Metal Colouring With Femtoscond Laser Pulses

Micro-and nano-structure on aluminum surface is prepared using femtosecond laser through either fixing or scanning the focused laser beam in this thesis. The femtosecond laser-induced periodic surface structures had been firstly obtained by the fixed laser beam method, and the structures were observed by using a scanning electron microscope. The effects of pulse energy and pulse number on the micro-structure morphology formation of the aluminum surface had been discussed. The mechanism of periodic micro structure formation was analyzed by interference theory between femtosecond laser and surface plasmon polaritons, and the spatial distribution of electron energy on the aluminum surface was simulated by using two-temperature model. In the experiment of scanning focused laser beam, grating structures on the surface of aluminum were formed, and structured aluminum sample shows as black, gray or golden by properly controlling experimental parameters. 85%-95% of the incident light in the wavelength of 8μm to 26μm is absorbed by the blacken aluminum. Color variation of aluminum was explained by utilizing color optics theory, and the varying mechanism of optical properties for aluminum samples was analyzed on the microscopic scale.