Terahertz Laser Power Measurement Comparison

A comparison of terahertz (THz) laser power measurements was undertaken among three national metrology institutes. At two laser frequencies, 2.52 THz (119 μm) and 0.762 THz (394 μm), a power level of approximately 3 mW was compared at one place at one time by means of national standard THz detectors, which had been calibrated by each participant at their own metrology institute beforehand. The measurements took advantage of the power stability and Gaussian beam profile of the THz radiation source, consisting of a molecular gas laser pumped with a line-tunable CO
₂
laser at the THz detector calibration facility of Physikalisch-Technische Bundesanstalt. A reference value was determined as weighted average of the measurement results with a maximum weight obtained from the arithmetic mean of the uncertainties stated by the participants. All measurement results agreed with the reference value and to each other within the stated expanded uncertainties.