Optical Waveguide Sinking Prevention Layer
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Solution Overview
Problem
Conventional optical waveguides using Ge-doped quartz glass for visible light experience increased loss due to color center generation, and the use of boron or fluorine-doped quartz glass for cladding materials results in a lower melting point, causing the core layer to sink into the cladding layer during thermal treatment, leading to uneven waveguide shape and reduced yield.
Innovation Solution
An optical waveguide structure with a sinking prevention layer composed of a material with a higher melting point than the lower cladding layer, which covers the core and lower cladding layers, preventing sinking and maintaining a uniform waveguide shape through surface tension, and a method of manufacturing involving deposition of layers to control thickness and refractive index.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Ge-doped quartz glass is used for core material, then optical communication wavelength performance is improved, but visible light loss increases due to color center generation
Solution Approach 1:
The patent removes GeO2 dopant from the core material to eliminate the source of color center generation. The core is made of pure SiO2, extracting the harmful dopant while maintaining the waveguide structure and function.
Solution Approach 2:
The patent changes the compositional parameter of the core material from Ge-doped SiO2 to pure SiO2, fundamentally altering the material properties to prevent visible light absorption while maintaining optical waveguide functionality.
2Shape
If boron or fluorine-doped quartz glass is used for cladding material, then refractive index difference is improved, but melting point decreases causing core layer sinking
Solution Approach 1:
The patent introduces a borosilicate glass layer as an intermediary between the pure SiO2 core and the fluorine-doped cladding. This intermediate layer has intermediate melting properties, preventing direct thermal interaction that would cause core sinking while maintaining the necessary refractive index difference.
Solution Approach 2:
The patent uses a composite structure combining pure SiO2 core, borosilicate glass intermediate layer, and fluorine-doped SiO2 cladding. This composite approach allows each layer to contribute its optimal properties: pure core for low loss, borosilicate for thermal stability, and fluorine-doped cladding for refractive index control.
3Ease of manufacture
If thermal treatment is applied for film formation, then upper cladding layer formation is improved, but core layer sinks into lower cladding layer
Solution Approach 1:
The patent applies a borosilicate glass intermediate layer beforehand to cushion and protect the core layer from thermal effects during subsequent processing. This preventive measure ensures core layer stability throughout the manufacturing process.
Solution Approach 2:
The borosilicate glass layer acts as a thermal intermediary, absorbing and distributing thermal stress during film formation processes, thereby preventing direct thermal damage to the core layer position.
4Shape
If etching is used to control core film thickness, then surface tension effect is improved, but etching rate distribution causes thickness non-uniformity
Solution Approach 1:
The patent removes the etching step entirely from the manufacturing process. Instead of using etching to control thickness, the core layer thickness is directly controlled during deposition, eliminating the source of thickness non-uniformity.
Solution Approach 2:
The patent replaces the mechanical/chemical etching process with a deposition-based thickness control method. This substitution eliminates the microloading effect and etching rate distribution issues inherent in etching processes.
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 solution reduces waveguide loss and maintains a consistent waveguide shape by preventing core layer sinking, improving yield and optical characteristics by using a sinking prevention layer with a higher melting point than the lower cladding layer.
Implementation Method 1
a method of using a surface tension acting on a core film by leaving the core film thin on a bottom surface of a rectangular core has been proposed
Implementation Method 2
the sinking prevention layer is composed of a material having a higher melting point than that of a material composing the lower cladding layer
Data Source
AI summary
To manufacture an optical waveguide including a substrate, a lower cladding layer formed on the substrate, a core layer formed on the lower cladding layer, a sinking prevention layer formed to cover the core layer and the lower cladding layer, and an upper cladding layer formed on the sinking prevention layer, in which the sinking prevention layer is composed of a material having a higher melting point than that of a material composing the lower cladding layer.