Revealing radiationless sources with multi-harmonic mantle cloaking

A general formula for the scattering suppression of simultaneous cylindrical harmonic waves is reported for a bare dielectric cylinder. A proper surface impedance condition is imposed at the boundary between dielectric and background regions, revealing a parity-time condition for the internal electromagnetic field in order to be nonradiating. Depending on the maximum number Mmax of cylindrical harmonic waves to suppress along the azimuthal variable ϕ, such surface impedance function profile reveals several higher order nonradiating modes. The determination of Mmax is consistent with the degrees of freedom of the scattered fields. Moreover, the multi-harmonic mantle cloaking technique automatically generates radiationless sources suitable for the implementation with metal-dielectric metasurfaces or all-dielectric metamolecules.