SPATIOTEMPORAL SHAPING OF HALF-CYCLE TERAHERTZ PULSES BY DIFFRACTION THROUGH CONDUCTIVE APERTURES OF FINITE THICKNESS

We demonstrate a simple quasi-optical technique for spatiotemporal sha ping of half-cycle terahertz-radiation pulses. We show, both experimen tally 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 t o solve Maxwell's equations for such a geometry and show that it can e xplain all the experimentally observed features. In the case of a thic k aperture, a planar waveguide model can also be used to describe the propagation of the pulse through the aperture, with excellent agreemen t with the experimental re suits. (C) 1998 Optical Society of America.