Epitaxial Design Optimizations for Increased Efficiency in GaAs-Based High Power Diode Lasers / Thorben Kaul.

Format:

Book

Author/Creator:

Kaul, Thorben, author.

Series:

Innovationen mit Mikrowellen und Licht. Forschungsberichte aus dem Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik

Innovationen mit Mikrowellen und Licht. Forschungsberichte aus dem Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik ; Volume

Language:

English

Subjects (All):

Diodes.

Physical Description:

1 online resource (137 pages)

Edition:

First edition.

Place of Publication:

Göttingen : Cuvillier Verlag, [2021]

Summary:

This work presents progress in the root-cause analysis of power saturation mechanisms in continuous wave (CW) driven GaAs-based high-power broad area diode lasers operated at 935 nm. Target is to increase efficiency at high optical CW powers by epitaxial design.The novel extreme triple asymmetric (ETAS) design was developed and patented within this work to equip diode lasers that use an extremely thin p-waveguide with a high modal gain. An iterative variation of diode lasers employing ETAS designs was used to experimentally clarify the impact of modal gain on the temperature dependence of internal differential quantum efficiency (IDQE) and optical loss. High modal gain leads to increased free carrier absorption from the active region. However, less power saturation is observed, which must then be attributed to an improved temperature sensitivity of the IDQE. The effect of longitudinal spatial hole burning (LSHB) leads to above average non-linear carrier loss at the back facet of the device. At high CW currents the junction temperature rises. Therefore, not only the asymmetry of the carrier profile increases but also the average carrier density in order to compensate for the decreased material gain and increased threshold gain. This carrier non-pinning effect above threshold is found in this work to enhance the impact of LSHB already at low currents, leading to rapid degradation of IDQE with temperature. This finding puts LSHB into a new context for CW-driven devices as it emphasizes the importance of low carrier densities at threshold. The carrier density was effectively reduced by applying the novel ETAS design. This enabled diode lasers to be realized that show minimized degradation of IDQE with temperature and therefore improved performance in CW operation.

Contents:

Intro

Contents

List of Publications

Abstract

Kurzfassung

1 Introduction

1.1 Structure and method of this work

2 Fundamentals

2.1 Laser technology and market context

2.2 Fabrication technology

2.3 Mathematical framework of semiconductor lasers

2.4 Parameters for characterization of broad area diode lasers

2.5 Simulation tools

2.6 Device configurations and measurement setups

3 Literature Review, Prior State of the Art and Target Specifications

3.1 Power and efficiency limiting effects - an overview

3.2 Target specifications

3.3 Prior state of the art high power diode lasers and laser bars

4 Novel Epitaxial Layer-Stack Design for Increased Efficiency

4.1 General epitaxial design considerations

4.2 Prior state of the art epitaxial design concepts and their limits

4.3 ETAS: The novel extreme triple asymmetric design concept

5 Diagnosis and Analysis of Power Limiting Mechanisms

5.1 Devices designed and used for diagnosis

5.2 Quantifying thermal- and bias-driven contributions to rollover

5.3 Bias-driven power limitations

5.4 Thermal-driven power limitations

6 Performance of Diode Lasers Using Optimized VerticalDesigns

6.1 Impact of optical confinement on T0 and T1

6.2 Measurement results of diode laser bars

6.3 Short-term perspective for further improved performance

7 Conclusion and Outlook

7.1 The role of optical loss in thermal power saturation

7.2 The role of internal differential quantum efficiency in thermal power saturation

7.3 Performance of optimized devices using the novel ETAS design

7.4 Outlook

8 Acknowledgements

A Appendix

B List of Abbreviations

Bibliography.

Notes:

Description based on publisher supplied metadata and other sources.

Description based on print version record.

Includes bibliographical references.

ISBN:

9783736963962

3736963963

OCLC:

1246582541