Laser Systems: Part 3

283 Pages·2011·13.755 MB·English

by  M. Walther (auth.), H. Weber, P. Loosen, R. Poprawe (eds.)

New
Series
Numerical Data
and Functional Relationships
in Science and Technology
GROUP VIII VOLUME 1
Advanced Materials Laser Physics
and Technologies
and Applications
SUBVOLUME B
Laser Systems
Part 3
1
123
Landolt-Börnstein / New Series
Landolt-Börnstein
Numerical Data and Functional Relationships
in Science and Technology

New Series
Editor in Chief: W. Martienssen†

Units and Fundamental Constants in Physics and Chemistry

Elementary Particles, Nuclei and Atoms (Group I)

(Formerly: Nuclear and Particle Physics)

Molecules and Radicals (Group II)
(Formerly: Atomic and Molecular Physics)

Condensed Matter (Group III)
(Formerly: Solid State Physics)

Physical Chemistry (Group IV)
(Formerly: Macroscopic Properties of Matter)

Geophysics (Group V)

Astronomy and Astrophysics (Group VI)

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Advanced Materials and Technologies (Group VIII)

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their contents.
Landolt-Börnstein
Numerical Data and Functional Relationships in Science and Technology
New Series / Editor in Chief: W. Martienssen†

Group VIII: Advanced Materials and Technologies
Volume 1

Laser Physics
and Applications

Subvolume B: Laser Systems

Part 3

Editors: H. Weber, P. Loosen, R. Poprawe

Authors:
O. Ambacher, K. Boucke, M. Chi, P. Crump, B. Eppich, K. Häusler,
H.-D. Hoffmann, R. Kleindienst, M. Kneissl, P.M. Petersen, J. Raß,
W. Schmid, S. Sinzinger, U. Strauß, B. Sumpf, P. Unger, M. Walther,
Q. Yang, U. Zeimer, A.E. Zhukov
ISSN 1619-4802 (Advanced Materials and Technologies)

ISBN 978-3-642-14176-8 Springer Berlin Heidelberg New York

Library of Congress Cataloging in Publication Data:
Landolt-Börnstein: Numerical Data and Functional Relationships in Science and Technology, New Series.
Editor in Chief: W. Martienssen†
Group VIII, Volume 1: Laser Physics and Applications. Subvolume B: Laser Systems. Part 3.
Edited by H. Weber, P. Loosen, R. Poprawe.
Springer-Verlag, Berlin, Heidelberg, New York 2011.
Includes bibliographies.
1. Physics - Tables. 2. Chemistry - Tables. 3. Engineering - Tables.
I. Börnstein, Richard (1852-1913). II. Landolt, Hans (1831-1910).
QC 61.23 502'.12 62-53136

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Editors

Weber, Horst
Technische Universität Berlin, Institut für Optik und Atomare Physik, Berlin, Germany

Loosen, Peter
Fraunhofer-Institut für Lasertechnik (ILT), Aachen, Germany

Poprawe, Reinhart
Fraunhofer-Institut für Lasertechnik (ILT), Aachen, Germany

Authors

Ambacher, Oliver
Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Freiburg, Germany

Boucke, Konstantin
Oclaro Inc., Oro Valley, Arizona, USA

Chi, Mingjun
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Roskilde,
Denmark

Crump, Paul
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Eppich, Bernd
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Häusler, Karl
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Hoffmann, Hans-Dieter
Fraunhofer-Institut für Lasertechnik (ILT), Aachen, Germany

Kleindienst, Roman
Technische Universität Ilmenau, Institut für Mikro- und Nanotechnologien (IMN – MacroNano®),
Fachgebiet Technische Optik, Ilmenau, Germany

Kneissl, Michael
Technische Universität Berlin, Institut für Festkörperphysik, Berlin, Germany
and
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Petersen, Paul Michael
DTU Fotonik, Department of Photonics Engineering, Technical University of Denmark, Roskilde,
Denmark
VI Authors
Raß, Jens
Technische Universität Berlin, Institut für Festkörperphysik, Berlin, Germany

Schmid, Wolfgang
OSRAM Opto Semiconductors GmbH, Regensburg, Germany

Sinzinger, Stefan
Technische Universität Ilmenau, Institut für Mikro- und Nanotechnologien (IMN – MacroNano®),
Fachgebiet Technische Optik, Ilmenau, Germany

Strauß, Uwe
OSRAM Opto Semiconductors GmbH, Regensburg, Germany

Sumpf, Bernd
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Unger, Peter
Universität Ulm, Institut für Optoelektronik, Ulm, Germany

Walther, Martin
Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Freiburg, Germany

Yang, Quankui
Fraunhofer-Institut für Angewandte Festkörperphysik (IAF), Freiburg, Germany

Zeimer, Ute
Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Berlin, Germany

Zhukov, Alexey E.
St. Petersburg Academic University – Nanotechnology Research and Education Center of the Russian
Academy of Sciences, St. Petersburg, Russia

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Preface
The three volumes VIII/1A, B, C document the state of the art of “Laser Physics and Applications”.
Scientific trends and related technology aspects are considered by compiling results and conclusions from
phenomenology, observation and experiments. Reliable data, physical fundamentals and detailed
references are presented.
In recent decades the laser source matured to an universal tool common to scientific research as well
as to industrial use. Today the technical goal is the generation of optical power towards shorter
wavelengths, shorter pulses, higher efficiency and higher pulse and average power for applications in
science and industry. Tailoring the optical energy in wavelength, space and time is a requirement for the
investigation of laser-induced processes, i.e. excitation, non-linear amplification, storage of optical
energy, etc. According to the actual trends in laser research and development, Vol. VIII/1 is split into
three parts: Vol. VIII/1A with its two subvolumes 1A1 and 1A2 covers laser fundamentals, Vol. VIII/1B
with its three subvolumes 1B1, 1B2 and 1B3 deals with laser systems and Vol. VIII/1C gives an overview
on laser applications.
Due to the increase of efficiency, power and beam quality diode lasers have become a major interest.
In the low-power range they are used in information technology and metrology, in the high-power range as
pumping modules for solid-state lasers and increasingly in material processing. Therefore it was necessary
to dedicate a complete volume to the recent advances in diode lasers, in addition to the fundamentals of
diode lasers in Vol. VIII/1B2.
In this Vol. VIII/1B3 the following topics are treated in detail:
Part 8: Crystal growth, wafer technology and epitaxy
Crystal growth technology is of high importance, because the relevant parameters as wavelength, life time,
efficiency depend on the mastery and control of these quantities. The first section of this part covers bulk
crystal growth technologies for the fabrication of III-V compound semiconductor substrates. Different
technologies for bulk crystalline growth of ingots, with emphasis on GaAs, InP, and GaSb, are given.
Wafering of substrates, polishing, and surface preparation techniques follow in subsequent sections.
In the second section the different epitaxial technologies are described. Molecular beam epitaxy and
related growth technologies as well as metal-organic chemical vapor phase epitaxy are the methods of
choice for epitaxial growth of laser structures in different material systems with high crystalline
perfection, precise control of thickness, composition, and doping, abrupt interfaces, and good
reproducibility and homogeneity on large compound semiconductor substrates.
Part 9: Edge-emitting laser diodes
The first section deals with GaN-systems, emitting in the blue and green spectral range between 400 and
500 nm with output powers of more than 5 W. A short review on the many applications in this spectral
range is given. The materials properties of the group-III nitrides are reviewed. Of high interest are the
quantum-well systems emitting in the 370-550 nm range. Special features are waveguides, cladding layers
and polarization properties. Finally the performance characteristics of these laser diodes are discussed.
VIII Preface
The second part is dedicated to the red-emitting diodes. The InAlGaP-diodes with emission
wavelength in the range of 635-670 nm are compared with the AlGaAs-systems. The optical properties of
InAlGaP are presented. Laser chip structures and facet stability are the final topics.
Diode lasers in the near infra-red spectral range are reviewed in section three. Diode lasers fabricated
on GaAs substrates cover the spectral range from 600 nm to 1600 nm, bipolar diode lasers on InP
substrates emit in the spectral range from 1200 nm to 2300 nm. The key-words in these two sections are
material properties, substrates doping, wave-guiding cladding, and structure design. The laser optical
parameters and physical properties are compiled in several tables and figures.
Quantum cascade lasers (QCLs) are the topic of section four. This laser, a unipolar device where the
lasing transitions occur between two quantized conduction band states in a series of coupled quantum
wells, differs in many fundamental ways from the semiconductor diode lasers. The transition energy is
determined by the size quantization effect but not by the semiconductor forbidden bandgap, which allows
a large wavelength range (from 3 μm to over 100 μm), using the same material system.
Starting with a brief summary of the principles, the design and fabrication procedure are summarized.
The QCLs are treated in two groups: the mid-to-far infra-red systems (3–30 μm) and the terahertz (30–300
μm) lasers. A review on actual and future applications is given.
Part 10: Vertical-cavity surface-emitting lasers
In vertical-cavity surface-emitting semiconductor lasers the resonator length is of the order of a few
wavelengths and therefore the number of oscillating longitudinal modes is rather low. To compensate the
low gain high reflecting mirrors are required, normally distributed Bragg reflectors are used. The basic
concepts, properties, and applications are summarized. An outline of wavelengths 0.3-1.6 μm and material
systems is given.
Part 11: Quantum dot lasers
A structure, where energy barriers exist in one direction of propagation is now known as a quantum dot
(QD). As compared to other types of the active region, quantum dots are much more favorable for laser
applications. In this ultimate case the only allowed energy states correspond to discrete quantum levels.
Formation of quantum dots and their basic structural properties is reported in section one.
Optical properties, inhomogeneous line broadening, control of emission wavelength, and optical gain
are the main topics of the following sections. Quantum dot lasers emitting in the 1.2–1.3 μm range,
beyond 1.3 μm, broad gain and low threshold systems are discussed.
Finally, the relevant properties for technical applications, the temperature stability, and the reliability
are reviewed.
Part 12: Laser diode characterization and testing
The first part summarizes the standard characterization methods, which have to be adapted to the special
features of diode lasers. The relevant parameters of diode lasers differ considerably from those of normal
lasers. The emitting area is very small and the divergence beyond the paraxial approach. Careful and
reliable measurement of these properties are indispensable for research and development of diode lasers,
for quality control in manufacturing, and as input for device data sheets.
Reliability and life time are the key words of the second part.
Of major interest for the industrial application of diode lasers is the life time, its definition, and the
special procedures to measure it. Life time depends mainly on the defects and a detailed analysis is given
in the third section.
Preface IX
Part 13: Micro-optics and beam shaping
The diode laser output field is highly astigmatic and has to be adapted to the special application by micro-
optics, refractive/reflecting optics, and other shaping systems. In the first and second part the fundamental
aspects of microoptics including diffractive optics as well as the technological background of the most
important technologies for the fabrication are discussed.
Section three deals with refractive and reflective microoptics. System integration is a key aspect of this
technology and briefly presented in section four. Optical beam shaping by transformers and splitting by
gratings are the topics of the last part, including the theoretical background and the Fourier transform
algorithm.
Part 14: High-power diode lasers
The fundamental properties of edge-emitting laser bars require specific package design characteristics. It
refers to a laser diode bar attached to a heat sink and provided with electrical contacts to its p-side and n-
side, in a way that the laser bar can be integrated into a fiber-coupled module or solid-state laser system
and operate as required. Depending on the application area, the mode of operation, and the average power
the package can be designed in different ways and comprise different components. Electrical and
mechanical requirements are summarized.
The packaging processes for p-side and n-side bonding are discussed and the different solder
compositions are compiled in detailed tables. Wire bonding, contact foils, heat sinks, and heat sink
assemblies are the key words of the following sections. Conductively cooled and convection-cooled heat
sinks are presented.
In the second part the various methods of combining many single emitters to high-power systems are
discussed. Coherent and incoherent coupling, spatial, polarization and wavelength multiplexing are the
key words. Beam shaping as well as fiber coupling are two further topics. Finally a summary of diode
laser applications in materials processing is given.
Part 15: External cavities and optically pumped disk lasers
The first part deals with diode lasers in external cavities. The progress of external feedback techniques to
improve the spatial and temporal coherence of edge-emitting high-power single-emitter semiconductor
diode lasers is reviewed. For the broad-area diode laser the external cavity feedback systems are divided
into three categories: narrow-linewidth systems, high spatial beam quality systems, and systems with both
high spatial and temporal coherence. Different external cavity techniques to achieve these three kinds are
discussed. Tapered diode lasers and typical experimental results are presented.
Edge-emitting high-power diode lasers can produce large amounts of optical power, and they are
attractive because of their compactness, long lifetimes, simplicity of operation, low cost, and high
efficiency.
Different techniques in order to improve the spatial and/or temporal coherence are discussed: injection
locking to an external single-mode master, and various external cavity feedback methods including
monolithically integrated master-oscillator power amplifiers.
The second part gives an introduction to the physics, design, and applications of optically pumped
semiconductor disk lasers with emphasis on high-power and high-efficiency operation. The properties of
these lasers are compared to edge-emitting semiconductor laser diodes, vertical-cavity surface-emitting
lasers (VCSELs), and solid-state thin-disk lasers. The epitaxially grown layer sequence of the
semiconductor laser disk, consisting of a multilayer Bragg mirror and a resonant periodic gain region, is
discussed. Two different concepts of optical pumping, namely barrier and quantum well pumping, are
introduced.
Due to their external cavity, semiconductor disk lasers are ideal devices for intracavity second
harmonic generation to obtain visible laser emission using linear and folded cavity setups. Edge-emitting