Ultrafast high-field carrier transport in a GaAs photoconductive switch

Abstract

Utilizing 18 fs optical pulses, field screening, and carrier dynamics which occur in the high-field region of an edge-illuminated coplanar transmission line are investigated. It is found, through the use of transient pump-probe reflectivity measurements, that the ballistic acceleration of carriers and subsequent field screening dominate the ultrashort electrical pulse generation for an edge-illuminated photoconductive switch. The formation of an instantaneous macroscopic polarization and phonon-plasmon modes are also observed. In addition, lattice and plasmon contributions to the field screening are found to be highly dependent on the excitation position within the gap. The measurements suggest that sub-100 fs electrical pulses can be generated.