Meta-study of laser power calibrations ranging 20 orders of magnitude with traceability to the kilogram**This work of the U.S. Government is not subject to U.S. copyright.

Abstract

Laser power metrology at the National Institute of Standards and Technology (NIST) ranges 20 orders of magnitude from photon-counting (103 photons s−1) to 100 kW (1023 photons s−1 at a wavelength of 1070 nm). As a part of routine practices, we perform internal (unpublished) comparisons between our various power meters to verify correct operation. Here we use the results of these intercomparisons to demonstrate an unbroken chain tracing each power meter’s calibration factor to the NIST cryogenic radiometer (our lowest uncertainty standard, whose SI traceability is established through the volt and ohm units). This yields the expected result that all the NIST primary standard measurement techniques agree with each other to within their measurement uncertainty. Then, these intercomparison results are re-mapped to describe the agreement of the various techniques with our radiation-pressure-based power measurement approach, whose SI traceability is established through the kilogram. Again, agreement is demonstrated to within the measurement uncertainty. This agreement is reassuring because the measurements are compared with two entirely different traceability paths and show expected agreement in each case. The ramifications of this agreement as well as potential means to improve on it are discussed.We demonstrate SI measurement traceability of our single-photon power measurement through the kilogram with less than 3% relative expanded uncertainty (obtained for a coverage factor k = 2 defining an interval having a level of confidence of approximately 95%).