Optical tuning of propagation time in YBa2CuO7-x superconducting delay lines

We present the observation of an optical pulse energy controlled delay in the propagation time of electrical picosecond pulses in YBa2Cu3O7-x (YBCO) superconducting delay lines. The delay lines were patterned in the geometry of a microstrip and were illuminated by the frequency-doubled output (532 nm) of an Nd:YAG laser. The propagation time of picosecond electrical pulses through the delay lines was measured using an electrical autocorrelation technique with photoconductive switches. The experiments were conducted at 30 and 55 K and delay tuning up to 54 ps was observed. The measured propagation time (τ) shows a quadratic dependence on optical pulse energy (p), τ=τ0(1+a(p/pc)2) , where pc is a critical optical pulse energy beyond which superconductivity has disappeared. (author)