Diffraction Grating Fabrication for High-Angle Waveguide Combiners
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Solution Overview
Problem
Current waveguide manufacturing technologies face challenges in high-volume production reproducibility, particularly in forming high-angle gratings and overcoming material shrinkage during imprint lithography, which limits the scalability and yield of waveguide combiners.
Innovation Solution
A combination of nanoimprint lithography (NIL) and direct etching methods is employed to fabricate waveguide combiners, allowing for the formation of high-angle gratings on transparent substrates, including glass, and overcoming material shrinkage by filling low-duty cycle gratings with high-index materials to achieve a wide range of duty cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional imprint replication is used to form gratings, then only materials that are imprint-able can be used, but this limits the scalability and yield of waveguide combiners
Solution Approach 1:
The patent changes the fundamental manufacturing parameter from imprint-based to direct-etch-based fabrication. This enables the use of glass and other non-imprintable materials while maintaining high-volume production capability through standardized semiconductor manufacturing processes
Solution Approach 2:
The patent replaces the mechanical imprint replication process with a direct etching process using photolithography and plasma etching. This substitution eliminates the material compatibility constraints of imprinting while enabling scalable production through established semiconductor fabrication techniques
2Manufacturing precision
If high-angle gratings are formed using traditional methods, then manufacturing precision is compromised, but this limits the optical performance of waveguide combiners
Solution Approach 1:
The patent applies preliminary patterning using photolithography to define the grating structure before etching. This preliminary action creates a precise mask that guides the subsequent high-angle plasma etching process, ensuring manufacturing precision is maintained even for challenging high-angle gratings
Solution Approach 2:
The patent replaces traditional mechanical grating formation methods with plasma-based direct etching. This substitution enables precise control of etch angles and depths through plasma parameter optimization, achieving high manufacturing precision for high-angle gratings that are difficult to produce mechanically
3Manufacturing precision
If material shrinkage occurs during imprint lithography, then the grating dimensions are inaccurate, but this reduces the reproducibility of mass production
Solution Approach 1:
The patent replaces imprint lithography with photolithography followed by plasma etching. This substitution eliminates material shrinkage issues inherent in imprinting, as the photolithographic patterning and subsequent etching processes maintain dimensional accuracy and reproducibility across high-volume production
Solution Approach 2:
The patent uses the photolithographic process to self-defined the accurate grating dimensions through photomask patterns. The process inherently maintains dimensional fidelity without requiring additional compensation for material shrinkage, as the pattern is transferred directly through photoresist and etching
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
This approach enables the mass production of waveguide combiners with improved reproducibility and scalability, facilitating the production of tens of millions of units by addressing the challenges of high-angle grating formation and material shrinkage.
Implementation Method 1
a method of directly etching a grating structure in a transparent substrate, the method including: forming a target stack on a substrate; forming a hardmask layer over the target stack; forming a pattern layer on the hardmask layer using nanoimprint lithography; etching the pattern layer, the hardmask layer, and the target stack using an ion beam to form a diffraction grating
Implementation Method 2
forming a pattern layer on the hardmask layer using nanoimprint lithography
Data Source
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Figure 2A~2F
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AI summary
The systems and methods discussed herein are for the fabrication of diffraction gratings, such as those gratings used in waveguide combiners. The waveguide combiners discussed herein are fabricated using nanoimprint lithography (NIL) of high-index and low-index materials in combination with and directional etching high-index and low-index materials. The waveguide combiners can be additionally or alternatively formed by the directional etching of transparent substrates. The waveguide combiners that include diffraction gratings discussed herein can be formed directly on permanent transparent substrates. In other examples, the diffraction gratings can be formed on temporary substrates and transferred to a permanent, transparent substrate.