Introduction

Laser sources emit both spatially and temporally concentrated light.

Spatial concentration corresponds to the possibility for laser light to be focused on very small surfaces, while carrying high powers. For example, one single Helium-Neon laser source, emitting 1 mW, can induce a bedazzlement ten times stronger than the one induced by sun light.

Temporal concentration corresponds to the possibility for laser light to carry a considerably high number of photons in a very short time. Laser pulses carrying energies of about one Joule during one nanosecond are common. The instantaneous power of the impulsion is in this case of the order of Gigawatt ! Still more powerful light pulses (up to the Petawatt, 1015W) are becoming more and more common. The effects induced on matter by such pulses are extremely violent : very fast absorption of the radiation, followed by high speed ejection of matter.

Laser is thus a dangerous tool as it can affect irreversibly both skin and eyes.

In the present context, where laser sources tend to be used for an increasing number of purposes, where their performances increase each year (sources emitting kilowatts continuously and Terawatts during pulses are becoming common), laser safety is a mandatory subject to study for laser users.

The purpose of this course is to present to the reader the main hazards related to laser sources and the way to prevent them. The structure is in three parts : after some reminders on lasers, the related hazards will be presented. Then follows the description of laser safety, including legal standards, physical quantities relevant for quantifying the hazard, and finally prevention. Case studies will finally analyze real laser accidents and thus show some good concrete behaviors for future laser users.