Gratings with Non-Rectangular Segments for Edge Couplers

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Solution Overview

Problem

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 around the tip.

Innovation Solution

A grating structure with first and second segments positioned along the longitudinal axis in a spaced-apart arrangement, where the sidewalls of these segments are sloped at specific angles relative to the longitudinal axis, effectively reducing optical return loss by redirecting reflected light.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the cross-sectional area of the inverse taper tip is reduced to match the light source mode size, then mode transformation is improved, but electromagnetic field confinement deteriorates

Engineering Contradiction:

Improvemode transformationVSAvoidelectromagnetic field confinement

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The grating structure is divided into multiple segments (first grating segment, second grating segment, etc.) positioned at different locations along the waveguide core. Each segment can be independently designed with specific dimensions and spacing to optimize both mode transformation and field confinement effects.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The grating segments are positioned at specific locations along the longitudinal axis where they provide localized effects. The first grating segment is positioned to work with the incident mode from the light source, while subsequent segments are positioned to manage reflected light and enhance confinement in specific regions.

Inventive Principle:

Principle #3Local quality

2Reliability

If the inverse taper width is increased to confine the electromagnetic field, then field confinement is improved, but mode transformation capability deteriorates

Engineering Contradiction:

Improveelectromagnetic field confinementVSAvoidmode transformation

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The grating is segmented into multiple sections positioned at different locations. The first grating segment interacts with the incident mode for transformation, while subsequent segments handle reflected light and confinement, allowing each segment to be optimized for its specific function.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The solution moves from a single-dimensional inverse taper structure to a multi-dimensional grating structure with segments positioned along the longitudinal axis. This adds a longitudinal dimension to the field confinement mechanism, allowing confinement to be achieved through distributed grating segments rather than solely through taper width.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

3Ease of manufacture

If a conventional grating structure is used in the edge coupler, then manufacturing is simplified, but optical return loss increases

Engineering Contradiction:

Improvegrating structure fabricationVSAvoidoptical return loss

Core Design Contradiction:

Ease of manufactureVSLoss of energy

Solution Approach 1:

The grating is divided into multiple segments positioned at different locations along the waveguide core. This segmentation allows the structure to address multiple optical issues simultaneously: the first segment handles mode transformation while subsequent segments manage reflected light and reduce return loss through their positioned geometry.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Each grating segment is positioned at a specific location where it provides localized optical management. The segments are positioned to specifically address reflected light from the inverse taper tip, providing local optimization for reducing optical return loss while maintaining manufacturability.

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 proposed grating structure enhances the confinement of the electromagnetic field, reducing optical return loss and improving the efficiency of light transfer from the light source to the photonics chip.

Implementation Method 1

The first sidewall of the first segment is positioned adjacent to the first sidewall of the second segment... effectively reducing optical return loss by redirecting reflected light

Methodology Applied

Scientific EffectLight reflection: Reflection

Implementation Method 2

The waveguide core includes a longitudinal axis and a grating... enhances the confinement of the electromagnetic field... improving the efficiency of light transfer

Methodology Applied

Scientific EffectWaveguide confinement: Waveguide (optics)

Data Source

PatentUS12339495B2Gratings with non-rectangular segments

Publication Date: 2025.06.24 GLOBALFOUNDRIES US INC

AI summary

Structures for a grating that may be deployed in edge coupler and methods of forming such structures. The structure comprises a waveguide core positioned on a substrate. The waveguide core includes a longitudinal axis and a grating having first and second segments positioned along the longitudinal axis in a spaced-apart arrangement. The first segment has a first sidewall sloped at a first angle relative to the longitudinal axis and a second sidewall oriented transverse to the longitudinal axis. The second segment has a first sidewall sloped at a second angle relative to the longitudinal axis and a second sidewall oriented transverse to the longitudinal axis. The first sidewall of the first segment positioned adjacent to the first sidewall of the second segment.