Multi-facility comparison of InGaAs trap detector responsivity for optical fiber power

The absolute responsivity of an optical detector in a trap configuration has been investigated in the interest of high-accuracy fiber-coupled measurements for commercial optical fiber power meters and fiber-coupled single-photon detector calibrations. The highest accuracy measurements of optical power are typically undertaken free space and then disseminated for fiber-coupled measurements with some additional uncertainty. At the lowest uncertainty, the difference between free-space and fiber-coupled optical power measurements can be significant. We present here a complete evaluation of multiple trap detectors consisting of two InGaAs photodiodes and a concave mirror. This evaluation includes fiber-based responsivity at discrete laser wavelengths measured both with cryogenic and room temperature standards (diverging input beam), free-space absolute spectral responsivity over a broad wavelength range (converging beam), free-space responsivity at discrete laser wavelengths (collimated), linearity, and spatial uniformity.