A Method for Generating High-Current, Ultrashort, and Square-Wave Pulses Based on a Photoconductive Switch Operating in the Quenched High-Gain Mode

摘要

The quenched high-gain mode of semi-insulation photoconductive semiconductor switch (PCSS) is a new operating mode. It has many advantages over the traditional modes, such as ultrafast rise time (mainly determined by the laser), high power, short pulsewidth, ultrafast fall time (mainly determined by the carrier lifetime), and so on, making it possible to generate high-power ultrashort pulses. To approximate square waveforms, a method for controlling PCSS is presented in this paper. First, a physical model of PCSS is established, which depends on the electronic negative differential mobility, the high-voltage impact ionization, the characteristic of luminous current filament, and the continuity equation of current. Second, constraint equations of circuit parameters are deduced to hold the dynamic balance of the tendency of current to increase or decrease for obtaining the flat top of output pulses. Finally, the control circuits of GaAs:EL2 PCSS operating in the quenched high-gain mode are designed, the parameters of which are the solutions to the constraint equations. The experimental results demonstrate that the method can generate square-wave pulses of kiloampere amplitude and about 50-ns pulsewidth on a subohm load.