Spot-Size Converter for Silicon Waveguide and Fiber Coupling

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Solution Overview

Problem

Existing spot-size converters for integrating optical components with different dimensions, such as silicon photonic waveguides and optical fibers, face limitations in effectively converting spot-sizes due to poor confining capabilities and mode mismatch, leading to energy loss and inefficient light transfer.

Innovation Solution

A spot-size converter design featuring a transition region with a lower waveguiding structure and an upper waveguiding structure formed by high-index elements arranged in multiple vertically spaced rows and columns, allowing for a low-index region where the mode of the first waveguide progressively transforms into the mode of the second waveguide, enabling efficient light propagation between dissimilar waveguides.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple tapered waveguiding structure is used for spot-size conversion, then the device complexity is reduced, but the conversion capability is insufficient and energy loss increases

Engineering Contradiction:

Improvewaveguiding structure complexityVSAvoidenergy loss

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The waveguiding structure is divided into multiple functional regions: a first waveguiding structure coupled to the first waveguide, a second waveguiding structure coupled to the second waveguide, and a transition region between them. This segmentation allows each region to be optimized for specific functions, improving overall conversion efficiency while managing complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The transition region acts as an intermediary between the first and second waveguiding structures, enabling gradual mode transformation. This intermediate zone facilitates smooth spot-size conversion by progressively changing the waveguiding properties, reducing abrupt transitions and associated energy losses.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the waveguiding structure is made large enough to confine light substantially all along the structure, then light confinement is improved, but the spot-size conversion capability is limited

Engineering Contradiction:

Improvelight confinementVSAvoidspot-size conversion capability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

Different regions of the waveguiding structure have different confining properties. The first and second waveguiding structures provide strong confinement for their respective waveguides, while the transition region provides gradual, localized confinement change to enable spot-size conversion. This local differentiation achieves both reliable confinement and conversion capability.

Inventive Principle:

Principle #3Local quality

3Adaptability or versatility

If an inverted-taper waveguiding structure is used to increase spot-size, then the spot-size conversion range is extended, but the confining capability deteriorates and energy loss increases

Engineering Contradiction:

Improvespot-size conversion rangeVSAvoidenergy loss

Core Design Contradiction:

Adaptability or versatilityVSLoss of energy

Solution Approach 1:

The waveguiding structure dynamically adjusts its confining properties along the light propagation path. The transition region gradually changes the waveguiding dimensions, allowing the structure to adapt its confinement strength from the first waveguide to the second waveguide, enabling extended spot-size conversion while managing energy loss through controlled transitions.

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

This configuration enables efficient mode conversion and light propagation between waveguides with significantly different dimensions, reducing energy loss and improving coupling efficiency, particularly between submicron silicon waveguides and optical fibers with larger mode field diameters.

Implementation Method 1

a low-index region where the mode of the first waveguide progressively transforms into the mode of the second waveguide, thereby enabling light propagation via a mode of the combined system of the first and second parts of waveguiding structures

Methodology Applied

Scientific EffectOptical mode conversion: Waveguide (optics)

Data Source

PatentUS10371895B2Spot-size converter for optical mode conversion and coupling between two waveguides

Publication Date: 2019.08.06 CIENA CORP

AI summary

A spot-size converter having a waveguiding structure. The first part of the waveguiding structure receives light from or transmits light to a first waveguide in a first propagation mode. The first part of the waveguiding structure has a longitudinally varying effective refractive index that decreases away from the first waveguide. The second part of the waveguiding structure transmits light to or receives light from a second waveguide in a second propagation mode. The second part of the waveguiding structure has a number of high-index elements arranged in a single plane, extending along a longitudinal waveguiding axis and at least partially overlapping the first part of the waveguiding structure. The first propagation mode of the first waveguide progressively transforms into the second propagation mode of the second waveguide along the longitudinal waveguiding axis through an overlap region between the first part and the second part of the waveguiding structure.