Full wave finite-difference time-domain study of lossless acoustic bipolar cylindrical cloak with compressed geometry and complementary media

Abstract

Full-wave finite-difference time-domain analysis of a lossless acoustic cloak with complementary media is studied for bipolar cylindrical geometry. The material parameters for the acoustic cloak are obtained by comparing two-dimensional Maxwell's equations in the transverse magnetic polarization and acoustic field equations for general curvilinear coordinates. The permittivity and permeability tensors for the corresponding electromagnetic fields are then obtained by using an effective medium approach in general relativity. The complementary media cancels the phase vectors across the boundaries of the illuminated acoustic waves. It is shown that for the lossless cloak the broadband and illumination direction independent cloaking can be achieved with the proposed structure.

Lossless acoustic half-bipolar cylindrical cloak with negative-index metamaterial

“…It was shown that, for the lossless acoustic cloak, the illumination-direction-independent cloaking can be achieved using the structure with the compressed geometry and complementary media. 15) We extend our previous results for the lossless full-bipolar cylindrical cloak to the half-bipolar cylindrical cloak where the cloaking shell covers only the upper structure and the bottom of the cloak is exposed without the cloaking shell. In this work, the region σ 1 < σ < π, which would have been filled with the RG in the ordinary half-bipolar cylindrical cloak shown in Fig.…”

“…where is the fluid bulk modulus. By comparing with Maxwell's equations for TM polarizations ðE 1 ; E 2 ; H z Þ, we obtain material parameters for the acoustic cloak by the variable change 15) ½ p; v 1 ; v 2 ; 1 ; 2 ; À1 $ ½H z ; E 2 À E 1 ; " 2 ; " 1 ; z : ð2Þ…”

“…To implement the twodimensional FDTD method, we transform the constitutive parameters (3) obtained for the bipolar cylindrical coordinates into the constitutive tensors in the Cartesian coordinates using the unitary transformations (Appendix B). 9) Recently, we have considered a full-bipolar acoustic cloak 15) containing both the conventional cloaking shell, which compresses the inner structure into a line segment, and the complementary media 9,12,21) containing the negative-index material. The negative acoustic metamaterial has been studied both theoretically 22) and experimentally.…”

“…8,9) Moreover, there have been studies of electromagnetic cloaks with partially enclosed cloaking structures. [10][11][12][13][14] Previously, we studied 15) a lossless acoustic cloak using the analogy of acoustic equations and TM polarizations of electromagnetic field equations, and showed that the acoustic cloak with both the cloaking shell and complementary media shows illumination-direction-independent cloaking performance. The material properties for the acoustic cloak were obtained by comparing 2D Maxwell's equations in the TM polarization with acoustic field equations for general curvilinear coordinates with the effective medium theory.…”

A novel broadband waterborne acoustic absorber

“…This method can manipulate the propagation trajectories of electromagnetic wave, guiding the wave in metamaterial to propagate as designed path. Many researchers have expanded this method to acoustic waves, [16][17][18] matter waves, 19 and even surface water waves. 20,21 Inspired by this method, an omnidirectional absorber 22,23 (like black hole) was also designed, and experimentally validated through different procedures.…”