Superconducting kinetic inductance photon detectors

We are investigating a novel superconducting detector and readout method that could lead to photon counting, energy resolving focal plane arrays. This concept is intrinsically different from STJ and TES detectors, and in principle could deliver large pixel counts, high sensitivity, and Fano-limited spectral resolution in the optical/UV/X-ray bands. The readout uses the monotonic relation between the kinetic surface inductance <i>L_s </i>of a superconductor and the density of quasiparticles <i>n</i>, which holds even at temperatures far below <i>T_c</i>. This allows a sensitive readout of the number of excess quasiparticles in the detector by monitoring the transmission phase of a resonant circuit. The most intriguing aspect of this concept is that passive frequency multiplexing could be used to read out ~10⁴ detectors with a single HEMT amplifier. Single x-ray events have been observed in prototype detectors.