Electromagnetic beam modulation through transformation optical structures

The transformation media concept based on the form-invariant Maxwell's equations under coordinate transformations has opened up new possibilities of manipulating electromagnetic ( EM) fields. In this paper, we report on application of the finite-embedded coordinate transformation method to the design of EM beam-modulating devices both in Cartesian coordinates and in cylindrical coordinates. By designing the material constitutive tensors of the transformation optical structures through different kinds of coordinate transformations, either the beamwidth of an incident Gaussian plane wave could be modulated by a slab or the wave-propagating direction of an omnidirectional source could be modulated through a cylindrical shell. We present the design procedures and the full-wave EM simulations that clearly confirm the good performance of the proposed beam-modulating devices.