Semiconductor Optical Waveguide Coupling With Thermal Cladding

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Solution Overview

Problem

Current laser structures on heat dissipation substrates face challenges in optically coupling their output efficiently to Si optical waveguides embedded in SiO2/Si substrates, limiting their application in Si photonics due to poor heat dissipation and high refractive index mismatch.

Innovation Solution

A semiconductor optical device design featuring a first cladding layer with higher thermal conductivity than Si, a core with a direct transition semiconductor, and a second cladding layer with a refractive index lower than the core, where the core's cross-sectional shape in the optical coupling region facilitates substrate radiation modes for efficient optical coupling.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If a laser structure is formed on a SiO2/Si substrate with a membrane configuration to achieve high optical confinement, then optical confinement factor is improved, but thermal conductivity is reduced leading to poor heat dissipation

Engineering Contradiction:

Improveoptical confinement factorVSAvoidheat dissipation

Core Design Contradiction:

Illumination intensityVSTemperature

Solution Approach 1:

The device is divided into functionally independent parts: a SiO2/Si substrate for optical confinement and a separate heat dissipation substrate (SiC or diamond) for thermal management. The active layer is positioned at the interface between these two substrates, allowing simultaneous optimization of optical and thermal performance without compromise.

Inventive Principle:

Principle #1Segmentation

2Temperature

If a laser is formed on a heat dissipation substrate with high thermal conductivity and low refractive index, then heat dissipation is improved, but optical coupling to Si optical waveguide becomes difficult

Engineering Contradiction:

Improveheat dissipationVSAvoidoptical coupling efficiency

Core Design Contradiction:

TemperatureVSEase of manufacture

Solution Approach 1:

An optical coupling layer with intermediate refractive index is introduced between the heat dissipation substrate and the Si optical waveguide. This intermediary layer acts as a refractive index bridge, enabling efficient optical coupling while preserving the high heat dissipation capability of the substrate.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Illumination intensity

If the active layer is positioned close to the Si substrate to utilize high refractive index for optical confinement, then optical confinement is improved, but heat dissipation is reduced due to SiO2's low thermal conductivity

Engineering Contradiction:

Improveoptical confinementVSAvoidtemperature rise

Core Design Contradiction:

Illumination intensityVSTemperature

Solution Approach 1:

Inventive Principle:

Principle #1Segmentation

4Strength

If a bonding interface with insulating material layer is used to join InP and SiO2/Si substrates, then substrate bonding is achieved, but thermal conductivity at the bonding interface is reduced

Engineering Contradiction:

Improvesubstrate bondingVSAvoidthermal conductivity at interface

Core Design Contradiction:

StrengthVSTemperature

Solution Approach 1:

The bonding interface is engineered with controlled thickness and material composition of the insulating layer. By optimizing the thickness parameter and using materials with relatively higher thermal conductivity, the interface achieves both mechanical bonding strength and improved thermal transport capability.

Inventive Principle:

Principle #35Parameter changes

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 enables easier and more efficient optical coupling between the laser and the Si optical waveguide, enhancing heat dissipation and allowing for high-speed, high-temperature operation with improved modulation bandwidth.

Implementation Method 1

a first cladding layer formed on a Si substrate and including a material having thermal conductivity higher than thermal conductivity of a direct transition type semiconductor

Methodology Applied

Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

a core formed on the first cladding layer and including a direct transition type semiconductor

Methodology Applied

Scientific EffectLight emission from direct transition semiconductor: Electroluminescence

Implementation Method 3

a refractive index of the first cladding layer is higher than a refractive index of the second cladding layer and lower than a refractive index of the core

Methodology Applied

Scientific EffectTotal internal reflection: Total Internal Reflection

Data Source

PatentUS20240291233A1Semiconductor Optical Device

Publication Date: 2024.08.29 NIPPON TELEGRAPH & TELEPHONE CORP

AI summary

A semiconductor optical device includes: a first cladding layer formed on a Si substrate; a core formed on the first cladding layer; and a second cladding layer formed on the first cladding layer to cover the core. A lower cladding layer including SiO2 or the like is formed on (a front surface of) the Si substrate, and the first cladding layer is formed on the lower cladding layer. The first cladding layer includes a material having thermal conductivity higher than thermal conductivity of a direct transition type semiconductor. A refractive index of the first cladding layer is higher than that of the second cladding layer and lower than that of the core. In an optical coupling region of an optical waveguide by the core, a cross-sectional shape of the core is in a state in which a substrate radiation mode appears.