Multi-Core Silicon Waveguide for Photonic Edge Coupler

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Solution Overview

Problem

Existing silicon photonic edge couplers face limitations in coupling efficiency due to trade-offs between coupler length and insertion loss, particularly in achieving efficient coupling between optical fibers or laser diodes and silicon photonic waveguides, where a larger mode size is desired for broad-bandwidth applications but results in reduced coupling strength.

Innovation Solution

A mode-converting optical coupler design featuring a multi-core primary waveguide that enhances coupling strength between the secondary and primary waveguides, reducing coupler length and insertion loss by utilizing a central core structure and neighboring core structures made of silicon, which taper to improve spatial overlap and adiabatic coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If a larger mode size is used in the secondary waveguide for broad-bandwidth applications, then the coupling bandwidth is improved, but the coupling strength between the secondary and primary waveguide is reduced

Engineering Contradiction:

Improvecoupling bandwidthVSAvoidcoupling strength

Core Design Contradiction:

Adaptability or versatilityVSStrength

Solution Approach 1:

The primary waveguide is segmented into multiple cores (at least three cores arranged in a triangle configuration), which collectively provide enhanced coupling strength to the secondary waveguide while maintaining the required mode size for broad bandwidth operation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Multiple core structures are merged into a single primary waveguide system that acts as a unified coupling interface to the secondary waveguide, combining their individual coupling contributions to achieve sufficient overall coupling strength

Inventive Principle:

Principle #5Merging (Combining)

2Volume of moving object

If the coupler length is reduced to improve device compactness, then the device size is reduced, but the insertion loss increases due to insufficient adiabatic coupling

Engineering Contradiction:

Improvedevice sizeVSAvoidinsertion loss

Core Design Contradiction:

Volume of moving objectVSLoss of energy

Solution Approach 1:

The multi-core structure distributes the coupling interaction across multiple core-waveguide interfaces, enabling sufficient total coupling strength over a shorter interaction length while maintaining adiabatic conditions

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The primary waveguide uses a composite multi-core structure with silicon cores in a silicon oxide cladding, optimizing the refractive index distribution to enhance coupling efficiency over reduced lengths

Inventive Principle:

Principle #40Composite materials

3Strength

If the width of the primary waveguide is increased to improve coupling strength, then the coupling strength is improved, but the mode size mismatch with the secondary waveguide worsens

Engineering Contradiction:

Improvecoupling strengthVSAvoidmode size matching

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The primary waveguide is divided into multiple smaller cores rather than one large core, allowing each core to maintain appropriate mode size for matching the secondary waveguide while the collective structure provides enhanced coupling strength

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each core in the multi-core structure has locally optimized dimensions to achieve proper mode matching with the secondary waveguide, while the overall multi-core configuration provides the required coupling strength

Inventive Principle:

Principle #3Local quality

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 multi-core primary waveguide design effectively reduces the length of the mode-converting optical coupler and minimizes insertion loss, enabling efficient coupling over a broader wavelength range while maintaining adiabatic conditions, thus addressing the limitations of prior art edge couplers.

Implementation Method 1

a mode-converting optical coupler may include: a secondary waveguide to guide light in one or more secondary optical modes; and a primary waveguide, to guide light in one or more primary optical modes

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Implementation Method 2

each adiabatically coupled to a secondary optical mode of the secondary waveguide having a secondary mode index, wherein each primary optical mode of the primary waveguide has a first primary mode index near a first end and a second primary mode index near a second end

Methodology Applied

Scientific EffectAdiabatic coupling:

Data Source

PatentUS10345522B2Multi-core silicon waveguide in a mode-converting silicon photonic edge coupler

Publication Date: 2019.07.09 WELLS FARGO BANK NA

AI summary

A mode-converting optical coupler may include a secondary waveguide to guide light in one or more secondary optical modes, and a primary waveguide to guide light in one or more primary optical modes, each adiabatically coupled to a secondary optical mode of the secondary waveguide having a secondary mode index. Each primary optical mode of the primary waveguide may have a first primary mode index near a first end and a second primary mode index near a second end. The first primary mode index may be lower than the second primary mode index. The secondary mode index may be between the first primary mode index and the second primary mode index. The primary waveguide may include a plurality of silicon core structures including a central core structure arranged between a first neighboring core structure and a second neighboring core structure.