The word “laser” is an acronym for light amplification by stimulated emission of radiation. A laser is a device that produces an intense beam by amplifying light.
The radiation produced for surgical lasers is in the electromagnetic spectrum with a wavelength that ranges from 200 to 400 nm (near-UV radiation), 400 to 700 nm (visible radiation), 700 to 1000 nm (near-infrared radiation), and more than 1000 nm (infrared radiation). The most prominent physical feature of the radiation is its wavelength, which determines its visibility. The three most commonly used types of surgical lasers are (1) the argon laser, which is within the visible portion of the electromagnetic spectrum; (2) the neodymium:yttrium–aluminum–garnet (Nd:YAG) laser; and (3) the carbon dioxide (CO2) laser.
Stimulated emission is the main source of laser energy. However, the energy of stimulated emission needs to be amplified to produce an intense beam. When the laser pump activates the active medium, the active medium starts having more atoms in an excited state. As atoms in the excited state release photons, this induces the emission of the photons from other atoms through a chain reaction.
One of the distinctive features of the light is its highly concentrated energy per unit area. Beams forming the light synchronously occur parallel with each other, which makes it possible for the laser to travel a certain distance without divergence. It is monochromatic. The wavelength of the light is one of the factors determining the physical characteristics of the laser and its interaction with tissue.
The current model of stimulated emission is described by quantum physics, which defines different energy levels of electrons while revolving around the nucleus in different levels of orbit. In this model, a stable electron in a normal state makes a transition to a higher but unstable energy level by absorbing a photon (absorption). This unstable electron with high energy ultimately may return to the original stable level spontaneously (spontaneous emission). Alternately, this emission can be induced by a forced interaction between one photon and the unstable electron to release a new photon (stimulated emission), which is the basis of laser energy.
A laser primarily consists of three main components: (1) an active medium; (2) a stimulation (excitation) mechanism, which is the power source or a laser pump; and (3) an optical chamber (feedback mechanism) (Figure 6–1). The active medium is the component where the laser radiation is generated. The function of the active medium is to supply a source of stimulated atoms, molecules, and ions. It may be in a solid, gaseous, or liquid state. Different types of lasers are named based on what is used as an active medium. Lasers with a solid state of active medium are the Nd:YAG, ruby, and ...