Lasers and their applications

Lasers and their applications

Laser is an acronym for light amplification by stimulated emission of radiation. In the last century many types of lasers have been used for many different applications from welding to surgery to military and even many uses in every day life by harnessing the principles of light and stimulated emission.
To understand how lasers work we must first understand the physics behind light waves. Light is emitted from a source and travels in straight lines and when it strikes an object is either absorbed, reflected, or refracted. Light behaves primarily like a wave and its this wave nature of light that allows lasers to work. Constructive interference is what amplifies light. Since light is a wave it has a frequency calculated by the equation:
f = c/
and
= c/f

where f is the frequency c is the speed of light which is equal to 3.00 x 108 m/s and is the wave length of light. Also waves have crests, the high points of waves, and troughs, the low points. Constructive interference occurs when two waves of the same frequency meet at a crest or trough therefore combining to form a wave that has an amplitude equal to the sum of the individual amplitudes of the original waves. Stimulated emission is the process that the laser works on, which was first proposed by Albert Einstein in 1917. When a sufficient number of atoms, either gas solid or liquid, absorb energy so that they are in an excited state of higher energy stimulated emission can occur. Light of a specific wavelength can produce more light with the same phase and direction these light waves will be coherent. Stimulated emission amplifies the coherency of this radiation and gives the radiation a very narrow beam spread.
The combination of light amplification and stimulated emission creates a laser. Laser light is coherent because the atoms are stimulated to emit waves of light that are in phase creating constructive interference producing a powerful and intense laser light. The emitted light is monochromatic, meaning only one wavelength, and one directional. For a laser to work three components are needed. First a gain medium that can amplify light through it. Second an energy pump source to create a population inversion, (this is a condition when electrons in high energy levels are more numerous than electrons in lower energy levels), in the gain medium. Finally two mirrors that form a resonator cavity where small units of energy released from the atoms called photons move back and forth between the mirrors triggering more stimulated emissions. The energy of a photon is calculated using the equation:
E =hv
where E is the energy of a photon, h is Planck's constant (equal to 6.63 x 10-34) and...

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