264 research outputs found
Bessel beam through a dielectric slab at oblique incidence: the case of total reflection
The oblique incidence of a Bessel beam on a dielectric slab with refractive
index n1 surrounded by a medium of a refractive index n>n1 may be studied
simply by expanding the Bessel beam into a set of plane waves forming the same
angle with the axis of the beam. In the present paper we examine a Bessel beam
that impinges at oblique incidence onto a layer in such a way that each
plane-wave component impinges with an angle larger than the critical angle.Comment: 10 pages, 6 figure
Circularly Symmetric Apodization via Starshaped Masks
Recently, we introduced a class of shaped pupil masks, called spiderweb
masks, that produce point spread functions having annular dark zones. With such
masks, a single image can be used to probe a star for extrasolar planets. In
this paper, we introduce a new class of shaped pupil masks that also provide
annular dark zones. We call these masks starshaped masks. Given any circularly
symmetric apodization function, we show how to construct a corresponding
starshaped mask that has the same point-spread function (out to any given outer
working distance) as obtained by the apodization.Comment: Paper also at:
http://www.orfe.princeton.edu/~rvdb/tex/starshape/ms.pdf Updated to clarify
misleading statements regarding total throughput for apodizations and their
corresponding starshaped mask
Ultrasmall spot size scanning laser ophthalmoscopy
An ultrasmall spot size scanning laser ophthalmoscope has been developed that employs an annular aberration-corrected incident beam to increase the effective numerical aperture of the eye thereby reducing the width of the probing light spot. Parafovea and foveal cone photoreceptor visibility determined from small area retinal image scans are discussed from the perspective of mode matching between the focused incident beam and the waveguide modes of individual cones. The cone visibility near the fovea centralis can be increased with the annular illumination scheme whereas the visibility of larger parafovea cones drops significantly as a consequence of poorer mode match. With further improvements of the implemented wavefront correction technology it holds promise for individual cone-photoreceptor imaging at the fovea centralis and for optical targeting of the retina with increased resolution
Gravitational diffraction radiation
We show that if the visible universe is a membrane embedded in a
higher-dimensional space, particles in uniform motion radiate gravitational
waves because of spacetime lumpiness. This phenomenon is analogous to the
electromagnetic diffraction radiation of a charge moving near to a metallic
grating. In the gravitational case, the role of the metallic grating is played
by the inhomogeneities of the extra-dimensional space, such as a hidden brane.
We derive a general formula for gravitational diffraction radiation and apply
it to a higher-dimensional scenario with flat compact extra dimensions.
Gravitational diffraction radiation may carry away a significant portion of the
particle's initial energy. This allows to set stringent limits on the scale of
brane perturbations. Physical effects of gravitational diffraction radiation
are briefly discussed.Comment: 5 pages, 2 figures, RevTeX4. v2: References added. Version to appear
in Phys. Rev.
Exotic radiation from a photonic crystal excited by an ultra-relativistic electron beam
We report the observation of an exotic radiation (unconventional
Smith-Purcell radiation) from a one-dimensional photonic crystal. The physical
origin of the exotic radiation is direct excitation of the photonic bands by an
ultra-relativistic electron beam. The spectrum of the exotic radiation follows
photonic bands of a certain parity, in striking contrast to the conventional
Smith-Purcell radiation, which shows solely a linear dispersion. Key
ingredients for the observation are the facts that the electron beam is in an
ultra-relativistic region and that the photonic crystal is finite. The origin
of the radiation was identified by comparison of experimental and theoretical
results.Comment: 4 pages, 5 figure
Shannon dimensionality of quantum channels and its application to photon entanglement
We introduce the concept of Shannon dimensionality D as a new way to quantify
bipartite entanglement as measured in an experiment. This is applied to
orbital-angular-momentum entanglement of two photons, using two state analyzers
composed of a rotatable angular-sector phase plate that is lens-coupled to a
single-mode fiber. We can deduce the value of D directly from the observed
two-photon coincidence fringe. In our experiment, D varies between 2 and 6,
depending on the experimental conditions. We predict how the Shannon
dimensionality evolves when the number of angular sectors imprinted in the
phase plate is increased and anticipate that D = 50 is experimentally within
reach.Comment: 4 pages, 3 figures, accepted for Physical Review Letter
Intensity‐Enhanced Apodization Effect on an Axially Illuminated Circular‐Column Particle‐Lens
A particle can function as a refractive lens to focus a plane wave, generating a narrow, high intensive, weak‐diverging beam within a sub‐wavelength volume, known as the ‘photonic nanojet’. It is known that apodization method, in the form of an amplitude pupil‐mask centrally situated on a particle‐lens, can further reduce the waist of a photonic nanojet, however, it usually lowers the intensity at the focus due to blocking the incident light. In this paper, the anomalously intensity‐enhanced apodization effect was discovered for the first time via numerical simulation of focusing of the axially illuminated circular‐column particle‐lenses, and a greater than 100% peak intensity increase was realised for the produced photonic nanojets
Simulating human photoreceptor optics using a liquid-filled photonic crystal fiber
We introduce a liquid-filled photonic crystal fiber to simulate a retinal cone photoreceptor mosaic and the directionality selective mechanism broadly known as the Stiles-Crawford effect. Experimental measurements are realized across the visible spectrum to study waveguide coupling and directionality at different managed waveguide parameters. The crystal fiber method is a hybrid tool between theory and a real biological sample and a valuable addition as a retina model for real eye simulations
Image processing as state reconstruction in optics
The image reconstruction of partially coherent light is interpreted as the
quantum state reconstruction. The efficient method based on maximum-likelihood
estimation is proposed to acquire information from registered intensity
measurements affected by noise. The connection with totally incoherent image
restoration is pointed out. The feasibility of the method is demonstrated
numerically. Spatial and correlation details significantly smaller than the
diffraction limit are revealed in the reconstructed pattern.Comment: 10 pages, 5 figure
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