Microwave Kinetic Inductance Detectors (MKIDs) are a class of superconducting cryogenic detectors that simultaneously exhibit energy resolution, time resolution and spatial resolution. The pixel yield of MKID arrays is usually a critical figure of merit in the characterisation of an MKIDs array. Currently, for MKIDs intended for the detection of optical and near-infrared photons, only the best arrays exhibit a pixel yield as high as 75-80%. The uniformity of the superconducting film used for the fabrication of MKIDs arrays is often regarded as the main limiting factor to the pixel yield of an array. In this paper we will present data on the uniformity of the TiN/Ti/TiN multilayers deposited at the Tyndall National Institute and compare these results with a statistical model that evaluates how inhomogeneities affect the pixel yield of an array.
Microwave Kinetic Inductance Detectors (MKIDs) are cryogenic photon detectors and are attractive because they permit simultaneous time, energy and spatial resolution of faint astronomical sources. We present a cost-effective alternative to dedicated (e.g. analogue) electronics for prototyping readout of single-pixel Optical/NIR MKIDs by repurposing existing and well-known ROACH-1 boards. We also present a pipeline that modernises previously-developed software and data frameworks to allow for extensibility to new applications and portability to new hardware (e.g. Xilinx ZCU111 or 2x2 RFSoC boards).
MKIDs are promising candidates for next generation optical-IR instrumentation as they combine single pixel energy resolution, photon counting and vanishing dark counts with the possibility of megapixel arrays. Ti/TiN multilayers have significant advantages for MKIDs as they allow full control of the superconducting energy gap. We will compare the performance of different Ti/TiN stacks varying in Tc, layer number and film thickness. We have already achieved Qi up to 150 000 and will demonstrate how to control energy resolution and Qi and explore the proximity effect’s limits in the Ti/TiN system.
Dichroic beamsplitters, or dichroics, are filters that rely on the optical interference that occurs within thin layers to ensure the transmission and reflection of selective wavelengths of an incident beam of light. These optical components consist of a substrate coated on one or both surfaces with multiple layers of thin films, the spectral design and construction of which determine the isolation of particular wavebands. Discrepancies between the measured and expected spectral performance of optical elements with such coatings can largely be attributed to depositions errors and uncertainties in the refractive indices of the materials. Our model uses two-dimensional transmission line modeling to evaluate the transmittance of light through multilayer coatings deposited on a substrate material for given materials, angle of incidence and polarisation. This model allows us to perform Monte Carlo simulations to obtain statistical information about the tolerance of the coating performance to systematic and random uncertainties from the manufacturing process, as well as from environmental changes in space. With the aid of accurate manufacturing recipes and uncertainty amplitudes from commercial manufacturers, this tool can predict variations in the optical performance that result from the propagation of each of these uncertainties for various hypothetical scenarios. One particular application of this study are the dichroics of the ARIEL space telescope. We compare the predicted optical performance with transmission measurements at cryogenic temperatures for one of the ARIEL dichroics, which show the specification compliance of this prototype after many thermal cycles.
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