Silicon Photonics Grating Coupler Alignment Tolerance
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Solution Overview
Problem
The existing silicon grating coupler configuration in optoelectronic integrated circuits has limited alignment tolerance, which is insufficient for applications like automated wafer scale testing and packaging that require greater precision.
Innovation Solution
The introduction of a second optical waveguide with a dielectric core, indirectly coupled to a grating coupler with dielectric or semiconductor fins, provides increased alignment tolerance by using dielectric layers with different refractive indices to expand the light beam diameter and improve coupling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a silicon grating coupler is formed adjacent to one end of a silicon optical waveguide on the same horizontal plane, then the structure is simple and easy to manufacture, but the alignment tolerance is relatively small
Solution Approach 1:
The patent introduces a second optical waveguide with a dielectric core that is vertically offset from the first silicon waveguide, creating a three-dimensional stacked configuration. This vertical dimensionality change allows the grating coupler to be positioned at a different height, thereby increasing alignment tolerance without complicating the horizontal manufacturing process
Solution Approach 2:
The second optical waveguide with dielectric core acts as an intermediary between the first silicon waveguide and the grating coupler. This intermediate waveguide expands the light beam diameter and provides a transition path that improves coupling efficiency and alignment tolerance while maintaining manufacturing simplicity
2Manufacturing precision
If a second optical waveguide with dielectric core is introduced to increase alignment tolerance, then alignment tolerance and coupling efficiency are improved, but the device complexity increases
Solution Approach 1:
The patent changes the refractive index parameter by introducing a dielectric core with different refractive index properties compared to the silicon waveguide. This parameter change enables beam expansion and improved coupling while the standardized multi-layer dielectric structure keeps the overall device complexity manageable through conventional fabrication processes
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 configuration enhances alignment tolerance and coupling efficiency, allowing for improved light signal propagation and alignment in optoelectronic integrated circuits, particularly in applications requiring higher precision.
Implementation Method 1
using dielectric layers with different refractive indices to expand the light beam diameter and improve coupling efficiency
Data Source
AI summary
Disclosed are optoelectronic integrated circuit structures that incorporate a first optical waveguide, having a semiconductor core, indirectly coupled to a grating coupler through a second optical waveguide, having a dielectric core, in order provide a relatively large alignment tolerance. The dielectric core can comprise multiple dielectric layers above one end of the semiconductor core and extending laterally over an isolation region adjacent to that end. The grating coupler can include dielectric fins above the isolation region. Alternatively, the grating coupler can include semiconductor fins within the isolation region. Also disclosed herein are methods of forming such optoelectronic integrated circuit structures that can be readily integrated with complementary metal oxide semiconductor (CMOS) device processing and germanium photodetector processing.