International comparison on ultrafast waveform metrology

We report on the first international comparison in ultrafast waveform metrology. To this end, the frequency and time responses of a photodiode with a nominal bandwidth of 100 GHz have been measured by several National Metrology Institutes (NMIs) during the last two years. An overall good agreement between the different measurement techniques is obtained. However, certain features in the frequency- and time-domain responses are not reproduced by all NMIs, calling for additional studies and comparisons.