Metamaterials-based Near-perfect Absorbers in the Visible and Infrared Range

Metamaterials, which consist of periodic arrays of sub-wavelength structures, induce anisotropic photonic properties within various frequency regimes of the electromagnetic spectra, such as microwave, terahertz, infrared and visible regions. This chapter reviews near-perfect absorbers based on metamaterials that have attracted great attention in the visible and infrared wavebands due to their potential applications, such as biochemical sensors, optical imaging, color filtering, photodetectors and photovoltaic solar cells. With respect to absorption bandwidths, near-perfect absorbers are classified as narrow-band and broadband absorbers. Because most metamaterials use plasmonic resonant metal arrays on dielectric materials, they tend to present a narrow absorption band. Geometric size, shape and patterns of metals are strongly correlated with plasmonic resonance wavelengths. Therefore, many studies have investigated broadband absorbers using multiplexed narrow-band plasmonic resonators. In this chapter, we review theoretical backgrounds and various strategies to achieve metamaterials-based near-perfect absorbers in the visible and infrared range. We describe various metal and dielectric structures formed by disks, rings, gratings, nanocomposite and mixed arrays. Applications based on narrow-band and broadband near-perfect absorbers are discussed. Metamaterials have great potential to enhance efficiency in any part of the visible and infrared spectra for sensing, imaging, photodetector and solar cell applications.