Femtosecond carrier dynamics in an asymmetrically excited GaAs photoconductive switch

We present a detailed analysis of the field screening and carrier dynamics which exist in the high-field region of an asymmetrically excited coplanar transmission line. Through time-resolved reflectivity measurements, it is f ound that the ballistic acceleration of carriers, and subsequent field scre ening, dominate the ultrashort electrical pulse generation. In addition, th e formation of an instantaneous macroscopic polarization and the creation o f coherently coupled plasmon-phonon modes are found to effect the electric field screening response. The results are in agreement with the field scree ning picture of edge-illuminated photoconduction and suggest that pulses as short as 110 fs can be generated. (C) 2001 American Institute of Physics.