Picosecond Electro-Optic Sampling

Abstract

The electro-optic sampling technique is a new characterization technique based on short optical pulses (picosecond or femtosecond) and the electro-optic effect. With this technique, electrical waveforms have been characterized with temporal resolution of less than 300 fs, corresponding to a 1 THz bandwidth. Since its inception in 1982, this method has been adapted to a variety of measuring situations, leading to a large number of embodiments. The electro-optic sampling was first used to study the dispersion of picosecond electrical pulses on transmission lines. Using a superconducting transmission line, it has been recently shown that conduction losses can be defeated’and single picosecond pulses propagated over a few millimeters. Additionally, Ultrafast transistors have been tested with single picosecond resolution that is, the transistor response was time-resolved as the gate was pulsed using a step function with a picosecond rise time. MESFET, TEGFET, and permeable base transistor (PBT) responses have been studied, and switching times as low as 5 ps have been directly measured for the PBT. Because GaAs exhibits the Pockels effect, the GaAs components and circuits can be directly probed in a noninvasive way. We will review the principle of electro-optic sampling in its various embodiments and applications to device and circuit characterization, as well as the direct investigation of velocity overshoot and ballistic and resonant tunneling transport.