20 ps Pulsed Laser Irradiation to Current-Biased Kinetic Inductance Detector Made of Nb Nanowires

A current-biased kinetic inductance detector (CB-KID) is a new type of superconducting detector and senses a change in kinetic inductance in the superconducting nanowire biased by weak dc current I_b. Kinetic inductance depends on the density of Cooper pairs. Therefore, when Cooper pairs are broken by local energy dissipation, a change in kinetic inductance ΔLk can be obtained by monitoring a voltage V across the CB-KID sensor. The CB-KID has a wide operating temperature regime in the superconducting state whereas a current-biased transition edge detector senses a change in resistance at the superconductive transition edge and operates only at near vicinity of Tc. The confirmation for the validity of the CB-KID idea was preceded by using an MgB₂ CB-KID meanderline detector. We extended this CB-KID method to a conventional Nb nanowire. We consider that our Nb-based CB-KID has versatile potentials in the various future applications. It is for the first time that the Nb-based CBKID operates at 4 K and has a capability of submicrometer position resolution.