Kinetic Inductance Detectors for Cosmology

Kinetic inductance detectors (KIDs) feature ultra-high sensitivity, high quality factor (Q>105), wide band, easy fabrication, and the possibility to multiplexing large detector arrays. They have been applied in various astronomical projects in from the millimeter, infrared, optical to X-ray band, in passive imaging and single photon counting.

KIDs work at 1/8 of the critical temperature of its material, which is usually around 100 mK. They make use of the change in the surface impedance of a superconductor as the incoming photons break Cooper pairs, which will shift the resonance frequency. Then incoming signal can be detected by measuring the shift of phase in the resonator. KIDs array can be easily made by tuning their resonance frequency and can be readout in the frequency domain naturally.

PCCP/APC has been working on KIDs since 2012, mainly focusing on multi-colour antenna coupled KIDs for cosmology [1]. It uses wideband slot antenna to receive the signal and separates the signal into several bands by on-chip filters. Then the signal will be detected.

Fig.1 antenna couple KIDs developed at PCCP

PCCP has also been working on bi-layer material (Al/Au) for KIDs [2]. The initial results show the bi-layer KIDs have higher sensitivity than usual materials such as Aluminum and Niobium, as is shown in Fig. 2.

Fig. 2 Film resistivity and response of Al/Au KIDs

PCCP has a variety of collaborations with Paris Observatory and Institut Néel in France and Nazarbayev University in Kazakhstan.

[1] Dual-Color Antenna-Coupled LEKID for Next-Generation Multi-chroic CMB Focal Planes.

[2] Proximity-coupled Al/Au Bilayer Kinetic Inductance Detectors.