As a post-doc in the NIST Mass and Force Group, one of the projects I worked on was linking laser power to force measurements. As light bounces of an object its momentum changes imparting a force on the object, if the optical power is known, then the force can be calculated, or vice versa.

In the realms of very small forces (femto-Newton range) laser power (~100 μW) can be calibrated to a higher accuracy, and force measurements can be improved with optomechanical calibration. See our paper “A self-calibrating optomechanical force sensor with femtonewton resolution” (arXiv version).

At higher laser power (~1W), force measurements have lower uncertainties. To investigate improving optical power measurements we used the NIST EFB to compare laser power to traceable electrostatic forces. This work was published in Metrologia.