Back-End-of-Line Truncated Layers for Photonics Edge Couplers
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Solution Overview
Problem
Conventional photonics chips experience significant power loss due to the large mode size mismatch between optical fibers and edge couplers, leading to inefficiencies in coupling laser light.
Innovation Solution
A structure and method for forming an edge coupler with a waveguide core and a back-end-of-line stack that includes a tapered section and truncated layers, where the truncated layers are overlapped with the tapered section, reducing the mode size mismatch and enhancing coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If direct butt-coupling between optical fiber and edge coupler is used, then coupling structure is simple, but power loss is significant due to mode size mismatch
Solution Approach 1:
The patent introduces an intermediary structure (the back-end-of-line stack with truncated layers) between the optical fiber and the edge coupler waveguide core. This intermediary gradually transforms the optical mode from the large-mode-area fiber to the smaller waveguide mode, acting as a mediator that enables efficient coupling without direct contact between the mismatched components.
Solution Approach 2:
The patent utilizes the vertical dimension by stacking multiple truncated layers at different heights above the waveguide core. This three-dimensional arrangement creates a gradual mode transformation path through the vertical space, allowing the optical field to adapt from the fiber mode to the waveguide mode through multiple intermediate stages rather than a single abrupt transition.
2Adaptability or versatility
If edge coupler with small mode size is used to match waveguide, then waveguide integration is improved, but coupling efficiency with optical fiber deteriorates due to mode size mismatch
Solution Approach 1:
The patent divides the coupling transformation into multiple segments by using several truncated layers of different sizes stacked vertically. Each layer represents a segment of the overall mode transformation process, gradually reducing the mode size from the optical fiber scale to the waveguide scale through a series of stepped transitions rather than a single abrupt change.
Solution Approach 2:
The patent exploits the vertical dimension to resolve the mode size mismatch conflict. By arranging truncated layers at different heights above the waveguide core, the design creates a three-dimensional mode transformation path that enables gradual adaptation from large fiber mode to small waveguide mode, maintaining both waveguide integration benefits and coupling 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 proposed solution significantly reduces power loss by optimizing the mode size matching between the optical fiber and the edge coupler, improving the efficiency of laser light coupling.
Implementation Method 1
The truncated layer is tapered from the first end surface to the second end surface
Implementation Method 2
reducing the mode size mismatch between the optical fiber and the edge coupler
Data Source
AI summary
Structures including an edge coupler and methods of forming a structure including an edge coupler. The structure includes a waveguide core over a dielectric layer and a back-end-of-line stack over the dielectric layer and the waveguide core. The back-end-of-line stack includes a side edge and a truncated layer that is overlapped with a tapered section of the waveguide core. The truncated layer has a first end surface adjacent to the side edge and a second end surface above the tapered section of the waveguide core. The truncated layer is tapered from the first end surface to the second end surface.