Blazed Grating Fabrication via Nanoimprint Lithography
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Solution Overview
Problem
Current methods for fabricating blazed optical device structures are time-consuming and costly due to the need for multiple lithographic patterning operations and angled etch steps, which also result in low optical efficiency, stray light, ghost images, and a small Field of View (FOV).
Innovation Solution
The method involves disposing a first device material layer over a substrate, patterning it to form a plurality of gratings, and then using a nanoimprint lithography process to form a second plurality of gratings with a grating depth extending from the top surface of the first material layer. This process eliminates the need for multiple lithographic patterning and angled etch steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple lithographic patterning operations and angled etch steps are used to fabricate blazed optical device structures, then the optical device can achieve the desired grating structure, but the fabrication time and cost increase
Solution Approach 1:
The patent segments the grating formation process into two distinct stages: first forming a binary grating structure through conventional lithography, then converting it to a blazed grating structure through a separate etching process. This segmentation allows each stage to be optimized independently, achieving the desired precision while managing fabrication time through process specialization.
Solution Approach 2:
The patent employs preliminary action by first creating a binary grating pattern that serves as a template or mask for the subsequent blazed structure formation. This preliminary binary pattern guides the etching process to create the final blazed grating, eliminating the need for complex multi-step lithographic patterning and angled etch sequences.
2Manufacturing precision
If multiple lithographic patterning operations and angled etch steps are used to fabricate blazed optical device structures, then the grating structure can be formed, but the fabrication cost increases
Solution Approach 1:
The patent divides the manufacturing process into a first stage (binary grating formation) and a second stage (blazed structure conversion), allowing each stage to use optimized, potentially less expensive processes. This segmentation reduces the overall complexity and cost compared to conventional single-step approaches requiring multiple lithographic and etching operations.
Solution Approach 2:
The patent replaces complex mechanical lithographic patterning operations with a simpler two-step process involving initial pattern transfer followed by chemical or physical etching. This substitution reduces the number of expensive lithographic steps while maintaining the required grating precision.
3Productivity
If conventional grating designs and materials are used in waveguide display, then the optical device can function, but optical efficiency is low and stray light and ghost images occur
Solution Approach 1:
The patent employs asymmetry by creating blazed grating structures with asymmetric profile (non-uniform depth or height across the grating period) rather than symmetric binary gratings. This asymmetric geometry optimizes light coupling and propagation, improving optical efficiency while reducing stray light and ghost images through enhanced light directionality.
Solution Approach 2:
The patent changes the geometric parameters of the grating structure by transitioning from binary (two-level) to blazed (multi-level or continuous profile) geometries. This parameter change in the grating profile optimizes optical performance, improving efficiency and reducing harmful optical artifacts.
4Productivity
If current grating designs are used, then the optical device can be manufactured, but the Field of View is limited
Solution Approach 1:
The patent changes the grating design parameters by implementing blazed profiles with optimized duty cycles, depths, and periods that expand the Field of View. These parameter optimizations allow the grating to manage light more effectively, increasing FOV without proportionally increasing design complexity.
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 reduces fabrication time and costs while improving optical efficiency, image quality, and Field of View, enabling the production of optical devices with higher throughput and better performance.
Implementation Method 1
patterning the second device material layer with a nanoimprint lithography process to form a second plurality of device structures in the second material layer disposed on the first device material layer
Data Source
AI summary
Embodiments of the present disclosure include apparatus and methods for optical devices. In one embodiment, a method for forming an optical device generally includes disposing a first material device layer on a substrate, patterning a portion of the first material device layer to form a first plurality of device structures in the first material device layer, disposing a second material device layer on an un-patterned portion of the first device material layer, and patterning the second material device layer to form a second plurality of device structures disposed on the first material device layer.