Modeling Metamaterials Leads to Advance in Cloaking System Prototype

Duke University, Durham, North Carolina, and COMSOL, Inc., Burlington, Massachusetts

Thursday, November 01 2007

In efforts to use metamaterials to construct the world’s first working prototype of an invisibility cloak, researchers relied on multiphysics software.

Modeling software is generally used to show the fields and flows that are impossible to see with the eye or instruments. A group of researchers has done just the opposite: They ran computer simulations that showed it should be possible to fabricate the metamaterials necessary to build an “invisibility cloak” that makes an object invisible to certain frequencies.

The required electromagnetic properties of the cloaking shell are not of the sort found in natural materials. Knowledge of how to engineer materials with specific and complex electromagnetic properties has increased dramatically, and there is now an understanding of how to create “metamaterials” that behave as if they were continuous materials with permittivity, ε, and permeability, μ, that can vary with direction and position, and can even be negative. Early efforts at creating these materials were unsuccessful, but numerical simulations made it easy to study real-world material imperfections.

The geometry of the COMSOL Multiphysics simulation is simple (Figure 1). It solves the 2D cylindrical problem in which a perfect electrical conductor (PEC) infinite circular cylinder is wrapped by a cloaking shell. The PEC shell is a strong reflector of electromagnetic energy, and the goal is to mask this scattering in all directions. On the left and right sides are regions of PMLs (perfectly matched layers), which simulate the infinite domain in which the system resides. A uniform plane wave is launched by a sheet of uniform current density near the left edge of the domain. The top and bottom boundaries are perfect magnetic conductors (PMC) so that a uniform plane wave with its electric field pointed out of the page can terminate without reflection on these edges.