Broad-area laser bars for 1 kW-emission : demonstrating increased efficiency and narrowed far field / Matthias M. Karow.

Format:

Book

Author/Creator:

Karow, Matthias M., 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 ; v.70

Language:

English

Subjects (All):

Emission spectroscopy.

Physical Description:

1 online resource (143 pages)

Edition:

1st ed.

Place of Publication:

Göttingen : Cuvillier Verlag, [2022]

Summary:

Industrial laser systems for material processing applications rely on the availability of highly efficient, high-brightness diode lasers. GaAs-based broad-area laser bars play a vital role in such applications as pump sources for high-beam-quality solid-state lasers and, increasingly, as direct processing tools.This work studies 940 nm-laser bars emitting 1 kW optical power at room temperature, identifying those physical mechanisms that are currently limiting electrical-to-optical conversion efficiency as well as lateral beam quality. In the process, several diagnostic studies on bars with varied lateral-longitudinal design were carried out. The effects of technological measures for performance optimization were analyzed, yielding a new benchmark in efficiency and lateral divergence.The studies into altered resonator lengths of 4 and 6 mm as well as fill factors between 69 and 87 % successfully reduce both the voltage dropping across the device and power saturation at high currents, enabling 66 % efficiency at the operation point. Concrete measures how to reach efficiencies ?70 % are presented thereafter, showing that doubling the efficiency value of the first 1 kW-demonstration in 2007 - amounting to 35 % - is in near reach.Investigation of the beam quality bases on a herein proposed and realized concept, in which the far field is resolved for each individual bar emitter. In this way, it is possible to determine how far-field profiles vary along the bar width and how much these variations affect the overall bar far-field. Further, such effects specific to bar structures can be separated into non-thermal and thermal influences. The effect of mechanical chip deformation (bar smile) as well as neighboring-emitter interaction has been investigated for the first time in active kW-class devices, yielding a lateral divergence as low as 8.8° at the operation point.

Contents:

Intro

Abstract

1. Introduction

1.1. The global laser market

1.2. State of the art

1.3. Structure of this work

2. Theoretical Background

2.1. Concept and physics of broad-area laser bars

2.2. Definition and governing effects of beam quality in broad-area lasers

2.3. Strained diode-laser chips

2.4. Thermal aspects of diode-laser operation

3. Experimental Methods

3.1. Fabrication of broad-area laser bars

3.2. Characterization techniques

4. Diode-Laser Bars for Highly Efficient 1 kW-Emission

4.1. Vertical structure for high-efficiency operation

4.2. Thermal transient

4.3. Varied resonator length

4.4. Impact of the lateral design

4.5. Conclusions

5. Efficient 1 kW-Emitting Bars Exhibiting Narrow Far Field

5.1. Mechanical chip deformation (bar smile)

5.2. Emitter cross heating

5.3. Bar edge emitters

5.4. Emitter sub-structure

5.5. Conclusions

6. Conclusions and Outlook

Appendices

A. Beam-Path Calculation Using the Matrix Formalism

B. Thermal Wavelength Dependence of Longitudinal Modes

Bibliography

Public ContributionsPublic Contributions

Acknowledgements

Biographical Sketch.

Notes:

Description based on print version record.

ISBN:

9783736966260

3736966261