Reduced invasiveness of noncontact electrooptic probes in millimeter-wave optoelectronic characterization

We report time-resolved measurements of the invasiveness of LiTa[O.sub.3] external probes in millimeter-wave electrooptic sampling. Using external probe tips at varying distances from a coplanar stripline, we show that invasiveness can be reduced in a noncontact configuration at the expense of measurement sensitivity. In the contact configuration, the risetime can be significantly lengthened by dispersion and signal reflection caused by the probe tip.