substrate 110. Near the optical waveguide layer 130, Si has a high nitrogen content, and Si-N bonds form strong chemical bonds with Si and C in silicon carbide, with a refractive index close to that of the optical waveguide layer 130. The middle region has a continuous transition, achieving low optical loss and high bonding strength.

[0099] For example, the substrate layer 110 is borosilicate glass, the optical waveguide layer 130 is silicon carbide, and the transition layer 120 is an amorphous SiO2-TiO2 composite layer or SiO2. x N y In the first direction of the transition layer 120, the proportion of TiO2 in the SiO2-TiO2 composite layer gradually increases, while the proportion of SiO2 gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is from the substrate layer 110 to the optical waveguide layer 130. When the transition layer 120 is an amorphous SiO2-TiO2 composite layer, the refractive index of SiO2 is approximately 1.46, and the refractive index of TiO2 is approximately 2.5. The refractive index of the composite can be controlled by adjusting the proportion of TiO2 and SiO2, ranging from approximately 1.46 to 2.5, which perfectly meets the refractive index transition requirements between borosilicate glass (1.47-1.52) and silicon carbide (2.6). The gradient setting of the transition layer 120 is specifically as follows: along the first direction, the proportion of TiO2 gradually increases, and the proportion of SiO2 gradually decreases, achieving a gradual increase in refractive index and a continuous transition of composition.

[0100] On the side of the transition layer 120 near the borosilicate glass substrate 110, the proportion of SiO2 is relatively high, while the proportion of TiO2 is relatively low. The Si element in SiO2 can form strong chemical bonds with the Si and O elements in the borosilicate glass, enhancing the bonding strength between the transition layer 120 and the substrate 110. At this point, the refractive index of the transition layer 120 is low, close to that of the borosilicate glass, achieving an initial transition in refractive index. As it extends towards the silicon carbide optical waveguide layer 130, the proportion of TiO2 gradually increases, while the proportion of SiO2 gradually decreases. The Ti element in TiO2 can form strong chemical bonds with the C elements in silicon carbide, enhancing the bonding strength between the transition layer 120 and the optical waveguide layer 130. Simultaneously, the refractive index of the transition layer 120 gradually increases, gradually approaching that of silicon carbide, achieving a smooth transition in refractive index and reducing optical loss. Furthermore, the addition of TiO2 can also improve the mechanical strength and wear resistance of the transition layer 120, extending the service life of the optical waveguide structure.

[0101] When the transition layer 120 is SiO x N y At that time, its gradient setting is similar to that of SiO in the third combination. x N y The transition layer 120 is consistent, that is, along the first direction, the oxygen content of Si gradually decreases and the nitrogen content gradually increases, so as to achieve a gradual increase in refractive index and a continuous transition of composition, ensuring a stable connection between the transition layer 120 and the borosilicate glass substrate layer 110 and the silicon carbide optical waveguide layer 130, and reducing optical loss.

[0102] In other embodiments, the substrate 110 may also be made of other materials, and the optical waveguide may be made of non-silicon carbide material.

[0103] For example, the substrate 110 is sapphire, the waveguide layer 130 is GaN, and the transition layer 120 is made of Al. i Ga (1-i) N; wherein, in the first direction of the transition layer 120, the value of i gradually decreases, and the atomic ratio of Al / Ga to N gradually transitions to 1:1; the first direction is the direction from the substrate layer 110 to the optical waveguide layer 130; Transition layer 120 selects Al i Ga (1-i) N-ternary solid solution, Al i Ga (1-i) Al and Ga elements in N, as the first bonding elements, can form strong chemical bonds with O elements in sapphire substrate 110, ensuring a stable connection between transition layer 120 and substrate 110; N element, as the second bonding element, can form strong chemical bonds with Ga and N in GaN optical waveguide layer 130, ensuring a stable connection between transition layer 120 and optical waveguide layer 130.

[0104] Along the first direction, the value of i gradually decreases, and the atomic ratio of Al / Ga to N gradually transitions to 1:1; the value of i is the mole fraction of AlN, and (1-i) is the mole fraction of GaN. The decrease of the value of i means that the mole fraction of AlN decreases and the mole fraction of GaN increases. The refractive index and lattice constant of the transition layer 120 change accordingly, realizing a smooth transition from the sapphire substrate layer 110 to the GaN optical waveguide layer 130.

[0105] For example, the substrate layer 110 is quartz glass, the optical waveguide layer 130 is TiO2, and the transition layer 120 is made of Si3N4 or TiO2. x N y In the first direction of the transition layer 120, the atomic ratio of Si to N elements in the Si3N4 layer gradually decreases until it reaches 3:4; TiO x N y The oxygen content of Ti in the layer gradually decreases while the nitrogen content gradually increases until the atomic ratio of Ti to O is 1:2; the first direction is from the substrate layer 110 to the optical waveguide layer 130. When the transition layer 120 is Si3N4, the transmittance of Si3N4 is not less than 90%, and the refractive index is about 2.0, which is between that of quartz glass (1.46) and TiO2 (2.5), thus achieving a smooth transition in refractive index. The Si element in Si3N4, as the first bonding element, can form strong chemical bonds with Si and O in quartz glass, ensuring a stable connection between the transition layer 120 and the substrate layer 110; the N element can form strong chemical bonds with Ti in TiO2, enhancing the bonding strength between the transition layer 120 and the optical waveguide layer 130. Specifically, the gradient setting of the transition layer 120 is as follows: along the first direction, the atomic ratio of Si to N elements in the Si3N4 layer gradually decreases until it reaches 3:4, ensuring optimal crystal quality of Si3N4 and achieving a smooth transition in refractive index. When the transition layer 120 is TiO x N y At that time, TiO x N yThe light transmittance is not less than 90%, and the refractive index can be adjusted by the oxygen and nitrogen ratios of Ti, ranging from approximately 1.8 to 2.4, which is between that of quartz glass (1.46) and TiO2 (2.5). The gradient setting of the transition layer 120 is as follows: along the first direction, the oxygen ratio of Ti gradually decreases, and the nitrogen ratio gradually increases until the atomic ratio of Ti to O is 1:2, matching the atomic ratio of TiO2.

[0106] On the side of the transition layer 120 near the quartz glass substrate 110, Ti has a higher oxygen content and a lower nitrogen content. Ti-O bonds can form strong chemical bonds with Si and O in the quartz glass, improving the bonding strength between the transition layer 120 and the substrate 110. At this time, the refractive index of the transition layer 120 is low, close to that of the quartz glass, achieving an initial transition. As it extends towards the TiO2 optical waveguide layer 130, the oxygen content of Ti gradually decreases and the nitrogen content gradually increases. Ti-N bonds can form strong chemical bonds with Ti in TiO2, improving the bonding strength between the transition layer 120 and the optical waveguide layer 130. At the same time, the atomic ratio of Ti to O gradually transitions to 1:2, matching the atomic ratio of TiO2, achieving a smooth transition of refractive index and reducing optical loss.

[0107] For example, the substrate layer 110 is soda-lime glass or high-alumina-silicon optical glass, the optical waveguide layer 130 is ZnO, and the transition layer 120 is made of ZnO. x AlN or AlO x N y In the first direction of the transition layer 120, ZnO x In the AlN layer, the proportion of Zn gradually increases while the proportion of Al gradually decreases. x N y The oxygen content of Al in the layer gradually decreases while the nitrogen content gradually increases; the first direction is from the substrate layer 110 to the optical waveguide layer 130. When the transition layer 120 is ZnO x When AlN is used, ZnO x AlN combines the compatibility of ZnO and ZnO waveguide layer 130 with the good mechanical properties of AlN, making it well-suited for both substrate layer 110 and waveguide layer 130. Along the first direction, the proportion of Zn gradually increases while the proportion of Al gradually decreases, achieving a continuous transition in composition and a gradual increase in refractive index to accommodate the refractive index difference between substrate layer 110 and waveguide layer 130.

[0108] On the side of the transition layer 120 near the substrate layer 110, Al has a higher proportion and Zn has a lower proportion. Al can form strong chemical bonds with O in soda-lime glass or high-alumina-silicon optical glass, improving the bonding strength between the transition layer 120 and the substrate layer 110. At this time, the refractive index of the transition layer 120 is low and close to that of the substrate layer 110, achieving an initial transition. As it extends towards the ZnO optical waveguide layer 130, the proportion of Zn gradually increases and the proportion of Al gradually decreases. Zn can form strong chemical bonds with Zn and O in ZnO, improving the bonding strength between the transition layer 120 and the optical waveguide layer 130. At the same time, the refractive index of the transition layer 120 gradually increases and becomes close to that of ZnO, achieving a smooth transition of refractive index and reducing optical loss. When the transition layer 120 is AlO x N y Along the first direction, the oxygen content of Al gradually decreases and the nitrogen content gradually increases, thereby achieving a gradual increase in refractive index and a continuous transition in composition. This ensures a stable connection between the transition layer 120 and the substrate layer 110 and the ZnO optical waveguide layer 130, while also achieving lattice and refractive index matching to reduce optical loss.

[0109] This application also provides an optical waveguide sheet, such as Figure 2 As shown, the optical waveguide structure described above also includes: a coupling element 140, which is disposed on the optical waveguide layer 130. The coupling element 140 includes: a coupling unit 141, which is used to couple virtual imaging light into the optical waveguide layer 130 so that the virtual imaging light satisfies the total internal reflection condition and is propagated within the optical waveguide layer 130; and a coupling unit 142, which is used to couple and emit the virtual imaging light within the optical waveguide layer 130 on the side of the optical waveguide layer 130 away from the transition layer 120.

[0110] like Figure 2 As shown, a coupling element 140 is set on the optical waveguide structure described above. The coupling element 140 is set on the optical waveguide layer 130. The coupling element 140 is used to realize the coupling in and coupling out of the virtual imaging light, and complete the closed loop of the virtual imaging light transmission. The coupling element 140 includes a coupling in unit 141 and a coupling out unit 142. The two work together to ensure that the virtual imaging light can be transmitted and displayed efficiently and stably.

[0111] like Figure 2As shown, the coupling element 140 is positioned on the optical waveguide layer 130, specifically on the surface of the optical waveguide layer 130. This can be either the side of the optical waveguide layer 130 away from the transition layer 120 or the side surface of the optical waveguide layer 130. Preferably, the side of the optical waveguide layer 130 away from the transition layer 120 is selected. This avoids interference between the coupling element 140 and the transition layer 120 and the substrate layer 110, while ensuring that the virtual imaging light can be directly coupled into the optical waveguide layer 130, reducing light loss. Preferably, the coupling element 140 is located on the side of the waveguide layer away from the transition layer 120, i.e., the side closer to the human eye. When the optical engine 300 emits virtual imaging light, it enters the optical waveguide layer 130 through the coupling unit 141 and exits through the coupling unit 142, so that the human eye can observe the displayed image signal.

[0112] like Figure 2 As shown, the coupling unit 141 is used to couple virtual imaging light into the optical waveguide layer 130, ensuring that the virtual imaging light satisfies the total internal reflection condition for propagation within the optical waveguide layer 130. The virtual imaging light is emitted by the display module (optical engine 300) of the AR glasses. The display module is typically located on the temple or frame of the AR glasses. The emitted virtual imaging light needs to enter the optical waveguide layer 130 through the coupling unit 141 to achieve propagation and display. The design of the coupling unit 141 needs to meet two core requirements: first, it must be able to efficiently couple the virtual imaging light into the optical waveguide layer 130, with a coupling efficiency of not less than 85%, reducing light loss; second, it must be able to adjust the incident angle of the virtual imaging light so that after entering the optical waveguide layer 130, the incident angle is greater than the critical angle, satisfying the total internal reflection condition and achieving stable propagation.

[0113] The coupling unit 141 can be structured using a grating structure, a prism structure, or a holographic optical element structure, with a grating structure being preferred. Grating structures are small, lightweight, and easy to manufacture, making them well-suited to the lightweight requirements of AR glasses. They also offer high coupling efficiency and precise angle adjustment. The grating period, grating depth, and grating duty cycle of the grating-structured coupling unit 141 can be optimized based on the wavelength of the virtual imaging light and the refractive index of the waveguide layer 130, ensuring efficient coupling of the virtual imaging light and that the incident angle meets the total internal reflection condition.

[0114] The coupling unit 142 is used to couple and emit the virtual imaging light within the optical waveguide layer 130 on the side of the optical waveguide layer 130 away from the transition layer 120, guiding the virtual imaging light into the human eye to achieve the display of virtual information. The virtual imaging light is stably propagated within the optical waveguide layer 130 through total internal reflection to the location of the coupling unit 142. After being acted upon by the coupling unit 142, the propagation direction is changed, and the light is coupled and emitted out of the optical waveguide layer 130, entering the human eye. The human eye simultaneously receives the virtual imaging light and the real ambient light, achieving the fusion display of virtual information and the real scene.

[0115] The grating structure parameters of the output unit 142 are adapted to those of the input unit 141 and optimized according to the visual range of the human eye. The positions of the input unit 141 and the output unit 142 are correspondingly set. Typically, the input unit 141 is located in the edge region of the optical waveguide sheet, and the output unit 142 is located in the center region of the optical waveguide sheet or the region corresponding to the human eye. This ensures that after the virtual imaging light is coupled into the input unit 141, it is conducted through total internal reflection within the optical waveguide layer 130 to the output unit 142, and then coupled out by the output unit 142 to the human eye. The number of input units 141 and output units 142 can be set according to actual needs, usually one or more sets. In one embodiment, the input unit 141 includes multiple sets of gratings with different angles. Similarly, the output unit 142 also includes multiple sets of gratings with different angles to achieve two-dimensional display.

[0116] like Figure 3 As shown, the spatial region where the virtual imaging light is coupled out by the coupling unit 142 on the side of the optical waveguide layer 130 away from the transition layer 120 is called the eyebox 200; furthermore, multiple coupling elements 140 are provided on the optical waveguide layer 130. In each group of coupling elements 140, the coupling unit 141 and the coupling unit 142 are matched one-to-one to form an eyebox array 210 on the side of the optical waveguide layer 130 away from the transition layer 120. The eyebox array 210 is arranged along the direction perpendicular to the thickness of the waveguide sheet.

[0117] Define eyebox 200: The spatial region where the coupling unit 142 couples out virtual imaging light on the side of the optical waveguide layer 130 away from the transition layer 120 is defined as eyebox 200; after the coupling unit 142 couples out the virtual imaging light conducted within the optical waveguide layer 130, the virtual imaging light will form a specific spatial region on the side of the optical waveguide layer 130 away from the transition layer 120. Within this region, the brightness of the virtual imaging light is uniform and the clarity is high, which can meet the visual needs of the human eye. This spatial region is eyebox 200; eyebox 200 is the spatial range within which the virtual imaging light can clearly image. The human eye needs to be within eyebox 200 to see a clear and complete virtual image.

[0118] To further expand the range of the eye box 200, improve wearing comfort, and achieve two-dimensional high-definition display, this embodiment sets up multiple coupling elements 140, forming multiple groups of coupling elements 140 on the optical waveguide layer 130. In each group of coupling elements 140, the coupling-in unit 141 and the coupling-out unit 142 are matched one-to-one. The multiple groups of coupling elements 140 work together to form an eye box array 210 on the side of the optical waveguide layer 130 away from the transition layer 120. The eye box array 210 is arranged along the direction perpendicular to the thickness of the waveguide sheet.

[0119] like Figure 3As shown, multiple coupling elements 140 are disposed on the optical waveguide layer 130, typically divided into multiple groups. Each group of coupling elements 140 includes an input unit 141 and an output unit 142. The input unit 141 and the output unit 142 are matched one-to-one, meaning that the virtual imaging light coupled into each input unit 141 is transmitted to its matched output unit 142 and coupled out by the output unit 142 to form an eyebox 200. The multiple coupling elements 140 groups are arranged along the direction perpendicular to the thickness of the waveguide sheet, that is, along the plane direction of the optical waveguide sheet, forming a two-dimensional eyebox array 210. The eyebox array 210 is arranged along the direction perpendicular to the thickness of the waveguide sheet, specifically in a horizontal direction or a vertical direction. A two-dimensional array with both horizontal and vertical directions is preferred to achieve a wide eyebox 200 range and two-dimensional high-definition display. For example, 140 sets of 5×3 coupling elements are arranged in the horizontal direction of the optical waveguide sheet to form 15 eye boxes 200, which together form a 5×3 eye box array 210. The eye boxes 200 are interconnected to form a large-scale overall eye box 200 area. When the human eye moves within this overall area, it can always see a clear and complete virtual image to adapt to different eye positions. Compared with a single eye box 200, the eye box 200 area in this application is significantly expanded, greatly increasing the human eye's activity space. When wearing AR glasses, there is no need to deliberately align with a certain position to see a clear virtual image, which greatly improves wearing comfort. At the same time, the collaborative splicing of multiple eye boxes 200 can improve the resolution and display range of the virtual image, realize two-dimensional high-definition display, avoid problems such as display fragmentation and uneven brightness, and improve the AR display effect.

[0120] This application also provides a lens, including the aforementioned optical waveguide sheet; preferably, an antireflective coating, a protective layer, etc., may also be provided on the waveguide sheet.

[0121] This application also provides an AR glasses, including the aforementioned lenses; it also includes temples and a frame, with the lenses mounted on the frame to form the overall frame of the glasses; further including a display module (optical engine 300) for emitting virtual imaging light, an interaction module for enabling human-virtual information interaction, a computing module for running the system and processing image / interactive data, a sensing module for capturing the real environment and achieving spatial positioning, and a power supply / connection module for power supply and interconnection with external devices (mobile phones / computers).

[0122] Furthermore, this application also provides a fabrication process for an optical waveguide structure, used to prepare the aforementioned optical waveguide structure, such as... Figure 4 As shown, it includes: S1: Substrate treatment, cleaning and pretreatment of the substrate layer 110; S2: Deposition of transition layer 120: A transition layer 120 is deposited on the surface of the pretreated substrate layer 110. The transition layer 120 contains at least one first bonding element that bonds to the substrate layer 110 and at least one second bonding element that bonds to the optical waveguide layer 130. S3: Optical waveguide layer 130 deposition. Optical waveguide layer 130 is deposited on the side of transition layer 120 away from substrate layer 110, so that the refractive index of optical waveguide layer 130 is greater than the refractive index of transition layer 120.

[0123] Specifically, the core purpose of substrate treatment is to remove impurities, oxide layers, oil stains and surface defects from the surface of substrate layer 110, improve the cleanliness and smoothness of the surface of substrate layer 110, provide good substrate conditions for the subsequent deposition of transition layer 120, ensure that transition layer 120 and substrate layer 110 can form a stable chemical bond, and avoid impurities or defects from causing a decrease in interlayer bonding force, peeling or cracking.

[0124] The substrate 110 can be made of light-transmitting materials such as sapphire single crystal, quartz single crystal, magnesium oxide single crystal, or high-alumina-silicon optical glass, depending on the actual product requirements. The initial thickness of the substrate 110 is controlled at 0.1-1mm to ensure that it still meets the requirements for mechanical support and light transmission after subsequent processing. In one embodiment, the substrate 110 undergoes ultrasonic degreasing treatment. The substrate 110 is placed in an ultrasonic cleaning tank containing a mixed solution of anhydrous ethanol and deionized water (volume ratio 1:1). The ultrasonic power is controlled at 100-200W, and the ultrasonic time is 10-20 minutes to remove oil and soluble impurities from the surface of the substrate 110. Next, acid pickling is performed. The ultrasonically degreased substrate 110 is placed in a mixed acid pickling solution of dilute hydrochloric acid and hydrofluoric acid (concentration of 5-10%) and soaked for 5-10 minutes to remove impurities from the surface of the substrate 110. The substrate 110 is first removed by removing the oxide layer and metallic impurities. Then, it is rinsed multiple times with deionized water for 3-5 minutes each time until no acid washing solution remains on the surface of the substrate 110, so as to avoid residual acidic substances corroding the substrate 110 or affecting subsequent deposition. Finally, the rinsed substrate 110 is placed in a drying oven and dried at 80-120℃ for 10-15 minutes to obtain a clean, dry, and impurity-free pretreated substrate 110. After the pretreatment is completed, the surface of the substrate 110 needs to be inspected to ensure that the surface cleanliness meets the deposition requirements.

[0125] Deposition of transition layer 120: Deposit a transition layer 120 containing first and second bonding elements. On the surface of the pretreated substrate layer 110, a transition layer 120 capable of forming a stable bond with both the substrate layer 110 and the optical waveguide layer 130 is deposited. The transition layer 120 must contain at least one first bonding element (for bonding with the substrate layer 110) and at least one second bonding element (for bonding with the optical waveguide layer 130), providing a good connection for the subsequent deposition of the optical waveguide layer 130 and laying the foundation for subsequent gradient modulation.

[0126] The deposition method for the transition layer 120 can be selected according to the material of the transition layer 120. Physical vapor deposition (such as magnetron sputtering) or chemical vapor deposition (such as metal-organic chemical vapor deposition, MOCVD) is preferred. Among them, for aluminum nitride (AlN) and Al i Ga (1-i) For the N-type nitride transition layer 120, MOCVD is preferred, which enables precise control of composition and good crystal quality; for Si3N4 and AlO4... x N y For a transition layer of 120, magnetron sputtering can be used, which is a simple process with high deposition efficiency.

[0127] The selection of the first and second bonding elements must match the materials of the substrate 110 and the optical waveguide layer 130: if the substrate 110 is a sapphire single crystal (main elements Al and O), then the first bonding element should preferably be an element such as Al or Ga that can form a strong chemical bond with O; if the optical waveguide layer 130 is silicon carbide (main elements Si and C), then the second bonding element should preferably be an element such as N that can form a strong chemical bond with Si or C; if the optical waveguide layer 130 is GaN (main elements Ga and N), then the second bonding element should preferably be N, to ensure that the transition layer 120 and the optical waveguide layer 130 form a stable bond.

[0128] In one embodiment, the thickness of the transition layer 120 is controlled between 50-200 nm. If the thickness is too thin, effective bonding and subsequent gradient control cannot be achieved. If the thickness is too thick, it will increase optical loss and affect the optical performance of the optical waveguide structure. During the deposition process, the crystal quality of the transition layer 120 needs to be controlled to avoid too many crystal defects.

[0129] It should be noted that during the deposition process, the refractive index of the optical waveguide layer 130 must be strictly controlled to ensure that it is greater than the refractive index of the transition layer 120, and the refractive index difference is controlled between 0.3 and 1.0 to meet the requirements of total internal reflection transmission.

[0130] Furthermore, the deposition of the transition layer 120 also includes: gradually decreasing the content of the first bonding element and gradually increasing the content of the second bonding element in a first direction; wherein, the first direction is the direction from the substrate layer 110 to the optical waveguide layer 130. In other words, the deposition step of the transition layer 120 is further optimized to achieve a gradient distribution of the first and second bonding elements in the transition layer 120, that is, along the first direction (the direction from the substrate layer 110 to the optical waveguide layer 130), the content of the first bonding element gradually decreases and the content of the second bonding element gradually increases. Through this gradient control, a smooth transition of refractive index and lattice constant between the transition layer 120 and the substrate layer 110 and the optical waveguide layer 130 is achieved, alleviating lattice mismatch and interface stress, and further improving interlayer bonding and optical performance.

[0131] During the deposition of transition layer 120, the gradient distribution of the first and second bonding elements is achieved by precisely controlling the deposition process parameters. The specific control method is determined according to the deposition method of transition layer 120. If a transition layer 120 (such as a Si3N4 transition layer 120, with Si as the first bonding element and N as the second bonding element) is deposited using magnetron sputtering, the content of Si (the first bonding element) can be gradually reduced along the first direction and the content of N (the second bonding element) can be gradually increased along the first direction by gradually reducing the sputtering power of the Si target and maintaining a stable nitrogen flow rate. This ensures that the atomic ratio of Si to N gradually transitions to the ideal atomic ratio, achieving a smooth transition in composition and refractive index.

[0132] If MOCVD is used to deposit a transition layer of 120 (such as AlN, Al), i Ga (1-i) In the AlN transition layer 120, a gradient distribution is achieved by gradually adjusting the gas flow rates of the first bonding element source (such as Al source, Ga source) and the second bonding element source (such as N source). For example, for the AlN transition layer 120 (first bonding element Al, second bonding element N), the Al content gradually decreases along the first direction and the N content gradually increases along the first direction by gradually decreasing the flow rate of the Al source (such as trimethylaluminum, TMAl) and gradually increasing the flow rate of the N source (such as ammonia, NH3), until the atomic ratio of Al to N reaches 1:1.

[0133] Gradient control achieves a continuous and smooth transition, avoiding abrupt changes in elemental content. Therefore, the rate of change in elemental content needs to be uniform, which can be assisted by segmented deposition and real-time composition monitoring: the transition layer 120 is divided into 3-5 deposition segments along the first direction, and the elemental content of each deposition segment is set as a gradient change interval. The elemental content difference between adjacent deposition segments is uniform. During the deposition process, X-ray fluorescence spectrometry (XRF) is used to monitor the elemental content in real time. If there is a deviation from the designed gradient, process parameters (such as sputtering power and gas flow rate) are adjusted in real time to ensure accurate gradient distribution. In one embodiment, for Al... i Ga (1-i) The N transition layer 120 (i∈(0,1)) has Al and Ga as the first bonding elements and N as the second bonding element. Along the first direction, by gradually reducing the flux of the Al source and gradually increasing the flux of the Ga and N sources, the value of i (the mole fraction of Al) gradually decreases, the Al content gradually decreases, and the Ga and N content gradually increases. This achieves a smooth transition in refractive index and lattice constant from the sapphire substrate 110 to the silicon carbide optical waveguide layer 130, and minimizes the interface stress.

[0134] In one embodiment, the deposition of the optical waveguide layer 130 further includes: the optical waveguide layer 130 is silicon carbide, and the silicon carbide is deposited by low-pressure chemical vapor deposition or plasma-enhanced chemical vapor deposition; so that the deposition thickness of the silicon carbide is 400-600 nm.

[0135] When the optical waveguide layer 130 is silicon carbide, the substrate layer 110 is a sapphire single crystal, and the transition layer 120 is XN, where X is Al or Ga; the deposition of the transition layer 120 also includes: depositing the transition layer 120 using a metal-organic chemical vapor deposition method, by adjusting the flow rates of the X source and the N source, so that the X content gradually decreases along the first direction and the N content gradually increases along the first direction, until the stoichiometric ratio of X and N is 1:1, where the first direction is the direction from the substrate layer 110 to the optical waveguide layer 130.

[0136] Taking aluminum nitride as an example for transition layer 120 (the same applies to gallium nitride): On the pretreated substrate, the MOCVD reaction chamber was purged with hydrogen and a trimethylaluminum pre-laid Al layer at 40–60 mbar and 800–850 °C. Aluminum nitride layers were grown by introducing hydrogen, ammonia, and trimethylaluminum under conditions of 60–65 mbar and 1005–1255 °C. During the growth of the aluminum nitride layer, the gradient of Al content is reduced by adjusting the reaction chamber temperature, the flow rate of trimethylaluminum, and the inlet ratio, while the gradient of N content is increased by adjusting the flow rate of ammonia and the inlet ratio, so that the Al:N atomic ratio of the aluminum nitride transition layer 120 close to the optical waveguide layer 130 reaches 1:1.

[0137] Specifically, preparations before the deposition of the transition layer 120: After the substrate treatment is completed, the sapphire single crystal substrate layer 110 is placed in the MOCVD reaction chamber. First, the reaction chamber is vacuumed to ensure that the vacuum degree of the reaction chamber meets the deposition requirements. At the same time, the unobstructedness of each gas pipeline (hydrogen, TMA1, NH3) is checked, and the gas flow controller is calibrated to ensure precise control of process parameters.

[0138] Pre-laying the Al layer: This improves the wettability of the sapphire substrate 110 surface, avoids meltback etching during subsequent AlN growth, and ensures a stable bond between the AlN transition layer 120 and the sapphire substrate 110. Specifically: the MOCVD reaction chamber pressure is reduced to 40–60 mbar, the reaction chamber temperature is raised to 800–850 °C, and hydrogen (H2) and trimethylaluminum (TMAl) are introduced into the reaction chamber. Al pre-laying is performed for 3–4 minutes, with the H2 flow rate controlled at 150,000–1550 N·m·K. The flow rate of TMAl is controlled at 10-20 sccm. The intake ratio of H2 is G5:G4:G3:G2:G1=19.5:25.5:16.5:25.5:13 (the intake ratio can be adjusted according to the actual reaction chamber structure and is not limited to this ratio). The intake ratio of TMAl is G4:G2=0:100 (that is, TMAl is only introduced from the G2 intake port) to ensure that Al element is evenly covered on the surface of sapphire substrate 110 to form a thin and uniform Al pre-lay layer.

[0139] Growth of AlN transition layer 120: Gradient control of Al and N element content; after the pre-laying of the Al layer, the growth stage of AlN transition layer 120 begins. The core is to control the process parameters to make the Al element content decrease along the first direction (from the sapphire substrate 110 to the silicon carbide optical waveguide layer 130) and the N element content increase along the first direction, ultimately achieving an Al:N atomic ratio of 1:1 on the side of AlN transition layer 120 near the silicon carbide optical waveguide layer 130. Specifically: 1. Adjust the reaction chamber parameters: reduce the MOCVD reaction chamber pressure to 60-65 mbar and raise the reaction chamber temperature to 1005-1255℃. This temperature range can ensure the crystal quality of AlN and avoid the occurrence of amorphous phases or crystal defects. 2. Introducing Reaction Gases: Hydrogen (H2), ammonia (NH3), and trimethylaluminum (TMAl) are introduced into the reaction chamber. The three gases react at high temperature to grow an AlN transition layer 120. The process parameters for each gas are controlled as follows: (1) H2 flow rate: controlled at 156060~175950sccm, used as carrier gas and reducing gas to ensure uniform distribution of reaction gas and reduce impurities; the H2 inlet ratio adopts G5:G4:G3:G2:G1=17.0:25.0:15.0:25.0:18.0 (not limited to this ratio). (2) NH3 flow rate: controlled at 600-15000 sccm, as N source, its flow rate gradually increases along the first direction to achieve gradient increase of N element content; the NH3 intake ratio can be adjusted according to gradient requirements, including but not limited to G5:G3:G1=20.0:30.0:50.0, G5:G3:G1=40.0:40.0:20.0, etc., by adjusting the intake ratio, to help achieve uniform gradient distribution of N element; (3) TMAl flow rate: controlled at 220~715 sccm, as Al source, its flow rate gradually decreases along the first direction to achieve a gradient reduction of Al content; the inlet ratio of TMAl can be adjusted according to gradient requirements, including but not limited to G4:G2=0:100, G4:G2=5:95, G4:G2=15:85, G4:G2=40:60, etc., by adjusting the inlet ratio to ensure uniform Al gradient distribution; 3. Gradient control method: The gradient of Al is reduced by gradually decreasing the TMAl flow rate, adjusting the reaction chamber temperature (selectable temperatures include 1010℃, 1020℃, 1100℃, 1250℃, and 1255℃), and the TMAl inlet ratio. Increasing the temperature can promote the diffusion of Al and assist in gradient control. The gradient of N is increased by gradually increasing the NH3 flow rate and adjusting the NH3 inlet ratio to ensure that the reaction between N and Al is complete. 4. Growth time and thickness: The total thickness of the AlN transition layer 120 is controlled between 50-200 nm. The growth time is adjusted according to the thickness and growth rate. The growth rate is controlled between 1-2 nm / min to ensure that the thickness of the AlN transition layer 120 is uniform and the gradient transition is smooth.

[0140] After the AlN transition layer 120 is grown, the flow of TMAl and NH3 is stopped, and only H2 is introduced. The temperature and pressure of the reaction chamber are maintained for a period of time to allow the AlN transition layer 120 to fully crystallize, and then it is cooled to room temperature.

[0141] When the optical waveguide layer 130 is silicon carbide, the substrate layer 110 is sapphire single crystal, and the transition layer 120 is Al i Ga (1-i)N, where i∈(0,1); the deposition of the transition layer 120 further includes: depositing the transition layer 120 using metal-organic chemical vapor deposition, and adjusting the flow rates of the Al source, Ga source, and N source to gradually decrease the value of i along the first direction. In other words, the substrate layer 110 is a sapphire single crystal, and the transition layer 120 is Al i Ga (1-i) When N (i∈(0,1)), the MOCVD method is used to deposit the transition layer 120. By adjusting the flow rates of the Al source, Ga source and N source, the value of i is gradually reduced along the first direction, ensuring a smooth transition in refractive index and lattice constant between the transition layer 120 and the sapphire substrate layer 110 and the silicon carbide optical waveguide layer 130.

[0142] Specifically: 1. Substrate preparation: The pretreated sapphire single crystal substrate 110 is placed in the MOCVD reaction chamber and evacuated to 1×10⁻⁶. -3 Below Pa, H2 gas is introduced to raise the temperature of the reaction chamber to 1000-1100℃ and hold for 10-20 minutes to remove residual impurities and slight oxide layer on the surface of sapphire substrate 110 and improve surface activity. 2. Initialize process parameters: Adjust the pressure in the reaction chamber to 50-70 mbar and the temperature to 800-1000℃. Introduce H2 as the carrier gas and control the flow rate at 150,000-180,000 sccm to ensure uniform airflow inside the reaction chamber. 3. Gas introduction and i-value control: An Al source (TMAl), a Ga source (trimethylgallium, TMGa), and an N source (NH3) are introduced into the reaction chamber. The three gases react at high temperature to grow Al. i Ga (1-i) In the N transition layer 120, the core adjusts the flow rates of the three gases to gradually decrease the value of i along the first direction. (1) Initial stage (near the substrate 110): the i value is set to 0.8-0.9. At this time, the TMAl flow rate is controlled at 200-300 sccm, the TMGa flow rate is controlled at 20-50 sccm, and the NH3 flow rate is controlled at 5000-8000 sccm to ensure that the Al element content is high and the Ga element content is low, so that the transition layer 120 and the sapphire substrate 110 form a stable bond. (2) Gradient transition stage: As deposition proceeds, the flow rate of TMAl is gradually reduced (20-30 sccm every 5-10 min), the flow rate of TMGa is gradually increased (10-20 sccm every 5-10 min), and the flow rate of NH3 is gradually increased (500-1000 sccm every 5-10 min), so that the i value gradually decreases, the Al element content gradually decreases, and the Ga and N element content gradually increases, thus achieving a smooth transition of composition. (3) Termination stage (near optical waveguide layer 130): the i value drops to 0.1-0.2. At this time, the TMAl flow rate is controlled at 20-50 sccm, the TMGa flow rate is controlled at 200-300 sccm, and the NH3 flow rate is controlled at 12000-15000 sccm to ensure that the refractive index and lattice constant of the transition layer 120 and the silicon carbide optical waveguide layer 130 are matched, and the atomic ratio of Al / Ga to N transitions to 1:1, resulting in the best crystal quality. 4. Growth complete: Al i Ga (1-i) The total thickness of the N transition layer 120 is controlled between 50-200 nm, and the growth time is controlled between 30-60 min. After the growth is completed, the flow of TMAl, TMGa and NH3 is stopped, and only H2 is introduced. The temperature of the reaction chamber is maintained for 30 min, and then the temperature is slowly reduced to room temperature before the sample is taken out.

[0143] The specific process steps for epitaxially growing a silicon carbide optical waveguide layer 130 on the surface of the AlN transition layer 120 include in-situ etching, SiC growth, and cooling purging to ensure a stable bond between the silicon carbide optical waveguide layer 130 and the AlN transition layer 120, resulting in excellent crystal quality and meeting the requirements for total internal reflection. After depositing the aluminum nitride transition layer 120, the process also includes epitaxially growing the silicon carbide optical waveguide layer 130 on the surface of the aluminum nitride transition layer 120, including: Hydrogen gas was introduced into the reaction chamber as a carrier gas, and the surface of the aluminum nitride transition layer 120 was etched in situ under constant temperature conditions of 60-150 mbar and 1500-1700℃ for 10-30 min. Keeping the pressure and temperature of the reaction chamber constant, a Si source, a C source, and an optional doping source are introduced to control the carbon-silicon ratio at 0.6–1.2 and grow a silicon carbide layer with a thickness of 400–600 nm. The doping source is diluted through at least one stage of dilution pipeline before entering the reaction chamber, and the doping concentration is controlled by adjusting the flow rate of the doping source dilution gas. Turn off all gas sources, gradually cool the reaction chamber to 600-1000℃ and pressurize it to 900-1100mbar, purge with inert gas, and then cool and remove it.

[0144] Specifically, in-situ etching: Clean the surface of the AlN transition layer 120; after the AlN transition layer 120 is deposited, without removing the sample, in-situ etching is performed directly in the MOCVD reaction chamber (or a dedicated SiC epitaxial reaction chamber). The core purpose is to remove the oxide layer, residual impurities, and slight crystallization defects on the surface of the AlN transition layer 120, improve the activity of the AlN surface, and ensure that silicon carbide and the AlN transition layer 120 form a stable heteroepitaxial bond. Specifically, hydrogen (H2) is introduced into the reaction chamber as a carrier gas, the H2 flow rate is controlled at 80-400 slm, the reaction chamber pressure is adjusted to 60-150 mbar, the temperature is raised to 1500-1700℃, and the temperature is maintained for 10-30 min to perform in-situ etching on the surface of the AlN transition layer 120. H2 can react with the oxide layer (Al2O3) on the AlN surface at high temperatures, removing the oxide layer and etching away the surface defect layer, making the AlN transition layer 120 surface smooth and clean, providing a good substrate for SiC epitaxial growth.

[0145] Silicon carbide optical waveguide layer 130 is epitaxially grown; after in-situ etching, while keeping the pressure (60-150 mbar) and temperature (1500-1700℃) of the reaction chamber constant, the epitaxial growth of silicon carbide optical waveguide layer 130 begins, specifically as follows: 1. Introducing the growth source: Introduce a Si source, a C source, and an optional doping source (used to control the conductivity of SiC, such as nitrogen or ammonia for N-type doping) into the reaction chamber. The process parameters for each source are controlled as follows: (1) Si source: Select trichlorosilane (TCS) or dichlorosilane (DCS). The flow rate is set according to the C / Si ratio to ensure that the carbon-silicon ratio (C / Si) is controlled within the range of 0.6 to 1.2. If the carbon-silicon ratio is too high, excess C impurities will appear in SiC. If it is too low, Si vacancies will appear, affecting the crystal quality.

[0146] (2) C source: Select methane (CH4), ethane (C2H6) or ethylene (C2H4), and control the flow rate at 40-500 sccm. Adjust according to the Si source flow rate to ensure that the carbon-silicon ratio meets the requirements. (3) Doping source: If N-type doping is required, nitrogen or ammonia is selected as the doping source. The actual effective flow rate is controlled between 40 and 250 sccm. The doping source is diluted through at least one dilution pipeline (using H2 as the dilution gas) before entering the reaction chamber. By adjusting the flow rate of the doping source dilution gas, the N-type doping concentration is controlled between 8E+15 and 1.0E+16 cm. - Within the range of ³; 2. Growth parameter control: The growth rate is controlled between 5 and 100 μm / h. The growth time is adjusted according to the thickness requirements of the silicon carbide waveguide layer 130 to ensure that the thickness of the silicon carbide layer is 400 to 600 nm. During the growth process, the volatilization rate of the Si source is adjusted by controlling the flow rate of hydrogen entering the liquid Si source to further ensure the crystallization quality and thickness uniformity of SiC. Cooling and purging, and sample removal: After the silicon carbide optical waveguide layer 130 is grown, all growth sources (Si source, C source, doping source) are turned off, and H2 is kept flowing into the reaction chamber. The temperature of the reaction chamber is gradually reduced to 600-1000℃, while the pressure of the reaction chamber is gradually increased to 900-1100mbar to avoid sudden changes in temperature and pressure that could cause cracks or peeling of the SiC layer.

[0147] After the temperature and pressure stabilize, stop the H2 supply and introduce an inert gas (such as argon or nitrogen) to purge the reaction chamber and sample surface for 5-10 minutes to remove residual gas and impurities from the sample surface. Then continue cooling to room temperature, open the reaction chamber, remove the sample, and complete the epitaxial growth of the silicon carbide optical waveguide layer 130.

[0148] In other embodiments, the substrate 110 is a single crystal quartz, the optical waveguide layer 130 is silicon carbide, and the transition layer 120 is made of Si3N4 or AlN-SiO. x N y Composite layer; wherein, in the first direction of the transition layer 120, the Si element content in the Si3N4 layer gradually increases, and the N element content gradually decreases to an atomic ratio of 3:4; AlN-SiO x N y The proportion of AlN in the composite layer gradually increases, while that of SiO gradually decreases. x N y The proportion gradually decreases, and the Al content of AlN gradually decreases while the N content gradually increases to an atomic ratio of 1:1; the first direction is from the substrate layer 110 to the optical waveguide layer 130; Alternatively, the substrate 110 may be a single crystal of magnesium oxide, the waveguide layer 130 may be silicon carbide, and the transition layer 120 may be made of MgAl2O4 or a MgAl2O4-AlN composite layer. In the first direction of the transition layer 120, the proportion of MgAl2O4 in the MgAl2O4-AlN composite layer gradually decreases, while the proportion of AlN gradually increases. Furthermore, the Al content in AlN gradually decreases, while the N content gradually increases, until the atomic ratio of Al to N is 1:1. The first direction is the direction from the substrate 110 to the waveguide layer 130. Alternatively, the substrate 110 may be made of high-alumina-silicon optical glass, the waveguide layer 130 may be made of silicon carbide, and the transition layer 120 may be made of amorphous AlO₂. x N y or SiO x N yIn the first direction of the transition layer 120, AlO x N y In the layer, the oxygen content of Al gradually decreases while the nitrogen content gradually increases, and the SiO content gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is from the substrate layer 110 to the optical waveguide layer 130. Alternatively, the substrate 110 may be borosilicate glass, the optical waveguide layer 130 may be silicon carbide, and the transition layer 120 may be an amorphous SiO2-TiO2 composite layer or SiO2. x N y In the first direction of the transition layer 120, the proportion of TiO2 in the SiO2-TiO2 composite layer gradually increases, while the proportion of SiO2 gradually decreases. x N y The oxygen content of Si in the layer gradually decreases while the nitrogen content gradually increases; the first direction is from the substrate layer 110 to the optical waveguide layer 130. Alternatively, the substrate 110 may be sapphire, the waveguide layer 130 may be GaN, and the transition layer 120 may be made of Al. i Ga (1-i) N; wherein, in the first direction of the transition layer 120, the value of i gradually decreases, and the atomic ratio of Al / Ga to N gradually transitions to 1:1; the first direction is the direction from the substrate layer 110 to the optical waveguide layer 130; Alternatively, the substrate 110 may be made of quartz glass, the waveguide layer 130 of TiO2, and the transition layer 120 of Si3N4 or TiO2. x N y In the first direction of the transition layer 120, the atomic ratio of Si to N elements in the Si3N4 layer gradually decreases until it reaches 3:4; TiO x N y The oxygen content of Ti in the layer gradually decreases while the nitrogen content gradually increases until the atomic ratio of Ti to O is 1:2; the first direction is from the substrate layer 110 to the optical waveguide layer 130. Alternatively, the substrate 110 may be made of soda-lime glass or high-alumina-silicon optical glass, the waveguide layer 130 may be made of ZnO, and the transition layer 120 may also be made of ZnO. x AlN or AlO x N y In the first direction of the transition layer 120, ZnO x In the AlN layer, the proportion of Zn gradually increases while the proportion of Al gradually decreases. x N y The oxygen content of Al in the layer gradually decreases while the nitrogen content gradually increases; the first direction is from the base layer 110 to the optical waveguide layer 130.

[0149] This application also provides a method for fabricating an optical waveguide sheet, wherein a coupling element 140 is fabricated on the surface of the optical waveguide layer 130 of the optical waveguide structure, such as... Figure 5 As shown, fabricating the coupling element 140 includes: P1: Photolithography, photoresist is coated on the surface of the optical waveguide layer 130, and a photoresist mask is made by electron beam lithography. P2: Etching. Using a photoresist mask as a mask, the optical waveguide layer 130 is etched using a dry etching process to form coupling unit 141 and coupling unit 142. The coupling unit 141 is used to couple virtual imaging light into the optical waveguide layer 130 so that the virtual imaging light satisfies the total internal reflection condition and is propagated within the optical waveguide layer 130. The coupling unit 142 is used to couple and emit the virtual imaging light in the optical waveguide layer 130 on the side of the optical waveguide layer 130 away from the transition layer 120.

[0150] Furthermore, it also includes: fabricating multiple sets of photoresist masks; etching to form multiple sets of coupling elements 140 in the direction perpendicular to the thickness of the waveguide sheet, wherein in each set of coupling elements 140, the coupling-in unit 141 and the coupling-out unit 142 are matched one-to-one, so that an eyebox array 210 is formed on the side of the optical waveguide layer 130 away from the transition layer 120, and the eyebox array 210 is arranged along the direction perpendicular to the thickness of the waveguide sheet.

[0151] like Figure 3 As shown, multiple coupling elements 140 are disposed on the optical waveguide layer 130, typically divided into multiple groups. Each group of coupling elements 140 includes an input unit 141 and an output unit 142. The input unit 141 and the output unit 142 are matched one-to-one, meaning that the virtual imaging light coupled into each input unit 141 is transmitted to its matched output unit 142 and coupled out by the output unit 142 to form an eyebox 200. The multiple coupling elements 140 groups are arranged along the direction perpendicular to the thickness of the waveguide sheet, that is, along the plane direction of the optical waveguide sheet, forming a two-dimensional eyebox array 210. The eyebox array 210 is arranged along the direction perpendicular to the thickness of the waveguide sheet, specifically in a horizontal direction or a vertical direction. A two-dimensional array with both horizontal and vertical directions is preferred to achieve a wide eyebox 200 range and two-dimensional high-definition display. For example, in the horizontal direction of the optical waveguide sheet, 140 sets of 5×3 coupling elements are arranged to form 15 eye boxes 200, which together form a 5×3 eye box array 210. The eye boxes 200 are connected to each other to form a large-scale overall eye box 200 area. When the human eye moves within this overall area, it can always see a clear and complete virtual image to adapt to different human eye positions.

[0152] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0153] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A fabrication process for an optical waveguide structure, characterized in that, include: Substrate treatment: The substrate layer (110) is cleaned and pretreated. Transition layer (120) deposition: A transition layer (120) is deposited on the surface of the pretreated substrate layer (110). The transition layer (120) contains at least one first bonding element that bonds to the substrate layer (110) and at least one second bonding element that bonds to the optical waveguide layer (130). Optical waveguide layer (130) deposition: Optical waveguide layer (130) is deposited on the side of the transition layer (120) away from the substrate layer (110) such that the refractive index of the optical waveguide layer (130) is greater than the refractive index of the transition layer (120).

2. The fabrication process of an optical waveguide structure according to claim 1, characterized in that, The deposition of the transition layer (120) further includes: In a first direction, the content of the first bonding element is gradually reduced, and the content of the second bonding element is gradually increased; wherein, the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130).

3. The fabrication process of an optical waveguide structure according to claim 2, characterized in that, The deposition of the optical waveguide layer (130) also includes: The optical waveguide layer (130) is silicon carbide, which is deposited by low-pressure chemical vapor deposition or plasma-enhanced chemical vapor deposition, so that the deposition thickness of silicon carbide is 400-600 nm.

4. The fabrication process of an optical waveguide structure according to claim 3, characterized in that, The base layer (110) is a sapphire single crystal, and the transition layer (120) is XN, wherein X is Al or Ga; The deposition of the transition layer (120) further includes: depositing the transition layer (120) using a metal-organic chemical vapor deposition method, by adjusting the flow rates of the X source and the N source, so that the X content gradually decreases along the first direction and the N content gradually increases along the first direction until the atomic ratio of X to N is 1:1, wherein the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130).

5. The fabrication process of an optical waveguide structure according to claim 4, characterized in that, On the pretreated substrate, the MOCVD reaction chamber was purged with hydrogen and a trimethylaluminum pre-laid Al layer at 40–60 mbar and 800–850 °C. Aluminum nitride layers were grown by introducing hydrogen, ammonia, and trimethylaluminum under conditions of 60–65 mbar and 1005–1255 °C. During the growth of the aluminum nitride layer, the gradient of Al content is reduced by adjusting the reaction chamber temperature, the flow rate of trimethylaluminum and the inlet ratio, and the gradient of N content is increased by adjusting the flow rate of ammonia and the inlet ratio, so that the Al:N atomic ratio of the aluminum nitride transition layer (120) close to the optical waveguide layer (130) reaches 1:

1.

6. The fabrication process of an optical waveguide structure according to claim 5, characterized in that, After depositing the aluminum nitride transition layer (120), a silicon carbide optical waveguide layer (130) is epitaxially grown on the surface of the aluminum nitride transition layer (120), comprising: Hydrogen gas was introduced into the reaction chamber as a carrier gas, and the surface of the aluminum nitride transition layer (120) was etched in situ under constant temperature conditions of 60-150 mbar and 1500-1700℃ for 10-30 min. While maintaining constant pressure and temperature in the reaction chamber, a Si source, a C source, and an optional doping source are introduced to control the carbon-to-silicon ratio at 0.6–1.2, and a silicon carbide layer with a thickness of 400–600 nm is grown. The doping source is diluted through at least one stage of dilution pipeline before entering the reaction chamber, and the doping concentration is controlled by adjusting the flow rate of the doping source dilution gas. Turn off the gas source, gradually cool the reaction chamber to 600-1000℃ and pressurize it to 900-1100mbar, purge with inert gas, and then cool and remove it.

7. The fabrication process of an optical waveguide structure according to claim 3, characterized in that, The base layer (110) is a sapphire single crystal, and the transition layer (120) is Al. i Ga (1-i) N, where i∈(0,1); The deposition of the transition layer (120) further includes: depositing the transition layer (120) using a metal-organic chemical vapor deposition method, and adjusting the flow rates of the Al source, Ga source and N source to gradually decrease the i value along the first direction.

8. The fabrication process of an optical waveguide structure according to claim 1 or 2, characterized in that, The substrate layer (110) is a single crystal quartz, the optical waveguide layer (130) is silicon carbide, and the transition layer (120) is made of Si3N4 or AlN-SiO2. x N y Composite layer; wherein, in the first direction of the transition layer (120), the Si element content in the Si3N4 layer gradually increases, and the N element content gradually decreases to an atomic ratio of 3:4; AlN-SiO x N y The proportion of AlN in the composite layer gradually increases, while that of SiO gradually decreases. x N y The proportion gradually decreases, and the Al content of AlN gradually decreases while the N content gradually increases to an atomic ratio of 1:1; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130); Alternatively, the substrate layer (110) is a single crystal of magnesium oxide, the optical waveguide layer (130) is silicon carbide, and the transition layer (120) is made of MgAl2O4 or a MgAl2O4-AlN composite layer; wherein, in the first direction of the transition layer (120), the proportion of MgAl2O4 in the MgAl2O4-AlN composite layer gradually decreases, the proportion of AlN gradually increases, and the Al content of AlN gradually decreases and the N content gradually increases until the atomic ratio of Al to N is 1:1; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130); Alternatively, the substrate layer (110) may be high-alumina-silicon optical glass, the optical waveguide layer (130) may be silicon carbide, and the transition layer (120) may be made of amorphous AlO₂. x N y or SiO x N y； In the first direction of the transition layer (120), AlO x N y In the layer, the oxygen content of Al gradually decreases while the nitrogen content gradually increases, and the SiO content gradually decreases. x N y The oxygen content of Si in the layer gradually decreases and the nitrogen content gradually increases; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130); Alternatively, the substrate layer (110) may be borosilicate glass, the optical waveguide layer (130) may be silicon carbide, and the transition layer (120) may be an amorphous SiO2-TiO2 composite layer or SiO2. x N y In the first direction of the transition layer (120), the proportion of TiO2 in the SiO2-TiO2 composite layer gradually increases, while the proportion of SiO2 gradually decreases. x N y The oxygen content of Si in the layer gradually decreases and the nitrogen content gradually increases; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130); Alternatively, the substrate layer (110) may be sapphire, the optical waveguide layer (130) may be GaN, and the transition layer (120) may be made of Al. i Ga (1-i) N; wherein, in the first direction of the transition layer (120), the value of i gradually decreases, and the atomic ratio of Al / Ga to N gradually transitions to 1:1; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130); Alternatively, the substrate layer (110) may be made of quartz glass, the optical waveguide layer (130) may be made of TiO2, and the transition layer (120) may be made of Si3N4 or TiO2. x N y In the first direction of the transition layer (120), the atomic ratio of Si to N in the Si3N4 layer gradually decreases until it reaches 3:4; TiO x N y The oxygen content of Ti in the layer gradually decreases and the nitrogen content gradually increases until the atomic ratio of Ti to O is 1:2; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130); Alternatively, the substrate layer (110) may be made of soda-lime glass or high-alumina-silicon optical glass, the optical waveguide layer (130) may be made of ZnO, and the transition layer (120) may be made of ZnO. x AlN or AlO x N y In the first direction of the transition layer (120), ZnO x In the AlN layer, the proportion of Zn gradually increases while the proportion of Al gradually decreases. x N y The oxygen content of Al in the layer gradually decreases and the nitrogen content gradually increases; the first direction is the direction from the substrate layer (110) to the optical waveguide layer (130).

9. A method for fabricating an optical waveguide sheet, characterized in that, A coupling element (140) is fabricated on the surface of the optical waveguide layer (130) of the optical waveguide structure as described in any one of claims 1-8, wherein fabricating the coupling element (140) comprises: Photolithography involves coating the surface of the optical waveguide layer (130) with photoresist and fabricating a photoresist mask using electron beam lithography. Etching: Using the photoresist mask as a mask, the optical waveguide layer (130) is etched using a dry etching process to form a coupling unit (141) and a coupling unit (142). The coupling unit (141) is used to couple virtual imaging light into the optical waveguide layer (130) so that the virtual imaging light satisfies the total internal reflection condition and is conducted in the optical waveguide layer (130). The coupling unit (142) is used to couple and emit the virtual imaging light in the optical waveguide layer (130) away from the transition layer (120) on the side of the optical waveguide layer (130).

10. A method for fabricating an optical waveguide sheet according to claim 9, characterized in that, Also includes: Fabricate multiple sets of photoresist masks; Multiple sets of coupling elements (140) are formed by etching in a direction perpendicular to the thickness of the waveguide sheet. In each set of coupling elements (140), the coupling-in unit (141) and the coupling-out unit (142) are matched one-to-one, so that an eyebox array (210) is formed on the side of the optical waveguide layer (130) away from the transition layer (120). The eyebox array (210) is arranged in a direction perpendicular to the thickness of the waveguide sheet.

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