Tapered Spot Size Converter for Optical Coupling Loss
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Solution Overview
Problem
Semiconductor optical devices with shallow and deep ridge waveguides experience increased optical coupling loss due to mismatched far-field patterns with optical fibers and silica waveguides, limiting the efficiency of mode conversion and complicating manufacturing processes.
Innovation Solution
A spot size converter is designed with a tapered core layer and waveguide layer structure, where the waveguide layer is wider on one side and matches the core layer's width on the other side, allowing for efficient mode conversion within the core layer, simplifying the manufacturing process and maximizing productivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the width of a shallow ridge waveguide is decreased to improve mode conversion, then the effective refractive index variation is not large enough, but mode conversion efficiency remains low
Solution Approach 1:
The patent applies asymmetry by creating a ridge waveguide with different widths at opposite ends (first end wider than second end). This asymmetric structure enables gradual mode conversion along the waveguide length, improving coupling efficiency between ridge waveguide mode and optical fiber mode without requiring complex multi-layer or multi-component structures.
Solution Approach 2:
The patent changes the width parameter of the ridge waveguide along its length, creating a tapered profile where the width gradually transitions from the first end to the second end. This continuous parameter change enables smooth mode transformation, achieving high mode conversion efficiency while maintaining structural simplicity.
2Manufacturing precision
If the thickness of a clad layer is gradually decreased to decrease effective refractive index, then mode conversion improves, but manufacturing processes become complicated
Solution Approach 1:
The patent extracts the mode conversion function from complex multi-layer thickness variations and implements it through a single ridge waveguide width variation. By taking out the essential function (mode conversion) and implementing it through a simpler geometric parameter change rather than multiple layer thickness adjustments, the manufacturing process is simplified while maintaining effectiveness.
3Reliability
If a ridge waveguide is disposed near a different type of ridge waveguide for mode conversion, then coupling efficiency improves, but device structure becomes complex
Solution Approach 1:
The patent merges the mode conversion function into the ridge waveguide itself through its asymmetric width profile, eliminating the need for separate conversion waveguides or additional optical components. This merging approach achieves high coupling efficiency while reducing overall device complexity by integrating multiple functions into a single structural element.
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 tapered structure reduces optical coupling loss by minimizing the full-width at half maximum of the far-field pattern, enhancing coupling efficiency while maintaining high productivity through simplified manufacturing.
Implementation Method 1
a spot size converter which includes a core layer 30 that is tapered in a first direction on a side of a substrate 10; and a waveguide layer 50 that covers the core layer 30 on the first side of the substrate 10, and that is tapered in a second direction opposite to the first direction
Data Source
AI summary
Provided are a spot size converter and a method of manufacturing the spot size converter. The method includes stacking a lower clad layer, a core layer, and a first upper clad layer on a substrate, tapering the first upper clad layer and the core layer in a first direction on a side of the substrate, forming a waveguide layer on the first upper clad layer and the lower clad layer, and etching the waveguide layer, the first upper clad layer, the core layer, and the lower clad layer such that the waveguide layer is wider than a tapered portion of the core layer on the side of the substrate and has the same width as that of the core layer on another side of the substrate.