| Terahertz (THz) wave imaging is one of the most promising applications of THz technology. This dissertation presents detailed studies on an all-optical scanning THz wave imaging system. The THz wave emitter and detector are implemented with electro-optic crystals. In comparison with the traditional system with the photoconductive antenna emitter and detector, this THz wave imaging system not only improves the diffraction limited spatial resolution, but also has the potential to be applied to the mid-infrared range. Theoretical and experiment studies on the optimum crystal orientations for THz wave optical rectification generation and THz wave electro-optic sampling provide the guidelines for system optimization.; To further improve the spatial resolution of the all-optic THz wave imaging system, near-field THz wave imaging with a dynamic aperture created on semiconductor wafer is used. The achieved spatial resolution is 36 μm (∼ λ/10). The dynamic apertures on GaAs and Silicon wafers were experimentally investigated, and it is concluded that the GaAs wafer is best suited for near-field THz wave imaging with a dynamic aperture. The spatial resolution is determined by the focal size of an optical gating beam. The dynamic aperture technique does not show the severe high-pass filter effect in the reported near-field THz wave imaging method.; With the implementation of THz wave generation and detection in the same zinc-blende crystal, the construction of an electro-optic THz wave transceiver is demonstrated for the first time. The optimization of an electro-optic THz wave transceiver was experimentally carried out with the help of the theory of nonlinear different frequency generation and the equation of the induced refractive index ellipsoid. The unique application of the electro-optic THz wave transceiver in THz wave imaging facilitates THz wave imaging in a reflection geometry.; The above THz wave imaging configurations provide the basis for some novel applications of THz wave imaging. The exploration of various applications of THz wave imaging is illustrated with many THz wave images presented in this dissertation. Most of them had never been accomplished before, including THz wave images of watermarks, a mammographic phantom, the optically damaged areas on a GaAs wafer, the p+-doped unannealed and annealed areas on an n-doped Silicon wafer, and the THz wave time-of-flight images of coins. |
