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CN-121978800-A - Composite super-surface optical waveguide structure and preparation method thereof

CN121978800ACN 121978800 ACN121978800 ACN 121978800ACN-121978800-A

Abstract

The application provides a composite super-surface optical waveguide structure and a preparation method thereof, and belongs to the technical field of AR display. The composite super-surface optical waveguide structure comprises an optical waveguide substrate, a composite super-surface assembly, a composite cylindrical super-surface structure and a composite cylindrical super-surface structure, wherein the composite super-surface assembly is integrally arranged on the optical waveguide substrate and comprises a coupling-in assembly and a coupling-out assembly, the coupling-in assembly and the coupling-out assembly respectively comprise a composite grating super-surface structure and a composite cylindrical super-surface structure which are arranged in a stacked mode, the composite grating super-surface structure is an inclined grating structure, the refractive index of a lower grating layer is smaller than that of an upper grating layer, and the composite cylindrical super-surface structure comprises a lower cylindrical super-surface structure and an upper cylindrical super-surface structure which are arranged in a stacked mode along the direction far away from the optical waveguide substrate. The application can ensure high integration level, realize light weight, realize dispersion regulation of full visible spectrum, reduce diffraction angle deviation of blue light, green light and red light, obviously improve diffraction efficiency of RGB three-color light, reduce energy loss in light transmission process and improve imaging quality.

Inventors

  • LIU SHENG
  • ZHOU SHENGJUN
  • GU YUHUI

Assignees

  • 武汉大学

Dates

Publication Date
20260505
Application Date
20260203

Claims (10)

  1. 1. A composite supersurface optical waveguide structure comprising: an optical waveguide substrate having a coupling-in region and a coupling-out region arranged at an interval; the composite super-surface component is integrally arranged on the optical waveguide substrate and comprises a coupling-in component positioned in the coupling-in area and a coupling-out component positioned in the coupling-out area, wherein the coupling-in component and the coupling-out component both comprise a composite grating super-surface structure and a composite cylindrical super-surface structure which are stacked along the direction far away from the optical waveguide substrate; The composite grating super-surface structure is an inclined grating structure and comprises a lower grating layer and an upper grating layer which are stacked along the direction far away from the optical waveguide substrate, wherein the refractive index of the lower grating layer is smaller than that of the upper grating layer; The composite cylindrical super-surface structure comprises a lower cylindrical super-surface structure and an upper cylindrical super-surface structure which are arranged in a lamination manner along the direction far away from the optical waveguide substrate, and is used for compensating the diffraction angles of blue light and green light so as to reduce the diffraction angle deviation of the blue light, the green light and the red light and enable all RGB (red, green and blue) three-color light to meet the total reflection condition.
  2. 2. The composite supersurface optical waveguide structure of claim 1 wherein said composite grating supersurface structure in said coupling-in assembly is tilted in a direction from said coupling-out region toward said coupling-in region and said composite grating supersurface structure in said coupling-out assembly is tilted in a direction from said coupling-in region toward said coupling-out region.
  3. 3. The composite supersurface optical waveguide structure of claim 2 wherein the grating tilt angles of the composite grating supersurface structures in the coupling-in and coupling-out assemblies are each 15 ° to 25 °.
  4. 4. The composite super surface optical waveguide structure as claimed in claim 3, wherein the difference between the refractive index of the upper grating layer and the refractive index of the lower grating layer is 0.45 to 0.6.
  5. 5. The composite supersurface optical waveguide structure of claim 4 wherein the composite grating supersurface structure has a grating period of 460nm to 500nm and/or, The composite grating super surface structure has a grating duty cycle of 0.6 to 0.8, and/or, The thickness of the upper grating layer is 200nm to 280nm, and the thickness of the lower grating layer is 520nm to 580nm.
  6. 6. The composite supersurface optical waveguide structure of any one of claims 1 to 4 wherein said upper layer cylindrical supersurface structure and said lower layer cylindrical supersurface structure each comprise a transparent substrate and a plurality of cylindrical microstructures disposed in an array on said transparent substrate.
  7. 7. The composite supersurface optical waveguide structure of claim 6 wherein the period of the cylindrical microstructures in the upper layer cylindrical supersurface structure is the same as the period of the cylindrical microstructures in the lower layer cylindrical supersurface structure, and the diameter of the cylindrical microstructures in the upper layer cylindrical supersurface structure is different from the diameter of the cylindrical microstructures in the lower layer cylindrical supersurface structure.
  8. 8. The composite supersurface optical waveguide structure of claim 7 wherein the diameter of the cylindrical microstructures in the upper layer cylindrical supersurface structure is 80nm to 120nm and the diameter of the cylindrical microstructures in the lower layer cylindrical supersurface structure is 60nm to 130nm, and/or, The height of the cylindrical microstructure in the upper layer cylindrical super surface structure is 380nm to 420nm, and the height of the cylindrical microstructure in the lower layer cylindrical super surface structure is 280nm to 320nm.
  9. 9. The preparation method of the composite super-surface optical waveguide structure is characterized by comprising the following steps of: providing an optical waveguide substrate, wherein the optical waveguide substrate is provided with a coupling-in area and a coupling-out area which are arranged at intervals; The optical waveguide substrate is characterized in that a composite super-surface component is formed on the optical waveguide substrate, the composite super-surface component comprises a coupling-in component located in the coupling-in area and a coupling-out component located in the coupling-out area, the coupling-in component and the coupling-out component both comprise a composite grating super-surface structure and a composite cylindrical super-surface structure, the composite grating super-surface structure and the composite cylindrical super-surface structure are arranged in a stacked mode along the direction away from the optical waveguide substrate, the composite grating super-surface structure is an inclined grating structure and comprises a lower grating layer and an upper grating layer which are arranged in a stacked mode along the direction away from the optical waveguide substrate, the refractive index of the lower grating layer is smaller than that of the upper grating layer, the composite cylindrical super-surface structure comprises a lower cylindrical super-surface structure and an upper cylindrical super-surface structure which are arranged in a stacked mode along the direction away from the optical waveguide substrate, and is used for compensating diffraction angles of blue light and green light so as to reduce diffraction angle deviations of the blue light, the green light and red light, and enable RGB three light to meet the total reflection condition.
  10. 10. An AR display device comprising an image source, a collimating assembly disposed between the image source and the composite super-surface optical waveguide structure, and the composite super-surface optical waveguide structure of any one of claims 1-8, the collimating assembly configured to direct divergent light rays from the image source into parallel light beams and coupled into a coupling-in region of the composite super-surface optical waveguide structure.

Description

Composite super-surface optical waveguide structure and preparation method thereof Technical Field The application relates to the technical field of augmented reality (Augmented Reality, AR) display, in particular to a composite super-surface optical waveguide structure and a preparation method thereof. Background The AR near-to-eye display technology can superimpose the image generated by the computer with the real environment seen by the user in real time, so that fusion visual presentation is realized. The technology has shown wide application potential in the fields of education, medical treatment, consumption entertainment and the like. In AR near-eye display systems, the optical coupler is a key component determining display performance and device morphology, and its main function is to achieve efficient transmission and precise projection of optical signals. Among them, the optical waveguide structure has become the current mainstream optical coupler solution because of the advantages of light weight, strong portability, large field of view, low power consumption, excellent anti-glare performance, etc. However, the conventional AR optical waveguide technology still has a plurality of technical bottlenecks in practical application, which limit the performance improvement and the morphological optimization of the AR near-to-eye display device. First, it is difficult to achieve high diffraction efficiency in the full visible spectrum. AR displays use red (about 640 nm), green (about 530 nm) and blue (about 460 nm) light, that is, RGB three-color light to realize full-color imaging, and conventional optical waveguides mostly use a single-layer grating super-surface as a coupling structure. Due to material dispersion and structural singleness limitation, the single-layer grating super-surface can only obtain higher diffraction efficiency in a narrow band, and the whole visible spectrum is difficult to cover, so that the AR imaging brightness is insufficient and the color is unbalanced, and the display effect and the user visual experience are seriously affected. Secondly, the imaging quality is reduced due to serious chromatic aberration problems. Because the wavelength difference of RGB three colors is larger, the diffraction angles of the traditional single-layer grating super surface to different wavelengths have obvious deviation, so that the propagation paths of optical signals in the waveguide are inconsistent, and obvious phenomena such as color edges, ghost images and the like are generated at an imaging end. To alleviate this problem, a scheme of separating three colors of light by using a multi-layer optical waveguide is generally adopted in the related art, that is, independent waveguides (a single-layer grating super surface is disposed on each independent optical waveguide substrate as one optical waveguide) are designed for RGB light, and laminated and integrated. However, this solution may result in an increase in the volume and thickness of the device, against the development requirements of light weight and miniaturization of the AR display device, and at the same time, the splicing error between multiple waveguides may further reduce the imaging accuracy. Thirdly, the total reflection (Total Internal Reflection, TIR) condition of blue light is difficult to meet, and the light energy loss is serious. The optical waveguide implementation for long distance transmission relies on the condition of total reflection, i.e. the angle of incidence of the incident light at the waveguide interface must be greater than the critical angle. Because of the short wavelength of blue light, the deflection angle of the conventional single-layer grating super-surface to blue light is generally small, and is far lower than the total reflection critical angle of the optical waveguide (with the refractive index of 1.8 to 2.0). Therefore, a large amount of blue light cannot realize total reflection to generate transmission loss, so that not only is the blue light diffraction efficiency further reduced, but also the proportion of RGB light energy is unbalanced, and imaging color distortion is aggravated. In order to solve the technical bottleneck, the related technology can improve performance by optimizing grating parameters, improving material characteristics and the like, but the schemes are limited to single structure optimization, and the collaborative breakthrough of the bottleneck problem can not be fundamentally realized. Therefore, the development of an optical waveguide structure capable of simultaneously solving the above-described core problems has been a key to the development of high-end and practical AR near-to-eye display technologies. Disclosure of Invention The application provides a composite super-surface optical waveguide structure and a preparation method thereof, which can ensure high integration level, realize light weight, realize dispersion regulation and control of full visible spectrum