Tapered Diffraction Grating via Anisotropic Etching
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Solution Overview
Problem
Existing diffraction gratings face challenges in achieving high efficiency and controlled manufacturing, particularly in achieving optimal diffraction efficiency and minimizing stray light, especially in applications like space-based spectrographs and laser cavities, due to limitations in uniformity and precision of ruling methods and holographic techniques.
Innovation Solution
The development of a diffraction grating with tunable groove bottom width and blaze angle, achieved through anisotropic etching of a silicon wafer, which forms tapered structures with optimized cavity widths and corrugation amplitudes, enhancing diffraction efficiency by controlling electromagnetic field interactions within the grating structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If ruling methods are used to produce gratings, then design freedom and blaze angle optimization are improved, but line density uniformity deteriorates
Solution Approach 1:
The patent uses a master grating as a template that is replicated multiple times through replication techniques. The master grating is created with precise line density and optimized blaze angle through ruling, then this pattern is copied to produce additional gratings, thereby transferring the design freedom and precision achievements to multiple units without repeating the complex ruling process for each one.
2Manufacturing precision
If holographic methods are used to produce gratings, then line density uniformity is improved, but design freedom and blaze angle optimization are worsened
Solution Approach 1:
The replication process copies the master grating's precise line density pattern to multiple gratings, preserving the uniformity advantage of holographic methods while allowing the master to be designed with optimized blaze angles through ruling techniques.
Solution Approach 2:
The patent allows modification of grating parameters such as blaze angle, groove depth, and line density by changing the master grating design or replication conditions. This enables optimization for different applications while maintaining manufacturing precision through the replication process.
3Adaptability or versatility
If traditional ruling methods are used, then blaze angle optimization is improved, but manufacturing complexity and precision limitations are worsened
Solution Approach 1:
The master grating captures the optimized blaze angle design through ruling, and subsequent replication copies this geometry to multiple gratings. This separates the complex precision ruling operation (performed once on the master) from mass production, reducing the need for repeatedly operating complex ruling instruments.
Solution Approach 2:
The master grating is prepared in advance with all the precise geometric features and optimized blaze angles. This preliminary creation of the master template eliminates the need for complex precision ruling operations during subsequent grating production, simplifying the manufacturing process for additional gratings.
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 significantly improves diffraction efficiency, achieving efficiencies up to 90% or higher while minimizing stray light, leading to higher quality spectral images and reduced interference, suitable for various optical applications including spectrographs and laser cavities.
Implementation Method 1
anisotropic etching of a silicon wafer
Implementation Method 2
A diffraction grating operates on the principle that phases of light traveling through different light paths, reflected or transmitted by the grating lines, constructively interfere in certain directions while destructively interfering in other directions
Implementation Method 3
enhancing diffraction efficiency by controlling electromagnetic field interactions within the grating structure
Data Source
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AI summary
A manufacturing method for a grating is disclosed for the angular dispersion of light impinging the grating. The grating comprises tapered structures and cavities. A cavity width and/or corrugation amplitude is varied for achieving a desired grating efficiency according to calculation. A method is disclosed for conveniently creating gratings with variable cavity width and/or corrugation amplitude. The method comprises the step of anisotropically etching a groove pattern into a grating master. Optionally a replica is produced that is complementary to the grating master. By variation of an etching resist pattern, the cavity width of the grating may be varied allowing the optimization towards different efficiency goals.