Laser power-meter comparison at far-infrared wavelengths and terahertz frequencies

We have evaluated the responsivity of seven different thermal detectors compared to an electrically calibrated photoacoustic reference detector at 119 µm (2.5 THz) and 394 µm (0.76 THz) laser wavelengths. Among the thermal detectors is an electrically calibrated thermopile having a vertically aligned carbon nanotube array as the absorber. We document the uncertainty contributions attributable to the photoacoustic reference detector along with a definition of a calibration factor based on the measurement protocol. The expanded relative uncertainty (k = 2) and a calibration factor of each detector are tabulated.