On the omnidirectional radiation via radially anisotropic zero-index metamaterials

Abstract

By a comprehensive mathematical derivation, we show that the underlying physics of realizing a two-dimensional omnidirectional radiation from multiple sources via radially anisotropic zero-index metamaterials (RAZIM), as numerically and experimentally demonstrated in Cheng Q. et al., Phys. Rev. Lett., 108 (2012) 213903, lies in that the RAZIM shell confines all anisotropic cylindrical modes within the shell, while keeping transparent to isotropic cylindrical modes. From the illustrated underlying physics, it follows straightforwardly that it is impossible to use the RAZIM for generating perfectly coherent isotropic radiation in a three-dimensional free space, contrary to the claim made in the above-mentioned reference.

Epsilon-near-zero or mu-near-zero materials composed of dielectric photonic crystals

“…Metamaterial as an artificial medium whose effective permittivity and permeability can be arbitrarily tuned, has become one of the most intriguing and important materials to control electromagnetic (EM) propagation in the past decade, promising a vast variety of unexpected physical phenomena [1][2][3][4][5][6]. Recently, metamaterials with near zero parameters, i.e., epsilon-near-zero (ENZ) metamaterials with permittivity near zero, mu-near-zero (MNZ) metamaterials with permeability near zero, and index-nearzero (INZ) metamaterials with both permittivity and permeability near zero, have been found to exhibit some unusual transmission properties and enable applications such as tailoring the wave fronts [7][8][9][10][11][12][13][14][15], creating sub-wavelength channels and bends [16][17][18][19][20][21][22][23][24], achieving total transmissions and reflections in a channel by engineering defects [25][26][27][28][29][30][31][32][33][34], constructing displacement-current wires and nano-circuit boards [35][36][37][38][39], arbitrarily controlling energy flux in anisotropic systems [40,41], subwavelength imaging…”

Additional modes in a waveguide system of zero-index-metamaterials with defects

“…After that, the research on metamaterials 2 3 4 5 6 7 has made great progress. Recently, attention to zero-index-metamaterials (ZIM) 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 32 33 has been extensive. For instance, matched impedance zero-index metamaterials (MIZIMs), epsilon-near-zero metamaterials (ENZ), anisotropic ENZ.…”

“…For instance, matched impedance zero-index metamaterials (MIZIMs), epsilon-near-zero metamaterials (ENZ), anisotropic ENZ. By utilizing ZIM, some applications and devices with novel functionalities can be realized, such as squeezing wave energy 10 11 12 13 14 , tailoring wave front 15 16 17 , realizing total transmission and reflection in ZIM 18 19 20 21 22 , waveguide bending 23 , enhancing radiation from an embedded source 24 25 26 , controlling energy flux 27 , etc. Several years ago, by putting perfect electric conductor (PEC) or perfect magnetic conductor (PMC) defects in ZIM in a waveguide structure, Hao et al .…”

Experimental Verification of Isotropic Radiation from a Coherent Dipole Source via Electric-Field-DrivenLCResonator Metamaterials

“…We experimentally demonstrate the isotropic radiation from an actual dipole source for the first time. Interestingly, this method, inspired by transformation optics, can enable the control of electromagnetic fields and engineering of new devices such as the invisibility cloak [1,6,7,[17][18][19][20][21][22][23], wormholes [24], waveguide connections [25][26][27][28][29], and antennas [30][31][32][33][34][35][36], by producing proper permittivity and permeability parameters. These devices can be realized by electric metamaterial fabrication, which are engineered by subwavelength artificial structures that produce necessary material properties corresponding to the space manipulation.…”