Photonic-Crystal Surface Laser Hole Geometry for Dislocation Suppression

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Solution Overview

Problem

Dislocation in the semiconductor layer of photonic-crystal surface emitting lasers (PCSEL) occurs due to differences in refractive indices, leading to deteriorated characteristics.

Innovation Solution

The PCSEL design includes a photonic crystal layer with holes that are shorter in the <110> direction than in the <1-10> direction, facilitating faster growth of the semiconductor layer in the <110> direction, thereby quickly closing the holes and reducing dislocation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If holes are periodically disposed in the photonic crystal layer with equal lengths in all directions, then the photonic crystal structure provides uniform diffraction characteristics, but dislocation occurs in the semiconductor layer due to refractive index differences

Engineering Contradiction:

Improvecrystallinity of semiconductor layerVSAvoiddislocation in semiconductor layer

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent applies asymmetry by making the holes have different lengths in different crystallographic directions (shorter in <110> direction, longer in <1-10> direction). This asymmetric hole configuration creates preferential growth paths for the semiconductor layer, allowing faster hole closure in the <110> direction where dislocation is more problematic, thereby reducing overall dislocation in the semiconductor layer.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent applies local quality by creating direction-dependent hole characteristics within the photonic crystal structure. The holes are engineered to have specific length variations along different crystallographic directions, providing locally optimized properties that promote selective epitaxial growth and reduce dislocation in critical regions of the semiconductor layer.

Inventive Principle:

Principle #3Local quality

2Reliability

If the semiconductor layer grows slowly to close the holes, then the holes remain open longer providing optical functionality, but dislocation increases and crystallinity deteriorates

Engineering Contradiction:

Improvecrystallinity of semiconductor layerVSAvoidtime for hole closure

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The asymmetric hole design creates direction-dependent closure rates. The shorter hole dimension in the <110> direction enables faster closure in that specific direction, achieving rapid dislocation suppression without requiring complete closure of all hole dimensions, thus balancing speed and quality.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent changes the geometric parameters of the holes (lengths along different crystallographic directions) to optimize the epitaxial growth process. By adjusting hole dimensions anisotropically, the structure promotes faster material deposition in directions where rapid hole closure is beneficial for reducing dislocation.

Inventive Principle:

Principle #35Parameter changes

3Power

If holes with equal lengths in all directions are used, then the photonic crystal provides isotropic optical properties, but threshold current increases and output decreases

Engineering Contradiction:

Improveoutput of PCSELVSAvoidthreshold current

Core Design Contradiction:

PowerVSUse of energy by moving object

Solution Approach 1:

The asymmetric hole configuration modifies the optical mode distribution and confinement characteristics. The direction-dependent hole lengths create anisotropic diffraction that optimizes the lasing mode, reducing threshold current and enhancing output power by better matching the optical field distribution to the gain medium.

Inventive Principle:

Principle #4Asymmetry

Solution Approach 2:

The patent optimizes optical performance by changing the geometric parameters of the holes anisotropically. The specific length ratios and orientations of holes along different crystallographic directions are tuned to achieve optimal optical confinement and reduced losses, thereby lowering threshold current and increasing output power.

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 suppresses dislocation, improves crystallinity, reduces threshold current, enhances output, and increases long-term reliability of the PCSEL.

Implementation Method 1

By diffracting light in a plane of the photonic-crystal, light oscillates at a wavelength based on the period and is emitted in the normal direction of the plane

Methodology Applied

Scientific EffectDiffraction: Diffraction

Data Source

PatentUS20260018862A1Photonic-crystal surface emitting laser and method of manufacturing the same

Publication Date: 2026.01.15 SUMITOMO ELECTRIC INDUSTRIES LTD

AI summary

A photonic-crystal surface emitting laser includes an active layer, a photonic crystal layer, and a first semiconductor layer, wherein the photonic crystal layer includes a base material and a plurality of holes periodically disposed in the base material, the plurality of holes extends from one plane of the photonic crystal layer to an opposite plane of the photonic crystal layer, the first semiconductor layer is provided on the one plane of the photonic crystal layer, and a length of each of the plurality of holes in a <110>direction of the photonic crystal layer is smaller than a length of each of the plurality of holes in a <1-10>direction of the photonic crystal layer.