In recent years substantial progress has been made in the detection of surface phonons owing to considerable improvements in inelastic rare gas scattering tech niques and electron energy loss spectroscopy. With these methods it has become possible to measure surface vibrations in a wide energy range for all wave vectors in the two-dimensional Brillouin zone and thus to deduce the complete surface phonon dispersion curves. Inelastic atomic beam scattering and electron energy loss spectroscopy have started to play a role in the study of surface phonons similar to the one played by inelastic neutron scattering in the investigation of bulk phonons in the last thirty years. Detailed comparison between experimen tal results and theoretical studies of inelastic surface scattering and of surface phonons has now become feasible. It is therefore possible to test and to improve the details of interaction models which have been worked out theoretically in the last few decades. At this point we felt that a concise, coherent and self-contained guide to the rapidly growing field of surface phonons was needed."

The text develops the basic principles that underlie nonlinear optical phenomena in matter, in an approach oriented to the general reader or student with a background in classical electromagnetic theory. It begins with a discussion of linear wave propagation in dispersive media, moves into weak nonlinearities which can be discussed in a pertuberative manner, then examines strong nonlinear effects (solitons, chaos). The emphasis is on the macroscopic description on nonlinear phenomena, within a semi-classical framework. The text is aimed at the student or researcher who is not a specialist in optics, and who wishes to acquire an introduction to the principal concepts as a precursor to the consultation of the specialized literature.