Picosecond pulse propagation on hybrid Tc transmission lines.
Abstract
The frequency response of a transmission line structure based on films of the high Tc superconductor YBaCu oxide has been studied. A high-current-density oxide film brought in close proximity to a coplanar Al transmission line acts as an additional ground plane for the mode structure of the tranmission line. This hybrid structure supports a pulse propagation partially in the Al lines and in the additional ground plane. The propagation of an initially 1-ps pulse through a 4-mm-long section of the coplanar lines covered with an additional ground plane of 1.0-μm epitaxial YBaCu-oxide film on SrTiO3 substrate (Tc = 91 K) was measured. The pulse shape after propagation for various temperatures is shown, and the broadening observed discussed. Similar measurements using an additional ground plane of Al or Nb show the same type of broadening as long as the resistance of the film is high. The measurements indicate that the epitaxial high Tc material can support frequencies up to ≅0.7 THz without apparent loss.