Low Temperature Detectors, Milano, Italy
Oral presentation (#325)
Arrays of lumped-element kinetic inductance detectors (LEKIDs) optically coupled through an antenna and transmission-line structure are a promising candidate for future cosmic microwave background (CMB) experiments. Using the separated architecture of a LEKID enables optical coupling to be realised, without the detector becoming susceptible to two-level system noise created by the amorphous-dielectric requirements of a simple microstrip feedline structure. Through initial investigations of small prototype arrays, we have shown this compact device architecture can produce intrinsic quality factors > 105, allowing for MUX ratios to exceed 10^3. Moreover, we have demonstrated that these devices are limited by generation-recombination or photon noise down to low modulation frequencies proving the devices are not susceptible to the fabrication requirements of any antenna feed or filtering network the device is coupled to. However, this optical configuration is highly susceptible to a reduction in sensitivity due to stray light. Here we discuss our investigation into a suitable method of stray-light suppression based on the addition of an absorbing layer compatible with our device design and present the current performance of our prototype devices.
SPIE Astronomical Telescopes & Instrumentation 2018, Austin, Texas
Oral presentation (10708-53)
(Short) Abstract: Arrays of lumped-element kinetic inductance detectors (LEKIDs) optically coupled through an antenna and transmission line structure are a promising architecture for next generation cosmic microwave background (CMB) experiments; like CMB-S4. To maximise the efficiency of future focal planes, it is desirable to observe multiple frequencies simultaneously within each pixel. Therefore, we utilise the proven transmission line coupling scheme to introduce band-defining structures to our pixel architecture. We present preliminary designs and measurements from a set of prototype filter-coupled detectors as the first demonstration towards the construction of large-format, multi-chroic, antenna-coupled LEKIDs with the sensitivity required for future observations of the CMB.
Low Temperature Physics 2017, Kurme, Japan
Poster presentation (PA-24)
Abstract: Optical coupling to a lumped-element kinetic inductance detector (LEKID) via an antenna and transmission line structure enables a compact detector architecture, easily optimised for the required sensitivity and multiplexing performance of future cosmic microwave background (CMB) experiments. Coupling in this way allows multi-chroic, polarisation-sensitive pixels to be realised through planar on-chip filtering structures. However, adding the necessary dielectric layers to LEKID structures to form the microstrip-coupled architecture has the potential to increase two-level system (TLS) contributions, resulting in excess detector noise. Using a lumped-element resonator enables coupling via a microstrip to the inductive section only, whilst leaving capacitive elements clear of potentially noisy dielectrics. Here we present the preliminary data acquired to demonstrate that a microstrip transmission line structure can be coupled to a LEKID architecture with minimal additional TLS contributions. This is achieved through a simple fabrication process, which allows for the dielectric to be removed from capacitive regions of the LEKID. As a result, we have produced resonators with the high quality factors required for large multiplexing ratios; thus highlighting the suitability of the separated KID architecture for future observations of the CMB.