Mohammad Mehdi Sadeghi

Bio: Mohammad Mehdi Sadeghi is an academic researcher from Jahrom University. The author has contributed to research in topics: Metamaterial & Isotropy. The author has an hindex of 1, co-authored 2 publications receiving 3 citations.

Illusion Properties in Perfect Cylindrical Devices

Abstract: In this paper, illusion properties in a class of perfect cylindrical devices that contain a singular radial mapping have been reported. In these media, illusion can be implemented using alternating structure of only two kinds of metamaterial: zero index metamaterials and perfect electric conductors. Full-wave simulations in two dimensions have been performed to verify its functionality and its illusionary effects for TM polarization incident wave. The duality principle can be applied for TE polarization.

Designing Electromagnetic Field Rotators with Homogenous and Isotropic Materials

Abstract: This paper reports the design features of an electromagnetic device with an improved mapping transformation function allowing perfect electromagnetic rotation. Based on transformation optics theory, theoretical analysis has been used to show the constitutive parameters of both unimproved and improved perfect case which has ultimately validated via full-wave simulations. For implementation of this device, an alternating structure of zero-index metamaterials and perfect electric conductors has been used. The functionality of the proposed structure was verified by numerical simulations.

Optical Null Medium: Experimental Verification of Super Scatterer in Broadband Continues Frequencies

Abstract: We experimentally show the results of the super scatterer designed by the transformation optics (TO) technique. The coordinate transformation maps a finite region in physical space to a zero thickness in virtual space, yielding extreme material properties called optical null media (ONM). As a result, an object placed inside the core media will look larger from an outside observer. ONM media is realized using metaldielectric layered structures in cylindrical coordinates. Closed form solutions for the scattering field from a cylindrical object is given in detail. ONM media is realized using air and iron layers in cylindrical layers using effective medium theory. We experimentally fabricate the ONM and show the super scattering effect using the ONM. For achieving super scattering validation, a metal pipe has been inserted into the center of the core medium made of Plexiglas and surrounded by ONM. Keyword: experimental illusion perception, optical null medium, transformation optics, slit array, scattering theory. 1Introduction Relying on the form invariance of Maxwell's equations, transformation optics (TO) provides a methodology to control and manipulate the electromagnetic waves in order to design novel devices such as invisibility cloaks, optical black holes, negative index lenses, concentrators, rotators, PEC reshaper, super scatterer, reflectionless waveguide bends, waveguide miniaturization including many other devices. These devices, typically, are restricted by their anisotropic characteristics, narrow bandwidth, and high losses associated with resonant metamaterial elements. With the advance in metamaterial technology, however, some of these difficulties can be elevated, and these devices can be realized with increased capabilities. One media that has recently attracted great attention is the optical null media (ONM). ONM media can be derived by transforming zero thickness into a finite region. As a result, the derived transformation media has extreme material properties (i.e., [ε] = {∞, 0,0}ONM has two important characteristics. First, phase accumulation inside the transformation media is zero; thus, ONM effectively nullifies the occupying space. Second, the wave propagation is limited to one particular direction only. The latter is particularly used to realize interesting surface transformation devices. Many useful devices have been designed using ONM, including hyper-lens, magnetic hoses, and field concentrators. Metal-dielectric layered structures have been extensively used to realize anisotropic effective material properties. By properly arranging the ratio of metallic and dielectric layer thickness, extreme material properties can be derived, such as ONM. In this paper, we design a super scatterer device using the TO approach. In the coordinate transformation, zero thickness in the virtual space is mapped to a finite thickness in physical space, yielding extreme material properties. Any object that is placed inside the core region of the transformation device will look like a larger from an outside observer. We provide analytical calculations for the scattered field and show the equivalence between the original and equivalent problems. ONM is realized using air and iron metal layers in cylindrical coordinates. We show that the proposed structure approximates the effective medium parameters closely. We have also experimentally fabricated the transformation media and showed the superscatterer effect. The proposed device is realized using isotropic air and iron to realize ONM and does not require resonant metamaterial structures. As a result, the super scattering effect is not limited to a narrow frequency band. 2Super scattering effects of ONM in wave expansion form solution At first, we study CPs and functionalities of ONM. To design a cylindrical ONM using TO we must provide transformation relation between real space and virtual space with an extreme extension in one or more coordinate. Here we use radial extension in cylindrical coordinates as shown in Fig.1a and 1b with following radial transformation function, Figure 1. (a) and (b) show the transformation relation between virtual space and real space, respectively. (c) numerical simulation of energy density of gaussian beam in 2D ONM. r = { R2−∆ R2−δ r r ∈ [0,R1), we name this region core medium ∆ δ r − ( ∆ δ − 1)R2 r ∈ [R1, R2], we name thisregion shell medium r r ∈ (R2, ∞], out side of device (1) Where r and r represent virtual and real space, respectively. In this relation δ, a very thin region (a region between cylinders with radiuses R2 − δ and R2) extremely extended to a finite region, ∆= R2 − R1. The CPs of such an ONM can be calculated by TO, For r ∈ [0,R1) , ε = μ = diag (1,1, ( R2−δ R2−∆ ) 2 ) δ→0 ⇒ diag (1,1, ( R2 R1 ) 2 ) (2) And for r ∈ [R1,R2], ε = μ = diag (P, 1 P , ( δ ∆ ) 2 P) δ→0 ⇒ diag(∞, 0,0) (3) Where P = 1 + ( ∆ δ + 1) R2 r . Eq. (2) and (3) show that this extension resulted in a CP with extreme large value along radial direction and nearly zero in other directions. If we consider the relation, kr 2

Radar Cross Section Approach in Illusion Effects of Transformation Optics-Based Expander

Abstract: In this paper, analytical calculation has been provided to show illusion perception in electromagnetics expander. For this end, a precise analytical solution has been done for a scattered wave from the expander including an object in the core medium. Also, this analytical calculation has been done for a bare transformed object with different size and constitute parameters (CPs). Illusion perception, in the far field, can be illustrated by comparing the calculated scattered field patterns (SFP) of the object placed inside the expander with SFP of the bare transformed object. Moreover, the same calculation and comparison has been done for nearfield SFP. In continuation, for precise deduction, radar cross sections (RCSs) of both objects have been calculated and plotted using MATLAB. Well functionality in illusion perception has been obtained using comparisons in both analytical SFPs parts and RCSs parts.

Experimental Verification of Illusion Optics with Optical Null Media

Abstract: We experimentally show the results of the illusion device designed by the transformation optics (TO) technique. The coordinate transformation maps a zero thickness in virtual space to a finite region in physical space, yielding extreme material properties called optical null media (ONM). As a result, an object placed inside the core media will look larger to an outside observer. ONM media is realized using metaldielectric layered structures in cylindrical coordinates. Also closed-form solutions for the scattering field from a cylindrical object are given in detail to prove illusion effect analytically. ONM media is realized using air and iron sheets in radial structure using effective medium theory. We experimentally fabricate the ONM and show the scattering effect using the ONM. For achieving illusion validation, a metallic pipe has been inserted into the center of the core medium made of Plexiglas and surrounded by ONM. Keyword: Experimental Illusion Perception, Optical Null Medium, Transformation Optics Theory, Slit Array, Scattering Theory. 1Introduction Relying on the form invariance of Maxwell's equations [1-3], transformation optics (TO) [4-7] provides a methodology to control and manipulate the electromagnetic waves in order to design novel devices such as invisibility cloaks [4,5,8-10], optical black holes [11-15], negative index lenses [6,7,16-18], concentrators [19,20], rotators [21-25], PEC reshaper [26,27], super scatterer [28-31], reflectionless waveguide bends [32,33], waveguide miniaturization [34,35] including many other devices. These devices, typically, are restricted by their anisotropic characteristics, narrow bandwidth, and high losses associated with resonant metamaterial elements. With the advance in metamaterial technology, however, some of these difficulties can be elevated, and these devices can be realized with increased capabilities [36-41]. One media that has recently attracted great attention is the optical null media (ONM) [42-45]. ONM media can be derived by transforming zero thickness into a finite region. As a result, the derived transformation media has extreme anisotropic material properties (i.e., [ε], [μ] = {∞, 0,0}). ONM has two important characteristics. First, phase accumulation inside the transformation media is zero; thus, ONM nullifies the occupying space. Second, the wave propagation is limited to one particular direction only. These properties are particularly used to realize interesting surface transformation devices [46,47]. Many useful devices have been designed using ONM, including hyper-lens [48], magnetic hoses [49], and field concentrators [50]. Such anisotropic material properties can be realized using metal-dielectric layered structures [51-52]. Extreme material properties, for instance, ONM, can be obtained by appropriately arranging the ratio of metallic and dielectric layer thickness. In this paper, we design an illusion optics device using the TO approach. In the coordinate transformation, zero thickness in the virtual space is mapped to a finite thickness in physical space, yielding extreme material properties. Any object placed inside the transformation device's core region will look larger from an outside observer. We provide analytical calculations for the scattered field and show the equivalence between the original and equivalent problems. ONM is realized using air and iron metal layers in cylindrical coordinates. We show that the proposed structure approximates the effective medium parameters closely. We have also experimentally fabricated the transformation media and showed the illusion effect. The proposed device is realized using isotropic air and iron to realize ONM and does not require resonant metamaterial structures. 2Optical Null Media for Illusion Optics Here, we first study the derivation of the ONM media. Fig. 1(a,b) shows the virtual and physical space, respectively, where almost zero thickness region (δ) in virtual space is mapped to a finite thickness (∆) in physical space. The corresponding coordinate transformation from physical space to virtual space is given in Eq. (1).