Laser, Action, Einstein Theory of Laser, Types, Applications in Industry

TERM PAPER

LASER, ACTION, EINSTEIN THEORY OF LASER, TYPES, APPLICATIONS IN INDUSTRY & MEDICAL FIELD

SUBJECT: CURRENT, ELECTRICITY & MODERN PHYSICS SUBJECT CODE: PHY-113 SUBMITTED TO: Dr. AMRITA SAXENA SUBMITTED BY: JAGDEEP SINGH SECTION: C7802 ROLL No.:RC7802A21 REG. No.: 10804440

CONTENTS •

Acknowledgement

•

Introduction

•

Laser action

•

Einstein theory of laser

•

Types of lasers

1. Based on energy level 2. Based on the material used •

Applications

•

Recent discoveries

•

Recent applications

•

References

ACKNOWLEDGEMENT

For the completion of this term paper I would like to acknowledge my respected teacher Dr .AMRITA SAXENA who was always worthily helpful to help me in my queries in different aspects. I would also like acknowledge my friends who helped me a lot in the completion f this and were always there at one call.

JAGDEEP SINGH

INTRODUCTION The name LASER is an acronym for Light Amplification by the Stimulated Emission of Radiation.

Light is really an electromagnetic wave. Each wave has brightness and color, and vibrates at a certain angle, so-called polarization. This is also true for laser light but it is more parallel than any other light source. Every part of the beam has (almost) the exact same direction and the beam will therefore diverge very little. With a good laser an object at a distance of 1 km (0.6 mile) can be illuminated with a dot about 60 mm (2.3 inches) in radius.

As it is so parallel it can also be focused to very small diameters where the concentration of light energy becomes so great that you can cut, drill or turn with the beam. It also makes it possible to illuminate and examine very tiny details. It is this property that is used in surgical appliances and in CD players. It can also be made very monochromic, so that just one light wavelength is present. This is not the case with ordinary light sources. White light contains all the colors in the spectrum, but even a colored light, such as a red LED (light emitting diode) contains a continuous interval of red wavelengths. On the other hand, laser emissions are not usually very strong when it comes to energy content. A very powerful laser of the kind that is used in a laser show does not give off more light than an ordinary streetlight; the difference is in how parallel it is.

Before the Laser there was the Maser In 1954, Charles Townes and Arthur Schawlow invented the maser (microwave amplification by stimulated emission of radiation), using ammonia gas and microwave radiation - the maser was invented before the (optical) laser. The technology is very close but does not use a visible light. On March 24, 1959, Charles Townes and Arthur Schawlow were granted a patent for the maser. The maser was used to amplify radio signals and as an ultrasensitive detector for space research. In 1958, Charles Townes and Arthur Schawlow theorized and published papers about a visible laser, an invention that would use infrared and/or visible spectrum light, however, they did not proceed with any research at the time. Many different materials can be used as lasers. Some, like the ruby laser, emit short pulses of laser light. Others, like helium-neon gas lasers or liquid dye lasers emit a continuous beam of light.

LASER ACTION Lasers are possible because of the way light interacts with electrons. Electrons exist at specific energy levels or states characteristic of that particular atom or molecule. The energy levels can be imagined as rings or orbits around a nucleus. Electrons in outer rings are at higher energy levels than those in inner rings. Electrons can be bumped up to higher energy levels by the injection of energy-for example, by a flash of light. When an electron drops from an outer to an inner level, "excess" energy is given off as light. The wavelength or color of the emitted light is precisely related to the amount of energy released. Depending on the particular lasing material being used, specific wavelengths of light are absorbed (to energize or excite the electrons) and specific wavelengths are emitted (when the electrons fall back to their initial level). In a cylinder a fully reflecting mirror is placed on one end and a partially reflecting mirror on the other. A high-intensity lamp is spiraled around the ruby cylinder to provide a flash of white light that triggers the laser action. The green and blue wavelengths in the flash excite electrons in the atoms to a higher energy level. Upon returning to their normal state, the electrons emit their characteristic ruby-red light. The mirrors reflect some of this light back and forth inside the ruby crystal, stimulating other excited chromium atoms to produce more red light, until the light pulse builds up to high power and drains the energy stored in the crystal. High-voltage electricity causes the quartz flash tube to emit an intense burst of light, exciting some of the atoms in the ruby crystal to higher energy levels. At a specific energy level, some atoms emit particles of light called photons. At first the photons are emitted in all directions. Photons from one atom stimulate emission of photons from other atoms and the light intensity is rapidly amplified. Mirrors at each end reflect the photons back and forth, continuing this process of stimulated emission and amplification. The photons leave through the partially silvered mirror at one end. This is laser light.

EINSTEIN THEORY OF LASER

Although Einstein did not invent the laser his work laid the foundation. It was Einstein who pointed out that stimulated emission of radiation could occur along with spontaneous emission & absorption. He used his photon mathematics to examine the case of a large collection of atoms full of excess energy and ready to emit a photon at some random time in a random direction. If a stray photon passes by, then the atoms are stimulated by its presence to emit their photons early. More remarkably, the emitted photons go in the

same direction and have exactly the same frequency as the original photon ! Later, as the small crowd of identical photons moves through the rest of the atoms, more and more photons will leave their atoms early to join in the subatomic parade. All it took to invent the laser was for someone to find the right kind of atoms and to add reflecting mirrors to help the stimulated emission along .The acronym LASER means Light Amplification by (using Einstein's ideas about) Stimulated Emission of Radiation. Stimulated Emission Normally atoms and molecules emit light at more or less random times and in random directions and phases. All light created in normal light sources, such as bulbs, candles, neon tubes and even the sun is generated in this way. If energy is stored in the atom and light of the correct wavelength passes close by something else can happen. The atom emits light that is totally synchronous with the passing light. This means that the passing light has been amplified which is necessary for the oscillation taking place between the mirrors in a laser.

Light is normally emitted from atoms or molecules that meet with two conditions. - They have stored energy originating from heat or previous absorption of light - A time has passed since the energy was stored Light emitted in this way goes in random directions, with random phases and at random times. Albert Einstein predicted early in the 1900s that there is also another way for light to be emitted. It can amplify a passing beam, provided three conditions are met: - Energy is stored in the atom (same as above) - Light passes close enough to the atom before the time has expired and the light is emitted in the random fashion described above - The passing light has a wavelength suitable for the atom.

The process taking place in this case is called Stimulated Emission, which, together with feedback in a resonant cavity between mirrors, forms the conditions for laser.

TYPES OF LASER •

ON THE BASIS OF ENERGY LEVEL

1. Two level: In this photon from mata stable state jumps to second level on excitation 2. Three level: In this photon from mata stable state jumps to third level on excitation 3. Four level: In this photon from mata stable state jumps to fourth level on excitation

ON THE BASIS OF MATERIAL USED

GAS LASERS Gas laser Laser gain medium and type

Operation wavelength(s)

632.8 nm (543.5 nm, Helium- 593.9 nm, 611.8 nm, neon laser 1.1523 μm, 1.52 μm, 3.3913 μm)

Pump source

Electrical discharge

Applications and notes

Interferometry, holography, spectroscopy, barcode scanning, alignment, optical demonstrations.

Argon laser

454.6 nm, 488.0 nm, 514.5 nm (351 nm, 363.8, 457.9 nm, 465.8 nm, 476.5 nm, 472.7 Electrical nm, 528.7 nm, also discharge frequency doubled to provide 244 nm, 257 nm)

Retinal phototherapy (for diabetes), lithography, confocal microscopy,spectroscopy pumping other lasers.

Krypton laser

416 nm, 530.9 nm, 568.2 nm, 647.1 nm,

Scientific research, mixed with argon to create "white-light" lasers,

Electrical

676.4 nm, 752.5 nm, 799.3 nm

discharge

light shows.

Many lines throughout Xenon ion visible spectrum Electrical laser extending into the UV discharge and IR.

Scientific research.

Nitrogen laser

Pumping of dye lasers, measuring air pollution, scientific research. Nitrogen lasers can operate superradiantly (without a resonator cavity). Amateur laser construction. See TEA laser

Carbon dioxide laser

337.1 nm


10.6 μm, (9.4 μm)

Transverse (high power) or Material processing (cutting, longitudinal (low welding, etc.), surgery. power) electrical discharge

Carbon 2.6 to 4 μm, 4.8 to 8.3 Electrical monoxide μm discharge laser

Excimer laser

Material processing (engraving, welding, etc.), photoacoustic spectroscopy.

Excimer 193 nm (ArF), 248 nm Ultraviolet lithography for recombination via (KrF), 308 nm (XeCl), semiconductor manufacturing, electrical 353 nm (XeF) laser surgery, LASIK. discharge

CHEMICAL LASERS Chemical laser Used as directed-energy weapons.

Laser gain medium and type


Pump source


2.7 to 2.9 μm for Chemical reaction in a Hydrogen Hydrogen fluoride burning jet of ethylene fluoride laser (<80% Atmospheric and nitrogen trifluoride transmittance) (NF3)

Used in research for laser weaponry by the U.S. DOD, operated in continuous wave mode, can have power in the megawatt range.

~3800 nm (3.6 to Deuterium 4.2 μm) (~90% chemical reaction fluoride laser Atm. transmittance)

MIRACL, Pulsed Energy Projectile & Tactical High Energy Laser

COIL 1.315 μm (<70% (Chemical Atmospheric oxygentransmittance) iodine laser)

Laser weaponry, scientific and materials research, laser Chemical reaction in a jet used in the U.S. military's of singlet delta oxygen Airborne laser, operated in and iodine continuous wave mode, can have power in the megawatt range.

Agil (All 1.315 μm (<70% gas-phase Atmospheric iodine laser) transmittance)

Chemical reaction of chlorine atoms with gaseous hydrazoic acid, resulting in excited Scientific, weaponry, molecules of nitrogen aerospace. chloride, which then pass their energy to the iodine atoms.

DYE LASER Dye laser Laser gain medium and type Dye lasers


Pump source


390-435 nm (stilbene), 460- Other laser, Research, spectroscopy, 515 nm (coumarin 102), 570birthmark removal, isotope

640 nm (rhodamine 6G), many others

flashlamp

separation. The tuning range of the laser depends on which dye is used.

METAL-VAPOR LASERS Laser gain medium and type


Pump source

Printing and typesetting applications, fluorescence excitation examination (ie. in U.S. paper currency printing), scientific research.

Heliumcadmium 441.563 nm, 325 (HeCd) metal- nm vapor laser

Heliummercury 567 nm, 615 nm (HeHg) metalvapor laser Heliumselenium (HeSe) metalvapor laser

up to 24 wavelengths between red and UV


Rare, scientific research, amateur Electrical laser construction. discharge in metal vapor mixed with helium buffer gas. Rare, scientific research, amateur laser construction.

Helium-silver (HeAg) metal- 224.3 vapor laser

Scientific research

Neon-copper (NeCu) metal- 248.6 vapor laser

Electrical discharge in metal Scientific research vapor mixed with neon buffer gas.

Copper vapor 510.6 nm, 578.2 laser nm


Dermatological uses, high speed photography, pump for dye lasers.

Gold vapor laser

Rare, dermatological and photodynamic therapy uses.

627 nm

SOLID-STATE LASER Laser gain medium Operation Pump source and type wavelength(s)

Ruby laser

694.3 nm

Flashlamp

Nd:YAG laser

1.064 μm, (1.32 Flashlamp, μm) laser diode

Er:YAG laser

2.94 μm

Flashlamp, laser diode

Neodymium YLF 1.047 and 1.053 Flashlamp, (Nd:YLF) solid-state μm laser diode laser

Neodymium doped 1.064 μm Yttrium orthovanadate (Nd:YVO4) laser

laser diode


Holography, tattoo removal. The first type of visible light laser invented; May 1960. Material processing, rangefinding, laser target designation, surgery, research, pumping other lasers (combined with frequency doubling to produce a green 532 nm beam). One of the most common high power lasers. Usually pulsed (down to fractions of a nanosecond)

Periodontal scaling, Dentistry

Mostly used for pulsed pumping of certain types of pulsed Ti:sapphire lasers, combined with frequency doubling. Mostly used for continuous pumping of mode-locked Ti:sapphire or dye lasers, in combination with frequency doubling. Also used pulsed for marking and micromachining. A frequency doubled nd:YVO4 laser is also the normal way of making a

green laser pointer.

Neodymium doped yttrium calcium oxoborate Nd:YCa4O(BO3)3 or simply Nd:YCOB

~1.060 μm (~530 nm at second harmonic)

laser diode

Nd:YCOB is a so called "selffrequency doubling" or SFD laser material which is both capable of lasing and which has nonlinear characteristics suitable for second harmonic generation. Such materials have the potential to simplify the design of high brightness green lasers.

~1.062 μm (Silicate Flashlamp, glasses), ~1.054 laser diode μm (Phosphate glasses)

Used in extremely high power (terawatt scale), high energy (megajoules) multiple beam systems for inertial confinement fusion. Nd:Glass lasers are usually frequency tripled to the third harmonic at 351 nm in laser fusion devices.

Titanium sapphire (Ti:sapphire) laser

650-1100 nm

Other laser

Spectroscopy, LIDAR, research. This material is often used in highly-tunable mode-locked infrared lasers to produce ultrashort pulses and in amplifier lasers to produce ultrashort and ultra-intense pulses.

Thulium YAG (Tm:YAG) laser

2.0 μm

Laser diode

LIDAR.

1.03 μm

Laser diode, flashlamp

Optical refrigeration, materials processing, ultrashort pulse research, multiphoton microscopy, LIDAR.

Ytterbium:2O3 (glass 1.03 μm or ceramics) laser

Laser diode

ultrashort pulse research, [3]

Neodymium glass (Nd:Glass) laser

Ytterbium YAG (Yb:YAG) laser

Ytterbium doped glass laser (rod, 1. μm plate/chip, and fiber)

Laser diode.

Fiber version is capable of producing several-kilowatt continuous power, having ~7080% optical-to-optical and ~25% electrical-to-optical efficiency. Material processing: cutting, welding, marking; nonlinear fiber optics: broadband fibernonlinearity based sources, pump for fiber Raman lasers; distributed Raman amplification pump for telecommunications.

Holmium YAG (Ho:YAG) laser

Laser diode

Tissue ablation, kidney stone removal, dentistry.

2.1 μm

Frequency quadrupled Cerium doped Nd:YAG laser lithium strontium(or pumped, Remote atmospheric sensing, calcium) aluminum ~280 to 316 nm excimer laser LIDAR, optics research. fluoride (Ce:LiSAF, pumped, Ce:LiCAF) copper vapor laser pumped.

Promethium 147 doped phosphate 933 nm, 1098 glass (147Pm+3:Glass) nm solid-state laser

Chromium doped chrysoberyl (alexandrite) laser

??

Laser material is radioactive. Once demonstrated in use at LLNL in 1987, room temperature 4 level lasing in 147Pm doped into a leadindium-phosphate glass étalon.

Flashlamp, Typically tuned laser diode, Dermatological uses, LIDAR, laser in the range of mercury arc machining. 700 to 820 nm (for CW mode operation)

Erbium doped and 1.53-1.56 μm erbium-ytterbium codoped glass lasers

Laser diode

These are made in rod, plate/chip, and optical fiber form. Erbium doped fibers are commonly used as optical amplifiers for

telecommunications.

Flashlamp

First 4-level solid state laser (November 1960) developed by Peter Sorokin and Mirek Stevenson at IBM research labs, second laser invented overall (after Maiman's ruby laser), liquid helium cooled, unused today. [1]

Divalent samarium doped calcium 708.5 nm fluoride (Sm:CaF2) laser

Flashlamp

Also invented by Peter Sorokin and Mirek Stevenson at IBM research labs, early 1961. Liquid helium cooled, unused today. [2]

F-center laser.

Ion laser

Spectroscopy

Trivalent uranium doped calcium fluoride (U:CaF2) solid-state laser

2.5 μm

2.3-3.3 μm

SEMICONDUCTOR LASER Laser diode Laser gain medium and type


Pump source


Semiconductor laser diode (general information)

0.4-20 μm, depending on active region material.

Electrical Telecommunications, holography, current printing, weapons, machining, welding, pump sources for other lasers.

GaN

0.4 μm

Optical discs.

AlGaAs

0.63-0.9 μm

Optical discs, laser pointers, data communications. 780 nm Compact Disc player laser is the most common laser type in the world. Solid-state laser pumping, machining, medical.

InGaAsP

1.0-2.1 μm

lead salt

3-20 μm

Vertical cavity surface emitting laser (VCSEL)

850 - 1500 nm, depending on material

Telecommunications, solid-state laser pumping, machining, medical..

Telecommunications

Quantum cascade Mid-infrared to laser far-infrared.

Research,Future applications may include collision-avoidance radar, industrial-process control and medical diagnostics such as breath analyzers.

Hybrid silicon laser

Research

Mid-infrared

OTHER TYPES OF LASERS Laser gain medium and type

Free electron laser

Gas dynamic laser


Pump source

A broad wavelength range (about 100 nm several mm); one relativistic free electron laser electron beam may be tunable over a wavelength range Several lines around 10.5 um; other frequencies may be possible with different gas mixtures


atmospheric research, material science, medical applications.

Spin state Military applications; can population operate in CW mode at several inversion in megawatts optical power. carbon dioxide molecules caused by supersonic

adiabatic expansion of mixture of nitrogen and carbon dioxide

"Nickel-like" X-rays at 7.3 nm Samarium laser wavelength

Lasing in ultra-hot samarium plasma formed by double pulse terawatt scale irradiation fluences created by Rutherford Appleton Laboratory's Nd:glass Vulcan laser. [3]

Raman laser, uses inelastic stimulated Raman scattering 1-2 μm for fiber in a nonlinear version media, mostly fiber, for amplification

Complete 1-2 μm wavelength coverage; distributed optical Other laser, mostly signal amplification for Yb-glass fiber telecommunications; optical lasers solitons generation and amplification

Nuclear pumped See gas lasers laser

Nuclear fission

APPLICATIONS Industrial Applications of Laser

First demonstration of efficient "saturated" operation of a sub– 10 nm X-ray laser, possible applications in high resolution microscopy and holography, operation is close to the "water window" at 2.2 to 4.4 nm where observation of DNA structure and the action of viruses and drugs on cells can be examined.

Research

Today, laser can be found in a broad range of applications within industry, where it can be used for such things as pointing and measuring. In the manufacturing industry, laser is used to measure the ball cylindricity in bearings by observing the dispersion of a laser beam when reflected on the ball. Yet another example is to measure the shadow of a steel band with the help of a laser light to find out the thickness of the band. Within the pulp mill industry the concentration of lye is measured by observing how the laser beam refracts in it. Laser also works as a spirit level and can be used to indicate a flat surface by just sweeping the laser beam along the surface. This is, for instance, used when making walls at building sites. In the mining industry, laser is used to point out the drilling direction.

Laser technologies have also been used within environmental areas. One example is the ability to determine from a distance the environmental toxins in a column of smoke. Other examples are being able to predict and measure the existence of photochemical smog and ozone, both at ground level where it isn't wanted and in the upper layers of the atmosphere where it is needed. Laser is also used to supervise wastewater purification.

Laser works as a light source in all fiber optics in use. It has greater bandwidth (potentially 100,000 times greater) than an ordinary copper cable.

It is insensitive to interference from external electrical and magnetic fields. Crosstalk (hearing someone else's phone call) is of rare occurrence. Fiber optics is used increasingly often in data and telecommunications around the world.

Medicine Laser is used in medicine to improve precision work like surgery. Brain surgery is an example of precision surgery that calls for the surgeon to reach the intended area precisely. To make sure of this, lasers are used both to measure and to point in the area in question. Birthmarks, warts and discoloring of the skin can easily be removed with an unfocused laser. The operations are quick and heal quickly and, best of all, they are less painful than ordinary surgery performed with a

scalpel.

RECENT APPLICATIONS DVD A DVD player contains a laser that is used not because it produces a parallel beam, but rather because the light emerges from a tiny point, which enables it to be focused on the different layers of the disc. By moving the lens sideways - laterally, it is possible to reach areas farther in or out on the disc. By moving the lens along the beam - longitudinally, different depths can be reached in the disc. The information, ones and zeros, is stored in several layers, and only one layer is to be read at a time. Every point on a particular layer is read during every revolution of the disc. In order to make room for a lot of information on every disc, the beam has to be focused on as small an area as possible. This cannot be done with any other light source than a laser. Today this area has been reduced to about half a square micrometer, which yields 2 megabits or 0,25 MB(yte) per mm2. Laser Pointers Laser pointers are made from inexpensive semiconductor lasers that together with a lens produce

a parallel beam of light that can be used to make a bright spot to point with. Their range is very large. If one points at a surface 200 meters (220 yards) distant in the dark, a person standing close to the object being pointed at will have no trouble seeing the shining spot (of course, someone else has to hold the laser). On the other hand, the one holding the pointer will have difficulty seeing the spot. The eternal question of range has more to do with the light's behavior on its way back to the sender than with the length of the beam. Laser Sights Laser sights for rifles and guns can be based on several different principles. Some send a laser beam parallel to the trajectory so that the point of impact becomes visible. This method exposes the marksman. Some project a red dot inside a telescopic sight (instead of cross hairs). In both cases, the dot can be produced with a ring around it. Speed Measurement Using Laser The method the police use to measure car speed is based on a laser signal that is sent towards the target. This beam bounces back and is mixed with light that has not hit the car. The result is an oscillation - the same as when you tune a guitar - with higher frequency (more treble) the faster the target moves. The speed has to be measured straight from the front or from the back. If it is measured at an angle, the speed is underrated. This means that you cannot get false values that are too high. The measurement is dependent on the car having something that reflects well. The license plate is perfect, as are different types of reflecting objects. Fogged surfaces are okay, but reduce the maximum distance. Laser Distance Meter The primary users of laser distance meters today are surveyors and constructors, but the car industry is catching on. Least spectacular is the so-called parking assistance that helps the driver to estimate the distance to the car behind when parking. A more recent application measures the distance to the car in front of the driver when driving on highways or other roads. You simply lock in the distance to the car in front of you in order to maintain that distance. This makes driving more efficient and faster as long as it all works. This kind of laser is found in most robots with mechanical vision. Optical Loudspeaker Cable Any amplifier of worth nowadays has an optical cable for transmission to the loudspeakers. The advantage of this method is that it is insensitive to interference from electromagnetic fields, that is interference from electronic devices and radio transmitters such as cell phones. The light source used as a transmitter is a small laser semiconductor. All equipment using optic cable uses the same standard. For example, the maximum bit rate for broadband applications is today 50100 times higher using optics, but the potential ratio is 10,000 times.

RECENT DISCOVERIES 1964 Townes, Basov and Prokhorov shared the prize for their fundamental work, which led to the construction of lasers. They founded the theory of lasers and described how a laser could be built, originating from a similar appliance for microwaves called the MASER that was introduced during the '50s (The MASER has not been used as much as the laser). However, the first functioning laser was not built by them, but by Maiman in 1960. This was the work that resulted in the big and rather clumsy lasers built in the beginning of the '60s. Still, their theory for the laser effect is the one that fundamentally describes all lasers. Every time you listen to a CD or point with a laser pointer, you hold their discovery in your hand. 1971 Gabor (alone) was given the prize, having founded the basic ideas of the holographic method, which is a famous and spectacular application of laser technology. At first "just" a method of creating 3-D pictures, it has since become a useful tool for the observation of vibrating objects. Much of what we today know about how musical instruments produce their tones is due to the use of holograms.

In addition to holograms that can be bought and hung on a wall, simpler holograms can be found on many other things where you might not expect to find them. Small holograms are present on many credit cards and identity cards in order to make them more difficult to forge. 1981 Bloembergen and Schawlow received the prize for their contribution to the development of laser spectroscopy. One typical application of this is nonlinear optics which means methods of influencing one light beam with another and permanently joining several laser beams (not just mixing them - compare the difference between mixing two substances and making them chemically react with one another). These phenomena mean that a light beam can in principle be steered by another light beam. If in the future someone intends to build an optical computer (that could be much faster and much more efficient in storing data), it would have to be based on a nonlinear optic. When using optical fibers, for example in broadband applications, several of the switches and amplifiers that are used require nonlinear optical effects. 1997 Chu, Cohen-Tannoudji and Phillips et al. received the prize for their developments of methods to cool and trap atoms with laser light which is a method for inducing atoms to relinquish their heat energy to laser light and thus reach lower and lower temperatures. When their temperature sinks very close to absolute zero, atoms form aggregates (make clumps) in a way that reveals some of the innermost aspects of nature. And that is the important application of laser cooling, namely to make us understand more of nature. Very soon after the discovery other scientists started to use the technique to further develop closely related areas. 2000 Alferov and Kroemer were given the prize for their development within the field of semiconductor physics, where they had studied the type of substances that was first used to build semiconductor lasers, that is, the kind of miniature lasers that today have become the cheapest, lightest and smallest. The idea is to produce both the light source and energy supply and place the mirrors in one crystal (less than 1 mm facet, with many sequences). This has become not only the basis for many cheap and portable appliances, but also the foundation in optical information networks.

The CD player, laser writer, laser pointer and the bar code reader the cashier at the supermarket uses, are all based on their discovery.

REFRENCES *NEWAGE PUBLISHER PVT. LTD.,LASERANDNONLINEAROPTICS,P.B LAUD *macmillan publisher,laser theory and application,k.dhyacagrajan,ak.ghatak *universities publishers,laser,e.a siegman *http://www.nobel.org

Laser, Action, Einstein Theory of Laser, Types, Applications in Industry

Recommend Documents