ANALYSIS OF QUANTUM SUPERCONDUCTING KINETIC INDUCTANCE PHOTODETECTORS

Analysis of a quantum superconducting kinetic inductance photodetector (QSKIP) structure is presented for operation in a low background envi ronment. We project the QSKIP's spectral response to be limited by the Cooper pair binding energy, 2 Delta or about 32 mu m for YBCO. The QS KIP response and sensitivity are computed from the minimum of the Hami ltonian energy functional and linearized Rothwarf-Taylor equations. Ph otoresponse and sensitivity expressions are computed in terms of the q uasiparticle lifetime and indicate background limited infrared perform ance at very low photon flux levels. At low temperatures and under bac kground limited infrared performance conditions, the photoresponse is proportional to the number of absorbed photons. Operating the QSKIP in the Meissner state and below 50% of the critical current limits the n oise sources to fluctuations in the condensate population. With the no ise and photoresponse equations, the QSKIP noise equivalent power is c omputed in terms of the characteristic lifetimes of: quasiparticle gen eration; quasiparticle recombination; anharmonic phonon decay; and pho non trapping. The calculated noise equivalent power for a YBCO QSKIP i s about 2.5X10(-15) W/root Hz at 9 K. (C) 1995 American Institute of P hysics.