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 a 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 re suits. (C) 1998 Optical Society of America.