Abstract

The use of ultrafast laser pulses to activate photoconductive (PC) sampling gates has led to the development of electrical measurement devices and probes with high temporal, spatial, and voltage resolution [1-6]. In the work reported here, a 1-μm-thick epitaxial layer of low-temperature-grown GaAs (LT-GaAs) having a 1-ps carrier relaxation time has been mounted on the end of a single-mode optical fiber. With an interdigitated switch defined on the LT-GaAs, this structure forms a photoconductive-sampling probe capable of measuring microvolt-amplitude electrical waveforms through insulating passivation layers. This flexible, micro-machined PC probe, which does not require optical realignment after repositioning, has achieved an ultrahigh sensitivity through reduction of parasitic capacitance and leakage current. This allows measurement of fringing electric fields from a device or circuit under test without draining away any charge.

© 1996 Optical Society of America