Lasers have become increasingly important research tools in Medicine, Physics, Chemistry, Geology, Biology and Engineering. If improperly used or controlled, lasers can produce injuries (including burns, blindness, or electrocution) to operators and other personnel, including uninitiated visitors to laboratories, and cause significant damage to property. Individual users of all lasers must be adequately trained to ensure full understanding of the safety practices outlined in The University of Texas Laser Safety Policy. The Laser Safety procedures here at the University follow the requirements of the Texas Department of Health Bureau of Radiation Control, and the guidelines from the American National Standards Institute (ANSI) as specified in the ANSI Standards Z136.1, “The Safe Use of Lasers.”
WHAT IS A LASER?
LASER is an acronym that 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. Energy is amplified to extremely high intensity by an atomic process called stimulated emission. The term “radiation” is often misinterpreted because the term is also used to describe radioactive materials or ionizing radiation. The use of the word in this context, however, refers to an energy transfer. Energy moves from one location to another by conduction, convection, and radiation. The color of laser light is normally expressed in terms of the laser’s wavelength. The most common unit used in expressing a laser’s wavelength is a nanometer (nm). There are one billion nanometers in one meter (1 nm = 1 X 10-9 m). Laser light is nonionizing and includes ultra-violet (100-400nm), visible (400-700nm), and infrared (700nm1mm).
Every electromagnetic wave exhibits a unique frequency, and wavelength associated with that frequency. Just as red light has its own distinct frequency and wavelength, so do all the other colors. Orange, yellow, green, and blue each exhibit unique frequencies and wavelengths. While we can perceive these electromagnetic waves in their corresponding colors, we cannot see the rest of the electromagnetic spectrum. Most of the electromagnetic spectrum is invisible, and exhibits frequencies that traverse its entire breadth. Exhibiting the highest frequencies are gamma rays, x-rays and ultraviolet light. Infrared radiation, microwaves, and radio waves occupy the lower frequencies of the spectrum. Visible light falls within a very narrow range in between.
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. These properties which have been applied to laser surgery and materials processing can also cause tissue damage. In addition to these obvious thermal effects upon tissue, there can also be photochemical effects when the wavelength of the laser radiation is sufficiently short, i.e., in the ultraviolet or blue region of the spectrum. 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. The human body is vulnerable to the output of certain lasers, and under certain circumstances, exposure can result in damage to the eye and skin. Research relating to injury thresholds of the eye and skin has been performed in order to understand the biological hazards of laser radiation. It is now widely accepted that the human eye is more vulnerable to injury than human skin. The cornea (the clear, outer front surface of the eye’s optics), unlike the skin, does not have an external layer of dead cells to protect it from the environment. In the far-ultraviolet regions of the...