The invention ofthe laser 25years ago resulted in powerfullight sources which led to the observation of unexpected and striking phenomena. New fields of science such as holography and nonlinear optics developed constituting the basis of this volume. The classical principle of linear superposition of light wavesdoes not hold anymore. Two laser beams crossing in a suitable material may produce a set of new beams with different directions and frequencies. The interaction of light waves can be understood by considering the optical grating structures which develop in the overlap region. The optical properties of matter become spatially modulated in the interference region of two light waves. Permanent holographic gratings have been produced in this way by photographic processes for many years. In contrast, dynamic or transient gratings disappear after the inducing light source, usually a laser, has been switched off. The grating amplitude is controlled by the light intensity. Dynamic gratings have been induced in a large number ofsolids, liquids, and gases, and are detected by diffraction, 'forced light scattering' of a third probing beam, or by self-diffraction of the light waves inducing the grating. The combined interference and diffraction effect corresponds to four-wave mixing (FWM) in the language of nonlinear optics. The process is called degenerate ifthe frequenciesofthe three incident wavesand the scattered wave are equal. Degenerate four-wave mixing (DFWM) is a simple method to achieve phase conjugation, i.e. to generate a wave which propagates time reversed with respect to an incident wave.

This book presents an account of the course "Spectroscopy of Solid-State Laser-Type Materials" held in Erice, Italy, from June 16 to 30, 1985. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The objective of the course was to present and examine the recent advances in spectroscopy and theoretical modelling relevant to the interpretation of luminescence and laser phenomena in several classes of solid-state materials. The available solid-state matrices (e.g. halides, oxides, glasses, semiconductors) and the full range of possible activators (transition ions, rare earth ions, post-transition ions, actinides, color centres) were considered. By bringing together specialists in the fields of solid-state luminescence and of solid-state laser materials, this course provided a much-needed forum for the critical . assessment of past developments in the R&D of solid-state lasers. Additional objectives of the meeting were to identify new classes of host/activator systems that show promise of laser operation; to alert researchers in solid-state luminescence to current technological needs for solid-state tunable lasers operating in the visible and infrared spectral regions; and generally to provide the scientific background for advanced work in solid state lasers. A total of 71 participants came from 54 laboratories and 21 nations (Austria, Belgium, Canada, F.R. of Germany, France, Greece, Ireland, Israel, Italy, the Netherlands, P.R. of China, Poland, Rumania, Sweden, Switzerland, South Korea, Spain, Turkey, United Kingdom, U.S.A. and U.S.S.R.).

This book highlights recent progress in the chemistry of radicals. Developments include the growing use of lasers to generate radicals, the application of lasers to provide state, angular, polarization, energy and real-time resolution in kinetics and dynamics experiments, the development of theories for handling the reactions of radicals, and the simulation of the reaction dynamics of increasingly larger systems for direct comparison to experimental results. The book emphasizes the increasing interaction between experimental dynamics, kinetics and theory. It is appropriate for chemistry graduate students and researchers about to enter the field. However, the discussions of some topics progress to a more advanced level so that even an expert will find the book useful.

This book highlights recent progress in the chemistry of radicals. Developments include the growing use of lasers to generate radicals, the application of lasers to provide state, angular, polarization, energy and real-time resolution in kinetics and dynamics experiments, the development of theories for handling the reactions of radicals, and the simulation of the reaction dynamics of increasingly larger systems for direct comparison to experimental results. The book emphasizes the increasing interaction between experimental dynamics, kinetics and theory. It is appropriate for chemistry graduate students and researchers about to enter the field. However, the discussions of some topics progress to a more advanced level so that even an expert will find the book useful.

This is the first volume of a set of three within the Springer Series in Optical Sciences, and is devoted to photorefractive effects, photorefractive materials, and their applications. Since the publication of our first two Springer books on Photorefractive Materials and Their Applications (Topics in Applied Physics, Vols. 61 and 62) almost 20 years ago, a lot of research has been done in this area. New and often expected effects have been discovered, theoretical models developed, known effects finally explained, and novel applications proposed. We believe that the field has now reached a high level of maturity, even if research continues in all areas mentioned above and with new discoveries arriving quite regularly. We therefore have decided to invite some of the top experts in the field to put together the state of the art in their respective fields. This after we had been encouraged to do so for more than ten years by the publisher, due to the fact that the former volumes were long out of print.