The Study Of Femtosecond Laser Ablation Process And Surface Morphology Of Solid Materials

Femtosecond laser shows advantages in the field of micro processing because itcan reach the highest power in the shortest time. Traditionally, we machine materialsusing long short pulses, and the processing area comes more than the wavelength oflaser. Femtosecond laser interaction with material process is complicated. Themechanism is different for different laser energy and materials. In this paper, theinteraction of femtosecond laser with materials were studied both theoretically andexperimentally.Our work is as follows:Firstly, we discuss how the femtosecond laser interect with materials, also, wesimplified the dual-temperature equation, electronic and lattice temperature evolutionis simulated under different incident laser power on copper and titanium, andsummarizes the time of the electronic coupling with the lattice under differentincident laser power.Secondly, we studied the periodic structure evolution under differentfemtosecond laser energy. When the power is low, we can see the vertical periodicsurface structure clearly that in the direction of polarization of the incident laser. Theperiodic stripe structure was gradually destroyed with the increasing laser energy, andwe can see it in the rigin of the ablation area. We explain the phenomenon using thethreshold theory. The periodic surface structure is destroyed and no longer visiblewhen the energy is high, and we see the nanoparticles in the region of the ablationarea. We carry our experiment on copper and titanium, measuring the period underdifferent incident laser energy, and calculating the period in theory, and the result isin good agreement with the experiment. We draw the conclution that the periodicstructure has nothing to do with the incident laser energy, but has something to dowith the metal type. In addition, we also carried out the experiment onsemiconductor silicon and found different periodic structure from the metallic material. We obtained the damage threshold of titanium equalling0.20J/cm2throughestablish the relationship between incident laser power energy and ablation diameter.We measured the elemental composition of Si under different femtosecond laserablation, the oxygen content of the ablated region increases with the increasingincident laser energy. This plays an important role in femtosecond processingmaterials.Finally, we fixed the incident laser energy and varied the number of incidenrlaser pulses, and studied the ablation morphology and periodic structure on copperand titanium when irradiated by femtosecond laser. When the number of pulsesincreases, the area of the ablation also increases, we found periodic structure in theregion, and explained it using the Gaussian distribution of incident laser energy.