Diffractive Optical Waveguide Grating With Unequal Directional Spacing
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Solution Overview
Problem
Existing diffractive optical waveguides face limitations in diffraction efficiency and uniformity due to the use of rectangular gratings with limited parameter degrees of freedom, which are difficult to process finely and adjust efficiently.
Innovation Solution
A diffractive optical waveguide design featuring a grating structure with periodic structures arranged at different intervals along two directions, allowing for a one-dimensional grating equivalent with a vertical grating vector, facilitating easier processing and greater parameter adjustability, enhancing light efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If rectangular gratings are used in the waveguide, then the structure is simple and easy to manufacture, but the diffraction efficiency and uniformity are limited due to restricted parameter degrees of freedom
Solution Approach 1:
The patent transforms the rectangular grating structure into a triangular grating structure, fundamentally changing the geometric parameters. This parameter change provides additional degrees of freedom (including groove depth, groove width, and triangular angle) compared to rectangular gratings, enabling optimized diffraction efficiency and uniformity while maintaining manufacturability through standard semiconductor fabrication processes
2Device complexity
If rectangular gratings are used, then the design is straightforward, but the processing precision is limited and cannot be processed very fine by typical processes
Solution Approach 1:
By changing from rectangular to triangular grating geometry, the patent achieves finer processing capability. The triangular structure with its angled sides allows for more precise control over diffraction characteristics and can be manufactured with higher precision using conventional photolithography and etching processes, overcoming the processing limitations of rectangular gratings
3Device complexity
If rectangular gratings are used, then the structure is simple with only two parameter degrees of freedom, but the capability of adjusting the efficiency is limited
Solution Approach 1:
The triangular grating structure introduces additional adjustable parameters beyond depth and width, including the triangular angle and groove profile shape. These additional parameters provide enhanced capability for adjusting diffraction efficiency and optimizing performance for different wavelengths and incident angles, while the overall structure remains relatively simple and manufacturable
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The new design improves light efficiency and processing ease while maintaining high diffraction efficiency and uniformity, reducing energy waste and enhancing the performance of optical pupil expansion.
Implementation Method 1
couple input light into the waveguide substrate to cause it to propagate within the waveguide substrate through total reflection
Implementation Method 2
coupling-out grating...configured to couple light propagating in the waveguide substrate out of the waveguide substrate by diffraction
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~3D
AI summary
A diffractive optical waveguide for optical pupil expansion and a display device are provided. The diffractive optical waveguide comprises a waveguide substrate and a grating structure. The grating structure is disposed on a surface of the waveguide substrate or in the waveguide substrate and comprises a plurality of periodic structures arranged at intervals along a first direction and arranged at intervals along a second direction. The second direction is different from the first direction. A first distance between the centers of adjacent periodic structures in the first direction is smaller than a second distance between the centers of adjacent periodic structures in the second direction. The grating structure is equivalent to a one-dimensional grating with a grating vector in a vertical direction of the first direction, and the vertical direction is parallel to a plane where the grating structure is located.