Research on microcracks avoidance in processing of α-Al_2O_3 by ultrashort laser pulses

摘要

The optical crystal α-Al_2O_3 has been widely used as the matrix of ruby and blue sapphire for its wide transparency, high thermal conductivity, big scale and low cost. α-Al_2O_3 is so hard that cutter is easily abraded. Micromachining of α-Al_2O_3 by ultrashort pulsed laser is superior to the traditional mechanical approach as its non-contact and cold machining features. However, unexpected cracks on the surface of α-Al_2O_3 are observed after femtosecond laser machining. In order to hinder the crack source from stretching, we optimize the laser parameters accompanied with annealing. The crack-free machining can be achieved. Three-dimensional α-Al_2O_3 microstructures free from fracture, such as cylinder, barrel and sphere are demonstrated.