Influence of Inhomogeneity of NIR-Photodiodes on Calibrations at 1 047 nm

The inhomogeneity of responsivity of photodiodes limits the accuracy of their calibration. Inhomogeneity measurements of a Ge and InGaAs photodiode and of an integrating sphere equipped with an InGaAs photodiode are shown as examples. An evaluated set of inhomogeneity coefficients is proposed as a more advantageous and objective measure than original data matrices or their graphical presentation. The PTB facility for the calibration of transfer standards at the wavelength λ = 1 047 nm is described. This takes inhomogeneity effects into account resulting in a relative transfer uncertainty of less than 10^-4.