Stacked Polarization Splitter Layout for Compact Low-Loss Photonic Chips

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Solution Overview

Problem

Conventional polarization splitters in photonic chips have a large footprint and exhibit high loss, necessitating improved structures and methods for more efficient polarization splitting.

Innovation Solution

A polarization splitter structure comprising a multimode interference region with overlapping waveguide cores and stacked multimode interference regions, utilizing materials with varying refractive indices and angled connections to enhance polarization mode separation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of stationary object

If conventional polarization splitter structures are used, then polarization splitting function is achieved, but the footprint area is large

Engineering Contradiction:
Improvefootprint areaVSAvoidpolarization splitting performance
Core Design Contradiction:
Area of stationary objectVSReliability

Solution Approach 1:

The patent transitions from a planar two-dimensional waveguide structure to a three-dimensional stacked structure with multiple interference regions at different vertical levels. The first and second multimode interference regions are positioned at different heights, creating a vertical stacking arrangement that reduces horizontal footprint while maintaining splitting functionality through three-dimensional optical path manipulation

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

Solution Approach 2:

The patent implements a nested configuration where the second multimode interference region is positioned to overlap with the first multimode interference region in the horizontal plane, while being separated vertically. This nesting approach allows compact spatial arrangement that minimizes the overall footprint area while preserving the necessary optical interference paths for polarization splitting

Inventive Principle:
Principle #7Nested doll (Nesting)

2Loss of energy

If conventional polarization splitter structures are used, then polarization splitting function is achieved, but the loss is high

Engineering Contradiction:
Improveoptical lossVSAvoidpolarization splitting performance
Core Design Contradiction:
Loss of energyVSReliability

Solution Approach 1:

The patent modifies the effective refractive index parameter by introducing a third material with a refractive index different from the first and second materials in the overlapping region. This parameter change creates a controlled index gradient that reduces optical loss through improved mode matching and reduced reflection at interfaces between regions with different refractive indices

Inventive Principle:
Principle #35Parameter changes

Solution Approach 2:

The patent employs a composite material structure consisting of three distinct materials: a first material in the first multimode interference region, a second material in the second multimode interference region, and a third material in the overlapping region. This composite approach optimizes optical performance by selecting materials with specific refractive indices to minimize loss while maintaining polarization splitting functionality

Inventive Principle:
Principle #40Composite materials

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 structure achieves more efficient polarization splitting with reduced footprint by increasing the difference in effective refractive index between polarization modes, thereby improving performance and reducing size.

Implementation Method 1

a first multimode interference region, a second multimode interference region

Methodology Applied
Scientific EffectMultimode interference: Interference

Implementation Method 2

a first waveguide core adjoined to a first portion of the first multimode interference region at a first acute angle, a second waveguide core adjoined to a second portion of the first multimode interference region at a second acute angle

Methodology Applied
Scientific EffectRefraction: Refraction

Data Source

PatentEP4707885A1Polarization splitters for a photonic chip
Publication Date: 2026.03.11 GLOBALFOUNDRIES US INC
  • EP4707885A1 patent drawingFigure 1
  • EP4707885A1 patent drawingFigure 2~2A
  • EP4707885A1 patent drawingFigure 3

AI summary

Structures for a polarization splitter and methods of forming such structures. The structure comprises a multimode interference structure including a first multimode interference region, a second multimode interference region, a first waveguide core adjoined to a first portion of the first multimode interference region at a first acute angle, a second waveguide core adjoined to a second portion of the first multimode interference region at a second acute angle, and a third waveguide core adjoined to a third portion of the first multimode interference region. The second multimode interference region has an overlapping relationship with the first multimode interference region.