Adiabatic Polarization Rotator-Splitter Using Silicon Nitride Rib Waveguide

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Solution Overview

Problem

Existing adiabatic polarization rotators and splitters face challenges in efficiently converting and separating light with different polarizations in silicon photonic integrated circuits, particularly in achieving high mode conversion efficiency and polarization extinction ratio.

Innovation Solution

The implementation of a polarization rotator splitter (PRS) system with a silicon nitride (SiN) rib waveguide and a silicon (Si) strip waveguide, featuring a ribbed structure with varying rib width and a tapered geometry, which adiabatically converts TM00 to TE01 polarization mode and spatially separates components, utilizing the vertical asymmetry of the waveguide structure to achieve efficient mode conversion and polarization rotation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional adiabatic polarization rotator is used, then polarization conversion is achieved, but mode conversion efficiency and polarization extinction ratio are insufficient

Engineering Contradiction:

Improvemode conversion efficiencyVSAvoidwaveguide structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent employs vertical asymmetry in the waveguide structure by introducing a rib feature that breaks the symmetry of the waveguide cross-section. This asymmetric geometry creates different effective indices for TE and TM modes, enabling adiabatic polarization rotation while achieving high conversion efficiency and extinction ratio without requiring overly complex multi-stage structures

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The rib width is varied locally along the propagation direction to create a gradient in the waveguide's effective index. This local modification of the waveguide geometry allows for controlled adiabatic evolution of the polarization state, achieving high mode conversion efficiency through gradual parameter changes rather than uniform structure modifications

Inventive Principle:

Principle #3Local quality

2Productivity

If the rib width is varied to improve mode conversion, then polarization rotation efficiency increases, but manufacturing precision requirements increase

Engineering Contradiction:

Improvepolarization conversion efficiencyVSAvoidrib width variation precision

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The rib width is designed to vary dynamically along the propagation direction, creating a gradient structure that enables adiabatic evolution. This dynamic geometric variation allows the waveguide to continuously transform the polarization state with high efficiency while using fabrication-compatible gradual transitions that reduce sensitivity to manufacturing tolerances

Inventive Principle:

Principle #15Dynamics

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 PRS system achieves high mode conversion efficiency and polarization extinction ratio, with minimal loss, enabling effective polarization conversion and separation of light components in silicon photonic integrated circuits, enhancing the performance of photonic systems.

Implementation Method 1

The PRS includes a silicon nitride (SiN) rib waveguide core... the rib width wrib varies along at least a portion of a length of the SiN rib waveguide core... which adiabatically converts TM00 to TE01 polarization mode

Methodology Applied

Scientific EffectAdiabatic mode conversion: Waveguide (optics)

Implementation Method 2

utilizing the vertical asymmetry of the waveguide structure to achieve efficient mode conversion and polarization rotation

Methodology Applied

Scientific EffectVertical asymmetry:

Implementation Method 3

spatially separates components, enabling effective polarization conversion and separation of light components

Methodology Applied

Scientific EffectPolarization separation:

Data Source

PatentUS11119275B2Adiabatic polarization rotator-splitter

Publication Date: 2021.09.14 II VI DELAWARE INC

AI summary

Various polarization rotator splitter (PRS) configurations are disclosed. In an example embodiment, a system includes a PRS that includes a silicon nitride (SiN) rib waveguide core that includes a rib and a ridge that extends vertically above the rib, the SiN rib waveguide core having a total height hSiN from a bottom of the rib to a top of the ridge, a rib height hrib from the bottom of the rib to a top of the rib, a rib width wrib, and a top width wSiN of the ridge. The rib width wrib varies along at least a portion of a length of the SiN rib waveguide core.