Switching of a superconducting Y-Ba-Cu-O thin film by laser irradiation

Summary form only given. Measurements of the electrical response of a YBCO superconducting thin film to YAG laser light were performed. A pulsed Q-switched Nd:YAG laser was used to irradiate the film surface in the usual four-probe arrangement. The voltage signals of the sample provided with a DC bias current of 100 mA were measured with an oscilloscope at a laser energy of about 1.7 mJ/cm² for various initial temperatures. The signal was observed above 72 K and the risetime was about 30 ns. The voltage signals were converted into film temperatures by using the result of the temperature dependence of the DC resistance of the film. The increase in the film temperature was about 8 K at the initial temperature of 72 K. However. it became smaller with initial temperature and was about 4 K near T_c. Above T_c, it again is about 8 K. This result appears to indicate a jump in the specific heat of the film at T_c . The response of the sample to laser irradiation is bolometric