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Lasers HISTORY OF LASER PRODUCTION The roots of laser mechanism are very modern. In 1900 German physicist Max Planck presented an explanation of why the colors of a glowing hot body may change with temperature. He also proposed discrete quantum theory saying that radiations come in discrete quantities called quanta. Therefore radiations are not only a series of waves but a stream of particles called photons.
By 1917, Einstein has outlined the principles underlying the production of laser radiation as a part of quantum theory. Rudolph W. Landenburg in 1929 confirmed the existence of stimulated emission and negative absorption. Lamb and Rutherford invented stimulated emission in hydrogen spectrum and thereby demonstrated it for the first time. Kastler almost revolutionized the laser world by proposing method of optical pumping. PHYSICAL PRINCIPLES OF LASER PRODUCTION The word laser is an acronym for light amplification by the stimulated emission of radiation.
It refers to the production of beam of radiation which differs from ordinary light in following three ways. Firstly lasers are of single specific wave length and hence of a defined frequency, called as mono chromaticity. Second distinct feature is coherence. Laser radiation is not only of the same wave length but also in phase, that is to say the peaks and troughs of the electric and magnetic fields all occur at the same time.
This is called temporal coherence. Furthermore, they are traveling in same direction which is called spatial coherence. Thirdly as a consequence of spatial coherence lasers remain in a parallel beam. Because the radiations do not diverge the energy is propagated over very long distances. This is called collimation. This property makes laser invaluable for measurement and aiming purposes.
Electrons of an individual atom exist as a cloud of negative charges circling the positively charged nucleus. According to quantum theory, electrons can occupy certain energy levels or shells around the nucleus. The electrons in outermost orbit or shell are most easily affected by outside forces. If the atom is given additional energy, say by heating, these outer electrons can be made to occupy higher energy levels. And if enough energy is added to the atom, an outer electron may gain sufficient energy to free itself from the pull of nucleus. The atom then may become positively charged ion and the electron a free negative charge.
Photons themselves if absorbed, can give energy to an atom, this causes excitation. For absorption of the photon to occur its wavelength must correspond exactly to the difference in energy between the existing state of the electron and a possible higher energy level. Similarly if the electron is already in higher energy state and can move to a lower level with a difference that corresponds to the energy of stimulating photon it may do so by giving out a photon of its own identical to that of colliding photon. This process is called stimulated emission and this is nothing but physical principle of LASER production.
USES OF LASER There are many different uses of laser in modern world. Its use in laser printers, laser pointers, for cutting hard materials like iron and steel are some commonest use. It has also spread its wing to military where laser is used in identification of target and ranging. Presently its being widely used in manufacturing compact discs and DVDs.
Cinemas and animations are no exceptions. Most important ingly it is being used to do very precise internal surgery, skin surgery and eye surgery etc. DURING THE EYE SURGERY there are certain basic principles of laser are involved. There would be an Analyzer which is specifically designed to deliver wave front data needed to perform safe and successful wave front guided laser vision correction. All components such as the user interface, resolution and algorithms have to be optimized. All necessary treatment and patient parameters are transferred from the Analyzer to the laser wave systems.
The software inside the laser computer then calculates the appropriate correction pattern. The ophthalmologist may, however, decide to change individual parameters at any stage of the process. Any required correction to the optical path of the eye is then enabled via system module on the cornea. Working in the visible spectrum, the Analyzer is designed to make wave front measurements by utilizing the operating principle, which works on the same principle as the human eye. In order to perform a measurement, an image of the measurement spots is projected onto the retina. This allows the ophthalmologist to constantly verify that the image has been taken properly and that all measurement spots are actually valid.
The application of this measurement principle allows for the detection of inaccurate readings caused by local obstructions. This allows the Analyzer to exclusively deliver valid data and minimizes the risk of false treatment. Automatic measurement release ensures that only centered measurements will be taken into account. Proprietary Wave Light data processing software allows for the registration and recording of valid measurements even with serious eye conditions. Conclusively, in the present world it is difficult to count the uses of LASER. LASER which was an unknown thing at the beginning of century is so much involved in our day today use that without it, we may go a century behind at the count of development.
References 1. Basford J. R. Low intensity laser therapy; still not established clinical tool. Lasers surg. med. , 16, 331 - 342. 2.
Baxter G. D. Therapeutic lasers; Theory and Practice. Edinburgh; Churchill Livingstone. 3. Van Der Zypen E. The use of laser in eye surgery: morphological principles.
Ophthalmol Clinic. 1985; 25 (3): 21 - 52 4. M. Stoker. Basic principles of lasers.
Anaesthesia & intensive care medicine, Volume 6; 12, 402 404.
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