Real time terahertz imaging is emerging as an important non-destructive imaging tool for medical, quality control, security and other industrial applications. In this thesis, we demonstrate real-time full-field terahertz (THz) imaging of still, moving, and concealed objects, and real-time THz images of the field distribution on the imaging plane. A femtosecond laser pulse from an amplified Ti:sapphire laser system with a pulse duration of 100 fs, repetition rate of 1 kHz, and 800 nm center wavelength is used to generate THz pulses via optical rectification in a 15x15 mm2 by 2 mm thick [110] ZnTe crystal. The THz pulses are collimated to a 1" diameter beam using off-axis parabolic reflectors. An object is placed in the collimated THz beam, and a plastic lens is used to form an image of the object on a second ZnTe crystal (detector). The THz image is detected by free-space electro-optic sampling using a large diameter gating beam derived from the laser source. Video or still images are captured by an 8-bit (30 fps) grayscale CCD camera, and objects hidden behind paper or inside Styrofoam can be clearly seen in real-time. We also study the ring-like spatial intensity distribution of the various frequency components of the THz pulse focused in the image plane by varying the time-delay between the THz and probe beams. Methods for improving signal-to-noise such as frame averaging and dynamic subtraction are also studied.
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