Self-Assembled Arrays of Gold Nanorod-Decorated Dielectric Microspheres with a Magnetic Dipole Response in the Visible Range for Perfect Lensing and Cloaking Applications

Photonic nanostructures made of a dielectric sphere covered with many metallic nanospheres fabricated by self-assembly constitute a basic building block for optical metamaterials with a magnetic response in the visible. However, they suffer from limited degrees of freedom to tune their response. Once the involved materials are chosen, the response is mostly determined. To overcome such a limitation, we design, fabricate, and characterize here a bottom-up metamaterial in which metallic nanorods are used instead of nanospheres. Nanorods offer the ability to tune the spectral position of the resonances by changing their aspect ratio. Building blocks consisting of dielectric spheres covered with metallic nanorods are fabricated and characterized. They are also deposited in densely packed arrays on a substrate using a blade coating deposition of the dielectric spheres first and a subsequent deposition of the metallic nanorods. Full-wave optical simulations support the spectroscopic characterization. These simulations also indicate a dominant magnetic dipolar response of the building blocks. These arranged core-shell structures are promising materials for applications such as perfect lensing and cloaking.