Continuing our previous findings that ultrashort pulses applied to Josephson junctions have excitation characteristics significantly different from the static limit, this work will investigate how different values of pulse duration actually change the excitation thresholds. The practical use of these results in the design of GHz superconducting electronics will be investigated. The electro-optic sampling technique will be applied to the transmission line structures to study their characteristics in the femtosecond (terahertz) regime. The algorithm previously developed by us for use in structures will be extended to allow inclusion of either BCS-type of dispersion or the two-fluid model results in computing transient dispersions. Since the loss of a superconducting transmission line is directly related to the quasiparticle distributions and, in the case of a gap-less superconductor, it is significantly different from the BCS result, our transmission experiments are then well suited to test the validity of this theory.
