Analysis of quantum superconducting kinetic inductance photodetectors

Abstract

Analysis of a quantum superconducting kinetic inductance photodetector (QSKIP) structure is presented for operation in a low background environment. We project the QSKIP’s spectral response to be limited by the Cooper pair binding energy, 2Δ or about 32 μm for YBCO. The QSKIP response and sensitivity are computed from the minimum of the Hamiltonian energy functional and linearized Rothwarf–Taylor equations. Photoresponse and sensitivity expressions are computed in terms of the quasiparticle lifetime and indicate background limited infrared performance at very low photon flux levels. At low temperatures and under background 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 noise sources to fluctuations in the condensate population. With the noise and photoresponse equations, the QSKIP noise equivalent power is computed in terms of the characteristic lifetimes of: quasiparticle generation; quasiparticle recombination; anharmonic phonon decay; and phonon trapping. The calculated noise equivalent power for a YBCO QSKIP is about 2.5×10−15 W/√Hz at 9 K.

Josephson Photodetectors via Temperature-to-Phase Conversion

“…Kinetic inductance [1,11,12] and Josephson superconductor-normal-metal-superconductor-(S-N-S) [8,[13][14][15] based detectors make use of the temperature dependence of the supercurrent. The changes in the current response can be detected, e.g., via resonant circuits [11] or inductively or directly [1,16] coupled superconducting quantum-interference-device (SQUID) sensors. In the direct coupling scheme, variation of the critical current or inductance in the detector embedded as one junction of a dc SQUID affects the distribution of phase differences across the second junction and the current balance, which can be detected.…”

Superconducting detectors and mixers for millimeter and submillimeter astrophysics

“…At finite frequencies, the surface impedance is nonzero and is in fact largely inductive; this is known as the kinetic inductance effect due to its connection with the kinetic energy of motion of the Cooper pairs. Furthermore, the surface impedance responds to changes in the quasi-particle population, even at very low temperatures [140], [141]. This opens up the possibility of making very simple detectors [142], [143], which consist of high-thin-film microwave resonators, using coplanar waveguide transmission lines [144] for example.…”

“…For this mode of operation, the radiation is converted to heat, and so the temperature of the superconductor must be kept close to , where the variation of the kinetic inductance with temperature is largest. As noted earlier, a significant advantage can be gained if the radiation is directly absorbed by the superconductor to produce quasi-particle excitations rather than heat; SQUID-KIDs using this mode of operation have been proposed [140], [155]. Multiplexed readouts of SQUID-KIDs should be possible, with approaches similar to those followed for TES bolometers, but have not been studied in any detail yet.…”

Microwave parameters of HTSC thin film RC circuit

“…From the viewpoint of applications of superconducting electronics, characteristics of photoresponse (including thermal and photo inducted nonequilibrium effects) must be examined and evaluated for the development of optically controlled switches [4], delay lines [SI,filters [6], photo detectors [7]- [9] and other optical microwave systems [lo]- [12].…”