WO2024240019A1 - Crossed metasurface grating for suppressing high-order light, optical waveguide, and near-eye display device - Google Patents

Abstract

The present application relates to the technical field of diffraction optics, and provides a crossed metasurface grating for suppressing high-order light, an optical waveguide, and a near-eye display device. The crossed metasurface grating comprises at least one first grating structure and at least one second grating structure, the size of the first grating structure is larger than that of the second grating structure, and the coupling efficiency can be adjusted by changing the ratio of the sizes the two grating structures; the first grating structure and the second grating structure are of a crossed structure, a crossing angle of the first grating structure is the same as that of the second grating structure, and the crossed structure can better reduce light leakage on the outer side; the edge of the first grating structure and the edge of the second grating structure are sawtooth-shaped; in the edge of any grating structure, the distances between every two adjacent sawteeth are the same, and the sawteeth are randomly normally distributed along the vector direction of a one-dimensional grating. The sawtooth configuration is carried out for the edge of the grating structure, facilitating suppressing the high-order diffraction component of light, thereby improving the imaging quality.

Description

Fork-shaped metasurface grating, optical waveguide and near-eye display device for suppressing high-level light

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Chinese patent application No. 202310575696X, filed on May 22, 2023, and entitled “Forked metasurface grating, optical waveguide and near-eye display device for suppressing high-order light”, which is incorporated herein by reference in its entirety.

Technical Field

The present application relates to the field of diffraction optical technology, and in particular to a fork-shaped metasurface grating, optical waveguide and near-eye display device for suppressing high-order light.

Background Art

In recent years, with the rapid development of computer science, human-computer interaction technologies such as virtual reality (VR) and augmented reality (AR) based on near-eye display devices have gradually become hot applications. Depending on the interaction method, VR near-eye display devices generate a virtual environment through computers, and observers can observe, touch and interact with things in the virtual environment. The virtual environment generated by AR near-eye display devices is superimposed on the real world, and observers can interact with the real world while seeing the virtual environment, achieving the purpose of augmented reality. Therefore, AR has stronger interactive capabilities than VR, and shows a more promising development trend in education, medical care, and military.

The display system used by AR glasses on the market is a combination of various micro-displays and optical components such as prisms, free-form surfaces, BirdBath, and optical waveguides. The difference in the combination of optical components is the key to distinguishing AR display systems. Overall, the optical waveguide solution has the best development potential in terms of optical effects, appearance, and mass production prospects, and may be the only choice for AR glasses to move towards consumer level.

The mainstream of optical waveguides - diffraction optical waveguides is essentially a technology that uses diffraction grating lenses to achieve near-eye image display. Its emergence and popularity are due to the technological progress trend of optical components from millimeter level to micro-nano level, and from "three-dimensional" to "flat". However, the commonly used surface relief gratings have problems such as low diffraction efficiency, narrow field of view and large size.

In addition, diffraction waveguide technology is divided into one-dimensional expansion and two-dimensional expansion. Two-dimensional diffraction waveguide can achieve two-dimensional expansion of the exit pupil by reasonably designing the grating structure. The use of two-dimensional gratings for bidirectional pupil expansion can fully utilize the effective area of the optical waveguide. However, the development of common two-dimensional diffraction optical waveguide related technologies currently requires a breakthrough in the bottleneck of materials to improve optical parameters, because the coupling efficiency of the front and back sides of ordinary two-dimensional gratings on the market is basically the same, there is a light leakage problem, and it is easy to generate high-order diffraction components, thereby reducing the imaging quality.

Summary of the invention

The present application provides a fork-shaped metasurface grating, optical waveguide and near-eye display device for suppressing high-order light, so as to improve the outcoupling efficiency of the grating, reduce external light leakage, and suppress the high-order diffraction components of the high-order light, thereby improving the imaging quality.

The present application provides a fork-shaped metasurface grating for suppressing high-order light, comprising at least one first grating structure and at least one second grating structure; the size of the first grating structure is larger than the size of the second grating structure; the first grating structure and the second grating structure are fork-shaped structures, the crossing angle of the first grating structure is the same as the crossing angle of the second grating structure, the edge of the first grating structure and the edge of the second grating structure are serrated; in the edge of any grating structure, the distance between two adjacent serrations is the same, and each serration is randomly normally distributed along the vector direction of the one-dimensional grating.

According to a fork-shaped metasurface grating for suppressing high-order light provided in the present application, in a first grating structure, the distance between two saw teeth ranges from 5nm to 50nm, and the tooth height of the saw teeth ranges from 30nm to 700nm; in a second grating structure, the distance between two saw teeth ranges from 5nm to 100nm, and the tooth height of the saw teeth ranges from 30nm to 1000nm.

According to a fork-shaped metasurface grating for suppressing high-order light provided by the present application, the edges of the sawtooth are rectangular, arc-shaped or triangular.

According to a fork-shaped metasurface grating for suppressing high-order light provided by the present application, the first distances between adjacent first grating structures and second grating structures are equal, the second distances between two adjacent first grating structures are equal, the third distances between two adjacent second grating structures are equal, and the second distance and the third distance are equal.

According to a fork-shaped metasurface grating for suppressing high-order light provided in the present application, the value range of the first distance is 50nm to 500nm; the value range of the second distance is 100nm to 1000nm.

According to a fork-shaped metasurface grating for suppressing high-order light provided in the present application, two first primitives cross at a first angle to form a first grating structure, and two second primitives cross at the first angle to form a second grating structure; wherein the value range of the first angle is 10° to 80°.

According to a fork-shaped metasurface grating for suppressing high-order light provided by the present application, the first primitive includes A first rectangular structure stacked in sequence along a first direction and a first rectangular structure stacked in sequence along a second direction, wherein the angle between the first direction and the second direction is a first angle; in the same direction, any adjacent first rectangular structures are staggered to form a serrated edge of a first grating structure; a second element comprises a second rectangular structure stacked in sequence along the first direction and a second rectangular structure stacked in sequence along the second direction; in the same direction, any adjacent second rectangular structures are staggered to form a serrated edge of a second grating structure.

The present application also provides a two-dimensional diffraction optical waveguide, comprising a waveguide substrate, a one-dimensional coupling-in grating arranged on the surface of the waveguide substrate, and a forked metasurface grating for suppressing higher-order light as described in any of the above items; wherein the one-dimensional coupling-in grating is used to couple incident light carrying image information into the two-dimensional diffraction optical waveguide; the forked metasurface grating for suppressing higher-order light is used to diffract and expand the diffracted light from the one-dimensional coupling-in grating and transmitted in a total reflection manner in the waveguide substrate in two directions, so as to couple it out to the human eye for imaging.

According to a two-dimensional diffraction optical waveguide provided by the present application, a one-dimensional coupling grating includes a first grating column and a second grating column arranged at intervals, and the length of the first grating column is greater than the length of the second grating column; the edge of the first grating column and the edge of the second grating column are serrated, and in any grating column, the distance between two adjacent serrations is the same, and each serration is randomly normally distributed along the vector direction of the one-dimensional grating.

The present application also provides a near-eye display device, comprising a microdisplay and a two-dimensional diffraction optical waveguide as described in any one of the above items, wherein the microdisplay outputs incident light carrying image information.

The present application provides a fork-shaped metasurface grating, optical waveguide and near-eye display device for suppressing high-order light, including at least one first grating structure and at least one second grating structure, the size of the first grating structure is larger than the size of the second grating structure, and the coupling efficiency can be adjusted by changing the size ratio of the two grating structures; the first grating structure and the second grating structure are fork-shaped structures, the crossing angle of the first grating structure and the crossing angle of the second grating structure are the same, and the cross-shaped structure can better reduce the leakage of light outside; the edge of the first grating structure and the edge of the second grating structure are serrated, and the distance between two adjacent serrations in the edge of any grating structure is the same, and each serration is randomly normally distributed along the vector direction of the one-dimensional grating. By setting the edge of the grating structure to be serrated, it is beneficial to suppress the high-order diffraction components of light, thereby improving the imaging quality.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions in the present application or the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the prior art description. Obviously, the following The drawings in the description are some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

FIG1 is a schematic structural diagram of an embodiment of a fork-shaped metasurface grating for suppressing high-order light in the present application;

FIG2( a ) is a schematic diagram of the edge shape of a conventional fork-shaped grating structure, wherein the edge shape is a fork-shaped grating structure with straight edges;

FIG2( b ) is a schematic diagram of the edge shape of a conventional fork-shaped grating structure, wherein the edge shape is a fork-shaped grating structure with a curved edge;

FIG3 is a schematic diagram of a simulation of the order distribution of an existing fork-shaped grating structure in the visible light band;

FIG4 is a schematic diagram of a simulation of the order distribution of the fork-shaped grating structure of the present application in the visible light band;

FIG5 is a schematic diagram of a grating structure of the present application;

FIG6( a ) is a schematic diagram of three types of sawtooth edge primitives of the present application, wherein the sawtooth edge is a rectangular primitive;

FIG6( b ) is a schematic diagram of three types of sawtooth edge primitives of the present application, wherein the sawtooth edge is a triangle primitive;

FIG6( c ) is a schematic diagram of three types of sawtooth edge primitives of the present application, wherein the sawtooth edge is an arc-shaped primitive;

FIG7 is a schematic diagram of the distance between grating structures in a fork-shaped metasurface grating for suppressing high-order light in the present application;

FIG8 is a schematic diagram of the structure of a primitive in a fork-shaped metasurface grating of advanced light of the present application;

FIG9 is a schematic diagram of a top view of a two-dimensional diffractive optical waveguide according to an embodiment of the present invention;

FIG10 is a schematic diagram showing a cosine distribution of the lateral area of a one-dimensional coupling grating array of the present invention;

FIG. 11 is a schematic diagram of an embodiment of a one-dimensional grating sawtooth edge of the present application.

DETAILED DESCRIPTION

In order to make the purpose, technical solutions and advantages of this application clearer, the technical solutions in this application will be clearly and completely described below in conjunction with the drawings in this application. Obviously, the described embodiments are part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

The present application provides a fork-shaped metasurface grating for suppressing high-order light. Please refer to FIG. 1 , which is a schematic structural diagram of an embodiment of the fork-shaped metasurface grating for suppressing high-order light of the present application.

In this embodiment, the fork-shaped metasurface grating for suppressing high-order light includes at least one first grating structure 110 and at least one second grating structure 120 .

The size of the first grating structure 110 is larger than the size of the second grating structure 120 .

Specifically, the size of the first grating structure 110 is different from the size of the second grating structure 120. The outcoupling efficiency can be adjusted by changing the size ratio of the first grating structure 110 and the second grating structure 120. Those skilled in the art can adjust the sizes of the two grating structures according to actual needs, and this embodiment does not limit this.

Furthermore, the first grating structure 110 and the second grating structure 120 are fork-shaped structures, and the crossing angle of the first grating structure 110 is the same as the crossing angle of the second grating structure 120 . The cross-shaped structure can better reduce the light leakage at the outside.

It should be noted that the fork grating is a common optical element, and the design of the edge shape of the fork grating structure has an important influence on its performance. At present, the edge of the fork grating structure usually adopts two forms: a smooth curved edge or a neat straight edge. Please refer to Figure 2, which is a schematic diagram of the edge shape of the existing fork grating structure, wherein Figure 2 (a) is a fork grating structure with a straight edge shape, and Figure 2 (b) is a fork grating structure with a curved edge shape. The smooth curved edge design can not only reduce the scattering of light, but also make the transmission path of light on the grating surface smoother, reduce the energy loss of light, and thus improve the optical performance of the grating; the neat straight edge design can make the grating manufacturing simpler and more accurate, and make the grating repetition period more stable, thereby ensuring the consistency and repeatability of the grating light output quality, which is conducive to improving the optical performance. However, the inventors found that whether it is a straight-edge fork grating or a curved-edge fork grating, it still inevitably has the characteristics of multi-order diffraction, which is easy to produce high-order diffraction components, thereby affecting the imaging quality.

Specifically, in the visible light band, the order distribution of the fork grating can be calculated using the diffraction formula. Specifically, the fork grating can be regarded as a grating composed of two slits, and then the intensity distribution of diffracted light of different orders is calculated based on the width and distance of the slits and the wavelength of the incident light. The order distribution of the fork grating is periodic, that is, within a certain range of orders, the intensity of light of different orders will change periodically. Light beams of high diffraction orders will have an impact on practical applications, so it is necessary to suppress the high-order diffraction components of light to improve imaging quality.

Please refer to FIG. 3 , which is a schematic diagram of a simulation of the order distribution of a conventional fork-shaped grating structure in the visible light band.

As shown in Figure 3, if the existing fork grating structure is used, light of different wavelengths will be diffracted. The number of orders generated is different, and the reflectivity and refractive index of light of different wavelengths are also different, and the difference in reflectivity and refractive index will affect the diffraction image. Therefore, it is necessary to reduce the number of orders generated when light of different wavelengths is diffracted as much as possible.

Based on this, in this embodiment, the edge of the first grating structure 110 and the edge of the second grating structure 120 are sawtooth-shaped; in the edge of any grating structure, the distance between two adjacent sawtooths is the same, and each sawtooth is randomly normally distributed along the vector direction of the one-dimensional grating.

When the edge of the grating structure is designed to be sawtooth-shaped, the number of orders generated when light of different wavelengths is diffracted can be effectively reduced, that is, the high-order diffraction components of the light can be effectively suppressed.

Please refer to Figure 4, which is a schematic diagram of the simulated order distribution of the fork-shaped grating structure of the present application in the visible light band. As can be seen from Figure 4, when the edge of the grating structure is designed to be sawtooth-shaped, the number of orders generated by light of different wavelengths when diffracted is the same, avoiding the influence of the high-order diffraction components of the light during the diffraction process, thereby effectively ensuring the quality of the diffraction image and improving the imaging quality.

Continuing to refer to FIG. 3 , when the fork-shaped grating structure is a refractive type, the existing fork-shaped grating structure generates 11 orders when diffracting light of a wavelength of 450nm, 9 orders when diffracting light of 500nm, and 5 orders when diffracting light of 650nm.

Continuing to refer to FIG. 4 , when the fork-shaped grating structure is a refractive type, the number of orders generated by the fork-shaped grating structure of this embodiment when diffracting light in the wavelength range of 450 nm to 650 nm is always 3.

Similarly, when the fork-shaped grating structure is a reflective type, the number of orders generated by the existing fork-shaped grating structure when diffracting light of wavelengths 450nm and 500nm is 3, and the number of orders generated when diffracting light of 600nm is 1.

When the fork-shaped grating structure is a refractive type, the number of orders generated by the fork-shaped grating structure of this embodiment when diffracting light in the wavelength range of 450nm to 650nm is 1.

By comparing FIG3 and FIG4 , it can be seen that the fork-shaped grating structure of the present embodiment not only reduces the number of orders generated during diffraction, but also makes the order data generated by diffraction unaffected by the wavelength, thereby effectively ensuring the quality of the diffraction image and further improving the imaging quality.

Since the fork-shaped grating structure has a better diffraction effect on light of different wavelengths when it is a reflective type, it can be preferably set as a reflective grating.

It should be noted that the fork-shaped metasurface grating can be regarded as two one-dimensional gratings crossing at a preset angle, wherein the edge of the one-dimensional grating is also serrated. Encloses the vector directions of two different one-dimensional gratings.

As described above, the forked metasurface grating for suppressing high-order light provided in this embodiment includes at least one first grating structure and at least one second grating structure, the size of the first grating structure is larger than the size of the second grating structure, and the coupling efficiency can be adjusted by changing the size ratio of the two grating structures; the first grating structure and the second grating structure are forked structures, the crossing angle of the first grating structure and the crossing angle of the second grating structure are the same, and the cross-shaped structure can better reduce the leakage of light on the outside; the edge of the first grating structure and the edge of the second grating structure are serrated, and the distance between two adjacent serrations in the edge of any grating structure is the same, and each serration is randomly normally distributed along the vector direction of the one-dimensional grating. By setting the edge of the grating structure to be serrated, it is beneficial to suppress the high-order diffraction components of light, thereby improving the imaging quality.

In some embodiments, in the first grating structure, the distance between two saw teeth ranges from 5nm to 50nm, and the tooth height of the saw teeth ranges from 30nm to 700nm; in the second grating structure, the distance between two saw teeth ranges from 5nm to 100nm, and the tooth height of the saw teeth ranges from 30nm to 1000nm.

Please refer to FIG. 5 , which is a schematic diagram of the grating structure of the present application. The distance between two saw teeth is denoted as D1 , and the tooth height of the saw teeth is denoted as D2 .

The range of the distance D1 between the saw teeth will affect the suppression effect of the high-order diffraction components of the light. Generally speaking, within a certain range, the smaller the distance D1 between the saw teeth is, the better the suppression effect of the high-order diffraction components is: when the distance D1 between the saw teeth is small, the scattering angle of the light passing through the fork grating structure will be larger, making it difficult for the light of the high-order diffraction components to coherent, thereby reducing the impact caused by the high-order light coherence. However, if the distance is too small, it will not only increase the difficulty of grating manufacturing, but also may lead to an increase in the diffraction loss of light. Therefore, the distance between the saw teeth needs to balance between the grating manufacturing process and the system performance, and select an appropriate range of values.

Optionally, in the first grating structure, the distance D1 between two saw teeth can range from 5nm to 50nm, and the tooth height D2 of the saw teeth can range from 30nm to 700nm; in the second grating structure, the distance between two saw teeth can range from 5nm to 100nm, and the tooth height D2 of the saw teeth can range from 30nm to 1000nm.

In some embodiments, the edges of the saw teeth are rectangular, arc-shaped or triangular.

Preferably, the edges of the saw teeth may be rectangular.

Please refer to Figures 6(a)-6(c), which are three types of sawtooth edges in this application. 6(a) is a schematic diagram of a primitive with a rectangular sawtooth edge, FIG6(b) is a primitive with a triangular sawtooth edge, and FIG6(c) is a primitive with an arc sawtooth edge.

The edges of the sawtooth can take many different shapes, including rectangular, arc or triangle. Different edge shapes will have different effects on the diffraction and scattering of light, so the advantages and disadvantages of different edge shapes and their impact on system performance need to be considered when designing and manufacturing fork-shaped metasurface gratings.

For example, in some cases, the arc edge may reduce light scattering, thereby improving the imaging quality, while in other cases, the rectangular or triangular edge may more effectively suppress the high-order diffraction components, thereby improving the system performance. Those skilled in the art may choose to adjust the edge shape of the fork grating structure according to actual needs, and this embodiment does not limit this.

In some embodiments, the first distances between adjacent first grating structures and second grating structures are equal, the second distances between two adjacent first grating structures are equal, the third distances between two adjacent second grating structures are equal, and the second distance and the third distance are equal.

Please refer to FIG. 7 , which is a schematic diagram of the distance between grating structures in the fork-shaped metasurface grating for suppressing high-order light in the present application.

It should be noted that in order to illustrate the distance relationship between the grating structures, the interference of other factors is ignored in FIG. 7 , so the squares A1 , A2 , A3 can be regarded as the first grating structure, and the squares B1 , B2 , B3 can be regarded as the second grating structure.

Optionally, the center point of the first grating structure may be regarded as a square A1, and the center point of the second grating structure may be regarded as a square B2.

The first distance between any adjacent first grating structures and the second grating structures is equal, the second distance between any adjacent two first grating structures is equal, and the third distance between any adjacent two second grating structures is equal, wherein the second distance and the third distance are equal.

In some embodiments, as shown in FIG. 7 , the distance between A1 and B1 is d1 , the distance between A1 and B2 is d2 , the distance between A2 and B2 is d3 , and d1 = d2 = d3 .

The distance between A1 and A2 is d4, the distance between A1 and A3 is d5, and d4=d5.

The distance between B1 and B2 is d6, the distance between B1 and B3 is d7, d6=d7, and d4=d5=d6=d7.

In some embodiments, the first distance may be in the range of 50 nm to 500 nm; the second distance may be in the range of 100 nm to 1000 nm.

In some embodiments, two first primitives are crossed at a first angle to form a first grating structure, and two second primitives are crossed at the first angle to form a second grating structure.

Optionally, the value range of the first angle may be 10° to 80°.

The crossing angle of the fork grating structure can affect the light coupling efficiency and light leakage. Generally, within a certain range, the smaller the crossing angle, the higher the coupling efficiency and the relatively less light leakage, thereby improving privacy. However, too small a crossing angle may increase the high-order diffraction components of light, affecting the imaging quality. The length and width of the element will also affect the performance of the grating. Those skilled in the art can adjust the crossing angle of the fork grating structure, the length and width of the element according to actual needs.

In some embodiments, the first primitive includes a first rectangular structure stacked in sequence along a first direction and a first rectangular structure stacked in sequence along a second direction, wherein the angle between the first direction and the second direction is a first angle; in the same direction, any adjacent first rectangular structures are staggered to form a serrated edge of a first grating structure; the second primitive includes a second rectangular structure stacked in sequence along the first direction and a second rectangular structure stacked in sequence along the second direction; in the same direction, any adjacent second rectangular structures are staggered to form a serrated edge of a second grating structure.

Please refer to FIG8 , which is a schematic diagram of the structure of a primitive in the fork-shaped metasurface grating of advanced light of the present application.

Any primitive includes first rectangular structures stacked in sequence along a first direction and first rectangular structures stacked in sequence along a second direction, wherein an angle between the first direction and the second direction is a first angle, denoted as θ.

Specifically, the first primitive 810 may include first rectangular structures sequentially stacked along a first direction and first rectangular structures sequentially stacked along a second direction, wherein an angle between the first direction and the second direction is a first angle.

Furthermore, in the same direction, any adjacent first rectangular structures are arranged in a staggered manner to form a serrated edge of the first grating structure; the second element 820 includes second rectangular structures stacked in sequence along the first direction and second rectangular structures stacked in sequence along the second direction; in the same direction, any adjacent second rectangular structures are arranged in a staggered manner to form a serrated edge of the second grating structure.

The sizes of the first rectangular structure and the second rectangular structure may be different.

The fork-shaped metasurface grating for suppressing higher-order light can be made of materials with high transmittance in the visible light band, such as silicon oxide, silicon nitride, gallium nitride, titanium dioxide, etc., with a refractive index greater than 1.5.

The present application also provides a two-dimensional diffraction optical waveguide. Please refer to FIG. 9 , which is a schematic diagram of a top view of the structure of an embodiment of the two-dimensional diffraction optical waveguide of the present application.

In this embodiment, the two-dimensional diffraction optical waveguide includes a waveguide substrate 900, a one-dimensional coupling-in grating 910 disposed on the surface of the waveguide substrate, and the fork-shaped metasurface grating 920 for suppressing higher-order light.

Among them, the one-dimensional coupling grating 910 is used to couple the incident light carrying image information into the two-dimensional diffraction optical waveguide; the fork-shaped metasurface grating 920 that suppresses high-order light is used to diffract and expand the diffracted light from the one-dimensional coupling grating 910 and transmitted in a total reflection manner in the waveguide substrate 900 in two directions to couple it out to the human eye for imaging.

The one-dimensional coupling-in grating 910 can be any high-efficiency grating, and the waveguide substrate 900 is a light-transmitting substrate, such as glass. The glass material has a high refractive index, which is conducive to achieving total reflection of internal light, thereby facilitating the transfer of light entering from the one-dimensional coupling-in grating 910 to the fork-shaped metasurface grating 920 that suppresses high-order light.

Alternatively, the one-dimensional coupling-in grating 910 and the fork-shaped metasurface grating 920 for suppressing higher-order light can be regarded as photolithographically shaping a thin film of a high-refractive-index material deposited on the waveguide substrate 900.

In some embodiments, the one-dimensional coupling-in grating includes a first grating column and a second grating column arranged at an interval, and the length of the first grating column is greater than the length of the second grating column; the edge of the first grating column and the edge of the second grating column are serrated, and in any grating column, the distance between two adjacent serrations is the same, and each serration is randomly normally distributed along the vector direction of the one-dimensional grating.

Since the two-dimensional grating can be regarded as two one-dimensional gratings crossed, the distribution law of the sawtooth edge of the one-dimensional coupling-in grating in this embodiment can be the same as the distribution law of the two-dimensional diamond grating, which is as follows:

Please refer to FIGS. 10-11 , where FIG. 10 is a schematic diagram showing a cosine distribution of the lateral area of a one-dimensional coupling grating row of the present invention, and FIG. 11 is a schematic diagram showing an embodiment of a one-dimensional grating sawtooth edge of the present invention.

As shown in Figure 11, a one-dimensional grating including a sawtooth edge can be regarded as a plurality of identical rectangular structures stacked in a misaligned manner in the same direction. Assuming that the length of each rectangular structure is L1, the offset caused by the misalignment of each rectangular structure is L2 or L3, and then: L2≤0.5L1, L3≤0.5L1.

In Figure 10, the horizontal axis is the vector direction of the one-dimensional grating, and the vertical axis is the area integral of the one-dimensional grating. Each sawtooth is randomly normally distributed along the vector direction of the one-dimensional grating, and the integral area is cosine distributed.

Specifically, along the diffraction direction, the grating period is d, the length of the rectangular structure is d/2, and the rectangular structure is randomly arranged according to the cosine distribution law within the range of (-d/4 to d/4) of each grating period. The rate function satisfies x is the coordinate of the grating along the diffraction direction.

The present application also provides a near-eye display device, comprising a microdisplay and any of the two-dimensional diffraction optical waveguides described above, wherein the microdisplay outputs incident light carrying image information.

The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit it. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application.

Claims (10)

A fork-shaped metasurface grating for suppressing high-order light comprises at least one first grating structure and at least one second grating structure, wherein the size of the first grating structure is larger than the size of the second grating structure, The first grating structure and the second grating structure are fork-shaped structures, the crossing angle of the first grating structure and the crossing angle of the second grating structure are the same, and the edges of the first grating structure and the edges of the second grating structure are serrated; In the edge of any grating structure, the distance between two adjacent saw teeth is the same, and each saw tooth is randomly and normally distributed along the vector direction of the one-dimensional grating. The fork-shaped metasurface grating for suppressing higher-order light according to claim 1, wherein: In the first grating structure, the distance between the two saw teeth ranges from 5 nm to 50 nm, and the tooth height of the saw teeth ranges from 30 nm to 700 nm; In the second grating structure, the distance between the two saw teeth ranges from 5 nm to 100 nm, and the tooth height of the saw teeth ranges from 30 nm to 1000 nm. The fork-shaped metasurface grating for suppressing high-order light according to claim 1, wherein the edges of the sawtooth are rectangular, arc-shaped or triangular. The fork-shaped metasurface grating for suppressing high-order light according to claim 2, wherein the first distances between adjacent first grating structures and second grating structures are equal, the second distances between two adjacent first grating structures are equal, the third distances between two adjacent second grating structures are equal, and the second distance and the third distance are equal. The fork-shaped metasurface grating for suppressing higher-order light according to claim 4, wherein: The first distance has a value range of 50 nm to 500 nm; the second distance has a value range of 100 nm to 1000 nm. The fork-shaped metasurface grating for suppressing high-order light according to claim 5, wherein two first primitives cross at a first angle to form the first grating structure, and two second primitives cross at the first angle to form the second grating structure, The first angle has a value range of 10° to 80°. The fork-shaped metasurface grating for suppressing higher-order light according to claim 6, wherein: The first primitive includes first rectangular structures stacked in sequence along a first direction and first rectangular structures stacked in sequence along a second direction, wherein the first direction and the second direction are sandwiched between The angle is the first angle, and any adjacent first rectangular structures in the same direction are arranged in a staggered manner to form a serrated shape at the edge of the first grating structure; The second element includes second rectangular structures stacked in sequence along the first direction and second rectangular structures stacked in sequence along the second direction, wherein any adjacent second rectangular structures in the same direction are staggered to form a serrated edge of the second grating structure. A two-dimensional diffraction optical waveguide, comprising: a waveguide substrate, a one-dimensional coupling-in grating arranged on the surface of the waveguide substrate, and a fork-shaped metasurface grating for suppressing high-order light as claimed in any one of claims 1 to 7, The one-dimensional coupling grating is used to couple the incident light carrying image information into the two-dimensional diffraction optical waveguide; the fork-shaped metasurface grating for suppressing higher-order light is used to diffract and expand the diffracted light from the one-dimensional coupling grating and transmitted in the waveguide substrate by total reflection in two directions, so as to couple it out to the human eye for imaging. The two-dimensional diffraction optical waveguide according to claim 8, wherein: The one-dimensional coupling-in grating comprises a first grating column and a second grating column which are arranged at intervals, wherein the length of the first grating column is greater than the length of the second grating column; The edge of the first grating column and the edge of the second grating column are sawtooth-shaped. In any grating column, the distance between two adjacent sawtooths is the same, and each sawtooth is randomly and normally distributed along the vector direction of the one-dimensional grating. A near-eye display device comprises a microdisplay and a two-dimensional diffraction optical waveguide as claimed in any one of claims 8 to 9, wherein the microdisplay outputs incident light carrying image information.