Tapered Waveguide Spot Size Converter for Mode Filtering
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Solution Overview
Problem
Existing spot size converters excite higher-order modes when an optical beam is misaligned, leading to unexpected effects in optical processors due to the propagation of these modes through internal waveguides.
Innovation Solution
A semiconductor optical device with a spot size converter comprising a first semiconductor waveguide, a second semiconductor waveguide with a larger width for optical coupling, a third semiconductor waveguide with an even larger width, and a tapered waveguide that attenuates odd-order modes and converts the spot size of the optical beam, reducing higher-order mode propagation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional spot size converter is used, then the spot size of the optical beam can be converted, but higher-order modes are excited when the beam is misaligned, causing unexpected effects in optical processors
Solution Approach 1:
The waveguide structure is divided into multiple sections with different width characteristics: a first waveguide section with width for single-mode propagation, a second waveguide section with larger width for mode filtering, and a tapered waveguide section for gradual spot size conversion. This segmentation allows each section to perform its specific function of reducing higher-order modes while converting spot size.
Solution Approach 2:
Different sections of the waveguide are designed with different local properties: the second waveguide section has a larger width specifically optimized for attenuating odd-order modes, while the tapered section has a gradually changing width for smooth mode transformation. This local optimization ensures that higher-order modes are suppressed at the appropriate location without affecting the overall spot size conversion function.
2Object-generated harmful factors
If the waveguide width is increased to reduce higher-order modes, then mode filtering improves, but the device complexity increases
Solution Approach 1:
The spot size conversion function and the higher-order mode filtering function are merged into a single integrated waveguide structure. The tapered waveguide section simultaneously performs spot size transformation and mode filtering, eliminating the need for separate components and reducing overall device complexity while achieving both objectives.
Solution Approach 2:
The waveguide width is varied in the lateral dimension to create the tapered structure, allowing smooth transition between different mode fields. This dimensional approach enables gradual mode transformation without introducing additional complex structures or components.
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 effectively reduces odd-order modes, minimizing optical loss and preventing unexpected effects in optical processors by filtering and converting the optical beam, ensuring improved performance and reduced leakage modes.
Implementation Method 1
a single tapered waveguide having a first end portion connected to the third semiconductor waveguide structure, and a second end portion connected to the first semiconductor waveguide structure, the single tapered waveguide having a width gradually changing in a direction from the first end portion to the second end portion
Data Source
AI summary
A spot size converter includes: a first semiconductor waveguide structure having a first width enabling single mode propagation; a second semiconductor waveguide structure having a second width greater than the first width, a second semiconductor waveguide structure including an end face for optically coupling with an external waveguide; a third semiconductor waveguide structure having a third width greater than the first and second widths, the third semiconductor waveguide structure being optically coupled to the second semiconductor waveguide structure; and a single tapered waveguide having a first end portion connected to the third semiconductor waveguide structure, and a second end portion connected to the first semiconductor waveguide structure, the single tapered waveguide having a width gradually changing in a direction from the first end portion to the second end portion.