Terahertz Power Calibration Using Absolute Reference Calorimeter

Here, we demonstrate an accurate terahertz (THz) power calibration toward tens of nanowatt levels at room temperature. A power reference standard based on a calorimeter with extremely low noise is realized by introducing vacuum insulation panels utilized for thermal insulation. The standard provides a measurement capability of 26.7 nW with the expanded uncertainty of 4.2% (k = 2) at 1 THz. The direct-comparison calibration of a commercially available power meter is performed by considering its detectable power levels using the standard. A thermopile-type power meter is used as the device under test, and its calibration factors are determined at 1 and 1.5 THz over a power-level range of 0.66-1.56 mu W. We evaluate the measurement uncertainties of the calibration and find a relative expanded uncertainty of 4.8-9.0% (k = 2). (c) 2019 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.