91 research outputs found
Nonreciprocal Phase Gradient Metasurface: Principle and Transistor Implementation
We introduce the concept of nonreciprocal nongyrotropic phase gradient
metasurfaces. Such metasurfaces are based on bianisotropic phase shifting unit
cells, with the required nonreciprocal and nongyrotropic characteristics.
Moreover, we present a transistor-based implementation of a nonreciprocal phase
shifting subwavelength unit cell. Finally, we demonstrate the concept with a
simulation of a 6-port spatial circulator application
Transmissive Suppressed-Order Diffraction Grating (SODG)
We present a novel type of Suppressed-Order Diffraction Grating(SODG). An
SODG is a diffraction grating whose diffraction orders have all been suppressed
except one that is selected to provide electromagnetic deflection. The proposed
SODG is a transmissive grating that exhibits high-efficiency refraction-like
deflection for all angles, including large angles that are generally
challenging to achieve, while featuring a deeply subwavelength thickness, as
required in the microwave regime. We first present the design rationale and
guidelines, and next demonstrate such a 10.5 GHz SODG that reaches an
efficiency of 90% at 70 degrees
Study of the Angular Spectrum of a Bianisotropic Refractive Metasurface at a Dielectric Interface
We present an initial study of the angular spectrum of a bianisotropic
refractive metasurface at an interface between two dielectric media. In this
study, we report on the existence of three distinct angular regions: a)~a
rotated transmission cone, b)~a modified total internal reflection region, and
c)~a new total retro-reflection region
Extending the Brewster Effect to Arbitrary Angle and Polarization using Bianisotropic Metasurfaces
A bianisotropic metasurface design is proposed for extending the Brewster
effect to arbitrary angles and polarizations. The metasurface is synthesized
using the surface susceptibility tensor and Generalized Sheet Transition
Conditions (GSTCs) synthesis method, and is demonstrated by GSTC-FDFD
simulation. It is found that an extremely broad angular range (0-30) with near
zero reflection may be obtained near the normal angle, which is of paramount
interest in paraxial optics, while narrower angular range at more oblique
angles may find applications in spatial filtering
Comparison of Tensor Boundary Conditions (TBCs) with Generalized Sheet Transition Conditions (GSTCs)
This paper compares Tensor Boundary Conditions (TBCs), which were introduced
to model multilayered dielectric structures, with Generalized Sheet Transition
Conditions (GSTCs), which have been recently used to model metasurfaces. It
shows that TBCs, with their 3 scalar parameters, are equivalent to the
direct-isotropic -- cross-antiisotropic, reciprocal and nongyrotropic subset of
GSTCs, whose 16 tangential (particular case of zero normal polarizations) or 36
general susceptibility parameters can handle the most general bianisotropic
sheet structures. It further shows that extending that TBCs scalar parameters
to tensors and allowing a doubly-occurring parameter to take different values
leads to a TBCs formulation that is equivalent to the tangential GSTCs, but
without reflecting the polarization physics of sheet media, such as
metasurfaces and two-dimensional material allotropes.Comment: 6 pages, 1 figur
Synthesis of Electromagnetic Metasurfaces: Principles and Illustrations
The paper presents partial overview of the mathematical synthesis and the
physical realization of metasurfaces, and related illustrative examples. The
synthesis consists in determining the exact tensorial surface susceptibility
functions of the metasurface, based on generalized sheet transition conditions,
while the realization deals with both metallic and dielectric scattering
particle structures. The examples demonstrate the capabilities of the synthesis
and realization techniques, thereby showing the plethora of possible
metasurface field transmission and subsequent applications. The first example
is the design of two diffraction engineering birefringent metasurfaces
performing polarization beam splitting and orbital angular momentum
multiplexing, respectively. Next, we discuss the concept of the "transistor"
metasurface, which is an electromagnetic linear switch based on destructive
interferences. Then, we introduce a non-reciprocal non-gyrotropic metasurface
using a pick-up circuit radiator (PCR) architecture. Finally, the
implementation of all-dielectric metasurfaces for spatial dispersion
engineering is discussed
Generalized Brewster effect using bianisotropic metasurfaces
ABSTRACT: We show that a properly designed bianisotropic metasurface placed at the interface between two arbitrary different media, or coating a dielectric medium exposed to the air, provides Brewster (reflectionless) transmission at arbitrary angles for both the TM and TE polarizations. We present a rigorous derivation of the corresponding surface susceptibility tensors based on the generalized sheet transition conditions and demonstrate by full-wave simulations the system with planar microwave metasurfaces designed for polarization-independent and azimuth-independent operations. The proposed bianisotropic metasurfaces provide deeply subwavelength matching solutions for initially mismatched media. The reported generalized Brewster effect represents a fundamental advance in optical technology, where it may both improve the performance of conventional components and enable the development of novel devices
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