Dual-Trapezoidal Waveguide Core for Edge Coupler Mode Matching

Solution Overview

Problem

The existing edge couplers in photonics chips face challenges in fully confining the incident mode due to the small cross-sectional area at the tip of the inverse taper, leading to significant electromagnetic field distribution and increased optical coupling loss.

Innovation Solution

A waveguide core structure with dual-trapezoidal tapered sections is introduced, where the tapered sections have different trapezoidal shapes, allowing for improved mode confinement and reduced optical coupling loss through a gradual increase in width, and the use of chamfered upper corners to enhance the trapezoidal shape alignment.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the cross-sectional area at the tip of the inverse taper is reduced to enable mode transformation, then mode size variation is supported, but electromagnetic field confinement deteriorates

Engineering Contradiction:

Improvemode transformation capabilityVSAvoidelectromagnetic field distribution

Core Design Contradiction:

Adaptability or versatilityVSObject-generated harmful factors

Solution Approach 1:

The waveguide core is divided into multiple sections with different cross-sectional areas: a first section with a first cross-sectional area, a second section with a second cross-sectional area smaller than the first, and a third section with a third cross-sectional area smaller than the second. This segmentation allows progressive mode transformation while maintaining field confinement at each stage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the waveguide core are assigned different local geometric properties (different cross-sectional areas) to optimize their specific functions. The first section provides initial mode confinement, the second section enables mode transformation, and the third section completes the mode matching, with each section having locally optimized dimensions.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If the tip cross-sectional area is made small to achieve inverse taper configuration, then mode conversion is supported, but optical coupling loss increases

Engineering Contradiction:

Improvemode conversion capabilityVSAvoidoptical coupling loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The waveguide core is divided into multiple sections with different cross-sectional areas: a first section with a first cross-sectional area, a second section with a second cross-sectional area smaller than the first, and a third section with a third cross-sectional area smaller than the second. This segmentation allows progressive mode transformation while maintaining field confinement at each stage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the waveguide core are assigned different local geometric properties (different cross-sectional areas) to optimize their specific functions. The first section provides initial mode confinement, the second section enables mode transformation, and the third section completes the mode matching, with each section having locally optimized dimensions.

Inventive Principle:

Principle #3Local quality

3Ease of manufacture

If the waveguide core uses a single trapezoidal shape, then fabrication is simplified, but mode matching precision is insufficient

Engineering Contradiction:

Improvefabrication simplicityVSAvoidmode matching precision

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The waveguide core is divided into multiple sections with different cross-sectional areas: a first section with a first cross-sectional area, a second section with a second cross-sectional area smaller than the first, and a third section with a third cross-sectional area smaller than the second. This segmentation allows progressive mode transformation while maintaining field confinement at each stage.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the waveguide core are assigned different local geometric properties (different cross-sectional areas) to optimize their specific functions. The first section provides initial mode confinement, the second section enables mode transformation, and the third section completes the mode matching, with each section having locally optimized dimensions.

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 dual-trapezoidal shape waveguide core effectively improves mode matching and reduces optical coupling loss, enhancing the efficiency of light transfer between the light source and the photonics chip.

Implementation Method 1

The gradually-varying cross-sectional area of the inverse taper supports mode transformation and mode size variation associated with mode conversion when light is transferred from the light source to the edge coupler

Methodology Applied

Scientific EffectMode transformation and mode size variation: Waveguide (optics)

Data Source

PatentUS12135456B2Waveguide cores with a dual-trapezoidal shape

Publication Date: 2024.11.05 GLOBALFOUNDRIES US INC

AI summary

Structures for a waveguide core and methods of fabricating such structures. The structure comprises a waveguide core including a section having a first trapezoidal portion and a second trapezoidal portion stacked with the first trapezoidal portion. The first trapezoidal portion has a first trapezoidal shape, and the second trapezoidal portion has a second trapezoidal shape different from the first trapezoidal shape.