Handbook of the Eurolaser Academy: Volume 1

437 Pages·1998·14.602 MB·English

by  D. Schuöcker (auth.), D. Schuöcker (eds.)

Handbook of the Eurolaser Academy
Handbook of the Eurolaser Academy
Volume 1
Edited by D. Schuocker
Director of the Eurolaser Academy
Vienna
Austria
uni
SPRINGER-SCIENCE+BUSINESS MEDIA, BV. I
First edition 1998
© 1998 Springer Science+Business Media Dordrecht
Originally published by Chapman & Hali in 1998
Softoover reprint ofthe hardcover Ist edition 1998
ISBN 978-1-4613-7416-9 ISBN 978-1-4615-5295-6 (eBook)
DOI 10.1007/978-1-4615-5295-6
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A catalogue record for Ihis book is available from the British Library
:9
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v
Contents
List of contributors
VIII
Preface
IX
Acknowledgements
X
Introduction
XI
1 Basic Laser Mechanisms
D. Schuocker
1.1 Basic wave phenomena 1
1.2 Electromagnetic waves and light 15
1.3 Electrons, atoms and molecules 20
1.4 Interaction between light and matter 27
1.5 Basic laser mechanisms 33
1.6 Active media 39
1.7 References 50
2 Optics, Resonators and Beams
D. Schuocker
2.1 The Kirchhoff-Fresnel integral 51
2.2 Fourier transformation by focusing 52
2.3 Focusing a gaussian distribution 54
2.4 Gaussian beams 56
2.5 Higher order transverse modes 59
2.6 Divergence of higher order transverse modes 62
2.7 Focusing arbitrary beam modes 63
2.8 Stable resonators 64
2.9 Unstable resonators 72
2.10 Characterisation of beam quality 78
2.11 References 84
vi Contents
3 Carbon Dioxide Lasers
D. Schuocker
3.1 Introduction 85
3.2 Excitation, emission and relaxation mechanisms 86
3.3 Parametric behaviour of the CO2 laser 90
3.4 Energising and cooling the plasma 94
3.5 Main types of electrode system and plasma
shapes, output power 100
3.6 Optical resonators and beam quality 108
3.7 Summary 115
3.8 References 117
4 Solid State Lasers
H Weber
4.1 Introduction 119
4.2 Main characteristics of high power Nd lasers 131
4.3 Resonators for high power and beam quality 165
4.4 Realisation of high power systems 190
4.5 Beam delivery by fibres 212
4.6 References 220
5 Excimer Lasers
C. Fotakis. C. Kalpouzos and T. Papazoglou
5.1 Introduction 227
5.2 The physics of the active medium 228
5.3 Preionization and pumping considerations 232
5.4 Cooling systems and corrosion problems 237
5.5 Beam manipulation systems 240
5.6 Pulse shaping 253
5.7 Current status and future developments 262
5.8 Applications 263
5.9 References 264
6 Semiconductor Lasers
E. Wintner
6.1 Introduction 267
6.2 Materials and epitaxial growth techniques 269
6.3 Electronic and optical properties 280
6.4 Diode laser design 305
6.5 Conclusions and outlook 319
6.6 References 321
Contents vii
7 Safety
JM Green
7.1 Introduction 325
7.2 Biological hazards 327
7.3 Hazard classification and MPES 337
7.4 Standards and legislative requirements 343
7.5 Control measures 354
7.6 Radiation risk assessment 366
8 Beam Manipulation
R.C. Craler
8.1 Setting the scene 379
8.2 Small scale applications 385
8.3 Medium and large scale applications 399
8.4 Sensors 416
8.5 Acknowledgements 421
Index 423
viii
List of contributors
Volume Editor
Professor D. Schuocker
Department of High Power Beam Technology
Vienna University of Technology
Austria
Principal authors in alphabetical order
Dr. RC. Crafer
Abington Consultants, Cambridge
England
Professor C. Fotakis
Laser and Applications Division
Foundation for Research and Technology Hellas (FORTH)
Greece
Dr. J.M. Green
Pro Laser, Abingdon
England
Professor D. SchuOcker
Department of High Power Beam Technology
Vienna University of Technology
Austria
Professor H. Weber
Optisches Institut
Technische UniversiUit Berlin
Germany
Professor E. Wintner
Institut flir Allgemeine Elektrotechnik
Technische Universitat Wien
Austria
ix
Preface
The European Community regards training as a priority area and has
therefore developed a series of programmes in the field of vocational
training.
This book is the result of a pilot project selected under two of these
Community Action Programmes. It was initially selected under the
COMETT programme, concerned with the development of continuing
vocational training in the European Community. Moreover, it was one of
the few selected projects to receive further funding under a second
selection in the context of the LEONARDO DA VINCI Action Programme
for the implementation of a European Community Vocational Training
policy.
It is with great pleasure that I present the outcome of this project which
embodies one of the fundamental objectives of the LEONARDO DA
VINCI Programme -training for new technologies in SMEs, which make a
significant contribution to economic development in Europe.
K DRAXLER
Director
Directorate General XXII
European Commission
x
Acknowledgements
The Volume Editor gratefully acknowledges funding by the LEONARDO
DA VINCI Programme of the Commission of the European Community
and by the Austrian Federal Ministry of Science and Transport whose
financial support has made the EuroLaser Academy a reality and has led
directly to the generation ofthis handbook.
He is also indebted to Director Dr. Klaus Draxler, Head of the
LEONARDO DA VINCI Programme, DG XXII of the Commission of the
European Community, moreover to Director General Raul Kneucker,
Minister's Advisor Helmut Schacher and Mrs. Friederike Pranckl-Kloepfer
from the Austrian Federal Ministry of Science and Transport.
Grateful thanks are due to authors and their organisations for their
contributions, and for their efforts in updating their manuscripts from
lecture form to chapter form.
A number of people behind the scenes have been instrumental in reading
and correcting the manuscripts, suggesting improvements and compiling
the index. Specific thanks are due to Ms. Tanja Altreiter, Gerhard Lied),
Andreas Penz, Kurt SchrOder and Wendelin Weingartner of the Department
of Laser Technology, Vienna University of Technology.
Alexander Kaplan of the Department of Laser Technology and
Ms. Gabriele Schmid of ARGELAS, the Austrian Laser Association, have
provided constant organisational support throughout this project, while
Roger Crafer from Abington Consultants has provided substantial support
in editing the book.
Finally the Volume Editor extends grateful thanks and
acknowledgements to all those other co-workers who are not mentioned
here.
xi
Introduction
High power lasers can be used to perform various manufacturing processes
with significant advantages such as flexibility in terms of material,
geometry and processing tasks. Furthermore, laser processing is fast, yields
high processing quality that often permits post process machining to be
eliminated, and is environmentally friendly. High power laser sources used
for conventional processes as cutting, welding and surface treatment have
reached a high degree of industrial maturity. New processes that extend the
range of applications of high power lasers in material processing, such as
3-D processing, rapid prototyping, forming and micromachining are rapidly
developing. For these reasons, laser processing is replacing more and more
mechanical or thermal production processes, and leading in general to
higher manufacturing competitiveness.
Although laser processing has important advantages, it is nevertheless a
difficult task compared to conventional processing:
• The energy source, a high power laser, is a complex system with
powerful high frequency electronics, ultra high temperature plasmas,
fast gas flows, ultra precise optics and sophisticated sensor and control
systems.
• The production tool, the laser beam itself, is an invisible
electromagnetic light wave with very specific properties, and entirely
different from natural light. For example power densities up to
100 MW Icm2 determine the quality and performance of the production
process, in turn depending strongly on the appropriate operation of the
laser source.
• The results of the manufacturing process depend not only on the quality
of the laser beam, but also on the properties of the workpiece material
and on the performance of the manipulation system that moves the
workpiece along the desired contour.
The production process itself results from the combined action of various
phenomena, e.g. absorption of light by the workpiece, heating of the
workpiece, subsequent melting and evaporation, plasma formation, action
of external gas flows and fast flow and resolidification of the molten