Direct observation of the Gouy phase shift with single-cycle terahertz pulses

Summary form only given. Advances in the generation and detection of terahertz (THz) radiation have made it possible to investigate many of the propagation characteristics of wide bandwidth single-cycle electromagnetic pulses. In particular, the effects of diffraction on the temporal profile of such pulses has received attention both theoretically and experimentally. Recently it has been pointed out that the Gouy phase shift of electromagnetic beams should result in a polarity reversal for a terahertz pulse as it passes through a focus. In the paper we report the first clear and unambiguous observation of the Gouy effect with single-cycle terahertz pulses.