Experimental Studies On Shaped Femtosecond Laser Ablation Of Metals

With the development of laser technology, laser micro processing technology has been concerned in recent years.The laser micro processing technology has a lot of advantages such as:the function of short time, heat affected zone small, high machining accuracy and easy to control and so on.In order to study laser and material interaction to promote the development of laser micro processing technology, national research workers have made many meaningful work.In this thesis,we mainly through recording diode signal and observation sample drilling morphology to study the influence of laser drilling in different experimental conditions . The samples which we used in our experiments are aluminium foil (50μm, 150μm) and copper foil (100μm).In our experiments we change the relative positions between samples and laser focus , and found that when the sample near the laser focus location the hole diameter is small and the diameter of laser focus hole increased gradually. When we decrease the laser energy , we found the diameter of the hole decreased gradually.In aluminum foil experiment we found that when energy is lower enough, diode signal will appear first increases, then decreases until zero .When we use different repeat frequency laser to drill the hole, we found that high frequency laser has stimulative effect on drilling.We changed the pressure of the background gas , and find that with the increase of the pressure, the sediment increased quantity is not linear, but first increase then reduced. We explained the reason of the above-mentioned phenomenon.Pulse shaping technology can change the shape of a single transform limited pulse,and results drilled by different shaped pulse are different. In our experiments we use different shaped pulse to drill samples, and found the holes drilled by some shape pulse are obviously better than those drilled by transform limit pulse.