Analytical modelling of a linear GaAs photoconductive switch for short pulse excitation

The carrier density for a photoconductive switch is described by a single linear rate equation that is dependent on the time-varying incidental optical source. Typical solutions to this equation assume the optical source as a square pulse with instantaneous rising and falling edges; thus simplifying the solution to the problem. This paper presents an analytical solution to the rate equation with a short, Gaussian optical profile. This solution leads to a PSpice model for the photoconductive switch using a time-varying resistor model. The time-dependent conduction profile is numerically generated by the analytical solution and placed in a table definition for the time-varying resistor model. This paper discusses the analytical aspects of the solution and presents the PSpice model results. Analytical and experimental results are compared.