Beam Shaping and Control with Nonlinear Optics

478 Pages·2002·5.154 MB·English

by  George I. Stegeman (auth.), F. Kajzar, R. Reinisch (eds.)

Beam Shaping and Control with
Nonlinear Optics
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Volume 369—Beam Shaping and Control with Nonlinear Optics
edited by F. Kajzar and R. Reinisch
Series B: Physics
Beam Shaping and Control with
Nonlinear Optics
Edited by
F. Kajzar
Commissariat a l’Energie Atomique
Gif-sur-Yvette, France
and
R. Reinisch
Institut National Polytechnique de Grenoble
Grenoble,France
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PREFACE
The field of nonlinear optics, which has undergone a very rapid development since the
discovery of lasers in the early sixties, continues to be an active and rapidly developing re-
search area. The interest is mainly due to the potential applications of nonlinear optics: di-
rectly in telecommunications for high rate data transmission, image processing and
recognition or indirectly from the possibility of obtaining large wavelength range tuneable
lasers for applications in industry, medicine, biology, data storage and retrieval, etc.
New phenomena and materials continue to appear regularly, renewing the field. This
has proven to be especially true over the last five years. New materials such as organics have
been developed with very large second- and third-order nonlinear optical responses. Impor-
tant developments in the areas of photorefractivity, all optical phenomena, frequency conver-
sion and electro-optics have been observed. In parallel, a number of new phenomena have
been reported, some of them challenging the previously held concepts. For example, solitons
based on second-order nonlinearities have been observed in photorefractive materials and
frequency doubling crystals, destroying the perception that third order nonlinearities are re-
quired for their generation and propagation. New ways of creating and manipulating nonlin-
ear optical materials have been developed. An example is the creation of highly nonlinear
(second-order active) polymers by static electric field, photo-assisted or all-optical poling.
Nonlinear optics involves, by definition, the product of electromagnetic fields. As a conse-
quence, it leads to the beam control. This includes amplitude or phase modulation, genera-
tion of new laser frequencies and altering the propagation of beams either in space or time.
Different nonlinear optical interactions and mechanisms lead to a large variety of functions.
The time thus seemed appropriate to us to bring all these new developments into focus
in a summer school format. This was the main objective of the NATO Advanced Science In-
stitute held in Cargese (Corsica, France) August 4–16, 1997. A good understanding of non-
linear optical phenomena and their dependence on wavelength, electronic structure,
structural properties, etc. requires not only an excellent knowledge of the basic laws of phys-
ics, governing the nonlinear optical phenomena, but also a good knowledge of materials and
the laws governing the interaction between light beams in different forms of matter.
The lectures given at the school covered the following topics: nonlinear optical phe-
nomena and their applications, temporal and spatial solitons, third-order effects, organic ma-
terials, organic and inorganic multiple quantum wells, hybrid excitons and microcavity
effects, cascading effects and applications, parametric processes, applications of optical
parametric oscillators and second harmonic generators, the latest developments in nonlinear
magneto-optics, new techniques for molecule orientation, ato-optics, light-induced kinetic
effects in gases, light upconversion to the blue, nonlinear waveguiding optics, photorefrac-
tive effects and photorefractive solitons, χ(2)spatial solitons. The subjects covered by the
school underline the importance of the ever improving fundamental research and continuing
technological developments. We hope that this book will contribute to the dissemination of
v
the theoretical and experimental results concerning this fascinating field of all-optical inter-
actions.
Organization of the school would be impossible without financial support. We are
highly indebted to its main sponsor: the NATO Scientific Affairs Division. The financial con-
tributions from other sources such as Centre National de la Recherche Scientifique, Direc-
tion des Systemes de Forces et de la Prospective de la DGA, Institut National Polytechnique
de Grenoble, LETI-Saclay, and Centre National d’Etude des Telecommunications were also
very helpful and we would like to thank these organizations for their support. We would like
also to acknowledge the Scientific Committee members V. M. Agranovich, G. Assanto, C.
Flytzanis, S. Kryszewski and G. Stegeman for their suggestions and help in the organization
of the school. Thanks are also due to Ms. Amelie Kajzar for her assistance in the organiza-
tional tasks and in the preparation of these proceedings. Finally, many thanks are due to the
staff of the Institut Scientifique de Cargese for its efficiency and kindness from which we
benefited during the school, and more generally to all the lecturers and students for their con-
tribution in making this meeting very pleasant and successful.
François Kajzar
Raymond Reinisch
Saclay and Grenoble
vi
CONTENTS
Introduction to Nonlinear Optics: A Selected Overview . . . . . . . . . . . . . . . . . . . . . . . .1
G. I. Stegeman
Introduction to Ultrafast and Cumulative Nonlinear Absorption and Nonlinear
Refraction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
E. W. Van Stryland
From Dipolar Molecular Engineering to Multipolar Photonic Engineering in
Nonlinear Optics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
J. Zyss and S. Brasselet
MoleculeOrientation Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
F. Kajzar and J.-M. Nunzi
Nonlinear Pulse Propagation along Quantum Well in a Semiconductor Microcavity. . 133
V. M. Agranovich, A. M. Kamchatnov, H. Benisty, and C. Weisbuch
Some Aspects of the Theory of Light Induced Kinetic Effects in Gases . . . . . . . . . . .149
S. Kryszewski
Temporal and Spatial Solitons: An Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
A. Boardman, P. Bontemps, T. Koutoupes, and K. Xie
Spatial Solitons in Quadratic Nonlinear Media . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229
L. Torner
Photorefractive Spatial Solitons. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
M. Segev, B. Crosignani, P. Di Porto, M.-F. Shih, Z. Chen, M. Mitchell, and
G. Salamo
Sub-Cycle Pulses and Field Solitons: Near- and Sub-Femtosecond EM-Bubbles . . . . . 291
A. Kaplan, S. F. Straub, and P. L. Shkolnikov
Nonlinear Waveguiding Optics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
R. Reinisch
Quadratic Cascading: Effects and Applications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
G. Assanto
vii
Nonlinear Optical Frequency Conversion: Material Requirements, Engineered
Materials, and Quasi-Phasematching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
M. Fejer
Low-Power Short Wavelength Coherent Sources: Technologies and Applications. . . . 407
D. Ostrowsky
Artificial Mesoscopic Materials for Nonlinear Optics . . . . . . . . . . . . . . . . . . . . . . . . . . 427
C. Flytzanis
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .465
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .467
viii
INTRODUCTION TO NONLINEAR OPTICS: A SELECTED
OVERVIEW
George I. Stegeman
C.R.E.O.L., University of Central Florida
4000 Central Florida Blvd., Orlando, FL 32816-2700, USA
INTRODUCTION
Historical Perspective
Nonlinear optics (NLO) has enjoyed great success as a discipline for over 30 years now.
Although it was a relative newcomer to nonlinear wave sciences, other examples being
nonlinear fluid dynamics, acoustics, plasmas etc, it has contributed many new phenomena.
Since its inception in 1962, nonlinear optics has passed through many phases and different
topics have been “hot” at any given time.1,2 One of the fascinating features of the nonlinear
optics field is its regenerative power to develop new topics over the years. The first ten years
witnessed demonstration of many of the fundamental interactions such as second harmonic
generation (SHG), sum and difference frequency generation, stimulated Raman, Brillouin and
Rayleigh scattering, self-focusing etc. And many more interesting phenomena were predicted
theoretically, some having to wait two decades before experimental confirmation was
forthcoming. This “novelty” trend continued into the second decade with the development of
multiple nonlinear spectroscopies and their applications to materials science, phase
conjugation, bistability leading to concepts of all-optical signal processing, the beginnings of
nonlinear optics in fibers, etc. The third phase, from about the mid 1980s to the present has had
its own highlights such as the development of nonlinear guided wave optics, especially in
fibers where a whole spectrum of new propagation effects and light induced non-
centrosymmetric effects were found, the exciting development of efficient, widely tunable
sources through optical parametric oscillators, temporal solitons and their potential for long-
haul communications, a surprising variety of spatial solitons, terahertz sources, femtosecond
pulses, generation of tens of higher harmonics in gases etc. One of the exciting recent
developments is the blurring of the roles of second and third order nonlinear optics, namely
the creation of second order nonlinear effects via third order nonlinearities, and the use of
second order effects to mimic third order phenomena. Many of these topics will be discussed
in this book.
The key to applications of nonlinear optics is, has been and always will be the
availability of appropriate materials. The initial stages of the field which focused on
demonstrating and understanding new effects utilized the materials available at that time. For
Beam Shaping and Control with Nonlinear Optics
Edited by Kajzar and Reinisch, Kluwer Academic Publishers, New York, 2002 1
example, for second harmonic generation, materials developed for piezoelectric applications
which also require non-centrosymmetric media were used first. In the case of third order,
much of the early work was done with liquids. Ultimately, the search for better materials was
driven by the realization that in order for any applications to be practical, nonlinear optics had
to move forward from the era in which high power lasers were almost exclusively needed to
observe nonlinear phenomena. Compact semiconductor lasers with 100s of mW power levels
drove the need for sub-watt nonlinear optics. The search for better materials gained
momentum in the mid to late 1970s and continues unabated to the present day. In the case of
second order materials, there have been multiple goals including doubling into the UV region
of the spectrum, widely tunable sources via parametric interactions, inexpensive sources in the
blue, etc. The exciting concept of all-optical processing has fueled third order nonlinear optics
for many years.
Formalism
Traditionally nonlinear optics has been discussed in terms of the nonlinear polarization
induced in a nonlinear medium by the mixing of one or more intense electromagnetic waves2.,3
Typically multiple beams with different frequencies are incident onto a nonlinear medium,
either modifying the linear optical properties of the medium or leading to the generation of new
waves at new frequencies. As a matter of notation, the incident fields E(r,t) of frequency ω
i
and wavevector ki for propagation along the z-axis can be written in the form:
(1)
For plane waves, ei is the electric field unit vector, fi(x,y) = 1 and ai(z), the slowly varying
(complex) amplitude, is normalized so that |a(z)| ²is the intensity in units of W/cm². When
i
the interacting beams are of finite extent, for example in a waveguide, the f (xy) describe the
i
transverse field profiles. The nonlinear polarization
(2)
induced by the mixing of the optical fields has the general form:²
(3)
whereE(r,t) is the total electric field in the medium and χ(n) is the n’th order nonlinearity.
Here the r - ri allow for a spatially non-local response, e.g. carrier diffusion and t - ti allow for
a polarization field at time t to be generated by fields at an earlier time t , for example due to
i
a finite carrier recombination time. For a total field of the form E(r,t) = ∑ ½E(r;ωi) exp[i(ωit
-k r)] + c.c., i.e. an expansion in terms of its Fourier components, the induced polarization
i
can be written as a Taylor’s expansion in the Fourier components of the mixing fields,²
2