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General information

  • Lasers are classified into seven categories (1, 1M, 2, 2M, 3R, 3B, and 4), depending on their danger potential.
  • The main danger concerns the eyes. Never stare directly into a laser, and never aim a laser beam at people or animals.
  • Not only the direct laser beam is dangerous, but reflected and scattered laser light is dangerous as well.

Laser classes

  • Class 1 lasers are harmless, but are only few and with very low power.
  • Class 2 lasers are considered harmless only for the duration it takes to blink (250 milliseconds). Class 2 lasers emit visible light and at most 1 mW of optical power.
  • Class 3 lasers are dangerous for the eyes. Class 3 lasers emit up to 5 mW in continuous wave mode
  • Class 4 lasers are extremely dangerous for eyes and skin. Even reflected or scattered light is still dangerous.
  • Special care should be paid with pulsed lasers, which often belong to Class 4.


Class 1 lasers

  • No precautions are necessary.

Class 2 lasers

  • Don't stare into the beam. Don't aim at people or animals.

Class 3 and 4 lasers

  • Wear laser protection goggles (for the correct wavelength)
  • An area where lasers are in use should be delimited, and access to the area should be verified.
  • Place laser warning signs and a laser warning lamp at the entrance of the lab.
  • One person should be designated to be responsible for laser safety, and only instructed and qualified personnel should be allowed into the laser area.

Warning sign

The following warning sign can be obtained from the D-PHYS shop:




Tobias Donner

Dr. Tobias Donner


ETH Zurich

Professur für Quanten-Optik

Dr. Tobias Ulrik Donner

HPF D 19

Otto-Stern-Weg 1

8093 Zürich


  • phone +41 44 633 39 54 
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Sat Jun 24 03:54:00 CEST 2017
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