CN115480329A

CN115480329A - Multi-order two-dimensional grating structure, manufacturing method thereof, optical waveguide device and AR equipment

Info

Publication number: CN115480329A
Application number: CN202110600711.2A
Authority: CN
Inventors: 徐钦锋; 马珂奇; 杜佳玮
Original assignee: Ningbo Sunny Opotech Co Ltd
Current assignee: Ningbo Sunny Opotech Co Ltd
Priority date: 2021-05-31
Filing date: 2021-05-31
Publication date: 2022-12-16

Abstract

The invention relates to a multi-order two-dimensional grating structure, a manufacturing method thereof, an optical waveguide device and AR equipment. The multi-order two-dimensional grating structure has an array set including: a plurality of first pillars disposed on a surface of a substrate and arranged in a two-dimensional periodic array, wherein each first pillar has a top surface and a bottom surface opposite to each other, the bottom surface being on the surface of the substrate; and a plurality of second pillars respectively disposed on top surfaces of the respective first pillars, wherein each of the second pillars has a top surface and a bottom surface opposite to each other, the bottom surface of the second pillar is contained within the top surface of the corresponding first pillar, and a shape of the bottom surface of the second pillar is different from a shape of the bottom surface of the corresponding first pillar. The multi-order two-dimensional grating structure can be applied to waveguide pieces, AR equipment and the like, so that the light leakage energy loss pointing to the world side in the existing waveguide pieces is effectively reduced, the energy utilization rate of the waveguide pieces is improved, and the information leakage risk is reduced.

Description

Multi-order two-dimensional grating structure, manufacturing method thereof, optical waveguide device and AR equipment

Technical Field

The present invention relates to the field of optical imaging technology, and more particularly, to a multi-order two-dimensional grating structure, a method of manufacturing the same, an optical waveguide device, and an AR apparatus.

Background

The optical waveguide sheet is a key core component in the new generation of Augmented Reality (AR) technology, combines the total reflection waveguide principle and the diffraction element to copy the extended exit pupil in the imaging system, and has become an inevitable trend of the development of the AR technology due to the advantages of large pupil, small volume, light weight and the like. In some existing schemes, a two-dimensional grating is applied to an optical waveguide lens as an optical coupling element, and at the same time, the two-dimensional grating has a two-dimensional pupil expanding function and has high compactness, but high light leakage energy loss exists at the side pointing to the world, so that the energy utilization rate is reduced, information leakage is caused, and eye contact with surrounding people is influenced.

The above disadvantages can be improved by using a multi-order two-dimensional grating, however, the manufacturing of the multi-order micro-nano structure is usually realized by multi-step alignment with high alignment precision, and generally, n photolithography steps can generate 2n steps, but it is limited by the alignment precision of photolithography tools and etching processes. And when preparing multilayer patterns with the characteristic size lower than 100nm or meeting the requirement of extremely high lamination alignment precision, both the multilayer patterns have great challenges, and the requirements of the quality, the production efficiency, the cost and the like of the multi-order two-dimensional grating are difficult to ensure.

What is described in this section is for the convenience of understanding the present application and therefore it should not be assumed that it is prior art that this section is solely for its inclusion in this section.

Disclosure of Invention

In view of the above, the present invention provides a multi-order two-dimensional grating structure, a method of manufacturing the same, an optical waveguide device, and an AR apparatus, which can solve or at least alleviate one or more of the above problems and other problems.

First, according to an aspect of the present invention, there is provided a multi-order two-dimensional grating structure having an array group including:

a plurality of first pillars disposed on a surface of a substrate and arranged in a two-dimensional periodic array, wherein each first pillar has a top surface and a bottom surface opposite to each other, the bottom surface being on the surface of the substrate; and

and a plurality of second pillars respectively disposed on the top surfaces of the respective first pillars, wherein each of the second pillars has a top surface and a bottom surface opposite to each other, the bottom surfaces of the second pillars are contained in the top surfaces of the respective first pillars, and the bottom surfaces of the second pillars have a shape different from that of the bottom surfaces of the respective first pillars.

In the multi-order two-dimensional grating structure according to the present invention, optionally, the array set further includes one or more additional arrays, where the additional arrays include:

and a plurality of third pillars respectively disposed on the base surfaces adjacent thereto, wherein each of the third pillars has a top surface and a bottom surface opposite to each other, the bottom surfaces of the third pillars are contained in the base surfaces, and the bottom surface shape of the third pillars is different from the bottom surface shape of the pillar corresponding to the base surface, and the base surface is the top surface of the second pillar in the array group or the top surface of the third pillar in another additional array.

In the multi-order two-dimensional grating structure according to the present invention, optionally, the cross-sectional shape of the first cylinder and/or the second cylinder is configured to be circular, elliptical, polygonal, or any combination thereof, and/or the bottom surface of the second cylinder is reduced in an equal proportion according to a preset reduction rate of the bottom surface of the first cylinder.

In the multi-order two-dimensional grating structure according to the present invention, optionally, the reduction ratio is in a range of 0.45-0.65.

In the multi-order two-dimensional grating structure according to the present invention, optionally, a central axis of the second cylinder is offset with respect to a central axis of the first cylinder.

In the multi-order two-dimensional grating structure according to the present invention, optionally, a bottom surface of the second cylinder is tangent with respect to a bottom surface of the first cylinder, and the tangent point is located in an offset direction of a central axis of the second cylinder with respect to a central axis of the first cylinder.

In the multi-order two-dimensional grating structure according to the invention, optionally the first and second pillars have a first height in a direction perpendicular to the surface of the substrate in the range of 30nm-65nm and a second height having a substantially comparable height to the first height, respectively.

In the multi-order two-dimensional grating structure according to the present invention, optionally, in a two-dimensional plane formed by a first dimension direction and a second dimension direction of the two-dimensional periodic array, a projection of the second cylinder in the two-dimensional plane is smaller than a projection of the corresponding first cylinder in the two-dimensional plane in at least three directions.

In the multi-order two-dimensional grating structure according to the present invention, optionally, the array groups are disposed to protrude outward or to be recessed inward from the surface of the substrate.

Secondly, according to another aspect of the present invention, there is provided an optical waveguide device, comprising an optical waveguide substrate, a coupling-in region through which incident light is coupled into the optical waveguide substrate and then coupled out through the coupling-out region, and a coupling-out region configured to have a multi-order two-dimensional grating structure as described in any one of the above.

In addition, according to still another aspect of the present invention, there is further provided an AR device including:

one or more optical waveguide devices as described above; and

and the image projection device is arranged on the light inlet side of the light waveguide device and is used for sending image light rays to be incident to the coupling-in area of the light waveguide device.

In addition, according to another aspect of the present invention, there is provided a method for manufacturing a multi-order two-dimensional grating structure, comprising the steps of:

providing a substrate; and

constructing a plurality of first pillars and a plurality of second pillars on a surface of the substrate to form an array group, wherein each of the first pillars and each of the second pillars are configured to have top and bottom surfaces opposite to each other, respectively, the bottom surfaces of the first pillars are located on the surface of the substrate and the first pillars are arranged in a two-dimensional periodic array, the second pillars are located on top surfaces of the respective corresponding first pillars, respectively, the bottom surfaces of the second pillars are contained within the top surfaces of the corresponding first pillars, and shapes of the bottom surfaces of the second pillars are different from shapes of the bottom surfaces of the corresponding first pillars.

In the method for manufacturing a multiple-order two-dimensional grating structure according to the present invention, optionally, the method further comprises the steps of:

constructing one or more additional arrays to form an array group, wherein the additional arrays are configured to include a plurality of third cylinders, each of the third cylinders has a top surface and a bottom surface opposite to each other, the third cylinders are respectively arranged on a base surface adjacent to the third cylinders, the bottom surfaces of the third cylinders are contained in the base surface, and the bottom surface of each third cylinder is different from the bottom surface of the cylinder corresponding to the base surface, and the base surface is the top surface of the second cylinder in the array group or the top surface of the third cylinder in another additional array.

In the method for manufacturing a multi-order two-dimensional grating structure according to the present invention, the array group is optionally constructed by performing the following steps at least twice and then performing etching:

depositing a substrate layer on a surface or a currently exposed surface of the substrate;

coating a photoresist layer on the substrate layer, photoetching, and depositing a mask layer; and

and removing the residual photoresist layer.

In the method for manufacturing a multi-order two-dimensional grating structure according to the present invention, the substrate layer is optionally formed by sputtering, evaporation or atomic layer deposition, and/or the material of the substrate layer comprises Si, siO2 or SiN.

In the method of manufacturing a multi-order two-dimensional grating structure according to the invention, optionally, the method further comprisesEtching the mask layer by photolithography, wherein the photolithography comprises ultraviolet lithography, electron beam lithography and nanoimprint, and/or the material of the mask layer comprises a metal material or a metal oxide material, wherein the metal material comprises Au, al, ag, ni or Cr, and the metal oxide material comprises SiO2 or TiO 2 ₂ 。

In the method of manufacturing a multi-step two-dimensional grating structure according to the present invention, a solvent is optionally used to remove the residual photoresist layer, the solvent being determined based on the type of photoresist used.

In the method of manufacturing a multi-order two-dimensional grating structure according to the invention, optionally the thickness of the substrate layer corresponds to a first height or a second height, the first height and the second height being the height of the first pillars and the second pillars, respectively, in a direction perpendicular to the surface of the substrate.

The multi-order two-dimensional grating structure provided by the invention has the advantages that the whole structure is compact, the preparation process is efficient, and particularly, the depth of each grating order can be accurately controlled, so that the high-quality level is achieved. Be applied to waveguide piece, AR equipment etc. with this multistage two-dimensional grating structure, can effectively reduce the light leak energy loss of the directional world side that exists in the current waveguide piece to promote the energy utilization of waveguide piece, reduce the information and reveal the risk, promote the duration of AR equipment etc.. The scheme of the invention is very suitable for large-scale manufacturing and has outstanding application value.

Drawings

The present invention will be described in further detail below with reference to the following drawings and examples, but it should be understood that these drawings are merely illustrative for purposes of explanation and are not necessarily drawn to scale.

Fig. 1a and 1b are schematic partial top views of array groups in an embodiment of a multi-order two-dimensional grating structure according to the present invention and schematic perspective structures of a first pillar and a corresponding second pillar.

Fig. 2a and 2b are schematic partial top views of array groups and schematic perspective structures of a first column and a corresponding second column in an embodiment of a multi-order two-dimensional grating structure according to the present invention.

Fig. 3 shows a schematic diagram of the generation of both outward transmitted diffraction orders T1 and inward reflected diffraction orders R1 of incident image light as it is coupled out via an outcoupling region applying an example of a multi-order two-dimensional grating structure according to the invention in an embodiment of an optical waveguide device according to the invention.

Fig. 4 shows the coupling-out diffraction efficiency curves of the respective transmission diffraction orders T1 and reflection diffraction orders R1 of the s-polarized light and the p-polarized light transmitted in the coupling-out region of the embodiment of the optical waveguide device shown in fig. 3 as a function of the incident angle.

FIG. 5 is a flow chart of an embodiment of a method of fabricating a multi-order two-dimensional grating structure according to the present invention.

Fig. 6a to 6j respectively show schematic side views of different processes in manufacturing a multi-level two-dimensional grating structure by using an embodiment of the method of the present invention.

Detailed Description

First, it should be noted that the following will illustrate, by way of example, the multi-order two-dimensional grating structure and the manufacturing method thereof, the steps, configurations, features, advantages, and the like of the optical waveguide device and the AR apparatus according to the present invention, however, all the descriptions should not be construed as limiting the present invention in any way. In this document, the terms "first", "second", "third" are used merely for descriptive purposes and are not intended to imply a sequence, relative importance, etc. they are used in a descriptive sense, the term "substantially" is intended to include insubstantial errors associated with measurement of a particular quantity, for example, the range of ± 8%, ± 5%, or ± 2% of a given value may be included, the term "multi-step" is meant to be third or more, the terms "upper", "lower", "top", "bottom", "horizontal", "vertical", and derivatives thereof are intended to be associated with the orientation in the drawings, and it is to be understood that the invention may assume various alternative orientations.

Furthermore, to any single feature described or implicit in an embodiment herein or shown or implicit in the drawings or any single feature, the invention still allows any combination or subtraction between these features (or their equivalents) to proceed without any technical impediment, thus covering further embodiments according to the invention. In addition, for the sake of brevity, identical or similar parts and features may be indicated only at one or several places in the same drawing, and general items known to those skilled in the art are not described in detail herein.

The present invention first provides a multi-order two-dimensional grating structure, which is exemplarily illustrated by two specific examples shown in fig. 1a, 1b, 2a and 2 b. Specifically, the multi-step two-dimensional grating structure is configured to have an array group protruding outwards or recessed inwards from the surface of the substrate, such array group can be formed by two or more series of different cylinder structures, and the specific configuration can be designed according to the practical application requirements, the processing easiness, the manufacturing cost and the like. It should be understood that a cylindrical shape is intended in this context in a broad sense, for example covering numerous types of configurations, such as prismatic tables, oblique prisms, cylinders, etc., which may be relatively simple or rather complex, with these different structural shapes being used to vary the energy distribution of the different diffraction orders of the two-dimensional grating without altering the light transmission path.

By way of illustration, referring to fig. 1a and 1b (or fig. 2a and 2 b), an array block may be constructed to have a plurality of first pillars 11 and a plurality of second pillars 12 in a general case. In this context, the present invention is not specifically limited to the specific number, arrangement, configuration, etc. of the pillars in the array set, unless otherwise specified. For example, the sectional shapes of the first and

second cylinders

11 and 12 may be selectively provided as desired, and they may be configured, for example, as a circle, an ellipse, a polygon, or any combination thereof, for example, fig. 1a and 1b show that the first and

second cylinders

11 and 12 are configured to have a hexagonal sectional shape and a quadrangular sectional shape, respectively, and fig. 2a and 2b show that the first and

second cylinders

11 and 12 are configured to have a relatively large hexagonal sectional shape and a relatively small hexagonal sectional shape, respectively.

In the array group, each first pillar 11 has a top surface 111 and a bottom surface 112 opposite to each other, and each second pillar 12 similarly has a top surface 121 and a bottom surface 122 opposite to each other. The first pillars 11 are arranged on the substrate 10 in a two-dimensional periodic array, with a bottom surface 112 of each first pillar 11 lying on the surface 101 of the substrate 10, the substrate 10 being generally flat and may be made of a suitable material such as silicon, quartz or other.

As for the second columns 12, they are respectively disposed on the top surfaces 111 of the respective corresponding first columns 11, the bottom surface 122 of each second column 12 is contained in the top surface 111 of the corresponding first column 11, and the shape of the bottom surface 122 is set to be different from the shape of the bottom surface 112 of the corresponding first column 11, so that a gradual stepped configuration can be formed. For example, as an alternative embodiment, the bottom surface 122 of the second column 12 may be configured to be scaled down at a predetermined reduction rate according to the bottom surface 112 of the first column 11, which is exemplarily illustrated in fig. 2a and 2 b. In practical applications, the range of the reduction ratio may be optionally set to 0.45-0.65, but it may also adopt any other suitable value to meet different application requirements.

As an alternative, it is conceivable to offset the central axis of the second cylinder 12 with respect to the central axis of the first cylinder 11, and the offset direction may be, for example, the direction in which the optical grating is coupled. In an alternative case, the bottom surface of the second cylinder 12 may be made tangent with respect to the bottom surface of the first cylinder 11, and the tangent point is located in the offset direction of the central axis of the second cylinder 12 with respect to the central axis of the first cylinder 11. Further, in an alternative case, the first and

second columns

11 and 12 may be disposed to have first and second heights H1 and H2, respectively, in a direction perpendicular to the surface of the substrate 10. For the first height H1, it may be selected in the range of 30nm-65nm, or any other suitable value. For the second height H2, it is generally considered to be set to have a height substantially equivalent to the first height H1. That is, as will be understood by those skilled in the art, the second height H2 does not differ too much from the first height H1 as long as the heights are made to be approximately equivalent in the height dimension.

In addition, as an alternative, for example, as shown in fig. 1b and fig. 2b, the multi-step two-dimensional grating structure may be configured such that, in a two-dimensional plane formed by the first dimension direction and the second dimension direction of the two-dimensional periodic array formed by the first cylinders 11, the projection of the second cylinders 12 in the two-dimensional plane is smaller than the projection of the corresponding first cylinders 11 in the two-dimensional plane at least in three directions (for example, the transmission direction of the light coupled into the grating, the transmission direction of the turning light on the left side of the grating, the transmission direction of the turning light on the right side of the grating, and the like), so that a gradient of height decrease may be formed in these directions.

It should be noted that if the higher the order of the columnar array in the multi-order two-dimensional grating structure, the closer the side view is to the triangle, the more prominent the blaze characteristic is, so in the solution of the present invention, by creating a series of different columns (such as the first column 11 and the second column 12 described above), it is possible to simulate a gradual step structure, and thus, a grating structure that tends to approach the desired triangle pattern can be obtained. Blazed gratings have high reflection diffraction efficiency and low transmission diffraction efficiency because the optical paths of light reaching the diffraction maxima of each periodic cell are identical, resulting in constructive superposition.

For the multi-order two-dimensional grating of the invention, since the side views of the grating in the two main image beam expansion directions have the constructive superposition effect brought by the above steps, the light leakage energy loss pointing to the world side can be reduced, and the energy utilization rate pointing to the human eye side can be increased. For example, as shown in fig. 3, when incident image light is coupled out toward the viewer's eye E in the direction of the arrow in the figure, each time the image light is coupled out, an outward transmitted diffraction order T1 (i.e., the world side) and an inward reflected diffraction order R1 (i.e., the user side) are generated simultaneously. In general, more image light needs to be directed to the user side than to the world side, which increases the risk of information leakage because image light directed to the world side is not only wasteful in nature, but also causes other people around the viewer to unnecessarily see the output content. The multi-order two-dimensional grating structure can achieve the beneficial and obvious technical effects.

With continued reference to fig. 4, there is shown the coupled-out diffraction efficiency curves of the transmitted s-polarized light, the transmitted p-polarized light, the respective transmitted T1 and reflected R1 diffraction orders as a function of the angle of incidence for the coupled-out grating in the third-order hexagonal array exemplified by fig. 2a and 2 b. As shown in fig. 4, the diffraction efficiency of the reflection order R1 facing the user side can reach 2-3 times of the transmission order T1 of the world side in the same polarization state. Therefore, by adopting the scheme of the invention, the reflection level R1 can be greatly enhanced, so that the diffraction efficiency of the user side is improved, the transmission level T1 is effectively inhibited, and a quite good effect is realized.

In the introduction above, a three-order two-dimensional grating structure implemented according to the invention has been described with some specific examples. It will be appreciated that the present invention allows, in addition to the above embodiments, further provision of one or more additional arrays in which one or more series of third pillars may be provided.

Specifically, the third pillars (not shown) may be respectively disposed on the base surfaces adjacent thereto, for example, on the top surfaces of the existing second pillars 12 in the multi-step two-dimensional grating structure to form a configuration having three different arrays of pillar periods, or may be disposed on the top surfaces of the third pillars in another additional array to form a configuration such as four, five or more different arrays of pillar periods, which is very advantageous in sufficiently and flexibly satisfying any possible different requirements.

It also has a top and a bottom surface opposite each other for each third pillar, and each bottom surface is contained within the base surface corresponding thereto, and is shaped differently from the bottom surface of the corresponding pillar corresponding to the base surface (i.e. the second pillar 12 described above or the third pillar in another additional array), thereby forming a graduated stepped configuration.

It is to be noted that, unless otherwise specified, the present invention is also applicable to the third column as set forth in the foregoing description concerning the structural configuration, arrangement, and the like of the first column or the second column, and therefore, the description will not be repeated here.

The basic structure, arrangement, advantages and the like of the multi-order two-dimensional grating structure according to the present invention are described above, and details regarding specific construction formation, implementation and the like of the substrate, the first pillar, the second pillar and the third pillar therein will be described later in conjunction with the manufacturing method of the multi-order two-dimensional grating structure according to the present invention.

Based on the multi-order two-dimensional grating structure, the invention further provides an optical waveguide device. The optical waveguide device comprises an optical waveguide substrate, a coupling-in region and a coupling-out region, which can be constructed with a multi-order two-dimensional grating structure according to the invention. When the incident light is coupled into the optical waveguide substrate through the coupling-in region of the optical waveguide device, the incident light is coupled out through the coupling-out region. In practice, the optical waveguide device may be configured in any suitable shape, such as a sheet, a block, etc.

The multi-order two-dimensional grating structure is applied to the optical waveguide device, so that the whole structure is more compact, the multi-order two-dimensional grating structure has high quality level, and the loss of transmission diffraction light energy pointing to the world side, which is usually existed in the existing waveguide piece, can be reduced, so that the energy utilization rate is improved, and the risk of information leakage is reduced.

Furthermore, the present invention also provides an AR apparatus on which one or more of the above-discussed optical waveguide devices according to the present invention can be arranged, and by disposing the image projecting device on the light incident side of the optical waveguide device so as to transmit image light thereto to be incident to the coupling-in region of the optical waveguide device. Therefore, the AR equipment has the advantages of easily realizing two-dimensional pupil expansion, large field angle range and the like, and particularly can effectively reduce transmitted diffracted light to improve energy efficiency, enhance the endurance capacity of the AR equipment and improve the product competitiveness.

In addition, the invention also provides a method for manufacturing the multi-order two-dimensional grating structure. With reference to fig. 5, the following basic steps of the manufacturing method according to the invention are shown:

first, a substrate may be provided in step S11, and the substrate may be made of any suitable material such as silicon, quartz, etc. according to the application requirements.

Then, in step S12, a plurality of first pillars and a plurality of second pillars, each having a top surface and a bottom surface, may be constructed on the surface of the substrate to form an array group. Referring to the foregoing, the bottom surface of each first pillar is located on the surface of the substrate provided in step S11, and the first pillars are arranged in a two-dimensional periodic array, and the second pillars are respectively located on the top surfaces of the corresponding first pillars, and the bottom surface of each second pillar is not only contained in the top surface of the corresponding first pillar, but also has a shape different from the shape of the bottom surface of the corresponding first pillar, so that a multi-step two-dimensional grating structure can be manufactured.

As an alternative, it is possible to consider adding additional processing steps in the method of the invention, alone or in combination.

For example, in some embodiments, a step for constructing one or more additional arrays may be further added to the already constructed array group formed by the first and second pillars, for example, such additional arrays may be formed by continuing to construct a series of third pillars, thereby forming a grating structure of more than three orders.

Specifically, the third column may be constructed on the top surface of the second column such that the bottom surface of the third column is contained within the top surface of the corresponding second column and the bottom surface of the third column has a shape different from the shape of the bottom surface of the corresponding second column. Of course, it is also possible to subsequently build one or more additional arrays on top of the completed additional array, i.e., build the third pillars in the next additional array on the top surface of the third pillars in the previous additional array, with the bottom surface of the next third pillar on the top surface of the adjacent previous third pillar, and with the bottom surface of the next third pillar having a shape different from the shape of the bottom surface of the previous third pillar.

As another example, in some embodiments, any feasible process step may be considered to have a mask layer between the surface of the substrate and the bottom surface of the first pillars, as will be described in more detail below with reference to fig. 6i and the like.

In order to facilitate a better understanding of the technical solution of the present invention, the method content of the present invention is further explained by the specific examples of fig. 6a to 6j, however, it should be understood that the following description is only exemplary and should not form any limitation to the present invention, i.e. the present invention fully allows to use other processes, operation steps, etc. to make a multi-order two-dimensional grating structure.

First, in fig. 6a, a substrate 10 is shown as a starting substrate, which may use a suitable material such as silicon, quartz, etc., and generally takes a shape such as a flat plate. Subsequently, based on the substrate 10, cyclic processes such as substrate layer deposition, photoresist layer coating, photolithography processing, mask layer deposition, residual photoresist layer removal and the like may be performed in sequence as required, and each processing period may generate one grating step, that is, more cyclic processes may be performed as required to obtain more grating steps.

Next, illustrated in fig. 6b, a mask layer S may be first deposited over the surface 101 of the substrate 10, which is to resist subsequent ion beam etching. As for the material, thickness, deposition mode, etc. of the mask layer S, it can be set according to the requirements of the specific application, for example, it can use metal material such as Au, al, ag, ni or Cr, or use any suitable material such as metal oxide material such as SiO2 or TiO; the deposition method may use, for example, sputtering, evaporation, atomic layer deposition, or the like.

Fig. 6c-6e and fig. 6f-6h show two cycles of the process, respectively. As shown in these figures, the first step in each cyclic process, i.e. the deposition of the substrate layer T, is shown in fig. 6c and 6 f. In particular, the substrate layer T may be deposited on a surface or currently exposed surface of the substrate 10 (e.g., a deposited mask layer S or substrate layer T), which may use materials such asSuch as sputtering, evaporation or atomic layer deposition. The substrate layer T may have a good etch selectivity and its available materials may include, but are not limited to, for example, si, siO ₂ SiN, etc. As regards the thickness of the substrate layer T, it may correspond to the aforementioned first height of the first columns or to the second height of the second columns.

In fig. 6d and 6g, a second step during each cyclic process is shown, i.e. a further deposition of an etching mask layer S on the substrate layer T. In particular, the substrate layer T may be coated with a photoresist layer P and then processed using a photolithography method (e.g., uv lithography, e-beam lithography, or nanoimprinting) to deposit a mask layer S on the basis thereof after completing the photolithography. The mask layer S may generally employ a metal material, a metal oxide material, or the like as described above, and has a thickness generally not greater than 100nm, for example, between several nanometers and several tens of nanometers.

The third step during each cycle of the process, namely the removal of the photoresist layer P remaining after the above operation, is shown in fig. 6e and 6 h. This may be removed by using a solvent, which may correspond to the type of photoresist used in the previous process, to remove the remaining photoresist layer P. For example, when a ZEP520 type photoresist is used in electron beam lithography, it is considered to use, for example, NMP (N-Methylpyrrolidone) or the like as a resist removing treatment solvent.

Fig. 6i is further illustrated after fig. 6h, that is, for the structure shown in fig. 6h, a single etching process may be performed to remove the portion not covered by the mask layer, so as to obtain the array group structure formed by the first pillars and the second pillars shown in fig. 6i, in which the mask layer S remaining between the surface 101 of the substrate 10 and the bottom surfaces 111 of the first pillars 11 is also shown. In the process, one-time etching treatment is simplified, so that the depth of each step in the grating is allowed to be accurately controlled, the side wall of the cylinder with higher verticality can be realized, the quality of a corner is improved, and the high-quality multi-step two-dimensional grating is promoted to be obtained.

Fig. 6i to 6j show that further etching removes the mask layer S adjacent to the surface 101 of the substrate 10, however this process is not essential and is an alternative. For example, when the mask layer S is a metal material, it may be easier to be etched away for storage, since it may be easier to be oxidized in some cases. Of course, it may be advantageous in some cases to not employ a step of removing the mask layer as shown in fig. 6j, which would therefore simplify one processing step, help to increase production efficiency and save costs.

As described above, a multi-order two-dimensional grating structure according to the present invention can be obtained by a series of process steps as exemplarily described in connection with the above figures. For example only, in practical applications, the manufactured product shown in fig. 6i to 6j may be used as a template for imprinting a sub-template, and then the sub-template is used to imprint the waveguide sheet, so as to finally obtain the same grating structure on the surface of the waveguide sheet as shown in fig. 6i or 6 j.

The multi-order two-dimensional grating structure, the manufacturing method thereof, the optical waveguide device and the AR apparatus according to the present invention are explained in detail above by way of examples only, which are provided only for illustrating the principles of the present invention and the embodiments thereof, and not for limiting the present invention, and those skilled in the art may make various modifications and improvements without departing from the spirit and scope of the present invention. Accordingly, all equivalents are intended to be included within the scope of this invention and defined in the claims which follow.

Claims

1. A multi-order two-dimensional grating structure having an array set, the array set comprising:

2. The multi-order two-dimensional grating structure of claim 1, wherein the array set further comprises one or more additional arrays, the additional arrays comprising:

3. The multi-order two-dimensional grating structure of claim 1, wherein the cross-sectional shape of the first and/or second pillars is configured as a circle, an ellipse, a polygon, or any combination thereof, and/or the bottom surface of the second pillar is scaled down at a predetermined scaling rate according to the bottom surface of the first pillar.

4. The multi-order two-dimensional grating structure of claim 3, wherein the demagnification ratio is in a range of 0.45-0.65.

5. The multi-order two-dimensional grating structure of claim 1, wherein a central axis of the second cylinder is offset with respect to a central axis of the first cylinder.

6. The multi-order two-dimensional grating structure of claim 1, wherein the bottom surface of the second cylinder is tangent with respect to the bottom surface of the first cylinder, and the tangent point is located in an offset direction of a central axis of the second cylinder with respect to a central axis of the first cylinder.

7. The multi-order two-dimensional grating structure of claim 1, wherein the first and second pillars have a first height and a second height, respectively, in a direction perpendicular to the surface of the substrate, the first height being in a range of 30nm-65nm, the second height having a substantially comparable height to the first height.

8. The multi-order two-dimensional grating structure of claim 1, wherein, in a two-dimensional plane formed by a first dimension direction and a second dimension direction of the two-dimensional periodic array, a projection of the second cylinder in the two-dimensional plane is smaller than a projection of the corresponding first cylinder in the two-dimensional plane in at least three directions.

9. The multi-order two-dimensional grating structure according to any one of claims 1-8, wherein the array groups are arranged to protrude outwards or to be recessed inwards from the surface of the substrate.

10. An optical waveguide device comprising an optical waveguide substrate, a coupling-in area through which incident light is coupled into the optical waveguide substrate and then coupled out through the coupling-out area, and a coupling-out area, wherein the coupling-out area is configured to have a multi-order two-dimensional grating structure as set forth in any one of claims 1 to 9.

11. An AR device, the AR device comprising:

one or more optical waveguide devices according to claim 10; and

12. A method for manufacturing a multi-order two-dimensional grating structure is characterized by comprising the following steps:

providing a substrate; and

13. The method for fabricating a multi-order two-dimensional grating structure according to claim 12, further comprising the steps of:

constructing one or more additional arrays to form an array group, wherein the additional arrays are configured to include a plurality of third cylinders, each of the third cylinders has a top surface and a bottom surface opposite to each other, the third cylinders are respectively arranged on a base surface adjacent to the third cylinders, the bottom surfaces of the third cylinders are contained in the base surface, and the bottom surface of the third cylinders is different from the bottom surface of the cylinder corresponding to the base surface, and the base surface is the top surface of the second cylinder in the array group or the top surface of the third cylinder in another additional array.

14. The method for fabricating a multi-order two-dimensional grating structure according to claim 12 or 13, wherein the array set is fabricated by performing the following steps at least twice and then etching:

and removing the residual photoresist layer.

15. A method of manufacturing a multi-order two-dimensional grating structure according to claim 14, wherein the substrate layer is formed using sputtering, evaporation or atomic layer deposition and/or the material of the substrate layer comprises Si, siO2 or SiN.

16. The method for fabricating a multi-order two-dimensional grating structure according to claim 14, wherein the lithography comprises uv lithography, e-beam lithography and nanoimprinting, and/or the material of the mask layer comprises a metal material or a metal oxide material, the metal material comprising Au, al, ag, ni or Cr, the metal oxide material comprising SiO2 or TiO ₂ 。

17. The method of claim 14, wherein a solvent is used to remove the remaining photoresist layer, the solvent being determined based on the type of photoresist used.

18. The method of fabricating a multi-order two-dimensional grating structure according to claim 14, wherein the thickness of the substrate layer corresponds to a first height or a second height, the first height and the second height being a height of the first pillar and the second pillar, respectively, in a direction perpendicular to the surface of the substrate.