Direct implementation of a frequency-programmable Josephson voltage standard to provide an SI traceable optical power scale

Abstract

We have developed a technique to determine the electrical substitution power of a cryogenic optical radiant power detector, that directly implements a frequency-programmable Josephson voltage standard (FPJVS), thus reducing the traceability chain. The optical power detector and the Josephson voltage reference are combined inside a common cryogenic environment. We demonstrate the practicality of the technique by using a FPJVS to apply a known voltage across the resistive heater of a standard NIST cryogenic planar radiometric detector. The power applied to the detector heater is calculated from a measurement of the heater resistance and the known applied voltage. The FPJVS dc bias current source supplies dc current to the resistive heater. In this demonstration, the standard uncertainty of the substituted electrical power is limited by the uncertainty of the electrical heater four-wire resistance measurement at 4 K. The uncertainty due to the resistance measurement is 1 part in 105 out of a total uncertainty of 1 part in 104 (k = 2) on the 1 mW optical power measurement. We aim to develop the technique, to provide traceability to the International System of Units for the picowatt power measurement of single-photon emitters such as quantum dot sources.