Si Optical Waveguide Stepwise Tapered Light Input Output Part
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Solution Overview
Problem
Current methods for manufacturing Si optical waveguides face challenges in dimensional accuracy and complexity, particularly in spot-size converters, leading to variations in coupling efficiency and polarization dependence.
Innovation Solution
A method involving wet etching of single-crystalline Si using an alkaline solution, where the (111) plane acts as an etch-stop plane, simplifies the process and reduces dimensional variations by forming terraced or tapered patterns, resulting in a Si optical waveguide with improved reproducibility and reduced polarization dependence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional manufacturing methods are used for Si optical waveguides, then the process can be implemented with standard techniques, but dimensional accuracy and manufacturing precision deteriorate due to variations in coupling efficiency and polarization dependence
Solution Approach 1:
The patent changes the etching parameters by using wet etching with alkaline solution instead of conventional dry etching methods. This parameter change exploits the anisotropic etching characteristics of silicon crystal structures, where the etching rate differs significantly between crystal planes, enabling precise control of waveguide dimensions and reducing manufacturing variations
Solution Approach 2:
The patent replaces mechanical/dry etching processes with chemical wet etching methods. This substitution allows the chemical reaction to selectively remove material based on crystal plane orientation, achieving superior dimensional accuracy without the limitations of mechanical etching control
2Reliability
If spot-size converters are manufactured with conventional methods, then the basic structure can be formed, but coupling efficiency varies and polarization dependence increases
Solution Approach 1:
The patent applies local quality by creating specific crystal plane orientations at critical locations within the spot-size converter structure. The (111) planes are strategically positioned at the output face to provide uniform light coupling characteristics, while other regions maintain different orientations to achieve the desired size transformation, thereby improving coupling efficiency and reducing polarization dependence
3Productivity
If the (111) plane is used as etch-stop plane in wet etching, then manufacturing yield and dimensional accuracy improve, but the process requires precise control of etching conditions
Solution Approach 1:
The patent employs self-service by utilizing the inherent self-limiting nature of anisotropic wet etching. The etching process automatically stops when it encounters the (111) crystal planes, which etch extremely slowly, creating natural etch-stop planes without requiring external control mechanisms. This self-regulating property simplifies process control while achieving high manufacturing yield and dimensional accuracy
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 method enhances the manufacturing yield and dimensional accuracy of optical devices, allowing for efficient light coupling and reduced radiation loss, while maintaining polarization independence.
Implementation Method 1
A method involving wet etching of single-crystalline Si using an alkaline solution
Implementation Method 2
where the (111) plane acts as an etch-stop plane, simplifies the process and reduces dimensional variations by forming terraced or tapered patterns
Data Source
AI summary
An optical device includes an optical waveguide provided on a principal surface of a substrate. The optical waveguide includes a core and a cladding provided around the core. The cladding is configured by a substance having a refractive index smaller than 71.4% of the refractive index of the core. The core has constituent atoms substantially forming a diamond lattice structure. The optical waveguide has a light input/output part through which a light beam is input and/or output. The light input/output part decreases stepwise in thickness towards an output end while tapering down in its width. The core is provided in the light input/output part to have a (111) plane or an equivalent plane to the (111) plane exposed on a face of a riser of the stepwise thickness of the light input/output part.