Second harmonic generation from thin slabs in the discrete dipole approach

The nonlinear optical response of thin Si slabs is calculated using a discrete dipole approach. The s-polarized second harmonic response as a function of the angle of incidence appears to be in reasonable agreement with experimental results. The p-polarized SHG shows a high sensitivity for the shape of the polarizability profile

Polarizability tensor and Kramers-Heisenberg induction

A general expression for the semiclassical, nonrelativistic linear polarizability of an arbitrary volume element V has been derived in the long wavelength approximation. The derivation starts from the expectation value of the dipole strength, as in the original Kramers-Heisenberg paper about optical scattering by atoms. The main requirements underlying the present approach are a separate non-Hermitian part of the Hamiltonian and a frequency dependent damping, which is zero for the static case. Resonant and antiresonant exponentials are both found to be necessary to obtain a proper static response. It is concluded that even parity for the damping has to be preferred from the theoretical point of view, although odd and asymmetric parity yield virtually the same polarizability. The electromagnetic response can still be written in terms of a single complex frequency, in agreement with the requirements of electrodynamics. The resulting expression is suited for the treatment of nonisotropic system

Forgotten factors in the development of dependent clauses in Swedish as a second language

This paper is concerned with the acquisition of Swedish dependent clauses. In a longitudinal study of Belgian foreign language learners of Swedish, three factors were found to be of special relevance in the learner’s successive acquisition of dependent clauses: (i) finiteness, i.e. the difference between finite and non-finite complements; (ii) complementizers, i.e. the acquisition of different complementizers (iii) dependent clause types, i.e. the acquisition and use of different types of dependent clauses. My study emphasizes the importance of acknowledging a wide array of structural factors besides internal word order, which has hitherto been the main focus in studies on the acquisition of Swedish dependent clauses

Rayleigh scattering from single-site polysylane adsorbed on silicon: Theory

An ordered set of dipoles with mutual interaction in the close vicinity of a dielectric surface is studied. The solution of that particular theoretical problem is given rigorously both for the static and dynamic case. It can serve as a description of the polysylane molecules formed at the surface of silicon by means of HOMOCVD or sputtering in a hydrogen atmosphere. The theory can be used to describe the optical behaviour of those molecules, like first the Rayleigh scattering and next also the photoluminescence of those molecules

Exact solution of the optical response of thick slabs in the discrete dipole approach

The recently developed double cell technique, which describes the optical response of an arbitrary semi-infinite dielectric crystal taking into account internal field effects, is extended to include the response of thick slabs. The surface sensitivity of the first technique is fully retained. The implications of the internal field effects on the microscopy of these thick slabs are examined for three simple model systems. Further, we investigated under which conditions deviations from classical Fresnel-behaviour are to be expected and how important these corrections are

Structural contribution to the anisotropic reflection from the Si (110) surface

For a single plane of dipoles of arbitrary configuration the optical reflection has been calculated, using the screened discrete dipole model. Results differ from continuum approaches. Further the results show that the experimentally observed reflection anisotropy has besides the dominating intrinsic contribution, also a structural on

Anisotropic off-normal incidence optical reflection from GaP (110) surfaces

This article contains a theoretical study for off-normal incidence surface induced optical anisotropy (SIOA). The discrete dipole approximation was used to calculate the off-normal incidence optical response of slabs. By means of the two slab approach those results were converted to semi-infinite reflectivities. The calculated ellipsometric parameter δΔ shows large variations near the Brewster angle, but only the p-polarized reflection has a clearly increased SIOA sensitivity. So experimentally a straightforward determination of ΔRp should be preferred. Advantages have to be sought in the optical observation of surface state related phenomena at subbandgap conditions

Contribution of the Internal Field to the Anisotropic Optical Reflectance of GaP(110)

This article presents the theory of optical reflection from thin slabs of GaP(110) by means of the discrete dipole model and focusses especially upon the possible implications of this model for the surface induced optical anisotropy. The reflectance of a semi-infinite sample is extracted from slab calculations and compared with experiments. We find that the internal field has a very important role in determining the surface induced optical anisotropy. We also show that the surface sensitivity of such experiments can be estimated to be about five monolayer

SSHG of uniaxial molecules: Phenomena near brewster's angle

The nonlinear optical behaviour of a crystalline adlayer of unidirectionally oriented macromolecules at a substrate is studied by means of the discrete dipole model. Polar and azimuthal dependence of the second harmonic pp-reflectance is investigated at the fundamental and second harmonic frequencies. The influence of the anisotropic linear properties of the adlayer turns out to be essential