Optical waveguide device and preparation method therefor, and ar near-eye display device and application thereof

Abstract

An optical waveguide device (10) and a preparation method therefor, and an AR near-eye display device (1) and an application thereof. A metasurface structure layer (200) is stacked on an outer surface of a coupling-in end (110) of the optical waveguide device (10), and light emitted by a light source device (20) passes through the metasurface structure layer (200) and is directly or indirectly coupled into an optical waveguide (100) to propagate. The metasurface structure layer (200) is configured to perform phase modulation on a first beam emitted to the metasurface structure layer (200), such that a second beam emitted from the metasurface structure layer (200) has collimation and directionality, thereby improving light coupling efficiency, and improving light energy utilization efficiency and display brightness. The optical waveguide device (10) and the light source device (20) constitute the AR near-eye display device (1), which can be applied to naked-eye 3D light field display.

Description

Optical waveguide devices and their fabrication methods, AR near-eye display devices and their applications

[0001] This application claims priority to Chinese Patent Application No. 2024115809084, filed on November 7, 2024, entitled "Optical Waveguide Device and Preparation Method Thereof, AR Near-Eye Display Device and Its Application", the entire contents of which are incorporated herein by reference.

[0002] Technical Field

[0003] This invention relates to the field of display technology, and in particular to an optical waveguide device and its fabrication method, an AR near-eye display device and its application. Background Technology

[0004] AR is an abbreviation for Augmented Reality. In AR display devices, virtual images are superimposed on real images to achieve a display effect that combines virtual and reality. Diffractive waveguides have advantages such as being ultra-light and ultra-thin, having a large pupil range, high transparency, and low mass production cost, making them one of the mainstream solutions for realizing AR displays. However, existing diffractive waveguides use gratings to couple visible light into the waveguide, but due to the low diffraction efficiency of the gratings, the light energy utilization is poor. Currently, the grating coupling efficiency of mass-produced diffractive waveguides is typically no higher than 10%. Furthermore, considering the mass production feasibility in actual manufacturing processes, certain restrictions need to be placed on the structural morphology of the coupling grating, so the final coupling efficiency of the coupling grating may be even lower. Existing diffractive waveguides include a light source device, a collimation system, a diffraction grating, and a waveguide, with the light source device and collimation system constituting the optomechanical part. Using a grating to couple visible light into the waveguide results in poor light energy utilization due to the low diffraction efficiency of the grating. Summary of the Invention

[0005] The present invention provides an achromatic array structure and its fabrication method, an optical waveguide, and an AR near-eye display system to solve technical problems such as dispersion and chromatic aberration that occur in traditional AR waveguides.

[0006] The present invention provides an optical waveguide device and its fabrication method, an AR near-eye display device and its application, to solve the technical problems of low coupling efficiency and poor light energy utilization.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0008] In a first aspect, this application provides an optical waveguide device, comprising:

[0009] An optical waveguide has an input end and an output end spaced apart. Signal light is coupled into the optical waveguide through the input end and propagates to the output end, where it is coupled out of the optical waveguide.

[0010] A metasurface structure layer is stacked on the outer surface of the optical waveguide at the coupling end. The metasurface structure layer is configured to phase modulate a first light beam emitted to the metasurface structure layer so that a second light beam emitted from the metasurface structure layer has collimation and directionality.

[0011] The metasurface structure layer includes multiple spaced arrays of metasurface units with three different phase structures. Each metasurface unit with a phase structure can perform phase modulation on light of a certain color. The phase modulation of light of a corresponding color by the metasurface unit satisfies the following formulas (1) to (3):

[0012]

[0013] In formula (1), For phase delay, For collimation delay phase; For phases deflected to different angles;

[0014] In formula (2), f is the focal length, ni is the refractive index of the medium through which the light incident on the metasurface structure layer passes, λ represents the wavelength of different color signal light, and x / y / z represents the spatial coordinates of the metasurface structure.

[0015] In formula (3), This represents the angle between the Z-axis and the projection of the deflected beam onto the XZ plane; The angle between the Z-axis and the projection of the deflected beam onto the YZ plane is represented; no represents the refractive index of the optical waveguide.

[0016] In one embodiment, the optical waveguide device further includes a protective adhesive layer filled between the metasurface units; and / or, the optical waveguide further includes an encapsulation glass disposed on the side of the metasurface structure layer opposite to the optical waveguide.

[0017] In one embodiment, each of the metasurface units has a columnar geometry or a ring geometry.

[0018] In one embodiment, the metasurface structure layer directly couples the signal light into the optical waveguide for propagation.

[0019] In one embodiment, the optical waveguide is further provided with a geometric optical element at the coupling end, and the signal light is coupled into the optical waveguide for propagation after passing through the metasurface structure layer and the geometric optical element in sequence.

[0020] Secondly, this application provides a method for fabricating an optical waveguide device, comprising the following steps:

[0021] Select an optical waveguide with input and output terminals;

[0022] Select three-color signal light: Select signal light with red, green and blue light, and measure the wavelengths of red light, green light and blue light in the signal light;

[0023] The design of the metasurface structure layer is based on the coupled-wave method and the finite-difference time-domain method. The coupled-wave method is used for unit structure design, and the finite-difference time-domain method is used for overall structure design and verification.

[0024] A metasurface structure layer is formed on the outer surface of the coupling end of the optical waveguide. The metasurface structure layer is configured to phase modulate a first light beam emitted to the metasurface structure layer so that a second light beam emitted from the metasurface structure layer has collimation and directionality.

[0025] The metasurface structure layer comprises multiple spaced arrays of metasurface units with three different phase structures. Each metasurface unit corresponding to a phase structure can perform phase modulation on light of a certain color. The metasurface unit performs phase modulation on light of a corresponding color, satisfying the following formulas (1) to (3):

[0026] In formula (1), For phase delay, For collimation delay phase; For phases deflected to different angles;

[0027] In formula (2), f is the focal length, ni is the refractive index of the medium through which the light incident on the metasurface structure layer passes, λ represents the wavelength of different color signal light, and x / y / z represents the spatial coordinates of the metasurface structure.

[0028] In formula (3), This represents the angle between the Z-axis and the projection of the deflected beam onto the XZ plane; The angle between the Z-axis and the projection of the deflected beam onto the YZ plane is represented; no represents the refractive index of the optical waveguide.

[0029] In one embodiment, the process of designing the metasurface structure layer includes the following steps:

[0030] Based on the parameters of the three-color signal light, a metasurface structure layer matching the three-color signal light is constructed;

[0031] Extract the phase distribution information of the metasurface structure layer;

[0032] The phase distribution information is discretized based on the periodic size of the metasurface unit library to obtain the phase discretization result;

[0033] The metasurface unit array is arranged according to the phase discretization results to construct the metasurface structure layer.

[0034] In one embodiment, forming the metasurface structure layer includes the following steps:

[0035] A metasurface film and a hard mask layer are sequentially deposited on the outer surface of the coupling end;

[0036] Patterning and etching are performed sequentially on the hard mask layer to transfer the pattern on the hard mask layer onto the metasurface film layer;

[0037] Remove the hard mask layer to form the metasurface structure layer;

[0038] The metasurface structure layer includes multiple metasurface units that match the wavelengths of the RGB primary color light.

[0039] Thirdly, this application provides an AR near-eye display device, comprising:

[0040] A light source device that emits three-color signal light, the light source device comprising a red photon sub-pixel, a green photon sub-pixel, and a blue photon sub-pixel;

[0041] In the optical waveguide device described in any of the preceding embodiments or the optical waveguide device fabricated in any of the preceding method embodiments, the light source device is disposed at the coupling end, and the three types of metasurface units are respectively aligned with the red photonic pixel, the green photonic pixel and the blue photonic pixel;

[0042] A coupling element is disposed at the coupling end and is used to couple out the signal light from the optical waveguide.

[0043] Fourthly, the AR near-eye display device described in the previous embodiments is applied to naked-eye 3D light field display.

[0044] As can be seen from the above technical solutions, the embodiments of the present invention have at least the following advantages and positive effects:

[0045] This invention provides an optical waveguide device and its fabrication method, an AR near-eye display device and its application. A metasurface structure layer is stacked on the outer surface of the coupling end of the optical waveguide device. Light emitted from a light source device propagates directly or indirectly into the optical waveguide through the metasurface structure layer. The metasurface structure layer is configured to phase-modulate the first light beam emitted to it, thereby ensuring collimation and directionality of the second light beam exiting the metasurface structure layer. This collimation and directionality of the light entering the optical waveguide improves the coupling efficiency, thus increasing light energy utilization and display brightness. The optical waveguide device and light source device of this application constitute an AR near-eye display device, which can be applied to naked-eye 3D light field displays. The metasurface structure layer not only achieves collimation and directionality of the emitted light, improving luminous efficiency and brightness, but also facilitates the thinning of the display optical engine. Furthermore, the metasurface structure layer includes three types of metasurface units, each of which phase-modulates a different color of light, thus reducing optical crosstalk. Attached Figure Description

[0046] 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.

[0047] Figure 1 is a schematic diagram of the optical path and overall structure of an optical waveguide device according to an embodiment of this application;

[0048] Figure 2 is a partially enlarged schematic diagram of the coupling end in the optical waveguide device shown in Figure 1;

[0049] Figure 3 is a schematic diagram of the optical path and overall structure of an optical waveguide device coupled to signal light through a metasurface structure layer in an embodiment.

[0050] Figure 4 is a schematic diagram of the optical path and overall structure of an optical waveguide device according to an embodiment, in which signal light is coupled in through a reflector.

[0051] Figure 5 is a schematic diagram of the optical path and overall structure of an optical waveguide device according to an embodiment, in which signal light is coupled in through a prism.

[0052] Figure 6 is a flowchart of the fabrication method of the optical waveguide device shown in Figure 1;

[0053] Figure 7 shows the step-by-step flow of the metasurface structure layer design in the preparation process shown in Figure 6;

[0054] Figure 8 shows the steps involved in the formation of the metasurface structure in the preparation process shown in Figure 6.

[0055] Figure 9 is a schematic diagram of the optical path and structure of an AR near-eye display device according to an embodiment of this application;

[0056] Figure 10 is an enlarged schematic diagram of the coupling part in the AR near-eye display device shown in Figure 9.

[0057] The annotations in the attached figures are explained as follows:

[0058] 1. AR near-eye display device;

[0059] 10. Optical waveguide device; 100. Optical waveguide; 110. Coupler input terminal; 111. Mirror; 112. Prism; 120. Coupler output terminal; 200. Metasurface structure layer; 201. Red light metasurface unit; 202. Green light metasurface unit; 203. Blue light metasurface unit; 300. Protective adhesive layer; 400. Encapsulation glass;

[0060] 20. Light source device; 21. Red photon pixel; 22. Green photon pixel; 23. Blue photon pixel;

[0061] 30. Coupling element.

[0062] Detailed Implementation

[0063] Typical embodiments embodying the features and advantages of the present invention will be described in detail in the following description. It should be understood that the present invention can have various variations in different embodiments without departing from the scope of the present invention, and the descriptions and illustrations herein are for illustrative purposes only and not intended to limit the present invention.

[0064] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the stated features. In the description of this application, "a plurality of" means two or more, unless otherwise explicitly specified.

[0065] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "setup," and "connection" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0066] Traditional diffractive waveguides typically collimate the signal light before coupling into a parallel beam using a collimation system, and then deflect it into the waveguide by a diffractive coupler. However, due to the low diffraction efficiency of the diffraction grating, the coupling efficiency is low, resulting in poor light energy utilization. Referring to Figure 1, this application provides an optical waveguide device 10 that enables the beam to have collimation and directionality to improve light energy utilization, while also eliminating the need for a collimation system, thus meeting the requirement for a thinner and lighter display optical engine.

[0067] Specifically, Figure 1 illustrates that the optical waveguide device 10 includes an optical waveguide 100 and a metasurface structure layer 200. Along the signal light propagation direction, the optical waveguide 100 has a spaced-apart coupling end 110 and a coupling end 120. The signal light is coupled into the optical waveguide 100 via the coupling end 110 and propagates to the outside of the optical waveguide 100 via the coupling end 120. The metasurface structure layer 200 is stacked on the outer surface of the optical waveguide 100 at the coupling end 110. The metasurface structure layer 200 is configured to phase-modulate the first beam of light emitted to the metasurface structure layer 200, so that the second beam of light emitted from the metasurface structure layer 200 has extremely high collimation and directionality. It should be noted that the collimation of light means that the beam is modulated from divergent light into a parallel beam, and the directionality of light means that the beam is modulated to exit at a preset angle. It should be noted that the metasurface structure layer 200 is composed of metasurface unit structures with a scale smaller than the incident light wavelength arranged according to a certain arrangement rule. The metasurface structure layer 200 is typically a micro / nano structure (GaN, TiO, SiN, etc.) built on a substrate material (SiO2, Al2O3, etc.). The metasurface structure layer 200, with its micro / nano structure optical modulation characteristics, can achieve accurate modulation of the incident light phase, thereby enabling precise control of the incident light. It features strong design flexibility, small structural size, and precise light control.

[0068] Specifically, Figure 2 illustrates that the signal light is RGB tri-color light, and the metasurface structure layer 200 includes multiple metasurface units arranged in an array with three different phase structures, namely red metasurface unit 201, green metasurface unit 202, and blue metasurface unit 203. Red metasurface unit 201 performs phase modulation on the red signal light; green metasurface unit 202 performs phase modulation on the green signal light; and blue metasurface unit 203 performs phase modulation on the blue signal light. That is, the metasurface unit corresponding to one phase structure performs phase modulation on the signal light of one color, and the metasurface unit performs phase modulation on the light emitted by the corresponding sub-pixel, satisfying the following formulas (1) to (3):

[0069]

[0070] In formula (1), For phase delay, For collimation delay phase; For phases deflected to different angles;

[0071] In formula (2), f is the focal length, ni is the refractive index of the medium through which the light incident on different metasurface units passes, λ represents the wavelength of the corresponding incident light, and x / y / z represents the spatial coordinates of the metasurface structure.

[0072] In formula (3), This represents the angle between the Z-axis and the projection of the deflected beam onto the XZ plane; The angle between the Z-axis and the projection of the deflected beam onto the YZ plane is indicated; no represents the refractive index of the outgoing medium, which here refers to the refractive index of the optical waveguide 100.

[0073] Preferably, in one embodiment, continuing to refer to FIG1, the metasurface structure layer 200, as a micro / nano structure, is highly susceptible to damage if directly exposed to air. Therefore, to protect the metasurface structure layer 200, the optical waveguide device 10 further includes a protective adhesive layer 300, which fills the spaces between the metasurface units. Additionally, the optical waveguide device 10 includes encapsulation glass 400, which is stacked on the side of the metasurface structure layer 200 facing away from the optical waveguide 100, i.e., covering the light-incident surface of the metasurface structure layer 200. It should be understood that the presence or absence of the protective adhesive layer 300 or the encapsulation glass 400 is not limited unless the metasurface structure layer 200 requires protection.

[0074] Preferably, in one embodiment, the smallest unit structure of each metasurface unit has a regular structure such as a columnar or annular geometry, which facilitates the fabrication and processing of the metasurface structure layer 200 (facilitating array arrangement). It should be noted that columnar geometry includes, but is not limited to, cylinders, cuboids, and cubes, while annular geometry includes, but is not limited to, concentric cylinders. It should be understood that, without considering the ease of fabrication and processing of the metasurface structure layer 200, the shape of the metasurface unit is not limited in this application.

[0075] Referring to Figure 3, in one embodiment, the metasurface structure layer 200 can not only modulate the phase of the incident signal light, giving it collimation and directionality, but also deflect the incident signal light into the optical waveguide 100 for propagation. That is, the metasurface structure layer 200 can directly couple the signal light into the optical waveguide 100 for propagation. In this case, the metasurface structure layer 200 serves as the coupling structure of the optical waveguide device 10, simultaneously possessing the functions of modulating and coupling the signal light, eliminating the need for an additional coupling structure and simplifying the structure of the optical waveguide device 10.

[0076] Referring to Figure 4, in one embodiment, the optical waveguide 100 has a reflector 111 inside the coupling end 110. The signal light is modulated by the metasurface structure layer 200 and emitted to the reflector 111. Then the signal light is reflected from the reflector 111 and coupled into the optical waveguide 100 for propagation.

[0077] Referring to Figure 5, in one embodiment, the optical waveguide 100 is provided with a prism 112 at the coupling end, and the metasurface structure layer 200 is attached to the mirror surface of the prism 112. The signal light is emitted to the prism 112 after being phase-modulated by the metasurface structure layer 200, and then the signal light is refracted by the prism 112 and coupled into the optical waveguide 100 for propagation.

[0078] It should be noted that both the reflector 111 and the prism 112 are non-diffractive geometric optical elements. The signal light is phase-modulated by the metasurface structure layer 200 and then coupled into the optical waveguide 100 by the geometric optical elements for propagation. Here, by adjusting the incident angle or shape of the signal light, the signal light can meet the total internal reflection condition within the optical waveguide 100. The signal light is totally internally reflected within the optical waveguide 100 to the coupling end 120, thereby improving the light energy utilization rate. Part of the signal light is coupled out of the optical waveguide 100 and enters the human eye, while the remaining light continues to propagate within the optical waveguide 100.

[0079] It should be understood that in this application, there is no limitation on whether the coupling end 210 is additionally provided with a coupling structure (such as a geometric optical element). The signal light can be directly coupled into the optical waveguide 100 through the metasurface structure layer 200 for propagation; or the signal light can be additionally coupled into the optical waveguide 100 through the phase modulation of the metasurface structure layer 200 and then coupled into the optical waveguide 100 for propagation. Here, the specific structure of the coupling structure is not limited.

[0080] Secondly, referring to Figure 6, the present invention provides a method for fabricating an optical waveguide device 10, comprising the following steps:

[0081] S10, Select an optical waveguide 100 with an input terminal 110 and an output terminal 120;

[0082] S20, Select three-color signal light: Select signal light with red light, green light and blue light, and measure the wavelength of red light, green light and blue light in the signal light;

[0083] S30, design the metasurface structure layer 200. The design of the metasurface structure layer 200 is based on the rigorous coupled-wave method (RCWA) and the finite-difference time-domain method (FDTD). RCWA is used for unit structure design, while FDTD is used for overall structure design and verification. The main parameters involved in the design process are: the height of the metasurface structure layer 200, and the morphology of the smallest unit structure of a single metasurface unit, which can be a regular structure such as a column or a ring, or a free-form structure.

[0084] S40, fabricate optical waveguide device 10, form metasurface structure layer 200 on the outer surface of coupling end 110 of optical waveguide 100, metasurface structure layer 200 is configured to phase modulate the first beam emitted to metasurface structure layer 200 so that the second beam emitted from metasurface structure layer 200 has collimation and directionality.

[0085] The metasurface structure layer 200 includes three different metasurface units, each of which performs phase modulation on light of a certain color; each metasurface unit performs phase modulation on light of a certain color signal, satisfying the following formulas (1) to (3):

[0086]

[0087] In formula (1), For phase delay, For collimation delay phase; For phases deflected to different angles;

[0088] In formula (2), f is the focal length, ni is the refractive index of the medium through which the light incident on different metasurface units passes, λ represents the wavelength of the corresponding incident light, and x / y / z represents the spatial coordinates of the metasurface structure.

[0089] In formula (3), This represents the angle between the Z-axis and the projection of the deflected beam onto the XZ plane; The angle between the Z-axis and the projection of the deflected beam onto the YZ plane is indicated; no represents the refractive index of the outgoing medium, which here refers to the refractive index of the optical waveguide 100.

[0090] Referring to Figure 7, the specific steps for designing the metasurface structure layer during the fabrication of the aforementioned optical waveguide device 10 are as follows:

[0091] S31, Collimation and deflection phase design: Based on the parameters of the light-emitting pixel, construct a metasurface structure layer that matches the light-emitting pixel, and extract the phase distribution information of the metasurface structure;

[0092] S32, Phase discretization: The phase distribution information is discretized based on the periodic size of the metasurface unit library to obtain the phase discretization result;

[0093] S33, construct a metasurface unit structure library. The metasurface unit structure library corresponds to the emission spectrum range of the luminescent pixel and includes multiple metasurface unit structures. Each metasurface unit structure corresponds to a phase value in the range of 0 to 2π. The phase values ​​corresponding to each metasurface unit structure are different.

[0094] S34. Construct a metasurface structure layer by arranging the metasurface unit array according to the phase discretization result.

[0095] In one embodiment, the phase distribution information is discretized based on the periodic dimensions of the metasurface unit structure library, including: dividing the phase distribution information using the period of the metasurface unit structure as the smallest division scale, so that the phase distribution information is discretized into phase values ​​in the range of 0 to 2π.

[0096] Referring to Figure 8, the specific steps for forming the metasurface structure layer 200 during the fabrication of the aforementioned optical waveguide device 10 are as follows:

[0097] S41, deposit two thin films: a metasurface material thin film (such as SiNx, nanoimprint stencil, etc.) and a hard mask thin film (such as aluminum Al, titanium Ti, chromium Cr, etc.) are sequentially deposited on the outer surface of the coupling end 110 of the optical waveguide 100;

[0098] S42, Image processing, patterning the hard mask film to form a pattern of metasurface structure and thus form a hard mask layer;

[0099] S43, Etching: Using the hard mask layer as a mask, the metasurface material film is etched to transfer the pattern of the hard mask layer onto the metasurface material film.

[0100] S44, clean, and then remove the hard mask layer to form a metasurface structure layer;

[0101] The metasurface structure layer 200 includes multiple metasurface unit structures that match the wavelengths of the RGB primary color light.

[0102] Thirdly, referring to Figures 9 and 10, the present invention provides an AR near-eye display device 1, including a light source device 20, an optical waveguide device 10, and a coupling element 30. The light source device 20 is disposed at the coupling end 110 and is capable of emitting three-color signal light. Specifically, referring to Figure 9, the light source device 20 includes multiple red sub-pixels 21, multiple green sub-pixels 22, and multiple blue sub-pixels 23. The red sub-pixels 21 in the light source device 20 are paired with red metasurface units 201, the green sub-pixels 22 are paired with green metasurface units 202, and the blue sub-pixels 23 are paired with blue metasurface units 203. That is, the three metasurface units are respectively paired with the three colors of sub-pixels, so that one metasurface unit performs phase modulation on the light of one color. The coupling element 30 is disposed at the coupling end 120 and is used to couple out the signal light within the optical waveguide 100. Here, the light source device 20 includes, but is not limited to, LCOS, LED, OLED, quantum dot, etc.; the structure of the coupling element 30 includes, but is not limited to, optical elements with coupling function such as gratings, metasurfaces, holographic or liquid crystal material structures, microprisms, etc.

[0103] Here, the one-to-one alignment of metasurface units and sub-pixels can be achieved using high-precision alignment and bonding technology, aligning and bonding the metasurface structure layer with the light-emitting pixels. Alignment marks are simultaneously created during the fabrication of the light-emitting units, and these marks are referenced during subsequent fabrication of the metasurface structure to achieve pixel alignment.

[0104] Fourthly, 3D display is a technology capable of displaying scenes and objects with a sense of depth, allowing observers to directly observe 3D images with physical depth. Currently, 3D display technologies mainly include glasses-free and device-assisted displays, with glasses-free 3D display technology attracting significant attention due to its advantages of not requiring glasses or other auxiliary devices and its convenience and flexibility. Glasses-free 3D display technology is a light field display technology. It projects coded light field information onto different locations in space using light field modulation devices, forming a true 3D light field with continuous parallax at different locations in space, simultaneously providing stereoscopic parallax in multiple directions, including horizontal and vertical. However, because the depth of focus of the diffracted light waveguide is located at infinity, it is limited to displaying two-dimensional images at a fixed distance from the user. These limitations cause convergence-accommodation conflicts in the user's eyes, leading to reduced realism and visual discomfort.

[0105] Figure 9 illustrates that the AR near-eye display device 1 provided by this invention can be applied to naked-eye 3D light field display. The light source device 20 emits three-color signal light, and the metasurface structure layer 200 is used to collimate and directionally emit the emitted light from each pixel. The emission direction not only satisfies the viewing angle rules of the diffraction waveguide but also the light field modulation rules of the light field display, in order to reproduce a naked-eye visible 3D light field. The modulated light forms multiple independent viewpoints at the user's eyeball. When more than two viewpoints enter the eye simultaneously, the eye is guided to focus, thereby generating depth perception. The optical waveguide 100 is used to propagate the signal light. The coupling element 30 is used to couple the signal light within the optical waveguide 100 to the outside of the optical waveguide 100. The coupling element 30 includes, but is not limited to, optical elements with coupling functions such as gratings, metasurfaces, holographic or liquid crystal material structures, and microprisms.

[0106] This invention discloses an optical waveguide device 10 and its fabrication method, an AR near-eye display device 1, and their applications. A metasurface structure layer 200 is stacked on the outer surface of the coupling end 110 of the optical waveguide device 10. Signal light emitted from the light source device 20 propagates directly or indirectly into the optical waveguide 100 via the metasurface structure layer 200. The metasurface structure layer 200 is configured to phase-modulate the first light beam emitted to it, thereby ensuring collimation and directionality of the second light beam exiting the metasurface structure layer. This collimation and directionality of the light entering the optical waveguide 100 improves the coupling efficiency, thereby increasing light energy utilization and display brightness. The optical waveguide device 10 and the light source device 20 constitute the AR near-eye display device 1, which can be applied to naked-eye 3D light field displays. The metasurface structure layer 200 not only achieves collimation and directionality of the emitted light, improving light efficiency and brightness, but also facilitates the thinning of the display optical engine. On the other hand, the metasurface structure layer 200 includes three metasurface units, each of which performs phase modulation on a color of light, which can also reduce optical crosstalk.

[0107] Although the invention has been described with reference to several typical embodiments, it should be understood that the terminology used is illustrative and exemplary, and not restrictive. Since the invention can be embodied in many forms without departing from the spirit or essence of the invention, it should be understood that the above embodiments are not limited to any of the foregoing details, but should be interpreted broadly within the spirit and scope defined by the appended claims. Therefore, all variations and modifications falling within the scope of the claims or their equivalents should be covered by the appended claims.

Claims

1. An optical waveguide device, characterized in that, include: An optical waveguide has an input end and an output end spaced apart. Signal light is coupled into the optical waveguide through the input end and propagates to the output end, where it is coupled out of the optical waveguide. A metasurface structure layer is stacked on the outer surface of the optical waveguide at the coupling end. The metasurface structure layer is configured to phase modulate a first light beam emitted to the metasurface structure layer so that a second light beam emitted from the metasurface structure layer has collimation and directionality. The metasurface structure layer includes multiple spaced arrays of metasurface units with three different phase structures. Each metasurface unit with a phase structure can perform phase modulation on light of a certain color. The phase modulation of light of a corresponding color by the metasurface unit satisfies the following formulas (1) to (3): In formula (1), For phase delay, For collimation delay phase; For phases deflected to different angles; In formula (2), f is the focal length, and n i λ represents the refractive index of the medium through which the light incident on the metasurface structure layer passes, λ represents the wavelength of different color signal light, and x / y / z represents the spatial coordinates of the metasurface structure. In formula (3), This represents the angle between the Z-axis and the projection of the deflected beam onto the XZ plane; This represents the angle between the Z-axis and the projection of the deflected beam onto the YZ plane; n o This represents the refractive index of the optical waveguide.

2. The optical waveguide device according to claim 1, characterized in that, The optical waveguide device further includes a protective adhesive layer filled between the metasurface units; and / or, the optical waveguide further includes encapsulation glass disposed on the side of the metasurface structure layer opposite to the optical waveguide.

3. The optical waveguide device according to claim 1, characterized in that, Each of the metasurface units has a columnar or annular geometry.

4. The optical waveguide device according to claim 1, characterized in that, The metasurface structure layer directly couples the signal light into the optical waveguide for propagation.

5. The optical waveguide device according to claim 1, characterized in that, The optical waveguide is further provided with a geometric optical element at the coupling end. The signal light passes through the metasurface structure layer and the geometric optical element in sequence before being coupled into the optical waveguide for propagation.

6. A method for fabricating an optical waveguide device, characterized in that, Includes the following steps: Select an optical waveguide with input and output terminals; Select three-color signal light: Select signal light with red, green and blue light, and measure the wavelengths of red light, green light and blue light in the signal light; The design of the metasurface structure layer is based on the coupled-wave method and the finite-difference time-domain method. The coupled-wave method is used for unit structure design, and the finite-difference time-domain method is used for overall structure design and verification. A metasurface structure layer is formed on the outer surface of the coupling end of the optical waveguide. The metasurface structure layer is configured to phase modulate a first light beam emitted to the metasurface structure layer so that a second light beam emitted from the metasurface structure layer has collimation and directionality. The metasurface structure layer comprises multiple spaced arrays of metasurface units with three different phase structures. Each metasurface unit corresponding to a phase structure can perform phase modulation on light of a certain color. The metasurface unit performs phase modulation on light of a corresponding color, satisfying the following formulas (1) to (3): In formula (1), For phase delay, For collimation delay phase; For phases deflected to different angles; In formula (2), f is the focal length, ni is the refractive index of the medium through which the light incident on the metasurface structure layer passes, λ represents the wavelength of different color signal light, and x / y / z represents the spatial coordinates of the metasurface structure. In formula (3), This represents the angle between the Z-axis and the projection of the deflected beam onto the XZ plane; The angle between the Z-axis and the projection of the deflected beam onto the YZ plane is represented; no represents the refractive index of the optical waveguide.

7. The method for fabricating the optical waveguide device according to claim 6, characterized in that, The design process for metasurface structural layers includes the following steps: Based on the parameters of the three-color signal light, a metasurface structure layer matching the three-color signal light is constructed; Extract the phase distribution information of the metasurface structure layer; The phase distribution information is discretized based on the periodic size of the metasurface unit library to obtain the phase discretization result; The metasurface unit array is arranged according to the phase discretization results to construct the metasurface structure layer.

8. The method for fabricating the optical waveguide device according to claim 6, characterized in that, The formation of the metasurface structure layer includes the following steps: A metasurface film and a hard mask layer are sequentially deposited on the outer surface of the coupling end; Patterning and etching are performed sequentially on the hard mask layer to transfer the pattern on the hard mask layer onto the metasurface film layer; Remove the hard mask layer to form the metasurface structure layer; The metasurface structure layer includes multiple metasurface units that match the wavelengths of the RGB primary color light.

9. An AR near-eye display device, characterized in that, include: A light source device that emits three-color signal light, the light source device comprising a red photon sub-pixel, a green photon sub-pixel, and a blue photon sub-pixel; The optical waveguide device as described in any one of claims 1-5 or the optical waveguide device prepared by any one of claims 6-8, wherein the light source device is disposed at the coupling end, and the three metasurface units are respectively aligned with the red photonic pixel, the green photonic pixel and the blue photonic pixel; A coupling element is disposed at the coupling end and is used to couple out the signal light in the optical waveguide.

10. An application of an AR near-eye display device, characterized in that, The AR near-eye display device of claim 9 is applied to naked-eye 3D light field display.

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