SBIR Phase II: Simple Device for Measuring Nanosecond Laser Pulses

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This Small Business Innovation Research Program Phase II project proposes to develop a simple, single-shot, inexpensive, and complete laser-pulse measurement device for ~100-picosecond to ~10-nanosecond pulses. Long (10 nanosecond) pulses are easily measured, and recently developed techniques completely measure ultrashort pulses (10 picosecond). But intermediate-length, ~1-nanosecond, pulses remain only partially, roughly, and expensively measurable, and so generally remain complex and unstable. This is unfortunate because most laser pulses are in this intermediate range. The proposed measurement device is based on frequency-resolved optical gating (FROG), a very successful technique for measuring the complete intensity and phase vs. time of femtosecond pulses. The main challenge in extending FROG to much longer pulses is the generation of a many-nanosecond delay range on a single pulse-currently an unsolved problem in general. The proposed innovation solves it by tilting the input pulse by a remarkable ~89.99° without distorting it in time. As a result, one side of a ~1cm-wide beam precedes the other by over a meter. The proposed nanosecond FROG can completely measure even complex pulses and will cost less than one tenth as much as the high-bandwidth oscilloscopes currently used to only partially measure such pulses. The broader impact/commercial potential of this project follows from the fact that most pulsed lasers, from solid-state lasers to fiber lasers, emit pulses about a nanosecond long. They are the least stable lasers in the world, yet they have billions of dollars of applications, from materials processing to distance measurements to remote sensing to medical, military, and scientific uses. With the proposed device, nanosecond lasers will finally have a previously unavailable device to monitor their performance and to diagnose problems before expensive materials are ruined or patients are harmed. It will also be essential for combining pulses from multiple fiber lasers, generally regarded as the next important step in the development of compact and convenient high-power pulsed lasers. Finally, using this device, laser engineers in general will be better able to improve the quality of nanosecond laser pulses, thus greatly benefitting all pulsed-laser applications. If the spectacular progress in much-shorter-pulse lasers that occurred after analogous complete pulse-measurement technology was introduced there is any indication, such an inexpensive and simple device for measuring nanosecond pulses should make a huge difference in the generation of cleaner, more stable nanosecond pulses and consequently in the many fields that use such lasers.