ABSTRACT
Terahertz (THz) wave radiation is defined as the far-infrared (FIR) electro-
magnetic radiation between 0.1 and 10 THz (1 THz¼ 1012 Hz), and it has become a rich field for fundamental physics and technological application.
THz wave science and technology is expected to become one of the key fields
in the twenty-first century. The interest in THz wave started as early as 1930s,
but the lack of good emission and detection techniques and devices left THz
less mature compared to its neighbor technologies (microwave and photon-
ics). At lower frequencies, microwave technology has been developed on
