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AN INTRODUCTION TO LASERS


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Lasers play a pivotal role in our daily life. One can find their use in everything from dental drills to high speed cutting machines. Laser beams are very much different from ordinary beam of light. In this article I would like to discuss about some of the fundamental facts about lasers like mechanism behind lasers operation, properties of laser, components of lasers and their uses in various fields.

 

LASER

“LASER”, the term which is abbreviated for Light Amplification by Stimulated Emission of Radiation is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation.

Lasers are basically evolved from ‘MASERS’ which means “Microwave Amplification by Stimulated Emission of Radiations”. Unlike Masers which produce only microwaves and radiowaves, lasers produce visible light.

CHARACTERISTICS OF LASER

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COHERENT

The laser beams are in phase with each other over a sufficient time so that interference effects can be visualized. This coherent nature of beams makes the holograms possible

MONOCHROMATIC

The laser beams typically comes from one atomic transition via stimulated emission and hence consist of single wavelength only.

COLLIMATED

Laser beams are very narrow, sharp and highly amplified because of multiple reflections caused by mirrored ends of laser cavity.

WORKING PRINCIPLE OF LASERS

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When an atom receives some energy from the external source it jumps to higher energy states. Similarly, the same electron when falls back from higher energy level to the lower energy level it emits energy either in radiative or in nonradiative transitions. Lasers are the result of radiative transitions i.e. emission of electromagnetic radiations. Laser action is based on the principle of stimulated emission of photons or forced emission which is attained. The stimulated emission is attained when the population of higher energy states has greater population of electrons than the lower energy states which is known as population inversion.

Since the overall single-pass gain is small with the population inversion and stimulated emission and most of the excited electrons may undergo spontaneous emission a resonator is used to make a positive feedback mechanism.

An optical resonator consists of two concave or flat mirrors, one on each end so as to reflect the photons back and forth and amplify the laser light produced by stimulated emission. The front mirror is made 95 – 99% reflective whereas the back mirror is almost 100% reflective. The low reflectivity of front mirror permits to escape the generated laser beam outside the laser device.

A lot many types of lasers are available for various uses like research, medical, industrial, and commercial uses as shown in the flowchart below.

 

 

 

TYPES OF LASERS

A lot many types of lasers are available for various uses like research, medical, industrial, and commercial uses as shown in the flowchart below.

 

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USES OF LASERS

Lasers were initially referred to as an invention looking for a job. Gradually, it gained importance in many fields like medical for various skin treatments and surgery purposes; in military devices; in fact various scientific researches are based on lasers. Lasers have now been used in many consumer devices in CDs and DVD players, scanners and printers. Lasers are also being used to carry information in fiber optics as they have been proved to be the fastest mode of communication.

 

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