Geometrical factors in the emission of terahertz radiation from semiconductors under excitation by sub-picosecond pump pulses

Geometrical factors play an important role in the emission of terahertz radiation from semiconductors, as has been recognized for many years. This is particularly the case for the mechanism of optical rectification. Early work in the area was concerned with simple geometric arrangements, such as normal incidence of the pump radiation on the emitter surface, and low-index crystal faces, such as (001), (011), and (111). In this paper the general problem will be described for arbitrary angles of incidence and detection relative to the emitter crystal axes. It is seen that new information about the bulk and surface contributions to the optical rectification emission is obtained.