High capacity color code prepared on titanium alloy using femtosecond laser

Abstract This study reported on the high capacity color code obtained by femtosecond laser-induced surface oxidation on titanium alloy. The color code with quaternary numbers was designed. Various colors were obtained by changing the pulse energy and scanning speed. Moreover, the XPS survey spectra showed the surface chemical composition of different colored areas was TiO2. Experimental reflectance data and simulations showed that the increase of oxide layer thickness led to peak shift and color change. Taking into account the effect of color code unit size on coloring, the processing areas with an area of 1 × 1 mm2 and 6 × 6 mm2 were prepared. Since the color difference showed that the colors obtained under different unit sizes were different, the effect of size should be considered in the actual processing. By changing the scanning speed, different color areas with obvious contrast could be obtained to meet the conditions of color code realization. Therefore, this research further realized the encryption of information on the basis of increasing the information capacity of the marking.