Ultrafast photoresponse of a structured YBa/sub 2/Cu/sub 3/O/sub 7- delta / thin film to ultrashort FIR laser pulses

The authors have investigated the photoinduced voltage response of a current-carrying structured YBa/sub 2/Cu/sub 3/O/sub 7- delta / thin film to ultrashort far-infrared (FIR) laser pulses in the frequency range from 0.7 THz to 7 THz. The detector has shown an almost constant sensitivity of 1 mV/W and a noise equivalent power of less than 5*10/sup -7/ W/ square root Hz. The temperature dependence of the decay time of the detector signal was studied for temperatures around the transition temperature of the film ( approximately 80 K). For a detector temperature where dR/dT had its maximum, the authors observed bolometric signals with decay times of about 2 ns, and for lower temperatures they observed nonbolometric signals with decay times of approximately 120 ps; the duration of the nonbolometric signals was limited by the time resolution of the electronic registration equipment.<>