A detector combining quantum and thermal primary radiometric standards in the same artefact

We present the concept of a dual-mode primary standard cryogenic detector, utilizing a predictable quantum efficient silicon photodiode, and demonstrate the behaviour of the detector from room temperature down to 30 K. The detector absorbs visible radiation generating either heat or photocurrent, dependent on the selected mode of operation. In effect, this detector links optical power to fundamental constants through the two different routes of operation in the one artefact. Forward biasing of the photodiode is used in lieu of resistive heating to provide the electrical substitution power. The detector has a thermal time constant of 50 s and a sensitivity of 1.39 K mW−1. Using an LED source, we measure equivalence between the two modes of operation of 1.5% at 50 K, limited principally by our knowledge of the wavelength of the emitted radiation of the source.