A two-dimensional grating preparation method and a diffractive grating waveguide device thereof

Abstract

The application provides a two-dimensional grating preparation method and a diffractive grating waveguide device, and the two-dimensional grating preparation method comprises the following steps: determining a setting scheme of two grating vectors of a two-dimensional grating based on two known first basic grating vectors and second basic grating vectors of the two-dimensional grating; determining grating design optimization parameters of the two-dimensional grating, including a grating period and a grating line direction, according to the setting scheme of the two grating vectors of the two-dimensional grating; and preparing the two-dimensional grating according to the grating design optimization parameters of the two-dimensional grating. The two-dimensional grating preparation method provided by the application is helpful to realize the balance between the coupling-out image energy efficiency and the average brightness uniformity of the coupling-out image of the two-dimensional grating, and improve the degree of freedom of the two-dimensional grating preparation process.

Description

Technical Field

[0001] This invention relates to the field of diffraction grating technology, specifically to a method for fabricating a two-dimensional grating and its diffraction grating waveguide device. Background Technology

[0002] Augmented Reality (AR) technology refers to providing users with additional information in the real world through certain technical means (i.e., "enhancement"). This technology organically integrates images from the virtual world with scenes from the real world, providing users with richer information and an immersive experience by deeply integrating the calculated information with the real world.

[0003] Augmented reality (AR) technology can be implemented through many hardware platforms, with wearable AR devices offering the most immersive experience. AR glasses, as a type of wearable AR device, guide light into the eyes through the microstructures on the lens surface, providing a convenient way to achieve AR. Currently, mature AR glasses lens technologies mainly include prism solutions, birdbath solutions, freeform surface solutions, off-axis holographic lens solutions, and diffraction grating waveguide solutions. Among these, the diffraction grating waveguide solution is widely recognized as the mainstream AR glasses lens solution due to its advantages such as small size and light weight, large eye movement range, large field of view, and mass production feasibility.

[0004] Diffraction grating waveguides can increase the range of eye movement through two-dimensional pupil expansion, thereby achieving a strong sense of immersion and a good visual experience. There are currently two existing two-dimensional pupil expansion schemes using diffraction grating waveguides: One-dimensional grating waveguide scheme: such as Figure 1 As shown, a coupling grating 2, a bend grating 3, and a coupling grating 4 are respectively disposed on the waveguide substrate 1. The coupling grating, bend grating, and coupling grating are all one-dimensional gratings. The light emitted by the optomechanical system is coupled into the waveguide substrate through the coupling grating and propagates through total internal reflection. It achieves two-dimensional pupil expansion through the combined action of the bend grating and the coupling grating, and achieves image formation by coupling out the light through the coupling grating.

[0005] Two-dimensional grating waveguide schemes: such as Figure 2 As shown, a coupling grating 2 and a coupling grating 4 are respectively set on the waveguide substrate 1. The coupling grating is a two-dimensional grating. The light emitted by the optomechanical system is coupled into the waveguide substrate through the coupling grating and propagates through total internal reflection. It then passes through the coupling grating to achieve two-dimensional pupil expansion and light coupling imaging.

[0006] The two-dimensional grating waveguide scheme, since it does not require a bend grating, has a larger exit pupil region (light coupling region) and higher space utilization, making it an ideal scheme for two-dimensional pupil expansion using diffraction grating waveguides.

[0007] A two-dimensional grating is composed of grating structural units arranged periodically along a two-dimensional direction. Each grating structural unit can be decomposed into two grating vectors, two grating periods, and two grating line directions.

[0008] The existing fabrication process for two-dimensional gratings has low degrees of freedom, and the energy distribution of two-dimensional gratings in different diffraction directions is not easy to control, making it impossible to achieve a balance between the energy efficiency of the coupled image and the uniformity of the average brightness of the coupled image. Summary of the Invention

[0009] To overcome the shortcomings of the prior art, the present invention provides a method for fabricating a two-dimensional grating and a diffraction grating waveguide device thereof.

[0010] This invention is achieved through the following technical solution: This invention provides a method for fabricating a two-dimensional grating, comprising the following steps: The scheme for setting the two grating vectors of a two-dimensional grating is determined based on two known first and second fundamental grating vectors; The grating design optimization parameters of the two-dimensional grating are determined based on the setting scheme of the two grating vectors. The grating design optimization parameters include the grating period and the grating line direction; wherein, the grating period includes the first grating period and the second grating period, and the grating line direction includes the first grating line direction and the second grating line direction. The two-dimensional grating is prepared based on the grating design optimization parameters of the grating.

[0011] Furthermore, the scheme for determining the setting of the two grating vectors of the two-dimensional grating based on the two known first and second basic grating vectors includes the following steps: Based on two known first and second fundamental grating vectors of a two-dimensional grating, various design schemes for the two grating vectors of a two-dimensional grating are obtained; The setting scheme for the two grating vectors of a two-dimensional grating is determined from various design schemes for the two grating vectors.

[0012] Furthermore, based on two known first and second fundamental grating vectors of the two-dimensional grating, various design schemes for the two grating vectors of the two-dimensional grating are obtained, including the following steps: Based on the principle of grating vector synthesis, various design schemes for the two grating vectors of a two-dimensional grating can be obtained by replacing the first and / or second basic grating vectors of a two-dimensional grating with other grating vectors.

[0013] Furthermore, based on the principle of grating vector synthesis, various design schemes are obtained by replacing the first and / or second basic grating vectors of a two-dimensional grating with other grating vectors to obtain the two grating vectors of the two-dimensional grating, including: Based on the principle of grating vector synthesis, the first grating vector is used to replace the first basic grating vector, and the first grating vector and the second basic grating vector are used as the first design scheme of the two grating vectors of the two-dimensional grating. Based on the principle of grating vector synthesis, the second basic grating vector is replaced by the second grating vector, and the first basic grating vector and the second grating vector are used as the second design scheme of two grating vectors of a two-dimensional grating; Based on the principle of grating vector synthesis, the third grating vector is used to replace the first basic grating vector and the fourth grating vector is used to replace the second basic grating vector. The third and fourth grating vectors are used as the third design scheme of the two grating vectors of the two-dimensional grating.

[0014] Furthermore, determining the setting scheme of the two grating vectors of the two-dimensional grating from various design schemes includes the following steps: For two-dimensional gratings with various design schemes, the diffraction energy distribution of the two-dimensional gratings in different regions was measured, and the measurement results of the diffraction energy distribution of the two-dimensional gratings with various design schemes in different regions were recorded. For two-dimensional gratings with various design schemes, the ease or difficulty of fabrication process is evaluated based on the fabrication process parameters of the two-dimensional gratings, and the evaluation results of the ease or difficulty of fabrication process for two-dimensional gratings with various design schemes are recorded. Based on the measurement results of the diffraction energy distribution in different regions of two-dimensional gratings with various design schemes, and the evaluation results of the ease of fabrication process, the setting scheme of the two grating vectors of the two-dimensional grating is determined from various design schemes of the two grating vectors of the two-dimensional grating.

[0015] Furthermore, determining the grating design optimization parameters of the two-dimensional grating based on the setting scheme of the two grating vectors includes the following steps: The first and second grating line directions of the two-dimensional grating are determined based on the vector directions of the two grating vectors in the grating vector setting scheme. Calculate the first grating period and the second grating period of the two-dimensional grating based on the vector magnitudes of the two grating vectors in the grating vector setting scheme.

[0016] Furthermore, the direction of the first grating line of the two-dimensional grating is perpendicular to the vector direction of one of the two grating vectors in the grating vector setting scheme of the two-dimensional grating; The direction of the second grating line of the two-dimensional grating is perpendicular to the vector direction of the other grating vector in the grating vector setting scheme of the two-dimensional grating.

[0017] Furthermore, based on the vector magnitudes of the two grating vectors in the grating vector setting scheme of the two-dimensional grating, the first grating period and the second grating period of the two-dimensional grating are calculated according to the following formula:

[0018] in, This represents the numerical value of the grating vector. This indicates the grating period.

[0019] Furthermore, the two-dimensional grating is fabricated based on the grating design optimization parameters of the grating, including the following steps: Photoresist is spin-coated onto a substrate to obtain a substrate with a photoresist mask. A first beam interference exposure operation is performed on the photoresist mask on the substrate according to the first grating period and the first grating line direction to obtain a first photoresist mask with changed properties on the substrate. A second beam interference exposure operation is performed on the first photoresist mask whose properties have changed on the substrate according to the second grating period and the second grating line direction to obtain a second photoresist mask whose properties have changed on the substrate. A development operation is performed on the second photoresist mask whose properties have changed on the substrate to obtain a photoresist grating mask on the substrate, resulting in a substrate with a photoresist grating mask. The substrate with the photoresist grating mask is etched, and the residual photoresist on the substrate surface is cleaned after etching to obtain a two-dimensional grating on the substrate.

[0020] The present invention also provides a diffraction grating waveguide device, comprising a waveguide substrate, wherein the waveguide substrate is provided with an input grating and an output grating; The coupled-in grating and / or coupled-out grating are two-dimensional gratings prepared using the above-described two-dimensional grating preparation method.

[0021] The present invention also provides a diffraction grating waveguide device, comprising a waveguide substrate, wherein the waveguide substrate is provided with an insertion grating, a folding grating and an output grating; At least one of the coupled-in grating, the folding grating, and the coupled-out grating is a two-dimensional grating prepared by the above-described two-dimensional grating preparation method.

[0022] Compared with the prior art, the technical solution of the present invention has the following beneficial effects: This invention provides a method for fabricating a two-dimensional grating. First, based on two known first and second fundamental grating vectors, a setting scheme for the two grating vectors of the two-dimensional grating is determined. Then, based on the setting scheme of the two grating vectors, optimization parameters for grating design, including the grating period and grating line direction, are determined for the two-dimensional grating. The two-dimensional grating is then fabricated based on these optimization parameters. The method provided by this invention, by adjusting the energy distribution of the two-dimensional grating in different diffraction directions by changing the grating vectors, helps to achieve a balance between the energy efficiency and the average brightness uniformity of the coupled image. Furthermore, by adjusting the grating vectors, process parameters such as the grating groove shape, grating period, and grating duty cycle in the two-dimensional grating fabrication process are adjusted, thereby increasing the degree of freedom in the two-dimensional grating fabrication process. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A schematic diagram of a one-dimensional grating waveguide scheme for a diffraction grating waveguide; Figure 2 A schematic diagram of a two-dimensional grating waveguide scheme for a diffraction grating waveguide; Figure 3 This is an overall flowchart of the two-dimensional grating fabrication method of the present invention; Figure 4 A schematic diagram of the first design scheme of two grating vectors of a two-dimensional grating based on the first and second basic grating vectors; Figure 5 for Figure 4 The corresponding grating topography diagram of the two-dimensional grating; Figure 6 A schematic diagram of a second design scheme for two grating vectors of a two-dimensional grating based on a first basic grating vector and a second basic grating vector; Figure 7 for Figure 6 The corresponding grating topography diagram of the two-dimensional grating; Figure 8A schematic diagram of a third design scheme for two grating vectors of a two-dimensional grating based on the first and second basic grating vectors; Figure 9 for Figure 8 The corresponding grating topography diagram of the two-dimensional grating; Figure 10 This is a schematic diagram of the optical path of a dual-beam exposure system.

[0025] Wherein, 1-waveguide substrate, 2-coupled grating, 3-turning grating, 4-coupled grating, 5-laser, 6-first waveplate, 7-beam splitter prism, 8-second waveplate, 9-first reflecting mirror, 10-second reflecting mirror, 11-third reflecting mirror, 12-first microscope objective, 13-second microscope objective, 14-first pinhole, 15-second pinhole, 16-first collimating lens, 17-second collimating lens. Detailed Implementation

[0026] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] In this document, the terms "first," "second," and other similar words are not intended to imply any order, quantity, or importance, but are merely used to distinguish different elements. The terms "one," "a," and other similar words are not intended to indicate the existence of only one of the stated things, but rather that the description refers only to one of the stated things, which may have one or more. The terms "comprising," "including," and other similar words are intended to indicate a logical relationship, not a spatial relationship. For example, "A includes B" means that logically B belongs to A, not that spatially B is located inside A. Furthermore, the meanings of the terms "comprising," "including," and other similar words should be considered open-ended, not closed. For example, "A includes B" means that B belongs to A, but B does not necessarily constitute all of A; A may also include other elements such as C, D, and E.

[0028] In this document, the terms "embodiment," "this embodiment," "preferred embodiment," and "one embodiment" do not imply that the description applies only to one specific embodiment, but rather that such description may also be applicable to one or more other embodiments. Those skilled in the art will understand that any description made herein with respect to one embodiment can be substituted, combined, or otherwise incorporated with the descriptions in one or more other embodiments. Such substitutions, combinations, or other incorporations resulting in new embodiments are readily conceived by those skilled in the art and fall within the scope of protection of this invention.

[0029] In this description, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0030] Existing methods for fabricating two-dimensional gratings generally involve directly determining the grating period and grating line direction by setting the grating vector. With the grating vector set, the fabrication process of the two-dimensional grating has low freedom, and the energy distribution of different diffraction directions of the two-dimensional grating is not easy to control, making it impossible to achieve a balance between the energy efficiency of the coupled image and the uniformity of the average brightness of the coupled image.

[0031] To address the above problems, this invention provides a method for fabricating a two-dimensional grating, such as... Figure 3 As shown, the overall technical concept is as follows: S1 is a scheme for determining the setting of two grating vectors of a two-dimensional grating based on two known first and second basic grating vectors.

[0032] S2 determines the grating design optimization parameters of the two-dimensional grating based on the setting scheme of the two grating vectors.

[0033] The grating design optimization parameters here include the grating period and the grating line orientation.

[0034] The grating period includes a first grating period and a second grating period, and the grating line direction includes a first grating line direction and a second grating line direction.

[0035] S3 prepares a two-dimensional grating based on the grating design optimization parameters of the two-dimensional grating.

[0036] For example, step S1 above determines the setting scheme of the two grating vectors of the two-dimensional grating based on the two known first and second basic grating vectors, specifically including the following steps: S1-1 derives various design schemes for the two grating vectors of a two-dimensional grating based on two known first and second fundamental grating vectors.

[0037] The two known first and second basic grating vectors are the two initial grating vectors for preparing the two-dimensional grating. The grating period and grating line direction of the two-dimensional grating can be directly determined using these initial grating vectors.

[0038] For example, based on the principle of grating vector synthesis, by replacing the first basic grating vector and / or the second basic grating vector of a two-dimensional grating with other grating vectors, various design schemes for the two grating vectors of a two-dimensional grating can be obtained.

[0039] Specific examples, Based on the principle of grating vector synthesis, by replacing the first and / or second basic grating vectors of a two-dimensional grating with other grating vectors, the following three design schemes for the two grating vectors of a two-dimensional grating are obtained: Option 1 Based on the principle of grating vector synthesis, the first grating vector is used to replace the first basic grating vector, and the first grating vector and the second basic grating vector are used as the first design scheme of the two grating vectors of the two-dimensional grating.

[0040] like Figure 4 As shown, for two defined basic grating vectors K1 and K2 in a two-dimensional grating, according to the principle of grating vector synthesis, a first grating vector K3 is found. The first grating vector K3 and the second basic grating vector K2 are vectored together to obtain the first basic grating vector K1. The first grating vector K3 is then used to replace the first basic grating vector K1, and the first grating vector K3 and the second basic grating vector K2 are taken as the two grating vectors of the two-dimensional grating. Figure 4 (The conversion from a to b in the text). Alternatively, for two defined basic grating vectors K1 and K2 in a two-dimensional grating, according to the principle of grating vector synthesis, a first grating vector K4 is found. The first grating vector K4 and the second basic grating vector K2 are vectored together to obtain the first basic grating vector K1. The first grating vector K4 is then used to replace the first basic grating vector K1, and the first grating vector K4 and the second basic grating vector K2 are taken as the two grating vectors of the two-dimensional grating. Figure 4 (Conversion from a to c in Chinese).

[0041] like Figure 5 As shown Figure 4 The grating topography diagram of the two-dimensional grating corresponding to the first design scheme based on the first and second basic grating vectors. Figure 5 In Figures (a), (b), and (c), the shaded areas represent the raised parts of the grating, the blank areas represent the recessed parts of the grating, and G1, G2, G3, and G4 represent the grating line directions. Figure 5 Figures (a), (b), and (c) correspond to each other in sequence. Figure 4 Figures (a), (b), and (c) are shown in the image. Figure 5 As can be seen from the above, the first design scheme, which replaces the first basic grating vector with the first grating vector and uses the first grating vector and the second basic grating vector as the two grating vectors of the two-dimensional grating, can change the morphological features such as the grating groove shape and grating period.

[0042] Option 2 Based on the principle of grating vector synthesis, the second basic grating vector is replaced by the second grating vector, and the first basic grating vector and the second grating vector are used as the second design scheme of two grating vectors of a two-dimensional grating.

[0043] like Figure 6 As shown, for two defined basic grating vectors K1 and K2 in a two-dimensional grating, according to the principle of grating vector synthesis, a second grating vector K5 is found. The second grating vector K5 is vector-synthesized with the first basic grating vector K1 to obtain the second basic grating vector K2. The second grating vector K5 is then used to replace the second basic grating vector K2, and the first basic grating vector K1 and the second grating vector K5 are taken as the two grating vectors of the two-dimensional grating. Figure 6 (The conversion from a to b in the original text). Alternatively, for two defined basic grating vectors K1 and K2 in a two-dimensional grating, according to the principle of grating vector synthesis, a second grating vector K6 is found. The second grating vector K6 is vector-synthesized with the first basic grating vector K1 to obtain the second basic grating vector K2. The second grating vector K6 is then used to replace the second basic grating vector K2, and the first basic grating vector K1 and the second grating vector K6 are taken as the two grating vectors of the two-dimensional grating. Figure 6 (Conversion from a to c in Chinese).

[0044] like Figure 7 As shown Figure 6 The grating topography diagram of the two-dimensional grating corresponding to the second design scheme based on the first and second basic grating vectors. Figure 7 In Figures (a), (b), and (c), the shaded areas represent the raised parts of the grating, the blank areas represent the recessed parts of the grating, and G1, G2, G5, and G6 represent the grating line directions. Figure 7 Figures (a), (b), and (c) correspond to each other in sequence. Figure 6 Figures (a), (b), and (c) are shown in the image. Figure 7 As can be seen from the above, the second design scheme, which replaces the second basic grating vector with the second grating vector and uses the first basic grating vector and the second grating vector as the two grating vectors of the two-dimensional grating, can change the morphological features such as the grating groove shape and grating period.

[0045] Option 3 Based on the principle of grating vector synthesis, the third grating vector is used to replace the first basic grating vector and the fourth grating vector is used to replace the second basic grating vector. The third and fourth grating vectors are used as the third design scheme of the two grating vectors of the two-dimensional grating.

[0046] like Figure 8 As shown, for two defined basic grating vectors K1 and K2 in a two-dimensional grating, a third grating vector K7 and a fourth grating vector K8 are found according to the principle of grating vector synthesis. The vector synthesis of the third grating vector K7 and the fourth grating vector K8 yields the first basic grating vector K1 and the second basic grating vector K2. The third and fourth grating vectors are then used as the third design scheme for the two grating vectors of the two-dimensional grating. Figure 8 (The conversion from a to b in Chinese).

[0047] Figure 9 for Figure 8 The grating topography diagram of the two-dimensional grating corresponding to the third design scheme based on the first and second basic grating vectors. Figure 9 In Figures (a) and (b), the shaded areas represent the raised portions of the grating, and the blank areas represent the recessed portions. G1, G2, G7, and G8 indicate the directions of the grating lines. Figure 9 Figures (a) and (b) correspond to each other in turn. Figure 8 Figures (a) and (b) in the text. From... Figure 9 As can be seen, replacing the first basic grating vector with the third grating vector and replacing the second basic grating vector with the fourth grating vector, and using the third and fourth grating vectors as the two grating vectors of the two-dimensional grating, can change the morphological features such as the grating groove shape and grating period.

[0048] It should be noted that the above Figure 4 , Figure 6 as well as Figure 8 In example (a), the vector directions of the first fundamental grating vector (K1) and the second fundamental grating vector (K2) are perpendicular, so the corresponding... Figure 5 , Figure 7 as well as Figure 9 In Figure (a), the direction of the first grating line G1, which is perpendicular to the direction of K1, coincides with the direction of K2, and the direction of the second grating line, which is perpendicular to the direction of K2, coincides with the direction of K1. If Figure 4 , Figure 6 as well as Figure 8 If the vector directions of the first basic grating vector (K1) and the second basic grating vector (K2) in the example (a) are not perpendicular, the above situation will not occur.

[0049] S1-2 determines the setting scheme of the two grating vectors of the two-dimensional grating from various design schemes of the two grating vectors.

[0050] For example, S1-2-1 can measure the diffraction energy distribution of two-dimensional gratings in different regions for various design schemes, and record the measurement results of the diffraction energy distribution of two-dimensional gratings in different regions for various design schemes.

[0051] Taking the three design schemes of the two grating vectors of the two-dimensional grating mentioned above as examples, the diffraction efficiency of the three schemes of two-dimensional gratings can be simulated and tested using diffraction optics simulation software, the diffraction energy distribution of the three schemes of two-dimensional gratings in different regions can be obtained, and the measurement results of the diffraction energy distribution of the three design schemes of two-dimensional gratings in different regions can be recorded.

[0052] S1-2-2 evaluates the ease of fabrication of two-dimensional gratings from various design schemes based on fabrication process parameters, and records the evaluation results for the ease of fabrication of two-dimensional gratings from various design schemes. Process parameters used to evaluate the ease of fabrication of two-dimensional gratings may include grating period, grating groove shape, and grating duty cycle, etc.

[0053] Taking the three design schemes of the two grating vectors of the above two-dimensional grating as examples, the fabrication process difficulty of the three schemes can be evaluated, and the evaluation results of the fabrication process difficulty of the two-dimensional gratings of the three design schemes can be recorded.

[0054] Based on the measurement results of the diffraction energy distribution in different regions of two-dimensional gratings with various design schemes and the evaluation results of the ease of fabrication process, S1-2-3 determines the setting scheme of the two grating vectors of the two-dimensional grating from various design schemes.

[0055] Taking the three design schemes of the two grating vectors of the two-dimensional grating mentioned above as examples, based on the measurement results of the diffraction energy distribution of the two-dimensional grating in different regions of the three design schemes and the evaluation results of the ease of fabrication process, the setting scheme of the two grating vectors of the two-dimensional grating is determined from the three design schemes. The setting scheme of the two grating vectors of the two-dimensional grating satisfies, for example, the following conditions: the diffraction energy distribution of the two-dimensional grating is uniform in different regions, and the fabrication process of the two-dimensional grating is relatively easy.

[0056] For example, step S2 above determines the grating design optimization parameters of the two-dimensional grating based on the setting scheme of the two grating vectors, specifically including the following steps: The first and second grating line directions of the two-dimensional grating are determined based on the vector directions of the two grating vectors in the grating vector setting scheme.

[0057] Specifically, the direction of the first grating line of the two-dimensional grating is perpendicular to the vector direction of one of the two grating vectors in the grating vector setting scheme of the two-dimensional grating. The direction of the second grating line of the two-dimensional grating is perpendicular to the vector direction of the other grating vector in the grating vector setting scheme of the two-dimensional grating.

[0058] Calculate the first grating period and the second grating period of the two-dimensional grating based on the vector magnitudes of the two grating vectors in the grating vector setting scheme.

[0059] Specifically, based on the vector magnitudes of the two grating vectors in the grating vector setting scheme of the two-dimensional grating, the first grating period and the second grating period of the two-dimensional grating are calculated according to the following formula:

[0060] in, This represents the numerical value of the grating vector. This indicates the grating period.

[0061] Specifically, with , To represent the magnitudes of the two grating vectors in the grating vector setting scheme of a two-dimensional grating, then:

[0062] in, This represents the size of one of the grating vectors in the grating vector setting scheme for a two-dimensional grating. This represents the size of another grating vector in the grating vector setting scheme for a two-dimensional grating. Indicates the first grating period. This indicates the second grating period.

[0063] For example, step S3 above, which involves preparing a two-dimensional grating based on the grating design optimization parameters, specifically includes the following steps: S3-1 spin-coating photoresist onto the substrate to obtain a substrate with a photoresist mask.

[0064] The substrate is immersed in a mixed cleaning solution and cleaned with ultrasonic assistance at 70-100℃ for 1-3 hours to obtain a cleaned substrate. This cleaning process removes residual impurities from the substrate surface, ensuring its cleanliness and preventing these impurities from affecting the subsequent fabrication of the grating structure.

[0065] The upper surface of the cleaned substrate is subjected to oxygen ion ashing treatment for 5-20 minutes. Oxygen ion ashing treatment can improve the hydrophilicity of the substrate and enhance its adhesion to photoresist.

[0066] A tackifier is spin-coated onto the upper surface of the ashing substrate, and the amount of tackifier is set according to actual needs.

[0067] Photoresist is spin-coated onto the substrate after the adhesion enhancement treatment to obtain a substrate with a photoresist mask. The amount of photoresist added to the substrate is related to the spin-coating thickness of the photoresist on the substrate. There is no specific requirement for the spin-coating thickness of the photoresist on the substrate, and those skilled in the art can set it according to actual needs.

[0068] S3-2 performs a first beam interference exposure operation on the photoresist mask on the substrate according to the first grating period and the first grating line direction, and obtains a first photoresist mask with changed properties on the substrate.

[0069] Construct an exposure field for beam interference exposure operations; for example, the exposure field can be constructed using a dual-beam exposure system or a Loehn mirror exposure system.

[0070] like Figure 10 The diagram shows the optical path of a dual-beam exposure system. The incident beam emitted by laser 5 enters the first waveplate 6, and after its polarization state is adjusted by the first waveplate, it enters the beam-splitting prism 7. The beam-splitting prism 7 splits the beam into two beams. The first beam is reflected by the third mirror 11 and enters the first microscope objective 12. After being focused by the first microscope objective 12, it enters the first pinhole 14. After being filtered by the first pinhole 14, it enters the first collimating lens 16 and becomes the first parallel beam after being collimated by the first collimating lens 16. The second beam is polarized by the second waveplate 8, and after being reflected by the first mirror 9 and the second mirror 10 in sequence, it enters the second microscope objective 13. After being focused by the second microscope objective 13, it enters the second pinhole 15. After being filtered by the second pinhole 15, it enters the second collimating lens 17 and becomes the second parallel beam. The first and second parallel beams are adjusted so that the interference period of the exposure field formed by the interference of the first and second parallel beams is equal to the period of the first grating.

[0071] The substrate (sample to be exposed) with the photoresist mask is fixed in the exposure field at a first set angle (the first set angle corresponds to the direction of the first gate line) and the first beam interference exposure operation is performed to obtain a first photoresist mask with changed properties on the substrate.

[0072] S3-3 performs a second beam interference exposure operation on the first photoresist mask whose properties on the substrate have changed according to the second grating period and the second grating line direction to obtain a second photoresist mask whose properties have changed on the substrate.

[0073] For the established exposure field used for beam interference exposure operation, the first parallel beam and the second parallel beam are adjusted so that the interference period of the exposure field formed by the interference of the first parallel beam and the second parallel beam is equal to the period of the second grating.

[0074] A substrate (sample to be exposed) with a first photoresist mask having changed properties is fixed in the exposure field at a second set angle (the second set angle corresponds to the direction of the second gate line) to perform a second beam interference exposure operation, thereby obtaining a second photoresist mask with changed properties on the substrate.

[0075] S3-4 performs a development operation on the second photoresist mask whose properties have changed on the substrate, and obtains a photoresist grating mask on the substrate, thus obtaining a substrate with a photoresist grating mask.

[0076] The second photoresist mask with altered properties on the substrate is immersed in a developing solution for development. The corresponding part of the photoresist mask is eroded and dissolved by the developing solution, resulting in a substrate with a photoresist grating mask.

[0077] Taking positive photoresist as an example, After the second photoresist mask with altered properties on the substrate is immersed in a developing solution for development, the illuminated portion of the photoresist mask is eroded and dissolved by the developing solution, resulting in a substrate with a photoresist grating mask.

[0078] S3-5 etches the substrate with a photoresist grating mask, and after etching, cleans the residual photoresist on the substrate surface to obtain a two-dimensional grating on the substrate.

[0079] An ion beam etching machine is used to etch a substrate with a photoresist grating mask, and the morphology distribution of the photoresist grating mask is copied onto the substrate. After etching, the residual photoresist on the substrate surface is cleaned, and a two-dimensional grating is obtained on the substrate.

[0080] The present invention also provides a diffraction grating waveguide device, which can be implemented using the following two schemes: Diffraction grating waveguide device scheme 1: The diffraction grating waveguide device includes a waveguide substrate, on which an input grating and an output grating are disposed.

[0081] The two-dimensional gratings are prepared using the above-described two-dimensional grating preparation method, including the insertion grating and / or the output grating.

[0082] The light emitted by the optomechanical system is propagated by total internal reflection through the coupled waveguide substrate via a coupling grating, and then through the coupled-out grating to achieve two-dimensional pupil expansion and light-induced imaging.

[0083] Scheme 2 for diffraction grating waveguide device: The diffraction grating waveguide device includes a waveguide substrate, on which a coupling-in grating, a deflection grating, and a coupling-out grating are disposed.

[0084] The two-dimensional grating is prepared by the above-described two-dimensional grating preparation method, at least one of the coupling grating, the folding grating and the coupling grating.

[0085] The light emitted by the optomechanical system is coupled into the waveguide substrate by the coupling grating and propagated by total internal reflection. The two-dimensional pupil is expanded by the combination of the deflection grating and the output grating, and the light is coupled out to form an image by the output grating.

[0086] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still make modifications or equivalent substitutions to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention are within the protection scope of the claims of the present invention pending approval.

Claims

1. A method for fabricating a two-dimensional grating, characterized in that, Includes the following steps: The scheme for setting the two grating vectors of a two-dimensional grating is determined based on two known first and second fundamental grating vectors; The grating design optimization parameters of the two-dimensional grating are determined based on the setting scheme of the two grating vectors. The grating design optimization parameters include the grating period and the grating line direction; wherein, the grating period includes the first grating period and the second grating period, and the grating line direction includes the first grating line direction and the second grating line direction. The two-dimensional grating is prepared based on the grating design optimization parameters of the grating.

2. The method for fabricating a two-dimensional grating according to claim 1, characterized in that, The scheme for determining the setting of the two grating vectors of a two-dimensional grating based on two known first and second basic grating vectors includes the following steps: Based on two known first and second fundamental grating vectors of a two-dimensional grating, various design schemes for the two grating vectors of a two-dimensional grating are obtained; The setting scheme for the two grating vectors of a two-dimensional grating is determined from various design schemes for the two grating vectors.

3. The method for fabricating a two-dimensional grating according to claim 2, characterized in that, Based on two known first and second fundamental grating vectors of a two-dimensional grating, various design schemes for the two grating vectors of the two-dimensional grating are obtained, including the following steps: Based on the principle of grating vector synthesis, various design schemes for the two grating vectors of a two-dimensional grating can be obtained by replacing the first and / or second basic grating vectors of a two-dimensional grating with other grating vectors.

4. The method for fabricating a two-dimensional grating according to claim 3, characterized in that, Based on the principle of grating vector synthesis, various design schemes are obtained by replacing the first and / or second basic grating vectors of a two-dimensional grating with other grating vectors to obtain the two grating vectors of the two-dimensional grating, including: Based on the principle of grating vector synthesis, the first grating vector is used to replace the first basic grating vector, and the first grating vector and the second basic grating vector are used as the first design scheme of the two grating vectors of the two-dimensional grating. Based on the principle of grating vector synthesis, the second basic grating vector is replaced by the second grating vector, and the first basic grating vector and the second grating vector are used as the second design scheme of two grating vectors of a two-dimensional grating; Based on the principle of grating vector synthesis, the third grating vector is used to replace the first basic grating vector and the fourth grating vector is used to replace the second basic grating vector. The third and fourth grating vectors are used as the third design scheme of the two grating vectors of the two-dimensional grating.

5. The method for fabricating a two-dimensional grating according to any one of claims 2-4, characterized in that, The method for determining the setting scheme of the two grating vectors of a two-dimensional grating from multiple design schemes includes the following steps: For two-dimensional gratings with various design schemes, the diffraction energy distribution of the two-dimensional gratings in different regions was measured, and the measurement results of the diffraction energy distribution of the two-dimensional gratings with various design schemes in different regions were recorded. For two-dimensional gratings with various design schemes, the ease or difficulty of fabrication process is evaluated based on the fabrication process parameters of the two-dimensional gratings, and the evaluation results of the ease or difficulty of fabrication process for two-dimensional gratings with various design schemes are recorded. Based on the measurement results of the diffraction energy distribution in different regions of two-dimensional gratings with various design schemes, and the evaluation results of the ease of fabrication process, the setting scheme of the two grating vectors of the two-dimensional grating is determined from various design schemes of the two grating vectors of the two-dimensional grating.

6. The method for fabricating a two-dimensional grating according to claim 1, characterized in that, The process of determining the grating design optimization parameters of the two-dimensional grating based on the setting scheme of the two grating vectors includes the following steps: The first and second grating line directions of the two-dimensional grating are determined based on the vector directions of the two grating vectors in the grating vector setting scheme. Calculate the first grating period and the second grating period of the two-dimensional grating based on the vector magnitudes of the two grating vectors in the grating vector setting scheme.

7. The method for fabricating a two-dimensional grating according to claim 6, characterized in that, The direction of the first grating line of the two-dimensional grating is perpendicular to the vector direction of one of the two grating vectors in the grating vector setting scheme of the two-dimensional grating; The direction of the second grating line of the two-dimensional grating is perpendicular to the vector direction of the other grating vector in the grating vector setting scheme of the two-dimensional grating.

8. The method for fabricating a two-dimensional grating according to claim 6, characterized in that, Based on the magnitudes of the two grating vectors in the grating vector setting scheme of the two-dimensional grating, the first grating period and the second grating period of the two-dimensional grating are calculated according to the following formula: in, This represents the numerical value of the grating vector. This indicates the grating period.

9. The method for fabricating a two-dimensional grating according to claim 1, characterized in that, The fabrication of a two-dimensional grating based on the grating design optimization parameters of the grating includes the following steps: Photoresist is spin-coated onto a substrate to obtain a substrate with a photoresist mask. A first beam interference exposure operation is performed on the photoresist mask on the substrate according to the first grating period and the first grating line direction to obtain a first photoresist mask with changed properties on the substrate. A second beam interference exposure operation is performed on the first photoresist mask whose properties have changed on the substrate according to the second grating period and the second grating line direction to obtain a second photoresist mask whose properties have changed on the substrate. A development operation is performed on the second photoresist mask whose properties have changed on the substrate to obtain a photoresist grating mask on the substrate, resulting in a substrate with a photoresist grating mask. The substrate with the photoresist grating mask is etched, and the residual photoresist on the substrate surface is cleaned after etching to obtain a two-dimensional grating on the substrate.

10. A diffraction grating waveguide device, characterized in that, Includes a waveguide substrate, wherein the waveguide substrate is provided with an input grating and an output grating; The coupled-in grating and / or coupled-out grating are two-dimensional gratings prepared by any one of the two-dimensional grating preparation methods of claims 1-9.

11. A diffraction grating waveguide device, characterized in that, The waveguide substrate includes a coupling-in grating, a deflection grating, and a coupling-out grating. At least one of the coupled-in grating, the folding grating, and the coupled-out grating is a two-dimensional grating prepared by any one of the two-dimensional grating preparation methods of claims 1-9.

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