Technology-driven Semiconductor Laser Based Photoconductive Switch

Photoconductive Semiconductor Switches (PCSS) is a new kind of switch combined with laser pulse and photoconductive semiconductor. Because of its advantages, including shorter closing time, higher power, more precise and lower jitter, PCSS has a promising future in the fields of medical Dielectric Wall Accelerator, high power microwave, ultrashort pulse, flash photograph, and so on. This paper develops a new kind of PCSS driving technology based on laser diode, and this driving technology is smaller, cheaper and more convenient.In this paper, firstly, a driving circuit, based on MOSFET, is designed to drive the laser diode. Based on circuit simulation with Pspice, some important circuit parameters are optimized. The rise-time of the output current pulse is1.21ns, and the peak current is adjustable and up to44A.Then, this paper researches on the output of laser diode. The rise-time of the laser pulse is3.1ns and its peak power is75W. Smaller rise-time and higher peak power means shorter turn-on time. The jitter of the laser pulse is0.2ns and the jitter between two laser pulses is about0.3ns or0.4ns, both of them influence the jitter of the PCSS. The laser beam is asymmetric in the horizontal section, and its horizontal angle is larger than the vertical one, resulting in that the relative position between the laser pulse and PCSS is one of the key points to PCSS. What’s more, the PCSS can’t absorb the laser energy completely depending different sizes of the PCSS.An experiment, based on the pulse forming line, is designed to test the PCSS triggered by laser diode. The results show that when the distance between the laser diode and PCSS is about3mm and the light’s position is close to the anode slightly, the PCSS works best. To the opposed-contact PCSS with5mm narrow-gap used in the experiment, the proper working voltage is from16kV to18kV. The PCSS’s jitter is about0.3ns and the average lifetime is about100shots. Higher bias voltage means the PCSS’s better conducting state, but shorter lifetime.Finally, the PCSSs triggered by the laser diodes are tested in the experiments of single Blumlein transmission line and in four stage Blumlein transmission lines, respectively. The switches works well in these experiments, which confirms the feasibility of PCSS drive technology based on laser diode.