High-Speed Diagnostic of Temperature and Intensity Variation on Diode-Laser Facets

In this STTR project, Science Research Laboratory (SRL) and Boston University Photonics Center (BU Photonics) will develop a revolutionary optical technology for detecting localized increases in temperature on time scales ranging from nanoseconds to microseconds. Localized diode heating is a critical factor limiting the lifetime of LDs; such heating causes optical and electrical instabilities that lead to catastrophic optical damage (COD), in which a dramatic temperature increase causes melting in the vicinity of the output facet. By appropriately responding to instabilities in laser diodes (LDs), SRL has demonstrated 10X increase in their lifetime. In Phase 1, we successfully identified an optical precursor of COD in high-power broad-area laser diodes. In Phase 2, we will (1) assemble a diode protection system using commercially available fast and intelligent data-acquisition systems; (2) demonstrate the improvement in lifetime and performance of laser diodes obtained by protecting; (3) fabricate intelligent fault-protection electronics that are based on the results of the optimum fault-detection criteria; and (4) deliver a prototype of the protection circuit to a facility of DARPA’s choice for additional testing and verification. As an option, we will extend our diode-protection technology to other LD systems of interest to DARPA: (1) Slab-coupled Optical Waveguide Lasers (SCOWLs), single mode LDs that can be coherently combined into high-power arrays; and (2) LDs incorporating SRL’s revolutionary cooling technology to provide operation at power levels unsustainable with conventional cooling.