Plasma Etching High-Index Glass for Diffractive Grating Patterning
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Solution Overview
Problem
Eching optical elements such as diffractive gratings in high refractive index glass substrates is challenging due to low silicon oxide content, leading to insufficient resolution and optical artifacts from deposited materials.
Innovation Solution
A plasma etching process is used to form features directly in high refractive index glass substrates, allowing high resolution and selectivity, with a patterned mask layer and chemical and physical etchant species, forming optical elements like diffractive gratings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional etching methods are used on high refractive index glass substrates, then the substrates can be processed, but the etching resolution is insufficient and optical artifacts are generated
Solution Approach 1:
The patent changes the chemical parameters of the etching process by using a plasma etch with specific chemical and physical etchant species. This alters the etching mechanism to achieve higher resolution and eliminate optical artifacts associated with conventional wet chemical etching methods.
Solution Approach 2:
The patent replaces conventional wet chemical etching with plasma etching, substituting a chemical-liquid system with a plasma-physics-based system. This substitution enables precise control over the etching process, achieving superior resolution and eliminating interface-related artifacts.
2Ease of manufacture
If deposited materials are used to form optical elements, then the elements can be created, but interface-related optical artifacts are generated
Solution Approach 1:
The patent extracts the problematic interface layer by etching directly into the glass substrate without depositing intermediate materials. This eliminates the interfaces that cause optical artifacts while maintaining the ability to form precise optical elements like diffractive gratings.
Solution Approach 2:
The patent uses a patterned mask layer as an intermediary to define the optical elements directly in the substrate. This mask-based approach replaces the need for deposited material layers, eliminating interface artifacts while preserving manufacturing capability.
3Reliability
If the glass substrate has high refractive index, then optical performance is improved, but the etching process becomes more difficult due to low silicon oxide content
Solution Approach 1:
The patent changes the etching parameters by using plasma-based chemistry that is effective for high refractive index glasses with low silicon oxide content. The plasma etch uses fluorinated gases and other chemistries that can selectively remove glass material regardless of silicon oxide concentration, enabling processing of high-performance optical substrates.
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 process enables precise formation of optical elements with desired dimensions and aspect ratios, improving optical performance by eliminating interface-related artifacts and simplifying manufacturing.
Implementation Method 1
etching the features in the substrate by exposing the mask layer and high refractive index glass substrate to a plasma etch comprising chemical and physical etchant species to selectively remove exposed high refractive index glass from the high refractive index glass substrate
Implementation Method 2
a plasma etch comprising chemical and physical etchant species to selectively remove exposed high refractive index glass
Implementation Method 3
a plasma etch comprising chemical and physical etchant species to selectively remove exposed high refractive index glass
Data Source
AI summary
Plasma etching processes for forming patterns in high refractive index glass substrates, such as for use as waveguides, are provided herein. The substrates may be formed of glass having a refractive index of greater than or equal to about 1.65 and having less than about 50 wt % SiO2. The plasma etching processes may include both chemical and physical etching components. In some embodiments, the plasma etching processes can include forming a patterned mask layer on at least a portion of the high refractive index glass substrate and exposing the mask layer and high refractive index glass substrate to a plasma to remove high refractive index glass from the exposed portions of the substrate. Any remaining mask layer is subsequently removed from the high refractive index glass substrate. The removal of the glass forms a desired patterned structure, such as a diffractive grating, in the high refractive index glass substrate.