Silicon Photonic Waveguide Sidewall Loss Reduction
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Solution Overview
Problem
Silicon photonic devices experience power-dependent optical loss due to dangling covalent bonds at etched sidewalls, leading to increased loss with higher optical power, which restricts design, reduces bandwidth, and decreases receiver sensitivity.
Innovation Solution
The design of a silicon-based optical waveguide with specific geometric features, including central and wing ridge portions and connecting portions, along with a concentrator, reduces the interaction of the optical mode with sidewalls, thereby minimizing free carrier generation and power-dependent loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional silicon waveguide with etched sidewalls is used, then light guiding function is achieved, but power-dependent optical loss increases due to dangling covalent bonds at sidewalls
Solution Approach 1:
The patent removes the harmful etched sidewalls by forming a trench isolation structure that completely encapsulates the silicon waveguide. This extraction of the problematic sidewall region eliminates the dangling covalent bonds that cause power-dependent loss, while maintaining the light guiding function through the isolated waveguide structure.
Solution Approach 2:
The patent introduces an intermediary dielectric material (such as silicon nitride or silicon oxide) to fill and cap the waveguide structure. This intermediary layer acts as a mediator that provides a smooth, non-harmful surface replacing the etched sidewalls, thereby eliminating the harmful dangling bonds while maintaining optical confinement.
2Power
If higher optical power is used to compensate for loss, then signal strength is maintained, but power-dependent loss increases quadratically
Solution Approach 1:
The patent converts the previously harmful effect of sidewall interaction into a beneficial configuration by using the trench isolation structure to create a controlled optical confinement environment. The isolation structure that was designed to prevent harmful sidewall effects now provides beneficial optical confinement, allowing higher optical powers to be transmitted with reduced quadratic loss.
3Ease of manufacture
If waveguide structure is simplified, then manufacturing is easier, but optical mode interaction with sidewalls increases
Solution Approach 1:
The patent segments the waveguide structure into distinct functional regions: the silicon waveguide core for light guiding, the trench isolation structure for confinement, and the dielectric capping layer for protection and smooth surface formation. This segmentation allows each component to be optimized independently, maintaining ease of manufacture while reducing optical mode interaction with harmful sidewalls.
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 effectively reduces power-dependent optical loss by diffusing free carriers over a larger area, increasing carrier recombination rates and maintaining high light confinement within the waveguide structure.
Implementation Method 1
An insulator 12 is etched to form a rib 14 of silicon which guides light
Implementation Method 2
When these dangling covalent bonds absorb light, they generate free carriers, which contribute to optical loss
Data Source
AI summary
Optical waveguides may include a substrate and a silicon based optical waveguide supported on the substrate. The silicon based optical waveguide may include a central ridge portion and a plurality of spaced apart wing portions connected through connecting portions. The number of wing portions may be greater than two. The central ridge portion may have a central ridge lateral width extent greater than a lateral width extent of at least one of the wing portions. Optical waveguides may include a substrate, a silicon based optical waveguide supported on the substrate, and a concentrator supported on the substrate and positioned within a lateral width extent of the silicon based optical waveguide and outside of a height extent of the silicon based optical waveguide. The optical waveguides may be included as part of an optical modulator.