Multi-Stage Edge Coupler Tapers for Low-Loss Mode Confinement

Solution Overview

Problem

Existing edge couplers struggle to fully confine the electromagnetic field of incident modes due to the tip's smaller cross-sectional area, leading to significant mode distribution and increased insertion loss.

Innovation Solution

The edge coupler structure features non-linearly varying tapered sections with concave sidewalls, allowing for adiabatic mode evolution and reduced radiative losses, combined with a suspended design to minimize light loss to the substrate.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the tip cross-sectional area is reduced to enable mode transformation, then mode conversion is supported, but electromagnetic field confinement deteriorates

Engineering Contradiction:

Improvemode transformation capabilityVSAvoidelectromagnetic field confinement

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The waveguide core is divided into multiple tapered sections with different taper ratios arranged in sequence. The first tapered section has a first taper ratio, and the second tapered section has a second taper ratio different from the first. This segmentation allows each section to perform specific mode transformation functions while collectively achieving better field confinement than a single tapered section could provide.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the waveguide core are given different local geometrical properties through varying taper ratios. The first tapered section and second tapered section have distinct local characteristics optimized for their respective positions in the mode transformation process, enabling both adaptability and confinement to be addressed locally in different regions.

Inventive Principle:

Principle #3Local quality

2Device complexity

If a single tapered section is used, then device complexity is reduced, but insertion loss increases

Engineering Contradiction:

Improvetapered section structureVSAvoidinsertion loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The waveguide core is divided into multiple tapered sections with different taper ratios arranged in sequence. The first tapered section has a first taper ratio, and the second tapered section has a second taper ratio different from the first. This segmentation allows each section to perform specific mode transformation functions while collectively achieving better field confinement than a single tapered section could provide.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the waveguide core are given different local geometrical properties through varying taper ratios. The first tapered section and second tapered section have distinct local characteristics optimized for their respective positions in the mode transformation process, enabling both adaptability and confinement to be addressed locally in different regions.

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 non-linear tapered sections significantly reduce insertion loss and provide a flatter frequency response, improving the coupling efficiency and mitigating mode hybridization for large mode sizes.

Implementation Method 1

The non-linear end configuration of the inverse taper enables adiabatic mode evolution

Methodology Applied

Scientific EffectAdiabatic mode evolution:

Implementation Method 2

The gradual variation in the cross-sectional area of the inverse taper supports mode transformation and mode size variation associated with mode conversion

Methodology Applied

Scientific EffectMode transformation:

Data Source

PatentUS20250370185A1Edge couplers with multiple stages

Publication Date: 2025.12.04 GLOBALFOUNDRIES US INC

AI summary

Structures for an edge coupler and methods of forming such structures. The structure comprises a waveguide core including a facet, a first tapered section, a second tapered section, and a longitudinal axis. The first tapered section is positioned along the longitudinal axis between the second tapered section and the facet. The first tapered section has a first width dimension that varies non-linearly with position along the longitudinal axis. The second tapered section has a second width dimension that varies non-linearly with position along the longitudinal axis.