First CASP EFRC Seminar
Superconducting Devices for Detection of Single Photons
Dr. Sae Woo Nam
National Institute of Standards and Technology (NIST), Boulder, CO
Wednesday, February 10, 10am
Chemistry Division Auditorium, TA-46, Bld. 535, Rm. 103
There is increasing interest in using superconducting optical photon detectors in a variety of applications. These applications require detectors that have extremely low dark count rates, high count rates, and high quantum efficiency. I will describe our work on two types of superconducting detectors, the Superconducting Nanowire Single Photon Detector (SNSPD) and superconducting Transition-Edge Sensor (TES). An SSPD is an ultra-thin, ultra-narrow (nm scale) superconducting meander that is current biased just below its critical current density. When one or more photon is absorbed, a hot spot is formed that causes the superconductor to develop a resistance and consequently a voltage pulse. By exploiting the sharp superconducting-to-normal resistive transtion of tungsten at 100mK, TES detectors give an output signal that is proportional to the cumulative energy in an absorption event. This proportional pulse-height enables the determination of the energy absorbed by the TES and the direct conversion of sensor pulse-height into photon number. I will discuss our progress towards developing detectors with quantum efficiencies approaching 100% as well as describe several experiments and applications that are enhanced by using these detectors.