Laser, acronym for light amplification by stimulated emission of radiation. Lasers are devices that amplify light and produce coherent light beams, ranging from infrared to ultraviolet. A light beam is coherent when its waves, or photons, propagate in step, or in phase, with one another. Laser light, therefore, can be made extremely intense, highly directional, very pure in colour (frequency) and applied in laser
therapy methods. Laser devices now extend into the X-ray frequency range. Lasers harness atoms to store and emit light in a coherent fashion. The electrons in the atoms of a laser medium are first pumped, or energized, to an excited state by an energy source. They are then "stimulated" by external photons to emit the stored energy in the form of photons, a process known as stimulated emission. The photons emitted have a frequency characteristic of the atoms and travel in step with the stimulating photons. These photons in turn impinge on other excited atoms to release more photons, which are used
in light laser therapy and in cold
laser therapy. Light amplification is achieved as the photons move back and forth between two parallel mirrors, triggering further stimulated emissions. At the same time the intense, directional, and monochromatic laser light "leaks" through one of the mirrors, which is only partially silvered.
According to the laser medium used, lasers are generally classified as solid state, gas, semiconductor, liquid, and they are all foundation stone for laser therapy methods.
The most common solid laser media are rods of ruby crystals and neodymium-doped glasses and crystals. The ends of the rod are fashioned into two parallel surfaces coated with a highly reflecting non-metallic film. Solid-state lasers offer the highest power output. They are usually operated in a pulsed manner to generate a burst of light over a short time. Bursts as short as 12 Ч 10-15 sec have been achieved, which are useful in studying physical phenomena of very brief duration. Pumping is achieved with light from xenon flash tubes, arc lamps, or metal-vapour lamps.
The laser medium of a gas laser can be a pure gas, a mixture of gases, or even metal vapour, and is usually contained in a cylindrical glass or quartz tube. Laser therapy methods
embrace this laser medium either.
Two mirrors are located outside the ends of the tube to form the laser cavity. Gas lasers are pumped by ultraviolet light, electron beams, electric current, or chemical reactions. The helium-neon laser is known for its high frequency stability, colour purity, and minimal beam spread. Carbon dioxide lasers are very efficient, and consequently they are the most powerful continuous wave (CW) lasers. The most compact of lasers, the semiconductor laser usually consists of a junction between layers of semiconductors with different electrical conducting properties. The laser cavity is confined to the junction region by means of two reflective boundaries. Gallium arsenide is the semiconductor most commonly used. Semiconductor lasers are pumped by the direct application of electrical current across the junction, and they can be operated in the CW mode with better than 50 per cent efficiency. New laser therapy methods that permit even more efficient use of energy have been devised. It involves mounting tiny lasers vertically in such circuits, to a density of more than a million per square centimetre, which is
perfect for cold laser therapy.
Thus developed, laser therapy metods
have not only abridged the healing time but also enhanced the therapeutic consequences of light laser therapy and cold laser therapy. The most common liquid laser media are inorganic dyes contained in glass vessels. They are pumped by intense flash lamps in a pulse mode or by a gas laser in the CW mode. The frequency of a tunable dye laser can be adjusted with the help of a prism inside the laser cavity. Free-electron lasers are lasers using beams of electrons unattached to atoms and spiralling around magnetic field lines to produce laser radiation, are now becoming important research instruments for light laser therapy and cold laser therapy. Healing is frequently carried out by limited irradiation on damage/ache spot, but it can also be done on remote points like local lymph nodes and cervical daring roots. Ache elimination can often be achieved in a couple of sessions. Prescribed intensity of skin pigmentation processing
must be carefully calculated.