Traceable Measurements of CW and Pulse Terahertz Power With Terahertz Radiometer

We report on traceable measurements of continues wave (CW) and pulse terahertz (THz) power with a THz radiometer. A sensitive THz radiometer with a broad bandwidth, high absorbance coating as absorber was fabricated. The absorber has an absorbance of higher than 99% in both 0.1 THz-3.0 THz region and in visible laser wavelengths range, which allows for an absolute measurement of THz radiation power and traceability to the International System of Units (SI). The uncertainty budget of CW THz power measurement with this radiometer is discussed, and the measurement results agreed excellently in the first international THz power comparison. Due to its high sensitivity and flat spectral responsivity, a pulse THz radiation from a THz time-domain spectrometer (THz-TDS) was absolutely measured with this radiometer.