Laser induced ablation of materials has became an extremely important area of research and application. The laser sources for ablation cover the wavelengths from ultraviolet (most are excimer lasers), visible (copper vapor lasers, argon ion lasers) to the infrared (Nd:YAG lasers, CO2 lasers). The laser material processing technique is intensely used in both the electronic and aerospace industries. In this paper, a new theoretical model describing laser microhole drilling processes in carbon fiber composites (CFC) has been developed, which can predict the profiles ofthe microholes for certain incident beam profiles. The calculated results for several specific incident beams will be presented in this paper. We show how the peak fluence, the beam diameter, and the material parameters (absorption coefficient, threshold ablation fluence) affect the hole
shapes. Although the model is specific to CFC, it can be applied to any other laser micromachining process for materials such as polyimide, polymethylmethacrylate (PMMA), polyethylene terephthalate (PET) etc. We not only present a new method to model the drilling hole profiles but also explain why hole drilling will stop under
certain circumstances in the low fluence regime for polymers and fiber reinforced composites. The model explains tapered wall formation and stabilized drilling, from which, high efficient laser drilling and cutting can be predicted in low fluence regimes. This new model is suitable for most well defined beams and materials such as polymers, fiber CFC, glass fiber composites and some ceramics.