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Safety measures of laser

General precautions

Many scientists involved with lasers agree on the following guidelines:

  • Everyone who uses a laser should be aware of the risks. This awareness is not just a matter of time spent with lasers; to the contrary, long-term dealing with invisible risks (such as from infrared laser beams) tends to reduce risk awareness, rather than to sharpen it.
  • Optical experiments should be carried out on an optical table with all laser beams travelling in the horizontal plane only, and all beams should be stopped at the edges of the table. Users should never put their eyes at the level of the horizontal plane where the beams are in case of reflected beams that leave the table.
  • Watches and other jewelry that might enter the optical plane should not be allowed in the laboratory. All non-optical objects that are close to the optical plane should have a matte finish in order to prevent specular reflections.
  • Adequate eye protection should always be required for everyone in the room if there is a significant risk for eye injury.
  • High-intensity beams that can cause fire or skin damage (mainly from class 4 and ultraviolet lasers) and that are not frequently modified should be guided through tubes.
  • Alignment of beams and optical components should be performed at a reduced beam power whenever possible.

Protective eyewear

Laser goggles

The use of eye protection when operating lasers of classes 3B and 4 in a manner that may result in eye exposure in excess of the MPE is required in the workplace by the U.S. Occupational Safety and Health Administration.

Protective eyewear in the form of spectacles or goggles with appropriately filtering optics can protect the eyes from the reflected or scattered laser light with a hazardous beam power, as well as from direct exposure to a laser beam. Eyewear must be selected for the specific type of laser, to block or attenuate in the appropriate wavelength range. For example, eyewear absorbing 532 nm typically has an orange appearance, transmitting wavelengths larger than 550 nm. Such eyewear would be useless as protection against a laser emitting at 800 nm. Furthermore, some lasers emit more than one wavelength of light, and this may be a particular problem with some less expensive frequency-doubled lasers, such as 532 nm "green laser pointers" which are commonly pumped by 808 nm infrared laser diodes, and also generate an intermediate 1064 nm laser beam which is used to produce the final 532 nm output. If the IR radiation is allowed into the beam, which happens in some green laser pointers, it will in general not be blocked by regular red or orange colored protective eyewear designed for pure green or already IR-filtered beam. Special YAG laser and dual-frequency eyewear is available for work with frequency-doubled YAG and other IR lasers which have a visible beam, but it is more expensive, and IR-pumped green laser products do not always specify whether such extra protection is needed.

Eyewear is rated for optical density (OD), which is the base-10 logarithm of the attenuation factor by which the optical filter reduces beam power. For example, eyewear with OD 3 will reduce the beam power in the specified wavelength range by a factor of 1,000. In addition to an optical density sufficient to reduce beam power to below the maximum permissible exposure (see above), laser eyewear used where direct beam exposure is possible should be able to withstand a direct hit from the laser beam without breaking. The protective specifications (wavelengths and optical densities) are usually printed on the goggles, generally near the top of the unit. In the European Community, manufacturers are required by European norm EN 207 to specify the maximum power rating rather than the optical density.

Interlocks and automatic shutdown

Interlocks are circuits that shut down a laser if some condition is not met, such as if the laser casing or a room door is open. Class 3B and 4 lasers typically provide a connection for an external interlock circuit. Lasers that are class 1 only because the light is contained within an enclosure nearly always have an interlock that disables the laser if that enclosure is opened.

Some systems have electronics that automatically shut down the laser under other conditions. For example, some fiber optic communication systems have circuits that automatically shut down transmission if a fiber is disconnected or broken.

Laser safety officer

In many jurisdictions, organizations that operate lasers are required to appoint a laser safety officer (LSO). The LSO is responsible for ensuring that safety regulations are followed by all other workers in the organization.

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