47 research outputs found
Exact off-resonance near fields of small-size extended hemielliptic 2-D lenses illuminated by plane waves
The near fields of small-size extended hemielliptic lenses made of rexolite
and isotropic quartz and illuminated by E- and H-polarized plane waves are
studied. Variations in the focal domain size, shape, and location are presented
versus the angle of incidence of the incoming wave. The problem is solved
numerically in a two-dimensional formulation. The accuracy of results is
guaranteed by using a highly efficient numerical algorithm based on the
combination of the Muller boundary integral equations, the method of analytical
regularization, and the trigonometric Galerkin discretization scheme. The
analysis fully accounts for the finite size of the lens as well as its
curvature and thus can be considered as a reference solution for other
electromagnetic solvers. Moreover, the trusted description of the focusing
ability of a finite-size hemielliptic lens can be useful in the design of
antenna receivers.Comment: 7 pages, 7 figure
Performance of hemielliptic dielectric lens antennas with optimal edge illumination
The role of edge illumination in the performance of compact-size dielectric
lens antennas (DLAs) is studied in accurate manner using a highly efficient
algorithm based on the combination of the Muller boundary integral equations
and the method of analytical regularization. The analysis accounts for the
finite size of the lens and directive nature of the primary feed placed close
to the center of the lens base. The problem is solved in a two-dimensional
formulation for both E- and H-polarizations. It is found that away from
internal resonances that spoil the radiation characteristics of DLAs made of
dense materials, the edge illumination has primary importance. The proper
choice of this parameter helps maximize DLA directivity, and its optimal value
depends on the lens material and feed polarization. Index Terms: Beam
collimation, dielectric lens antenna, directivity improvement, edge
illumination, edge taper, hemielliptic lens.Comment: 5 pages, 9 figure
Whispering-gallery and Luneburg-lens effects in a beam-fed circularly-layered dielectric cylinder
The whispering-gallery mode (WGM) excitation and Luneburg lens (LL) effect
are studied for a lossy circularly-layered dielectric cylinder illuminated by a
beam field. The latter is simulated by the Complex Source-Point (CSP) beam.
Exact series solution to the wave scattering problem is used to obtain the
far-field patterns and directivity. The WG mode effect is shown to undermine
the LL performance. Index Terms: Layered circular dielectric cylinder, Complex
source point beam, Whispering-gallery modes, Luneburg lens.Comment: 5 pages, 7 figure
Optical and modal features of hemielliptic dielectric lenses
Any dielectric lens has a finite closed boundary and therefore is, in fact,
an open dielectric resonator capable of supporting resonant modes whose
Q-factor depends of the lens parameters (size, shape, and material). The
hemielliptic lens, that is an essential building block of many mm-wave and THz
antennas, is not an exception: it supports the so-called halfbowtie (HBT)
resonances that can strongly affect performance of such antennas. In this paper
we illustrate the interplay between the optical and modal features in the
electromagnetic behaviour of hemielliptic lenses and highlight the drastic
influence of the HBT resonances on radiation characteristics of lens antennas.
We also discuss the difficulties associated with accurate description of the
resonant phenomena in compact-size hemielliptic lenses with conventional
techniques and provide recommendations on how to minimize the parasitic impact
of HBT resonances on the antenna performance.Comment: 5 pages 6 figure
Topological engineering of interfacial optical Tamm states for highly-sensitive near-singular-phase optical detection
We developed planar multilayered photonic-plasmonic structures, which support
topologically protected optical states on the interface between metal and
dielectric materials, known as optical Tamm states. Coupling of incident light
to the Tamm states can result in perfect absorption within one of several
narrow frequency bands, which is accompanied by a singular behavior of the
phase of electromagnetic field. In the case of near-perfect absorptance, very
fast local variation of the phase can still be engineered. In this work, we
theoretically and experimentally demonstrate how these drastic phase changes
can improve sensitivity of optical sensors. A planar Tamm absorber was
fabricated and used to demonstrate remote near-singular-phase temperature
sensing with an over an order of magnitude improvement in sensor sensitivity
and over two orders of magnitude improvement in the figure of merit over the
standard approach of measuring shifts of resonant features in the reflectance
spectra of the same absorber. Our experimentally demonstrated
phase-to-amplitude detection sensitivity improvement nearly doubles that of
state-of-the-art nano-patterned plasmonic singular-phase detectors, with
further improvements possible via more precise fabrication. Tamm perfect
absorbers form the basis for robust planar sensing platforms with tunable
spectral characteristics, which do not rely on low-throughput nano-patterning
techniques.Comment: 31 pages; 6 main text figures and 10 supplementary figure