A Frequency Sweeping Readout System for Kinetic Inductance Detectors Based on Submillimeter Radio Astronomy

We have been developing a superconductive detector array for terahertz astronomical observation using Microwave Kinetic Inductance Detector (MKID) technology. MKID is accomplished by making a strip of superconductor part of a microwave resonant circuit, and monitoring the phase and amplitude of a probe signal transmitted through the resonator. Frequency-domain multiplexing will allow up to thousands of resonators to be read out through a single line. We developed a 600-pixel 220 GHz detector array and a 102-pixel 440-GHz detector array. We have developed a new scheme readout system for the detector arrays, and which uses a frequency-sweeping probe signal instead of a fixed-frequency probe signal. This scheme enables us a direct measurement of the changed resonance frequency after optical loading.