Dielectric Cylinder Research Articles

Super-Operator Linear Equations and Their Applications to Quantum Antennas and Quantum Light Scattering

In this paper, we develop a resolvent method for super-operator equations with applications in quantum optics. Our approach is based on the novel concept of a linear super-operator acting on the Hilbert subspace of vector or scalar linear operators satisfying physically reasonable commutation relations. The super-operator equations for the electromagnetic (EM) field operators are formulated for the problems of quantum antenna emission and quantum light scattering by a dielectric body. The general solution of super-operator equation is presented in terms of the classical resolvent. In contrast to the classical case, it includes the ancillary components associated with the quantum noise even in the absence of absorption. The reason for this lies in the energy exchange between different spatial regions with various bases for the field presentation (which looks like losses or gain from the point of view of the correspondent region). A number of examples (a two-element dipole antenna, a plane dielectric layer, and a dielectric cylinder with a circular cross section) which demonstrate the physical mechanism of the appearance of noise are considered. It is shown that antenna emission or scattering transforms the coherent properties of quantum light. This leads to a new way of controlling coherence in a direction-dependent manner, a feature that can be useful in various applications of quantum technologies, including quantum radars and lidars, and quantum antennas.

Evaluation of Electric Field for a Dielectric Cylinder Placed in Fractional Space

The problem related to the dielectric cylinder placed in non-integer dimensional space (FD space) isthoroughly investigated in this paper. The FD space describes complex phenomena of physics and electromagnetism. We have solved Laplacian equation in FD space to obtain the solution of a dielectric cylinder in low frequency. The problem is solved by the method of separation of variables analytically. The classical solution of the problem can be easily recovered from the derived solution in non-integer dimensional space.

Scattering by Arbitrary Cross-Section Cylinders Based on the T-Matrix Approach and Cylindrical to Plane Waves Transformation

Multiple scattering of parallel cylinders with arbitrary cross section is computed using the T-matrix of each single scatterer and the general translational matrix for cylindrical waves. Usually, the recommended golden rule to compute the translational matrix is Graf’s addition theorem. However, this approach cannot be properly implemented for some geometries, such as in a two-cylinder case when the center of one of them falls within the minimum circular cylinder that circumscribes the other one. In order to overcome this limitation, a transformation between cylindrical waves and plane waves, followed by propagation of the latter, is proposed. The new approach succeeds due to an adequate truncation of the evanescent plane wave spectrum. This strategy is demonstrated by studying the scattering of three infinite elliptic metallic cylinders for different electrical sizes and observing the convergence of the results as a function of the truncated spectrum. Finally, to conclusively show the interest and applicability of the approach, two more complex problems are treated: a group of infinite elliptic metallic cylinders where two different sizes are combined and a practical real-life filter in substrate integrated waveguide (SIW) technology, including several groups of rectangular dielectric cylinders.

Omnidirectional, thin metasurface exhibiting selective absorption for un-polarized broadband incidence.

Thin devices with large areas have strong and omnidirectional absorption over a wide bandwidth and are in demand for applications such as energy harvesting, structural color, and vehicle LiDAR (laser detection and ranging). Despite persistent efforts in the design and fabrication of such devices, the simultaneous realization of all these desired properties remains a challenge. In this study, a 190-nm-thick metasurface with an area of 3 cm2, incorporating dielectric cylinder arrays, a chromium layer, a silicon nitride (SiNx) layer, and an aluminum layer is theoretically and experimentally demonstrated. The developed device achieves an average absorptivity of ∼99% (97% in the experiment) in the entire visible spectrum 400-700 nm. Moreover, it exhibits strong absorption over a wide range of incident angles (∼91% and 90% at 60° in the calculation and experiment, respectively). Importantly, the feasibility of applying the developed metasurface absorber to solar thermophotovoltaics and vehicle LiDAR (laser detection and ranging) has been explored. Moreover, the photoresist can be replaced by other glues and easily scaled up to a large area using the roll-to-roll nanoimprinting process. With the excellent spectral properties and performance, this device is promising for large-area applications.

Corner states in second-order two-dimensional topological photonic crystals with reversed materials

Recently, topological corner states have been extensively investigated in second-order topological photonic crystals (STPCs). However, most square lattice STPCs are proposed based on the two-dimensional (2D) Su-Schrieffer--Heeger (SSH) model. In this work, we propose a photonic crystal (PC) that goes beyond the 2D SSH model. The unit cell (UC) of the PC is only composed of a dielectric cylinder in an air background (or an air hole in a dielectric slab). The topological trivial or nontrivial photonic band gap of the cylinder-in-air or hole-in-slab UC can be confirmed from the value of 2D polarization. Remarkably, photonic band gaps form directly without any intermediate transition. 2D bulk states, one-dimensional edge states, and zero-dimensional corner states are generated hierarchically in the box-type combination structures composed of trivial and nontrivial PCs. By comparing the perfect and defective structures, the corner states show strong robustness against the defects. The proposed configurations provide a simpler platform for exploring topological corner states in photonic systems, which have great potential for application in integrated nanophotonic devices.

Scattering of an Electromagnetic Wave by a Structure Consisting of Several Perfectly Conducting and Dielectric Finite-Length Thin Cylinders

Scattering of an Electromagnetic Wave by a Structure Consisting of Several Perfectly Conducting and Dielectric Finite-Length Thin Cylinders

WITHDRAWN: Propagation and scattering analysis of a rectangular dielectric cylinder for various incident angles

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Use of a Set of Wearable Dielectric Scatterers to Improve Electromagnetic Transmission for a Body Power Transfer System

In this paper we present an accurate analytical solution of the scattering of a plane-wave by dielectric cylinders placed above a multilayered medium. An analytical approach is used to solve the scattered field by the cylinders in each medium through expansions into cylindrical waves, expressed through plane-wave spectra. The multilayer models a biological tissue consisting of skin, fat and muscle covered by a cotton textile. Several numerical examples are presented considering the electrical parameters of the biological and textile tissues at the millimeter frequency range (24 GHz). The results show that it is possible to obtain an intensification of the electric field in the underlying tissues in case of TM polarization of the incident wave, finding an interesting application for the charging of implantable or wearable devices.

Highly-sensitive sensor based on toroidal dipole governed by bound state in the continuum in dielectric non-coaxial core-shell cylinder.

The electromagnetic fields distributed on the surface region of the nanostructure is very important to improve the performance of the sensor. Here, we proposed a highly sensitive sensor based on toroidal dipole (TD) governed by bound state in the continuum (BIC) in all-dielectric metasurface consisting of single non-coaxial core-shell cylinder nanostructure array. The excitation of TD resonance in a single nanostructure is still challenging. The designed nanostructure not only supports TD resonance in a single nanostructure but also has very high Q-factor. More importantly, its electric field distributes at the surface of outer cylinder-shell, which is very suitable for biosensing. To evaluate the sensing performance of our proposed structure, we investigated the sensitivity and the figure of merit (FOM) of nanostructure with different structural parameters. Maximum sensitivity and FOM can reach up to 342 nm/RIU and 1295 when the asymmetric parameter d =10 nm. These results are of great significance to the research of TD resonance and the development of ultrasensitive sensor.

Active Millimeter Wave Imaging Using Leaky-Wave Focusing Antenna

In this article, an active millimeter-wave imaging system using two rectangular waveguide leaky-wave focusing antennas deployed in a quasi-monostatic transmitter and receiver pair is proposed. The broadband design method of the focusing antenna is presented, where the phase constant is derived from the radiation direction of a rectangular waveguide leaky-wave antenna. To eliminate the effect of mutual coupling between the transmitting and receiving antennas and scattering from the surrounding environment, the scattered field from the object is obtained by subtracting the incident field from the total field. The 1-D detection of conducting sphere, conducting and dielectric cylinders, and a conducting plate is performed by experiment to validate the imaging capability of the proposed system. The 2-D imaging of a conducting cylinder in free space and positioned in front of a human body phantom representing the human body is finally performed to simulate the practical application of the system.

Grassmannian diffusion maps based surrogate modeling via geometric harmonics

AbstractA novel surrogate model based on the Grassmannian diffusion maps (GDMaps) and utilizing geometric harmonics (GH) is developed for predicting the response of complex physical phenomena. The method utilizes GDMaps to obtain a low‐dimensional representation of the underlying behavior of physical/mathematical systems with respect to uncertain input parameters. Using this representation, GH, an out‐of‐sample extension technique, is employed to create a global map from the input parameter space to a Grassmannian diffusion manifold. GH is further employed to locally map points on the diffusion manifold onto the tangent space of a Grassmann manifold. The exponential map is then used to project the points in the tangent space onto the Grassmann manifold, where reconstruction of the full solution is performed. The performance of the proposed surrogate model is verified with three examples. The first problem is a toy example used to illustrate the technique. In the second example, errors associated with the various mappings are assessed by studying response predictions of the electric potential of a dielectric cylinder in a homogeneous electric field. The last example applies the method for uncertainty prediction in the strain field evolution in a model amorphous material using the shear transformation zone theory of plasticity.

A wide‐angle scanning Luneburg lens antenna

The Luneburg lens is an effective way to implement multibeam antennas. However, the existing planar Luneburg lens configuration usually can only provide a relatively narrow scanning range. To deal with this problem, a Luneburg lens consisting of one dielectric cylinder and nine dielectric rings is proposed. It can be easily fabricated using low cost ABS material through 3D printing technology. The lens is placed between two metal plates which have an additional flare structure to enhance the antenna gain. To effectively excite the lens for multibeam applications, 9 magneto electric dipoles are utilized. For validation, a wide-angle scanning planar Luneburg lens antenna operating at 35 GHz was designed, fabricated and measured. A good agreement between simulation and measurement can be observed. At the center frequency, a wide scanning coverage of 172° can be obtained with a gain variation less than 1.6 dB.

Design of a lattice dielectric cylinder based on multiwalled carbon nanotube-epoxy composite for microwave absorption in the X-band

To meet the urgent electromagnetic compatibility (EMC) requirements for the electronic products, microwave absorbers with a lattice of the dielectric cylinder were investigated. The elements of the lattice have a cylindrical shape and are composites of epoxy resin filled with multi-walled carbon nanotubes (MWCNTs-EP). The relative complex permittivity of the MWCNT-EP was obtained from the S-parameters measured by the transmission-reflection method with X-band waveguide. The numerical simulation results show that the reflection coefficient of the uniform lattice of the dielectric cylinder is less than −10 dB in the entire X-band (8 GHz–12 GHz) and the reflection coefficient of the hybrid lattice of the dielectric cylinder (HLDC) is less than −15 dB in the same band. Moreover, the reflection coefficient of HLDC is less than −20 dB at normal incidence in the frequency range of 8.4 GHz–11.3 GHz. Further investigation demonstrates that the proposed HLDC could maintain good absorption performance under different incident angles and polarizations. This study suggests that HLDC with the characteristics of lightweight, excellent absorption performance, good angle, and polarization stability provide a promising prospect in the EMC field.

A graphene inspired electromagnetic superlens

In this paper we propose a new paradigm to create superlenses inspired by n–p–n junctions of graphene. We show that by adjoining an n-type region and a p-type region with a crystal dislocation, it is possible to mimic the interaction of complementary Hamiltonians and achieve subwavelength imaging. We introduce an effective model of the system, and show that it predicts perfect lensing for both propagating and evanescent waves due to the excitation of a resonant mode at the interface between each region. This phenomenon is the consequence of a nontrivial boundary condition at the n–p interfaces due to a dislocation of the graphene ‘atoms’. We discuss practical realizations of such superlenses in electronic and photonic platforms. Using full wave simulations, we study in detail the performance of a photonic realization of the lens based on a honeycomb array of dielectric cylinders embedded in a metal.

Scattering of Electromagnetic Radiation by Linear Small-Particle Aggregates of Finite Dielectric Cylinders

Scattering of Electromagnetic Radiation by Linear Small-Particle Aggregates of Finite Dielectric Cylinders

Lagrangian PAFs in multiple optical scattering by two absorptive dielectric parallel cylinders

The objective of this work is to derive semi-analytical integral expressions for the Lagrangian longitudinal (L) and transverse (T) photophoretic asymmetry factors (PAFs) for an aggregate pair of parallel absorptive dielectric cylinders of arbitrary radii in plane waves with arbitrary incidence angles and polarizations. Based on the multiple scattering theory of waves and its rigorous mathematical formalism, the components of the internal electric field vectors in cylindrical coordinates are determined and used subsequently to compute the PAFs. The L- and T-PAFs are directly proportional to the L and T components of the photophoretic (known also as radiometric) force vector, respectively, induced by light absorption inside each dielectric cylinder. The modal expansion method in cylindrical coordinates and adequate boundary matching at the surface of each particle are used to determine the internal coefficients to compute the PAFs. Subsequently, the integral expressions are derived and evaluated assuming TE- and TM-polarized plane waves with arbitrary angles in the polar plane. Additional computations for the dimensionless intensity function are performed, and the corresponding results provide quantitative assessment of the internal heated portions of the absorptive dielectric cylinders at different interparticle distances while illuminated by plane waves with variable incidence angles and polarizations. The results are of some importance in electromagnetic/optical multiple scattering theory and related applications in optical binding, optical tweezers, particle manipulation, and photophoresis.

Topological boundary states of two-dimensional restricted isosceles triangular photonic crystals.

We propose an all-media photonic crystal (PC) composed of isosceles triangle dielectric cylinders that realizes the topological phase transition by simply rotating the isosceles triangular dielectric cylinders. Additionally, the topological phase transition is closely linked with the size parameters and rotation angle of the isosceles triangle. The topological boundary states with lossless transmission are constructed on the interface of two different topological structures, and the optical quantum spin Hall effect is simulated. Further, we verified that the boundary state is unidirectional and immune to disorder, cavity, and sharp bend defects. By rotating the angle of the triangle to control the transmission path of the pseudo-spin state, we realize diverse transport pathways of light, such as the "straight line" shape, "Z" shape, "U" shape, and "Y" shape. This topological system shows a higher degree of freedom, which can promote the research on topological boundary states and the development of topological insulators in practical applications.

Optical Magnus radiation force and torque on a dielectric layered cylinder with a spinning absorptive dielectric core.

A dielectric cylindrical shell material with an inner stationary absorptive core (or, equivalently, a concentric layered cylinder) illuminated by an axisymmetric wave field (in 2D) with arbitrary polarization will experience a time-averaged radiation force along the direction of wave propagation, whereas the transverse component vanishes as required by symmetry. Counterintuitively, the present analysis shows that when the inner absorptive core material rotates with an initial angular velocity Ω0 around its main geometrical axis, a transverse radiation force component arises (in addition to a longitudinal force) as well as an axial radiation torque component in plane waves. This phenomenon is the analog of the classical hydrodynamic Magnus effect. In this analysis, the instantaneous rest-frame theory and the modal series expansion method in cylindrical coordinates are utilized to formulate the EM/optical scattering from a cylindrical shell with arbitrary thickness, and to compute the optical radiation force and torque vector components. Particular emphases are given on the size parameter of the cylindrical shell, the layer thickness, the angular rotation of the inner absorptive core, and the polarization (TM or TE) of the incident plane waves. Numerical computations illustrate the analysis and explicate the behaviors of the longitudinal, transverse, and axial radiation force and torque components. Related applications for the optical Magnus effect in radiation force and torque investigations can benefit from the results of the present analysis in spin-optics, rotational Doppler shift for optical waves, optical tweezers, optical manipulation of elongated spinning objects, and particle rotation.

Optical Magnus effect in the photophoresis of a spinning absorptive dielectric circular cylinder.

When a stationary absorptive dielectric cylinder suspended in a gas (such as air) is illuminated by an axisymmetric wave field (such as plane waves), the transverse (T) photophoretic asymmetry factor (PAF) vanishes as required by geometrical symmetry [Appl. Opt.60, 7937 (2021) APOPAI0003-693510.1364/AO.435306]. Counter-intuitively, when the cylinder possesses an initial angular velocity Ω0 with a sufficiently small acceleration and spins around its main axis in the illuminating field of axisymmetric plane waves, it is shown here that the T-PAF (which is directly proportional to the T-photophoretic force vector component) is quantifiable, in analogy with the Magnus effect in hydrodynamics where a force perpendicular to the axis of the cylinder and to the propagation direction arises. Based upon the instantaneous rest-frame theory and the partial-wave series expansion method in cylindrical coordinates, the internal electric field of the spinning absorptive dielectric cylinder is determined and utilized to compute both the longitudinal (L) and T-PAFs. Particular emphases are given on the size parameter of the cylinder, its angular rotation, the light absorption inside its core material and the polarization (TM or TE) of the incident plane waves. The dimensionless intensity function (DIF) is also computed, which reveals quantitative information on the heated portions within the internal absorptive core material of the cylinder. Numerical computations illustrate the analysis and explicate the behaviors of the DIF and the L- and T-PAFs, which predict the emergence of the forward, neutral, and reverse optical/electromagnetic Magnus effect in the photophoresis of an absorptive dielectric cylinder and related applications in spin optics, optical tweezers, optical manipulation of elongated objects, and radiative transfer research.

Dual-band all-dielectric chiral photonic crystal

We present an all-dielectric chiral photonic crystal that guides the propagation of electromagnetic waves without backscattering for dual bands. The chiral photonic crystal unit cell is composed of four dielectric cylinders with increasing inner diameter clockwise or anticlockwise, which leads to chirality. It is demonstrated that the proposed chiral photonic crystal can generate dual band gaps in the gigahertz frequency range and has two types of edge states, which is similar to topologically protected edge states. Hence, the interface formed by the proposed 2D chiral photonic crystal can guide the propagation of electromagnetic waves without backscattering, and this complete propagation is immune to defects (position disorder or frequency disorder). To illustrate the applicability of the findings in communication systems, we report a duplexer and a power divider based on the presented all-dielectric chiral photonic crystal.