Photoconductive nanosecond pulse generation utilizing radial transmission lines

A nanosecond, kilovolt pulse generator utilizing a radial transmission line was investigated. The device incorporates a gallium arsenide, photoconductive switch to connect the radial line to the coaxial output. Identical gridded electrodes are used on opposite sides of the switch. Switching is achieved with a 75-ps-wide pulse from a mode-locked Nd:YAG laser. In addition to the radial design, a quasi-radial structure was also investigated, in which improvements in rise time and pulsewidth were achieved at the expense of voltage gain. For the same charging voltage of 9.2 kV, the radial device delivered a 10-kV, 1.3-ns-wide pulse, while the quasi-radial device gave a 6-kV, 500-ps-wide pulse. An integrated pulser design in which the switch and the dielectric medium between conducting planes are combined into a single semi-insulating GaAs wafer is described. The potential advantages of such a device are discussed