Single-mode fibers are the most advanced means of transmitting information, since they provide extremely low attenuation and very high bandwidths. At present, long distance communication by single-mode fibers is cheaper than by conventional copper cables, and in the future single-mode fibers will also be used in the subscriber loop. Since single-mode fibers have many applications, a variety of people need to understand this modern transmission medium. How­ ever, waveguiding in single-mode fibers is much more difficult to understand than waveguiding in copper lines. A single-mode fiber is a dielectric waveguide operated at optical wave­ lengths. Since 1961, I have been involved in experimental and theoretical re­ search on dielectric rod waveguides in the microwave region. From the experi­ ments, I learned much about the properties of a wave guided by a dielectric rod or a glass fiber, especially about its behavior at waveguide discontinuities like bends, gaps, or the waveguide end. Since 1972, my co-workers and I have also been investigating dielectric waveguides at optical frequencies, and since 1973 I have lectured on "Optical Communications". These activities have shown that there is a need for a tutorial introduction to the new technical field of single­ mode fibers. In this book the physical fundamentals are emphasized and the mathematics is limited to the absolutely necessary subjects. Besides presenting a physical explanation of waveguiding in single-mode fibers, it is also the aim of this book to give an overview of the knowledge accumulated in this field.

The contributions of this book represent only a small sample of the work of the many researcher electromagneticians who have had the pleasure of being associated with Professor Papas, either as students or as colleagues. Many of us continue to work in the many and diverse areas that modem electro­ magnetism encompasses. There is, however, a common thread that was derived from our association with Professor Papas that has greatly influenced our thinking and technical style of expression. Professor Papas, from his studies at Harvard, brought with him to Pasadena a very fundamental and classical point of view that was instilled in all those who were associated with him. He saw research problems as a combination offundamental physical and mathematical principles and the electromagnetic "reality. " He searched and demanded clarity and often, in the rather involved and engaging discussions which took place in his office, he demanded that the "baby picture" be clearly drawn on the blackboard. This requirement, certainly for some of us who were working in widely varied subjects ranging from relativistic plasmas to almost periodic media, has forced us to reexamine the fundamentals. The clear and lucid marriage of fundamental concepts to applications has been the trademark of Professor Papas's intellectual tradition, and has greatly in­ fluenced the thinking of all of those who have associated with him.

This volume contains the proceedings of a two-week NATO A.S.I. on Integrated Optics: Physics and Applications, held from August 17 to August 30, 1981 in Erice, Italy. This is the 8th annual Course of the "International School of Quantum Electronics" presented under the auspices of the "E. Majorana" Centre for Scientific Culture. The subject was chosen in order to satisfy the demand for a course on integrated optics which is relevant to the expanding use of fiber optics for communication and signal processing. Integrated Optics, encompassing all of the optical waveguide circuits which are the optical analog of integrated circuits, is finding its way into a variety of applications involving communi­ cations, high speed signal-processing, and sensors of many kinds. However, because the technology is still changing very rapidly, the development of these exciting applications relies heavily upon the physics of the integrated optical circuits themselves and the pro­ cessing techniques used to fabricate them. This NATO A.S.I. provided not only a thorough tutorial treatment of the field, but also through panel discussions and additional lectures treated topics at the forefront of present work. Therefore the character of the Course was a blend of current research and tutorial reviews. "The Physics and Applications of Integrated Optics" could hardly be a more appropriate title to be chosen for this volume. Many of the worlds' acknowledged leaders in the field have been brought together to review and speculate on the accomplishments of integrated optics.

Nonlinear photonics is the name given to the use of nonlinear optical devices for the generation, communication, processing, or analysis of information. This book is a progress report on research into practical applications of such devices. At present, modulation, switching, routing, decision-making, and detection in photonic systems are all done with electronics and linear optoelectronic devices. However, this may soon change, as nonlinear optical devices, e.g. picosecond samplers and switches, begin to complement optoelectonic devices. The authors succinctly summarize past accomplishments in this field and point to hopes for the future, making this an ideal book for newcomers or seasoned researchers wanting to design and perfect nonlinear optical devices and to identify applications in photonic systems.

This thesis presents research on novel laboratory-scale synchrotron X-ray sources based on inverse Compton scattering and applications of their X-ray radiation using the Munich Compact Light Source (MuCLS) as an example. It provides an introduction to the theory of this laser-electron interaction, laser resonators and X-ray interactions with matter. On this basis, upgrades to the laser system including the development of a new laser optic, X-ray beam stabilisation and two techniques for fast X-ray energy switching of inverse Compton sources are presented. On the application side, the beamline, designed and developed for the inverse Compton X-ray source at the MuCLS, is described before various techniques and applications are demonstrated at this laboratory-scale synchrotron X-ray facility. Among them are K-edge subtraction imaging, X-ray phase contrast imaging and X-ray absorption spectroscopy. Additionally, a new X-ray microscopy technique, called full-field structured-illuminationsuper-resolution X-ray transmission microscopy, is presented.

Arnold Sommerfeld's "Mathematische Theorie der Diffraction" marks a milestone in optical theory, full of insights that are still relevant today. In a stunning tour de force, Sommerfeld derives the first mathematically rigorous solution of an optical diffraction problem. Indeed, his diffraction analysis is a surprisingly rich and complex mix of pure and applied mathematics, and his often-cited diffraction solution is presented only as an application of a much more general set of mathematical results. The body of Sommerfeld's work is devoted to the systematic development of a method for deriving solutions of the wave equation on Riemann surfaces, a fascinating but perhaps underappreciated topic in mathematical physics.

Mathematics is a tool for thought. A highly necessary tool in a world where both feedback and non-
linearities abound. Similarly, all kinds of parts of mathematics serve as tools for other parts and for
other sciences.

Environmental and chemical sensors in optical fiber sensor technology The nature of the environment in which we live and work, and the precarious state of many aspects of the natural environment, has been a major lesson for scientists over the last few decades. Public awareness of the issues involved is high, and often coupled with a scepticism of the ability of the scientist and engineer to provide an adequate, or even rapid solution to the preservation of the environment before further damage is done, and to achieve this with a mini­ mum of expenditure. Monitoring of the various aspects of the environment, whether it be external or internal to ourselves and involving chemical, physical or biomedical parameters is an essential process for the well-being of mankind and of the individual. Legis­ lative requirements set new standards for measurement and control all around us, which must be met by the most appropriate of the technologies available, commensurate with the costs involved. Optical fiber sensor technology has a major part to play in this process, both to complement existing technologies and to promote new solutions to difficult measurement issues. The developments in new sources and detectors covering wider ranges of the electromagnetic spectrum, with higher sensitivity, allow the use of techniques that some time ago would have been considered inappropriate or lacking in sufficient sensitivity.