SBIR Phase I: Simple Device for Measuring Nanosecond Laser Pulses

This Small Business Innovation Research (SBIR) Phase I project proposes to develop a simple, single-shot, inexpensive, and complete laser-pulse measurement device for ~100ps to ~10ns pulses. While long (>10ns) pulses are easily measured, and recently developed techniques completely measure ultra-short pulses (<10ps), intermediate-length ~1ns, pulses remain only partially and roughly measurable, and, consequently, such pulses generally remain complex and unstable. This is unfortunate because most commercial pulsed lasers emit pulses in this intermediate range. The proposed measurement device extends Frequency-Resolved Optical Gating (FROG), a very successful technique for measuring the complete intensity and phase versus time of ultra-short pulses, which operates by measuring the pulse's spectrogram. The main challenge in extending FROG to much longer pulses is the generation of a many-ns delay range on a single shot - currently an unsolved problem in general. The proposed innovation solves it by tilting the input pulse by a remarkable ~89.9° without distorting it in time. As a result, one side of a ~1cm-wide beam precedes the other by over a meter. The proposed ns FROG can measure even very complex pulses and will cost about 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 will extend to most pulsed lasers, from Q-switched and gain-switched solid-state lasers to fiber lasers, which emit ~ns pulses and have many applications. All such applications will benefit from this device. First, ~ns-laser users will now have adevice to test their laser?s performance, and it will be simple, easy to use, single-shot, and relatively inexpensive. It will be essential in attempts to coherently combine pulses from multiple fiber lasers, generally regarded as the next important step in high-power fiber-laser development. Injection-seeded Qswitched and gain-switched lasers, which endeavor to emit very clean ~ns pulses, are also in need of such a method for performance confirmation. Finally, laser engineers in general will be better able to improve the quality of ~ns-laser pulses, greatly benefitting all ~ns-pulsed-laser experiments and applications. If the spectacular progress in ultrafast lasers that occurred after complete ultra-short-pulse-measurement technology was introduced is any indication, such an inexpensive and simple device for measuring ns pulses should make a huge difference in the generation of ever more stable ~ns pulses and consequently in the many fields that use such lasers, from welding to surgery to material processing to distance measurements to remote sensing.