14-03-2010, 07:53 AM
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INTRODUCTION TO LASER:-
The word LASER is actually an acronym that stands for
Light Amplification by Stimulated Emission of Radiation .
Based on this principle, a very special kind of light is created,
of a form that doesnâ„¢t exist anywhere in nature. It is one
colour (monochrome) and appears as a tightly bundled,
directed beam. T.H. Maiman, a physicist from California,
USA, succeeded in building the first functioning
laser (ruby laser, with red light) in 1960.
FIRST LASER:-
The Flash Tube is just like a flash on a photo camera,
Its job is to inject the photons in to the ruby. The ruby
It self itâ„¢s the container of the atoms. The ruby was
Polished and was coated with silver, with the emitter
End of the ruby a little thinner, so some light could
escape out. The Quartz tube had the job of
reflecting the photons to maximize the number of
photons staying in the ruby.
LASER CONSTRUCTION:-
A laser system generally consists of three important parts:
¢ An energy source (usually referred to as the pump or pump source).
¢ A gain medium or laser medium.
¢ A mirror, or system of mirrors, forming an optical resonator.
1. Pump source:-
The pump source is the part that provides energy to the laser system. Examples of pump sources include electrical discharges, flashlamps, arc lamps, light from another laser, chemical reactions and even explosive devices. The type of pump source used principally depends on the gain medium, and this also determines how the energy is transmitted to the medium
2. Laser medium:-
The gain medium is the major determining factor of the wavelength of operation, and other properties, of the laser. There are hundreds if not thousands of different gain media in which laser operation has been achieved. The gain medium is excited by the pump source to produce a population inversion, and it is in the gain medium that spontaneous and stimulated emission of photons takes place, leading to the phenomena of optical gain or optical amplification.
3. Optical resonator:-
The optical resonator, or optical cavity, in its simplest form is two parallel mirrors placed around the gain medium. Light from the medium, produced by spontaneous emission, is reflected by the mirrors back into the medium, where it may be amplified by stimulated emission. The light may reflect from the mirrors (and thus pass through the gain medium) many hundreds of times before exiting the cavity.
TYPES OF LASERS:-
There are five types of lasers, which are classified according to the lasing materials employed. The laser type depends on the material used in creating the laser. They are,
Solid state lasers:-
The solid substance that is used for lasing is generally
stimulated by a flashlight or other type of light.
Depending on whether the stimulation is continuous
or intermittent, we will get solid lasers that are in a
continuous beam or a pulsed beam.
Ex:- neodymium-yttrium-aluminum garnet, ruby, Erbium-Holmium,
Titanium sapphire etc.
Gas state lasers:-
In this type of laser, the lasing material is a gaseous material. Helium and helium-neon are the two gases most popularly used to create gas lasers. When CO2 is used, the laser created is an infrared laser. Gas lasers are typically red in color
Liquid lasers:-
The medium is a dye solution, as a result of which the colour
of the laser light can be varied over a wide range.
Semiconductor lasers:-
These lasers are not solid state lasers and are also referred
to as diode lasers. A semi conductor laser is not very powerful
on its own, and is thus generally used in combination with
other devices.
Dye lasers:-
Some organic dyes, such as the very oft used rhodamine G6, have molecules that can be easily excited, because of which tunable lasers with many different frequencies can be achieved. Lasers created from dyes that are either liquid dyes or suspension materials, are known as dye lasers.
ADVANCED PERTINENCES/APPLICATIONS OF LASERS:-
Laser finds its pertinences in many fields such as military, biomedical, scientific,
industrial, optical communications etc¦
Military applications:-
Target designator
Directed energy weapons
Space laser satellite defense system
Guiding munitions
Missile defense
Defensive countermeasures
Ranging
Laser sight
Eye-targeted
Target designator:-
A laser designator is a laser light source which is used to designate a target. Laser designators provide targeting for laser guided bombs, missiles or precision artillery munitions, such as the pave way series of bombs, Lockheed-Martinâ„¢s hellfire or the copperhead round, respectively. When a target is marked by a designator, the beam is invisible and does not shine continuously. Instead, a series of coded pulses of laser-light are fired. These signals bounce off the target into the sky, where they are detected by the seeker on the laser guided munitions, which steers itself towards the centre of the reflected signal. Unless the people being targeted possess laser detection equipment or can hear aircraft overhead, it isextremely difficult for them to tell whether they are being marked or not. Laser designators work best in clear atmospheric conditions. Cloud cover, rain or smoke can make reliable designation of targets difficult or even impossible.
Directed energy weapons:-
The Boeing YAL-1 Airborne Laser Tested, (formerly Airborne Laser) weapons system is a megawatt-class chemical oxygen iodine laser (COIL) mounted inside a modified Boeing 747-400F. It is primarily designed as a missile defense system to destroy tactical ballistic missiles (TBMs), while in boost phase. The aircraft was designated YAL-1A in 2004 by the U.S. Department of Defense.
The YAL-1 with a low-power laser was test-fired in flight, at an airborne target in 2007.A high-energy laser was used to intercept a test target in January 2010.
The ABL does not burn through or disintegrate its target. It heats the missile skin, weakening it, causing failure from high speed flight stress. If proven successful, seven ABL-armed 747s will be built and assigned to two combat theaters. The aircraft were originally slated to enter service in 2008, but development has been slower and costlier than planned. The current plan calls for a prototype ABL to attempt to shoot down a test missile in 2009.
Space laser satellite defense system:-
The satellites would be powered by built-in nuclear warheads “ in theory, the energy from the warhead detonation would be used to pump a series of laser emitters in the missiles or satellites, allowing each satellite to shoot down many incoming warheads simultaneously. The attraction of this approach was that it was thought to be faster than an optical laser, which could only shoot down warheads one at a time, limiting the number of warheads each laser could destroy in the short time 'window' of an attack.
Brilliant Pebbles was a non-nuclear system of satellite-based,watermelon-sized mini-missiles designed to use a high-velocity kinetic warhead. It was designed to operate in conjunction with the Brilliant Eyes sensor system and would have detected and destroyed missiles without any external guidance.
Satellite known as Delta Star to test several sensor related technologies. Delta Star carried an infrared imager, a long-wave infrared imager, an ensemble of imagers and photometers covering several visible and ultraviolet bands as well as a laser detector and ranging device. The satellite observed several ballistic missile launches including some releasing liquid propellant as a countermeasure to detection. .
Laser sight:-
The laser has in most firearms applications been used as a tool to enhance the targeting of other weapon systems. For example, a laser sight is a small, usually visible-light laser placed on a handgun or a rifle and aligned to emit a beam parallel to the barrel. Since a laser beam by definition has low divergence. The laser light appears as a small spot even at long distances; the user places the spot on the desired target and the barrel of the gun is aligned (but not necessarily allowing for bullet drop, windage and the target moving while the bullet travels).
A radar gun or speed gun is a small Doppler radar unit used to detect the speed of objects, especially trucks and automobiles for the purpose of regulating traffic, as well as pitched baseballs, runners or other moving objects in sports. A radar gun does not return information regarding the object's position. It relies on the Doppler Effect applied to a radar beam to measure the speed of objects at which it is pointed. Radar guns may be hand-held or vehicle-mounted.
Most of today's radar guns operate at X, K, Ka, IR Band (infrared), and (in Europe) Ku bands. An alternative technology, LIDAR, uses pulsed laser light.
The radar gun was invented by Bryce K. Brown in March 1954.
Scientific pertinences:-
Spectroscopy:-
Laser spectroscopy has led to advances in the precision with which spectral line frequencies can be measured, and this has fundamental significance for our understanding of basic atomic processes. This precision has been obtained by passing two laser beams through the absorption sample in opposite directions, selectively triggering absorption only in those atoms that have a zero velocity component in the direction of the beams.
Nuclear fusion:-
Laser fusion, also called inertial confinement fusion, is the most frequent fusion reaction on Earth. It is commonly used for experiments relevant to hydrogen bombs. Is relatively simple and cheap in comparison to tokamaks but didnâ„¢t allow continuous fusion and can be ignited discontinuously only.
Laser fusion process:
Medical pertinences:-
Eye surgeries:
Now a days, mostly eye surgeries are done by using the laser technology.Although the terms laser eye surgery and refractive surgery are commonly used as if they were interchangeable, this is not the case. Lasers may be used to treat non-refractive conditions (e.g. to seal a retinal tear).
Surgical removal of tissues:-
The tissues in the human bodies are removed by using
the laser technology.Without touching the body,
we can remove the tissue.
Laser therapy:-
Low level laser therapy (LLLT, also known as photobiomodulation, cold laser therapy and laser biostimulation) is a medical and veterinary treatment which uses low-level lasers or light-emitting diodes tostimulate or inhibit cellular function. The technique is also known by other terms such as laser therapy, "cold laser" and phototherapy (though the latter more accurately refers to light therapy), which may also be used to describe other medical techniques.
Industrial pertinences:-
Holography:-
Holography (from the Greek, -hólos whole + af-grafe writing, drawing) is a technique that allows the light scattered from an object to be recorded and later reconstructed so that it appears as if the object is in the same position relative to the recording medium as it was when recorded. The image changes as the position and orientation of the viewing system changes in exactly the same way as if the object were still present, thus making the recorded image (hologram) appear three dimensional.
Lidar:-
LIDAR (Light Detection And Ranging) is an optical remote sensing technology that measures properties of scattered light to find range and/or other information of a distant target. The prevalent method to determine distance to an object or surface is to use laser pulses.
¢ Upcoming technologies:-
'The laser will ultimately fulfill its promise in the huge field that was called analytical chemistry, and become increasingly prolific in diagnostic medicine. Spectral properties and spatial coherence will assure this as the lab shrinks to chip scale. The future world of pharmagenomics will rely on lasers for genetic typing and perhaps for activation of the appropriate therapeutic course.â„¢
¢ Conclusion:-
Laser has got many applications or pertinences in many fields such as military, scientific, medical, industrial etc¦. This technology has been enhanced a lot in the past 40 years. This laser technology has many advantages such as eye surgeries, holograms, therapies etc and at the same it can be used for the destructive and devastative purposes also. So, we have to use this full-fledged laser technology in our positive Endeavour™s only.
