Stacked Waveguide Polarizer for Compact Photonic Integration

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Solution Overview

Problem

Polarizers in photonics chips have large footprints, consuming significant layout area and increasing operational overhead, as they are designed to pass the TM mode while eliminating the TE mode, which is not efficiently managed by existing structures.

Innovation Solution

A polarizer structure incorporating a waveguide core with tapered sections and a truncated waveguide core, where the tapered sections narrow towards a central section, and the truncated waveguide core is positioned over or under the waveguide core, enhancing the efficiency of lateral coupling and absorption of the TE mode, thereby reducing the overall size and allowing the TM mode to pass through with minimal loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If a conventional polarizer structure is used to pass the TM mode and eliminate the TE mode, then the polarization filtering function is achieved, but the footprint area is large and consumes significant layout area on the photonics chip

Engineering Contradiction:

Improvepolarizer footprintVSAvoidpolarization filtering efficiency

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The patent introduces a vertical dimension by stacking multiple waveguide cores (first waveguide core, second waveguide core, and third waveguide core) at different heights. This three-dimensional arrangement allows the polarizer to achieve effective TE mode elimination and TM mode transmission within a compact lateral footprint, resolving the contradiction between small area and filtering efficiency.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Solution Approach 2:

The patent embeds multiple functional elements within each other: the second waveguide core is positioned within the tapered section of the first waveguide core, and the third waveguide core is positioned within the tapered section of the second waveguide core. This nested configuration maximizes the use of space and achieves effective polarization filtering in a compact structure.

Inventive Principle:

Principle #7Nested doll (Nesting)

2Area of moving object

If the polarizer footprint is reduced to increase layout area, then more components can be integrated, but the efficiency of lateral coupling and absorption of the TE mode may be compromised

Engineering Contradiction:

Improvepolarizer footprintVSAvoidlateral coupling efficiency

Core Design Contradiction:

Area of moving objectVSProductivity

Solution Approach 1:

The patent employs tapered sections in the waveguide cores where the width gradually changes along the propagation direction. This parameter change enables adiabatic mode transformation, allowing efficient lateral coupling between waveguide cores and effective TE mode absorption while maintaining a compact footprint. The tapered geometry ensures that mode conversion occurs without significant reflection or loss.

Inventive Principle:

Principle #35Parameter changes

3Area of moving object

If a compact polarizer structure is designed, then layout area is reduced, but the ability to maintain negligible loss of the TM mode may be affected

Engineering Contradiction:

Improvepolarizer footprintVSAvoidTM mode loss

Core Design Contradiction:

Area of moving objectVSLoss of energy

Solution Approach 1:

The patent divides the polarizer into multiple functional segments along the light propagation direction: input waveguide section, tapered coupling sections, intermediate waveguide sections, and output waveguide section. Each segment performs a specific function in the polarization filtering process, allowing the TM mode to pass through with minimal loss while the TE mode is progressively eliminated, all within a compact footprint.

Inventive Principle:

Principle #1Segmentation

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 the polarizer's footprint, increasing available layout area on the photonics chip, while maintaining efficient polarization filtering with negligible loss of the TM mode, allowing for more compact integration of other components.

Implementation Method 1

enhancing the efficiency of lateral coupling and absorption of the TE mode

Methodology Applied

Scientific EffectLateral coupling: Waveguide (optics)

Implementation Method 2

absorption of the TE mode

Methodology Applied

Scientific EffectAbsorption: Absorption (EM radiation)

Implementation Method 3

polarizer is configured to receive an optical signal containing multiple modes (e.g., transverse electric (TE) mode and transverse magnetic (TM) mode) and to allow only one of these modes to propagate while the other of the modes is eliminated or dropped

Methodology Applied

Scientific EffectPolarization filtering: Polarisation

Data Source

PatentUS11105978B2Polarizers including stacked elements

Publication Date: 2021.08.31 GLOBALFOUNDRIES US INC

AI summary

Structures for a polarizer and methods of fabricating a structure for a polarizer. A first waveguide core has a first tapered section, a second tapered section, and a section positioned along a longitudinal axis between the first tapered section and the second tapered section. The first tapered section and the second tapered section each narrow in a direction along the longitudinal axis toward the section. A second waveguide core has a first terminating end, a second terminating end, and a section that is arranged between the first and second terminating ends. The section of the second waveguide core is positioned either over or below the section of the first waveguide core.