Surface-Emitting Laser Array Electrode Design for Corrosion Resistance

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Solution Overview

Problem

Surface-emitting laser arrays face challenges in balancing radiation performance and corrosion resistance, particularly when using aluminum gallium arsenide (Al x Ga (1-x) As with 0.95<x≤1, where increased radiation performance leads to enhanced corrosion susceptibility.

Innovation Solution

The surface-emitting laser array incorporates a mesa structure with a first and second reflection mirror, an active layer, and an electrode surrounding the emission region, where the electrode covers the region between adjacent light emitting parts and has a thickness greater than or equal to the height of the mesas, utilizing aluminum gallium arsenide (Al x Ga (1-x) As with 0.95<x≤1, and an upper electrode thickness of ≥2 µm to enhance both radiation performance and corrosion resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If aluminum gallium arsenide (Al x Ga (1-x) As with 0.95<x≤1) is used in the reflection mirror to improve radiation performance, then the radiation performance is enhanced, but corrosion resistance deteriorates due to increased susceptibility to water intrusion

Engineering Contradiction:
Improveradiation performanceVSAvoidcorrosion resistance
Core Design Contradiction:
Illumination intensityVSReliability

Solution Approach 1:

A thick electrode (≥2 µm) is introduced as an intermediary protective layer between the aluminum gallium arsenide reflection mirror and the external environment. This electrode layer acts as a barrier that prevents water intrusion and corrosion while allowing the high-Al content semiconductor layer to maintain its superior radiation performance for laser emission.

Inventive Principle:
Principle #24Intermediary (Mediator)

2Reliability

If the electrode thickness is increased to improve corrosion resistance, then protection against water intrusion is enhanced, but device complexity increases

Engineering Contradiction:
Improvecorrosion resistanceVSAvoidelectrode structure complexity
Core Design Contradiction:
ReliabilityVSDevice complexity

Solution Approach 1:

The thick electrode serves multiple functions simultaneously: it provides corrosion resistance by preventing water intrusion, acts as a protective barrier for the underlying semiconductor layers, and maintains electrical connectivity. By combining multiple functions into a single component, the design avoids adding separate protective layers, thus reducing overall device complexity while achieving reliable corrosion protection.

Inventive Principle:
Principle #6Universality (Multi-functionality)

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 effectively achieves both high radiation performance and corrosion resistance by ensuring the electrode covers the inter-mesa region, preventing water intrusion and enhancing heat dissipation, thus prolonging the lifespan of the laser device and maintaining stable high-output laser emission.

Implementation Method 1

heat is conducted in a lateral direction

Methodology Applied
Scientific EffectHeat conduction: Conduction (thermal)

Implementation Method 2

a selective oxidation layer in the upper reflecting mirror having a current blocking structure made of an oxidized region and an unoxidized region

Methodology Applied
Scientific EffectSelective oxidation: Oxidation

Data Source

PatentEP3271978B1Surface-emitting laser array, laser apparatus, ignition device and internal combustion engine
Publication Date: 2022.11.30 RICOH CO LTD
  • EP3271978B1 patent drawingFigure 1
  • EP3271978B1 patent drawingFigure 2
  • EP3271978B1 patent drawingFigure 3

AI summary

A surface-emitting laser array includes a plurality of light emitting parts. Each light emitting part includes a reflection mirror including aluminum gallium arsenide (AlxGa(1-x)As) where x is greater than 0.95 but less than or equal to 1; an active layer; and an electrode surrounding an emission region, from which laser light is emitted, the electrode covering a region between adjacent light emitting parts in the plurality of light emitting parts.