Grating waveguide structure with high diffraction efficiency and preparation method

Abstract

The invention discloses a high-diffraction-efficiency grating waveguide structure and a preparation method, and relates to the technical field of diffraction optical waveguides. Through the structural design of the double-layer cladding, the double-layer grating assembly and the orthogonal bidirectional anisotropic arrangement of the grating assembly, and in combination with the optimization of each layer of material, the optimization of the thickness and the refractive index difference and the high-precision preparation process, the high-diffraction-efficiency grating waveguide structure with excellent performance and simple process is obtained.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of diffractive optical waveguide, and particularly relates to a high-diffraction-efficiency grating waveguide structure and a preparation method. BACKGROUND

[0002] In the fields of augmented reality (AR), optical communication, biosensing, etc., as a core optical element, the performance of grating waveguide directly affects the imaging quality, integration level and cost of the system. The traditional grating waveguide technology has problems of low diffraction efficiency, narrow angle bandwidth, strong polarization sensitivity, etc.

[0003] For example, a grating structure, a diffractive optical waveguide and a display device are disclosed in Chinese Patent Application No. CN116661156A, the grating structure includes a plurality of periodically arranged structure units arranged on the surface of a waveguide substrate, the structure unit includes a first part and a second part, the first part covers and adheres to the surface of the waveguide substrate, the second part adheres to and at least surrounds three surfaces of the first part, the refractive index of the first part is less than the refractive index of the second part, and the volume ratio of the grating teeth of the structure unit to the first part is greater than or equal to 3.

[0004] However, the process of the diffractive optical waveguide structure is still relatively complex, and the diffraction efficiency still has room for improvement. SUMMARY

[0005] In view of the deficiencies of the prior art, the present application provides a high-diffraction-efficiency grating waveguide structure and a preparation method. Through layout control of grating structure units and cooperation and optimization of materials selected between structures, a high-diffraction-efficiency grating waveguide structure with excellent performance and simple preparation process is obtained.

[0006] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows:

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

[0008] a substrate layer;

[0009] a first cladding layer attached to the upper and lower surfaces of the substrate layer;

[0010] a grating combination body array attached to one surface of the first cladding layer, the grating combination body array comprising a plurality of grating combination bodies;

[0011] A second cladding layer covers the grating assembly; wherein the grating assembly comprises a first grating structure unit and a second grating structure unit; the refractive index of the material used by the first grating structure unit and the second grating structure unit is higher than that of the first cladding layer and the second cladding layer; the first grating structure unit is attached to the surface of the first cladding layer, the second grating structure unit comprises a first unit substructure and a second unit substructure, the first unit substructure covers the first grating structure unit, the second unit substructure is attached to the surface of the first cladding layer, and one side of the sidewall surface of the second unit substructure is combined with one side of the sidewall surface of the first grating structure unit.

[0012] In the grating waveguide structure provided in the application, the first grating structure unit and the first unit substructure serve as primary scatterers to couple incident light into the waveguide; the second unit substructure further modulates the light field to realize directional energy transmission through the interference effect of the double-layer structure. Moreover, the refractive index difference between the cladding material and the grating material is large, which can form strong optical contrast. The larger the refractive index difference between the cladding material and the grating material, the stronger the reflection and diffraction effect of light at the grating interface, and the higher the coupling efficiency of the light field and the grating structure, thereby reducing the energy loss of zero-order transmitted light and further improving the diffraction efficiency.

[0013] In a possible implementation, the arrangement direction of the grating assembly comprises 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 that 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 a possible implementation, the arrangement interval of the grating assembly in the first direction is 200-350 nm, and the arrangement interval in the second direction is 400-700 nm; the height of the first grating structure unit, the first unit substructure, and the second unit substructure is 100-150 nm.

[0015] In the application, the smaller interval of the first direction corresponds to a higher spatial frequency, which is suitable for vertical light coupling of the substrate layer; the larger interval of the second direction is used for lateral light expansion, which meets the requirement of different diffraction angles. Asymmetric arrangement can suppress high-order diffraction modes, reduce crosstalk, and improve the energy concentration of the main diffraction order, thereby improving the diffraction efficiency. Moreover, the height of the grating in the application matches the penetration depth of light, which can enhance the interaction between light and the grating, and at the same time avoid scattering loss caused by excessively high structures.

[0016] In a possible implementation, the thickness of the substrate 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 the present application, the thickness of the substrate layer provides sufficient mechanical support to avoid structural weakness caused by being too thin; the thickness of the first cladding layer is designed to ensure effective confinement of the optical field within the waveguide structure, reducing its leakage to the substrate layer; the thickness of the second cladding layer is designed to further cover the grating assembly, forming a complete waveguide channel, optimizing the transmission of the optical field, and reducing 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 the present application, borosilicate glass, aluminosilicate glass, or quartz glass is used as the substrate layer material, which has a low expansion coefficient and high chemical stability, ensuring that the structure does not deform during long-term use; silicon dioxide is used as the first cladding layer material, which has a low refractive index and good uniformity, reducing optical transmission loss; the high-refractive-index materials niobium oxide, tungsten trioxide, or tantalum pentoxide form a significant refractive index difference with silicon dioxide, and a refractive index difference is also formed 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 used in the second cladding layer material can be artificially adjusted to optimize waveguide mode matching.

[0020] In a second aspect, the present application provides a preparation method of a high-diffraction-efficiency grating waveguide structure, including the following steps:

[0021] S1: pretreat the substrate layer, and then, through plasma-enhanced chemical vapor deposition, attach silicon dioxide to the upper and lower surfaces of the substrate layer by reacting silane with oxygen under first parameters to obtain a first cladding layer;

[0022] S2: deposit a layer of the material used for the first grating structure unit on one surface of the first cladding layer by sputtering, and then apply photoresist;

[0023] S3: etch to obtain the first grating structure unit using electron beam lithography technology;

[0024] S4: deposit rutile titanium dioxide on the surface of the first cladding layer to which the first grating structure unit is attached by sputtering, so as to conform to the sidewall of the first grating structure unit and cover the first grating structure unit, and then apply photoresist;

[0025] S5: etching to obtain a second grating structure unit by using electron beam lithography technology, that is, to obtain a grating combination with different intervals in two directions;

[0026] S6: removing photoresist residues on the surface of the grating combination by using oxygen plasma ashing process;

[0027] S7: finally, depositing a second cladding layer on the grating combination by using plasma enhanced chemical vapor deposition, and by reacting silane with a mixed gas of oxygen and nitrogen under second parameters, to obtain the high-efficiency grating waveguide structure after annealing treatment.

[0028] In a possible implementation, the pretreatment method of the substrate layer is as follows: the substrate layer is immersed in anhydrous ethanol or acetone, taken out after ultrasonic treatment for 20-30 min, and vacuum dried at 80-100℃.

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

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

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

[0032] In the present application, the pretreatment method of the substrate layer can effectively remove impurities such as particles and oil stains on the surface of the substrate layer, while avoiding the reattachment of dust in the air, improving the surface cleanliness and adhesion, and ensuring the quality of the subsequent deposition layer; the plasma enhanced chemical vapor deposition forms a uniform first silicon dioxide cladding layer at 200-300℃, which can reduce thermal stress and material damage; the high precision of electron beam lithography can realize accurate etching of nanoscale grating structure, ensuring the consistency of grating period and morphology; the inductively coupled plasma etching process can realize the perpendicularity of the sidewall of the grating structure unit by accurately controlling the etching gas and parameters, and reduce scattering loss; the selection of photoresist ensures the high resolution and pattern fidelity of electron beam lithography; the process of oxygen plasma ashing can completely remove the photoresist residue, avoiding pollution and optical performance degradation; annealing at 300-500℃ can eliminate the internal stress of the cladding layer, improve the 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 realization of high-precision, high-consistency grating waveguide structure and performance.

[0033] Beneficial technical effects:

[0034] In the present application, through the structure design of double-layer cladding, double-layer grating combination and orthogonal double-direction anisotropic arrangement of grating combination, combined with the optimization of each layer material, the thickness, the refractive index difference and high-precision preparation process, a high diffraction efficiency grating waveguide structure is prepared. In the high diffraction efficiency grating waveguide structure, the first grating structure unit and the first unit substructure serve as the primary scatterer to couple the incident light into the waveguide; the second unit substructure further modulates the light field, and the energy directional transmission is realized through the interference effect of the double-layer structure. Moreover, the smaller interval in the first direction corresponds to a higher spatial frequency, which is suitable for optical coupling perpendicular to the base layer; the larger interval in the second direction is used for lateral light expansion, which meets the requirements of different direction diffraction angles. Moreover, the advantages of the prepared grating combination not only lie in the different intervals in two directions, but also in the cooperation of the anisotropy in geometry and height with the periodic anisotropy difference between the intervals in two directions; the former provides a direction-dependent optical response, and the latter matches a specific diffraction condition. In addition, borosilicate glass, aluminosilicate glass or quartz glass as the base layer material has low expansion coefficient and high chemical stability, which ensures that the structure does not deform during long-term use; silica as the first cladding material has low refractive index and good uniformity, which reduces the light transmission loss; high refractive index materials niobium oxide, tungsten trioxide or tantalum pentoxide form a significant refractive index difference with silica, and a refractive index difference is also formed between niobium oxide, tungsten trioxide or tantalum pentoxide and rutile phase titanium dioxide, thereby enhancing the diffraction efficiency of the grating. Finally, the proportion of nitrogen and oxygen components in the silicon oxynitride used in the second cladding of the present application can be adjusted artificially to optimize the waveguide mode matching. The high diffraction efficiency grating waveguide structure realizes high diffraction efficiency and wide polarized light control, while suppressing high-order diffraction and reducing light field leakage. BRIEF DESCRIPTION OF DRAWINGS

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

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

[0037] Figure 3 is an operation schematic diagram of the preparation step S1 of the high diffraction efficiency grating waveguide structure of the present application under a side view angle;

[0038] Figure 4 is an operation schematic diagram of the preparation steps S2-S3 of the high diffraction efficiency grating waveguide structure of the present application under a side view angle;

[0039] Figure 5 is an operation schematic diagram of the preparation steps S4-S6 of the high diffraction efficiency grating waveguide structure of the present application under a side view angle;

[0040] Figure 6is a side view, the preparation step S7 of the high diffraction efficiency grating waveguide structure of the application is shown in the figure.

[0041] The reference numerals are: 1, substrate layer; 2, first cladding layer; 3, grating combination; 4, first grating structure unit; 5, second grating structure unit; 51, first unit substructure; 52, second unit substructure; 6, second cladding layer. DETAILED DESCRIPTION

[0042] In order to make the technical problems, technical solutions and beneficial effects of the present application more clear, the present application will be further described in detail below in conjunction with the embodiments. However, it should not be understood as limiting the scope of the present application to the following examples. Without departing from the above-mentioned method idea of the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0043] The terms used in the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application.

[0044] The present application provides a high diffraction efficiency grating waveguide structure, which comprises:

[0045] The substrate layer 1;

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

[0047] The grating combination 3 array is attached to one surface of the first cladding layer 2, and the grating combination 3 array comprises a plurality of grating combinations 3;

[0048] The second cladding layer 6 covers the grating combination 3; wherein the grating combination 3 comprises 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 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, the second grating structure unit 5 comprises 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 side of the sidewall surface of the second unit substructure 52 is combined with one side of the sidewall surface of the first grating structure unit 4.

[0049] In the grating waveguide structure provided in the application, the first grating structure unit 4 and the first unit substructure 51 serve as primary scatterers to couple the incident light into the waveguide; the second unit substructure 52 further modulates the light field, and the energy is directionally transmitted through the interference effect of the double-layer structure. Moreover, the refractive index difference between the cladding material and the grating material is large, and strong optical contrast can be formed. The larger the refractive index difference between the cladding material and the grating material, the stronger the reflection and diffraction effect of light at the grating interface, and the higher the coupling efficiency of the light field and the grating structure, thereby reducing the energy loss of zero-order transmitted light and further improving the diffraction efficiency.

[0050] In a possible implementation, the arrangement direction of the grating combination 3 includes a first direction and a second direction, and the two directions are perpendicular to each other; the arrangement interval of the grating combination 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 substrate layer 1; and the second direction is the extension direction of the long side of the substrate layer 1.

[0051] In a possible implementation, the arrangement interval of the grating combination 3 in the first direction is 200-350 nm, and the arrangement interval in the second direction is 400-700 nm; the height of the first grating structure unit 4, the first unit substructure 51, and the second unit substructure 52 is 100-150 nm.

[0052] In the application, the smaller interval in the first direction corresponds to a higher spatial frequency, which is suitable for light coupling perpendicular to the substrate layer 1; and the larger interval in the second direction is used for lateral light expansion, which meets the requirement of different diffraction angles. The asymmetric arrangement can suppress high-order diffraction modes, reduce crosstalk, and improve the energy concentration of the main diffraction order, thereby improving the diffraction efficiency. Moreover, the height of the grating in the application matches the penetration depth of light, which can enhance the interaction between light and the grating, and at the same time avoid scattering loss caused by excessively high structures.

[0053] In a possible implementation, the thickness of the substrate 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 the application, the thickness of the substrate layer 1 provides sufficient mechanical support and avoids structural weakness caused by excessive thinness; the thickness design of the first cladding layer 2 can ensure the effective limitation of the light field in the waveguide structure and reduce the leakage of the light field to the substrate layer 1; and the thickness design of the second cladding layer 6 can further cover the grating combination 3 to form a complete waveguide channel, optimize the transmission of the light field, and reduce multimode interference.

[0055] In one possible implementation, the material used for the base layer 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 base layer 1, which has low expansion coefficient and high chemical stability, ensuring that the structure does not deform in long-term use; silicon dioxide is used as the material of the first cladding layer 2, which has low refractive index and good uniformity, reducing the light transmission loss; the high-refractive-index materials niobium oxide, tungsten trioxide or tantalum pentoxide form a significant refractive index difference with silicon dioxide, and a refractive index difference is also formed 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 material used for the second cladding layer 6 can be adjusted by artificially adjusting the proportion of nitrogen and oxygen components therein, thereby optimizing the waveguide mode matching.

[0057] The front view of the high-diffraction-efficiency grating waveguide structure is shown in Figure 1 , and the top view is shown in Figure 2 .

[0058] The following will specifically describe a preparation method of a high-diffraction-efficiency grating waveguide structure provided by the application in combination with the accompanying drawings and different embodiments.

[0059] Embodiment 1

[0060] A high-diffraction-efficiency grating waveguide structure, and a preparation method thereof, are provided.

[0061] S1: as shown in Figure 3 , the base layer 1 is immersed in acetone, taken out after ultrasonic treatment for 25 min, vacuum dried at 90°C, and then silicon dioxide is attached to the upper and lower surfaces of the base layer 1 by the reaction of silane and oxygen through plasma-enhanced chemical vapor deposition under the conditions of 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 min, to obtain the first cladding layer 2;

[0062] S2: as shown in Figure 4 , a layer of niobium oxide 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 a photoresist polymethyl methacrylate is applied;

[0063] S3: Etching to obtain a first grating structure unit 4 using electron beam lithography technology;

[0064] S4: As Figure 5 As shown, on the surface of the first cladding layer 2 to which the first grating structure unit 4 is attached, rutile phase titanium dioxide is obtained by sputtering deposition to adhere to the sidewalls of the first grating structure unit 4 and cover the first grating structure unit 4, and then coated with photoresist polymethyl methacrylate;

[0065] S5: E-beam lithography is then used to etch the second grating structure unit 5, that is, to obtain a grating assembly 3 with two different spacings in different directions;

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

[0067] S7: As Figure 6 As shown, finally, plasma enhanced chemical vapor deposition is also used. Under the conditions of deposition temperature of 250°C, 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 6 is deposited on the grating structure unit by the reaction of silane with mixed gas of oxygen and nitrogen. After annealing, the high diffraction efficiency grating waveguide structure is obtained.

[0068] Example 2

[0069] A high diffraction efficiency grating waveguide structure, the preparation method of which comprises the following steps:

[0070] S1: If Figure 3 As shown, the substrate layer 1 is immersed in anhydrous ethanol, ultrasonicated for 20 minutes, taken out, and vacuum-dried at 80°C. Then, plasma-enhanced chemical vapor deposition is performed 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 minutes. Silicon dioxide is attached to the upper and lower surfaces of the substrate layer 1 through the reaction of silane and oxygen to obtain the first cladding layer 2;

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

[0072] S3: Etching to obtain a first grating structure unit 4 using electron beam lithography technology;

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

[0074] S5: E-beam lithography is then used to etch the second grating structure unit 5, that is, to obtain a grating assembly 3 with two different spacings in different directions;

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

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

[0077] Example 3

[0078] A high diffraction efficiency grating waveguide structure, the preparation method of which comprises the following steps:

[0079] S1: If Figure 3 As shown, the substrate layer 1 is immersed in anhydrous ethanol, ultrasonicated for 30 minutes, taken out, and vacuum-dried at 100°C. Then, plasma-enhanced chemical vapor deposition is performed 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 minutes. Silicon dioxide is attached to the upper and lower surfaces of the substrate layer 1 through the reaction of silane and oxygen to obtain the first cladding layer 2.

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

[0081] S3: Etching to obtain a first grating structure unit 4 using electron beam lithography technology;

[0082] S4: As Figure 5 As shown, on the surface of the first cladding layer 2 to which the first grating structure unit 4 is attached, rutile phase titanium dioxide is obtained by sputtering deposition to adhere to the sidewalls of the first grating structure unit 4 and cover the first grating structure unit 4, and then coated with photoresist ZEP530A;

[0083] S5: E-beam lithography is then used to etch the second grating structure unit 5, that is, to obtain a grating assembly 3 with two different spacings in different directions;

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

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

[0086] Example 4

[0087] A high diffraction efficiency grating waveguide structure, the preparation method of which comprises the following steps:

[0088] S1: If Figure 3 As shown, the substrate layer 1 is immersed in acetone, ultrasonicated for 25 minutes, taken out, and vacuum-dried at 85°C. Then, plasma-enhanced chemical vapor deposition is performed at a deposition temperature of 250°C, a working pressure of 25 Pa, a silane gas flow rate of 60 sccm, an oxygen flow rate of 250 sccm, and a deposition time of 16 minutes. Silicon dioxide is attached to the upper and lower surfaces of the substrate layer 1 through the reaction of silane and oxygen to obtain the first cladding layer 2.

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

[0090] S3: Etching to obtain a first grating structure unit 4 using electron beam lithography technology;

[0091] S4: As Figure 5 As shown, on the surface of the first cladding layer 2 to which the first grating structure unit 4 is attached, rutile phase titanium dioxide is obtained by sputtering deposition to adhere to the sidewall of the first grating structure unit 4 and cover the first grating structure unit 4, and then coated with photoresist ZEP7000;

[0092] S5: E-beam lithography is then used to etch the second grating structure unit 5, that is, to obtain a grating assembly 3 with two different spacings in different directions;

[0093] S6: using oxygen plasma ashing process, removing photoresist residues on the surface of grating assembly 3;

[0094] S7: as shown in the last also using plasma enhanced chemical vapor deposition, in the condition of deposition temperature 250℃, working pressure 25Pa, silane gas flow 60sccm, oxygen gas flow 250sccm, no nitrogen, deposition time 10min, depositing second cladding layer 6 on grating structure unit by reaction of silane and oxygen, after annealing treatment, obtaining the high diffraction efficiency grating waveguide structure. Figure 6

[0095] Embodiment 5

[0096] A high diffraction efficiency grating waveguide structure, the preparation method comprising the following steps:

[0097] S1: as shown in the drawing, immersing substrate layer 1 in anhydrous ethanol, taking out after ultrasonic treatment for 20min, vacuum drying at 95℃, then through plasma enhanced chemical vapor deposition, in the condition of deposition temperature 280℃, working pressure 40Pa, silane gas flow 90sccm, oxygen flow 450sccm, deposition time 18min, depositing silicon dioxide on the upper and lower surfaces of substrate layer 1 by reaction of silane and oxygen, obtaining first cladding layer 2; Figure 3 S2: as shown in the drawing, depositing a layer of tungsten trioxide used for first grating structure unit 4 on one surface of first cladding layer 2 by sputtering, then coating photoresist polymethyl methacrylate;

[0098] Figure 4 S3: using electron beam lithography technology to etch first grating structure unit 4;

[0099] S4: as shown in the drawing, depositing rutile titanium dioxide on the surface of first cladding layer 2 with first grating structure unit 4 by sputtering, which is in contact with the sidewall of first grating structure unit 4 and covers first grating structure unit 4, then coating photoresist polymethyl methacrylate;

[0100] S5: using electron beam lithography technology to etch second grating structure unit 5, that is, obtaining grating assembly 3 with different intervals between two directions; Figure 5 S6: using oxygen plasma ashing process, removing photoresist residues on the surface of grating assembly 3;

[0101] S7: as shown in the drawing, finally also using plasma enhanced chemical vapor deposition, in the condition of deposition temperature 250℃, working pressure 25Pa, silane gas flow 60sccm, oxygen gas flow 250sccm, no nitrogen, deposition time 10min, depositing second cladding layer 6 on grating structure unit by reaction of silane and oxygen, after annealing treatment, obtaining the high diffraction efficiency grating waveguide structure.

[0102]

[0103] S7: as shown in the drawing, finally also using plasma enhanced chemical vapor deposition, in the condition of deposition temperature 250℃, working pressure 25Pa, silane gas flow 60sccm, oxygen gas flow 250sccm, no nitrogen, deposition time 10min, depositing second cladding layer 6 on grating structure unit by reaction of silane and oxygen, after annealing treatment, obtaining the high diffraction efficiency grating waveguide structure. Figure 6 ​​​As shown, finally, plasma enhanced chemical vapor deposition is also used. Under the conditions of deposition temperature 280°C, working pressure 40Pa, silane gas flow rate 90sccm, mixed gas flow rate of oxygen and nitrogen 450sccm, volume ratio of oxygen to nitrogen 75:25, and deposition time 25min, the second cladding 6 is deposited on the grating structure unit by the reaction of silane with mixed gas of oxygen and nitrogen. After annealing treatment, the high diffraction efficiency grating waveguide structure is obtained.

[0104] Example 6

[0105] A high diffraction efficiency grating waveguide structure, the preparation method of which comprises the following steps:

[0106] S1: If Figure 3 As shown, the substrate layer 1 is immersed in acetone, ultrasonicated for 25 minutes, taken out, and vacuum-dried at 90°C. Then, plasma-enhanced chemical vapor deposition is performed at a deposition temperature of 240°C, a working pressure of 35 Pa, a silane gas flow rate of 80 sccm, an oxygen flow rate of 400 sccm, and a deposition time of 12 minutes. Silicon dioxide is attached to the upper and lower surfaces of the substrate layer 1 through the reaction of silane and oxygen to obtain the first cladding layer 2.

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

[0108] S3: Etching to obtain a first grating structure unit 4 using electron beam lithography technology;

[0109] S4: As Figure 5 As shown, on the surface of the first cladding layer 2 to which the first grating structure unit 4 is attached, rutile phase titanium dioxide is obtained by sputtering deposition to adhere to the sidewall of the first grating structure unit 4 and cover the first grating structure unit 4, and then coated with photoresist ZEP7000;

[0110] S5: E-beam lithography is then used to etch the second grating structure unit 5, that is, to obtain a grating assembly 3 with two different spacings in different directions;

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

[0112] S7: As Figure 6The second cladding layer 6 is deposited on the grating structure unit by the reaction of silane and the mixed gas of oxygen and nitrogen through plasma enhanced chemical vapor deposition under the conditions of a deposition temperature of 240℃, a working pressure of 35Pa, a silane gas flow of 80sccm, a mixed gas flow of oxygen and nitrogen of 400sccm, a volume ratio of oxygen to nitrogen of 85:15, and a deposition time of 20min, and the high-refractive-efficiency grating waveguide structure is obtained after annealing treatment.

[0113] Comparative Example 1

[0114] A high-refractive-efficiency grating waveguide structure, and a preparation method thereof, includes the following steps:

[0115] S1: The substrate layer is immersed in acetone, and after ultrasonic treatment for 25min, the substrate layer is taken out and vacuum dried at 90℃, and then a first cladding layer is obtained by depositing silicon dioxide on the upper and lower surfaces of the substrate layer through the reaction of silane and oxygen through plasma enhanced chemical vapor deposition under the conditions of a deposition temperature of 250℃, a working pressure of 30Pa, a silane gas flow of 75sccm, an oxygen flow of 350sccm, and a deposition time of 15min;

[0116] S2: A layer of material used for the first grating structure unit, niobium oxide, is deposited on one surface of the first cladding layer through sputtering, and then a photoresist, polymethyl methacrylate, is applied;

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

[0118] S4: The photoresist residue on the surface of the first grating structure unit is removed using an oxygen plasma ashing process;

[0119] S5: The second cladding layer is deposited on the grating structure unit by the reaction of silane and the mixed gas of oxygen and nitrogen through plasma enhanced chemical vapor deposition under the conditions of a deposition temperature of 250℃, a working pressure of 30Pa, a silane gas flow of 75sccm, a mixed gas flow of oxygen and nitrogen of 350sccm, a volume ratio of oxygen to nitrogen of 70:30, and a deposition time of 20min, and the high-refractive-efficiency grating waveguide structure is obtained after annealing treatment.

[0120] Comparative Example 2

[0121] A high-refractive-efficiency grating waveguide structure, and a preparation method thereof, includes the following steps:

[0122] S1: immerse the substrate layer in anhydrous ethanol, take out after ultrasonicating for 30 min, vacuum dry at 100℃, then through plasma enhanced chemical vapor deposition, under the conditions of deposition temperature 300℃, working pressure 50Pa, silane gas flow 100sccm, oxygen flow 500sccm, deposition time 20min, attach silicon dioxide on the upper and lower surfaces of the substrate layer through the reaction of silane and oxygen, to obtain a first cladding layer;

[0123] S2: deposit a layer of rutile titanium dioxide on one surface of the first cladding layer through sputtering, then coat photoresist ZEP530A;

[0124] S3: etch to obtain a second grating structure unit using electron beam lithography technology;

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

[0126] S5: finally, also adopt plasma enhanced chemical vapor deposition, under the conditions of deposition temperature 300℃, working pressure 50Pa, silane gas flow 100sccm, mixed gas flow of oxygen and nitrogen 500sccm, volume ratio of oxygen and nitrogen 90:10, deposition time 30min, deposit a second cladding layer on the grating structure unit through the reaction of silane and the mixed gas of oxygen and nitrogen, and obtain the high diffraction efficiency grating waveguide structure after annealing treatment.

[0127] Comparative Example 3

[0128] A high diffraction efficiency grating waveguide structure, and a preparation method thereof, the preparation method comprising the following steps:

[0129] S1: immerse the substrate layer in acetone, take out after ultrasonicating for 25 min, vacuum dry at 90℃, then through plasma enhanced chemical vapor deposition, under the conditions of deposition temperature 240℃, working pressure 35Pa, silane gas flow 80sccm, oxygen flow 400sccm, deposition time 12min, attach silicon dioxide on the upper and lower surfaces of the substrate layer through the reaction of silane and oxygen, to obtain a first cladding layer;

[0130] S2: deposit a layer of tantalum pentoxide, which is used as the material of a first grating structure unit, on one surface of the first cladding layer through sputtering, then coat photoresist ZEP7000;

[0131] S3: etch to obtain a first grating structure unit using electron beam lithography technology;

[0132] S4: Rutilum phase titanium dioxide is deposited on the surface of the first cladding layer with the first grating structure unit by sputtering, and then photoresist ZEP7000 is coated;

[0133] S5: The second grating structure unit is etched by using electron beam lithography technology to obtain a grating combination body with the same interval in two directions;

[0134] S6: The photoresist residue on the surface of the grating combination body is removed by using oxygen plasma ashing process;

[0135] S7: Finally, the second cladding layer is deposited on the grating structure unit by using plasma enhanced chemical vapor deposition under the conditions of a deposition temperature of 240°C, a working pressure of 35Pa, a silane gas flow of 80sccm, a mixed gas flow of oxygen and nitrogen of 400sccm, a volume ratio of oxygen and nitrogen of 85:15, and a deposition time of 20min. The high-refractive-efficiency grating waveguide structure is obtained after annealing.

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

[0137] Table 1: Test results of high-refractive-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 detection data of the high-refractive-efficiency grating waveguide structures prepared in Examples 1-6 are better than those of Comparative Examples 1-3.

[0140] The reason is that the high diffraction efficiency grating waveguide structure prepared in Examples 1-6 has a smaller interval in the first direction corresponding to a higher spatial frequency, which is suitable for light coupling perpendicular to the substrate layer 1; a larger interval in the second direction for lateral light expansion, which meets the requirement of different diffraction angles. Moreover, the advantage of the prepared grating combination is not only the difference in the intervals of the two directions, but also the synergy of the anisotropy in geometry and height and the periodic anisotropy of the interval difference between the two directions; the former provides a direction-dependent optical response, and the latter matches specific diffraction conditions. In addition, borosilicate glass, aluminosilicate glass or quartz glass as the substrate layer material has low expansion coefficient and high chemical stability, ensuring that the structure does not deform during long-term use; silica as the first cladding material has low refractive index and good uniformity, reducing light transmission loss; high refractive index materials niobium oxide, tungsten trioxide or tantalum pentoxide form a significant refractive index difference with silica, and a refractive index difference is also formed between niobium oxide, tungsten trioxide or tantalum pentoxide and rutile phase titanium dioxide, thereby enhancing the diffraction efficiency of the grating. In addition, the proportion of nitrogen and oxygen in the silicon oxynitride used in the second cladding can be artificially adjusted to optimize the waveguide mode matching.

[0141] Comparative Example 1, compared with Example 1, does not construct a second grating structure unit, so it cannot produce the synergy of the anisotropy in geometry and height and the periodic anisotropy of the interval difference between the two directions, and there is no refractive index difference between niobium oxide and rutile phase titanium dioxide, so the diffraction efficiency of the final grating is significantly reduced, and the transmission loss is significantly improved.

[0142] Comparative Example 2, compared with Example 3, does not construct a first grating structure unit, so it also cannot produce the synergy of the anisotropy in geometry and height and the periodic anisotropy of the interval difference between the two directions, but the refractive index difference between rutile phase titanium dioxide and silica is higher than the refractive index difference between tungsten trioxide and silica, so the diffraction efficiency and transmission loss of the final grating are poorer than those of Example 3, but the performance of these two aspects is still better than that of Comparative Example 1.

[0143] Comparative Example 3, compared with Example 6, has the same arrangement interval in the two directions, so there is no periodic anisotropy of the interval difference between the two directions, and it cannot produce the synergy of the anisotropy in geometry and height and the periodic anisotropy of the interval difference between the two directions; but since it has complete first grating structure units and second grating structure units, the diffraction efficiency and transmission loss of the final grating are poorer than those of Example 6, but the performance of these two aspects is better than that of Comparative Examples 1 and 2.

[0144] The above results show and describe the basic principles and main features of the present application and the advantages of the present application.

[0145] Those skilled in the art should understand that the present application is not limited by the above-mentioned embodiments, the above-mentioned embodiments and descriptions in the specification are only to illustrate the principles of the present application, and various changes and improvements can be made to the present application without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present 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); A first cladding layer (2) is attached to the upper and lower surfaces of the base layer (1); A grating assembly (3) array is attached to a surface of one of the first cladding layers (2), wherein the grating assembly (3) array comprises 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 for 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); 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 a side wall surface of the second unit substructure (52) is combined with a 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); and 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 200-350 nm, and the arrangement interval in the second direction is 400-700 nm; the heights of the first grating structure unit (4), the first unit substructure (51) and the second unit substructure (52) are all 100-150 nm.

4. The high diffraction efficiency grating waveguide structure according to claim 1, wherein: 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.

5. The high diffraction efficiency grating waveguide structure according to claim 1, wherein: The material used for the base layer (1) includes any one of borosilicate glass, aluminosilicate glass and quartz glass; the material used for the first cladding (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 phase titanium dioxide; and the material used for the second cladding (6) includes any one of silicon dioxide and silicon oxynitride.

6. A method for preparing a high diffraction efficiency grating waveguide structure, characterized in that: The method for preparing the high diffraction efficiency grating waveguide structure according to any one of claims 1 to 5 comprises the following steps: S1: pre-treating the substrate layer (1), and then using plasma enhanced chemical vapor deposition, under first parameters, to attach silicon dioxide to the upper and lower surfaces of the substrate layer (1) through the reaction of silane and oxygen to obtain a first cladding layer (2); S2: a layer of material used for the first grating structure unit (4) is obtained on the surface of one of the first cladding layers (2) by sputtering deposition, and then coated with photoresist; S3: using electron beam lithography to etch a first grating structure unit (4); S4: sputtering and depositing rutile phase titanium dioxide on the surface of the first cladding layer (2) to which the first grating structure unit (4) is attached, so as to adhere to the sidewall of the first grating structure unit (4) and cover the first grating structure unit (4), and then coating with photoresist; S5: E-beam lithography is then used to etch a second grating structure unit (5), that is, a grating assembly (3) with two gratings having different spacings in two directions is obtained; S6: using an oxygen plasma ashing process to remove the photoresist residue on the surface of the grating assembly (3); S7: Finally, plasma enhanced chemical vapor deposition is used to deposit a second cladding layer (6) on the grating assembly (3) through the reaction of a mixed gas of silane, oxygen and nitrogen under the second parameter. After annealing, the high diffraction efficiency grating waveguide structure is obtained.

7. The method for preparing a high diffraction efficiency grating waveguide structure according to claim 6, wherein: The pretreatment method of the base layer (1) is as follows: the base layer (1) is immersed in anhydrous ethanol or acetone, ultrasonicated for 20 to 30 minutes, taken out, and vacuum-dried at 80 to 100°C.

8. The method for preparing a high diffraction efficiency grating waveguide structure according to claim 6, wherein: The first parameters in S1 include: deposition temperature of 200~300°C, 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 preparing a high diffraction efficiency grating waveguide structure according to claim 6, wherein: The photoresist includes any one of polymethyl methacrylate, ZEP520A, ZEP530A and ZEP7000.

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

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