Generation Of Steady And Jitter-Free Ultra-Fast Electrical Pulses With Photoconductive Switches

Based on the research results of SI-GaAs photoconductive switches, combined with the Project supported by the National High Technology Development Program of China (Grant No. 863-804-2002AA842211) and the National Natural Science Foundation of China (Grant No. 50077017), according to the need of switches with ultra-fast, accurate and synchronous control, combined the theory analysis with experiment, the paper studies the characteristics of the stability of pulse voltage amplitude, jitter-time ultra-fast electrical pulse from photoconductive switches. The main results obtained are as follows:1. The ultra-fast characteristics of photoconductive switches were mainly determined by the optical pulse width and the carrier lifetime of the chip material. The rise time of output electrical pulse can be improved by decreasing the optical pulse width and selecting the chip materials with shorter lifetime can decrease it's fall time, so in order to achieve fast switching, the short optical pulse should be used to trigger photoconductive switches and the material of the short carrier lifetime should be chosen.2. The results also showed that the output electric pulse width from thephotoconductive switches was affected by the optical pulse energy and biased voltage, decreasing the optical energy and increasing the biased voltage can reduce the output pulse width to a certain extent. The reason was examined.3. When the exterior circuit was certain, the output voltage was mainly determined by the biased, but it was also affected by the chip materials, the gap length on the device resistance and the optical pulse energy to a certain extent. The ultra-fast electric pulse with certain voltage amplitude can be obtained by controlling switch trigger condition and optimizing switch design.4. The theory and experiment results showed that the electric pulse with steady voltage amplitude could be outputted when the photoconductive switches worked in the saturated situation. Decreasing the gap length on the device resistance or increasing the optical pulse energy can produce the ultra-fast electric pulse with steady voltage amplitude, which is not related to the change of the optical energy.5. The photoconductive switches responded to the optical signal with pico-second rate so that it can kept the pico-second triggered jitter-time. The theory analysis results indicated the characteristic was determined by the parameters of the chip materials, so in order to obtain the ultra-fast electrical pulse with pico-second jitter-time, the proper parameters should be chosen.6. The ultra-fast and steady voltage amplitude characteristics of output electrical pulse from the lateral photoconductive semiconductor switches, which were fabricated with SI-GaAs by all solid insulation protection and triggered by nanosecond, pico-second and femto-second laser pulse, were studied. The steady ultra-fast electric pulse, whose change of amplitude was less than 1.2% and the triggered jitter-time was difficulty to discern, and the ultra-fast electric pulse whose pulse width was 133ps and the rise time was 83ps were obtained in the experiment. The result will provide information for realizing the application of the ultra-fast, accurate and synchronous control.