Micro-void and spherical dome formation in polycarbonate with nanojoule energy femtosecond laser pulses

We report on the formation of micro-voids inside polycarbonate samples upon irradiation with a high repetition rate and low energy femtosecond laser. The laser focal point was varied through the sample thickness and the resulting features were analyzed in a scanning electron microscope. It was found that spherical dome-like features are formed on the sample surface and that their size depends on the depth of the laser focal point. Resolidified …