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A numerical model for optically triggered switching in bulk GaAs is presented. First, a one-dimensional model is described and calculated behavior compared to experimental observations. Results from the one-dimensional model are not consistent with observed switching behavior. The model is then modified to include filament formation. Results from the modified model agree qualitatively and quantitatively with experimental data. Details of the dynamic behavior of the device are shown and a unified picture of the switching phenomenon presented. On the basis of the agreement of the numerical model and experimental observation it is concluded that switching is a result of localized impact ionization creating a conductive filament channel through the bulk material.

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A multigigahertz microwave signal was generated and up-converted in a GaAs substrate coplanar strip line. Two 630-nmwavelength laser pulses-one with a normal wavefront, another with a titled wavefront-were respectively used to generate and frequency up-convert the signal. The relativistic plasma front, induced by the tilted optical wavefront, frequency up-shifts the counter-propagating electromagnetic wave via the Doppler effect. When the speed of the plasma front was about 0.4 times the speed of electromagnetic wave in the coplanar strip lines, the experiments showed that the fall time of a step signal decreased more than 30% after the reflection. Given the bandwidth limitations of the data acquisition system, it is possible that a factor of 2 increase was achieved. A transmission line model was employed to simulate this process. The simulation results were consistent with experimental observations. Using coplanar strip lines on a GaAs substrate for microwave signal compression device has the advantage of a high reflection coefficient, frequency tunability, small laser trigger energy, and all-solid-state construction, making this technique suitable for impulse radar applications.