  The enhanced terahertz radiation from a new photoconductive antenna (PCA) has
been predicted by numerical simulation. Different from the conventional PCA,
the proposed PCA has electrodes with sawtooth structures on the edge, which
will introduce stronger localized bias field than common electrode (e.g.
strip-line structure). In addition, the elliptical beam of the laser source is
used to illuminate the sawtooth structure of the PCA, so that the effective
region of the terahertz excitation is enlarged and higher laser power can be
applied before saturation effect occurs. The design of the proposed PCA is
presented, and its performance is predicated by numerical analysis based on the
full-wave finite-difference-time-domain method. The simulated result shows
that, comparing with a conventional PCA, the proposed PCA achieves $1.4$ times
enhancement of the THz radiation field(i.e. peak of the time-domain THz pulse)
at the same condition. Further enhancement as high as $2$ times can be achieved
when considering the upper limit of the power density of the incoming laser
beam.
