Study On Machining Of Sapphire By Ultrashort Laser

Sapphire crystal has been widely applied to industry, national defense industry, scientific research and other fields due to its excellent physical, chemical and optical performances on hardness, chemical stability and transmittance. It has been applied on such as high-end table of the wear resistant surface, the epitaxial substrate of semiconductor materials and the window materials for infrared military devices and missiles. It attracts highly attention again especially due to its wide application on mobile phones. However brittleness is its critical defect for sapphire crystal and it is quite often to create chipping and cracking during the processing, and due to its complicated growth process and high production cost, machining on sapphire in high quality and low cost has been always a challenge. In this study, the high-precision machining of sapphire crystal by short wavelength ultraviolet laser and ultrashort pulse picosecond laser were researched in detail. The main contents include the following:(1)Make an introduction of the general rule of laser and material effect, and analyze the interaction mechanism of short wavelength UV laser & ultrashort pulse picosecond laser and sapphire material.(2)Study on machining of sapphire by 355 nm nanosecond(~40ns) laser. The parameters of the nanosecond UV laser machining of the sapphire substrate with the thickness of 0.55 mm, including laser power, scanning speed and scanning times, are systematically investigated by controlling variables during the experiments. And the threshold peak power density of nanosecond UV laser damage to sapphire substrate is determined by the laser punching method is 0.5×109W/cm2. Finally, though the comparison analyze of the theoretical model and the experimental results of the micro channel etching, it is confirmed that the process of nanosecond UV laser processing is mainly the removal mechanism of photo thermal effect, the heat effect limits the quality and depth of its cutting sapphire, which cannot achieve cutting the graphics of sapphire substrate even if its peak power density reaches 109 W/cm2.(3)Study on machining of sapphire by 1064 nm picosecond(~15ps) laser. The threshold peak power density of picosecond laser damage to sapphire substrate is determined by the laser punching method is 0.5×1012W/cm2. Explore the laws of the laser power, scanning speed and scanning times on the processing of sapphire substrate by laser scanning etching micro groove experiment, and modification of the processing parameters has no effect on the width of the cut groove, however increasing the time of scanning can benefit to improve the machining quality. Based on the experimental results, the parameters are optimized, and successfully machined different graphs and sizes on the blank of sapphire substrate with the thickness of 0.55 mm in high-quality by using the method of hierarchical scan cutting. Graphic structure without chipping and cracks and other thermal phenomena. Finally, according to the experimental results, determine the sapphire material under picosecond laser action can be attributed to a "cold" ablative material removal mode. It has certain advantages in the processing of hard brittle materials such as sapphire.