LASER (Light amplification by stimulated emission of radiation)Fundamental to applications

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The laser light is produces an intense, concentrated, and highly parallel beam of coherent light.  Laser is the outgrowth of maser, a similar device using radio microwaves instead of visible light waves. Some basic principles involved in the operation of laser. Meta stable states, optical pumping, fluorescence, population inversion, resonance, stimulated emission, coherence, polarization, fabry-perot interferometry, cavity oscillation. Most of the principles are already use in some other application but coherence and stimulated emission are the key to realization of maser and laser operation.



Consider a gas enclosed in a vessel containing free atoms having a number of energy levels, at least one to which is Meta stable. White light into these gas atoms can be raise from ground state to excited state. If light intense is high, we can obtain more electrons in excited states which means population inversion. When an electron in one of these excited states spontaneously jumps to the ground state, as it eventually will, it emits a photon of energy hv. This is called fluorescent or phosphorescent radiation. As, the photon passes by another nearby atom in the same Meta stable state, it can, by the principle of resonance, immediately stimulate that atom to radiate a photo of the exact same frequency and return it to its ground state. That stimulated photon has exactly the same frequency, direction, and polarization as the primary photon and exactly the same phase and speed.

            Both of these photons may now be considered primary waves, and upon passing close to other atoms in their Meta stable states, they stimulate them to emission in the same direction with the same phase. However, transition from the ground state to the excited state can also be stimulated, thereby absorbing the primary wave. An excess of stimulate emission therefore requires a population inversion, more atoms in the Meta stable state than the ground state. Thus if the conditions in the gas are right, a chain reaction can be developed, resulting in high-intensity coherent radiation.

The Ruby laser

The ruby is primarily a transparent crystal of corundum doped with trivalent chromium ions. The chromium ions are the active ingredients. The aluminum and oxygen atoms are inert. The ruby crystal is cylindrical in shape. Generally ruby laser one end is highly reflective and other end is close to half silvered. When white light enters into a crystal, absorption by the chromium ions in the blue-green part of the spectrum occurs. The electrons immediately raise excited state and randomly jump back to the ground level, emitting visible red light.

Helium neon gas laser

The helium neon gas laser was a first gas laser operation. Many scientist were tried to make gas lasers because it is inexpensive, unusually stable, and emits continuously, this helium neon laser is widely used in optics laboratories. There are ten times as many helium atoms present in a mixture as there are neon atoms, the orange color of the gaseous discharge is characteristic of neon atoms. The visible spectrum of helium contains lines in the red, yellow, green and blue, so the discharge appears as white light.

The carbon dioxide laser



A high power molecular gas laser is one that operates on carbon dioxide gas molecules. This optical device produces a continuous laser beam with a power output of several kilowatts and at the same time maintains a relatively high degree of purity and coherence.

At present hundreds of different kinds of lasers using many different materials have been made, emitting radiation over a wide range of wavelengths from the ultraviolet at one end of the spectrum to microwave at the other. Modulated laser beams have been used for communication. The modern medical industry is depending upon laser and in future all technology having some kind of lasers. Laser communication is used to communicate small and large distance also. Laser have been used like radar, and determine distances. Lasers also used in all micro level cutting machinery in industries.

Students can make many projects about wireless communication with the help of laser. We can able communicate using with laser beam transmission to hills area in the case of without mobile communication.
               




LASER (Light amplification by stimulated emission of radiation)Fundamental to applications LASER (Light amplification by stimulated emission of radiation)Fundamental to applications Reviewed by knowledge people creators on October 20, 2019 Rating: 5
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