Photonic Systems Brown Bag Seminar

Thursday, April 14, 2005, at 12 noon                            RLE Haus Room, 36-428

Superconducting Nanowire Single-Photon Detectors

Joel K. Yang

The ability to detect a single photon electrically was first demonstrated in the photomultiplier tube in 1940. Since then, several novel applications, for example quantum cryptography, have emerged that rely on high-speed single photon detectors (SPDs). Superconducting nanowire SPDs have been reported to detect single photons and proposed to have GHz counting rates—several orders of magnitudes faster than has been demonstrated by other types of SPDs to date. The nanowire SPD consists of a 4-nm-thick, ~ 100-nm-wide superconducting NbN wire, and operates at 4 K or below. We have recently developed a fabrication process for patterning a thin film of NbN using electron-beam lithography and hydrogen-silsesquioxane (HSQ) resist. With this technique, we were able to achieve uniform wire widths at the sub-100-nanometer length-scale, with the smallest devices made being as narrow as 25-nm-wide. Detectors fabricated with this process exhibited electrical characteristics comparable to those of the un-patterned material. In this seminar, I will explain the basic principle of operation of the detector and describe the fabrication process for the nanowires. I will also present preliminary electrical and optical test results of the nanowire SPD.