Broadband Carpet Cloak Designed Using Nanocomposite Metamaterials for 3–5-μm Wavelength Range

In this paper, a broadband carpet cloak using nanocomposite layers to operate in whole 3-5-μm wavelength band is designed successfully. For this purpose, spherical nanometals or doped semiconductors with desired plasma frequency are proposed. In this way, the refractive index of the cloak as an analytic function is considered by optical conformal mapping. In a two-dimensional structure, we approximated the obtained refractive index inside each pixel to be constant. Each pixel is considered as an effective medium that possesses nanoparticles with desired plasma frequency. Therefore, plasma frequency of nanoparticles should be adjusted proportional to the desired value of refractive index in each two-dimensional pixels, which is approximated to be constant (two-dimensional layers approximation). The cloak region is compacted for broadband performance. To compact the cloak region, refractive index values should be greater than 1 and realization of these required values is possible by designing nonresonant structures.