Optical metamaterials--artificially structured materials with engineered electromagnetic responses at optical frequencies--have exhibited optical properties not observed in their constituent materials and not found in nature. They extend the electromagnetic properties of usual optical media and allow unconventional material properties such as a negative magnetic permeability and a negative index of refraction. Optical metamaterials have enabled unprecedented flexibility in manipulating light waves and producing new functionalities. Among the many proposed metamaterial applications, two of the most prominent include the superlens that allows subwavelength resolution beyond the diffraction limit and the electromagnetic cloak, which promises the ultimate optical illusion--invisibility.
We have studied various topics in this field, from basic structures to potential applications. Specifically, we experimentally demonstrated the first optical magnetic metamaterial across the whole visible spectrum, and we also demonstrated the first optical negative-index material exhibiting a negative refractive index of -0.3 at the telecommunication wavelength of ∼ 1.5 μm. As for the potential applications with optical metamaterials, we proposed and analyzed a near-field superlens based on a composite metal-dielectric film, which can operate at practically any desired wavelength in the visible and near-infrared ranges. We also investigated the possibility of constructing an optical cloak of invisibility and presented the first practical design of such a device. Further studies on the topic include improved cloaking performance using high-order transformations and conceptual designs for high-order optical cloaking devices.
