Crosstalk Reduction for Superconducting Microwave Resonator Arrays

TL;DR

This paper presents a new design for superconducting microwave resonator arrays that significantly reduces electromagnetic crosstalk, enhancing the performance of MKID-based imaging instruments for submillimeter-wave telescopes.

Contribution

The authors introduce a novel resonator array design with grounding shields and a double-wound geometry that reduces crosstalk from 57% to less than 2%, along with a new measurement technique.

Findings

Crosstalk reduced from 57% to ≤2% with new design.

A circuit model predicts resonator frequency distribution and crosstalk levels.

A new experimental method measures crosstalk without optical setups.

Abstract

Large-scale arrays of Microwave Kinetic Inductance Detectors (MKIDs) are attractive candidates for use in imaging instruments for next generation submillimeter-wave telescopes such as CCAT. We have designed and fabricated tightly packed ~250-pixel MKID arrays using lumped-element resonators etched from a thin layer of superconducting TiNx deposited on a silicon substrate. The high pixel packing density in our initial design resulted in large microwave crosstalk due to electromagnetic coupling between the resonators. Our second design eliminates this problem by adding a grounding shield and using a double-wound geometry for the meander inductor to allow conductors with opposite polarity to be in close proximity. In addition, the resonator frequencies are distributed in a checkerboard pattern across the array. We present details for the two resonator and array designs and describe a circuit model for the full array that predicts the distribution of resonator frequencies and the crosstalk level. We also show results from a new experimental technique that conveniently measures crosstalk without the need for an optical setup. Our results reveal an improvement in crosstalk from 57% in the initial design down to \leq 2% in the second design. The general procedure and design guidelines in this work are applicable to future large arrays employing microwave resonators.