Bernard Bendow – författare

The First Binational USA-USSR Seminar-Symposium on the Theory of Light Scattering in Condensed Matter was held in Moscow 26-30 May 1975. The initial conception for a light scattering seminar of about fifty scientists - half from each side, including theorists and experimenters "well versed in theory" - arose from discussions between Professor J. L. Birman and Professor K. K. Rebane at the 1971 Paris International Conference on Light Scattering in Solids. This conception won approval among the active scientists on both sides. After considerable planning and some delays, it received both material support and encouragement from the appro­ priate organizations on each side: in the USA: The National Science Foundation (Division of International Programs), and the National Academy of Sciences; in the USSR: the Academy of Sciences USSR. A variety of reasons contributed to the positive response on both sides: for example, the considerable and high level of theoretical and experimental scientific activity on both sides in laser-related light scattering, optics, and generally - electro­ dynamics of condensed media - some along rather similiar lines; the impediments to free and easy communication and travel be­ tween USA and USSR scientists working on related problems; plus the desire to improve both contacts, and the free flow of informa­ tion and individuals, to the mutual advantage of both sides.

The First Binational USA-USSR Seminar-Symposium on the Theory of Light Scattering in Condensed Matter was held in Moscow 26-30 May 1975. The initial conception for a light scattering seminar of about fifty scientists - half from each side, including theorists and experimenters "well versed in theory" - arose from discussions between Professor J. L. Birman and Professor K. K. Rebane at the 1971 Paris International Conference on Light Scattering in Solids. This conception won approval among the active scientists on both sides. After considerable planning and some delays, it received both material support and encouragement from the appro­ priate organizations on each side: in the USA: The National Science Foundation (Division of International Programs), and the National Academy of Sciences; in the USSR: the Academy of Sciences USSR. A variety of reasons contributed to the positive response on both sides: for example, the considerable and high level of theoretical and experimental scientific activity on both sides in laser-related light scattering, optics, and generally - electro­ dynamics of condensed media - some along rather similiar lines; the impediments to free and easy communication and travel be­ tween USA and USSR scientists working on related problems; plus the desire to improve both contacts, and the free flow of informa­ tion and individuals, to the mutual advantage of both sides.

Although much work has been performed on measure­ ments and interpretation of light absorption by opaque or nearly opaque solids, it is surprising to note that until recently relatively little reliable experimental data, and much less theoretical work was available on the nature of transparent solids. This, in spite of the fact that a vast majority of engineering and device ap­ plications of a solid depend on its optical transparency. Needless to say, all solids are both transparent and opa­ que depending on the spectral region of consideration. The absorption processes that limit the transparency of a solid are either due to lattice vibrations, as in ionic or partially ionic solids, or due to electronic transi­ tions, both intrinsic and impurity-induced. For most materials, a sufficiently wide spectral window exists be­ tween these two limits, where the material is transpar­ ent. In general, the absorption coefficient, in the long wavelength side of, but sufficiently away from, the fun­ damental absorption edge, is relatively structureless and has an exponential dependence on frequency. Recent evi­ dence suggests that in the short wavelength side of the one-phonon region, but beyond two- or three-phonon sin­ gularities, the absorption coefficient of both polar and nonpolar solids is also relatively structureless and de­ pends exponentially on frequency.

Although much work has been performed on measure­ ments and interpretation of light absorption by opaque or nearly opaque solids, it is surprising to note that until recently relatively little reliable experimental data, and much less theoretical work was available on the nature of transparent solids. This, in spite of the fact that a vast majority of engineering and device ap­ plications of a solid depend on its optical transparency. Needless to say, all solids are both transparent and opa­ que depending on the spectral region of consideration. The absorption processes that limit the transparency of a solid are either due to lattice vibrations, as in ionic or partially ionic solids, or due to electronic transi­ tions, both intrinsic and impurity-induced. For most materials, a sufficiently wide spectral window exists be­ tween these two limits, where the material is transpar­ ent. In general, the absorption coefficient, in the long wavelength side of, but sufficiently away from, the fun­ damental absorption edge, is relatively structureless and has an exponential dependence on frequency. Recent evi­ dence suggests that in the short wavelength side of the one-phonon region, but beyond two- or three-phonon sin­ gularities, the absorption coefficient of both polar and nonpolar solids is also relatively structureless and de­ pends exponentially on frequency.

In June 1978 the University of Rhode Island conducted a three-day short course on Recent Advances in Fiber Optics. followed by a two-day conference on the Physics of Fiber Optics. The course contained over a dozen lectures spanning a wide range of subject matter from fundamental theory to operational systems. presented by well-known scientists from industry. government and academic institutions. The conference. on the other hand. emphasized basic research on fiber optics and related subjects. This volume contains both papers presented at the conference. as well as the majority of the lectures from the course (the written versions were solicited on a voluntary basis for this volume). In some cases the papers in this volume represent expanded or otherwise modified versions of the original presentations. One of the principal aims of the conference was promulgation of novel and/or unconventional concepts. For this reason. the papers in this volume cover subjects such as bistable optical switches. fiber acoustic sensors. extruded infrared fibers. compressively coated glass fibers. and soliton propagation in fibers.