Stimulated Raman scattering (SRS) is one of the major laser-plasma instabilities that can inhibit laser-target coupling, generate hot electrons, and consequently reduce the fusion efficiency. Kinetic inflation significantly amplifies the threat of SRS instability in inertial confinement fusion by enhancing SRS reflectivity. This process relies on phase matching between the incident light wave and its decay products—a scattered light wave and an electron plasma wave (EPW). Although density inhomogeneities can disrupt phase matching by altering the EPW frequency, electron trapping within the EPW induces a compensating frequency shift, enabling kinetic inflation and further increasing SRS reflectivity. We show that large laser bandwidth and small laser speckles can mitigate inflationary SRS by restricting EPW growth, maintaining reflectivity at non-inflationary levels. Since the instantaneous reflectivity depends on the local chirp, intensity, and the correlation between the incident angle and frequency of the pump laser, the inflationary SRS threshold depends on beam smoothing techniques, such as smoothing by spectral dispersion and induced spatial incoherence. These findings establish distinct scaling laws that offer critical guidance for developing effective SRS mitigation strategies.

laser bandwidth,stimulated Raman scattering,kinetic inflation