  The concept of the radio-frequency superconducting nanowire single-photon
detector (RF-SNSPD) allows frequency-division multiplexing (FDM) of the bias
and readout lines of several SNSPDs. Using this method, a multi-pixel array can
be operated by only one feed line. Consequently, the system complexity as well
as the heat load is significantly reduced. To allocate many pixels into a small
bandwidth the quality factor of each device is crucial. In this paper, we
present an improved RF-SNSPD design. This new design enables a simple tuning of
the quality factor as well as the resonant frequency. With a two-pixel device
we have demonstrated the operation without crosstalk between the detectors and
showed the time, spatial and photon number resolution. Thereby a single pixel
requires only a bandwidth of 14 MHz.
