Auxiliary Structures in AR Waveguide Anti-Reflection Coatings
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Solution Overview
Problem
Waveguides for augmented, virtual, and mixed reality face challenges with high reflectivity and visibility issues due to the presence of waveguide regions with high refractive index materials, causing distracting reflections and reduced visibility of the real world.
Innovation Solution
Incorporating auxiliary structures with a pitch less than the grating pitch between the gratings in the waveguide, which are fabricated using methods such as etching or imprinting, to minimize diffraction and reflections, allowing for concurrent fabrication with the grating structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If waveguide regions with high refractive index materials are used between gratings, then light guidance and coupling efficiency are improved, but distracting reflections and reduced visibility of the real world occur
Solution Approach 1:
The patent applies local quality by creating auxiliary structures with different geometric properties (smaller pitch) than the main grating structures. These auxiliary structures are localized in the waveguide regions between gratings and have tailored dimensions to provide anti-reflection functionality specifically in those regions, while the main gratings maintain their original light-coupling function. This local differentiation resolves the contradiction by allowing high refractive index materials to be used for efficient light guidance while the locally-modified auxiliary structures suppress harmful reflections.
2Object-generated harmful factors
If auxiliary structures with smaller pitch are added between gratings, then reflections and diffraction are minimized, but device complexity and fabrication difficulty increase
Solution Approach 1:
The patent merges the fabrication of auxiliary structures with the existing grating fabrication process. Both the main gratings and auxiliary structures are formed in the same lithography and etching steps, using a single patterned layer. This consolidation approach reduces device complexity by eliminating separate fabrication steps while still achieving the dual functionality of light coupling (via main gratings) and reflection suppression (via auxiliary structures).
Solution Approach 2:
The patent segments the waveguide surface into two functional zones: main grating regions for light coupling and auxiliary structure regions for anti-reflection. The auxiliary structures are segmented with smaller pitch specifically in the waveguide regions between gratings, creating a spatially-resolved structure that addresses different optical requirements in different locations without requiring completely separate fabrication processes.
3Productivity
If auxiliary structures are fabricated concurrently with gratings, then manufacturing time is reduced, but manufacturing precision requirements increase
Solution Approach 1:
The patent employs a universal fabrication approach where a single lithography step defines both the main grating patterns and auxiliary structure patterns simultaneously. The same photoresist layer and etching process serve dual purposes: creating the primary light-coupling gratings and the secondary anti-reflection auxiliary structures. This multi-functional process reduces productivity loss while managing precision requirements through unified process control rather than sequential steps.
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 auxiliary structures reduce distracting reflections and maintain visibility by preventing diffraction of light in total internal reflection, enabling improved user experience by minimizing high reflection regions between gratings.
Implementation Method 1
preventing diffraction of light in total internal reflection
Implementation Method 2
minimize diffraction and reflections
Data Source
AI summary
A waveguide is disclosed. The waveguide includes one or more gratings disposed over a substrate. The gratings include grating structures having a grating pitch. The waveguide includes a waveguide region disposed over the substrate between each grating and an edge of the substrate. The waveguide region includes auxiliary structures with an auxiliary pitch less than the grating pitch.