Edge Couplers with Varying Grating Widths for Photonic Chips
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Solution Overview
Problem
Current edge couplers in photonics chips face challenges in efficiently transferring optical signals between optical fibers and waveguide cores due to limitations in layout area, cost, and operational overhead, necessitating improved structural designs for effective signal coupling.
Innovation Solution
A structure comprising a layer stack with a first and second dielectric layer, a waveguide core, and a coupler with varying grating structures and a transition structure, where the grating structures' widths change relative to the transition structure, facilitating efficient optical coupling without the need for semiconductor-based transition structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If traditional edge coupler structures are used, then optical coupling can be achieved, but layout area is increased and manufacturing cost is elevated
Solution Approach 1:
The coupler is divided into multiple grating structures with varying widths arranged in a sequence, where each grating structure has a different width to progressively transform the optical mode. This segmentation allows compact design while maintaining coupling efficiency, reducing both layout area and manufacturing complexity
Solution Approach 2:
The grating structures employ varying parameters including width, period, and depth along the propagation direction. These parameter changes enable gradual mode transformation from fiber to waveguide core, achieving efficient coupling in a compact footprint while simplifying the overall manufacturing process
2Ease of operation
If conventional coupling methods are used, then optical signals can be transferred, but operational overhead is increased
Solution Approach 1:
The grating structures are designed to automatically perform mode transformation through their inherent periodic geometry and varying dimensions. The structure self-adjusts the optical field distribution along the propagation direction without requiring external control or adjustment mechanisms, reducing operational overhead while maintaining high coupling efficiency and reliability
3Ease of manufacture
If simple grating structures are used, then manufacturing is simplified, but optical coupling efficiency is reduced
Solution Approach 1:
Different regions of the coupler feature grating structures with locally optimized qualities - varying widths, periods, and depths tailored to specific positions. This local quality variation enables efficient mode transformation throughout the coupling region while maintaining manufacturability through standard fabrication processes
Solution Approach 2:
The grating structures utilize three-dimensional geometry with variations in width, period, and depth along the propagation direction. This multi-dimensional design enables sophisticated optical control while remaining compatible with standard planar fabrication techniques, balancing manufacturing simplicity with high 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 structure enhances optical coupling efficiency and reduces operational overhead by allowing bidirectional in-plane coupling between waveguide cores and optical fibers, with lower loss and improved integration capabilities, thereby addressing the limitations of existing edge couplers.
Implementation Method 1
a coupler having a first plurality of grating structures and a transition structure including a second plurality of grating structures
Implementation Method 2
Optical signals from the much larger core of the optical fiber are transferred by the edge coupler to the considerably smaller waveguide core on the photonics chip
Data Source
AI summary
Structures for an edge coupler and methods of fabricating a structure for an edge coupler. A waveguide core and a coupler are formed over a layer stack that includes a first dielectric layer and a second dielectric layer over the first dielectric layer. The coupler includes a first plurality of grating structures and a transition structure including a second plurality of grating structures that are positioned between the first plurality of grating structures and the waveguide core. The first plurality of grating structures include respective widths that vary as a function of position relative to the transition structure.