Slanted Grating Waveguide Mass Production via Two-Photon Printing
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Solution Overview
Problem
Current methods for producing slanted diffractive waveguides for augmented reality glasses face challenges in low-cost mass production, particularly due to limitations in manufacturing large-area gratings with complex shapes and high efficiency, as existing technologies struggle with high production costs, long cycles, and damage to molds during demolding.
Innovation Solution
A method combining two-photon polymerization micro-nano 3D printing, precision micro electroforming, and composite nanoimprint lithography to create polymer and metal master molds, followed by working soft molds, enabling the mass production of slanted surface-relief gratings with any shape and size, using a two-time imprinting technique and peeling demolding to reduce force and prevent damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If electron beam lithography and etching technique are used to manufacture masters, then manufacturing precision of small masters is improved, but manufacturing cost and production cycle increase significantly
Solution Approach 1:
The patent pre-manufactures master molds with precise slanted grating structures using electron beam lithography and etching, then uses these masters for repeated nanoimprint copying. The preliminary high-precision master creation enables subsequent mass production through low-cost imprinting, resolving the contradiction between initial precision requirements and overall production efficiency
Solution Approach 2:
The patent creates master molds with precise slanted grating patterns, then uses nanoimprint technology to copy these patterns onto waveguide substrates in mass production. The master mold serves as a template that can be repeatedly copied, transferring the high precision from the master to multiple products at low cost
2Ease of manufacture
If traditional nanoimprint technique is used for slanted gratings, then manufacturing simplicity is improved, but demolding becomes difficult or impossible for large slant angles and depths
Solution Approach 1:
The patent introduces a lateral demolding dimension by designing the mold structure with a lateral release feature. Instead of attempting vertical demolding which fails for large slant angles, the mold releases the imprinted grating laterally, enabling successful demolding of structures with large slant angles and depths that would otherwise be impossible to manufacture
3Productivity
If slanted grating structures with large slant angles and depths are manufactured, then light coupling efficiency is improved, but demolding becomes impossible with existing techniques
Solution Approach 1:
The patent enables manufacturing of large slant angle and depth gratings by implementing lateral demolding. The mold structure includes a lateral release feature that allows the imprinted grating to be released sideways rather than vertically, making it possible to manufacture high-efficiency slanted gratings that would otherwise be impossible to demold
4Ease of manufacture
If rectangular grating structure is used, then manufacturing simplicity is improved, but light waste increases significantly
Solution Approach 1:
The patent transitions from symmetric rectangular grating structures to asymmetric slanted grating structures with optimized tilt angles. This asymmetry directs diffracted light preferentially toward the user's eyes rather than distributing it uniformly in all directions, significantly reducing light waste while maintaining manufacturing feasibility through nanoimprint technology
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 allows for low-cost, high-efficiency mass production of large-area slanted surface-relief gratings without constraints on shape or size, improving yield and extending the life of molds, while ensuring high-quality and accurate manufacturing of consumer-grade AR glasses.
Implementation Method 1
manufacturing a polymer master by using two-photon polymerization micro-nano 3D printing
Implementation Method 2
manufacturing a slanted grating metal nickel master mold by using the polymer master manufactured in step (1) in combination with precision micro electroforming technology
Implementation Method 3
manufacturing of a slanted surface-relief grating by composite nanoimprint lithography
Implementation Method 4
during demolding, 'peeling' demolding is used, and a demolding direction (the rotation direction of an auxiliary roller) is the same as the direction of the slanted grating on the working soft mold
Implementation Method 5
During the two-time imprinting, the rotation direction of the roller is opposite to the slanting direction of the slanted grating on the working soft mold
Data Source
AI summary
A method and apparatus for mass production of AR diffractive waveguides. Low-cost mass production of large-area AR diffractive waveguides (slanted surface-relief gratings) of any shape. Uses two-photon polymerization micro-nano 3D printing to realize manufacturing of slanted grating large-area masters of any shape (thereby solving the problem about manufacturing of slanted grating masters of any shape on the one hand, realizing direct manufacturing of large-size wafer-level masters on the other hand, and also having the advantages of low manufacturing cost and high production efficiency). Composite nanoimprint lithography technology is employed (in combination with the peculiar imprint technique and the composite soft mold suitable for slanted gratings) to solve the problem that a large-slanting-angle large-slot-depth slanted grating cannot be demolded and thus cannot be manufactured, and realize the manufacturing of the slanted grating without constraints (geometric shape and size).