Laser micromachining is a widely used technique that has many benefits, such as the possibility to mill and polish the sample using the same laser system. Current laser systems can divide laser pulses into lower energy sub-pulses so-called bursts. Doing so allows for greater control of laser fluence, which results in greater ablation efficiencies and surface roughness if optimal parameters are chosen.
In this work, a femtosecond laser system capable of MHz, GHz, and burst-in-the-burst (bibursts) were used to investigate the influence of the number of pulses in the MHz, GHz, and bibursts on the surface polishing of stainless steel and copper. It was shown, that both MHz and GHz bursts are useful in reducing the surface roughness on metals. Ra values of 0.23 µm and 0.1 µm were achieved in the MHz and GHz burst regimes on copper, respectively. While low surface roughness values were very parameter dependant in the MHz regime, it was the opposite for the GHz burst, where many different pulse values yielded Ra of < 0.15 µm on copper. 
These results show that the efficient laser polishing using femtosecond pulses at MHz, GHz, and biburst regimes has a great potential to be applied in various fields where conventional polishing techniques could not be used, as this method can be performed under ambient conditions without the usage of any polishing pastes, gels, and slurries.