External Cylindrical Invisibility Cloaks With Small Material Dynamic Range

By means of the commonly used transformation optics, and a general transformation function, new sets of external cylindrical invisibility cloaks are proposed. For the proposed cloaks, a rigorous analysis is performed and the results indicate zero scattering coefficients outside of the cloaks. Later, a numerical investigation shows that the material dynamic range (MDR) of the proposed cloaks can be as small as half of that of the previously introduced cloak which was based on a simple linear transformation function. The obtained analytical results are verified using a Finite-Element computational analysis.