Improved Spectral Responsivity Scales at the NPL, 400 nm to 20 μm

Two spectral responsivity scales have been established at the National Physical Laboratory, UK. High quantum efficiency silicon photodiodes have been used to establish a continuous spectral responsivity scale for the spectral region 400 nm to 920 nm. The scale can be disseminated by the NPL with an uncertainty of ±0,1%. Pyroelectric detectors fitted with a reflecting hemispherical cavity have been used to establish a spectral responsivity scale for the spectral region 1 μm to 20 μm. This scale has an uncertainty of less than ±1,6%.