Transparent uniaxial anisotropic spherical particles designed using radial anisotropy

Abstract

Based on Mie scattering theory and the assumption that the particle is electrically small in size (k(t)a≪1,k(m)a≪1), an analytic relationship between radial and tangential permittivity parameters has been established for achieving minimal scattering from an arbitrary rotationally uniaxial anisotropic spherical object incident by a plane wave. Analysis of fields in both the far- and near-field zones indicates that the derived relation is not only valid for electrically small particles, but also applicable to larger ones whose sizes are comparable with the free space wavelength after slight adjustments in parameters. Furthermore, it is observed that the dielectric spherical particle of reduced tangential permittivity yields better transparency performance than the design using a plasmonic cover by Alu and Engheta [Phys. Rev. E 72, 016623 (2005)]. As such, particles with carefully engineered radial anisotropy are transparent without using any coating and are ideal for applications with space constraint and stringent transparency criteria.

Quasi-Static Analysis of Scattering From a Metallic Sphere Coated by Radially Anisotropic Material

“…The constitutive parameters of the host medium and medium filling the core are ( h , μ 0 ) and ( 1 , μ 0 ), respectively. The tensor form of the permittivity for the anisotropic medium is written below [21][22][23][24][25]…”

“…The values of different parameters used to obtain behaviors are given in Table 1 [29]. The behavior of dielectric function (ω) = R (ω) + i I (ω) for three different metals obtained using LD model is shown in Equation (24). Figure 2 shows the dielectric function plots for W , Ag, and Au for wavelength range (800 nm to 3000 nm).…”

Mueller matrix holographic method for small particle characterization: theory and numerical studies

“…In previous holographic studies of spherical particles, all particles were assumed to be optically isotropic with no birefringence, and a scalar refractive index could be used with the Lorenz-Mie theory to calculate the holographic patterns. However, the materials from which spherical particles are composed can be birefringent with anisotropic refractive indices [18,19]. We will apply the Mueller matrix holography method to birefringent spheres and demonstrate how the polarization information can be used to discriminate the birefringence and orientation of small anisotropic spherical particles.…”

Optical neutrality: invisibility without cloaking

“…Another interesting development of the plasmonic cloaking idea is mantle cloaking, in which surface currents running at a specially designed metasurface, enclosing the hidden object, cancel scattering from the object [13][14] An alternative interpretation of invisibility is based on the "neutral inclusion" idea, where the invisibility conditions are understood as the quasistatic effective permittivity being unity [15,16]. Recently, it has been proposed that a sub-wavelength homogeneous sphere can be made invisible, without evoking cloaking [17][18][19]. This was demonstrated for a radially symmetric anisotropic metamaterial sphere in the Rayleigh approximation, where the quasistatic effective permittivity of the sphere becomes equal to unity and the induced dipole is suppressed.…”

“…where the parameters R and S, corresponding to multipole order l and , are provided in the Supplementary materials. In the quasistatic approximation the scattering cross-section of the radially anisotropic spheres is proportional to the polarizability ( ) ( ) with an effective dielectric permittivity [17][18][19]. Correspondingly, the neutrality condition for radially anisotropic spheres with extremely small radii,…”