Coherent optical radiation (lasers)

What is coherent optical radiation?

Coherent optical radiation is a form of optical radiation consisting of light waves that are congruent in their phase and direction. The best-known source of coherent optical radiation is the laser, which emits monochromatic light, i.e. light of a single colour or with a very low spectral width. Laser light is also phase-coherent, meaning the wave amplitudes are synchronized in time and space. These characteristics allow laser beams to be precisely focused, making them highly effective for a wide range of applications across various fields.

What hazards are presented by coherent optical radiation?

The biological effects of laser radiation are fundamentally similar to those of conventional optical radiation. They depend on the wavelength, irradiance, and duration of exposure. The particular health risks of laser radiation arise primarily from the extremely high power density and the strong focusing of the laser beam. Lasers should therefore be operated only in controlled environments and by qualified personnel, in accordance with their respective laser classes. The relevant exposure limit values are laid down in the Ordinance on the Protection of Employees from Hazards Caused by Artificial Optical Radiation (Occupational Safety and Health Ordinance on Artificial Optical Radiation - OStrV). The Technical Rules for the Occupational Safety and Health Ordinance on Artificial Optical Radiation (TROS Laser) specify, within their scope of application, the requirements of this German OSH Ordinance. These rules distinguish between ranges of wavelength and exposure times that lead to different characteristic injuries caused by thermal or photochemical processes in different areas of the eye and skin.


Users and system manufacturers must observe the limit values, taking account of direct, indirect (unintentionally specularly reflected) and scattered (unintentionally diffusely reflected) radiation.

What harm may occur?

Damage to the retina is among the most serious effects of lasers. Even exposure of very brief duration may cause damage to a part of the retina, which is very sensitive. In addition to the danger to the eyes and skin, which may be considerable (irreparable damage), lasers may also pose other dangers:

• Glare or temporary impairment of vision
• Fire and explosion hazard (the laser constitutes an ignition source)
• Toxic substances (associated with dye lasers, gas lasers)
• Production of toxic or infectious vapours, gases or aerosols and secondary radiation (e.g. UV radiation)

How can persons be protected against coherent optical radiation?

To ensure protection against coherent optical radiation, the hazards at the workplace must first be identified and assessed. Legislation and technical rules are in place that employers must comply with. The most important protective measures are:

• Use of technical or organizational measures to avoid or reduce exposure. Such measures include screening, marking, access restrictions and time limits
• Provision of information and instruction to workers on the risks and protective measures
• Provision of preventive occupational medical care for certain tasks involving coherent optical radiation
• Use of personal protective equipment, e.g. safety glasses, gloves or clothing