Laser Micro-Machining of Spherical and Elliptical 3-D Objects using Hole Area Modulation Method

Laser micromachining has the capability to fabricate very small and basic 2.5 D geometric features on a range of materials in the form of laser ablation or irradiation. Short pulsed lasers that can achieve wide range of wavelengths in the form of harmonics of infrared laser beam at 1064 nm wavelength have been a very effective micro-machining tool used for hole drilling, cutting, scribing, trimming and marking. A review of laser processing of materials is given in this paper. Direct laser ablation can be performed by controlling laser beam properties such as laser energy, intensity, pulse duration and wavelength in micro-machining 3-D geometric features. However, this method requires additional capabilities for a typical laser beam generating and delivery system. When the laser beam properties cannot be altered, Hole Area Modulation (HAM) method becomes alternative solution by controlling the density of the holes and the step size in a mask to improve the accuracy of the 3-D geometric feature. In this paper, we perform modeling, planning and simulation of laser micromachining with hole area modulation method to produce spherical and elliptical objects 3-D geometrical features that are typical for aspheric and or refractive micro-lenses. A computational methodology is developed to design a mask with varying density and diameter of the holes. The masks are created using micro-drilling and utilized in laser micromachining of 3-D objects on polycarbonate polymer substrates.