Fullwave analysis of picosecond photoconductive switches

Abstract

A fullwave analysis method for characterizing fast photoconductive switches (PCs) is proposed. Three-dimensional Maxwell curl equations, including the conductive current components, are solved using a finite-difference time-domain scheme. It is found from simulations that PCs in coupled microstrip lines with small widths and spacings are very effective in avoiding propagation of non-quasi-TEM modes and for achieving rapid responses. Futhermore, responses for PCs with pulse-forming networks constructed of coplanar waveguide shunt electrodes are simulated. Ultrashort electrical pulses with minimum widths of 0.2 and 0.4 ps can be obtained by symmetric and antisymmetric excitation methods, respectively, for linewidth and spacing readily realized.<>