Non-Contacting Waveguide Crossings for Low-Loss Photonic Routing

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Solution Overview

Problem

Waveguide crossings in photonics chips experience significant insertion loss and high cross-talk due to strong light scattering caused by the close local proximity of waveguide cores in different levels, necessitating improved structures and fabrication methods.

Innovation Solution

A non-contacting waveguide crossing structure is designed with a gap between waveguide bends to promote light transfer, utilizing overlapping and non-overlapping arrangements of waveguide cores, and incorporating dielectric material to reduce scattering, thereby minimizing insertion loss while maintaining low cross-talk.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If waveguide cores are arranged in multiple levels with close local proximity, then layout area is reduced, but insertion loss increases and cross-talk increases due to strong light scattering

Engineering Contradiction:
Improvelayout areaVSAvoidinsertion loss
Core Design Contradiction:
Area of stationary objectVSLoss of energy

Solution Approach 1:

The patent introduces a vertical dimension by spacing waveguide bends at different heights (first level and second level) to create a three-dimensional non-contacting crossing structure. This vertical separation allows waveguide cores to cross without physical contact while maintaining compact lateral footprint, thereby reducing insertion loss and cross-talk caused by close proximity in planar arrangements.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent introduces a dielectric material as an intermediary substance filling the gap between the first waveguide core and second waveguide core. This dielectric intermediary reduces light scattering and evanescent field coupling between the waveguides, thereby minimizing insertion loss and cross-talk while enabling compact routing.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Area of stationary object

If waveguide cores are arranged in multiple levels with close local proximity, then layout area is reduced, but cross-talk increases due to strong light scattering

Engineering Contradiction:
Improvelayout areaVSAvoidcross-talk
Core Design Contradiction:
Area of stationary objectVSObject-generated harmful factors

Solution Approach 1:

The patent introduces a vertical dimension by spacing waveguide bends at different heights (first level and second level) to create a three-dimensional non-contacting crossing structure. This vertical separation allows waveguide cores to cross without physical contact while maintaining compact lateral footprint, thereby reducing insertion loss and cross-talk caused by close proximity in planar arrangements.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent introduces a dielectric material as an intermediary substance filling the gap between the first waveguide core and second waveguide core. This dielectric intermediary reduces light scattering and evanescent field coupling between the waveguides, thereby minimizing insertion loss and cross-talk while enabling compact routing.

Inventive Principle:
Principle #24Intermediary (Mediator)

3Loss of energy

If a gap is introduced between waveguide bends to permit light transfer, then insertion loss is reduced, but device complexity increases

Engineering Contradiction:
Improveinsertion lossVSAvoiddevice complexity
Core Design Contradiction:
Loss of energyVSDevice complexity

Solution Approach 1:

The patent segments the waveguide structure into distinct sections: straight waveguide sections and bent waveguide sections positioned at different vertical levels. This segmentation allows the creation of a non-contacting crossing with controlled gaps between bends, enabling light transfer while maintaining manufacturing feasibility through standardized fabrication processes.

Inventive Principle:
Principle #1Segmentation

Solution Approach 2:

The patent resolves the complexity issue by utilizing vertical spacing between waveguide bends at different levels. This three-dimensional arrangement achieves the required gap for light transfer without requiring complex lateral routing or additional components, as the vertical separation is naturally achieved through multi-level waveguide core positioning.

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 structure reduces insertion loss and cross-talk, enabling efficient light transfer without physical contact between waveguide cores, suitable for high-density and large-scale photonics chip applications.

Implementation Method 1

the gap having a distance that promotes light transfer between the first waveguide core and the second waveguide core

Methodology Applied
Scientific EffectEvanescent field coupling:

Implementation Method 2

significant insertion loss and high cross-talk due to strong light scattering induced by the close local proximity of the waveguide cores

Methodology Applied
Scientific EffectLight scattering: Scattering

Data Source

PatentEP4310561B1Waveguide crossings with a multiple-level non-contacting arrangement
Publication Date: 2025.12.31 GLOBALFOUNDRIES US INC
  • EP4310561B1 patent drawingFigure 1~2
  • EP4310561B1 patent drawingFigure 3~4
  • EP4310561B1 patent drawingFigure 4A~5

AI summary

Structures for a waveguide crossing and methods of fabricating a structure for a waveguide crossing. The structure comprises a first waveguide core and a second waveguide core each including a first section, a second section, and a first waveguide bend connecting the first section to the second section. The second section terminates the first waveguide core. The second section terminates the second waveguide core. The second waveguide bend has a side surface that is spaced from a side surface of the first waveguide bend by a gap. A third waveguide core is terminated by a section having an overlapping arrangement with the second section of the first waveguide core. A fourth waveguide core is terminated by a section having an overlapping arrangement with the second section of the second waveguide core.