High-aspect-ratio microdrilling in polymeric materials with intense KrF laser radiation

UV laser microdrilling of high-aspect-ratio holes has been studied by using an intense beam with a low numerical aperture (KrF laser). The UV laser ablation produces a minimum of thermal or mechanical damage on the target. Under some particular experimental conditions (many high-fluence pulses), it is shown that long deep holes are obtained with reproducible aspect ratio (up to Φ/d≈600) in a variety of materials. Experiments with polymers (PMMA, PC, PET, PI, PS, PEEK) show that the more absorbing the polymer is, the better the resolution. However highly absorbing materials exhibit a low ablation rate. These promising results on laser microdrilling can be extended to new applications, for example, when the beam/target relative movement is computer driven. For instance this approach can be applied to cutting micro-objects with complicated shape or to machining fragile or brittle materials.