Green Stimulated Rotational Raman Scattering for Utilization in Laser Inertial Confinement Fusion Reactor

The The U.S. Naval Research Laboratory has developed a method to change the laser spectral width from a very narrow frequency bandwidth tilde 3 GHZ at full width half maximum to a range of at least 17 THZ in frequency bandwidth utilizing a stimulated rotational Raman scattering process (SRRS). The greater than 3 orders of magnitude (5000 times) in spectral range was achieved utilizing propagation in air and taking advantage of the SRRS response of nitrogen and oxygen. The SRRS process can be enhanced in focal geometry utilizing elliptical (circular) polarization relative to linear polarization. Seeding higher frequency Raman (anti-Stokes) transitions of air diatomic molecules can generate measurable light at equivalent lower frequency Raman (Stokes) transitions. The ability to increase bandwidth for solid state lasers utilizing an inexpensive medium such as air offers potential to be utilized in laser fusion ignition scale facilities to mitigate laser plasma instabilities. Mitigation of laser plasma instabilities (LPI) in a controlled manner offers the opportunity to control the spatial laser power with interaction of multiple laser beams as well as allow higher coupling (more energy) to various targets that otherwise would be limited without significant laser modification.