Dresden 2020 – wissenschaftliches Programm
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TT 39.2: Hauptvortrag
Mittwoch, 18. März 2020, 15:30–16:00, HSZ 03
Ultra-Sensitive Microwave Kinetic Inductance Detectors from the Optical to the Far Infrared — •Jochem Baselmans1,2, Pieter de Visser1, Stephen Yates1, Lorenza Ferrari1, Vignesh Murugesan1, David Thoen2, and Akira Endo2 — 1SRON Netherlands Institute for Space Research — 2Delft University of Technology
Near future space-based observatories for the far-infrared and for the optical will need large arrays of cryogenic detectors with unprecedented sensitivity.
Aluminium based Microwave Kinetic Inductance Detectors (MKIDs) are the most promising for these applications. MKIDs are superconducting resonators whose resonant frequency and Q factor are modified due to photon absorption. They are read-out using a microwave readout signal at the unperturbed resonant frequency. These devices can be well described using the standard Mattis-Bardeen theory, with the added complexity that the quasiparticle energy distribution is modified by the absorption of readout photons with E = hfreadout<< Δ. At T<Tc/8 this process creates excess quasiparticles proportional to √Preadout, which limits the sensitivity. Since decreasing Preadout is impossible due to excess noise sources we reduce the device volume. This results in a Noise Equivalent Power NEP = 6· 10−20 W/√Hz, 4-5 times better than previously reported
For optical MKIDs, capable of single photon spectroscopy, an additional issue is the escape of high energy phonons from the aluminium film into the substrate. I will discuss recent experiments that use thin membranes to significantly reduce the phonon loss. This drastically increases the resolving power to 50 for 402 nm photons.