A fiber-mounted, micromachined photoconductive probe with 15 nV/Hz(1/2) sensitivity

We report the performance of a micromachined, photoconductive-sampling probe that is fabricated on low-temperature-grown GaAs and mounted on a single-mode optical fiber. The epitaxial probe has a temporal resolution of 3.5 ps, a spatial resolution of 7 mu m, and a sensitivity of 15 nV/(Hz)(1/2) when integrated with a high impedance, junction field-effect transistor source follower. The fiber, which couples short laser pulses to the interdigitated detector pattern on the probe, also provides flexible support and mobility. The probe's compact cross section makes it ideal for applications as an internal-node, picosecond-response, photoconductive sampling probe or wave form launcher for test and characterization of integrated circuits. (C) 1996 American Institute of Physics.