A reference calorimeter for laser energy measurements

Abstract

Principles and detailed procedures are described for measuring laser energy and power in terms of electrical energy based on voltage, resistance, and frequency standards. The construction of a small isoperibol calorimeter used for the measurements is described. The calorimeter will accommodate 0.01 to 20 J and 4 × 10^-5 to 1 W cw and is limited to a maximum pulse intensity of 0.1 J/cm². The standard deviation of comparison measurements using two calorimeters and a beam splitter is 0.08 percent when the smaller energy input is not less than 0.3 J. The estimated limits of systematic error for one calorimeter are ± 1.0 percent of the laser energy measured by the calorimeter.