Improving Self-Guided Pulsed Energy
State-of-the-art mid-infrared pulsed light sources can now exceed the critical power for self-focusing in atmosphere. This allows tens of millijoules of pulse energy in the mid-wave infrared (MWIR) and joules of energy in the long-wave infrared (LWIR) to be self-guided. While this is a major milestone for the field of directed energy and other Department of Defense applications, the sources used—carbon dioxide lasers and laser/optical parametric chirped pulsed amplifier (OPCPA) hybrid systems—have key limitations for applications in portability, bandwidth, efficiency, and adaptability for a dispersive environment.
Jeffrey Moses and Frank W. Wise, Applied and Engineering Physics, are addressing these limitations. Moses and Wise are combining the huge transparency window of gas with the high-intensity, ultrabroadband waveguiding afforded by coated hollow-core fibers. Doing this, they are investigating three unexplored concepts for robust, efficient, high-peak-power, and ultrabroadband LWIR/MWIR light generation: adiabatic four-wave mixing, Raman amplification, and nonlinear multimode (waveguide) beam combining. These provide the portability and robustness of waveguided devices, but also a combination of greater bandwidth, efficiency, and adaptability than existing concepts. They are demonstrating a proof-of-principle for each of these techniques at modest pulse energies and investigating their scalability to multi-terawatt peak powers. This means the researchers are moving toward their promise for directed energy and related applications, such as ranging, remote sensing, free-space communications, and triggering of electrical discharges.