Comparison of the laser power and total irradiance scales maintained by the national bureau of standards.

The paper describes an intercomparison of the instrument used to realize and maintain the NBS laser power and energy scale with the instrument used to realize and maintain the upper end of the NBS total irradiance scale. The intercomparison was conducted by performing simultaneous measurements of the average power from a cw kyrpton laser with both instruments. The procedure and apparatus of the comparison are described. The measured difference between the two instruments was well within the ~1.5% limit of error associated with the intercomparison.