Ultra-short pulse laser safety - a challenge to materials science

Abstract

In this paper, safety-related experiments with ultra-short laser pulses (down to 30 fs) on various components (goggles, curtains) for laser protection are presented. The damage and failure behaviour of protective devices has been investigated dependent on practical conditions such as pulse duration, laser fluence, pulse number, and repetition rate. The effects of laser-irradiation on materials can be roughly divided into transient ones like laser-induced transmission (LIT) or short-lived colour centres and permanent damages like the stable colour centres and ablation. The former effects are particularly important for transparent devices like laser goggles. To obtain a complete overview on laser safety issues and the prevention of failure there are two important fields of investigation: 1. the effects of laser radiation on human eyes and skin, and 2. on the possible protection materials. Both fields have been addressed during the recently finished German project SAFEST (safety aspects in femtosecond technology). The amount of safety data available in the ultrashort pulse region has been increased remarkably. This allows for a re-evaluation of known laser protection materials for this region of pulse durations and for the evaluation of new designs that promise high protection levels while being light-weight and convenient to use.