re created in the active area. The geometry of the antenna Terahertz Antenna in Future Healthcare Informatics also affects the mobility as well as the generation rate of the photocarriers which depends on the electric field distribution. To enhance the radiated THz power, antenna electrodes with sharp edges can be used that can operate with even less input optical power. Even-though the edge of the electrodes is very important to get high electric- field, the fabrication of sharp tiny edge antenna electrodes is difficult. Screening effects, velocity overshoot phenomenon, and the like, are some of the restriction phe- nomena in the generation of terahertz photocurrent [Cai et al. (1997)]. 12.7.1 DIPOLE PCA The first Hertzian dipole antenna similar to a photoconductive switch has been used both as a terahertz emitter and detector, proposed by Auston et al. [Auston, Cheung, & Smith (1984)]. The dipole geometry as shown in Figure 12.3 is the simplest design of PCA for THz radiation and it is being used because of its simplicity in design, and because it is less complex in nature. The electrodes can be biased using contact pads, coplanar strip line, and SO forth, to accelerate the generated photocarriers towards their respective electrodes. Factors such as photoconduction, the duration of optical pulses, and the geometry of PCA affects the radiated power, efficiency, bandwidth, and sensitivity for the terahertz radiation. But this dipole structured PCA has a larger gap between the two electrodes, SO the carrier drifting time is increased. Only a few photocarriers reach their corresponding electrodes and the remaining pairs end up in recombination as a result of the screening effect which leads to a reduction of terahertz radiation. So, to mitigate this effect and to boost PCA performance, the antenna geometry has to be modified with small antenna gap within the active area. 12.7.2 BOWTIE PCA To radiate terahertz, a bow-tie antenna which is printed on a semiconductor photocon- ductive substrate can be used which is sim