Photonic Data Science

For spectroscopic and imaging applications in the sub-mm wavelength band, superconducting radiation sensors are widely used. Thereby, sensor arrays with a rising number of pixels require multiplexing techniques in order to reduce the number of wires leading to the cryogenic stage. The current steering switch (CSS) provides the basis for one kind of promising code division multiplexers. It is composed of two identical superconducting quantum interference devices (SQUIDs) in parallel current paths. Switching one of them from the superconducting into the normal state, controlled by the applied magnetic flux, alters the signal path so they can act as a polarity switch for analog signals. In this work, we describe a method that uses rapid single flux quantum (RSFQ) electronics for controlling these switches. Therefore, their SQUIDs are coupled inductively each to the storing loop of an RSFQ delay flip flop (DFF), so the state of the analog switch can be controlled by means of digital RSFQ signals. As a first step, we show the change in the SQUIDs critical current by the coupled operating digital circuit. For a wider operating range of the CSS, we developed a DFF, which is able to store a larger quantity of magnetic flux to make it possible to apply more flux to the coupled SQUID. For further improvements, we tested asymmetric SQUIDs to reduce the required magnetic flux. The results of simulations and measurements are discussed.