Optimized LEKID Structures With Low Crosstalk for Large Detector Arrays

By using LEKIDs the prospect rises to multi-pixel arrays with an extremely small footprint. Moreover, these arrays have the advantage of frequency-division multiplex readout method (FDM). However, the increase of packing density of LEKIDs leads to an increase of crosstalk between adjacent pixels and complicates the readout process significantly. In this paper, we present a newly developed LEKID structure with reduced crosstalk and present their improved performance in terms of equally spaced resonance frequencies within an array. Thus, the array can be realized with a large number of pixels in a small analog readout bandwidth. We present simulation and measurement results of various linear arrays with 5 pixels, which are constructed with the new LEKID structures. When designing the resonance frequencies importance was attached to an equal spacing between the resonance frequencies at around 6 GHz within our available analog readout bandwidth of 400 MHz. The samples were fabricated in niobium thin film technology on silicon and sapphire substrates and then measured at liquid helium temperatures.