EAGER: Overcoming the Saturation Limit of High Intensity, Fully Coherent Raman Backscattering Laser

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The National Science Foundation uses the Early-concept Grants for Exploratory Research (EAGER) funding mechanism to support exploratory work in its early stages on untested, but potentially transformative, research ideas or approaches. This EAGER project was awarded as a result of the invitation in the Dear Colleague Letter NSF 16-080 to proposers from Historically Black Colleges and Universities to submit proposals that would strengthen research capacity of faculty at the institution. The project at Delaware State University aims to examine the feasibility of increasing the output energy in ultra-short laser pulses by over 100 times via the Stimulated Raman Backscattering (SRBS) technique. If this project succeeds, it could transform ultra-high intensity lasers, which in turn would have great technological and scientific impact. The project will strengthen research capacity and provide educational opportunities to students in the area of plasma physics. This project is funded by the Directorate for Mathematical and Physical Sciences.An alternative to the present chirped pulse amplification for high power laser is the Stimulated Raman Backscattering (SRBS) scheme, where a resonant interaction in plasma coherently mediates energy transfer from the long pump into the much shorter seed. The backscattered short seed should undergo simultaneous amplification and compression, and since plasma is impervious to optical damage and has unique dispersion properties, its power can grow to extraordinary levels. Feasibility of SRBS lasers was demonstrated theoretically and experimentally. Still, despite some progress over the past decade, the maximum amplified pulse energy was limited to milli-joule levels due to early saturation. This project addresses obstacles in SRBS through an integrated theoretical, computational, and experimental approach, and aims to develop a solid theoretical understanding of the underlying mechanism for the early saturation, verified by simulation and confirmed with experiments; develop a scheme to overcome the saturation limit and prove that the saturation barrier can be resolved; and demonstrate how a coherent, single spiked, and single cycled petawatt laser pulse can be generated via a moving soliton cavity in a millimeter-long plasma.