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Lasers 101: What is a Laser?

LASER is an acronym which stands for Light Amplification by Stimulated Emission of Radiation. The energy generated by the laser is in or near the optical portion of the electromagnetic spectrum (see Figure 1). Energy is amplified to extremely high intensity by an atomic process called stimulated emission. The color of laser light is normally expressed in terms of the laser's wavelength: nanometer (nm) is the most common unit used.

Figure 1: The optical spectrum. Laser light is non-ionizing and ranges from the ultra-violet (100-400nm), visible (400-700nm), and infrared (700nm-1mm).

Laser Hazards & Beam Hazards

The laser produces an intense, highly directional beam of light. If directed, reflected, or focused upon an object, laser light will be partially absorbed, raising the temperature of the surface and/or the interior of the object, potentially causing an alteration or deformation of the material. Lasers can also cause tissue damage. Today, most high-power lasers are designed to minimize access to laser radiation during normal operation. Lower-power lasers may emit levels of laser light that are not a hazard.

Laser Hazards Classification

The Center for Devices and Radiological Health, a division of the Food and Drug Administration regulates the manufacturing and classification of laser products. The laser classes help group lasers by their hazard potential, and identifies these classes based on their optical emission (wavelength, exposure time, output power).

General Guidelines for CW Laser Classification

Class I	Lasers or laser systems that do not, under normal operating conditions, pose a hazard.
Class IIa	Low power visible lasers or laser systems that are not intended for prolonged viewing, and under normal operating conditions will not produce a hazard if the beam is viewed directly for periods not exceeding 1000 seconds.
Class II	Low power visible lasers or laser systems which, because of the normal human aversion response, do not normally present a hazard, but may present some potential for hazard if viewed directly for extended periods of time (like many conventional light sources).
Class IIIa	Lasers or laser systems having a CAUTION label that normally would not injure the eye if viewed for only momentary periods (within the aversion response period) with the unaided eye, but may present a greater hazard if viewed using collecting optics. Another group of Class 3a lasers have DANGER labels and are capable of exceeding permissible exposure levels for the eye in 0.25 seconds and still pose a low risk of injury.
Class IIIb	Lasers or laser systems that can produce a hazard if viewed directly. This includes intrabeam viewing of specular reflections. Normally, Class 3B lasers will not produce a hazardous diffuse reflection.
Class IV	Lasers or laser systems that produce a hazard not only from direct or specular reflections, but may also produce hazardous diffuse reflections. Such lasers may produce significant skin hazards as well as fire hazards.

The information mentioned here is intended to be an introduction to lasers and laser safety, and should not be considered to be an authoritarian guide. A better informed user has the knowledge to make safer decisions: learn about safety procedures for your class of laser, and the next class higher.

An excellent source for laser safety is the Laser Institute of America. Very useful resources include their web based Safety Bulletin, and printed Laser Safety Guide.

BEA Lasers is a Corporate Member of the Laser Institute of America. BEA Lasers is a division of BEA Electro Sales, Inc.

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