Semiconductor Laser Engineering, Reliability and Diagnostics : A Practical Approach to High Power and Single Mode Devices

Dr. Peter W. Epperlein is Technology Consultant with his own semiconductor technology consulting business Pwe-PhotonicsElectronics-IssueResolution in the UK. He looks back at a thirty years career in cutting edge photonics and electronics industries with focus on emerging technologies, both in global and start-up companies, including IBM, Hewlett-Packard, Agilent Technologies, Philips/NXP, Essient Photonics and IBM/JDSU Laser Enterprise. He holds Pre-Dipl. (B.Sc.), Dipl. Phys. (M.Sc.) and Dr. rer. nat. (Ph.D.) degrees in physics, magna cum laude, from the University of Stuttgart, Germany.

Dr. Epperlein is an internationally recognized expert in compound semiconductor and diode laser technologies. He has accomplished R&D in many device areas such as semiconductor lasers, LEDs, optical modulators, quantum well devices, resonant tunneling devices, FETs, and superconducting tunnel junctions and integrated circuits. His pioneering work on sophisticated diagnostic research has led to many world’s first reports and has been adopted by other researchers in academia and industry. He authored more than seventy peer-reviewed journal papers, published more than ten invention disclosures in the IBM Technical Disclosure Bulletin, has served as reviewer of numerous proposals for publication in technical journals, and has won five IBM Research Division Awards. His key achievements include the design and fabrication of high-power, highly reliable, single mode diode lasers.

Dedication

Preface

About the Author

PART I: DIODE LASER ENGINEERING
Overview

1. Basic Diode Laser Engineering Principles
Introduction

1.1. Brief Recapitulation

1.1.1. Key Features of a Diode Laser

1.1.2. Homo-Junction Diode Laser

1.1.3. Double-Heterostructure Diode Laser

1.1.4. Quantum Well Diode Laser

1.1.5. Common Compounds for Semiconductor Lasers

1.2. Optical Output Power – Diverse Aspects

1.2.1. Approaches to High Power Diode Lasers

1.2.2. High Optical Power Considerations

1.2.3. Power Limitations

1.2.4. High Power versus Reliability Trade-Offs

1.2.5. Typical and Record-High CW Optical Output Powers

1.3. Selected Relevant Basic Diode Laser Characteristics

1.3.1. Threshold Gain

1.3.2. Material Gain Spectra

1.3.3. Optical Confinement

1.3.4. Threshold Current

1.3.5. Transverse Vertical and Transverse Lateral Modes

1.3.6. Fabry-Perot Longitudinal Modes

1.3.7. Operating Characteristics

1.3.8. Mirror Reflectivity Modifications

1.4. Laser Fabrication Technology

1.4.1. Laser Wafer Growth

1.4.2. Laser Wafer Processing

1.4.3. Laser Packaging

References

2. Design Considerations for High Power Single Spatial Mode Operation

Introduction

2.1. Basic High Power Design Approaches

2.1.1. Key Aspects

2.1.2. Output Power Scaling

2.1.3. Transverse Vertical Waveguides

2.1.4. Narrow Stripe Weakly Index Guided Transverse Lateral Waveguides

2.1.5. Thermal Management

2.1.6. Catastrophic Optical Damage Elimination
 
2.2. Single Spatial Mode and Kink Control

2.2.1. Key Aspects

2.3.1. Introduction

2.3.2. Selected Calculated Parameter Dependencies

2.3.3. Selected Experimental Parameter Dependencies

2.4.1. Introduction

2.4.2. Broad Area Lasers

2.4.3. Unstable Resonator Lasers

2.4.4. Tapered Amplifier Lasers

2.4.5. Linear Laser Array Structures

References

Part II: DIODE LASER RELIABILITY

Overview

3. Basic Diode Laser Degradation Modes 

Introduction

3.1. Degradation and Stability Criteria of Critical Diode Laser Characteristics

3.1.1. Optical Power, Threshold, Efficiency and Transverse Modes

3.1.2. Lasing Wavelength and Longitudinal Modes

3.2. Classification of Degradation Modes
 
3.2.1. Classification of Degradation Phenomena by Location
 
3.2.2. Basic Degradation Mechanisms

3.3. Key Laser Robustness Factors 

References

4. Optical Strength Engineering

Introduction

4.1. Mirror Facet Properties – Physical Origins of Failure

4.2. Mirror Facet Passivation and Protection

4.2.1. Scope and Effects

4.2.2. Facet Passivation Techniques

4.2.3. Facet Protection Techniques

4.3. Non-Absorbing Mirror Technologies

4.3.1. Concept

4.3.2. Window Grown on Facet

4.3.3. Quantum Well Intermixing Processes

4.3.4. Bent Waveguide

4.4. Further Optical Strength Enhancement Approaches

4.4.1. Current Blocking Mirrors and Material Optimization

4.4.2. Heat Spreader Layer, Device Mounting and Number of Quantum Wells

4.4.3. Mode Spot Widening Techniques

References

5. Basic Reliability Engineering Concepts

Introduction

5.1. Descriptive Reliability Statistics

5.1.1. Probability Density Function

5.1.2. Cumulative Distribution Function

5.1.3. Reliability Function

5.1.4. Instantaneous Failure Rate or Hazard Rate

5.1.5. Cumulative Hazard Function

5.1.6. Average Failure Rate

5.1.7. Failure Rate Units

5.1.8. Bathtub Failure Rate Curve

5.2. Failure Distribution Functions – Statistics Models for Non-Repairable Populations

5.2.1. Introduction

5.2.2. Lognormal Distribution

5.2.3. Weibull Distribution

5.2.4. Exponential Distribution

5.3. Reliability Data Plotting

5.3.1. Life Test Data Plotting

5.4. Further Reliability Concepts

5.4.1. Data Types

5.4.2. Confidence Limits
 
5.4.3. Mean Time to Failure Calculations

5.4.4. Reliability Estimations

5.5. Accelerated Reliability Testing – Physics-Statistics Models

5.5.1. Acceleration Relationships

5.5.2. Remarks on Acceleration Models

5.6. System Reliability Calculations

5.6.1. Introduction

5.6.2. Independent Elements Connected in Series

5.6.3. Parallel System of Independent Components

References

6. Diode Laser Reliability Engineering Program

Introduction

6.1. Reliability Test Plan

6.1.1. Main Purpose, Motivation and Goals

6.1.2. Up-Front Requirements and Activities

6.1.3. Relevant Parameters for Long Term Stability and Reliability

6.1.4. Test Preparations and Operation

6.1.5. Overview Reliability Program Building Blocks

6.1.6. Development Tests

6.1.7. Manufacturing Tests

6.2. Reliability Growth Program

6.3. Reliability Benefits and Costs
 
6.3.1. Types of Benefit

6.3.2. Reliability – Cost Trade Offs

References

PART III: DIODE LASER DIAGNOSTICS

Overview

7. Novel Diagnostic Laser Data for Active Layer Material Integrity, Impurity Trapping Effects and Mirror Temperatures

Introduction

7.1. Optical Integrity of Laser Wafer Substrates

7.1.1. Motivation

7.1.2. Experimental Details

7.1.3. Discussion of Wafer Photoluminescence Maps

7.2. Integrity of Laser Active Layers

7.2.1. Motivation

7.2.2. Experimental Details

7.2.3. Discussion of Quantum Well PL Spectra

7.3. Deep-Level Defects at Interfaces of Active Regions

7.3.1. Motivation

7.3.2. Experimental Details

7.3.3. Discussion of Deep-Level Transient Spectroscopy Results

7.4. Micro-Raman Spectroscopy for Diode Laser Diagnostics

7.4.1. Motivation

7.4.2. Basics of Raman Inelastic Light Scattering

7.4.3. Experimental Details

7.4.4. Raman on Standard Diode Laser Facets

7.4.5. Raman for Facet Temperature Measurements

7.4.6. Various Dependences of Diode Laser Mirror Temperatures

References

8. Novel Diagnostic Laser Data for Mirror Facet Disorder Effects, Mechanical Stress Effects and Facet Coating Instability

Introduction

8.1. Diode Laser Mirror Facet Studies by Raman

8.1.1. Motivation

8.1.2. Raman Microprobe Spectra

8.1.3. Possible Origins of the 193 cm-1 Mode in (Al)GaAs

8.1.4. Facet Disorder – Facet Temperature – Catastrophic Optical Mirror Damage Robustness Correlations

8.2. Local Mechanical Strain in Ridge-Waveguide Diode Lasers

8.2.1. Motivation

8.2.2. Measurements – Raman Shifts and Stress Profiles

8.2.3. Detection of “Weak Spots”

8.2.4. Stress Model Experiments

8.3. Diode Laser Mirror Facet Coating Structural Instability

8.3.1. Motivation

8.3.2. Experimental Details

8.3.3. Silicon Recrystallization by Internal Power Exposure

8.3.4. Silicon Recrystallization by External Power Exposure – Control Experiments

References

9. Novel Diagnostic Data for Diverse Laser Temperature Effects, Dynamic Laser Degradation Effects and Mirror Temperature Maps

Introduction

9.1. Thermoreflectance Microscopy for Diode Laser Diagnostics

9.1.1. Motivation

9.1.2. Concept and Signal Interpretation

9.1.3. Reflectance – Temperature Change
Relationship 

9.1.4. Experimental Details
 
9.1.5. Potential Perturbation Effects on Reflectance

9.2. Thermoreflectance versus Optical Spectroscopies

9.2.1. General

9.2.2. Comparison

9.3. Lowest Detectable Temperature Rise

9.4. Diode Laser Mirror Temperatures by Micro-Thermoreflectance

9.4.1. Motivation

9.4.2. Dependence on Number of Active Quantum Wells
 
9.4.3. Dependence on Heat Spreader

9.4.4. Dependence on Mirror Treatment and Coating
 
9.4.5. Bent-Waveguide Non-Absorbing Mirror
 
9.5. Diode Laser Mirror Studies by Micro-Thermoreflectance

9.5.1. Motivation

9.5.2. Real-Time Temperature-Monitored Laser Degradation

9.5.3. Local Optical Probe

9.5.3.1. Threshold and heating distribution within near-field spot

9.6. Diode Laser Cavity Temperatures by Micro-Electroluminescence

9.6.1. Motivation

9.6.2. Experimental Details – Sample and Setup

9.6.3. Temperature Profiles along Laser Cavity

9.7. Diode Laser Facet Temperature – Two-Dimensional Mapping

9.7.1. Motivation

9.7.2. Experimental Concept

9.7.3. First Temperature Maps Ever

9.7.4. Independent Temperature Line Scans Perpendicular Active Layer

9.7.5. Temperature Modelling

References

Index