22 research outputs found
Extraordinary optical transmission and vortex excitation by periodic arrays of Fresnel zone plates
Extraordinary optical transmission and good focusing properties of a
two-dimensional scattering structure is presented. The structure is made of
Fresnel zone plates periodically arranged along two orthogonal directions. Each
plate consists of two ring-shaped waveguides supporting modes that match the
symmetry of a circularly polarized incident plane wave. High field
concentration at the focal plane is obtained with short transverse and long
longitudinal foci diameters. Optical vortex excitation in a paraxial region of
the transmitted field is also observed and analysed in terms of
cross-polarisation coupling. The structure presented may appear useful in
visualization, trapping and precise manipulations of nanoparticles.Comment: 13 pages, 10 figure
Geometrical Optics of Beams with Vortices: Berry Phase and Orbital Angular Momentum Hall Effect
We consider propagation of a paraxial beam carrying the spin angular momentum
(polarization) and intrinsic orbital angular momentum (IOAM) in a smoothly
inhomogeneous isotropic medium. It is shown that the presence of IOAM can
dramatically enhance and rearrange the topological phenomena that previously
were considered solely in connection to the polarization of transverse waves.
In particular, the appearance of a new-type Berry phase that describes the
parallel transport of the beam structure along a curved ray is predicted. We
derive the ray equations demonstrating the splitting of beams with different
values of IOAM. This is the orbital angular momentum Hall effect, which
resembles Magnus effect for optical vortices. Unlike the recently discovered
spin Hall effect of photons, it can be much larger in magnitude and is inherent
to waves of any nature. Experimental means to detect the phenomena is
discussed.Comment: 5 pages, 2 figure
Properties of Physical Systems: Transient Singularities on Borders and Surface Transitive Zones
Certain alternative properties of physical systems are describable by
supports of arguments of response functions (e.g. light cone, borders of media)
and expressed by projectors; corresponding equations of restraints lead to
dispersion relations, theorems of counting, etc. As supports are measurable,
their absolutely strict borders contradict the spirit of quantum theory and
their quantum evolution leading to appearance of subtractions or certain needed
flattening would be considered. Flattening of projectors introduce transitive
zones that can be examined as a specification of adiabatic hypothesis or the
Bogoliubov regulatory function in QED. For demonstration of their possibilities
the phenomena of refraction and reflection of electromagnetic wave are
considered; they show, in particular, the inevitable appearing of double
electromagnetic layers on all surfaces that formerly were repeatedly
postulated, etc. Quantum dynamics of projectors proves the neediness of
subtractions that usually are artificially adding and express transient
singularities and zones in squeezed forms.Comment: 12 p
Cross-polarized normal mode patterns at a dielectric interface
Basic features of narrow optical beam interactions with a dielectric interface are analysed. As it was recently shown, two types of paraxial beams – elegant Hermite-Gaussians of linear polarization and elegant Laguerre-Gaussians of circular polarization – can be treated as vector normal modes of the interface [1]. In this contribution the problem of normal modes is discussed with special attention paid for the case of beam oblique incidence. Excitation of higher-order modes by cross-polarization coupling is described and it is shown that this process critically depends on a propagation direction of the incident beam. Besides the expected changes of mode indices induced by generalised transmission and reflection matrices, the new phenomenon of optical vortex spectral splitting at the interface is revealed and off-axis spectral placements of the splitted vortices are determined. Results of numerical simulations given here for beam reflection entirely confirm theoretical predictions even for beams beyond the range of paraxial approximation