Terahertz photoconductive switch performance dependence on antenna shape

Abstract

Terahertz photoconductive switch antennas come in many designs that appear to be hardly ever sensibly selected. The femtosecond laser induced carriers generate a continuum at terahertz frequencies that require a low Q factor antenna design achievable through ohmic losses. On the one hand, if a broadband terahertz spectrum is desired, a simple coplanar stripline configuration with narrow arm width, i.e. a short dipole, is sufficient. On the other hand, the practical antenna resonance effect raises fabrication and engineering challenges, while the studied antenna shapes provide only a slight improvement to the emission efficiency. These findings are supported by the terahertz emission and detection characterization of a dozen antenna designs, and the results are discussed through the classical Drude-Lorentz conductivity framework.