Comparison of frequency responses of cloaking devices under nonmonochromatic illumination

Plasmonic coatings have been proposed as a robust method to suppress the scattering signature of conventional dielectric objects, typically by surrounding a given object of moderate size with an isotropic, homogeneous, dispersive material that has a low or negative permittivity. In contrast to transformation-based cloaking devices, where highly anisotropic inhomogeneous materials achieve invisibility by electromagnetically isolating a certain region of space, plasmonic cloaks operate under the principle of scattering cancellation and usually allow field energy to enter the device's core. So far, plasmonic devices have been mostly examined using single-frequency, plane-wave excitations. In this work, the performance of such plasmonic cloaks when illuminated by more realistic, broadband nonmonochromatic pulses is investigated and compared with other cloaking mechanisms. The two-dimensional total-field scattered-field method is used within the finite-difference time-domain dispersive numerical technique in order to simulate time domain effects when temporally Gaussian pulses are launched toward cylindrical moderately-sized dielectric objects which are covered with appropriate plasmonic coatings. The results are compared to the performance of transformation-based cloaks, finding that the plasmonic cloaks may suppress scattering more effectively over a wider frequency range.