Ultrafast laser ablation of copper with GHz bursts: A numerical study on the effects of repetition rate, pulse number and burst fluence on ablation efficiency and heat-affected zone

•Ultrafast laserburst ablation is studied by an improved two-temperature model.•Effects of key factors in burst ablation on the ablation efficiency are analyzed.•Gigahertz ultrafast laser bursts improve the optimum ablation efficiency by 150%.•The burst fluence and duration determine the heat-affected zone thickness.•A theoretical model is proposed to predict the optimum burst ablation condition.