Modeling of terahertz radiation from biased photoconductors: transient velocity effects.

We include transient carrier velocity dynamics in a model describing the terahertz radiation from a large-aperture, biased photoconductor triggered by an ultrashort optical pulse. Waveforms of the radiated electric field are calculated as a function of optical excitation fluence and bias field. The model is applied to terahertz generation in biased GaAs photoconductors.