Bi-Material Mode Multiplexer for Compact Low-Crosstalk Coupling
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Solution Overview
Problem
Existing mode multiplexers suffer from high modal crosstalk, leading to increased size and cost due to the need for extended lengths to mitigate this issue.
Innovation Solution
A mode multiplexer with layered optical waveguides formed using different materials, where the first optical waveguide tapers to prevent signal propagation and the second optical waveguide widens to support multiple modes, allowing for optical coupling with reduced crosstalk and compact design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the length of the mode multiplexer is increased to reduce modal crosstalk, then the modal crosstalk is reduced, but the size and cost of the mode multiplexer increase
Solution Approach 1:
The patent changes the refractive index parameter by using different materials (silicon nitride with lower refractive index and silicon with higher refractive index) for the two waveguides. This material parameter change enables effective mode coupling and crosstalk reduction in a compact 60 μm length, avoiding the need for long lengths (200-400 μm) required by conventional single-material waveguide-based mode multiplexers.
2Reliability
If the length of the mode multiplexer is increased to reduce modal crosstalk, then the modal crosstalk is reduced, but the cost of the mode multiplexer increases
Solution Approach 1:
The patent changes the material parameters (refractive indices) to achieve better coupling efficiency in a shorter device length, reducing manufacturing complexity and cost despite using different materials.
Solution Approach 2:
The patent employs composite materials with different refractive indices (silicon nitride and silicon) to create waveguides that enable effective mode coupling. This composite material approach allows for compact device design with reduced manufacturing costs compared to conventional long-length single-material waveguide-based mode multiplexers.
3Productivity
If the first optical waveguide maintains constant width, then signal propagation is maintained, but modal crosstalk increases
Solution Approach 1:
The patent applies local quality by making the width of the first optical waveguide position-dependent. The waveguide width varies along its length, being wider at the input end and narrower at the output end where it overlaps with the second waveguide. This local variation in geometric parameter enables controlled mode coupling and crosstalk reduction while maintaining signal propagation efficiency.
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 modal crosstalk and device length, achieving compactness (e.g., 60 μm) while maintaining low loss or crosstalk across a wide wavelength band.
Implementation Method 1
The second optical waveguide has a higher index of refraction than the first optical waveguide. The first optical waveguide and the second optical waveguide are arranged such that an optical signal propagating from a first end towards a second end in the first optical waveguide optically couples into the second optical waveguide.
Data Source
AI summary
The present disclosure describes a mode multiplexer with layered optical waveguides formed using different materials. The mode multiplexer includes a first optical waveguide and a second optical waveguide. The first optical waveguide includes a first end and a second end. The first end is wider than the second end. The second optical waveguide includes a third end. The second optical waveguide has a higher index of refraction than the first optical waveguide. The first optical waveguide and the second optical waveguide are arranged such that when the first optical waveguide and the second optical waveguide are viewed along a first axis: a length of the first optical waveguide and a length of the second optical waveguide extend along a second axis orthogonal to the first axis, the first end is non-overlapping with the third end, and the second optical waveguide partially overlaps the second end.