Spatio-temporal imaging of terahertz electric-field vectors: Observation of polarization-dependent knife-edge diffraction

We develop a terahertz electric-field vector imaging system that uses the rotating polarizer technique. The imaging system is used to investigate the polarization-dependent optical response of a patterned indium tin oxide (ITO) film deposited on a glass substrate. While ITO is transparent for near-infrared probe light, it acts as a metal for terahertz light. Therefore, polarization-dependent diffraction can be observed at the edge of the ITO thin film, and only electric field components perpendicular to the edge boundary can propagate behind the ITO layer. By comparison with a numerical simulation, we reveal the polarization dependence of this so-called knife-edge diffraction.