Super-resolution and apodization with discrete adaptive optics.

High-resolution imaging is of great importance in various fields. The use of pupil phase-only filters (PPF) exceeds the diffraction limit of the imaging system in a simple way. When dealing with distorted wavefronts, however, PPF require that aberrations be compensated for. In this paper, we introduce a novel technique consisting of the use of discrete adaptive optics with PPFs so that the compensating device implements the PPF at the same time. Analysis of the theory for point spread function reshaping using PPFs has enabled us to develop a new approach to characterizing apodizing filters. A validation experiment has been carried out, the first of its kind to our knowledge, in which a number of PPFs were combined with two levels of compensation. Our experimental results are discussed.

Scattering from particles on surfaces: visibility factor and polydispersity.

We have developed an experimental method based on the visibility factor of light-scattering minima to obtain size-polydispersity information from contaminants upon a flat substrate. We verify the method by using double-interaction-model calculations and use this technique to examine experimentally the radial variation of a micrometer-sized fiber and the size polydispersity of spherical particles upon a substrate.

Scattering by a metallic cylinder on a substrate: burying effects.

Experimental measurements of the light scattered from a metallic circular cylinder, with a section diameter comparable with the incident wavelength, upon a metallic flat substrate are presented. The validity of the theoretical numerical calculation obtained from a one-dimensional model based on Maxwell's coupled integral equations for real metals is demonstrated by comparison with the experimental results. The theoretical model is able to reproduce a geometric feature as the partial burying of the cylinder in the substrate because of the sputtering process.

Electromagnetic wave scattering from conducting cylindrical structures on flat substrates: study by means of the extinction theorem.

The extinction theorem has been applied to the study of wave scattering from a non-single-valued surface composed of an infinitely long cylinder on a flat substrate, both of which are assumed to be perfect conductors. Cylinder diameters ranging from 0.1 to 4λ (λ being the incident wavelength) are considered. The calculation method is discussed for this kind of geometry. The study has been performed for both S (perpendicular) and P (parallel) polarizations when the direction of an incident Gaussian beam is perpendicular to the cylinder axis and the direction of the scattered wave is in the plane of incidence. The surface-current density on the flat substrate and on the cylinder has also been analyzed.

Theoretical study of birefringent filters as intracavity wavelength selectors.

A detailed theoretical study of the transmission function of birefringent filters using exact 4 x 4 matrix formalisms is presented. The Brewster-angle effect for the filters acting as intracavity wavelength selectors is also analyzed. Finally, the change in phase of the transmitted wave is calculated and the resonance condition of a cavity with a birefringent-type selector is obtained. The results are compared with those obtained from the usual Jones method.