Laser power and solar irradiance

This paper presents experience with two accurate and stable detectors of optical radiation: a Scientech disk calorimeter used as a standard for laser power measurement and a Kendall radiometer system (Technical Measurements, Inc.) used as a standard for solar irradiance measurements. The construction, calibration, and maintenance of each detector are first presented both for general interest and to contrast one device used for measuring the power in a collimated, monochromatic laser beam with one used for a diverging beam of white light. Intercomparisons of the two devices are then described, for such intercomparisons provide a valuable check on the accuracy and stability of the two standards. These intercomparisons used first the sun and then a Kr-ion laser as the light source. Subsidiary tests of each detector were required before using the different sources.