Reducing the total stimulated brillouin scattering of two-color lasers through two-ion decay

A mechanism coupling the stimulated Brillouin scattering (SBS) of two-color lasers with wavelengths of 527 and 351 nm via the two-ion decay instability is proposed. When the SBS reflectivities of both lasers exceed 10%, the ion-acoustic wave excited by the 527 nm laser seeds the decay process of the ion-acoustic wave excited by the 351 nm laser, thereby promoting the decay of the latter into the former. This results in a significant reduction in the SBS reflectivity of the 351 nm laser, while the SBS of the 527 nm laser exhibits minimal variation, consequently reducing the total SBS reflectivity. The total SBS reflectivity initially decreases and then increases as the intensity fraction α of the 527 nm laser rises. When α ∼ ( 20 % − 30 % ) , the laser energy reflections from both lasers become approximately equal, achieving the minimum total reflectivity. Through this mechanism, the incidence of the two-color lasers can achieve lower reflected energy compared to monochromatic lasers with the same total intensity. These results demonstrate the significant potential of replacing a small fraction of high-frequency light with low-frequency light in enhancing the laser-target coupling efficiency for inertial fusion energy.