Optimized Microwave LEKID Arrays for High-Resolution Applications

High-resolution applications demand a strong increase in number of pixels of detector arrays. In terms of the lumped-element kinetic inductance detector, this requires a detailed knowledge of the microwave properties of each single pixel; moreover, the unwanted interaction (cross-talk) between them has to be examined and eliminated. In this paper, the basic microwave properties of lumped-element kinetic inductance detector structures were investigated. Simulations demonstrate the influence of the embedding design parameters, e.g., orientation and coupling distances, in respect of the microwave behavior. In addition, different array arrangements to increase the number of pixels and to identify possible reasons causing unwanted cross-talk were examined. For this purposes several samples in niobium thin film technology on silicon substrates were designed, fabricated and characterized. Loaded quality factors QL up to 3 000 at 4.2 K were achieved. The results of the simulations and measurements of small and large arrays will be presented and discussed.