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PTB sets benchmarks in terahertz radiometry


A few years ago, the spectral range between infrared radiation and microwaves was still called the “THz gap” in radiometry, because measuring techniques for frequencies around 1 THz were poorly developed. Then it became clear that THz radiation would gain in importance in process monitoring and safety engineering and PTB, with its THz Radiometry Working Group, decided to systematically develop the quantitative measurement of THz radiation and to pass it on to clients all over the world in the form of a calibration service for frequencies from 1 THz to 5 THz during the last couple of years.

THz detectors at PTB’s calibration facility

In 2015, these activities arrived at another very important result with the successful performance of an international pilot comparison on THz power measurement. The other two participants were the national metrology institutes of China and the USA which wanted to compare their THz radiometers with PTB’s. The excellent agreement resulting from this comparison has allowed PTB to extend its calibration services down to 0.7 THz with optical methods. New THz detectors have enabled this additional step; these were developed in collaboration with a German manufacturer over the past two years and have now been enhanced, so that the THz power of a time domain spectroscopy (TDS) system could be measured absolutely for the first time. All around the world, TDS systems are the “workhorses” in the field of THz; they are on the verge of being used for industrial applications and are therefore the main topic of the first VDI/VDE guidelines of the recently established VDI Committee “THz Systems”.