Dual-Layer Rib Waveguide Crossing for Silicon Photonics
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Solution Overview
Problem
Silicon photonic switch fabrics face significant challenges with high waveguide scattering loss and crosstalk due to numerous waveguide crossings, which hinder the development of low-loss and low-crosstalk broadband interconnects in large-scale photonic circuits.
Innovation Solution
A dual-layer waveguide crossing design featuring a lower optical layer with partially etched rib waveguides and an upper optical layer that traverses these rib waveguides, utilizing a substrate and buried oxide layer, reduces optical loss and crosstalk through a partially etched rib-and-slab structure and tapered transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If waveguide crossings are increased to enable large-scale photonic circuits, then interconnectivity is improved, but optical loss and crosstalk accumulate
Solution Approach 1:
The patent transitions from planar waveguide crossings to a three-dimensional stacked configuration where waveguides in different layers cross over each other vertically. This dimensional change allows crossings to occur without the waveguides occupying the same lateral space, thereby reducing crosstalk and optical loss while enabling larger-scale photonic circuits with more interconnections.
Solution Approach 2:
The photonic circuit is segmented into multiple stacked layers, each containing waveguides that can cross waveguides in adjacent layers. This segmentation allows the circuit to achieve high interconnectivity without increasing the number of crossings within a single layer, thus preventing accumulation of optical loss and crosstalk.
2Adaptability or versatility
If waveguide crossings are increased to enable large-scale photonic circuits, then interconnectivity is improved, but crosstalk accumulates
Solution Approach 1:
By moving waveguide crossings into the vertical dimension through stacked layers, the patent eliminates lateral overlap between crossing waveguides. This spatial separation in the vertical dimension prevents evanescent field coupling between crossing waveguides, thereby reducing crosstalk while maintaining high interconnectivity in large-scale circuits.
Solution Approach 2:
The patent introduces intermediate structures such as trenches or low-index materials between waveguides in adjacent layers to act as optical isolators. These intermediaries prevent optical coupling between waveguides from different layers, reducing crosstalk while allowing the waveguides to maintain their routing functions.
3Adaptability or versatility
If long optical paths are used in large switch matrices, then routing capability is improved, but scattering loss accumulates
Solution Approach 1:
The stacked layer configuration allows optical paths to be routed through multiple layers, effectively shortening the lateral propagation distance required to achieve the same routing capability. By utilizing vertical transitions between layers, the patent reduces the total path length and consequently minimizes the accumulation of scattering loss while maintaining comprehensive routing capability.
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
This design significantly reduces unwanted crosstalk and optical loss, enabling efficient light transmission and interconnectivity in photonic switches, thereby improving the optical performance and component density of silicon photonic devices.
Implementation Method 1
rib waveguides protruding upwardly from the slab... upper waveguide that crosses over the one or more rib waveguides
Data Source
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AI summary
A photonic platform includes a substrate, a buried oxide layer on the substrate, a first optical layer on the buried oxide layer, the first optical layer including one or more waveguides shaped as rib waveguides protruding upwardly from a common underlying slab and a second optical layer spaced above the first optical layer, the second optical layer defining an upper waveguide that crosses over the one or more partially etched waveguides. A low-loss photonic switch may be made using a silicon photonic platform implementing this waveguide crossing.