Kinetic Inductance Detectors based on superconductors

Kinetic Inductance Detectors (KIDs) are highly sensitive superconducting detectors, based on changes in the kinetic inductance within the detector. The detector is built in the form of a resonance circuit, where the inductive part 'contains' kinetic inductance. The kinetic inductance changes when the charge carrier density in the superconductor, Cooper pairs, changes due to photon impact. The photon energy required to activate the detector (break the Cooper pairs) is 3 orders of magnitude lower than the photon energy required to activate a semiconductor detector, thus presenting a significant advantage in the form of extremely high sensitivity to low-energy photons. Additionally, kinetic inductance detectors, due to their resonance circuit structure, enable spatial resolution (multi-pixel detectors) without increasing the complexity of the setup, compared to other superconducting detectors where building a multi-pixel detector results in a much more complex setup.

In our group, we have developed several NbN (Tc=16 K),  MgB2 (Tc=40) and YBCO (Tc=90 K) based kinetic inductance detectors for various frequency ranges - IR, THz, X-Ray. The resonance circuit is of the half-wavelength type, but each frequency range requires its own unique geometry. For example, for IR, a high density of conduction lines is required to 'collect' as many photons as possible. For THz, an 'antenna' is required to capture the photons, and for X-Ray, a thick layer of superconductor is required to absorb the photons and prevent them from 'passing through' the detector. The developed detectors demonstrated, for the first time, performance close to the theoretical possible sensitivity.

In addition, we used these detectors to conduct fundamental research on superconductors 

[1]          A. Roitman, A. Shaulov, and Y. Yeshurun, “Characterization of YBa2Cu3O7-δ  coplanar resonator for microwave kinetic inductance detectors,” Supercond. Sci. Technol., vol. 36, no. 1, p. 015002, Jan. 2023, doi: 10.1088/1361-6668/ac9eea.

[2]          A. Roitman, C. Pfaff, T. Hauet, A. Shaulov, and Y. Yeshurun, “Microwave Kinetic Inductance Detector Made of Molecular Beam Epitaxy (MBE)-Grown MgB2 Film,” Nanomaterials, vol. 14, no. 21, p. 1731, Oct. 2024, doi: 10.3390/nano14211731.