Fabrication of superconducting nanowire single-photon detectors by nonlinear femtosecond optical lithography

摘要

This paper describes a new approach to the fabrication of superconducting nanowire single-photon detectors from ultrathin NbN films on SiO2 substrates. The technology is based on nonlinear femtosecond optical lithography and includes direct formation of the sensitive element of the detector (the meander) through femtosecond laser exposure of the polymethyl methacrylate resist at a wavelength of 525 nm and subsequent removal of NbN using plasma-chemical etching. The nonlinear femtosecond optical lithography method allows the formation of planar structures with a spatial resolution of similar to 50 nm. These structures were used to fabricate single-photon superconducting detectors with quantum efficiency no worse than 8% at a wavelength of 1310 nm and dark count rate of 10 s(-1) at liquid helium temperature.