Exploration of laser driver technology for high-gain fusion: the Kunwu low-coherence broadband laser facility

Suppression of laser plasma instabilities is one of the key factors to achieve high-gain laser inertial confinement fusion. Reducing laser coherence and breaking the growth path and time of laser-plasma interaction process are expected to achieve better suppression of laser-plasma instability. Low coherence pulses with randomly distributed spectral phases have the characteristics of instantaneous broadband and good spatial coherence. As the driving pulses, combined with beam smoothing techniques, low coherence speckle distribution in the dimensions of temporal, spatial, and polarization can be achieved. Shanghai Institute of Laser Plasma (SILP) has conducted research on low coherence laser driver technology based on the neodymium glass level amplification technology route. This study aims to review the developments, including low-coherence front-end with precise time and spectral shaping, high-efficiency amplification, frequency conversion and beam smoothing of low-coherence broadband pulses. Through the integrated application of the aforementioned innovative technologies, the Kunwu low-coherence broadband laser device has been built, which can deliver kilojoules pulse with a bandwidth of 13 nm. At present, a series of laser-plasma interaction experiments have been carried out, confirming the inhibitory effect of broadband laser on stimulated Raman scattering and stimulated Brillouin scattering, and providing important support for high-gain laser inertial confinement fusion research.