Asymmetric Diffraction Grating for Optical Waveguide Coupling-Out
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Solution Overview
Problem
The existing two-dimensional diffraction gratings in optical waveguides have limited shape adjustable parameters and low degree of freedom for design, which hinders the adjustment of coupling-out efficiency.
Innovation Solution
A diffraction grating with asymmetric micro-structure units, featuring edges that are not parallel to either dimension direction, and transformation angles ranging from 5° to 175°, allowing for increased design freedom and adjustable parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If regular-shaped micro-structure units (circles, ellipses, triangles, parallelograms) are used in two-dimensional diffraction gratings, then the grating structure is simple to manufacture, but the shape adjustable parameters are limited and coupling-out efficiency cannot be optimized
Solution Approach 1:
The patent applies asymmetry by designing micro-structure units with irregular polygonal shapes that have at least one edge not parallel to either the first or second dimension directions. This asymmetric design breaks the symmetry of traditional regular shapes (circles, ellipses, triangles, parallelograms) and provides multiple shape adjustable parameters including edge angles, vertex positions, and side lengths, enabling optimization of coupling-out efficiency while maintaining manufacturability through standard photolithography processes.
Solution Approach 2:
The patent employs parameter changes by systematically varying geometric parameters of the micro-structure units such as the number of edges, edge lengths, vertex angles, and relative orientations. These parameter adjustments allow fine-tuning of the diffraction grating's optical properties, particularly coupling-out efficiency, while the manufacturing process remains compatible with existing semiconductor fabrication techniques.
2Device complexity
If regular-shaped micro-structure units are used, then the design process is straightforward, but the degree of freedom for design is low and coupling-out efficiency adjustment is hindered
Solution Approach 1:
The patent introduces asymmetry in the micro-structure unit designs with irregular polygonal shapes having edges at various angles relative to the dimension directions. This increases the degree of freedom by adding controllable variables such as edge inclination angles, vertex positions, and relative edge lengths, while the design process remains systematic and can be implemented using standard computational design tools and photolithography manufacturing methods.
3Adaptability or versatility
If asymmetric micro-structure units with non-parallel edges are used, then coupling-out efficiency and design freedom are improved, but the manufacturing precision requirements increase
Solution Approach 1:
The patent utilizes parameter changes by defining specific angular ranges for the edges (5° to 175° relative to dimension directions) and optimizing geometric parameters such as edge lengths and vertex positions. These parameter specifications provide design flexibility for optimizing coupling-out efficiency while establishing clear manufacturing tolerances that are compatible with standard photolithography processes, thereby balancing design freedom with manufacturing precision requirements.
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 asymmetric design enhances coupling-out efficiency, diffraction selectivity, and image brightness by providing more adjustable parameters and richer design freedom for the micro-structure units.
Implementation Method 1
a plurality of micro-structure units formed on the substrate and periodically arranged at intervals in a first dimension direction and a second dimension direction
Data Source
Figure 1~2a
Figure 2b~2d
Figure 2e~2g
AI summary
A diffraction grating (10), an optical waveguide apparatus including the diffraction grating (10), and a display device. The diffraction grating (10) comprises: a substrate (1); and a plurality of micro-structure units (2), which are formed on the substrate (1) and are periodically arranged at intervals in a first dimension direction (p1) and a second dimension direction (p2). A pattern formed by the orthographic projections of the micro-structure units (2) on the substrate (1) comprises a first closed pattern (21), wherein the first closed pattern (21) is an asymmetric pattern, the boundary of the first closed pattern (21) is formed by sequentially connecting three or more edges in a surrounding manner, and among the three or more edges, there is at least one straight-line edge, which is neither parallel to the first dimension direction (p1) nor to the second dimension direction (p2). Therefore, each micro-structure unit (2) has more adjustable parameters and rich degree of freedom for design, which facilitates the adjustment of coupling-out efficiency.