We develop a simple local-field-effect theory in order to calculate the polarization near the surface and the surface dielectric response of crystals. We obtain a surface-induced anisotropy in all the optical properties of cubic crystals. A calculation of the reflectance anisotropy of a Ge(110) surface is in good agreement with recent measurements.

We obtain exact expressions for the Casimir forces between arbitrary materials using the concept of surface impedance. We verify their consistency with the well-known expressions for perfect conductors and with Lifshitz formula for semi-infinite local homogeneous media. As an application we present a full and rigorous calculation of the Casimir force between two metallic half spaces described by a hydrodynamic nonlocal dielectric response.

We calculate the dielectric response of free-standing and supported two-dimensional layers of polarizable entities, such as metallic particles or adsorbed molecules. We take into account dipole-dipole and the image interaction and investigate the effects of disorder within a two-dimensional renormalized polarizability theory. The behavior of the resonances arising from both the single particle’s and the substrate’s surface plasmon is studied.

We calculate the nonlinear dipole and quadrupole moments induced at the second-harmonic (SH) frequency $2\omega$ in a small dielectric sphere by an inhomogeneous monochromatic electric field of frequency $\omega .$ We neglect finite-size effects and assume that the selvedge region of the sphere is thin enough so that the surface may be considered locally flat. The second-order dipole displays resonances corresponding to the excitation of dipolar and quadrupolar plasmons at $\omega$ and a dipolar plasmon at $2\omega ,$ besides the resonances in the nonlinear surface response parameters a, b, and f. The second-order quadrupole, on the other hand, has resonances corresponding to those of a, b, and f, and to the excitation of dipolar surface plasmons at $\omega$ only. Depending on the relation between the size of the sphere and the spatial scale of variation of the field, the SH radiation may be dominated by either dipolar or quadrupolar scattering, with a crossover region. As an application, we calculate the SH scattering of a Si sphere lying at various distances above a dielectric substrate.

We report the first observation of a large (more than 10%) reflectance anisotropy on a Ag(110) single crystal. We reproduce the experimental data fairly well by use of a theoretical model, based on the quasistatic approximation, which takes into account both the actual geometry of the crystal surface and the interband and intraband transitions. This demonstrates that the main effect is the screened surface local-field effect on resonant dipolar oscillation localized near the surface.

We obtain closed-form expressions for the macroscopic dielectric response of systems with spatial fluctuations, taking into account the local-field effect. The macroscopic response is written, without reference to any specific representation, in terms of the microscopic dielectric operator and the projection operators that extract the average and the fluctuation components of the microscopic fields. The results are very general since few assumptions are made about the nature of the system and of its microscopic response, and very relaxed conditions are imposed on the average and fluctuation projectors. We put special emphasis on systems for which the length scale of the fluctuations is much smaller than the wavelength of light.