SIS QUANTUM DETECTOR IN THE 1-10 MICRON REGION FABRICATED BY SEQUENTIAL DEPOSITION OF THIN FILMS OF HIGH TC BI-CA-SR-CU-O

IN THE PROPOSED PROGRAM, FOR THE FIRST TIME, FEASIBILITY OF DEVELOPING AND CHARACTERIZING A HIGHLY SENSITIVE AND HIGH SPEED QUANTUM DETECTOR IN THE 1-10 U WAVELENGTH REGION USING A SUPERCONDUCTING SIS TYPE WEAK LINK OF BI-CA-SR-CU-O, IS EXAMINED. THE DETECTION PRINCIPAL IS BASED ON THE FACT THAT THE ABSORBED INFRARED RADIATION REDUCES THE ENERGY GAP OF THE SUPERCONDUCTOR, MODIFYING THE CURRENT-VOLTAGE CHARACTERISTICS OF JOSEPHSON JUNCTION WHICH CAN SERVE AS A USEFUL DETECTOR OUTPUT. RECENTLY, IN A PRELIMINARY EXPERIMENT, WE HAVE OBSERVED FOR THE FIRST TIME, NOT ONLY A SLOW BOLOMETRIC RESPONSE BUT ALSO A FAST NON-THERMAL QUANTUM RESPONSE DUE TO COOPER PAIR BREAKING AND QUASI-PARTICLES GENERATION IN YBA-CU-O FILM SUBJECTED TO PULSED 532 NM LASER. IN THE PRESENT WORK, PRECISELY CONTROLLED SUPERCONDUCTING, INSULATING, AND SUPERCONDUCTING THIN FILMS OF BI-CA-SR-CU-O WILL BE DEPOSITED ON A SUITABLE SUBSTRATE BY PLASMA ASSISTED LASER DEPOSITION USING 265 NM UV LASER AT 10 HZ. SUBSEQUENT TO A DEPOSITION, SUPERCONDUCTING WEAK LINK SIS TYPE JOSEPHSON JUNCTION WILL BE FABRICATED BY PATTERNING THESE FILMS WITH 532 NM VISIBLE LASER A 1 KHZ. FOR DETECTION, INFRARED RADIATION FROM ND:YAG LASER AT 1.06 U WILL BE MODULATED AND GUIDED THROUGH AN OPTICALFIBER TO THE DETECTOR. IN THE PHASE I, NON-EQUILIBRIUM (QUANTUM) RESPONSE OF THE DETECTOR AT 1.06 U AND THE TEMPERATURE DEPENDENCE OF THE RESPONSE WILL BE STUDIED. THE RESPONSIVITY OF THE DETECTOR IS ESTIMATED TO BE \ 10(4) V/W, WHICH IS SEVERAL ORDERS OF MAGNITUDE HIGHER THAN PRESENTLY AVAILABLE QUANTUM DETECTORS. IN PHASE II, WAVELENGTH DEPENDENCE OF THE RESPONSE IN THE 1-10 U REGION, HIGH FREQUENCY RESPONSE, AND THE TEMPERATURE DEPENDENCE OF THE RESPONSIVE TIME WILL BE INVESTIGATED.