scholarly journals Broadband corner cloak using a uniaxial transformation medium of stacked artificial dielectric sheets

2020 ◽  
Vol 7 ◽  
pp. 4
Author(s):  
Yuma Takano ◽  
Atsushi Sanada
Keyword(s):  
Cross Sections ◽  
Near Field ◽  
Field Measurements ◽  
Corner Reflector ◽  
Specular Scattering ◽  
Transformation Medium ◽  
Field Distributions ◽  
Artificial Dielectric ◽  
Measured Field ◽  
Original Area

We demonstrate corner cloak operations mimicking a corner reflector and hiding objects in a truncated corner. The corner cloak is designed at 18.25 GHz and implemented by nonresonant artificial dielectric sheets stacked onto the bottom hypotenuse. It is shown by the near-field measurements that the measured field distributions for the cloak agree well with those for the original area of the corner reflector as well as those for the numerical prediction. The bistatic radar cross-sections (BRCSs) for the cloak and the original area calculated from the measured field distributions coincide with each other and the cloak operation is quantitatively confirmed. The bandwidth evaluated by the specular scattering angles from the BRCSs shows broadband operation as wide as from 16 to 22 GHz.

scholarly journals High-Q dark hyperbolic phonon-polaritons in hexagonal boron nitride nanostructures

Nanophotonics ◽  
2020 ◽  
Vol 9 (6) ◽  
pp. 1457-1467 ◽  
Author(s):  
Georg Ramer ◽  
Mohit Tuteja ◽  
Joseph R. Matson ◽  
Marcelo Davanco ◽  
Thomas G. Folland ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Cross Sections ◽  
Hexagonal Boron Nitride ◽  
Near Field ◽  
High Q ◽  
Surface Phonon Polaritons ◽  
Previous Hypothesis ◽  
Phonon Polaritons ◽  
Field Reflectance ◽  
Strong Confinement

AbstractThe anisotropy of hexagonal boron nitride (hBN) gives rise to hyperbolic phonon-polaritons (HPhPs), notable for their volumetric frequency-dependent propagation and strong confinement. For frustum (truncated nanocone) structures, theory predicts five, high-order HPhPs, sets, but only one set was observed previously with far-field reflectance and scattering-type scanning near-field optical microscopy. In contrast, the photothermal induced resonance (PTIR) technique has recently permitted sampling of the full HPhP dispersion and observing such elusive predicted modes; however, the mechanism underlying PTIR sensitivity to these weakly-scattering modes, while critical to their understanding, has not yet been clarified. Here, by comparing conventional contact- and newly developed tapping-mode PTIR, we show that the PTIR sensitivity to those weakly-scattering, high-Q (up to ≈280) modes is, contrary to a previous hypothesis, unrelated to the probe operation (contact or tapping) and is instead linked to PTIR ability to detect tip-launched dark, volumetrically-confined polaritons, rather than nanostructure-launched HPhPs modes observed by other techniques. Furthermore, we show that in contrast with plasmons and surface phonon-polaritons, whose Q-factors and optical cross-sections are typically degraded by the proximity of other nanostructures, the high-Q HPhP resonances are preserved even in high-density hBN frustum arrays, which is useful in sensing and quantum emission applications.

scholarly journals Efficient Planar Near-field Measurements for Radiation Pattern Evaluation by a Warping Strategy

IEEE Access ◽  
2021 ◽  
pp. 1-1
Author(s):  
Maria Antonia Maisto ◽  
Giovanni Leone ◽  
Adriana Brancaccio ◽  
Raffaele Solimene
Keyword(s):  
Radiation Pattern ◽  
Near Field ◽  
Field Measurements

Atomic 2D electric field imaging of a Yagi–Uda antenna near-field using a portable Rydberg-atom probe and measurement instrument

2020 ◽  
Vol 9 (5) ◽  
pp. 305-312
Author(s):  
Ryan Cardman ◽  
Luís F. Gonçalves ◽  
Rachel E. Sapiro ◽  
Georg Raithel ◽  
David A. Anderson
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Field Measurement ◽  
Near Field ◽  
Measurement Instrument ◽  
Rydberg Atom ◽  
Field Measurements ◽  
Atom Probe ◽  
Electric Field Measurement ◽  
Measurement Uncertainties

AbstractWe present electric field measurements and imaging of a Yagi–Uda antenna near-field using a Rydberg atom–based radio frequency electric field measurement instrument. The instrument uses electromagnetically induced transparency with Rydberg states of cesium atoms in a room-temperature vapor and off-resonant RF-field–induced Rydberg-level shifts for optical SI-traceable measurements of RF electric fields over a wide amplitude and frequency range. The electric field along the antenna boresight is measured using the atomic probe at a spatial resolution of ${\lambda }_{RF}/2$ with electric field measurement uncertainties below 5.5%, an improvement to RF measurement uncertainties provided by existing antenna standards.

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