Fast nonequilibrium induction detectors based on thin superconducting films

A new type of fast detector is proposed. The operation of the detector is b ased on the change induced in the kinetic inductance of NbN and YBa2Cu3O7-d elta superconducting films by nonequilibrium quasiparticles produced by ele ctromagnetic radiation. The speed of a NbN detector is essentially temperat ure-independent and is less than I ps. A model based on the Omen-Scalapino scheme describes well the experimental dependence of the voltage-power sens itivity of a NbN detector on the modulation frequency of the radiation. A l ow equilibrium quasiparticle density and a high quantum yield give detectin g power D* 10(12)W(-1) . cm . Hz(1/2) at temperature T= 4.2 K and D*= 10(16 ) W-1 . cm . Hz(1/2) at temperature T= 1.6 K. The time constant of the low- temperature YBaCuO induction detector is determined only by the electron-ph onon interaction time tau(e-ph)(d) in the nodal regions. (C) 1998 American institute of Physics. [S1063-7842(98)01110-6].