Post-fabrication trimming of a 1024-pixel, single-photon counting, Microwave Kinetic Inductance Detector array with a pixel pitch of 150 micron

Abstract: Microwave Kinetic Inductance Detectors are superconducting resonators capable of single-photon counting with energy resolving capability at visible and near-infrared wavelengths. Their zero read noise, extremely low dark counts, and compatibility with frequency-division multiplexing make them well suited for large imaging arrays. The detector yield of these arrays is often limited by the fabrication-induced frequency scatter leading to resonator collisions. We find that the tight packing of the pixels can add significant frequency scatter as well. We developed a post-fabrication correction method that is suitable for tightly packed arrays with a pixel pitch of $150\ \mathrm{μm}$. We demonstrate this method on a 1024-pixel array multiplexed on a single octave of readout bandwidth and show a reduction in frequency scatter from $1.1\times 10<sup>{-2}$ to $3.5\times 10<sup>{-4}$ and an increase in yield from $76\%$ to $94\%$.