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.

Table of Contents:
Section I Multiphonon Absorption.- Theory of Multiphonon Absorption: A Review.- Multiphonon Absorption for Various Forms of the Anharmonic Potential.- Cumulant Methods in the Theory of Multiphonon Absorption.- The High Frequency Tail of the Lattice Absorption Spectra of Simple Crystals.- Optical Absorption by Alkali Halides: Possible Structure in the Multiphonon Region.- Experimental Studies of Multiphonon IR Absorption.- Temperature Dependence of Multiphonon Absorption in Fluorite Crystals.- Multiphonon Absorption in the Alkaline Earth Fluorides.- Multiphonon Absorption in KC?, NAC? and ZnSe.- Two-Phonon Absorption Spectra of III-V Compound Semiconductors.- Section II Electronic Processes.- Urbach's Rule.- Magnetic Circular Dichroism of the Urbach Edge in KI, CdTe and T?C?.- Theory of New Transients and Optical Phenomena in Spatially Dispersive Media.- Dispersion of the Elasto-Optic Constants of Potassium Halides.- Optical Transmission in Iodine Transported ?-HgS.- Section III Impurity Effects.- Impurity Induced Absorption in Transparent Crystals.- Raman, Photoconductive and Acoustoelectric Probes of Residual Deep Impurities and Absorption in GaAs.- Identification of Fe4+, Fe5+ and Fe4+-VO Photochromic Absorption Bands in SrTiO3.- Picosecond Spectroscopy of Transient Absorption in Pure KC?.- Section IV Glasses.- Highly Transparent Glasses.- Multiphonon Absorption in the Chalcogenide Glasses As2S3 and GeS2.- Multiphonon Absorption in Chalcogenide Glasses.- Theory of Multiphonon Absorption in the Transparent Regime of Amorphous Solids.- Light Scattering from Composition Fluctuations in the Superspinodal Region of a Phase-Separating Oxide Glass.- Two-Photon and Two-Step Absorption in Glass Optical Waveguide.- Optically Induced Effects in Photoluminescence Studies of Chalcogenide Glasses.- Section V Multiphoton Processes and Nonlinear Effects.- Nonlinear Spectroscopy in Transparent Crystals.- HF and CO2 Laser Measurements of Dispersion of the Nonlinear Susceptibility in Zinc-Blende Crystals.- Multiphoton Ionization Probability and Nonlinear Absorption of Light by Transparent Solids.- Nonlinear Spectroscopy of Excitons in CuC?.- Nonlinear Wave Propagation in a Transparent Medium.- Picosecond Laser-Induced Damage in Transparent Media.- Second-Harmonic Generation of Intense Laser Light in Transparent Centrosymmetric Solids.- Section VI Measurement Techniques.- A Review of Techniques for Measuring Small Optical Losses in Infrared Transmitting Materials.- Improved Laser Calorimetric Techniques.- Measurement of Small Absorption Coefficients from Thermally Induced Shifts at the Fundamental Edge.- An Alternative Way to Determine Absorption Coefficients in Highly Transparent Solids: Theory.- A Calorimetric Technique for the Measurement of Low Optical Absorption Losses in Bulk Glass and Optical Communication Fibres.- Raman Scattering Technique to Evaluate Losses in GaAs Dielectric Waveguides.- Accurate Spectrophotometer for the Attenuation Measurement of Low-Loss Optical Materials.- Surface Studies with Acoustic Probe Techniques.- A 10.6 Micron Modulated Light Ellipsometer.- Measurements of Stress-Optic Coefficients in the Transparent Regime of Solids.- Measuring Photoelastic and Elastic Constants of Transparent Materials by Application of Static Stress.- List of Contributors.