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(a) Representation of the polarization beam splitter/ combiner. (b) Fabricated structure with 24 · 24 unit cells. The two polarizations are refracted in the diagonal direction where a macroscopic stripe-like pattern is apparent.
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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 meta...
Contexts in source publication
Context 1
... an example, we present the implementation of a polarization beam splitter (or, reciprocally, a polarization combiner). The corresponding metasurface, that is shown in Figure 4, is first described in terms of its surface suscep- tibilities, by inserting the specified incident, reflected and transmitted electric and magnetic fields into (4a)-(5b). Here, the reflected waves are specified to be zero and the transmit- ted waves are specified to be fully refracted at / ? ...
Context 2
... the procedure described in Section 2.2.1, each unit cell is designed separately to realize the required equiv- alent surface susceptibilities. The fabricated metasurface, shown in Figure 4b, consists in 24 · 24 unit cells. From periodicity, the unit cells can be grouped into periodic super- cells composed of 8 · 8 unit cells. ...
Context 3
... the metasurface in Figure 4b is electrically too large to be simulated, a simplified version of the metasurface is considered for the full-wave simulations. Only the first row of the 8 · 8 supercell is selected. ...
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Citations
... In the top layer, a ring graphene meta-atom is constructed on a stacked SiO 2 substrate with an air gap. The geometric parameters of the constituent meta-atom are synthesized by mapping the metasurface scattering parameters onto the tensorial surface electrical and magnetic susceptibility functions, and fine-tuned by optimization (Achouri et al. 2015). ...
... Due to the shielding effectiveness of the gold ground, the transmittance T is 0. As a result, the calculation of absorption can be simplified with A = 1 − R. Since, R = (Z in − Z 0 )/(Z in + Z 0 ), where Z in is input impedance of structure and Z 0 is the free space impedance, when Z in = Z 0 , the perfect absorption can be achieved. Therefore, the tunable chemical potential parameter of graphene can be used to change the input impedance of the metasurface and obtain absorption/reflection waves (Achouri et al. 2015). In the other words, the response of metasurface can be switched between reflection and absorption by controlling the bias voltage. ...
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... The advantages of metasurfaces over metamaterials include lower loss, lighter weight, and easier fabrication. Applications of metasurfaces include polarization transformers [7], generalized refraction [8], broadband absorbers [9], spatial waveguides [10], remotely-controlled spatial processors [11], aberration free lens [12], [13], flat optical components [14], LED efficiency enhancers [15], and spatial isolators [16]. Metasurfaces achieve these functionalities by creating discontinuities in the electromagnetic fields. ...
... where E x z + m is a function of ξ. The metasurface synthesis equations in (11) can be used to obtain expressions for ...
... This section presents simulation examples to validate FEM-GSTC in both 1D and 2D domains. The metasurface susceptibilities are synthesized by using (11). For vacuum on either side of the metasurface, the susceptibilites are obtained as ...
A modeling of metasurfaces in the finite element method (FEM) based on generalized sheet transition conditions (GSTCs) is presented. The discontinuities in electromagnetic fields across a metasurface as represented by the GSTC are modeled by assigning nodes to both sides of the metasurface. The FEM-GSTC formulation in both 1D and 2D domains is derived and implemented. The method is extended to handle more general bianistroptic metasurfaces. The formulations are validated by several illustrative examples.
... In contrast to three-dimensional metamaterials, which are encumbered by large device dimensions, high losses, and intricate fabrication [6][7][8], metasurfaces offer the benefits of compact size, seamless integration, minimal losses, and streamlined preparation processes, paving the way for wireless communication within the terahertz band [9,10]. In recent years, the metasurface composed of artificial subwavelength elements arranged in a planar array has gained significant attention as it overcomes the limitations of traditional optoelectronic devices [11][12][13][14][15]. The metasurface allows manipulation of transmitted and reflected waves by arbitrary changes in its phase, amplitude, and polarization states. ...
Drawing upon the physical phenomenon of polarization transformation, this paper proposes an ultra-broadband, high-efficiency linear polarization converter composed of a metallic grating, an L-shaped metallic patch, and a dielectric substrate. The polarization conversion properties have been scrutinized using the finite element numerical simulation software CST. The computational outcomes reveal that the polarization converter operates within the frequency range of 0.5 THz to 1.8 THz, exhibiting a relative bandwidth of 113%, a transmission coefficient exceeding 0.87, a polarization conversion efficiency approaching 100%, and a phase coverage spanning 360°. Furthermore, a Fabry-Perot interference model was established utilizing Matlab to corroborate the concurrence between the theoretical analysis and the numerical findings. The polarization converter metasurface amalgamates both phase and transmission amplitude variations to accomplish not only a two-dimensional multi-channel focusing lens operating between 1.55 THz and 1.65 THz, but also a spatial imaging capability utilizing transmission amplitude variation within the 0.5 THz to 1.15 THz range. The outcomes demonstrate that the devised metasurface is impervious to the polarization direction of the incident wave, exhibiting ultra-broadband and high transmission efficacy, thus providing novel insights for the versatility of terahertz wave polarization and phase manipulation.
... Metasurfaces (MTSs) [1][2][3][4] are thin layers of subwavelength elements employed to control wavefronts of guided waves [5][6][7][8][9][10], scattered waves (SWs) [11][12][13][14] and leaky waves (LWs) [15][16][17][18][19][20][21][22][23][24][25][26]. Due to their reduced thickness and sub-wavelength patterning, they can conveniently be described in terms of equivalent boundary conditions (BCs) of impedance type. ...
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... Metasurfaces can perform EM wave manipulations for example non-reciprocal field control, generalized refraction, and polarization transformation [65]. ...
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... Assume that the RIS-APs aided network consists of a BS, K users, L RIS-APs, where the BS is equipped with N ., L} be the index sets of users, reflecting elements, the RIS-APs, respectively. According to ref. [27], the metasurface could be engineered for the specified frequency band instead of the whole wideband. Therefore, downlink spectrum is divided into L equal-sized sub-bands and each RIS-AP is assumed to be assigned with a licensed one. ...
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... For example, it was shown that a polarization transformer and some types of absorbers could be synthesized in [21] and [22,23], respectively, by studying the polarizabilities of the constituent particles. Furthermore, electromagnetic susceptibility is often used in synthesizing metasurfaces, and in [24,25], the value of the susceptibility was introduced as a criterion for specifying the potential application of a metasurface. Moreover, that method is faster for computing the frequency responses, in comparison to both numerical methods and commercial software, as it provides information about the single particle's polarizabilities, and the interaction constants, separately. ...
In this paper, an analytical method is expanded to analyze asymmetrical metasurfaces under normal plane-wave illuminations. In our proposed method, two key factors of the polarizabilities of individual particles, and the interaction constants between them, are employed to analyze the frequency responses of some asymmetrical metasurfaces. The associated interaction constants are extracted analytically, in the general form of an asymmetrical arrangement. Our proposed semianalytical method is validated using different asymmetrical arrays of applicable structures, including plasmonic and dielectric particles, such as a gold split ring resonator and a split Si nanocone. The reflections and transmissions of these arrays are compared to the results of numerical full-wave simulations, while the applications of our suggested method, in achieving unidirectional scattering of the split Si nanocone, are also studied. This proposed method is useful in computing the effective polarizabilities of asymmetrical arrays, as it gives a comprehensive view of the metasurface. Therefore, our proposed method is a step forward in designing and synthesizing metasurfaces.
... An essential aspect of metasurface design lies in the ability to properly model such complex electromagnetic structures in order to fully exploit the large number of degrees of freedom that they provide. In the linear regime, one of the common approaches to model a metasurface is the description of its electromagnetic responses using specialized transition conditions relating the metasurface effective parameters to the fields that interacts with it [47][48][49][50][51][52][53]. The strength of such an approach is that it provides a direct connection between the desired optical transformation that the metasurface must achieve and its effective material parameters, which may themselves be connected to the shape of scattering particles. ...
We present a frequency-domain modeling technique for second-order nonlinear metasurfaces. The technique is derived from the generalized sheet transition conditions (GSTCs), which have been so far mostly used for modeling linear metasurfaces. In this work, we extend the GSTCs to include effective nonlinear polarizations. This allows retrieving the effective nonlinear susceptibilities of a given metasurface and predict its nonlinear scattering responses under arbitrary illumination conditions. We apply this modeling technique to the case of metasurfaces made of a periodic arrangement of T-shaped gold nanoparticles. For verification, several metasurfaces are fabricated and a fair agreement is found when comparing simulated data and experimental results. The proposed model may thus serve as a design platform to implement complex nonlinear metasurface based applications.
... By reducing the number of independent susceptibility components, the number of transformations can be decreased [48]. GSTCs offer a very powerful tool to analyze a vast array of metasurface applications, including birefringent transformations [49], [50], bianisotropic refraction [51], light emission enhancement [52], nonreciprocal nongyrotropic isolators [53] and non linear second-harmonic generation [54], remote spatial processing [55], radiation pressure control [56] and dielectric metasurfaces for dispersion engineering [57]. ...
Precision in optics has always been a challenge, which has persistently demanding new methods of design. Achieving a high performance imaging system with a compact form factor such as AR/VR displays, cameras and microscopes requires extra degrees of freedom. Recently, emerging science like freeform conformal meta-optics, which is an integrated technology of metamaterials combined with freeform optical surface profiles, offers lighter, simple and more compact assemblies. We propose a new inverse synthesis method based on the Dirac distribution of the E-M fields at an arbitrary interface and come up with with an extension of the Generalized Sheet Transition Conditions (GSTCs) valid for any arbitrary surface which we called Conformal-GSTCs (or C-GSTCs in short). We model the CGSTCs using a three dimensional FDTD method and demonstrate the validity of our modelling technique by numerically implementing the scheme for optical devices such as lenses and deflectors using home made parallel FDTD codes. We have used our numerical simulations to study the effect of the shape of the metasurface interface on the performances of metalenses. These performances were numerically characterized using standard methods of optics such as the Full Wave at Half Maximum (FWHM), Point Spread Function (PSF) or optical aberrations calculation through Zernike polynomial analysis. Our numerical implementation can serve as a tool to design freeform meta-optics, and can help in evaluating and optimizing the optical response of complex freeform optical assemblies.On the other direction, we have come up with certain characterization techniques to measure the phase data experimentally by using an in-house experimental set up. The measured phase data is processed for the evaluation of the susceptibilities. The transmitted field data arising from the metaoptical devices are computed numerically using Fourier beam propagation methods with the help of measured susceptibilities. Finally, the performance of the optical devices such as metalenses and deflectors are studied and reported. This technique could help in characterizing optical devices without the need of much complicated tools & devices in experimental labs, which could save a huge amount of resources.We have developed a full vectorial mesoscopic model to investigate the light-metasurface interaction. In this method, we obtain the distributed form of the susceptibilities from the geometric design of the metasurface by the lattice representation of nano-antennas, an approach which is similar to the concept of solid state physics. We obtain an analytical expression for the propagation of the field through the metasurface by solving Maxwell's equations for a given susceptibility function. We prove that the transmitted co-polarized beam alone acquires a global phase associated with the antenna response. Contrarily to the co-polarization beam, the transmitted cross-polarized beam is influenced by both PB and propagation phases. We extend this phase phenomenon to a general situation by decomposing the arbitrary polarization of a normally incident light in circular basis, showing that each eigenstate acquires an opposite extra phase delay due to the topological phase retardation associated with the PB phase. The diffractive properties of topological phase gradient metasurfaces are analyzed in depth via the analytical derivations, and the results are verified with optical measurements. The other physical mechanisms such as the universal principles of co-polarization and cross-polarization transmission, and the coexistence of the zero and nonzero phase gradient leading to the ordinary and generalized Snell’s law, are illustrated using the present framework. Our model an initiative to develop an intuitive understanding of topological and functional beam splitters for future applications in quantum optics and quantum information protocols.
