SNSPDs on a Magnesium Fluoride Substrate for High System Efficiency and Ultra-Wide Band

We developed a superconducting nanowire single-photon detector (SNSPD) based on a magnesium fluoride (MgF2) substrate with the aim of producing a high system efficiency (SE) and wideband. The proposed SNSPD on a MgF2substrate could simultaneously provide: 1) low lattice mismatching of the lattice constant between MgF2and superconducting niobium nitride (NbN) films; 2) a low reflection loss (n = 1.37); and 3) a wide transmission band (0.2-7 μm). Based on the designed structure, a simulation indicated that the maximum absorption efficiency of the designed SNSPD on the MgF2substrate is 97%. An SE of 46% at 1064 nm was measured without maximizing the polarization. The SNSPD on the MgF2substrate was examined in a long-haul laser ranging application over four months, expanding the possibilities for application such as for laser ranging of space debris.