Design of an acoustic illusion device based on a shifting medium and multi-folded transformation.

An acoustic illusion device that can act as an invisible cloak or a shifting medium depending on the value of shift distance, which is about twice the circum-radius of the outer polygon, is proposed and designed based on linear coordinate transformation. A multi-folded transformation approach is used to design an illusion device with a circular opening window that allows for information interaction with the outside world. The results show that the proposed device can hide objects with arbitrary shapes or positions. Furthermore, in order to remove the material anisotropy of the proposed illusion device, a layered structure composed of homogenous and isotropic material is used based on the effective medium theory. The combination of the layered structure and the circular opening provide a flexible and feasible approach to achieve the partial implementation of the illusion device. It is hoped that these results may open an avenue for designing and implementing invisibility cloaks or illusion devices, and speed up potential applications for noise shielding, target camouflage, or target protection from active sonar signals.

Target illusion by shifting a distance.

A novel homogeneous illusion device with arbitrary polygonal cross section that acts as either invisible cloak or shifting medium has been proposed and designed based on coordinate transformation method. The material parameters of the device are derived and the effectiveness is verified by full-wave simulation. Results show that whether the illusion device acts as invisible cloak or shifting medium depends on a value of shifting distance which is about 2a (ais circum-radius of the outer polygon).When the shifting distance is larger than 2a, the illusion device acts as an invisible cloak, and otherwise it acts as shifting medium. The stealth effect of all kinds of illusion devices are investigated, including identical-size mapped polygonal devices or non-identical size mapped polygonal devices. The results show that the device is a novel interactive cloak and is different from pre-proposed cloaks. The shifting properties of the device are validated by two examples, including moving the target object virtually and generating illusionary image of a line source. The material parameters of the device are homogeneous, which makes it more practicable in reality. It is hoped that our works may open an avenue for designing novel invisible cloaks, and are helpful for speeding up the potential applications of the illusion devices, such as aircraft or military equipment stealth, target objects camouflage or protection.

Homogeneous Multifunction Devices Designing and Layered Implementing Based on Rotary Medium.

Multifunctional device with homogeneous anisotropic material parameters are proposed and designed based on linear transformation optics and rotary medium. Four examples including rotating concentrator, rotating amplifying device, rotating shrinking device and rotating transparent device are reported. All of them have bi-functional effects, i.e., they possess concentrating, amplifying, shrinking and transparent effects respectively while have the fields been rotated an angle of π/N simultaneously in common, where N is the sides number of polygon. All these devices have potential applications, such as energy accumulation or controlling, military camouflage, wireless communication system and radar/antenna protection. Furthermore, alternating isotropic layered structure based on effective medium theory is utilized to remove the anisotropic property of these devices. Simulation results show that the layered structure device behaves almost as perfect as the ideal one when it has sufficient divided layers. The feasibility of designing multifunctional device by natural isotropic materials instead of metamaterials with complicated artificial composite structure would dramatically reduce the fabrication difficulty and move the device a step further towards the practical application.

Transmission properties and molecular sensing application of CGPW.

In this paper, a cylindrical graphene plasmon waveguide (CGPW), which consists of two rolled graphene ribbons, a dielectric core and a dielectric interlayer is proposed, and its use for molecular sensing is investigated. First, an analytical model for the surface plasmon modes supported by this graphene geometry is presented and verified by finite element method simulations. Furthermore, we demonstrate a large tunability of the modes behavior by varying the Fermi level of the graphene, the coupling distance between the two sheets and the radius of the cylinder. Finally, a molecular sensing scheme based on the CGPW is proposed. Broadband spectroscopy of ethanol and toluene thin layers is realized by recording the changes in spectral intensity of the propagating mode. Due to the broadband localization capability of graphene plasmon mode which leads to a strong light-matter interaction in the midinfrared and terahertz regime, the proposed sensing scheme may provide an effective way for detecting nanometric-size molecules.

Mu and epsilon near zero metamaterials for perfect coherence and new antenna designs.

Wave interference is a fundamental physical phenomenon. Traditionally, the coherent effect of two identical point sources only takes place when the optical path is an integer number of wavelengths. In this paper, we show that mu and epsilon near zero (MENZ) metamaterials can be used to realize a perfectly constructive and isotropic interference. No matter how many point sources are embedded in the MENZ region, the wavefronts overlap perfectly. This translates into a total relaxation of the conventional condition for coherence enabled by the apparent infinite wavelength of the fields within MENZ metamaterials. Furthermore, we investigate crucial parameters such as the shape and size of the MENZ region. We demonstrate that flat sided geometries give rise to constructive interference beams serving as a powerful design mean. We also reveal the importance of relying on deeply sub-wavelength MENZ volumes as larger sizes increase the impedance and therefore reduce the output power of the device. The proposed concepts bear significance for current trends in antenna design which are inspired by the recent developments of electromagnetic metamaterials. Moreover, the perfect coherence effect can be appealing for power combiners, especially in the terahertz where sources are dim, as the irradiation intensity scales with the square of the number of embedded sources.