Time-Tagged Multiplexing of Serially Biased Superconducting Nanowire Single-Photon Detectors

We present a concept for a time-tagged multiplexed readout of several SNSPD detector elements for ultra-short pulsed laser applications. The detector elements were coupled in an array by a superconducting delay line giving each detector element a temporal signature. The complete detector chain is biased by one bias supply. The patterning concept and the first experimental proof of principle are demonstrated on 2 detector element arrays with delay times of 86 and 156 ps made from a 5 nm NbN film on sapphire. We discuss the propagation delay of such a delay line taking the geometric and kinetic inductance into account. We show that mainly the normal conducting propagation velocity defines the delay time of the delay line and that the inductance dependent response pulse width currently limits the maximum number of detector elements.