Influence of Substrate Material on Radiation Characteristics of THz Photoconductive Emitters

Figure 5

Schematic drawing of the THz wavefront propagation from GaAs substrate (a) and Si substrate (b) in a Si lens. In the case of a refractive index jump between the substrate and the lens a limiting stop aperture appears, leading to additional interference distortions of the THz radiation pattern. The stop aperture size in the case of Si substrate is determined by the lens size. The antenna sits in the center at the leftmost interface.

(a)

(b)