Spectrum-tailored random fiber laser towards ICF laser facility

Abstract

Broadband low-coherence light is considered to be an effective way to suppress laser plasma instability. Recent studies have demonstrated the ability of low-coherence laser facilities to reduce back-scattering during beam–target coupling. However, to ensure simultaneous low coherence and high energy, complex spectral modulation methods and amplification routes have to be adopted. In this work, we propose the use of a random fiber laser (RFL) as the seed source. The spectral features of this RFL can be carefully tailored to provide a good match with the gain characteristics of the laser amplification medium, thus enabling efficient amplification while maintaining low coherence. First, a theoretical model is constructed to give a comprehensive description of the output characteristics of the spectrum-tailored RFL, after which the designed RFL is experimentally realized as a seed source. Through precise pulse shaping and efficient regenerative amplification, a shaped random laser pulse output of 28 mJ is obtained, which is the first random laser system with megawatt-class peak power that is able to achieve low coherence and efficient spectrum-conformal regenerative amplification.

Digital generation of super-Gaussian perfect vortex beams via wavefront shaping with globally adaptive feedback

“…In particular, the low-coherence feature of RFLs makes them easy to be scaled up to high-intensity beams. Recently, a spectrum-tailored low-coherence RFL has been amplified to megawatt-class peak power, which shows great potential for the ICF laser facility [ 17 ] . The salient properties of RFLs are highlighted by the non-resonant lasing structure, the strongly suppressed temporal intensity fluctuation [ 33 ] and the low spatial coherence [ 34 ] , which are promising for the laser seed of ICF.…”

“…Therefore, all of these features pose a great demand for vortex beam shaping not only in the topological charge but also in the transverse intensity profiles. On the other hand, for temporal coherence, non-polarized vortex light from a random fiber laser (RFL) can contribute to a low-coherence laser seed that is greatly desirable in ICF [ 17 ] but cannot be efficiently created by a conventional liquid-crystal-based spatial light modulator directly using the non-polarized RFL. Aiming at addressing these requirements, a high-quality laser seed, that is, a low-coherence PVB with both a flat-top intensity profile and a flexibly manipulated high topological charge, is urgently needed, which has been seldom investigated to date.…”