4. Terahertz Metamaterials and Metadevices

Terahertz metamaterials are designed to interact at terahertz (THz) frequencies, which is usually defined as 0.1–10 THz. Terahertz regime is located at the interface of electronics and photonics where technologies directly translated from microwave and optical regime generally fail to operate. This is so-called terahertz gap that is caused mainly by weak or nonexistent material response at terahertz frequencies. Coupled with various passive and active media, terahertz metamaterials offer a solution to fill the terahertz gap. Moreover, there is a possibility that terahertz metadevices will become the next enabling technological breakthrough in terahertz technologies, particularly desirable to raise the performance and functionality of terahertz systems in imaging, sensing, spectroscopy, and nondestructive evaluation. This chapter will give a brief review about manipulation technologies and applications of various terahertz metamaterials and metadevices, such as passive type, active type, and flexible metamaterials and metadevices.