The Third Binational USA-USSR Symposium titled "Laser Optics of Con densed Matter" was held in Leningrad 1 June - 5 June 1987. This volume con tains the full text of 64 papers presented at (or prepared for) the Symposium in both plenary and poster sessions. This Symposium reestablished the very productive series of "Light Scattering" Binational Symposia which were initi ated in Moscow in 1975. Unfortunately there was an eight-year hiatus follow ing the Second Symposium in New York (1979). This interval, caused by serious chilling of the climate of USA-USSR collaboration, deprived the active scien tists on both sides of the opportunity to meet and interact in the active format of a conference. During this eight year interval there has been very rapid and intense development of scientific activity in the general area of laser optics phe nomena. The development of ultrafast laser sources has permitted rapid advances in time resolved spectroscopy and ultrafast processes; the field of optical bistability and strong nonlinearity became a hot topic; and intense work is now underway to clarify ideas of photon localization. These new dev elopments complement many advances in the study of low dimensional systems such as surfaces, new work on phase transitions, and novel studies of elemen tary excitations such as polariton-excitons in localized environments such as quantum wells and heterojunctions.

The Fourth USA-USSR Symposium. on The Physics of Optical Phenomena and Their Use as Probes of Matter, was held in Irvine, California, January 23-27, 1990. Participating in the Symposium were 22 scientists from the USSR and 29 from the USA. In addition, to provide an international dimension to this Symposium without, however, compromising significantly its essentially binational character, 7 non-US and non-USSR scientists were invited to take part in it. The present volume is the proceedings of that Symposium, and contains all manuscripts received prior to August 1, 1990, representing. scientific contributions presented. A few manuscripts were not received, but for completeness the corresponding abstract is printed.. Three previous USA/USSR Binational Symposia on related topics have been held, viz. "Theory of Light Scattering in Condensed Matter" (Moscow, 1975), "Light Scattering in Solids" (New York, 1979), and "Laser Optics of Condensed Matter" (Leningrad, 1987). These meetings were evaluated by the participants as highly successful and provided invaluable oppor tunities for researchers to exchange information and to initiate colla borative work which led to research visits by US physicist to Soviet laboratories, and vice versa, and which continue to the present day.

Symposia - Partial Contents: Hot Electrons in Semiconductors and Metals; Laser Spectroscopy of Hot Photoluminescence in Semiconductors Energy Spectrum and Relaxation Times; GaSe Nonlinear Susceptibility and Relaxation Process Rates; Picosecond Laser Studies of Collisional Effects on Rotational Processes in Liquids; The Oscillations of 2D-Electron Density of States in a Transverse Magnetic Field; Excitonic Optical Nonlinearities in Semiconductor Quantum Wells; Gain Saturation and Features in Threshold Behavior of AIIIBv Heterostructure Lasers; Single Frequency Diode Laser with a High Temperature Stability of the Emission Line; Raman Studies of Phonons in GaAs/AlGaAs Superlattices; Nonlinear Distributed Coupling into Guided Waves; Picosecond Nonlinear Optical Spectroscopy of Semiconductor Surface Structure Transformations; Optical Spectroscopy of Size Effects in Semiconductor Microcrystals; The Spectrum of Light Propagation Times through a Disordered Medium and Mesoscopic Fluctuations; Anderson Localization of Classical Photons in a Disordered Dielectric; Electron Single-Particle Light Scattering in InP Crystals and in Mixed Crystals GaXI1-xP; Are Phasons Observable in Optics?; Laser Spectroscopy of Fast KNO3 Ferroelectric Switches; Inelastic Light Scattering by Magnons in Antiferromagnetic EuTe; Excitons, Polaritons; Photoactive Materials, Photorefraction, Hole Burning, Holography; Optical Bistability in Semiconductors and Liquid Crystals. (jhd).