Abstract: In this paper, experiments of a lateral semi-insulating GaAs photoconductive semiconductor switch triggered by nano-second and pico-second and femto-second laser pulse are reported. The switches have all-solid-state insulated by multi-layer transparent dielectrics. Dark insulating intensity of the 8 mm-gap GaAs switch reached to 30kV. Jitter-free current wave form of the 3 mm-gap and 8 mm-gap GaAs switches were observed when triggered by the laser pulse. The current could be as high as 560A when the 3 mm-gap switch was under the voltage of 2 kV and triggered with 8 ns and 1.2 mJ laser pulse. The same device also revealed good temperal characteristics when trigger with pico-second laser and 108 repeat frequency laser pulse strings. The rising time the 3 mm-gap switch response is less than 2