MMPAs Operating in Different Frequency Ranges

In this chapter, metamaterial perfect absorbers (MMPAs) are introduced by categories according to their operating frequencies: MMPA operating in the GHz, the THz, and the infrared (IR)/visible ranges. Although the existence of famous THz gap, below which the response of device is dominantly electronic, while above which it is dominantly photonic, the basic principle of operation of MMPA in the whole frequency range is nearly identical to each other, except for small details, for example, localized surface-plasmon polaritons which come into play in the IR/visible range because their energies correspond to IR/visible. Therefore, a simple scale down of the structure operating at GHz is possible for operating in higher-frequency ranges. For individual frequency ranges considered in this Chapter the broadband behavior, polarization independence, tunability and omni-directional behavior are discussed individually. In the near future MMPA will play a key role in the field of photonics and optoelectronics.