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arXiv · 2604.12287

In Situ Interferometric Spatial Mapping Of A Microwave Kinetic Inductance Detector Array

Chris Albert·Ritoban Basu Thakur·Farzad Faramarzi·Byeong Ho Eom·Sumit Dahal·Andrew Bear·Reinier Janssen·Henry LeDuc·Thomas Stevenson·Peter Day
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Abstract

We present a method of spatially mapping microwave kinetic inductance detector (MKID) arrays, in a dark setup. MKIDs are superconducting natively multiplexed resonators which enable kilopixel arrays, such as for the proposed Probe far-Infrared Mission for Astrophysics (PRIMA). In such telescope applications one must map the spatial location of each MKID with their individual resonance frequencies. Traditional LED arrays or beam-mapping methods become increasingly difficult as pixel spacing decreases, e.g., 900 μm separated MKIDs in the spectrometer module of PRIMA. Our new mapping technique uses a cryogenic interferometer in reflection mode. As on-resonance signals reflect from an MKID, they accrue a phase proportional to the path-length, exactly corresponding to their physical distance on the feedline. Specifically, we use a superconducting transmission line that has nonlinear kinetic inductance. The slow-wave structure of this nonlinear device is designed to have a signal speed of 0.64% the speed of light, enabling a compact system. Current biasing this line allows for varying the wave speed and ensuring that the phase measured is periodic within a nulling interferometric mode. Using this setup, we measure a length ordering that reflects the bimodal MKID distribution of a 44 pixel array of MKIDs designed for PRIMA which contains the same spacing as the final kilopixel array design.

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Chris Albert, Ritoban Basu Thakur, Farzad Faramarzi, Byeong Ho Eom, Sumit Dahal, Andrew Bear, Reinier Janssen, Henry LeDuc, Thomas Stevenson, Peter Day. 2026-04-14. In Situ Interferometric Spatial Mapping Of A Microwave Kinetic Inductance Detector Array. https://doi.org/10.1109/tasc.2026.3678198

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