MKIDs made from alternating stacks of Ti and TiN have shown impressive results in far-IR and sub-mm detectors to date, which promises improvements for Optical to Near-IR MKIDs. TiN/Ti/TiN tri-layers offer different advantages between sub-stoichiometric and stoichiometric recipes. We will elaborate on the expected effects of using sub-stoichiometric vs. stoichiometric TiN in triple layers on the wavelength signal-to-noise ratio of MKIDs. We characterise the photon detection performance of TiN/Ti/TiN Optical to Near Infrared MKIDs deposited on silicon wafers. We present measurements of resolving power, quasi-particle lifetime and sensitivity to near-infrared photons with differing pixel fabrication procedures and design.
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.
We develop a photon energy measurement scheme for single photon counting Microwave Kinetic Inductance Detectors (MKIDs) that uses principal component analysis (PCA) to measure the energy of an incident photon from the signal (“photon pulse”) generated by the detector. PCA can be used to characterize a photon pulse using an arbitrarily large number of features and therefore PCA-based energy measurement does not rely on the assumption of an energy-independent pulse shape that is made in standard filtering techniques. A PCA-based method for energy measurement is especially useful in applications where the detector is operating near its saturation energy and pulse shape varies strongly with photon energy. It has been shown previously that PCA using two principal components can be used as an energy-measurement scheme. We extend upon these ideas and develop a method for measuring the energies of photons by characterizing their pulse shapes using any number of principal components and any number of calibration energies. Applying this technique with 50 principal components, we show improvements to a previously-reported energy resolution for Thermal Kinetic Inductance Detectors (TKIDs) from 75 eV to 43 eV at 5.9 keV. We also apply this technique with 50 principal components to data from an optical to near-IR MKID and achieve energy resolutions that are consistent with the best results from existing analysis techniques.
KEYWORDS: Multiplexing, Field programmable gate arrays, Digital filtering, Microwave radiation, Inductance, Sensors, Data conversion, Resonators, Astronomy, Signal processing
At DIAS, in collaboration with Trinity College Dublin, we are developing visible and near-infrared Microwave Kinetic Inductance Detectors (MKIDs) for astronomical applications. By designing an array of MKIDs with different resonant frequencies, an array of thousands of detectors can be readout with inherent frequency domain multiplexing (FDM). The Xilinx ZCU111 Radio Frequency System on Chip (RFSoC) Evaluation Kit is a very promising option not only for Microwave Kinetic Inductance Detector (MKID) readout systems, but also for any application relying on frequency domain multiplexing. The board's on-chip data converters provide ample bandwidth for reading out up to 8,000 MKID resonators, with 2 MHz spacing, at a 1 MHz pixel sampling rate. Without additional resources, we roughly estimate the ZCU111’s field programmable gate array (FPGA) can analyse ~ 4,000 MKID pixels, at a cost of about €4.75 per pixel. We present initial progress from developing firmware for this MKID readout system.
Microwave Kinetic Inductance Detector (MKID) arrays are currently being developed and deployed for astronomical applications in the visible and near infrared and for sub-millimetre astronomy. One of the main challenges of MKIDs is that large arrays would exhibit a pixel yield, defined as the percentage of individually distinguishable pixels to the total number of pixels, of 75 80 %.1 Imperfections arising during the fabrication can induce an uncontrolled shift in the resonance frequency of individual resonators which end up resonating at the same frequency of a different resonator. This makes a number of pixels indistinguishable and therefore unusable for imaging. This paper proposes an approach to individually re-tune the colliding resonators in order to remove the degeneracy and increase the number of MKIDs with unique resonant frequencies. The frequency re-tuning is achieved through a DC bias of the resonator since the kinetic inductance of a superconducting thin film is current dependent and its dependence is non linear. Even though this approach has been already proposed,2 our innovative pixel design may solve two issues previously described in literature such as non-negligible electromagnetic losses to the DC bias line, and the multiplexibility of multiple resonators on a single feed-line.
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