Method of Extending the Range of Measurements of the Energy of the Secondary Standard during Calibration and Verification of Laser Joulemeters

The paper analyzes the problem of a mismatch between the measurement ranges of the laser radiation energy of the State secondary standard of the unit of energy 2.1.ZZA.0095.2017 and the calibrated instruments for measuring low laser beam energy levels (joulemeters), which occurs during calibration/verification. A method is proposed for extending the measurement range of the laser radiation energy of a secondary standard during calibration and verification of the laser joulemeters. The extended range of the laser beam energy values is 1·10^–9–5·10^–1 J. A metrological traceability of the measurements from joulemeters to the secondary standard was achieved by a two-stage attenuation of the source radiation from the standard. The first attenuation stage represents a set of neutral filters, and the second one — an integrating sphere.

The method of extending the energy measurement range of the secondary standard consists in dividing the algorithm of its operation into two main modes: standard certification and joulemeter calibration/verification. The main modes consist of four stages. At each stage, the secondary standard is certified, and the joulemeters are calibrated/verified in one of four separate ranges, which overlap pairwise under the laser radiation energies having similar orders of magnitude, and collectively cover the required range. A functional diagram of an upgraded secondary standard of the unit of energy has been developed, which implements the proposed method. A detailed analysis of the modes of operation of the upgraded secondary standard in the extended range of measured energies is provided. Calculation expression were obtained, which confirm the feasibility of the method.