Far Infrared Response Of Thin-Film Bi2sr2cacu2o8 Using A Free-Electron Laser

The far infrared response of granular thin-film Bi2Sr2CaCu2O8 superconductor has been investigated using long (almost-equal-to 5 mus) but sharply truncated free electron laser pulses in the frequency range between 50 cm-1 and 125 cm-1. Under constant current bias, a fast response and a slow bolometric signal component could be identified in this energy range, which is below the BCS energy gap (almost-equal-to 200 cm-1). Measurements of the power dependences of the signal voltages showed that both the fast and the thermal responses are consistent with the predictions of the resistively shunted Josephson junction model.