Preparation method for volume holographic grating, and volume holographic grating, optical waveguide and display device

Abstract

A preparation method for a volume holographic grating, and a volume holographic grating, an optical waveguide and a display device. The preparation method comprises: acquiring a holographic material to be exposed, wherein said holographic material comprises a thermosetting liquid crystal material; providing a liquid crystal cell, and filling the liquid crystal cell with said holographic material; on the basis of a preset light source, exposing said holographic material in the liquid crystal cell to obtain a grating to be processed; and applying a preset electric field to said grating and heating said grating after the preset electric field has been applied thereto, so as to cure thermosetting liquid crystal molecules oriented by means of the preset electric field in said grating, thereby preparing a volume holographic grating.

Description

Fabrication method of volume holographic grating, volume holographic grating, optical waveguide and display device

[0001] This application claims priority to Chinese patent application No. 2025101053470, filed with the China National Intellectual Property Administration on January 22, 2025, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application relates to the technical field of grating fabrication, and in particular to a method for fabricating a volume holographic grating, a volume holographic grating, an optical waveguide, and a display device. Background Technology

[0003] Today, due to the superior optical performance of optical waveguides, more and more display devices are incorporating them for display purposes. Holographic gratings, with their simple fabrication process and high yield, are often used in optical waveguides. However, the free liquid crystal molecules in some holographic gratings can have different alignment orientations at different temperatures. Therefore, in some high-temperature operating environments, the alignment state of the liquid crystal molecules in the holographic grating can be easily altered, leading to a decrease in the diffraction efficiency of the holographic grating and consequently a degradation in its optical performance. Summary of the Invention

[0004] This application provides a method for fabricating a volume holographic grating, a volume holographic grating, an optical waveguide, and a display device, aiming to improve the stability of the liquid crystal molecules in the volume holographic grating at high temperatures, thereby maintaining the diffraction efficiency of the volume holographic grating and preventing the optical performance of the volume holographic grating from decaying at high temperatures.

[0005] Firstly, the method for fabricating a volume holographic grating provided in this application includes the following steps:

[0006] Obtain the holographic material to be exposed, including thermosetting liquid crystal materials;

[0007] Provide a liquid crystal cell and fill the liquid crystal cell with the holographic material to be exposed;

[0008] Based on a preset light source, the holographic material to be exposed in the liquid crystal cell is exposed to obtain the grating to be processed.

[0009] A volume holographic grating is prepared by applying a preset electric field to the grating to be processed and then heating the grating after applying the preset electric field to solidify the thermosetting liquid crystal molecules in the grating after being oriented by the preset electric field.

[0010] Secondly, this application also provides a volume holographic grating, which is prepared by the method for preparing a volume holographic grating as provided in the first aspect.

[0011] Thirdly, this application also provides an optical waveguide, which includes at least the volume holographic grating provided in the second aspect.

[0012] Fourthly, this application also provides a display device, which includes at least an optomechanical system and an optical waveguide as provided in the third aspect.

[0013] The volume holographic grating fabrication method, volume holographic grating, optical waveguide, and display device provided in this application involve adding thermosetting liquid crystal material to a holographic material to be exposed, filling the holographic material to be exposed into a liquid crystal cell, and exposing the holographic material in the liquid crystal cell to obtain a grating to be processed. Then, a preset electric field is applied to the grating to be processed to align the liquid crystal molecules in the grating. The grating to be processed after the electric field is applied is then heated to thermally solidify the aligned liquid crystal molecules, thereby fixing the alignment direction of the liquid crystal molecules. This improves the stability of the alignment state of the liquid crystal molecules in the volume holographic grating at higher temperatures, thus ensuring the diffraction efficiency of the volume holographic grating and avoiding the degradation of the optical performance of the volume holographic grating at high temperatures. Attached Figure Description

[0014] Figure 1 is a schematic flowchart of a method for fabricating a volume holographic grating according to an embodiment of this application;

[0015] Figure 2 is a schematic diagram of the molecular structure of photoinitiator 1173 provided in an embodiment of this application;

[0016] Figure 3 is a schematic diagram of the molecular structure of the photoinitiator TPO provided in another embodiment of this application;

[0017] Figure 4 is a schematic diagram of the molecular structure of photoinitiator 184 provided in another embodiment of this application;

[0018] Figure 5 is a schematic diagram of the molecular structure of photoinitiator 907 provided in another embodiment of this application;

[0019] Figure 6 is a schematic diagram of the molecular structure of an epoxy liquid crystal monomer provided in an embodiment of this application;

[0020] Figure 7 is a schematic diagram of the molecular structure of an epoxy liquid crystal monomer provided in another embodiment of this application;

[0021] Figure 8 is a schematic diagram of the molecular structure of an epoxy liquid crystal monomer provided in another embodiment of this application. Detailed Implementation

[0022] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. It should be noted that the following related embodiments are only some embodiments of this application, and not all of them. Other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are all within the scope of protection of this application.

[0023] The flowcharts shown in the accompanying drawings are for illustrative purposes only and do not necessarily include all content and operations / steps, nor do they necessarily need to be performed in the order described. For example, some operations / steps can be broken down, combined, or partially merged, so the actual execution order can be changed according to the actual situation.

[0024] Where there is no conflict, the embodiments of this application and the features in the embodiments can be combined with each other.

[0025] It should be noted that the liquid crystal molecules in the holographic grating provided by the related technology are mostly arranged in a direction parallel to the grating vector. In this state, the holographic grating has a high diffraction efficiency for p-polarized light. However, when the ambient temperature of the environment in which the holographic grating is located or the temperature of the holographic grating itself rises to a certain level, the arrangement of liquid crystal molecules in the holographic grating is prone to change from a state parallel to the grating vector to a disordered state, which leads to a decrease in the diffraction efficiency of the holographic grating for p-polarized light.

[0026] The volume holographic grating fabrication method provided in this application can stabilize the arrangement state of liquid crystal molecules in the volume holographic grating, thereby enabling the liquid crystal molecules in the fabricated volume holographic grating to maintain a highly ordered arrangement state over a wide temperature range, thus ensuring the diffraction efficiency of the volume holographic grating and avoiding the degradation of the optical performance of the volume holographic grating at high temperatures.

[0027] Referring to Figure 1, the method for fabricating a volume holographic grating according to an embodiment of this application may include steps S101 to S104. Each step will be described and elaborated below.

[0028] S101. Obtain the holographic material to be exposed, including thermosetting liquid crystal material.

[0029] For example, the holographic material to be exposed can be used to prepare a holographic surface with diffraction properties, thereby realizing the fabrication of a volume holographic grating. Specifically, the holographic material to be exposed may include a thermosetting liquid crystal material, which can form a structure with certain stability at a certain temperature, thereby maintaining the stability of the liquid crystal molecule arrangement state.

[0030] In some embodiments, the thermosetting liquid crystal material may include an epoxy-organic amine.

[0031] In the specific implementation process, the epoxy-organic amine component can be prepared by adding a portion of organic amines with different functions to the epoxy liquid crystal monomer component, so as to promote the crosslinking density in the reaction. It should be understood that thermosetting liquid crystal materials can also include epoxy liquid crystal monomers without organic amines and other monomers or oligomers, so that the liquid crystal molecules can be heated and cured after orientation.

[0032] In some embodiments, the holographic material to be exposed can be obtained in the following manner: S1011, the holographic material to be exposed is prepared according to the provided thermosetting liquid crystal material and prepolymer; wherein, the prepolymer may include a thermosetting accelerator, a photopolymerization monomer and a photoinitiator.

[0033] In the specific implementation process, the holographic material to be exposed can be obtained by mixing thermosetting liquid crystal materials with prepolymers. Specifically, the prepolymer can include, but is not limited to, thermosetting accelerators, photopolymerizing monomers, photoinitiators, and thermosetting crosslinking agents. Among them, photopolymerizing monomers are reactants capable of undergoing polymerization reactions, and can include, but are not limited to, liquid crystal monomers and photopolymerizing liquid crystals. Specifically, the molecular structure of photopolymerizing liquid crystals has a liquid crystal core and reactive functional groups at the ends. These functional groups can form a polymer network through photopolymerization, thus becoming a liquid crystal polymer. Before polymerization, the photopolymerizing liquid crystals are arranged in a periodic and ordered manner along the alignment layer, and then photopolymerization occurs to obtain the grating to be processed.

[0034] For example, photoinitiators may include, but are not limited to, photoinitiator 1173, photoinitiator TPO, photoinitiator 184, photoinitiator 907, etc.

[0035] Among them, the photoinitiator 1173 has the chemical name 2-hydroxy-2-methyl-1-phenyl-1-propanone, and its chemical formula is C6H5COC(CH3)2OH, and its structure is shown in Figure 2.

[0036] The photoinitiator TPO has the chemical name 2,4,6-trimethylbenzoyl-diphenylphosphine oxide and its chemical formula is C. 22 H 21 O2P, the structure of which is shown in Figure 3.

[0037] Photoinitiator 184 has the chemical name 1-hydroxycyclohexylphenyl ketone and its chemical formula is C. 13 H 16 O2, the structure of which is shown in Figure 4.

[0038] Photoinitiator 907 has the chemical name 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, and its chemical formula is C0. 13 H 17 NO2S has the structure shown in Figure 5.

[0039] In other implementations, the prepolymer may also include an inert liquid crystal material. Thermosetting liquid crystal materials, inert liquid crystal materials, and photopolymerizable monomers can polymerize under the action of a photoinitiator to form a polymer, which can then be further cured under the action of a thermosetting accelerator.

[0040] In some embodiments, the holographic material to be exposed may include liquid crystal units located in photopolymerization monomers and / or thermosetting accelerators.

[0041] It should be noted that liquid crystal units are structural units in the molecular structure that can promote the formation of liquid crystal states in molecules, so that at least thermosetting liquid crystal materials can form liquid crystal states during the reaction process.

[0042] In some embodiments, the aforementioned S1011 may include: mixing thermosetting liquid crystal material and prepolymer in a preset ratio to obtain the holographic material to be exposed.

[0043] For example, thermosetting liquid crystal materials, photopolymerizable monomers, photoinitiators, and thermosetting accelerators can be mixed in a certain proportion to obtain the desired holographic material to be exposed.

[0044] It should be understood that the aforementioned holographic material to be exposed can be adjusted according to actual needs. For example, inert liquid crystal materials and thermosetting crosslinking agents can be added to the holographic material to be exposed according to actual needs, and there are no restrictions on this.

[0045] In the specific implementation process, the thermosetting liquid crystal material can include epoxy liquid crystal monomers and non-liquid crystal polyfunctional epoxy monomers; the epoxy liquid crystal monomers, non-liquid crystal polyfunctional epoxy monomers, inert liquid crystal materials, photopolymerizable monomers, photoinitiators, thermosetting accelerators and thermosetting crosslinking agents are mixed in a preset ratio to obtain the holographic material to be exposed.

[0046] It should be noted that the preset ratio can be flexibly set according to the actual situation. For example, the preset ratio can be set to 1:1 for each component. Of course, the preset ratio can also be set to other values. This application does not limit the specific value of the preset ratio.

[0047] S102, Provide a liquid crystal cell and fill the liquid crystal cell with the holographic material to be exposed.

[0048] In practice, the liquid crystal cell can control the arrangement of liquid crystal molecules based on the driving voltage (the applied electric field), thereby changing the optical properties of the liquid crystal.

[0049] S103. Based on a preset light source, the holographic material to be exposed in the liquid crystal cell is exposed to obtain the grating to be processed.

[0050] For example, by exposing the holographic material to be exposed, the monomers in the holographic material to be exposed can undergo photopolymerization, and the monomers in the coherent dark area can diffuse to the coherent bright area, while the photoinert components can diffuse to the coherent dark area, thereby forming a holographic grating structure and obtaining the grating to be processed.

[0051] For example, exposure can be performed under a polarization interference light field with a period of 1µm. At this time, the thermosetting liquid crystal molecules in the holographic grating to be exposed will undergo a photopolymerization reaction, thereby obtaining the grating to be processed.

[0052] It should be noted that exposure parameters such as the wavelength and exposure dose of the preset light source can be set according to the actual situation to obtain the grating to be processed.

[0053] S104. Apply a preset electric field to the grating to be processed and heat the grating to be processed after the preset electric field is applied to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field, so as to obtain a volume holographic grating.

[0054] For example, after obtaining the grating to be processed, an electric field of preset intensity and direction can be applied to the grating, causing the liquid crystal molecules in the grating to align with a certain degree of order under the influence of the electric field. This reduces light scattering of the prepared volume holographic grating and improves diffraction efficiency. After the liquid crystal molecules align with this order, the grating is heated and cured, causing the liquid crystal molecules in the grating to form a liquid crystal network with a certain orientation structure. This achieves the fixation of the ordered liquid crystal molecules and improves the stability of the prepared volume holographic grating. Therefore, even at high temperatures, the arrangement of the internal liquid crystal molecules in the prepared volume holographic grating will not be destroyed, thus ensuring the stability of the volume holographic grating under high-temperature conditions.

[0055] In the holographic gratings provided by related technologies, the liquid crystal molecules inside are aligned along the direction parallel to the grating vector at room temperature, resulting in high diffraction efficiency for p-polarized light. However, when the holographic grating is at a high temperature, exceeding the temperature corresponding to the liquid crystal clearing point, the arrangement of the liquid crystal molecules in the holographic grating changes from a state parallel to the grating vector to a disordered state, leading to a decrease in the diffraction efficiency of the holographic grating for p-polarized light. In contrast, the volume holographic grating prepared by the method provided in this application, through thermosetting treatment that polymerizes the liquid crystal molecules or binds them to the formed intermolecular covalent cross-linked network, forms a liquid crystal network with a certain orientation structure, achieving ordered fixation of the liquid crystal molecules. Thus, even when the volume holographic grating is at a high temperature, the liquid crystal molecules in the volume holographic grating can still maintain their original state, ensuring high stability of the volume holographic grating under high-temperature conditions.

[0056] In some embodiments, a preset electric field can be applied to the grating to be processed in the following manner: an electric field of preset direction and preset intensity is applied to the grating to be processed to orient the liquid crystal molecules in the grating to be processed.

[0057] For example, when an electric field is applied to the grating to be processed, the liquid crystal molecules in the grating are driven by a voltage in a specific direction, and the pointing vector is arranged along the voltage direction, thereby promoting the orderly arrangement of the liquid crystal molecules and completing the orientation of the liquid crystal molecules.

[0058] After aligning the liquid crystal molecules, an electric field is maintained on the grating to be processed, and the grating under the influence of the electric field is heated to complete the heat curing of the grating and obtain a volume holographic grating. It should be understood that after the volume holographic grating is obtained by heat curing the grating to be processed, the arrangement of the liquid crystal molecules in the volume holographic grating is fixed. At this point, even if no electric field is applied, the arrangement of the liquid crystal molecules in the volume holographic grating will not change, and the arrangement of the liquid crystal molecules in the volume holographic grating can still be maintained within a certain temperature range, thus obtaining a stable volume holographic grating.

[0059] In some embodiments, the grating to be processed after the preset electric field is applied can be heated in the following manner: the grating to be processed after the preset electric field is applied is heated to a first temperature within a preset time to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field.

[0060] For example, within a preset time period, the grating to be processed after applying a preset electric field can be heated to a first temperature so that the thermosetting liquid crystal molecules in the grating to be processed react, thereby connecting the fragments of liquid crystal molecules into a polymer, and thus completing the curing of the liquid crystal molecules.

[0061] In the specific implementation process, the grating to be processed may also include inert liquid crystal molecules. During the heating process, the thermosetting liquid crystal molecules can react to become polymers, while the inert liquid crystal molecules will be affected by the thermosetting liquid crystal molecules. Under the interaction between molecules, the inert liquid crystal molecules can also be fixed, thereby fixing all the liquid crystal molecules in the grating to be processed and realizing the curing of liquid crystal molecules.

[0062] In some embodiments, the first temperature is higher than the second temperature, where the second temperature is the temperature of the holographic material to be exposed during the exposure process.

[0063] For example, the first temperature at which the grating to be processed is heated can be much higher than the second temperature at which the holographic material to be exposed is exposed, so as to ensure the orderly phase separation of the liquid crystal phase and the photopolymer during the exposure process, thereby achieving the curing of the liquid crystal and the photopolymer.

[0064] In a specific embodiment, the first temperature can be greater than or equal to 50°C and less than or equal to 150°C.

[0065] In the above embodiments, by applying an electric field to the grating to be processed, the orientation of each liquid crystal molecule in the prepared volume holographic grating is made the same, thereby reducing the light scattering intensity of the holographic polymer material and improving the diffraction efficiency of the volume holographic grating. During the application of the electric field, the grating to be processed is heated and cured, so that the arrangement state of the internal liquid crystal molecules of the prepared volume holographic grating will not be destroyed in a high-temperature environment, thereby improving the thermal stability of the volume holographic grating. This allows the volume holographic grating to maintain a high light diffraction efficiency in a high-temperature environment (above the clearing point of the liquid crystal monomer), thus avoiding the optical performance degradation of the volume holographic grating at high temperatures.

[0066] In some embodiments, the method for fabricating the volume holographic grating of this application can be performed in the following manner.

[0067] (1) Obtain epoxy liquid crystal monomer, non-liquid crystal polyfunctional epoxy monomer, inert liquid crystal, thermosetting accelerator, photopolymerization monomer and photoinitiator to obtain the holographic material to be exposed.

[0068] (2) Add the above materials into the provided liquid crystal cell.

[0069] (3) The holographic material to be exposed in the liquid crystal cell is exposed under a polarization interference light field with a period of 1 μm at a wavelength of 457 nm and an exposure dose of 0.5 J / cm. 2 At this point, the photoinitiator absorbs photon energy to generate free radicals, which in turn triggers the polymerization reaction of monomers to generate polymers. The monomers in the coherent dark region diffuse into the coherent bright region. At the same time, photoinert components (liquid crystals, thermosetting accelerators, etc.) diffuse into the coherent dark region to form a grating structure, so as to obtain the grating to be processed.

[0070] (4) The liquid crystal cell is driven by a working voltage of 3V to apply an electric field of a certain intensity to the grating to be processed. When the liquid crystal cell is driven by voltage, the liquid crystal molecules in the grating to be processed are driven by voltage in a specific direction and the pointing vector is arranged along the voltage direction.

[0071] (5) Maintain voltage to drive the liquid crystal cell and use a hot stage to heat the liquid crystal cell, thereby heating the grating to be processed to solidify the liquid crystal molecules arranged in the grating to be processed. The heating temperature range is 50℃-150℃ and the heating time is between 2min-60min, so that the liquid crystal molecules in the grating to be processed form polymers and / or form cross-linked networks to achieve fixation.

[0072] (6) After the heating process is completed, the applied voltage is removed to obtain a volume holographic grating.

[0073] It should be understood that since the liquid crystal molecules in the fabricated volume holographic grating are solidified and no longer have the ability to move, the director will no longer change with temperature. This maintains the arrangement state of the liquid crystal molecules in the volume holographic grating under high temperature conditions, thereby ensuring the diffraction efficiency of the volume holographic grating under high temperature conditions and avoiding the optical performance degradation of the volume holographic grating under high temperature conditions. At the same time, since the heating is carried out under the action of an electric field, the orientation of the liquid crystal molecules is the same during the heating process. This makes the orientation of each liquid crystal molecule micro-region in the fabricated volume holographic grating completely identical, thereby improving the diffraction efficiency of the volume holographic grating.

[0074] In some embodiments, the epoxy liquid crystal monomers of this application can be prepared in the manner described below.

[0075] Example 1:

[0076] (1) Using a round-bottom bottle as a container, add 2.1g of weighed N,N'-dicyclohexylcarbodiimide (10.17mmol) into the container.

[0077] (2) Add 0.62 g (5 mmol) of methylhydroquinone and 2.8 g (10 mmol) of 4-(3-((3-methyloxetyl)methoxypropoxy)benzoic acid to the container.

[0078] (3) Add 40 mL of dichloromethane as a solvent, place the container in an ice bath and stir, and add 0.12 g (1 mmol) of 4-dimethylaminopyridine as a base. Stir for 0.5 hours and then transfer to room temperature.

[0079] (4) After reacting at room temperature for 16 hours, white solid RM1 was obtained by column chromatography.

[0080] It should be noted that the white solid RM1 prepared in Example 1 is an epoxy liquid crystal monomer, and its molecular structure is shown in Figure 6. The yield of RM1 prepared by the above method is 78%.

[0081] Example 2:

[0082] (1) Using a round-bottom bottle as a container, add 2.1g of weighed N,N'-dicyclohexylcarbodiimide (10.17mmol) into the container.

[0083] (2) Add 0.62 g (5 mmol) of methylhydroquinone to the container.

[0084] (3) Add 40 mL of dichloromethane as a solvent and place the container in an ice bath and stir.

[0085] (4) Add 0.69g (5mmol) of 4-hydroxybenzoic acid dropwise over 12 hours.

[0086] (5) Add 0.12 g (1 mmol) of 4-dimethylaminopyridine as a base, stir in an ice bath for 0.5 hours, then transfer to room temperature and react for 16 hours.

[0087] (6) Place the container back in an ice bath and add 1.4 g (5 mmol) of a mixed solution (10 mL) of 4-(3-((3-methyloxecyclobutyl)methoxypropoxy)benzoic acid and dichloromethane. Return the container to room temperature and continue the reaction for 16 hours. The white solid was obtained by column chromatography.

[0088] It should be understood that the white solid obtained in Example 2 is an epoxy liquid crystal monomer, the molecular structure of which is shown in Figure 7. The yield of RM2 prepared by the above method is 59%.

[0089] Example 3:

[0090] (1) Using a round-bottom bottle as a container, add 2.1g of weighed N,N'-dicyclohexylcarbodiimide (10.17mmol) into the container.

[0091] (2) Add 0.67 g (5 mmol) of 2,5-dihydroxybenzonitrile and 2.8 g (10 mmol) of 4-(3-((3-methyloxetyl)methoxypropoxy)benzoic acid to the container.

[0092] (3) Add 40 mL of dichloromethane as a solvent and place the container in an ice bath and stir.

[0093] (4) Add 0.12 g (1 mmol) of 4-dimethylaminopyridine as a base, keep it in an ice bath and stir for 0.5 hours, then transfer it to room temperature.

[0094] (5) React at room temperature for 16 hours, and then separate by column chromatography to obtain a white solid.

[0095] It should be understood that the white solid RM3 prepared in Example 3 is an epoxy liquid crystal monomer, and its molecular structure is shown in Figure 8. The yield of RM3 prepared by the above method is 83%.

[0096] It should be noted that those skilled in the art can prepare the corresponding epoxy liquid crystal monomers according to the preparation methods provided in any of the above embodiments, and no limitations are imposed here.

[0097] This application also provides a volume holographic grating, wherein the volume holographic grating can be fabricated using the volume holographic grating fabrication method in any of the above embodiments. Therefore, this volume holographic grating can achieve the beneficial effects that the volume holographic grating fabrication method provided in the embodiments of this application can achieve, as detailed in the foregoing embodiments, and will not be repeated here.

[0098] This application also provides an optical waveguide, wherein the optical waveguide may include at least a waveguide substrate and a diffraction microstructure. The waveguide substrate may include, but is not limited to, resin and glass, and the diffraction microstructure may be the volume holographic grating in the above embodiments. Therefore, the optical waveguide can achieve the beneficial effects that the volume holographic grating fabrication method provided in the embodiments of this application can achieve, as detailed in the previous embodiments, which will not be repeated here.

[0099] This application also provides a display device, wherein the display device may include at least an optomechanical system and the optical waveguide provided in the above embodiments; therefore, the display device can also achieve the beneficial effects that the volume holographic grating fabrication method provided in the embodiments of this application can achieve, as detailed above, and will not be repeated here.

[0100] In specific implementation, display devices may include, but are not limited to, AR (Augmented Reality) glasses, VR (Virtual Reality) glasses, AR helmets and VR helmets and other near-eye display devices, as well as HUD (head-up display devices).

[0101] The above description is merely a specific embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for fabricating a volume holographic grating, wherein, include: Obtain a holographic material to be exposed, wherein the holographic material to be exposed includes a thermosetting liquid crystal material; A liquid crystal cell is provided, and the holographic material to be exposed is filled into the liquid crystal cell; Based on a preset light source, the holographic material to be exposed in the liquid crystal cell is exposed to obtain the grating to be processed. A preset electric field is applied to the grating to be processed, and the grating to be processed after the preset electric field is applied is heated to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field, thereby obtaining a volume holographic grating.

2. The method for fabricating a volume holographic grating as described in claim 1, wherein, The heating treatment of the grating to be processed after the preset electric field is applied includes: Within a preset time period, the grating to be processed after the preset electric field is applied is heated to a first temperature to solidify the thermosetting liquid crystal molecules in the grating to be processed after being oriented by the preset electric field.

3. The method for fabricating a volume holographic grating as described in claim 2, wherein, The first temperature is higher than the second temperature, where the second temperature is the temperature of the holographic material to be exposed when the exposure process is performed.

4. The method for fabricating a volume holographic grating as described in claim 2, wherein, The first temperature is greater than or equal to 50°C and less than or equal to 150°C.

5. The method for fabricating a volume holographic grating as described in claim 1, wherein, The thermosetting liquid crystal material includes epoxy-organic amine.

6. The method for fabricating a volume holographic grating as described in claim 1, wherein, The thermosetting liquid crystal material includes epoxy liquid crystal monomers.

7. The method for fabricating a volume holographic grating as described in claim 1, wherein, The thermosetting liquid crystal material includes a non-liquid crystal polyfunctional epoxy monomer.

8. The method for fabricating a volume holographic grating as described in any one of claims 1-7, wherein, The acquisition of the holographic material to be exposed includes: The holographic material to be exposed is prepared according to the provided thermosetting liquid crystal material and prepolymer, wherein the prepolymer includes a thermosetting accelerator, a photopolymerization monomer and a photoinitiator.

9. The method for fabricating a volume holographic grating as described in claim 8, wherein, The photoinitiator includes photoinitiator 1173, the chemical name of which is 2-hydroxy-2-methyl-1-phenyl-1-propanone.

10. The method for fabricating a volume holographic grating as described in claim 8, wherein, The photoinitiator includes photoinitiator TPO, the chemical name of which is 2,4,6-trimethylbenzoyl-diphenylphosphine oxide.

11. The method for fabricating a volume holographic grating as described in claim 8, wherein, The photoinitiator includes photoinitiator 184, the chemical name of which is 1-hydroxycyclohexylphenyl ketone.

12. The method for fabricating a volume holographic grating as described in claim 8, wherein, The photoinitiator includes photoinitiator 907, the chemical name of which is 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholino)-1-propanone.

13. The method for fabricating a volume holographic grating as described in claim 8, wherein, The prepolymer also includes a thermosetting crosslinking agent.

14. The method for fabricating a volume holographic grating as described in claim 8, wherein, The prepolymer also includes an inert liquid crystal material.

15. The method for fabricating a volume holographic grating as described in claim 8, wherein, The holographic material to be exposed includes liquid crystal units, which are located in the photopolymerization monomer or the thermosetting accelerator.

16. The method for fabricating a volume holographic grating as described in claim 8, wherein, The preparation of the holographic material to be exposed based on the provided thermosetting liquid crystal material and prepolymer includes: The thermosetting liquid crystal material and the prepolymer are mixed in a preset ratio to obtain the holographic material to be exposed.

17. The method for fabricating a volume holographic grating as described in any one of claims 1-7, wherein, Applying a preset electric field to the grating to be processed includes: An electric field with a preset direction and preset intensity is applied to the grating to be processed in order to orient the liquid crystal molecules in the grating.

18. A volume holographic grating, wherein, The volume holographic grating is prepared by the method for preparing a volume holographic grating as described in any one of claims 1-17.

19. An optical waveguide, wherein, The optical waveguide includes the volume holographic grating as described in claim 18.

20. A display device, wherein, The display device includes at least an optomechanical system and an optical waveguide as described in claim 19.

Images