Grating Coupler Silicide Mirror for Signal Loss Reduction
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Solution Overview
Problem
Grating couplers in photonics chips suffer from low coupling efficiency, leading to unacceptably high losses in optical signal transmission between waveguides and optical fibers.
Innovation Solution
A structure comprising a semiconductor layer with a silicide layer and a grating coupler having a plurality of grating structures positioned over the silicide layer, where the silicide layer is formed through a self-aligned silicidation process, and a dielectric layer is used to intervene between the grating structures and the semiconductor layer, enhancing the coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional grating coupler structure is used, then the device complexity is low, but the coupling efficiency is low leading to high signal loss
Solution Approach 1:
The patent employs a composite structure consisting of a semiconductor layer combined with a silicide layer (such as nickel silicide) to form a mirror beneath the grating coupler. This composite material approach creates a reflective surface that redirects otherwise lost optical signals back into the waveguide, thereby reducing signal loss without requiring a fundamentally new device architecture.
Solution Approach 2:
The silicide mirror acts as an intermediary element between the grating coupler and the substrate. It mediates the optical field by reflecting evanescent waves back into the guiding mode, effectively converting non-useful optical energy back into useful signal transmission without requiring direct modification of the grating structures themselves.
2Loss of energy
If the grating coupler structure is enhanced to improve coupling efficiency, then the signal loss is reduced, but the layout area increases
Solution Approach 1:
Instead of expanding the grating coupler footprint in the lateral plane to improve coupling efficiency, the patent introduces a vertical dimension by placing a reflective silicide mirror beneath the grating structure. This dimensional transition allows the system to enhance performance through vertical optical path management rather than lateral expansion.
Solution Approach 2:
The patent modifies the optical parameters of the existing grating coupler structure by introducing a layer with different refractive index characteristics (the silicide mirror). This parameter change alters the optical field distribution and reflection characteristics, improving coupling efficiency without changing the physical dimensions of the grating structures.
3Area of stationary object
If the grating coupler structure is modified to reduce layout area, then the integration density is improved, but the coupling efficiency may deteriorate
Solution Approach 1:
The silicide mirror is formed in advance during the fabrication process, before the grating coupler structures are finalized. This preliminary action ensures that the reflective surface is already in place to capture and redirect optical signals, maintaining high coupling efficiency even when the grating structures are compacted to reduce layout area.
Solution Approach 2:
The silicide mirror provides a self-service function by automatically reflecting optical signals that would otherwise be lost into the substrate. This passive reflective action occurs without requiring additional active components or complex structures, allowing compact grating designs to maintain high coupling efficiency through the mirror's inherent optical feedback mechanism.
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 improves coupling efficiency by reducing operational overhead and layout area, thereby minimizing signal loss in photonics chips, facilitating more effective integration of optical and electronic components.
Implementation Method 1
grating couplers with a silicide mirror
Data Source
AI summary
Structures for a grating coupler and methods of fabricating a structure for a grating coupler. A silicide layer is formed on a patterned section of a semiconductor layer. The grating structures of a grating coupler are formed over the silicide layer and the section of the semiconductor layer.