Optically tuned propagation delay in Y-Ba-Cu-O superconducting delay lines

An optoelectronic technique was used to study the optical tuning of electrical picosecond pulses propagation in YBa/sub 2/Cu/sub 3/O/sub 7-x/ superconducting delay lines. The propagation time through the delay lines was monitored as a function of the optical pulse energy incident on the superconducting thin film. The optical excitation consists of two 70 ps laser pulse trains at a 76 MHz repetition rate, generated by a mode-locked laser. One pulse train was used to pump a dye laser, while the second was used to illuminate the superconducting delay lines. The measured propagation time is well described by a squared dependence on the applied optical pulse energy. In addition, optically induced changes in the resonant frequency were investigated by using a resonator technique in the frequency domain.