Self-focusing, compression and collapse of ultrashort weakly-relativistic Laguerre–Gaussian lasers in near-critical plasma

Abstract Simultaneous self-focusing and compression of ultrashort weakly-relativistic Laguerre–Gaussian laser pulses in dense plasma is investigated theoretically numerically. A simple theoretical model developed used to identify parameter regimes interest, then three-dimensional particle-in-cell simulations are carried out examine the physics detail. Rapid observed, leading pulse collapse even for energy at ten millijoule level. Long-lived ring-shaped post-soliton structures left location first collapse, residual scattered into plasma. Filamentation re-focusing occur beyond this point, structure which depends on beam parameters but observed be only weakly dependent upon mode laser. Circularly-polarised light found produce particulary symmetric density structures. In all cases, bursts MeV electrons with thermal-like spectra points collapse.