Effect of Optical Pulsewidth on Transition From Linear to Nonlinear Mode of GaAs PCSS

The transient characteristics of the GaAs photoconductive semiconductor switch (PCSS) are determined by photon injection, absorption, recombination radiation, and subsequent photo-generated carriers' generation and transport. The optical pulsewidth determines the injection rate of incident photons and then affects the closing state of the PCSS. Five optical pulses with different pulsewidths but the same incident power are used to investigate the transient output characteristics of GaAs PCSS. Results show that the narrower trigger optical pulsewidth is prone to induce the nonlinear mode. Furthermore, 2D simulation indicates that the electron bunch phenomenon is more pronounced due to the rapid evolution of the electric field under the trigger of the narrower pulse. It enhances impact ionization in turn and ultimately boosts the GaAs PCSS to transform from linear to nonlinear mode.