Laser technology has revolutionized dermatologic cosmetic treatments, eye surgery and many other surgical techniques in modern medicine during the last two decades. Laser hair removal has proven itself to be the best method for permanent hair reduction with sustained cosmetic results compared to other methods of hair removal. This article is the first of a series of articles on lasers in dermatology and will review the basics of medical laser technology.
What is Laser?
Laser is an acronym for Light Amplification by Stimulated Emission of Radiation. To understand what is meant by the ‘light amplification’ and ‘stimulated emission of radiation’, one needs to learn a little about the quantum mechanics in physics.
All atoms (the basic unit of matter) have electrons circling the nucleus in stable orbits. Stability of electrons means that they remain in the same orbit throughout without jumping between the different orbits. The exception is the outer electron, which can move between the orbits by either absorbing or expelling a unit of light energy, called a photon.
What is Meant by Stimulated Emission of Radiation in Lasers?
In normal state of an atom, a spontaneous emission of light energy occurs when an excited electron falls back to a resting orbit, releasing a photon of energy. In laser systems, special media ensure that there are more atoms with excited electrons to produce a continuous supply of the light energy.
In the stimulated emission of radiation in lasers, when a photon of light enters the laser medium with excited electrons and is absorbed by an electron, which falls back into the resting orbit, releasing two identical photons. These photons then enter two other atoms with excited electrons and a chain reaction is thus set up. This provides a continuous supply of light beams from the laser energy source. The next step in the production of laser light is to amplify and orient the light rays.
What is Meant by Light Amplification in Laser?
Light amplification in laser means orienting the beams of light from a flash lamp source so that the light waves move parallel to each other. This enhances their energy levels. Laser machines use an optical resonator for this purpose. This is a cylindrical chamber with reflecting mirrors at both ends and an absorbing lining all around (to absorb and eliminate scattering light).
The laser medium (containing atoms with excited electrons), in the form of solids, gases or dyes are filled within the chamber. When the laser machine is put to work, spontaneous emission of laser light occurs, with the lining inside absorbing the scattering lights, and through reflection, the beams are amplified and sent out through a release mechanism from one end of the optical resonator chamber. This, in short, is the origin of the laser light beam.
What is the Difference between Laser Light and Ordinary Light?
There are three distinctive characteristics unique to laser light compared to the normal, natural light:
- Laser light is collimated: It travels in a single direction without any fluctuation or divergence, even over long distance. Ordinary light waves, in contrast, are scattered in every direction and lose their brightness and intensity within no time.
- Laser light is monochromatic: This means that the laser light contains only one color or a very narrow range of colors of same frequency. Ordinary light has a wide variety of colors of varying wavelengths. These include the visible light, the ultraviolet light, infra red light etc.
- Laser light is coherent: The light rays emanating from a laser source are in step, moving together, both in space and time. In ordinary light, the rays are incoherent (out of step with each other) and travel in different directions and are of different frequencies.
The characteristics and features of different types of medical lasers depend upon the types of medium used in laser systems.
Related Article
Reference
- Eubanks SW. Lasers in Dermatology. In Dermatology Secrets. 1996: 332-340, Eds. JE Fitzpatrick & JL Aeling; Hanley & Belfus, Inc.
 |
 |
