Highly efficient resonant antennas for terahertz photomixers

This paper presents antenna structures suitable for terahertz photomixer designs. Two antenna structures are selected: a four-leaf-clover-shaped antenna on an extended hemispherical substrate lens and a full-wavelength dipole antenna on a thin substrate with backside excitation. The input impedance and radiation characteristics of each antenna are different, being affected by both the antenna shape and the substrate geometry. In addition, the bias line structure, which is indispensable in a THz photomixer antenna design, has a substantial effect on antenna performance, and a thorough understanding of its characteristics is necessary. Each antenna design will be presented in turn and some challenges facing antenna design will be discussed.