Table Of ContentLaser ypocsortcepS
of Solids
Edited by W. M. Yen and R M. Selzer
With Contributions by
A.H. Francis T.Holstein D.L.Huber
G.F.Imbusch R.Kopelman S.K.Lyo R.Orbach
P.M.Selzer M.J.Weber W.M. neY
Second Edition
htiW 711 serugiF
Springer-Verlag Berlin Heidelberg New York
London Paris Tokyo
Professor William M. Yen
Department of Physics, University of Wisconsin
Madison, IW 53706, USA
Peter M. Selzer, M.D., Ph.D.
Division of Diagnostic Radiology, Stanford University
Stanford, CA 94305, USA
ISBN 3-540-16709-9 2. Auflage Springer-Verlag Berlin Heidelberg New York
ISBN 0-387-16709-9 2nd edition Springer-Verlag New York Berlin Heidelberg
ISBN 3-540-10638-3 .1 Auflage Springer-Verlag Berlin Heidelberg New York
ISBN 0-387-I0638-3 1st edition Springer-Verlag New York Berlin Heidelberg
Library of Congress Cataloging-in-Publication Data. Laser spectroscopy of solids. (Topics in applied physics; .v )94
:yhpargoilbiB p. Includes index. .1 Solids - Optical properties. .2 Laser spectroscopy. I. Yen, W. M. (William M.)
II. ,rezieS .P M. (Peter M.) III. Francis, A. H. (Anthony H.) IV. .seireS 73L60.8.671CQ 1986 530.4'1 08811-68
This work is subject to copyright. llA rights are reserved, whether the whole or part of the material is concerned,
yllacificeps those of translation, reprinting, reuse of illustrations, broadcasting, reproduction by photocopying
machine or similar means, and storage in data banks. Under § 45 of the German Copyright Law, where copies are
made for other than private use, a eef is payable to "Verwertungsgesellsehaft Wort", Munich.
© Springer-Verlag Berlin Heidelberg 1891 and 6891
Printed in Germany
The use of registered names, trademarks, etc. in this publication does not imply, even in the absence of a cificeps
statement, that such names are exempt from the relevant protective laws and regulations and therefore free for
general use.
Offset printing and bookbinding: Brfihlsche ,ierekcurdst,~tisrevinU Giessen
012345-0513/3512
We wish to dedicate this reissue to the memory of
Theodore D. Holstein
)5891-5191(
A mentor, a colleague, and a friend
Preface to the Second Edition
My colleagues and I have been gratefully pleased by the reception accorded to this
volume by the scientific community. This has resulted in the decision to reissue
Laser Spectroscopy of Solids in a second edition. As we had predicted, the activity
in this research area has enjoyed an explosive growth since 1981, thus some of the
contents of the monograph have inevitably become dated. Fortunately, a great deal
of the material has maintained its currency, specially those sections dealing with
theoretical and methodological aspects. We feel consequently that this volume re-
mains viable as an introduction and general reference to this area of spectroscopy.
As we have already noted, there has been an impressive amount of activity in
the area of laser spectroscopy as applied to the condensed phases. The commercial-
ization of many laser devices has been widespread and the general availability of
these sources has contributed greatly to the dissemination of the experimental tech-
niques advocated in this volume. At the same time, the needs of various advanced
technologies for better and more efficient optical materials have continued to
stimulate the study of optical properties of solids in both theoretical and experi-
mental senses. eW cannot see anything on the horizon which will diminish this activ-
ity and can safely predict continuing advances in spectroscopic methodologies, in
fundamental improvements in optical materials and in applied optical technologies.
Since the volume appeared, all areas delved in the reviews have experienced
considerable advances. Many experimental laser devices have since then been com-
mercialized and hence have become more or less commonplace laboratory tools.
Even as developments have begun which allow entry into the femtosecond temporal
domain, picosecond pulsed lasers have become readily available and thus studies of
dynamical processes in excited states have naturally expanded into this time regime.
Simultaneously, by using nonlinear processes and by exploiting the optical proper-
ties of defects, the tunability of stimulated devices has been extended further into
the vuv and to the near Jr. Because of these developments, many more levels and
materials have become amenable to laser-spectroscopic investigation.
In the course of the past five years, we have also witnessed the maturation of
coherent spectroscopic techniques such as those described in this volume. These
techniques have made it possible to obtain spectra with unprecedented resolution
so that the intrinsic limits have been attained in many cases. A great dealofinfor-
marion on superhyperfine interactions affecting optically active electrons has been
obtained through these means, resolving a number of the questions which had been
raised in this volume.
viii Preface to the Second Edition
Dynamical effects have also been pursued vigorously in the interim between
the publication of the original volume and this revision. The theoretical develop-
ments reviewed in the monograph have by and large been placed on a very firm
experimental foundation. As a consequence, we now possess a much more detailed
understanding of both the microscopic and macroscopic aspects of processes which
produce relaxation, quenching and transfer out of excited optical states in ordered
and disordered solids.
The advances in the understanding have also received considerable assistance
from new theoretical concepts such as those involved in fractals. Additionally, the
exponential growth in general computing capabilities has made it feasible to
engage in large scale modeling of structures and of dynamics in ways which had not
been thought practical even a short five years ago. All of these developments have
given us new insights and new opportunities for exploitation.
The present volume has been fairly criticized for having been restricted to the
area of insulators. As it was noted in the preface to the first edition, this restriction
was placed principally on account of space restrictions. It is our intention to amend
this omission by the publication of a sequel volume to Laser Spectroscopy of Solids
in the near future. The sequel will also include an extensive update of the various
advances in the field which we have alluded to above.
We have been permanently saddened by the untimely passing of one of our
colleague s in this endeavor. Professor Theodore Holstein was a valued colleague to
all of us as well as a mentor and a friend. We wish then to dedicate this reissue vol-
ume to his memory as a small expression of our joint appreciation.
Finally, we are pleased that the reissue is appearing in a lower-price paperback
form. This economy will allow a larger student audience to avail themselves of this
review of ours. We are thankful to Dr. H. K. V. Lotsch and to Springer for their
continued encouragement and support which has served to make this effort possible
and a positive experience.
Madison, January 1986 .qI .M Yen
Preface to the First Edition
In this volume we have attempted to present a concise survey of the spectroscopic
properties of insulators as derived from the application of tunable laser spectro-
scopic techniques. As has been the case in gaseous atomic spectroscopy, the of
use
tunable lasers has allowed the extension and the refinement of optical measure-
ments in the condensed phases to unprecedented resolutions in the frequency and
temporal domains. In turn, this firmer base of empirical findings has led to a more
sophisticated theoretical understanding of the spectroscopy of optically excited
states with major modifications being apparent in the area of their dynamic be-
havior. Yet the revivalistic nature of these advances implies that additional advan-
ces are to be expected as the techniques and developments outlined in this volume
are put to widespread use. Regardless, it is our hope and that of our distinguished
colleagues in this venture that the reviews presented here will be useful to neo-
phytes and veterans to this field alike - to the former as a laissez-passer into
solid-state spectroscopy, to the latter as a useful synopsis and reference of recent
developments.
eW have also attempted to expose the reader to the concept that optically
active materials, be they organic or inorganic, as universality would require, be-
have in a like manner and, though terminology may vary in detail, the outline
and general features of all insulators remain constant.
The book is organized as follows: Chapter 1 surveys in general terms the
field of spectroscopy of insulators and establishes the basic features the other
chapters refer to. Chapters 2 and 3, respectively, deal with the microscopic and
macroscopic aspects of the theory of dynamics of optically excited states with
emphasis on ion.ion interactions which are responsible for optical energy transfer
and diffusion in condensed phases. Chapter 4 details experimental techniques
which are used in laser spectroscopy in solids. Finally, the last three chapters pre-
sent surveys of the empirical status of these studies in ionic or crystalline, glassine
or amorphous, and organic solids, respectively.
The other areas in the study of optical properties of condensed matter where
lasers have played crucial roles and where considerable advances have been made,
such as semiconductors and the various types of light scattering experiments, are
not the principal focus of this volume and, hence, will not be reviewed here.
Finally, we wish to acknowledge the many people who have encouraged us
and collaborated with us in various phases of compilation. We specially wish to
thank Dr. H. K. V. Lotsch and the editorial staff of Springer for their help and
X ecaferP ot eht First noitidE
patient guidance, and Dr. E. Strauss and Dr. S.T. Lai for their assistance during
the preparation of this volume. A special note of thanks si due .sM Karen .M Wick
who did the majority of the type composition of this volume; her ability was
only surpassed by her patience and understanding. One of us (W.M.Y.) has bene-
fitted from support from the John Simon Guggenheim Memorial Foundation
during the 1979-80 academic year. eW also acknowledge support from the -aN
tional Science Foundation and the Army Research Office for the preparation of
the manuscripts.
January 1981 .W 3f. Yen. P. M. Selzer
Contents
1. Optical Spectroscopy of Electronic Centers in Solids
By G. F. Imbusch and R. Kopelman (With 20 Figures) .............. 1
1.1 Overview ......................................... 1
1.2 Interaction of Electronic Center with Optical Radiation .......... 1
1.3 Eigenstates for the Electronic Center in a Solid ............... 3
1.4 Energy Levels and Radiative Transitions in Ionic Centers ......... 5
1.4.1 Rare Earth Ions in a Static Environment ................ 5
1.4.2 Transition Metal Ions in a Static Environment ............ 9
1.4.3 Interaction of the Optically Active Ion with Lattice Modes .... 12
1.5 Energy Levels and Radiative Transitions in Isolated
Molecular Centers ................................... 15
1.6 Broadening of the No-Phonon Line ....................... 18
1.7 Nonradiative Relaxation .............................. 22
1.8 Increased Concentration and Excitation Transfer .............. 25
1.8.1 Increased Concentration - Ionic Solids ................. 25
1.8.2 Increased Concentration - Molecular Solids ............. 28
1.9 Fully Concentrated Materials ........................... 30
1.9.1 Fully Concentrated Material - Ionic Solids .............. 31
1.9.2 Fully Concentrated Materials - Molecular Solids .......... 35
References .......................................... 36
2. Excitation Transfer in Disordered Systems
By T. Holstein, S. K. Lyo, and R. Orbach (With 7 Figures) ........... 39
2.1 Excitation Localization ............................... 39
2.2 Phonon-Assisted Excitation Transfer ...................... 41
2.3 Nonradiative Excitation Transfer ......................... 42
2.3.1 Formulation of the Problem ........................ 43
2.3.20ne-Phonon-Assisted Process ....................... 45
2.3.3 Two-Phonon-Assisted Processes ...................... 49
2.4 Phonon-Assisted Radiative Transfer ....................... 63
2.4.10ne-Phonon-Assisted Process ....................... 64
2.4.2 Two-Phonon-Assisted Processes .................... .. 72
2.5 Phonon Trapping ................................... 76
2.5.1 Relationship to Radiative Trapping ................... 76
2.5.2 Frequency Shifting Mechanism by Energy Transfer ......... 77
XII Contents
2.6 Conclusions ....................................... 79
References ......................................... 81
3. Dynamics of Incoherent Transfer. By D. L. Huber (With 12 Figures) ...... 83
3.1 Rate Equations .................................... 83
3.2 Fluorescence Line Narrowing ........................... 85
3.2.1 General Theory and Exact Results .................... 85
3.2.2 Approximations ................................ 87
3.2.3 Further Approximations .................. ........ 90
3.2.4 Development of the Background Fluorescence ............ 91
3.2.5 Experimental Studies ............................ 94
3.3 Fluorescence in the Presence of Traps, Exact Results ............ 96
3.3.1 Early Models .................................. 97
3.3.2 Average T-Matrix Approximation .................... 99
3.3.3 Experimental Studies ............................ 103
3.4 Summary and Outlook ............................... 107
Appendix 3.A ........................................ 108
Appendix 3.B ........................................ 108
References .......................................... 110
4. General Techniques and Experimental Methods in Laser Spectroscopy
of Solids. By P. M. Seizer (With 7 Figures) ...................... 113
4.1 Fluorescence Line Narrowing in Solids ..................... 115
4.1.1 Phenomenological Model .......................... 115
4.1.2 Sources of Residual Broadening ...................... 117
4.1.3 Spectral Dynamics .............................. 120
4.1.4 Experimental Details ............................. 122
4.2 Saturation Spectroscopy in Solids ........................ 126
4.2.1 Hole Burning ................................... 127
4.2.2 Polarization Spectroscopy ......................... 130
4.3 Coherent Transient Spectroscopy ........................ 131
4.4 Light Scattering .................................... 135
4.5 Photoacoustic (or Optoacoustic) Spectroscopy ................ 135
4.6 Degenerate Four-Wave Mixing (Transient Grating Spectroscopy) .... 136
4.7 Conclusion ....................................... 137
References .......................................... 137
5. High Resolution Laser Spectroscopy of Ions in Crystals
By W. M. Yen and P. M. Selzer (With 25 Figures) ................. 141
5.1 Homogeneous Linewidth Studies ......................... 141
5.1.1 Ruby A1203: Cr 3+ ......... .................... 142
Contents XIII
5.1.2 Trivalent Praseodymium in Lanthanum Fluoride LaF3 :Pra+ . 149
5.1.3 Actinides and Other Centers ........................ 152
5.2 Static Spectral Features ............................... 154
5.2.1 Hyperfine and Other Structures ...................... 154
5.2.2 Site and Impurity Selectivity ....................... 158
5.2.3 Assisted Transitions ............................. 160
5.3 Single-Ion and Interion Dynamics ........................ 162
5.3.1 Single-Ion Dynamics ............................. 162
5.3.2 Energy Transfer ................................ 165
5.4 Concentrated Materials and Excitonic Effects ................ 175
5.4.1 PrF3 and PrCla ................................ 175
5.4.2 Tb(OH)a ..................................... 177
5.4.3 Magnetic Excitons .............................. 178
5.4A Other Concentrated Materials ....................... 182
5.5 Conclusion ....................................... 183
References .......................................... 184
Additional References with Titles ........................... 188
6. Laser Excited Fluorescence Spectroscopy in Glass
By M. J. Weber (With 22 Figures) ........................... 189
6.1 Background ....................................... 189
6.2 Glass Properties .................................... 191
6.2.1 Structure ..................................... 191
6.2.2 Activator Ions and Molecules ....................... 192
6.3 Experimental Techniques .............................. 196
6.3.1 Fluorescence Line Narrowing ....................... 196
6.3.2 Temporal Dependence ............................ 198
6.3.3 Polarization ................................... 199
6.3.4 Excitation-Fluorescence Schemes .................... 200
6.3.5 Accidential Coincidence ........................... 201
6.4 Experimental Apparatus .............................. 202
6.5 Experimental Results ................................ 203
6.5.1 Energy Levels ................................. 203
6.5.2 Transition Probabilities . . . ........................ 214
6.5.3 Homogeneous Linewidth .......................... 219
6.5.4 Energy Transfer ................................ 223
6.6 Applications of Fluorescence Line Narrowing ................ 227
6.6.1 Glass Structure ................................. 227
6.6.2 Structural Changes .............................. 231
6.6.3 Laser Glass ................................... 233
6.7 Concluding Remarks ................................. .v 234
References .......................................... 236
Additional References ................................... 239
