Self-Aligned Stacked Gratings for Waveguide Light Out-Coupling
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Solution Overview
Problem
Conventional near-eye displays (NEDs) face challenges in achieving high out-coupling efficiency of image light due to low refractive index materials, leading to low throughput and difficulty in manufacturing compact, lightweight NEDs with a wide field-of-vision for augmented reality systems.
Innovation Solution
A manufacturing system that uses a patterning, deposition, and etching process to create optical gratings with variable refractive indices through self-aligned stacking of materials, including photoresists and protective coatings, to enhance light coupling into optical waveguides.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional materials with low refractive index are used in near-eye displays, then the device can be manufactured with simpler materials, but the light out-coupling efficiency is reduced
Solution Approach 1:
The patent employs composite materials consisting of multiple layers with different refractive indices (e.g., TiO2, SiO2, Nb2O5) stacked in a specific configuration. This composite structure enables high light out-coupling efficiency by creating optical gratings that effectively modulate light propagation, while still using conventional deposition techniques for manufacturing.
Solution Approach 2:
The invention applies local quality by creating spatially varying refractive index distributions within the waveguide structure. Different regions of the waveguide contain materials with specifically tailored refractive indices to optimize light coupling at different locations, achieving high out-coupling efficiency without requiring the entire device to use complex materials throughout.
2Loss of energy
If high refractive index materials are used to improve light coupling, then out-coupling efficiency increases, but the manufacturing complexity and process difficulty increase
Solution Approach 1:
The manufacturing process is segmented into discrete, sequential deposition steps where each layer is deposited independently with controlled thickness and refractive index. This segmentation allows for precise control of the optical grating structure while maintaining manufacturability through standardized deposition processes for each individual layer.
Solution Approach 2:
The invention utilizes parameter changes by systematically varying the refractive index, thickness, and sequence of material layers to optimize optical performance. By adjusting these parameters during the deposition process, the manufacturing system achieves high out-coupling efficiency through controlled material properties rather than complex structural designs.
3Device complexity
If conventional near-eye display designs are used, then the device structure can be kept simple, but the field-of-vision and compactness are limited
Solution Approach 1:
The patent transitions from conventional two-dimensional display structures to three-dimensional optical grating structures within the waveguide. By utilizing the vertical dimension for multi-layer material stacking and creating depth-resolved refractive index profiles, the system achieves expanded field-of-vision while maintaining a compact overall device form factor.
Solution Approach 2:
The invention implements a nested structure where multiple functional layers are embedded within the waveguide thickness. The optical grating layers, protective coatings, and functional materials are nested in a hierarchical arrangement that maximizes optical performance within the available vertical space, enabling compact design with enhanced field-of-vision.
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 solution enables the production of NEDs with improved light out-coupling efficiency, enabling compact, lightweight, and wide field-of-vision displays suitable for augmented reality applications with high manufacturing throughput.
Implementation Method 1
deposition of a first photoresist of a first refractive index on the protective coating... deposition of a second photoresist of a second refractive index on the first photoresist. The second refractive index is greater than the first refractive index
Implementation Method 2
The manufacturing system performs the selective removal of the volatile photoresist in the stack created over the substrate. The manufacturing system performs the selective removal of the volatile photoresist based on a thermal decomposition process
Data Source
AI summary
A manufacturing system for fabricating self-aligned grating elements with a variable refractive index includes a patterning system, a deposition system, and an etching system. The manufacturing system performs a lithographic patterning of one or more photoresists to create a stack over a substrate. The manufacturing system performs a conformal deposition of a protective coating on the stack. The manufacturing system performs a deposition of a first photoresist of a first refractive index on the protective coating. The manufacturing system performs a removal of the first photoresist to achieve a threshold value of first thickness. The manufacturing system performs a deposition of a second photoresist of a second refractive index on the first photoresist. The second refractive index is greater than the first refractive index. The manufacturing system performs a removal of the second photoresist to achieve a threshold value of second thickness to form a portion of an optical grating.