Response of YBa2Cu3O7- grain-boundary junctions to short light pulses

The electrical response of a single YBa2Cu3O7- grain-boundary junction to visible light pulses was measured. Using an autocorrelation technique with picosecond laser pulses, no fast voltage transients were observed with the junction biased just above its critical current. Apparently, there are no relaxation times in the range of 7 ps to 14 ns. Using direct time-domain measurement with nanosecond pulses, three types of junction response were recorded: a nonexponential decay of 11 s (90 to 10 % time) at temperatures near Tc; an inverse-time dependence of the order of 0.3 s (100 to 50 % time) in the temperature range of 4.2 to 15 K; and an exponential decay time of 0.15 s with the sample immersed in superfluid helium.