Ultrashort pulse laser interaction with dielectrics and polymers

Femtosecond laser micromachining has excited vivid attention in various industrial fields and in medicine owing to the advantages of ultrashort laser pulses compared to long-pulse treatment. These are mainly the reduction of the laser fluence needed to induce ablation and the improvement of the contour sharpness of the laser-generated structures. Recently, special attention was paid to femtosecond laser experiments on nonabsorbing inorganic dielectrics. This is due to the fact that optical damage in dielectric optical elements limits the performance of high-power laser systems. Despite the fact that a large variety of organic polymers can be machined with excimer lasers successfully, the involvement of thermal processes can lead to an unsatisfactory quality of the structures. Ultrashort, fs-laser pulses might be an alternative for the treatment of polymers. Therefore, femtosecond laser machining investigations of dielectrics and polymers are reviewed in this paper. Similarities and differences of the ablation behavior of both material classes are discussed. The influence of the bandgap on the ablation threshold in dependence on the pulse duration, the enhancement of the machining precision with a shortening of the pulse duration, incubation phenomena, and morphological features appearing on the surface after femtosecond laser treatment are mentioned. Possible applications, e.g., in medicine and biosensors, are described.