Here we present a direct observation of the Gouy effect through THz impulse
scattering from cylindrical and spherical targets. A pi/2 Gouy phase shift
through a one-axis focus compared to the more common pi phase shift of the
two-axis focus is required to interpret the scattering results using a phy
sical optics model. (C) 2000 American Institute of Physics. [S0003-6951(00)
02306-8].