Non-collinear polychromatic light for inertial fusion energy

Normal broadband lasers with collinear polychromatic components have immense potential for mitigating laser plasma instabilities (LPIs). However, the projection complexity of collinear polychromatic light (CPL) is a significant challenge owing to the demand for a large bandwidth and beamlet number. Here, we propose a driver scheme for non-collinear polychromatic light (NCPL) with a small angle $\sim4^\circ$ between the double-color beamlets. The frequency difference between the beamlets of each NCPL is 1\%, and the beamlet colors of any two adjacent flanges are different. LPI models of the NCPL in both homogeneous and inhomogeneous plasmas have been developed, which lead to a decoupling threshold for the shared daughter waves under a multibeam configuration. Compared with the CPL, both the growth rate and saturation level of LPIs are greatly reduced by using the NCPL. The two- and three-dimensional simulation results indicate that the NCPL reduces the absolute and convective decoupling thresholds of the CPL and is sufficient to effectively mitigate the reflectivity, hot-electron generation, and intensity of cross-beam energy transfer. A novel design for the efficient generation of ultraviolet NCPL has been presented based on non-collinear sum-frequency generation. The proposed NCPL driver with a compact configuration can significantly enhance the beam-target coupling efficiency, which paves the way towards the realization of robust fusion ignition.