Recent Advances in Optically Controlled Discharges

The recent increase in modular pulsed power systems has amplified the potential of optically controlled discharges where stringent synchronization in time is required. This interest has lead to new switching applications and concepts as well as new understanding of the switching process from a fundamental standpoint. The increasing diversity of wavelengths available has necessitated a modification of the generally accepted laser-initiated breakdown mechanism. Advances in high time resolution diagnostics techniques have as well allowed a deeper insight into heretofore conjectured mechanisms. New understanding in optically controlled discharges and new applications since the last review (1977) will be addressed. These include the impact of short wavelength lasers, applications to surface discharges, their application in opening switches including the potential of optogalvanic effects which are of particular significance in diffuse discharges. One additional area of considerable promise is photoconductive switching using intrinsic solid state materials. That advance should be compared to optical control applications on traditional workhorses such as thyratrons. There is no question but that the potential of optically controlled discharges is only beginning to be realized, primarily as a result of improvements in laser versatility and reliability, efficiency of interaction of the optical control energy ( particularly in a resonant mode), demonstrated precise timing and synchronization capability to below a picosecond and improved understanding of the total switching event. Possibilities of optically controlled discharges not yet demonstrated will also be discussed.