Impact of Bandwidth on the Electron Distribution Functions of Laser-Produced Plasmas

The nonlinear absorption of laser light by an underdense plasma and associated development of non-Maxwellian distribution functions is a classic problem in plasma kinetics. To date, theory and simulations of this basic process have focused on the case of monochromatic laser light. However, ultra-broadband laser drivers are being developed that are capable of fractional bandwidths as high as 1.5% at 3ω. Using Vlasov–Fokker–Planck simulations, we reconsider the problem of nonlinear inverse bremsstrahlung absorption, taking into account non-negligible laser bandwidth. Special attention is paid to evolution on the slow beat wave time scale that is absent in the monochromatic case.