Enhanced transmission has been associated with surface wave excitation and aperture arrangement on a metallic film.
Aperture resonances, however, have been demonstrated to exist without an order in the arrangement of apertures, with
properties dependent on geometry and optical properties of the aperture filling. These resonances are accompanied by
wavelength-dependent phase shifts in the transmitted fields offering the potential for manipulation of wavefields. Here,
we present Finite Element Method simulations investigating light passing through periodic arrays of nanometric spatially
varying near-resonant slits perforated in a metallic film. We show that a tailored phase modulation can be introduced into
an incident optical wavefield by varying aperture sizes around the resonant dimensions for a particular design
wavelength, permitting control of wavefields which can be employed for beam deflection, beam focusing or for
producing a wavelength-specific spatial field change.
Great effort has been made in the recent past to develop new non-destructive imaging modalities for both two and three
dimensional objects, based on the phase properties of a specimen. Quantitative phase tomography (QPT) is a hybrid
technique that has been proposed to provide three-dimensional (3D) refractive index (RI) profiling of irregular phase
objects by combining transverse phase measurements with traditional tomographic reconstruction techniques. This
profiling is accomplished through measurements of sets of projections which are ultimately related to the RI values of
the object's transverse cross-section. This is particularly useful for 3D refractive index determination of specimens where
staining is not appropriate or for materials that cannot be stained and is essential to many applications in photonics and
biotechnology. This article reviews recent developments in quantitative phase tomography as they are presently available
and suggests future applications based on current research on the 3D RI. The enabling elements for 3D QPT in the
context of four key areas are discussed: the effect of the refractive index of the surrounding matching fluid, spatial
resolution, phase accuracy and optimal defocus. Recent progress and future perspectives related to each of these areas is
presented with regard to various test objects of known optical properties.