Characterization of Ultrafast Superconducmting Optoelectronic Devices

Superconductors are materials that exhibit zero resistivity and ideal diamagnetism below a certain critical temperature, current and magnetic field. Zero resistivity is achieved by the formation of Cooper pairs (CP), which are paired electrons with opposite wave vectors and spins that are bonded together through electron-phonon interactions. In 1962, Brian D. Josephson theorized that CP's were capable of tunneling through an insulating barrier of a superconductor-insulator-superconductor (SIS) junction [2]. The phase coherence of these CP's produces unique electronic attributes of superconductive materials. Research in the field of low temperature superconductivity has focused on using Josephson junctions (JJ) for applications in digital electronics (51. The JJ response that is produced when the junction switches into a resistive state is the single-flux quantum (SFQ).-This is a voltage response that is equivalent to a logic "1 " and could be used in superconducting digital circuitry. Since the discovery of high temperature superconductors (HTS) in 1986 [I], much research and development has been carried out on these materials. Using Josephson junctions based on YBa2C~307-x (YBCO) thin films, junction devices can generate-