THz photoconductive antennas are most commonly devices in THz sysytems. In this devices, method for generating and detecting terahertz waves is to excite a voltage-biased photoconductive antenna(PCA) with an extremely short laser pulse. The pulsed laser generates charge carriers in a photoconductive substrate which are swept onto the metallic antenna traces to produce an electric current that radiates or detects a terahertz band signal. Therefore, analysis of a photoconductive antenna requires simultaneous solutions of both semiconductor physics equations (including drift-diffusion and continuity relations) and Maxwell’s equations.In this thesis, first different sources of terahertz waves are introduced and their advantages and disadvantages are discussed. Westudy photoconductive antennas which have most application in THz wave generation. By analysing and various simulations, we identify effective ways for improvement performance of this devices and effective operation of them expressed. For proper design and reliable, analysis, design and modeling of this antennas have been made in accurate manner and without any conventioal approximations. Because of operation of this antennas and also having high accuracy in design of them, we have been used two different simulation tools for modeling them. The optoelectronic solver, is used to find an accurate absorbed optical intensity and optical carrier generation rate inside the fast photoconductive region through solving an optical scattering problem. Then, the equations governing the charge carrier traort inside the photoconductor are solved to obtain THz photo-current by considering realistic material parameters. Through a full-wave electromagnetic solver, and using calculated photo-current from the optoelectronic solver, antenna parameters and radiated THz power are obtained. During the proposed simulation method, the effect of PCA and photomixer parameters on the THz photo-current for various active region geometries are investigated. Keywords: Terahertz, Photoconductive Antenna, Photoelectric, Optoelectronic
