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 presented at CPEM 2016 (Proceedings paper).