Gouy shift and temporal reshaping of focused single-cycle electromagnetic pulses.

We discuss exact solutions of Maxwell's equations that describe the evolution of single-cycle electromagnetic pulses. The solutions are applied to recent observations of the diffraction transformation of terahertz pulses. In particular, we elucidate the role of the Gouy shift in the temporal reshaping and polarity reversals of single-cycle terahertz pulses.

Optical correlator that uses cesium vapor.

We obtain the correlation pattern between two amplitude-modulated input images of 36 and 280 random black and white pixels, using the standard degenerate four-wave-mixing geometry of 852-nm optical beams in a 1-mm-thick cesium-vapor cell. The total optical input power is 3.2 mW to obtain 0.

Measurement of the complex polarizability of electron traps in Bi(12)SiO(20) by a moving-grating technique.

We measure the optical two-beam coupling gain in three nominally undoped cubic n-type Bi(12)SiO(20) crystals as a function of the beam frequency difference Omega and the beam intensity. The crystal geometry is chosen so that the beam coupling through the ordinary photorefractive effect is absent. From the dependence of the gain on Omega the full complex polarizability difference alpha(fe) between a full and an empty deep trap at the wavelength of 515 am is deduced to be (-1.