Background

In 2018 the SI system of units was redefined such that the standard of the kilogram was linked to fundamental constants as opposed to a physical standard. Motivated by this redefinition I participated in studies of alternate calibration procedures for small forces. Specifically, a known laser power can be linked to the force on a highly reflective mirror by the same fundamental constants leveraged in the new definition of the kilogram. Establishing such a standard would significantly reduce the uncertainty of force and mass calibrations at and below the nN and ug levels.

Results

One method of scaling up the amount of force generated per unit of input power is to perform the calibration inside of an optical cavity. An optical cavity is an optical resonator in which light reflects multiple times before exiting the cavity. An example of such a cavity formed out of optical fibers is shown in the corresponding figure. Each end of the fiber was shaped into a curved surface using a laser manufacturing process and then coated with a highly reflective optical coating. One of the fibers was placed on a mechanical flexure for monitoring force. Such a configuration enabled building a transfer standard linking laser power and force.