Waveguide Nonlinear-Optic Devices

329 Pages·2003·12.602 MB·English

by  Professor Toshiaki Suhara, Dr. Masatoshi Fujimura (auth.)

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11 Waveguide Nonlinear-Optic Devices
By T. Suhara and M. Fujimura
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T. Suhara M. Fujimura
Waveguide
Nonlinear-Optic
Devices
With 173 Figures
, Springer
Professor Toshiaki Suhara
Dr. Masatoshi Fujimura
Osaka University, Graduate School of Engineering, Department of Electronics
2-1 Yamada-Oka, Suita, Osaka 565-0781, Japan
Series Editors:
Professor Takeshi Kamiya Dr. Herbert Venghaus
Ministry of Education, Culture, Sports, Heinrich -Hertz-Institut
Science and Technology, fUr Nachrichtentechnik Berlin GmbH
National Institution for Academic Degrees, Einsteinufer 37
3-29-1 Otsuka, Bunkyo-ku, 10587 Berlin, Germany
Tokyo 112-0012, Japan
Professor Bo Monemar Professor Yoshihisa Yamamoto
Department of Physics Stanford University
and Measurement Technology Edward L. Ginzton Laboratory
Materials Science Division Stanford, CA 94305, USA
Linkoping University
58183 Linkoping, Sweden
ISSN 1437-0379
ISBN 978-3-642-05685-7
Library of Congress Cataloging-in-Publication Data
Suhara, Toshiaki, 1950-
Waveguide nonlinear-optic devices I T. Suhara, M. Fujimura. p. cm. - (Springer series in photonics, ISSN
1437-0379 ; v. 11) Includes bibliographical references and index.
ISBN 978-3-642-05685-7 ISBN 978-3-662-10872-7 (eBook)
DOI 10.1007/978-3-662-10872-7
1. Optoelectronic devices. 2. Optical waveguides. 3. Nonlinear optics. I. FujinlUra, M. (Masatoshi), 1965-II.
Title. III. Series.
TK8304.S842003
621.36'9-dc21 2003050522
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Preface
Nonlinear optic effects provide a variety of possibilities for realizing important
and unique photonics functions unfeasible with linear optics and electronics.
They have found a number of applications in many areas of science, and nonlinear
optic instruments using bulk crystals are widely used in laboratories. Use of a
waveguide structure to confine interacting optical waves enables implementation
of compact and efficient devices appropriate for wider and more practical applica
tions, including those for office and consumer use in the area of optical informa
tion processing. Such waveguide nonlinear-optic (NLO) devices have been a
subject of extensive research and development work during past three decades,
and remarkable progress has been obtained in the last decade.
The waveguide NLO device technology has reached considerable maturity, as
represented by the commercialization of a blue laser module using a waveguide
second-harmonic generation device developed for optical disc memory. A num
ber of waveguide NLO devices for optical communication have also been devel
oped. They include difference-frequency generation devices as wavelength con
verters for wavelength division multiplexing optical communication systems and
all-optical switching devices for ultrafast optical data processing. Thus, the
waveguide nonlinear-optic devices are now an important subarea of photonics.
Extensive research and development work is being continued, and it is expected
that further progress will be made toward improvement of the performances, im
plementation of novel functions, and finding new applications not only in the ex
isting areas but also in emerging research areas such as quantum information
processing.
There already exist a number of authoritative textbooks on nonlinear optics,
and waveguide and integrated optics, as given as the references in Chapters land
2, but they do not provide detailed information on waveguide NLO devices. Ac
tually, there also exist many monographs, review articles and conference pro
ceedings concerning waveguide NLO devices. A few books dealing with NLO
phenomena in optical fibers and their applications have been published rather re
cently. However, a comprehensive textbook on waveguide NLO devices has not
been available. The monographs and proceedings are narrow in scope and lack
continuity, and most of the review articles on the waveguide NLO devices are
evidently outdated, since the remarkable development of this subarea has been
accomplished rather recently.
This book was written in order to offer a comprehensive and systematic de
scription of waveguide NLO devices, encompassing basic concepts, theoretical
analysis and device design, fabrication techniques, specific device implementa-
VI Preface
tions, and their applications, including the most recent results. As readers of this
book, graduate students studying photonics and engineers who are going to be in
volved in research and development in this area are assumed. With a background
in electromagnetic theory, quantum theory and material sciences at the under
graduate level, they should be able to learn the material without much difficulty.
The book would also be a useful reference for professionals in their review of the
subarea.
This book consists of three parts. The first part provides a general introduc
tion and presents fundamental concepts and theoretical analysis. The second part
deals with techniques required for fabrication of waveguide NLO devices. The
third part presents specific waveguide NLO device implementations and their ap
plications. A general introduction is given in Chapter 1. Fundamental con
cepts, such as optical waveguides, optical nonlinearities, NLO susceptibilities,
NLO interactions and phase matching, are outlined in Chapter 2. In Chapter 3, a
theoretical analysis of various NLO interactions in waveguides required for deeper
understanding of device characteristics and device design is discussed in detail
based on the nonlinear coupled-mode theory. Chapter 4 deals with theoretical
discussions of NLO interactions in waveguide resonators. The quantum theory
ofNLO devices is considered in some detail in Chapter 5, since it is expected that
its importance will increase in future research and development work toward ac
complishment of ultimate performances and implementation of novel functions.
Chapters 6 and 7 describe two important elements of device fabrication, i.e., tech
niques for fabrication of waveguides in ferroelectric NLO crystals and those for
fabrication of quasi-phase matching (QPM) structures, respectively. In Chapter
8, waveguide second-harmonic generation (SHG) devices are discussed as a pro
totype of many waveguide NLO devices, including problems related to materials
and device implementation. Some applications, e.g., those in optical disc mem
ory pickup heads, are also presented. In Chapter 9, waveguide differ
ence-frequency generation (DFG) devices for wavelength conversion of optical
communication signals and for generation of long-wavelength radiation are dis
cussed. In Chapter 10, waveguide optical parametric amplifiers and oscillators
(OPA and OPO) are discussed. Chapter 11 is devoted to waveguide NLO de
vices for ultrafast optical signal processing including optical sampling and gate
switching. Although the emphasis is on devices using second-order nonlinearity,
some examples of devices based on third-order nonlinearity are also presented.
The Appendix provides data for some important NLO materials. Efforts have
been made to provide many mathematical expressions, graphic, and numerical
data useful for device design by the readers.
The entire contents were organized by Suhara. The Preface, Chapter I, Chap
ter 2, Sections 3.1, 3.2, 3.3, 3.4, 4.2, Chapter 5, Chapter 7, Chapter 8, Chapter 9,
and Chapter 11 were written by Suhara. Sections 3.5, 4.1, Chapter 6, and Chap
ter 10 were written by Fujimura, and were revised for improvement under the su
pervision of Suhara. The manuscripts were carefully checked for mutual consis
tency and comprehensiveness. Some of the data, figures, and photographs are
based on research activities in the authors' laboratory at Osaka University. The
authors would like to express their gratitude to former and present graduate
students, especially, Drs. K.Kintaka and H.lshizuki, whose names are included as
Preface VII
dents, especially, Drs. K.Kintaka and H.lshizuki, whose names are included as
coauthors in the publications of the authors' group, for their contribution to the
experimental and calculation work. Finally, the authors would like to thank Dr.
C.Ascheron, Springer Verlag, for his encouragement during the process of writing
this book.
Osaka
March 2003
Toshiaki Suhara
Contents
1. Introduction ••••••••••......•.••••.........••••••••••••••••.•••••••••••••••••••••••••••....•.•••••••........•.•••.• 1
1.1 Nonlinear Optics and Nonlinear-Optic Instruments ..................................... 1
1.2 Waveguide and Integrated Optics ................................................................ 2
1.3. Historical Perspectives on Waveguide NLO Devices ................................. 3
1.4. Future Prospects .......................................................................................... 6
References .......................................................................................................... 7
2. Theoretical Background ••.........•.••.••.••.•••••••••...••.•••••••••.•••••••.•••••••••••.•.••••••••••.•.. 9
2.1 Optical Waveguides ..................................................................................... 9
2.1.1 Waveguide Structures and Electromagnetic Waves ............................. 9
2.1.2 Planar Waveguides ............................................................................. 12
2.1.3 Channel Waveguides .......................................................................... 15
2.2 Nonlinear Optical Polarizations ................................................................. 18
2.2.1 Dielectric Response Function and Susceptibility ............................... 19
2.2.2 Second-Order Nonlinear Polarization ................................................ 20
2.2.3 Third-Order Nonlinear Polarization ................................................... 22
2.3 Coupled-Mode Equations ...................................................................... 24
2.4 Phase Matching .......................................................................................... 26
2.4.1 Coherence Length and Phase Matching ............................................. 26
2.4.2 Birefringence Phase Matching ........................................................... 27
2.4.3 Mode Dispersion Phase Matching ...................................................... 29
2.4.4 Quasi-Phase Matching ........................................................................ 30
2.4.5 Cerenkov-Radiation-Type Phase Matching ........................................ 31
2.4.6 Other Phase Matching Methods ......................................................... 31
References ........................................................................................................ 32
3. Theoretical Analysis of Nonlinear Interactions •••••.•...•••••••••.....•••••.......•••••••. 35
3.1 Guided-Mode Nonlinear-Optic Interactions .............................................. 35
3.1.1 Second-Harmonic Generation ............................................................ 35
3.1.2 Sum-Frequency Generation ................................................................ 44
3.1.3 Difference-Frequency Generation ...................................................... 49
3.1.4 Optical Parametric Amplification ....................................................... 51
3.2 Quasi-Phase Matching by Chirped Grating ............................................... 54
3.2.1 Coupled-Mode Formalism ................................................................. 55
3.2.2 SHG Characteristics and Design Guidelines ...................................... 59
3.3 Cerenkov-Radiation-Type Interaction ....................................................... 63
3.3.1 Green Function Approach .................................................................. 64
X Contents
3.3.2 Coupled-Mode Formalism ................................................................. 65
3.3.3 SHG Characteristics ........................................................................... 68
3 .4 Wavelength Conversion of Ultrashort Pulses ............................................ 73
3.4.1 Coupled-Mode Equations ................................................................... 74
3.4.2 Pulse Walkoffand Phase Matching Bandwidth ................................. 75
3.4.3 Beam Propagation Method Formalism ............................................... 76
3.4.4 Interaction Characteristics .................................................................. 77
3.5 Cascaded Second-Order Nonlinear-Optic Effects ..................................... 82
3.5.1 Nonlinear Phase Shift ......................................................................... 82
3.5.2 Effective Nonlinear Refractive Index ................................................. 87
References ....................................................................................................... 88
4. Nonlinear-Optic Interactions in Resonator ................................................... 91
4.1 Second-Harmonic Generation in Optical Resonator.. ................................ 91
4.1.1 Description of Resonant SHG Devices .............................................. 91
4.1.2 Singly Resonant SHG Devices ........................................................... 95
4.1.3 Doubly Resonant SHG Devices ......................................................... 98
4.2 Optical Parametric Oscillation ................................................................. 100
4.2.1 Waveguide Resonators and Resonant Modes ................................... 100
4.2.2 Singly Resonant Oscillator.. ............................................................. 101
4.2.3 Doubly Resonant Oscillator ............................................................. 104
4.2.4 Pump-Resonant Oscillators .............................................................. 107
References ..................................................................................................... 108
5. Quantum Theory of Nonlinear-Optic Devices ............................................ 109
5.1 Quantum States of Optical Waves ........................................................... 110
5.1.1 Field Quantization ............................................................................ 110
5.1.2 Photon Number States ...................................................................... 111
5.1.3 Coherent States ................................................................................. 111
5.1.4 Squeezed States ................................................................................ 113
5.2 Expressions for Quantum Fluctuation ..................................................... 114
5.2.1 Field Amplitude Fluctuation ............................................................ 114
5.2.2 Covariance Matrix and Squeezing Spectrum ................................... 115
5.2.3 Intensity Noise ................................................................................. 117
5.3 Traveling-Wave Second-Harmonic Generation ....................................... 118
5.3.1 Nonlinear Coupled-Mode Equations and Steady-State Solutions .... 118
5.3.2 Linearized Differential Equation for Fluctuation ............................. 120
5.3.3 Fluctuation Propagation Matrix ........................................................ 120
5.3.5 Fluctuation and Squeezing Characteristics ....................................... 12 3
5.4 Resonant Second-Harmonic Generation .................................................. 124
5.4.1 Steady-State Solutions ...................................................................... 124
5.5 Degenerate Parametric Amplification ...................................................... 130
5.6 Sum-Frequency Generation ..................................................................... 133
5.7 Difference-Frequency Generation and Parametric Amplification ........... 134
5.8.1 Fluorescence Power.. ........................................................................ 136
5.8.2 Photon Correlation ........................................................................... 138
Contents XI
References ...................................................................................................... 139
6. Waveguide Fabrication and Characteristics ............................................... 141
6.1 Proton-Exchanged Waveguides ............................................................... 141
6.1.1 Anneal/Proton-Exchange .................................................................. 142
6.1.2 Variations of Proton Exchange ......................................................... 147
6.2 Ion-Exchanged Waveguides .................................................................... 148
6.3 Metal-Diffused Waveguides .................................................................... 150
6.3.1 Ti-Indiffused Waveguides ................................................................ 150
6.3.2 Zn-Indiffused Waveguides ............................................................... 151
6.4 Ion-Implanted Waveguides ...................................................................... 151
6.5 Other Waveguide Fabrication Techniques ............................................... 152
6.5.1 Liquid Phase Epitaxy ........................................................................ 152
6.5.2 Ridge Formation ............................................................................... 152
6.6 Photorefractive Damages ......................................................................... 153
6.7 Reduction of Nonlinear-Optic Effect ....................................................... 154
References ...................................................................................................... 155
7. Fabrication of QPM Structures. ..........•........................................................ 159
7.1.1 Crystal Structures and Spontaneous Polarization ............................. 160
7.1.2 Ferroelectric Domain Inversion and Hysteresis Loop ...................... 161
7.2 Review ofQPM Structure Fabrication Work. .......................................... 168
7.2.1 High Temperature Methods .............................................................. 168
7.2.2 Proton and Ion Exchange Methods ................................................... 170
7.2.3 Room Temperature Methods ............................................................ 172
7.2.4 Materials Other than Ferroelectrics .................................................. 174
7.3 Electron-Beam Direct Writing Method .................................................... 176
7.3.1 Procedure and Mechanism ............................................................... 176
7.3.2 Domain-Inverted Gratings ................................................................ 177
7.4 Pulse Voltage Application Method .......................................................... 179
7.4.2 Control for Pulse Voltage Application ............................................. 183
7.4.3 Domain Inverted Gratings ................................................................ 185
References ...................................................................................................... 187
8. Second-Harmonic Generation Devices ........................................................ 193
8.1 Review of Research Work on Waveguide SHG Devices ........................ 193
8.1.1 Dielectric Thin-Film Waveguides .................................................... 194
8.1.2 Ferroelectric Crystal Waveguides .................................................... 196
8.1.3 Semiconductor Waveguides ............................................................. 203
8.1.4 Organic Waveguides ........................................................................ 205
8.1.5 Glass Waveguides ............................................................................ 207
8.2 Prototype Waveguide QPM-SHG Devices .............................................. 207
8.2.1 Design and Theoretical Performances .............................................. 207
8.2.2 Experimental Performances .............................................................. 211
8.3 Modified Waveguide QPM-SHG Devices ............................................... 214
8.3.1 Structures for Residual Phase Mismatch Compensation .................. 214