![]() This causes the number of functional pixels of the NIKA2 260 GHz array to decrease from 84% to 70% under sky background illumination. 3 Intrinsic variation in these parameters gives rise to a large, uncontrolled deviation of the resonance frequency from the design values, leading to many frequency collisions. For example, the NIKA2 260 GHz array uses a 18 nm thick Al film with a 4 μ m inductor width. 8 Its low kinetic inductance and resistivity, however, impose thin films (<80 nm) and narrow linewidths (<4 μ m), in order to optimize sensitivity and optical coupling. Aluminum is commonly used in LEKID design for its easy fabrication, low gap frequency, and long quasiparticle lifetime. Frequency collision is usually caused by the variation of material parameters, such as the film thickness, the superconducting transition temperature, and the resonator dimensions across the wafer. This affects the number of pixels that are useful for astronomical observations. When a collision happens, the readout tone may pick up a signal from a nearby resonance. As the number of pixels per feedline increases, resonance frequency collision between adjacent resonators becomes problematic. In practice, the multiplexing factor per readout line depends on the readout bandwidth, resonance frequency spacing, and resonance width, which is usually limited by background radiation for ground-based observations. Their intrinsic frequency multiplexing property makes LEKIDs suitable for large detector arrays. Lumped element kinetic inductance detectors (LEKIDs) have been widely developed for astronomical observations 1–7 in the last decade. With the improvement in yield, the capacitor trimming technique may benefit future large-format LEKID arrays. The mapping yield, measured under a 110 K background, is improved from 69% to 76%, which can be further improved to 81% after updating our readout system. The yield of the trimming process is found to be 97%. Using the capacitor trimming technique, the fractional deviation is decreased by a factor of 14. Using the measured resonator dimensions and film thickness, the fractional deviation can be explained within ± 25 × 10 − 3, whereas the residual deviation is due to variation of electric film properties. kilo-pixel lumped-element kinetic inductance detector (LEKID) array using optical mapping. Here, we study the resonance frequency deviation of a 4-in. However, fabrication imperfections usually give rise to resonance frequency deviations, which create frequency collision and limit the array yield. One of the advantages of kinetic inductance detectors is their intrinsic frequency domain multiplexing capability.
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