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Laser Safety



Laser Characteristics

Laser Light has three unique characteristics that make it different than "ordinary" light. Monochromatic means that it consist of one single color or wavelength. Even though some lasers can generator more than one wavelength, the light is extreme "pure" and consists of a very narrow spectral range. Directional means that the beam is very well collimated and travels over long distances with very little spread in diameter. Coherent means that all individual waves of light are moving precisely together through time and space, or are in phase. The effect of one wave enhances the strength of every other wave, so that the overall effect of coherent light is much greater than if the waves were not in phase.

These three properties of laser light are what can make it more of a hazard than ordinary light. Laser light can deposit a lot of energy within a small area.

Eye Safety

The safe use of lasers requires that all laser users, and everyone near the laser system, are aware of the dangers involved. The safe use of the laser depends upon the user being familiar with the instrument and the characteristics of laser light.

Direct eye contact with the output beam from the laser will cause serious damage and possible blindness.

Laser beams can ignite volatile substances such as alcohol, gasoline, ether and other solvents, and can damage light-sensitive elements in video cameras, photo multipliers and photodiodes. Reflected beams may also cause damage, for these reasons, and others, the user is advised to follow the precautions.

The DPSS Lasers short wavelength poses extreme hazards for the operator's eyes. Wear safety glasses or goggles while operating any laser system.
1. Never look directly into the laser light source or at scattered laser light from any reflective surface.
2. Maintain experimental setups at low heights to prevent inadvertent beam-eye encounter at eye level.
3. Never use the eye to align or orient the beam looking into its source.
4. As a precaution against accidental exposure to the output beam or its reflection, those using the system should wear laser safety glasses or goggles as required by the wavelength being generated.

Of particular importance in prevention of laser hazards is eyewear. Laser protective eyewear is usually made of filters that absorb and/or reflect specific wavelengths of laser light. An important factor to look for in choosing laser protective eyewear is the optical density (OD) of the lenses. The higher the OD, the less the light that is transmitted to the eye. The OD must be chosen so as not to impair vision significantly, yet at the same time, must be chosen so as to be capable of reducing the laser light to the maximum permissible exposure (MPE). When choosing laser protective eyewear, it is also important to select eyewear that is designed to protect against the wavelengths of the laser light that will be used. Eyewear designed to filter shorter wavelengths of light are not appropriate for use with lasers that emit longer wavelengths of light. Finally, it is also important that some attention be paid to the style of the laser protective eyewear so that comfort to the wearer is maximized. Laser protective eyewear cannot protect personnel if not worn.

Laser safety glasses can present a hazard as well as benefit. While they protect the eye from potentially damaging exposure, they block light at the laser wavelengths, which prevents the operator from seeing the beam. Therefore, use extreme caution even when using safety glasses.

Controlling Safety

If the laser beam is reflected or scattered from various objects, it is very dangerous. Avoid physical contact with the laser beam. The high spectral intensity and short wavelength may cause tissue damage which is not immediately evident.
1. Do not permit any reflective object in the path of the beam. Scattering the beam from a reflective surface can be very damaging to the eyes or skin.
2. Block the beam when not in use.
3. Turn the beam off, preventing stray reflections from occurring either between experiments or when moving the laser.
4. If possible, have an enclosed path for the laser beam.
5. Always point the laser at a specific target, such as a power meter.
6. Limit access to the laser to qualified users who are familiar with laser safety practices and who are aware of the dangers involved.
7. Post warning signs indicating the laser is being used.
8. Never point the laser beam at anyone's' eyes.

Electrical Safety

The power supply is low voltage high current that is more likely to destroy the pump diode laser than to do any real personal or property damage. However, the current involved can make marginal connections or thin wires hot enough to cause problems.

The laser head is enclosed in a protective housing which prevents human access in excess of the limits of Class 1 radiation except for the output beam which is Class IIIb [CFR1040.10 (f) (1) and table 1-A/EN 60825-1, clause 4.2].

No user serviceable parts. Do not attempt to disassemble laser head or power supply. Disassembly of laser head or power supply may exposure the user to hazardous electrical or optical energies.

Additional Info

For US manufacturers of laser products, the standard of principal importance is the regulation of the Center for Devices and Radiological Health (CDRH), Food and Drug Administration (FDA), which regulates product performance. All laser products sold in the USA since August 1976 must be certified by the manufacturer as meeting certain product performance (safety) standards, and each laser must bear a label indicating compliance with the standard and denoting the laser hazard classification.

The governmental standards and requirements specify that the laser must be classified according to the output power or energy and the laser wavelength. DPSS laser are classified as Class IIIb based on 21 CFR, subchapter J, part II, section 1040-10 (d). According to the European Community standards, DPSS laser are classified as Class 3B based on EN 60825-1, clause 9.

Refer to Figure-1 for a description of all required safety labels. These include warning labels near apertures through which laser radiation is emitted and labels of certification and identification [CFR 1040.10(g), CFR 1010.2, and CFR 1010.3/EN60825-1, Clause 5].

1. Laser Institute of America, 4100 Executive Park Drive, Cincinnati, OH 45241 (Safety Guide)
2. America National Standards Institute, Inc. 1430 Broadway, New York, NY 10018 (Safety Booklet)

Warning Label Radiation Aperture Label Identification & Certification label


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