Water-Assisted Femtosecond Laser Pulse Ablation of High Aspect Ratio Holes

Two novel techniques to enhance hole drilling in a silicon using a femtosecond laser, is presented. Firstly, the sprayed thin water layer has been used in an ablation region. Sprayed water removes the ablation debris and enables more efficient pulse energy transition into ablated material than in the air ambient. Secondly, the diffractive optical element (DOE) that generates into its far field 5x5 hole matrix at single irradiation, is used. By using the DOE instead of single hole drilling it is possible to ablate several holes simultaneously. Both of these techniques enhance the femtosecond ablation rate significantly.