Photoconductive Semiconductor Switches: Laser Q-switch Trigger and Switch-Trigger Laser Integration

This report provides a summary of the Pulser In a Chip 9000-Discretionary LDRD. The program began in January of 1997 and concluded in September of 1997. The over-arching goal of this LDRD is to study whether laser diode triggered photoconductive semiconductor switches (PCSS) can be used to activate electro-optic devices such as Q-switches and Pockels cells and to study possible laser diode/ switch integration. The PCSS switches we used were high gain GaAs switches because they can be triggered with small amounts of laser light. The specific goals of the LDRD were to demonstrate: 1) that small laser diode arrays that are potential candidates for laser-switch integration will indeed trigger the PCSS switch, and 2) that high gain GaAs switches can be used to trigger optical Q-switches in lasers such as the lasers to be used in the X-1 Advanced Radiation Source and the laser used for direct optical initiation (DOI) of explosives. The technology developed with this LDRD is now the prime candidate for triggering the Q switch in the multiple lasers in the laser trigger system of the X-1 Advanced Radiation Source and may be utilized in other accelerators. As part of the LDRD we developed a commercial supplier. To study laser/switch integration we tested triggering the high gain GaAs switches with: edge emitting laser diodes, vertical cavity surface emitting lasers (VCSELs), and transverse junction stripe (TJS) lasers. The first two types of lasers (edge emitting and VCSELs) did activate the PCSS but are harder to integrate with the PCSS for a compact package. The TJS lasers, while easier to integrate with the switch, did not trigger the PCSS at the TJS laser power levels we used. The PCSS was used to activate the Q-switch of the compact laser to be used in the X-1 Advanced Radiation Source.