Femtosecond micro-machining at atmospheric pressure near air-ionization threshold

Summary form only given. Femtosecond laser pulses are capable of producing very small features (on the order of 1 /spl mu/m) without significantly modifying the surrounding bulk material. Furthermore, it is well known that these pulses produce very smooth and deterministic features when compared with conventional laser processing. Since it is common for intensities to exceed 10/sup 15/ W/cm/sup 2/ during femtosecond ablation, several experiments have been performed at low pressures (<10/sup -3/ mbar) in order to avoid unwanted nonlinear reactions with the surrounding atmosphere. However processing in ambient atmospheric conditions would be preferable for femtosecond laser processing to be useful in commercial applications. We present a detailed study of femtosecond and subnanosecond ablation in glasses, ceramics, carbon composite, and metals in order to determine the influence of air on characteristics such as penetration rate and surface quality.