A low diffraction laser beam as applied to polymer ablation

A low diffraction beam is obtained by altering the existing resonator of a CO2 laser using a special phase plate. The phase plate is designed based on the boundary diffraction principle and is implemented on the resonator rea r mirror. It is found that the low diffraction beam has a smaller M-2 value than that of a Gaussian beam. The effects of the improved beam quality on a laser ablation process are investigated using a polymeric material. A the oretical model is provided to predict the laser ablated hole profile and pe netration depth. The theoretical results are in agreement with the experime ntal measurements. Both the experimental and theoretical results show that the low diffraction beam has marked advantages over the Gaussian beam in ab lation-dominated material removal processes in terms of larger depth and sm aller taper at the same average power level. (C) 2001 Laser Institute of Am erica.