Polishing leaves a white mark on stainless steel and other metals. When compared to annealing and engraving, this method can be seen as a "lighter" way of engraving. The energy of the laser is reduced, which means that less material will be vaporized.
The process is quick and results in less ablation on a material like steel and a brighter marking. Regarding the parameters, this means less power and higher speeds that result in less energy per distance and higher frequencies that result in less pulse energy. Thereby, the laser-marked area is much lighter than it is in normal engraving.
Polishing is primarily suitable for materials that appear very dark and is not only possible on steel but on all metals.
—Josh Stephens, Trotec Laser