Numerical Comparisons of Terahertz Radiation from GaAs and GaAs: As+ Substrates.

In this paper, we have numerically analyzed the ultrafast change of local fields on the surfaces of a large-aperture photoconducting (LA-PC) antenna with GaAs and GaAs: As+ substrates. We find that the ultrafast screening of photogenerated carriers to the externally applied electric field has different effects on the saturation of THz radiation as the function of the laser fluence in the near and far field, respectively. Both screening effect of photocarriers and radiation effect are important in forming the saturation phenomena in the case of near field. But in far field, only the radiation effect is important. [ABSTRACT FROM AUTHOR]