NEAR-FIELD PROPAGATION OF TERAHERTZ PULSES FROM A LARGE-APERTURE ANTENNA

The near-field propagation behavior of terahertz (THz) pulses generate d by a planar large-aperture photoconducting THz transmitter has been characterized. A simulation model based on Huygens-Fresnel diffraction theory has been developed that permits accurate prediction of the spa tiotemporal profiles of the THz beam everywhere and gives excellent ag reement with experimental measurements. Two key conclusions emerge fro m this research, namely, the realization that for practical laboratory setups one is always working in the near-field regime and that the pr oper temporal shape of the THz field at the antenna is one that rises rapidly but decays slowly. (C) 1998 Optical Society of America.