Cascaded Tapered Optical Ring Resonators for Process Variation Tolerance
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Solution Overview
Problem
Integrated high-speed silicon-photonics devices, such as cascaded ring resonators, are sensitive to process variations, leading to poor performance due to mismatches between rings, which results in increased insertion loss and reduced yield.
Innovation Solution
The implementation of cascaded ring resonators with rings having varying waveguide widths, featuring wide and narrow portions, minimizes mismatch between rings by altering the waveguide geometry to support whispering gallery modes and suppress higher order modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If cascaded ring resonators are used in wavelength division multiplexing systems, then bandwidth and energy efficiency are improved, but sensitivity to process variations increases causing poor performance
Solution Approach 1:
The waveguide width is varied locally around the ring resonator circumference, creating different width portions (first, second, third, fourth waveguide width portions) at different locations. This local variation in waveguide geometry allows for compensation of process variations while maintaining the overall ring resonator functionality and bandwidth performance.
Solution Approach 2:
The waveguide width parameter is changed along the length of the ring resonator, creating a non-uniform waveguide structure. By varying the waveguide width from the first width portion to the second width portion and from the third width portion to the fourth width portion, the resonator becomes less sensitive to process variations while maintaining its wavelength-selective properties.
2Ease of manufacture
If uniform waveguide width is used in ring resonators, then manufacturing is simplified, but mismatch between rings increases leading to higher insertion loss
Solution Approach 1:
Different portions of the waveguide are assigned different widths (first, second, third, fourth waveguide width portions) to create local variations that compensate for process variations. This local quality differentiation reduces mismatch between cascaded rings and minimizes insertion loss while maintaining manufacturability through standard photolithography processes.
Solution Approach 2:
The waveguide structure transitions from a symmetric uniform width design to an asymmetric non-uniform width design. By introducing asymmetry in the waveguide width around the ring circumference, the system becomes more robust to process variations and achieves better performance with lower insertion loss.
3Productivity
If multiple propagating modes are supported in the waveguide, then bandwidth is increased, but mode coupling and interference increase degrading signal quality
Solution Approach 1:
The waveguide width is optimized at different locations to support only a single propagating mode. By creating specific width portions (first, second, third, fourth waveguide width portions) with carefully controlled dimensions, the design ensures single-mode operation while maintaining sufficient bandwidth for the application.
Solution Approach 2:
Instead of designing for multiple modes which would provide excessive bandwidth, the design uses partial action by optimizing for single-mode operation. This partial approach (supporting only one mode) is sufficient for the application requirements and avoids the harmful effects of mode coupling while achieving the necessary bandwidth performance.
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 reduces insertion loss and increases the yield of photonic integrated circuits by minimizing the impact of process variations and ensuring only a single propagating mode is supported, thereby enhancing the performance and reliability of the cascaded ring resonators.
Implementation Method 1
altering a geometry of the waveguides of the rings of the cascaded ring resonator... configured to support only a single propagating mode... support whispering gallery modes and suppress higher order modes
Data Source
AI summary
Embodiments herein describe a method for selectively filtering different wavelengths of optical signals received from an optical channel using cascaded ring resonators, each of the cascaded ring resonators having a first ring and a second ring. The first ring has a varying waveguide width along its length configured to form a first waveguide width portion and a second waveguide width portion, the first waveguide width portion having a greater width than the second waveguide width portion. The second ring has a varying waveguide width along its length configured to form a third waveguide width portion and a fourth waveguide width portion, the fourth waveguide width portion having a greater width than the third waveguide width portion. The method further connects receivers to respective cascaded ring resonators, each of the receivers having a photodetector configured to differentiate between the optical signals.