Optical Waveguide Layout for Low-Loss Non-Reciprocal Isolation

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Solution Overview

Problem

Existing optical isolators using magneto-optical materials like Ce:YIG in waveguides suffer from increased loss due to mismatched propagation characteristics between waveguide parts with and without a non-reciprocal member, leading to inefficiencies.

Innovation Solution

The optical integrated circuit design includes a waveguide with distinct first and second parts, where the second part has a reduced height and/or altered dimensions to align energy distributions, and incorporates a non-reciprocal member alongside the waveguide to minimize mode center deviations, thereby reducing loss for both TM-mode and TE-mode electromagnetic waves.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a non-reciprocal member is positioned alongside the waveguide, then non-reciprocal optical isolation is achieved, but propagation loss increases due to mismatched energy distribution between waveguide parts

Engineering Contradiction:

Improveoptical isolation performanceVSAvoidpropagation loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The waveguide is designed with different cross-sectional dimensions for its first and second parts. The first part has a first cross-sectional dimension while the second part has a second cross-sectional dimension that is smaller than the first. This local variation in geometry allows the energy distribution to be optimized in each region, reducing the mismatch at the interface where the non-reciprocal member is positioned, thereby reducing propagation loss while maintaining isolation performance.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the physical parameters of the waveguide by adjusting the cross-sectional dimensions of different parts. By making the second cross-sectional dimension smaller than the first, the mode field distribution is modified to better match the presence of the non-reciprocal member, reducing reflection and scattering losses while preserving the non-reciprocal optical isolation function.

Inventive Principle:

Principle #35Parameter changes

2Loss of energy

If the waveguide cross-sectional dimension is reduced in the second part, then energy distribution alignment improves, but waveguide manufacturing complexity increases

Engineering Contradiction:

Improvepropagation lossVSAvoidwaveguide fabrication

Core Design Contradiction:

Loss of energyVSEase of manufacture

Solution Approach 1:

The waveguide is segmented into distinct first and second parts along its length, with each part having different cross-sectional dimensions. This segmentation allows independent optimization of each region's geometry to match the local optical requirements, particularly in the region where the non-reciprocal member is positioned, while using standard fabrication techniques for each segment.

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 design effectively reduces propagation loss by aligning energy distributions and minimizing mode center shifts, enhancing the efficiency of electromagnetic wave transmission.

Implementation Method 1

an electromagnetic wave propagating in the first part and an electromagnetic wave propagating in the second part couple with each other

Methodology Applied

Scientific EffectElectromagnetic wave propagation:

Implementation Method 2

The non-reciprocal member is positioned alongside the second part in an amplitude direction of an electric field component of the electromagnetic wave

Methodology Applied

Scientific EffectNon-reciprocal optical effect:

Data Source

PatentUS12493204B2Optical integrated circuit

Publication Date: 2025.12.09 KYOCERA CORP

AI summary

An optical integrated circuit includes: a waveguide including a first part and a second part and configured to couple an electromagnetic wave propagating in the first part and an electromagnetic wave propagating in the second part; and a non-reciprocal member positioned alongside the second part in an amplitude direction of an electric field component of the electromagnetic wave. In a range where the first part and the second part are coupled with each other, deviation between a center of an energy distribution of an electric field component of the electromagnetic wave propagating in the first part and a center of an energy distribution of an electric field component of the electromagnetic wave propagating in the second part falls within a prescribed range.