Vector analysis of terahertz transients generated by photoconductive antennas in near- and far-field regimes

We apply a three-dimensional finite-difference time-domain method to simulate the self-consistent creation of near- and far-field THz-frequency vector fields from a femtosecond-pulse-excited photoconductive antenna. The simulation results reveal some key features of the near-field patterns on the photoconductive antenna. The THz wave forms and their Fourier transformed spectra agree well with experimental characteristics. Additionally, we find some significant deviations from a simple Hertzian dipole approximation. (C) 2003 American Institute of Physics.