Uniform colorization of metal surfaces through omnidirectional femtosecond laser-induced periodic surface structures

Following femtosecond(fs) laser pulse irradiation, the formation of a new type of low spatial frequency laser-induced periodic surface structures(LSFLs), namely omnidirectional LSFLs(OD-LSFLs) with the periodic ordering of their orientations are investigated on Ni. Using a liquid crystal polymer patterned depolarizer, we periodically rotate the polarization of fs laser pulses across the laser spot and create OD-LSFLs by raster scanning fs laser pulses. It is also shown that the period of OD-LSFL orientation rotation can be controlled with the defocused distance, and OD-LSFLs can significantly expand the viewing angle of the structural colors in the azimuthal direction without noticeable color degradations.