Spatiotemporal shaping of half-cycle terahertz pulses by diffraction through conductive apertures of finite thickness

We demonstrate a simple quasi-optical technique for spatiotemporal shaping of half-cycle terahertz-radiation pulses. We show, both experimentally and theoretically, that properly polarized half-cycle pulses can be modulated temporally by diffraction through a conductive aperture of finite thickness. We use the finite-difference time-domain method to solve Maxwell's equations for such a geometry and show that it can explain all the experimentally observed features. In the case of thick aperture, a planar waveguide model can also be used to describe the propagation of the pulse through the aperture, with excellent agreement with the experimental results. (C) 1998 Optical Society of America.