7. Development and Applications of Metasurfaces for Terahertz Waves

The development of optical components, in the terahertz frequency range, composed of artificial metallic structures is reviewed, with particular focus on two-dimensional metamaterials (metasurfaces). Various electromagnetic responses and associated fundamental terahertz optical components such as polarizers, wave plates, lenses, and absorbers can be derived even from two-dimensional structures made from common materials. Such terahertz optical components are light and thin, made from readily available materials, and are easy to fabricate owing to the long wavelength of terahertz waves. Both linear and nonlinear optical responses in metamaterials have been developed. The generation of terahertz waves by the nonlinear optical response in silver nanostructures is investigated with a view to designing the nonlinear response of the light and terahertz waves in metamaterials.