Cryogenic LED pixel-to-frequency mapper for kinetic inductance detector arrays.

We present a cryogenic wafer mapper based on light emitting diodes (LEDs) for spatial mapping of a large microwave kinetic inductance detector (MKID) array. In this scheme, an array of LEDs, addressed by DC wires and collimated through horns onto the detectors, is mounted in front of the detector wafer. By illuminating each LED individually and sweeping the frequency response of all the resonators, we can unambiguously correspond a detector pixel to its measured resonance frequency. We have demonstrated mapping a 76.2mm 90-pixel MKID array using a mapper containing 126 LEDs with 16 DC bias wires. With the frequency to pixel-position correspondence data obtained by the LED mapper, we have found a radially position-dependent frequency nonuniformity of ≾1:6% over the 76.2mm wafer. Our LED wafer mapper has no moving parts and is easy to implement. It may find broad applications in superconducting detectors and quantum computing/information experiments. [ABSTRACT FROM AUTHOR]