Diffraction-induced edge contrast enhancement for terahertz imaging

Contrast enhancement is particularly important for imaging of weakly absorbing materials.We demonstrate the inherent contrast-enhancement effect at the edges of a transparent object by using a conventional pulsed terahertz imaging setup without additional modification of the system design.We provide both experimental and theoretical evidence suggesting that this effect is a consequence of the frequency-dependent energy loss of the terahertz radiation induced by edge diffraction.The influence of the phase step of the broadband terahertz pulses on the edge contrast is discussed.