Ultrafast lasers possess safety hazards not associated with light from conventional sources. Among potential injuries, eyes are the most vulnerable. Damage to the retina cannot be repaired and does not heal by itself.
Why is eye safety so critical? Compare the output of femtosecond lasers with the radiation that the human eye can receive from the sun on a clear day. The sun’s image on the retina is approximately 160 microns. This yields a radiation density of around 30 W/cm2. A typical Ti:Sapphire femtosecond oscillator is capable of producing intensity in excess of 50 GW/cm2, while an amplifier will easily exceed 1014 W/cm2. Obviously, very weak laser reflections, or even scattering from rough surfaces, can be extremely bright - dangerously bright - to the eyes.
You are urged to read carefully the safety section found in the user manual of any laser product you use and to strictly adhere to those instructions.
