High diffraction efficiency grating waveguide structure and preparation method

Abstract

This application discloses a high diffraction efficiency grating waveguide structure and its fabrication method, relating to the field of diffraction waveguide technology. Through a structural design of double-layer cladding, double-layer grating assembly, and orthogonal bidirectional anisotropic arrangement of the grating assembly, combined with the optimal selection of materials for each layer, optimization of thickness and refractive index difference, and high-precision fabrication process, a high diffraction efficiency grating waveguide structure with excellent performance and simple process is obtained.

Description

Technical Field

[0001] This application relates to the field of diffractive waveguide technology, and in particular to a high diffraction efficiency grating waveguide structure and its fabrication method. Background Technology

[0002] In fields such as augmented reality (AR), optical communication, and biosensing, grating waveguides serve as core optical components, and their performance directly impacts the system's imaging quality, integration, and cost. Traditional grating waveguide technology suffers from problems such as low diffraction efficiency, narrow angular bandwidth, and high polarization sensitivity.

[0003] For example, Chinese patent application CN116661156A discloses a grating structure, a diffractive waveguide, and a display device. The grating structure includes a plurality of periodically arranged structural units disposed on the surface of a waveguide substrate. Each structural unit includes a first portion and a second portion. The first portion covers and adheres to the surface of the waveguide substrate, and the second portion adheres to and surrounds at least three surfaces of the first portion. The refractive index of the first portion is less than that of the second portion, and the volume ratio of the grating teeth of the structural unit to the volume of the first portion is greater than or equal to 3.

[0004] However, the fabrication process for this diffractive waveguide structure is still quite complex, and there is still room for improvement in diffraction efficiency. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides a high-diffraction-efficiency grating waveguide structure and its fabrication method. By controlling the layout of the grating structure units and optimizing the materials used in each structure, a high-diffraction-efficiency grating waveguide structure with excellent performance and a simple fabrication process is obtained.

[0006] To achieve the above objectives, this application adopts the following technical solution:

[0007] In a first aspect, this application provides a high diffraction efficiency grating waveguide structure, comprising:

[0008] basal layer;

[0009] The first cladding layer is attached to the upper and lower surfaces of the base layer;

[0010] A grating assembly array is attached to one of the first cladding surfaces, the grating assembly array comprising a plurality of grating assemblies;

[0011] A second cladding layer covers the grating assembly; wherein the grating assembly includes a first grating structural unit and a second grating structural unit; the refractive index of the materials used for the first grating structural unit and the second grating structural unit is higher than that of the first cladding layer and the second cladding layer; the first grating structural unit is attached to the surface of the first cladding layer, and the second grating structural unit includes a first unit substructure and a second unit substructure, the first unit substructure covers the first grating structural unit, the second unit substructure is attached to the surface of the first cladding layer, and one sidewall surface of the second unit substructure is combined with one sidewall surface of the first grating structural unit.

[0012] In the grating waveguide structure provided in this application, the first grating structure unit and the first unit substructure act as primary scatterers, coupling incident light into the waveguide; the second unit substructure further modulates the light field, achieving directional energy transmission through the interference effect of the double-layer structure. Furthermore, the large refractive index difference between the cladding material and the grating material creates strong optical contrast. The greater the refractive index difference between the cladding material and the grating material, the stronger the reflection and diffraction effects of light at the grating interface, resulting in higher coupling efficiency between the light field and the grating structure, reducing energy loss of zero-order transmitted light, and thus improving diffraction efficiency.

[0013] In one possible implementation, the arrangement direction of the grating assembly includes a first direction and a second direction, and the two directions are perpendicular to each other; the arrangement interval of the grating assembly in the first direction is smaller than the arrangement interval in the second direction; the first direction is the extension direction of the short side of the substrate layer; and the second direction is the extension direction of the long side of the substrate layer.

[0014] In one possible implementation, the grating assembly has an arrangement spacing of 200-350 nm in a first direction and an arrangement spacing of 400-700 nm in a second direction; the height of the first grating structural unit, the first unit substructure, and the second unit substructure is 100-150 nm.

[0015] In this application, the smaller spacing in the first direction corresponds to a higher spatial frequency, suitable for optical coupling perpendicular to the substrate; the larger spacing in the second direction is used for lateral light spread, meeting the requirements for diffraction angles in different directions. Asymmetric arrangement can suppress higher-order diffraction modes, reduce crosstalk, and increase the energy concentration of the principal diffraction orders, thereby improving diffraction efficiency. Furthermore, the grating height in this application is matched to the light penetration depth, which can enhance the interaction between light and the grating while avoiding scattering losses caused by excessively tall structures.

[0016] In one possible implementation, the thickness of the base layer is 0.5~2 mm; the thickness of the first cladding layer is 1~2 μm; and the thickness of the second cladding layer is 1~3 μm.

[0017] In this application, the thickness of the substrate layer provides sufficient mechanical support to avoid structural fragility due to excessive thinness; the thickness design of the first cladding layer can ensure effective confinement of the optical field within the waveguide structure and reduce its leakage to the substrate layer; the thickness design of the second cladding layer can further cover the grating assembly to form a complete waveguide channel, optimize the transmission of the optical field, and reduce multimode interference.

[0018] In one possible implementation, the material used for the substrate layer includes any one of borosilicate glass, aluminosilicate glass, and quartz glass; the material used for the first cladding layer includes silicon dioxide; the material used for the first grating structure unit includes any one of niobium oxide, tungsten trioxide, and tantalum pentoxide; the material used for the second grating structure unit is rutile titanium dioxide; and the material used for the second cladding layer includes any one of silicon dioxide and silicon oxynitride.

[0019] In this application, borosilicate glass, aluminosilicate glass, or quartz glass is used as the base layer material, possessing a low coefficient of expansion and high chemical stability to ensure structural stability during long-term use. Silica, as the first cladding material, has a low refractive index and good uniformity, reducing light transmission loss. High-refractive-index materials such as niobium oxide, tungsten trioxide, or tantalum pentoxide form a significant refractive index difference with silica. Furthermore, a refractive index difference also forms between niobium oxide, tungsten trioxide, or tantalum pentoxide and rutile titanium dioxide, thereby enhancing the diffraction efficiency of the grating. In addition, the silicon oxynitride in the second cladding material can be artificially adjusted to optimize waveguide mode matching.

[0020] Secondly, this application provides a method for fabricating a high-diffraction-efficiency grating waveguide structure, comprising the following steps:

[0021] S1: The substrate layer is pretreated, and then silicon dioxide is attached to the upper and lower surfaces of the substrate layer by plasma-enhanced chemical vapor deposition under the first parameter through the reaction of silane and oxygen to obtain the first cladding layer.

[0022] S2: A layer of the material used for the first grating structure unit is obtained by sputtering deposition on one of the surfaces of the first cladding layer, and then photoresist is applied;

[0023] S3: The first grating structure unit is obtained by etching using electron beam lithography.

[0024] S4: Rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit is obtained by sputtering deposition on the surface of the first cladding layer to which the first grating structure unit is attached, and then photoresist is applied.

[0025] S5: The second grating structure unit is obtained by etching using electron beam lithography, that is, a grating assembly with two different directional spacings is obtained;

[0026] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of the grating assembly;

[0027] S7: Finally, plasma-enhanced chemical vapor deposition is used. Under the second parameter, a second cladding layer is deposited on the grating assembly through the reaction of silane with a mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure is obtained.

[0028] In one possible implementation, the pretreatment method of the substrate layer is as follows: the substrate layer is immersed in anhydrous ethanol or acetone, ultrasonicated for 20-30 minutes, then removed and vacuum dried at 80-100°C.

[0029] In one possible implementation, the first parameter in S1 includes: a deposition temperature of 200~300℃, a working pressure of 10~50Pa, a silane gas flow rate of 50~100sccm, an oxygen carrier gas flow rate of 200~500sccm, and a deposition time of 10~20min.

[0030] In one possible implementation, the photoresist comprises any one of polymethyl methacrylate, ZEP520A, ZEP530A, and ZEP7000.

[0031] In one possible implementation, the second parameter in S7 includes: a deposition temperature of 200~300℃, a working pressure of 10~50Pa, a silane gas flow rate of 50~100sccm, a mixed gas of oxygen and nitrogen as a carrier gas with a flow rate of 200~500sccm, and a volume ratio of oxygen to nitrogen of (70~100):(0~30); a deposition time of 10~30min; and the parameters of the annealing treatment are: an annealing temperature of 300~500℃ and an annealing time of 3~5h.

[0032] In this application, the pretreatment method of the substrate layer can effectively remove impurities such as particles and oil stains from the substrate surface, while preventing the re-adhesion of dust in the air, improving surface cleanliness and adhesion, and ensuring the quality of subsequent deposition layers; plasma-enhanced chemical vapor deposition forms a uniform silicon dioxide first cladding layer at 200~300℃, which can reduce thermal stress and material damage; the high precision of electron beam lithography can achieve precise etching of nanoscale grating structures, ensuring the consistency of grating period and morphology; the inductively coupled plasma etching process can achieve the perpendicularity of the sidewalls of the grating structure units by precisely controlling the etching gas and parameters, reducing scattering loss; the selection of photoresist ensures the high resolution and pattern fidelity of electron beam lithography; the oxygen plasma ashing process can completely remove photoresist residues, avoiding contamination and optical performance degradation; annealing at 300~500℃ can eliminate internal stress in the cladding layer, improve material crystallinity, and improve the long-term stability and optical uniformity of the grating. It is the synergy of each step in the above preparation method and the optimization of various parameters that realizes the high-precision and high-consistency grating waveguide structure and performance.

[0033] Beneficial technical effects:

[0034] In this application, a high-diffraction-efficiency grating waveguide structure was fabricated through a structural design involving a double-layer cladding, a double-layer grating assembly, and a bi-directional anisotropic arrangement of the grating assembly. This was achieved by optimizing the materials of each layer, the thickness and refractive index difference, and employing high-precision fabrication processes. In this high-diffraction-efficiency grating waveguide structure, the first grating structural unit and the first unit substructure act as primary scatterers, coupling incident light into the waveguide. The second unit substructure further modulates the light field, achieving directional energy transmission through the interference effect of the double-layer structure. Furthermore, the smaller spacing in the first direction corresponds to a higher spatial frequency, suitable for optical coupling perpendicular to the substrate layer; the larger spacing in the second direction is used for lateral light propagation, meeting the requirements for diffraction angles in different directions. Moreover, the advantages of the fabricated grating assembly lie not only in the different spacing in the two directions but also in the synergy between the anisotropy in geometry and height and the periodic anisotropy of the difference in spacing between the two directions; the former provides a direction-dependent optical response, while the latter matches specific diffraction conditions. Furthermore, borosilicate glass, aluminosilicate glass, or quartz glass, used as the base layer material, possesses a low coefficient of thermal expansion and high chemical stability, ensuring structural stability during long-term use. Silica, as the first cladding material, has a low refractive index and good uniformity, reducing light transmission loss. High-refractive-index materials such as niobium oxide, tungsten trioxide, or tantalum pentoxide form a significant refractive index difference with silica, and also create a refractive index difference between niobium oxide, tungsten trioxide, or tantalum pentoxide and rutile titanium dioxide, thereby enhancing the diffraction efficiency of the grating. Finally, the silicon oxynitride material used in the second cladding of this application can have its nitrogen and oxygen content adjusted to optimize waveguide mode matching. This high-diffraction-efficiency grating waveguide structure achieves high diffraction efficiency and wide polarization control, while suppressing higher-order diffraction and reducing light field leakage. Attached Figure Description

[0035] Figure 1 This is a front view of the high diffraction efficiency grating waveguide structure of this application;

[0036] Figure 2 This is a top view of the high diffraction efficiency grating waveguide structure of this application;

[0037] Figure 3 This is a schematic diagram of step S1 in the fabrication of the high diffraction efficiency grating waveguide structure of this application from a side view.

[0038] Figure 4 This is a schematic diagram of the fabrication steps S2~S3 of the high diffraction efficiency grating waveguide structure of this application from a side view.

[0039] Figure 5 This is a schematic diagram of the fabrication steps S4~S6 of the high diffraction efficiency grating waveguide structure of this application from a side view.

[0040] Figure 6This is a schematic diagram of step S7 in the fabrication of the high diffraction efficiency grating waveguide structure of this application, viewed from the side.

[0041] Reference numerals: 1. Substrate layer; 2. First cladding layer; 3. Grating assembly; 4. First grating structural unit; 5. Second grating structural unit; 51. First unit substructure; 52. Second unit substructure; 6. Second cladding layer. Detailed Implementation

[0042] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the application will be further described in detail below with reference to embodiments. However, this should not be construed as limiting the scope of this application to the following examples. All other embodiments obtained by those skilled in the art without creative effort without departing from the above-described methodological spirit of this application are within the scope of protection of this application.

[0043] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0044] This application provides a high diffraction efficiency grating waveguide structure, the high diffraction efficiency grating waveguide structure comprising:

[0045] Basal layer 1;

[0046] The first cladding layer 2 is attached to the upper and lower surfaces of the base layer 1;

[0047] An array of grating assemblies 3 is attached to the surface of one of the first cladding layers 2, the array of grating assemblies 3 comprising a plurality of grating assemblies 3;

[0048] The second cladding layer 6 covers the grating assembly 3; wherein the grating assembly 3 includes a first grating structure unit 4 and a second grating structure unit 5; the refractive index of the materials used for the first grating structure unit 4 and the second grating structure unit 5 is higher than that of the first cladding layer 2 and the second cladding layer 6; the first grating structure unit 4 is attached to the surface of the first cladding layer 2, and the second grating structure unit 5 includes a first unit substructure 51 and a second unit substructure 52, the first unit substructure 51 covers the first grating structure unit 4, the second unit substructure 52 is attached to the surface of the first cladding layer 2, and one sidewall surface of the second unit substructure 52 is combined with one sidewall surface of the first grating structure unit 4.

[0049] In the grating waveguide structure provided in this application, the first grating structure unit 4 and the first unit substructure 51 act as primary scatterers, coupling incident light into the waveguide; the second unit substructure 52 further modulates the light field, achieving directional energy transmission through the interference effect of the double-layer structure. Furthermore, the large refractive index difference between the cladding material and the grating material creates strong optical contrast. The greater the refractive index difference between the cladding material and the grating material, the stronger the reflection and diffraction effects of light at the grating interface, resulting in higher coupling efficiency between the light field and the grating structure, reducing energy loss of zero-order transmitted light, and thus improving diffraction efficiency.

[0050] In one possible implementation, the arrangement direction of the grating assembly 3 includes a first direction and a second direction, and the two directions are perpendicular to each other; the arrangement interval of the grating assembly 3 in the first direction is smaller than the arrangement interval in the second direction; the first direction is the extension direction of the short side of the base layer 1; and the second direction is the extension direction of the long side of the base layer 1.

[0051] In one possible implementation, the grating assembly 3 has an arrangement spacing of 200~350nm in the first direction and an arrangement spacing of 400~700nm in the second direction; the height of the first grating structure unit 4, the first unit substructure 51 and the second unit substructure 52 are all 100~150nm.

[0052] In this application, the smaller spacing in the first direction corresponds to a higher spatial frequency, suitable for optical coupling perpendicular to the substrate layer 1; the larger spacing in the second direction is used for lateral light spread, meeting the requirements for diffraction angles in different directions. Asymmetric arrangement can suppress higher-order diffraction modes, reduce crosstalk, and increase the energy concentration of the principal diffraction orders, thereby improving diffraction efficiency. Furthermore, in this application, the grating height is matched to the light penetration depth, which can enhance the interaction between light and the grating while avoiding scattering losses caused by excessively tall structures.

[0053] In one possible implementation, the thickness of the base layer 1 is 0.5~2 mm; the thickness of the first cladding layer 2 is 1~2 μm; and the thickness of the second cladding layer 6 is 1~3 μm.

[0054] In this application, the thickness of the substrate 1 provides sufficient mechanical support to avoid structural fragility due to excessive thinness; the thickness design of the first cladding 2 can ensure effective confinement of the optical field within the waveguide structure and reduce its leakage to the substrate 1; the thickness design of the second cladding 6 can further cover the grating assembly 3 to form a complete waveguide channel, optimize the transmission of the optical field, and reduce multimode interference.

[0055] In one possible implementation, the material used for the substrate 1 includes any one of borosilicate glass, aluminosilicate glass, and quartz glass; the material used for the first cladding layer 2 includes silicon dioxide; the material used for the first grating structure unit 4 includes any one of niobium oxide, tungsten trioxide, and tantalum pentoxide; the material used for the second grating structure unit 5 is rutile titanium dioxide; and the material used for the second cladding layer 6 includes any one of silicon dioxide and silicon oxynitride.

[0056] In this application, borosilicate glass, aluminosilicate glass, or quartz glass is used as the material of the substrate layer 1, which has a low coefficient of expansion and high chemical stability, ensuring that the structure does not deform during long-term use. Silica, used as the material of the first cladding layer 2, has a low refractive index and good uniformity, reducing light transmission loss. The high-refractive-index materials niobium oxide, tungsten trioxide, or tantalum pentoxide form a significant refractive index difference with silica. Moreover, niobium oxide, tungsten trioxide, or tantalum pentoxide also form a refractive index difference with rutile titanium dioxide, thereby enhancing the diffraction efficiency of the grating. In addition, the silicon oxynitride in the material used for the second cladding layer 6 can be artificially adjusted to optimize waveguide mode matching.

[0057] The front view of the high diffraction efficiency grating waveguide structure is shown below. Figure 1 As shown, the top view is as follows Figure 2 As shown.

[0058] The following description, in conjunction with the accompanying drawings and different embodiments, details a method for fabricating a high diffraction efficiency grating waveguide structure provided in this application.

[0059] Example 1

[0060] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0061] S1: As Figure 3 As shown, the substrate 1 was immersed in acetone, ultrasonicated for 25 minutes, and then removed and vacuum dried at 90°C. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 250°C, a working pressure of 30 Pa, a silane gas flow rate of 75 sccm, an oxygen flow rate of 350 sccm, and a deposition time of 15 minutes. Silica was then deposited onto the upper and lower surfaces of the substrate 1 through the reaction of silane and oxygen to obtain the first coating layer 2.

[0062] S2: As Figure 4 As shown, a layer of niobium oxide, the material used for the first grating structure unit 4, is obtained by sputtering deposition on the surface of one of the first cladding layers 2, and then coated with photoresist polymethyl methacrylate.

[0063] S3: The first grating structure unit 4 is obtained by etching using electron beam lithography.

[0064] S4: As Figure 5 As shown, rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit 4 is obtained by sputtering deposition on the surface of the first cladding 2 on which the first grating structure unit 4 is attached, and then photoresist polymethyl methacrylate is coated on.

[0065] S5: The second grating structure unit 5 is obtained by etching using electron beam lithography, that is, the grating assembly 3 with two different directional spacings is obtained.

[0066] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of grating assembly 3;

[0067] S7: As Figure 6 As shown, plasma-enhanced chemical vapor deposition was finally used. Under the conditions of deposition temperature of 250℃, working pressure of 30Pa, silane gas flow rate of 75sccm, mixed gas flow rate of oxygen and nitrogen of 350sccm, volume ratio of oxygen to nitrogen of 70:30, and deposition time of 20min, the second cladding layer 6 was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0068] Example 2

[0069] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0070] S1: As Figure 3 As shown, the substrate 1 was immersed in anhydrous ethanol, ultrasonicated for 20 min, and then removed and vacuum dried at 80°C. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 200°C, a working pressure of 20 Pa, a silane gas flow rate of 50 sccm, an oxygen flow rate of 200 sccm, and a deposition time of 10 min. Silica was then deposited onto the upper and lower surfaces of the substrate 1 through the reaction of silane and oxygen to obtain the first coating layer 2.

[0071] S2: As Figure 4 As shown, a layer of tantalum pentoxide, the material used for the first grating structure unit 4, is obtained by sputtering deposition on one of the surfaces of the first cladding layer 2, and then coated with photoresist ZEP520A.

[0072] S3: The first grating structure unit 4 is obtained by etching using electron beam lithography.

[0073] S4: As Figure 5As shown, rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit 4 is obtained by sputtering deposition on the surface of the first cladding layer 2 on which the first grating structure unit 4 is attached, and then photoresist ZEP520A is coated on.

[0074] S5: The second grating structure unit 5 is obtained by etching using electron beam lithography, that is, the grating assembly 3 with two different directional spacings is obtained.

[0075] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of grating assembly 3;

[0076] S7: As Figure 6 As shown, plasma-enhanced chemical vapor deposition was finally used. Under the conditions of deposition temperature of 200℃, working pressure of 20Pa, silane gas flow rate of 50sccm, oxygen and nitrogen mixed gas flow rate of 200sccm, oxygen and nitrogen volume ratio of 80:20, and deposition time of 15min, the second cladding layer 6 was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0077] Example 3

[0078] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0079] S1: As Figure 3 As shown, the substrate 1 was immersed in anhydrous ethanol, ultrasonicated for 30 min, and then removed and vacuum dried at 100°C. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 300°C, a working pressure of 50 Pa, a silane gas flow rate of 100 sccm, an oxygen flow rate of 500 sccm, and a deposition time of 20 min. Silica was then deposited on the upper and lower surfaces of the substrate 1 through the reaction of silane and oxygen to obtain the first coating layer 2.

[0080] S2: As Figure 4 As shown, a layer of tungsten trioxide, the material used for the first grating structure unit 4, is obtained by sputtering deposition on one of the surfaces of the first cladding layer 2, and then coated with photoresist ZEP530A.

[0081] S3: The first grating structure unit 4 is obtained by etching using electron beam lithography.

[0082] S4: As Figure 5 As shown, rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit 4 is obtained by sputtering deposition on the surface of the first cladding 2 on which the first grating structure unit 4 is attached, and then photoresist ZEP530A is coated on.

[0083] S5: The second grating structure unit 5 is obtained by etching using electron beam lithography, that is, the grating assembly 3 with two different directional spacings is obtained.

[0084] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of grating assembly 3;

[0085] S7: As Figure 6 As shown, plasma-enhanced chemical vapor deposition was finally used. Under the conditions of deposition temperature of 300℃, working pressure of 50Pa, silane gas flow rate of 100sccm, oxygen and nitrogen mixed gas flow rate of 500sccm, oxygen and nitrogen volume ratio of 90:10, and deposition time of 30min, the second cladding layer 6 was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0086] Example 4

[0087] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0088] S1: As Figure 3 As shown, the substrate 1 was immersed in acetone, ultrasonicated for 25 minutes, and then removed and vacuum dried at 85°C. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 250°C, a working pressure of 25Pa, a silane gas flow rate of 60sccm, an oxygen flow rate of 250sccm, and a deposition time of 16 minutes. Silica was then deposited onto the upper and lower surfaces of the substrate 1 through the reaction of silane and oxygen to obtain the first coating layer 2.

[0089] S2: As Figure 4 As shown, a layer of niobium oxide, the material used for the first grating structure unit 4, is obtained by sputtering deposition on the surface of one of the first cladding layers 2, and then coated with photoresist ZEP7000.

[0090] S3: The first grating structure unit 4 is obtained by etching using electron beam lithography.

[0091] S4: As Figure 5 As shown, rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit 4 is obtained by sputtering deposition on the surface of the first cladding 2 on which the first grating structure unit 4 is attached, and then photoresist ZEP7000 is applied.

[0092] S5: The second grating structure unit 5 is obtained by etching using electron beam lithography, that is, the grating assembly 3 with two different directional spacings is obtained.

[0093] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of grating assembly 3;

[0094] S7: As Figure 6 As shown, plasma-enhanced chemical vapor deposition was finally used. Under the conditions of deposition temperature of 250℃, working pressure of 25Pa, silane gas flow rate of 60sccm, oxygen gas flow rate of 250sccm, no nitrogen, and deposition time of 10min, the second cladding layer 6 was deposited on the grating structure unit through the reaction of silane and oxygen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0095] Example 5

[0096] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0097] S1: As Figure 3 As shown, the substrate 1 was immersed in anhydrous ethanol, ultrasonicated for 20 min, and then removed and vacuum dried at 95°C. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 280°C, a working pressure of 40 Pa, a silane gas flow rate of 90 sccm, an oxygen flow rate of 450 sccm, and a deposition time of 18 min. Silica was then deposited onto the upper and lower surfaces of the substrate 1 through the reaction of silane and oxygen to obtain the first coating layer 2.

[0098] S2: As Figure 4 As shown, a layer of tungsten trioxide, the material used for the first grating structure unit 4, is obtained by sputtering deposition on one of the surfaces of the first cladding layer 2, and then coated with photoresist polymethyl methacrylate.

[0099] S3: The first grating structure unit 4 is obtained by etching using electron beam lithography.

[0100] S4: As Figure 5 As shown, rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit 4 is obtained by sputtering deposition on the surface of the first cladding 2 on which the first grating structure unit 4 is attached, and then photoresist polymethyl methacrylate is coated on.

[0101] S5: The second grating structure unit 5 is obtained by etching using electron beam lithography, that is, the grating assembly 3 with two different directional spacings is obtained.

[0102] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of grating assembly 3;

[0103] S7: As Figure 6As shown, plasma-enhanced chemical vapor deposition was finally used. Under the conditions of deposition temperature of 280℃, working pressure of 40Pa, silane gas flow rate of 90sccm, mixed gas flow rate of oxygen and nitrogen of 450sccm, volume ratio of oxygen to nitrogen of 75:25, and deposition time of 25min, the second cladding layer 6 was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0104] Example 6

[0105] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0106] S1: As Figure 3 As shown, the substrate 1 was immersed in acetone, ultrasonicated for 25 minutes, and then removed and vacuum dried at 90°C. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 240°C, a working pressure of 35Pa, a silane gas flow rate of 80sccm, an oxygen flow rate of 400sccm, and a deposition time of 12 minutes. Silica was then deposited on the upper and lower surfaces of the substrate 1 through the reaction of silane and oxygen to obtain the first coating layer 2.

[0107] S2: As Figure 4 As shown, a layer of tantalum pentoxide, the material used for the first grating structure unit 4, is obtained by sputtering deposition on one of the surfaces of the first cladding layer 2, and then coated with photoresist ZEP7000.

[0108] S3: The first grating structure unit 4 is obtained by etching using electron beam lithography.

[0109] S4: As Figure 5 As shown, rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit 4 is obtained by sputtering deposition on the surface of the first cladding 2 on which the first grating structure unit 4 is attached, and then photoresist ZEP7000 is applied.

[0110] S5: The second grating structure unit 5 is obtained by etching using electron beam lithography, that is, the grating assembly 3 with two different directional spacings is obtained.

[0111] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of grating assembly 3;

[0112] S7: As Figure 6As shown, plasma-enhanced chemical vapor deposition was finally used. Under the conditions of deposition temperature of 240℃, working pressure of 35Pa, silane gas flow rate of 80sccm, mixed gas flow rate of oxygen and nitrogen of 400sccm, volume ratio of oxygen to nitrogen of 85:15, and deposition time of 20min, the second cladding layer 6 was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0113] Comparative Example 1

[0114] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0115] S1: The substrate layer is immersed in acetone, ultrasonicated for 25 minutes, removed, and vacuum dried at 90°C. Then, it is subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 250°C, a working pressure of 30Pa, a silane gas flow rate of 75sccm, an oxygen flow rate of 350sccm, and a deposition time of 15 minutes. Silica is then deposited onto the upper and lower surfaces of the substrate layer through the reaction of silane and oxygen to obtain the first coating layer.

[0116] S2: A layer of niobium oxide, the material used for the first grating structure unit, is obtained by sputtering deposition on one of the surfaces of the first cladding layer, and then coated with photoresist polymethyl methacrylate;

[0117] S3: The first grating structure unit is obtained by etching using electron beam lithography.

[0118] S4: Use oxygen plasma ashing process to remove photoresist residue from the surface of the first grating structure unit;

[0119] S5: Finally, plasma-enhanced chemical vapor deposition was also used. Under the conditions of deposition temperature of 250℃, working pressure of 30Pa, silane gas flow rate of 75sccm, oxygen and nitrogen mixed gas flow rate of 350sccm, oxygen and nitrogen volume ratio of 70:30, and deposition time of 20min, the second cladding layer was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0120] Comparative Example 2

[0121] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0122] S1: The substrate layer was immersed in anhydrous ethanol, sonicated for 30 min, and then removed and vacuum dried at 100℃. Then, it was subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 300℃, a working pressure of 50Pa, a silane gas flow rate of 100sccm, an oxygen flow rate of 500sccm, and a deposition time of 20 min. Silica was then deposited onto the upper and lower surfaces of the substrate layer through the reaction of silane and oxygen to obtain the first coating layer.

[0123] S2: A layer of rutile phase titanium dioxide is obtained by sputtering deposition on one surface of the first cladding layer, and then photoresist ZEP530A is coated on it;

[0124] S3: The second grating structure unit is obtained by etching using electron beam lithography.

[0125] S4: Use oxygen plasma ashing process to remove photoresist residue from the surface of the second grating structure unit;

[0126] S5: Finally, plasma-enhanced chemical vapor deposition was also used. Under the conditions of deposition temperature of 300℃, working pressure of 50Pa, silane gas flow rate of 100sccm, mixed gas flow rate of oxygen and nitrogen of 500sccm, volume ratio of oxygen to nitrogen of 90:10, and deposition time of 30min, the second cladding layer was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0127] Comparative Example 3

[0128] A high diffraction efficiency grating waveguide structure is fabricated by the following steps:

[0129] S1: The substrate layer is immersed in acetone, ultrasonicated for 25 minutes, removed, and vacuum dried at 90°C. Then, it is subjected to plasma-enhanced chemical vapor deposition at a deposition temperature of 240°C, a working pressure of 35Pa, a silane gas flow rate of 80sccm, an oxygen flow rate of 400sccm, and a deposition time of 12 minutes. Silica is then deposited onto the upper and lower surfaces of the substrate layer through the reaction of silane and oxygen to obtain the first coating layer.

[0130] S2: A layer of tantalum pentoxide, the material used for the first grating structure unit, is obtained by sputtering deposition on one of the surfaces of the first cladding layer, and then coated with photoresist ZEP7000;

[0131] S3: The first grating structure unit is obtained by etching using electron beam lithography.

[0132] S4: Rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit is obtained by sputtering deposition on the surface of the first cladding layer to which the first grating structure unit is attached, and then photoresist ZEP7000 is applied.

[0133] S5: The second grating structure unit is obtained by etching using electron beam lithography, and a grating assembly with two directional spacings is fabricated.

[0134] S6: Use oxygen plasma ashing process to remove photoresist residue from the surface of the grating assembly;

[0135] S7: Finally, plasma-enhanced chemical vapor deposition was also used. Under the conditions of deposition temperature of 240℃, working pressure of 35Pa, silane gas flow rate of 80sccm, mixed gas flow rate of oxygen and nitrogen of 400sccm, volume ratio of oxygen to nitrogen of 85:15, and deposition time of 20min, the second cladding layer was deposited on the grating structure unit through the reaction of silane with the mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure was obtained.

[0136] The diffraction efficiency and transmission loss of the high diffraction efficiency grating waveguide structures prepared in Examples 1-6 and Comparative Examples 1-3 were tested. The test results are shown in Table 1.

[0137] Table 1. Test results of the high diffraction efficiency grating waveguide structures prepared in Examples 1-6 and Comparative Examples 1-3

[0138] Diffraction efficiency (%) Transmission loss (dB / cm) Example 1 82 0.3 Example 2 79 0.5 Example 3 83 0.2 Example 4 81 0.6 Example 5 78 0.7 Example 6 83 0.4 Comparative Example 1 26 4.3 Comparative Example 2 39 2.7 Comparative Example 3 51 1.8

[0139] As shown in Table 1, the high diffraction efficiency grating waveguide structures prepared in Examples 1-6 have better test data than those in Comparative Examples 1-3.

[0140] This is because, in the high diffraction efficiency grating waveguide structures fabricated in Examples 1-6, the smaller spacing in the first direction corresponds to a higher spatial frequency, suitable for optical coupling perpendicular to the substrate 1; the larger spacing in the second direction is used for lateral light spread, meeting the requirements for diffraction angles in different directions. Moreover, the advantage of the fabricated grating assembly lies not only in the different spacing in the two directions, but also in the synergy between the anisotropy in geometry and height and the periodic anisotropy of the difference in spacing between the two directions; the former provides a direction-dependent optical response, while the latter matches specific diffraction conditions. Furthermore, borosilicate glass, aluminosilicate glass, or quartz glass, as substrate materials, have low coefficients of expansion and high chemical stability, ensuring that the structure does not deform during long-term use; silicon dioxide, as the first cladding material, has a low refractive index and good uniformity, reducing light transmission loss; high-refractive-index materials such as niobium oxide, tungsten trioxide, or tantalum pentoxide form a significant refractive index difference with silicon dioxide, and niobium oxide, tungsten trioxide, or tantalum pentoxide also form a refractive index difference with rutile titanium dioxide, thereby enhancing the diffraction efficiency of the grating. Furthermore, the silicon oxynitride material used in the second cladding can be used to optimize waveguide mode matching by artificially adjusting the ratio of nitrogen and oxygen components.

[0141] Compared with Example 1, Comparative Example 1 did not construct a second grating structure unit, so it could not generate the synergy of geometric anisotropy in shape and height and periodic anisotropy with the difference in spacing between the two directions. Moreover, the refractive index difference between niobium oxide and rutile titanium dioxide was also absent. As a result, the diffraction efficiency of the grating was significantly reduced and the transmission loss was significantly increased.

[0142] Compared with Example 3, Comparative Example 2 did not construct the first grating structure unit, and it also could not produce the synergy of geometric anisotropy and periodic anisotropy with the difference in the spacing between the two directions. However, the refractive index difference between rutile titanium dioxide and silicon dioxide was higher than that between tungsten trioxide and silicon dioxide. Although the diffraction efficiency and transmission loss of the grating were worse than those of Example 3, they were still better than those of Comparative Example 1.

[0143] Compared with Example 6, Comparative Example 3 has the same arrangement interval in both directions, so there is no periodic anisotropy due to the difference in interval between the two directions, and it is also impossible to produce the synergy between the anisotropy in geometry and height and the periodic anisotropy due to the difference in interval between the two directions; however, since it has a complete first grating structure unit and a second grating structure unit, although the diffraction efficiency and transmission loss of the final grating are worse than those of Example 6, the performance in these two aspects is still better than that of Comparative Example 1 and Comparative Example 2.

[0144] The above results demonstrate and describe the basic principles and main features of this application, as well as its advantages.

[0145] Those skilled in the art should understand that this application is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of this application. Various changes and modifications can be made to this application without departing from the spirit and scope thereof, and all such changes and modifications fall within the scope of this application as claimed. The scope of protection of this application is defined by the equivalents of the appended claims.

Claims

1. A high diffraction efficiency grating waveguide structure, characterized in that, include: Basal layer (1); The first cladding layer (2) is attached to the upper and lower surfaces of the base layer (1); An array of grating assemblies (3) is attached to the surface of one of the first cladding layers (2), the array of grating assemblies (3) comprising a plurality of grating assemblies (3). The second cladding (6) covers the grating assembly (3); wherein the grating assembly (3) includes a first grating structure unit (4) and a second grating structure unit (5); the refractive index of the materials used in the first grating structure unit (4) and the second grating structure unit (5) is higher than that of the first cladding (2) and the second cladding (6); the first grating structure unit (4) is attached to the surface of the first cladding (2), and the second grating structure unit (5) includes a first unit substructure (51) and a second unit substructure (52), the first unit substructure (51) covers the first grating structure unit (4), the second unit substructure (52) is attached to the surface of the first cladding (2), and one side wall surface of the second unit substructure (52) is combined with one side wall surface of the first grating structure unit (4).

2. The high diffraction efficiency grating waveguide structure according to claim 1, characterized in that, The arrangement direction of the grating assembly (3) includes a first direction and a second direction, and the two directions are perpendicular to each other; the arrangement interval of the grating assembly (3) in the first direction is smaller than the arrangement interval in the second direction; the first direction is the extension direction of the short side of the base layer (1); the second direction is the extension direction of the long side of the base layer (1).

3. The high diffraction efficiency grating waveguide structure according to claim 2, characterized in that, The arrangement interval of the grating assembly (3) in the first direction is 200~350nm, and the arrangement interval in the second direction is 400~700nm; the height of the first grating structure unit (4), the first unit substructure (51), and the second unit substructure (52) is 100~150nm.

4. The high diffraction efficiency grating waveguide structure according to claim 1, characterized in that, The thickness of the base layer (1) is 0.5~2mm; the thickness of the first cladding layer (2) is 1~2μm; and the thickness of the second cladding layer (6) is 1~3μm.

5. The high diffraction efficiency grating waveguide structure according to claim 1, characterized in that, The material used in the base layer (1) includes any one of borosilicate glass, aluminosilicate glass and quartz glass; the material used in the first cladding layer (2) includes silicon dioxide; the material used in the first grating structure unit (4) includes any one of niobium oxide, tungsten trioxide and tantalum pentoxide; the material used in the second grating structure unit (5) is rutile phase titanium dioxide; the material used in the second cladding layer (6) includes any one of silicon dioxide and silicon oxynitride.

6. A method for fabricating a high diffraction efficiency grating waveguide structure, characterized in that, The method for fabricating the high diffraction efficiency grating waveguide structure according to any one of claims 1 to 5 includes the following steps: S1: The substrate (1) is pretreated and then silicon dioxide is attached to the upper and lower surfaces of the substrate (1) by plasma-enhanced chemical vapor deposition under the first parameter through the reaction of silane and oxygen to obtain the first cladding (2). S2: A layer of the material used for the first grating structure unit (4) is obtained by sputtering deposition on one of the surfaces of the first cladding layer (2), and then photoresist is applied; S3: The first grating structure unit (4) is obtained by etching using electron beam lithography. S4: Rutile titanium dioxide that adheres to and covers the sidewall of the first grating structure unit (4) is obtained by sputtering deposition on the surface of the first cladding (2) to which the first grating structure unit (4) is attached, and then photoresist is applied. S5: The second grating structure unit (5) is obtained by etching using electron beam lithography, that is, a grating assembly with two different directional spacings (3) is obtained. S6: Use oxygen plasma ashing process to remove photoresist residue on the surface of the grating assembly (3); S7: Finally, plasma-enhanced chemical vapor deposition is used. Under the second parameter, a second cladding layer (6) is deposited on the grating assembly (3) by the reaction of silane with a mixture of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure is obtained.

7. The method for fabricating a high diffraction efficiency grating waveguide structure according to claim 6, characterized in that, The pretreatment method of the substrate layer (1) is as follows: the substrate layer (1) is immersed in anhydrous ethanol or acetone, ultrasonicated for 20~30 minutes, and then taken out and vacuum dried at 80~100℃.

8. The method for fabricating a high diffraction efficiency grating waveguide structure according to claim 6, characterized in that, The first parameter in S1 includes: deposition temperature of 200~300℃, working pressure of 10~50Pa, silane gas flow rate of 50~100sccm, oxygen as carrier gas flow rate of 200~500sccm, and deposition time of 10~20min.

9. The method for fabricating a high diffraction efficiency grating waveguide structure according to claim 6, characterized in that, The photoresist includes any one of polymethyl methacrylate, ZEP520A, ZEP530A, and ZEP7000.

10. The method for fabricating a high diffraction efficiency grating waveguide structure according to claim 6, characterized in that, The second parameter in S7 includes: deposition temperature of 200~300℃, working pressure of 10~50Pa, silane gas flow rate of 50~100sccm, oxygen and nitrogen mixed gas as carrier gas flow rate of 200~500sccm, oxygen to nitrogen volume ratio of (70~100):(0~30); deposition time of 10~30min; the annealing parameters are: annealing temperature of 300~500℃, annealing time of 3~5h.

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