Saeid Jamilan

Bio: Saeid Jamilan is an academic researcher from Michigan Technological University. The author has contributed to research in topics: Photonic crystal & Transformation optics. The author has an hindex of 6, co-authored 19 publications receiving 103 citations. Previous affiliations of Saeid Jamilan include Urmia University.

Superluminal media formed by photonic crystals for transformation optics-based invisibility cloaks

Abstract: We have developed an approach to building superluminal medium for transformation optics‐based devices, including invisibility cloaks, from photonic crystals. Analysis of dispersion diagrams of 2D arrays composed from dielectric rods has shown that at frequencies corresponding to the second bands formed due to bandgap opening at increase of rod permittivity, the medium formed by arrays exhibits refractive indices providing for superluminal phase velocities of propagating waves. It is further demonstrated that rod arrays with various lattice constants could be used for realizing a range of superluminal index values prescribed by transformation optics for cylindrical cloaks at arbitrary chosen operating frequency. The performed studies allowed for solving a row of problems with employment rod arrays in the cloak medium: in particular, formulating transformation optics‐based prescriptions for refractive index dispersion in the cloaking shell, defining the dimensions of array fragments capable of responding similar to infinite arrays, finding optimal distribution of linear arrays sets at their coiling to form concentric material layers in the cloaking shell, and employing interaction between neighboring array sets with various lattice constants to assist the realization of prescribed index dispersion. The performance of the superluminal medium formed by rod array sets was demonstrated on an example of a cloaking shell developed for microwave frequency range. In contrast to metamaterial-based cloak media, the developed media requires neither material homogenization, nor obtaining the effective parameters with peculiar values and Lorentz's type resonances in rods. Combination of these advantages and low losses makes photonic crystals perspective materials for invisibility cloaks operating in THz and optical ranges.

A Directivity-Band-Dependent Triple-Band and Wideband Dual-Polarized Monopole Antenna Loaded with a Via-Free CRLH Unit Cell

Abstract: A printed triple-band and wideband dual-polarized meander-line monopole antenna with a single CRLH metamaterial loading is presented. The metamaterial loading improves the impedance matching and causes the proposed antenna to radiate at multiple frequency bands with extended bandwidth. We have designed a via-free version of the CRLH transmission line unit cell which simplifies the fabrication process and decreases the costs. The antenna’s $E$ -field radiation has $y$ -directed polarization at first and third resonance bands and $x$ -directed polarization at second resonance band. In addition, proposed antenna has $z$ -directed, $y$ -directed, and $x$ -directed main radiation directions at first, second, and third resonance bands, respectively. A fabricated prototype has small dimensions of the $30~\hbox{mm}\times 30~\hbox{mm}\times 1.6~\hbox{mm}$ , and exhibits good agreement between the measurements and simulations.

A Compact Multiband Printed Dipole Antenna Loaded With Two Unequal Parallel NRI-TL Metamaterial Unit Cells

Abstract: A negative-refractive-index transmission-line (NRI-TL) metamaterial-loaded dipole antenna is proposed, which has a fully printed configuration and exhibits multiband performance. The antenna consists of a conventional dipole antenna loaded with two unequal parallel NRI-TL metamaterial unit cells which have the same electrical length, but each is loaded with a thin inductive strip that has a different length and therefore a different effective shunt inductance. An equivalent circuit is extracted to investigate the performance of the proposed metamaterial-loaded dipole antenna by modeling each of the dipole arms as a transmission line. This circuit is then used to verify that the resonant behavior of the proposed antenna can be altered by simply adjusting the lengths of the thin inductive strips. A fabricated prototype has compact dimensions of $40 \mathrm{mm} \times 10 \mathrm{mm}\times 1.6 \mathrm{mm}$ , and exhibits good agreement between the measured and simulated results.

Design and Characterization of a Dual-Band Metamaterial Absorber Based on Destructive Interferences

Abstract: We present the design, characterization, and experimental veriflcation of a dual-band metamaterial absorber (MA) in the microwave frequencies. The proposed MA consists of a metallic gammadion-shaped structure and a complete metal layer, separated by a dielectric spacer. The results show that the proposed MA has two absorption peaks at nearly 5.6GHz and 6GHz with absorption rates of 97% and 99%, respectively. The interference theory is used to investigate the physical mechanism of the proposed MA. The experimental results are in good agreement with the theoretical predictions. Furthermore, it is verifled by simulations that the absorption of the proposed MA is almost insensitive to the incident wave polarization and oblique incident angle for the both TM and TE modes. This MA has broad prospect of potential applications.

Specifics of scattering and radiation from sparse and dense dielectric meta-surfaces

Abstract: Metasurfaces composed of nanosized silicon particles are considered prospective low-loss media for future planar devices with subwavelength thickness, capable of realizing many optical functionalities, including beam steering, focusing, and holography. Previous studies revealed an opportunity to provide directional scattering from silicon metasurfaces at Kerker’s conditions and projected obtaining significantly enhanced intensity of scattering at overlapping of dipolar magnetic and electric resonances in particles at their specific geometries. Although silicon metasurfaces are usually represented by dense arrays, interactions between resonators are often neglected in their analysis, which typically uses metamaterial concepts, assuming that responses of arrays can be represented by responses of single “meta-atoms.” In this work, we investigate cooperative resonance phenomena in dielectric metasurfaces, including interactions between electric and magnetic resonances within single particles and inter-resonator interactions in arrays. First, we analyze the transformation of the responses of single resonators, when their shape changes from a sphere to a cylinder, and then to a disk, and, in particular, describe the specifics of the formation of electric and magnetic dipole modes at a coincidence of resonances. Then, phenomena in arrays are considered, including the effects of arraying on resonator responses and the effects of packing density on metasurface responses. We demonstrate that dense packing causes strong changes of resonances, transverse coupling, and integration of resonance fields, affecting scattering and radiation from metasurfaces. The obtained results are important for understanding the complexity of responses of dielectric metasurfaces and provide guidance for their design and for scattering and radiation control.Metasurfaces composed of nanosized silicon particles are considered prospective low-loss media for future planar devices with subwavelength thickness, capable of realizing many optical functionalities, including beam steering, focusing, and holography. Previous studies revealed an opportunity to provide directional scattering from silicon metasurfaces at Kerker’s conditions and projected obtaining significantly enhanced intensity of scattering at overlapping of dipolar magnetic and electric resonances in particles at their specific geometries. Although silicon metasurfaces are usually represented by dense arrays, interactions between resonators are often neglected in their analysis, which typically uses metamaterial concepts, assuming that responses of arrays can be represented by responses of single “meta-atoms.” In this work, we investigate cooperative resonance phenomena in dielectric metasurfaces, including interactions between electric and magnetic resonances within single particles and inter-resonat...

Surface Impedance Modeling of All-Dielectric Metasurfaces

Abstract: We develop a simple and reliable analytical model that allows describing the electromagnetic response of all-dielectric metasurfaces consisting of a single-layer array of high-permittivity spherical particles. By combining Mie theory with a bi-dimensional homogenization approach, we derive closed-form expressions of the electric and magnetic surface impedances exhibited by the metasurface and, thus, its reflection and transmission coefficients. The effectiveness of the proposed approach is validated through a set of full-wave simulations. The availability of the analytical model here developed allows a more in-depth understanding of the complex scattering response of these electromagnetic structures and enables the design of innovative devices operating throughout the whole electromagnetic spectrum, including, for example, unconventional reflectors for antennas, broadband optical mirrors, and highly efficient nanoantenna reflectarrays.

Dual resonance shorted stub circular rings metamaterial absorber

Abstract: In this research work, the design characterization of metamaterial absorber (MMA) has been analysed for a unit cell structure of shorted stubs circular rings metamaterial absorber. The simulated results show that dual resonance peaks occur at 17 GHz and 18 GHz with absorbance peak response of 99.99% and 99.83%, almost unity absorbance. The corresponding full width at half maximum (FWHM) bandwidth at these resonant frequencies are 4.90% and 5.07% respectively. A parametric study has been done to analysed the effect of variation of circular ring radius, shorted stubs length and rectangular bar length upon the resonance frequency. The analysis shows that we can achieve a lower resonant frequency with almost unity absorbance. Moreover, the resonant frequency drifts to lower value without affecting absorbance. The effect at oblique angle of incidence and polarization sensitivity is also considered for both TE and TM modes. So, this unit cell structure acts as a controllable and tunable MMA structure. The dual resonances MMA structure are becoming a prime technology for many present and future wireless communication systems such as radar cross section (RCS) reduction for stealth technology, satellite navigation systems, radar frequency identification and wireless handheld devices.

Reconfigurable microwave SIW sensor based on PBG structure for high accuracy permittivity characterization of industrial liquids

Abstract: In this paper, we present a novel tunable microwave sensor for permittivity determination of industrial liquids. The proposed sensor is cavity based which is developed on a Substrate Integrated Waveguide (SIW). To enhance the characterization accuracy, the reconfigurable sensor is equipped with a Photonic Band Gap method and variable capacitors. Moreover, we employ the cavity perturbation technique in order to calculate the permittivity. In the characterization process, we obtain the permittivity of an unknown material by considering a resonant frequency shift. In fact, a capacitance is the main parameter for controlling the sensor resonance. We herein change this capacitance via reconfigurable SIW cavity and applying different materials. The proposed tunable architecture lets us study the material characteristic in the wider frequency range. The structure is designed in 5–6 GHz in order to determine the electromagnetic behavior of a brand new and used transformer oil samples. The results present a highly accurate permittivity of these oil samples. Hence, the proposed method and setup is not only suitable for oil ageing programs, but also applicable for other industrial liquid applications.

Dual-band planar antenna loaded with CRLH unit cell for WLAN/WiMAX application

Abstract: A dual-band planar antenna based on composite right and left handed (CRLH) metamaterial is presented. The proposed antenna is comprised of a host folded planar monopole antenna and a CRLH transmission line unit cell. Due to another resonance frequency generated from the loaded CRLH unit cell, the presented antenna is actually a planar antenna with dual resonance bands at the centre frequency of 2.50 and 5.80 GHz, respectively, which can be regulated independently. The developed antenna also has different polarisations, the linear polarisation at the lower band and the circular polarisation at the upper resonance band. Rather than the complicated structure as before, this antenna is fabricated easily for the simple configuration without holes and the interdigital capacitances. The results of this study show that the reflection coefficient and radiation pattern have a good agreement between the simulation and measurement, the simulated relative bandwidth is 22.8% (2.22–2.79 GHz) and 10.8% (5.42–6.04 GHz), which meet the Wi-Fi/Worldwide Interoperability for Microwave Access (WiMAX) specification very well.