Subpicosecond sampling using a noncontact electro-optic probe

This paper discusses a theoretical as well as experimental study of the performance of electro-optic sampling using a noncontact electro-optic probe, i.e., external electro-optic sampling. Sensitivity, temporal resolution, and the capacitive loading effect of this system are calculated by analysis of a static electric field coupled to an electro-optic crystal placed in close proximity to transmission lines such as microstrip lines and coplanar strips. Full-wave analysis is also applied to investigate effect of the electro-optic crystal on the transient property of high-speed electrical signals. Based on these analytical considerations, we have developed an external electro-optic sampling system using precise probe-positioning technology, which improves the measurement reproducibility. A temporal resolution of 0.5 ps and a spatial resolution of 1 μm are confirmed with this system.