Broadband optical metasurfaces and metamaterials

In this chapter, we investigate recent breakthroughs in the development of broadband optical metamaterials and metasurfaces that illustrate how their exotic properties can be exploited for broadband applications. In the first part of this chapter, dispersion engineering is introduced as a powerful method for exploiting the resonant properties of metamaterials over broad wavelength ranges in order to enhance practical devices. The second part of the chapter examines how the metamaterial loss can be exploited for broadband absorption in the infrared regime. A robust genetic algorithm (GA) synthesis technique is used to design super-octave and multi-octave metamaterial absorbers (MMAs) using only a single patterned metallic screen. The last part of the chapter investigates broadband optical metasurfaces that can control the phase and polarization of a reflected wave. Optical metasurface designs are presented along with measurement results that demonstrate broadband and wide- angle quarter-wave plate and half-wave plate functionalities. A second type of metasurface based on nanoantenna arrays that can artificially induce a phase gradient in the cross-polarized reflected or transmitted wave at an interface and, therefore, steer and focus light is also presented. Together, these metamaterial and metasurface examples illustrate the potential for nanostructured metamaterials to provide unique functionalities over broad bandwidths to facilitate practical optical devices.