Laser Technology

[Stanford University]

Laser technology is the process of creating a narrow, intense beam of light using a device called a laser. The word "laser" is an acronym for "Light Amplification by Stimulated Emission of Radiation".

A laser is a device that emits a beam of coherent light through an optical amplification process. There are many types of lasers including gas lasers, fiber lasers, solid state lasers, dye lasers, diode lasers and excimer lasers. All of these laser types share a basic set of components.

An external energy source excites the atoms in a medium, such as a gas, solid, or semiconductor. The excited atoms move to a higher energy level. When the atoms return to their original energy level, they emit a photon. The photons strike other atoms, creating more photons.The photons bounce back and forth between mirrors in the laser, amplifying the light. The amplified light passes through a partially reflective mirror, creating a laser beam.

Please refer to the following for more information:

• Wikipedia: Laser

Laser light is produced when electrons in atoms in optical materials such as glass, crystals or gases absorb energy from an electric current or light. The extra energy "excites" the electrons, causing them to move from low-energy orbits around the nucleus to higher-energy orbits. 

Lasers exploit the quantum properties of atoms, absorbing and radiating particles of light (called photons). When electrons in atoms return to their normal orbits (or "ground state"), either spontaneously or when "stimulated" by light or another energy source (in some cases even another laser beam), they emit more photons. 

Light moves in waves. Ordinary visible light, such as that from a household light bulb or flashlight, contains many wavelengths, or colors, and is incoherent, meaning that the peaks and troughs of the light waves travel at different wavelengths and in different directions. 

In a laser beam, the light waves are "coherent," meaning the beam of photons moves in the same direction with the same wavelength. This is achieved by sending charged electrons through an optical "gain medium," a solid material such as glass or gas. 

The specific wavelength of light is determined by the energy released when the excited electrons drop to a lower orbit. The level of energy introduced can be adjusted based on the materials in the gain medium to produce the desired color of the beam. 

Mirrors on one side of the laser's optical material reflect the photons back at the electrons. The space, or "cavity," between the mirrors is designed so the photons needed for a particular type of optical gain medium are fed back into the medium to stimulate the emission of nearly identical clones of the photons. They all move in the same direction and speed, bouncing off another mirror on the other side, repeating the cloning process. 

Two becomes four, four becomes eight, and so on, until the photons are amplified enough that they travel through the mirrors and optical material in perfect unison. Think of them as synchronized band members in a Rose Parade. This unison gives the laser its power. A laser beam can remain sharply focused over great distances, even to the moon and Earth.

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