Portable Electrostatic Force Balance for Laser Power Metrology

A new paradigm in laser power metrology has recently evolved. The measurement of photon pressure forces from the reflection of a laser from a high reflectivity mirror provides a means to quantify optical power in a fashion similar to methods used to realize the mass unit in the redefined SI. Because photon pressure forces are typically quite small, an electrostatic force balance (EFB) can be effectively used to interconvert between force and laser power within the International System of Units (SI). In this work, a portable version of the EFB is constructed and tested. The balance will be used to measure a photon pressure equivalent to 10 kilowatts of laser power (approximately 60 micronewtons) with an uncertainty on the order of 0.01%. A preliminary demonstration shows sufficient resolution for the required application.