Transparent uniaxial anisotropic spherical particles designed using radial anisotropy.

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.