Multimode Waveguide Bends with Curved Strips to Reduce Loss

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Solution Overview

Problem

Waveguide bends in photonics chips experience significant bending losses due to inter-modal mixing and interference, which are minimized by large bending radii but at the cost of reduced space for other components, necessitating improved structural designs.

Innovation Solution

A waveguide bend structure with a central region and side regions of varying thicknesses, where the side regions are thinner than the central region, and optionally enhanced with curved strips, to minimize mode mixing and reduce bending losses while preserving the fundamental mode.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a large bending radius is used to minimize bending losses, then signal integrity is improved, but the area occupied by the waveguide bend increases

Engineering Contradiction:

Improvesignal integrityVSAvoidwaveguide bend area

Core Design Contradiction:

ReliabilityVSArea of stationary object

Solution Approach 1:

The waveguide bend structure implements local quality by creating side regions with different thicknesses compared to the central region. The side regions have reduced thickness (second thickness) relative to the central region (first thickness), creating localized structural variations that modify optical mode propagation. This differential thickness structure reduces mode mixing and interference effects specifically at the bend regions while preserving the fundamental mode, thereby reducing bending losses without requiring a large bending radius.

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If a large bending radius is used to reduce inter-modal mixing, then mode purity is improved, but the device complexity increases due to larger layout requirements

Engineering Contradiction:

Improvemode purityVSAvoidlayout complexity

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

The patent applies local quality by introducing thickness variations specifically in the side regions of the waveguide bend, while the central region maintains its original thickness. This localized structural modification targets the specific problem of mode mixing at the bend without requiring changes to the overall layout or bending radius, thereby maintaining mode purity with a compact design.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The waveguide bend is segmented into distinct regions: a central region with first thickness and side regions with second thickness. This segmentation allows independent optimization of different functional zones within the bend structure, enabling the central region to maintain mode propagation while the side regions provide structural modification to reduce inter-modal mixing, achieving mode purity in a compact configuration.

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS11275207B2Multimode waveguide bends with features to reduce bending loss

Publication Date: 2022.03.15 GLOBALFOUNDRIES US INC

AI summary

Structures for a waveguide bend and methods of fabricating a structure for a waveguide bend. A waveguide core has a first section, a second section, and a waveguide bend connecting the first section with the second section. The waveguide core includes a first side surface extending about an inner radius of the waveguide bend and a second side surface extending about an outer radius of the waveguide bend. A curved strip is arranged over the waveguide bend adjacent to the first side surface or the second side surface.