Random fiber laser could drive next generation fusion experiments

An inertial confinement fusion experiment at the National Ignition Facility recently became the first such experiment to achieve fusion ignition, generating more energy than was introduced. One of their biggest obstacles was suppressing laser-plasma instability, where nonlinear effects between the laser and the plasma reduce the effective energy input. For commercial fusion generators, this effect must be minimized to reach necessary levels of efficiency.

Fan et al. describe how a random fiber laser (RFL) can be used to suppress LPI.

“RFL features low coherence and flexible design, which is promising to optimize the laser pulse injected into the hohlraum and suppress the LPI effect,” said author Zinan Wang.

Researchers have found multiple ways to reduce LPI, but one of the most promising ways for high-energy applications, such as ICF, is reducing the coherence of the light source. This can be achieved with RFL, which uses randomly distributed Rayleigh scattering in fiber as a feedback mechanism, resulting in a low-coherence output capable of suppressing LPI without sacrificing laser intensity.

“Moreover, compared with other low coherence light sources, random fiber laser can be flexibly designed by tailoring the cavity parameters,” said Wang. “We demonstrate RFL spectrum tailoring, precise shaping in the time domain, and efficient amplification based on a solid-state gain medium.”

The authors express that much work still must be done to move RFL from a theoretical proof of concept to practical use in fusion experiments. Because ICF experimental conditions are very complex, future research will be needed to understand how best to tailor the RFL parameters for maximum fusion efficiency.

Source: “Spectrum tailored random fiber laser towards ICF laser facility,” by Mengqiu Fan, Shengtao Lin, Ke Yao, Yifei Qi, Jiaojiao Zhang, Junwen Zheng, Pan Wang, Longqun Ni, Xingyu Bao, Dandan Zhou, Bo Zhang, Kaibo Xiao, Handing Xia, Rui Zhang, Ping Li, Wanguo Zheng, and Zinan Wang, Matter and Radiation at Extremes (2023). The article can be accessed at https://doi.org/10.1063/5.0129434 .