Optical Waveguide Adiabatic Coupling via Intermediate Layer

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Solution Overview

Problem

Adiabatic coupling between waveguides with different refractive index contrasts faces limitations in design due to abrupt changes in refractive index, leading to coupling losses and design trade-offs, particularly in the thickness of higher-contrast waveguides, which affect overall optical coupling performance.

Innovation Solution

An improved design for the intermediate waveguide with a three-layer adiabatic transition, featuring sections with varying heights to facilitate efficient adiabatic mode transformation between low-contrast and high-contrast waveguides, allowing independent choice of waveguide heights for each coupling section, thereby reducing overall system loss.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If adiabatic coupling is used between waveguides with different refractive index contrasts, then broadband coupling is achieved, but coupling losses occur due to abrupt changes in refractive index

Engineering Contradiction:

Improvebroadband couplingVSAvoidcoupling losses

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The patent introduces an intermediate waveguide layer with refractive index n2 between the low-contrast waveguide (n1) and high-contrast waveguide (n3). This intermediate layer acts as a mediator to gradually transition the optical mode between the two different refractive index contrasts, reducing abrupt changes and minimizing coupling losses while maintaining broadband operation.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent varies the thickness parameter of the intermediate waveguide layer along the propagation direction. By changing the thickness from h1 at the first interface to h2 at the second interface, the refractive index contrast is gradually adjusted, enabling smooth adiabatic mode transformation and reducing coupling losses.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the thickness of higher-contrast waveguides is increased to reduce coupling losses, then transmission performance improves, but design flexibility is reduced

Engineering Contradiction:

Improvetransmission lossVSAvoiddesign flexibility

Core Design Contradiction:

Loss of energyVSAdaptability or versatility

Solution Approach 1:

The patent segments the waveguide structure into multiple layers with different thicknesses: a first waveguide layer with thickness h1 and a second waveguide layer with thickness h2. This segmentation allows independent optimization of each layer's thickness for its specific coupling function, maintaining design flexibility while reducing transmission losses.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent applies different thickness values to different sections of the waveguide structure. The first waveguide layer has thickness h1 optimized for coupling to the low-contrast waveguide, while the second waveguide layer has thickness h2 optimized for coupling to the high-contrast waveguide. This local quality variation enables simultaneous optimization of coupling efficiency and design flexibility.

Inventive Principle:

Principle #3Local quality

3Productivity

If waveguide thickness is optimized for one coupling section, then coupling efficiency improves, but overall system performance is limited by the worst section

Engineering Contradiction:

Improvecoupling efficiencyVSAvoidoverall system performance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent divides the coupling structure into multiple independent sections, each with its own waveguide layer and thickness optimization. The first coupling section uses thickness h1 optimized for its specific refractive index contrast, while the second coupling section uses thickness h2 optimized for its contrast. This segmentation allows each section to be optimized independently without compromising the other, improving overall system reliability.

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

This design reduces overall transmission loss to near zero dB between waveguides, making it less sensitive to fabrication tolerances and enabling efficient optical routing with reduced leakage and bending losses.

Implementation Method 1

Adiabatic coupling provides a potentially lossless optical mode transformation between waveguides with different refractive index contrast and geometry

Methodology Applied

Scientific EffectAdiabatic coupling:

Implementation Method 2

An optical mode transformation occurs as a result of a change in refractive index and/or geometry in one waveguide or between two waveguides

Methodology Applied

Scientific EffectRefractive index contrast: Refraction

Data Source

PatentUS10393967B2Optical waveguide, corresponding coupling arrangement and method providing transverse propagation path

Publication Date: 2019.08.27 STMICROELECTRONICS SRL

AI summary

An optical waveguide includes opposed end sections for optical radiation to propagate in a longitudinal direction therebetween and an intermediate section extending between the end sections. The intermediate section includes first and second portions superposed in a superposition direction. One of the opposite end sections has a first height in the superposition direction corresponding to the sum of the heights of the superposed portions of the intermediate section. The other of the opposite end sections has a second height in the superposition direction corresponding to the height of the first of the superposed portions of the intermediate section.