An MOCVD grown InP based optothyristor has been fabricated and tested for high power pulsed switching applications. To increase the power handling capability, the thyristor structure has a 250 μm thick Fe doped semi-insulating (SI) InP sandwiched between two pn junctions of a conventional thyristor. The turn-on of the thyristor is controlled by optical illumination on the SI-InP which creates a high concentration of electron and hole pairs. More than 1,100 V device hold-off voltage has been observed and over 66 A switched current has been realized with a di/dt rating of 1.38×1010 A/s. The switched current as a function of switch voltage and of optical illumination power has also been studied. Comparison with the switching characteristics of a bulk SI-InP photoconductive switch clearly indicates the advantage of this optothyristor in terms of power handling capability.