Laser Technology

The acronym LASER stands for Light Amplification by Stimulated Emission of Radiation.

Lasers are devices that produce intense beams of light which are monochromatic, coherent, and highly collimated.The wavelength (color) of laser light is extremely pure(monochromatic) when compared to other sources of light, and all of the photons(energy) that makes up a laser beam  have a fixed phase relation ship(coherence) with respect to one another. Light from a laser typically has very low divergence. It can travel over great distances or can be focused to a very small spot with a brightness which exceeds that of the sun. Because of these properties, lasers are used in wide variety of applications in all walks of life.

The basic concepts of laser were first given by an American scientist, Charles Hard Townes and two Soviet scientists, Alexander Mikhailovich Prokhorov and Nikolai Gennediyevich Basov who shared the coveted Nobel Prize (1964). However, TH Maiman of the Hughes Research Laboratory, California, was the first scientist who experimentally demonstrated laser by flashing light through a ruby crystal, in 1960.

Laser is a powerful source of light having extraordinary properties which are not found in the normal light sources like tungsten lamps, mercury lamps, etc. The unique property of Laser is a powerful source of light having extraordinary properties which are not found in the normal light sources like tungsten lamps, mercury lamps, etc. The unique property of laser is that its light waves travel very long distances with e very little divergence.  The Properties of laser light are monochromaticity,coherence,directionality,high  irradiance etc…

APPLICATIONS OF LASER

Industrial applications

High power lasers have long been used for cutting and welding materials. Today the frames of automobiles are assembled using laser welding robots, complex card board boxes are made with laser-cut dies, and lasers are routinely used to engrave numbers and codes on a wide variety of products. Some less well-known applications include three-dimensional stereolithiography and photolithography.

Marking and Scribing

Lasers are used extensively in production to apply indelible, human and machine-readable marks and codes to a wide variety of products and packaging. Typical applications include marking semi conductor wafers for identification and lot control, removing the black overlay on numeric display pads, engraving gift items, and scribing solar cells and semiconductor wafers.

 

The basic marking system consists of a laser, a scanning head, a flat field focusing lens, and computer conrol. The computer turns the laser beam on and off as it is scanned over the surface to make the mark.  Depending upon this application, the scanning may occur in a raster pattern.

The laser scribing is similar to laser marking, except that the scan pattern is typically rectilinear, and the goal is to create micro scoring along the scan lines so that the substrate can be easily broken apart.

A wide variety of materials, including metal, wood, glass,silicon,and rubber are amenable to laser marking and scribbling.

Noncontact measurement

There are many types of laser –based noncontact measurement techniques in use today including scatter measurement, polarimetry and elipsometry and interferometric measurement. Typical applications of this technique include positioning of masks for the lithography process, mirror distance correlation with in an FTIR Spectrometer, opticalfeedbackin much high resolution positioning system.

LASERS IN TELECOMMUNICATIONS

One of the more exciting applications of lasers is in the field of telecommunications, in which tiny diode lasers generate the optical signal transmitted through optical fibers. Because the bandwidth of these fiber optic systems is so much greater than that of conventional copper wires, fiber optics is playing a major role in enabling the fast-growing Internet. Modern fiber optic telecommunication systems transmit multiple wavelengths through a single fiber, a technique called wavelength division multiplexing. The evolution of this technology, together with erbium-doped fiber amplifiers to boost the signal at strategic points along the transmission line, is a major driving force in today’s optoelectronics market.

The laser technology to automobile industry is introduced with some instances of foreign automobile works and the principles, the characteristics and the application areas of laser cutting, laser welding, laser surface treatment and laser detecting are analyzed in detail. The application of the laser technology to domestic automobile industry is also elaborated and it is expressed that with the advantages of assuring processing quality, increasing production efficiency and reducing manufacture cost the laser technology is fit for spreading in automobile industry. At last, something that should be studied next about the laser technology is explored.

 

Laser shock processing (LSP) or laser peening is an innovative surface treatment technique for strengthening metals. This process induces a compressive residual stress field which increases fatigue crack initiation life and reduces fatigue crack growth rate. The characteristics and the latest development of laser shock processing are introduced

Microscopy

Confocal laser scanning microscopimages of thick specimens at y and two photon excitation microscopy make use of lasers to obtain blur-free images of thick specimens at various depths. Additional laser microscopy techniques include harmonic microscopy, four-wave mixing microscopy and interferometric microscopy.

Nuclear fusion

Some of the world’s most powerful and complex arrangements of multiple lasers and optical amplifiers are used to produce extremely high intensity pulses of light of extremely short duration, e.g. laboratory for laser energeticsNational Ignition FacilityGEKKO XIINike laserLaser MégajouleHiPER. These pulses are arranged such that they impact pellets of tritiumdeuterium simultaneously from all directions, hoping that the squeezing effect of the impacts will induce atomic fusion in the pellets. This technique, known as “inertial confinement fusion“, so far has not been able to achieve “breakeven”, that is, so far the fusion reaction generates less power than is used to power the lasers, but research continues.

One of the leading laser applications is materials processing, in which lasers are used to cut, drill, weld, heat-treat, and otherwise alter both metals and nonmetals. Lasers can drill tiny holes in turbine blades more quickly and less expensively than mechanical drills. Lasers have several advantages over conventional techniques of cutting materials. For one thing, unlike saw blades or knife blades, lasers never get dull. For another, lasers make cuts with better edge quality than most mechanical cutters. The edges of metal parts cut by laser rarely need be filed or polished because the laser makes such a clean cut. Laser welding can often be more precise and less expensive than conventional welding techniques. Moreover, laser welding is more compatible with robotics, and several large machine-tool builders offer fully automated laser welding systems to manufacturers. Laser heat-treating involves heating a metal part with laser light.

Photochemistry

Some laser systems through the process of mode locki ng can produce extremely brief pulses of light.Such pulses can be used to initiate and analyses chemical reactions, a technique known as photochemistry. These pulses allowing the detection of shortlivedvitermediate molecules. This method is use ful in biochemistry

A technique that has recent success is laser cooling.This   involves atom trapping, a method where a number of atoms are confined in a specially shaped arrange met of electric and magnetic fields.Shining particular wavelengths of laser light at the ions or atoms slows them down, thus cooling them.As this process is continued, they all are slowed and have the same energy level, forming an unusual arrangement of matter known as a Bose-Einstein condensate.

When the Apollo astronauts visited the moon, they planted        retroreflector arrays to make possible the lunar laser rangingexperiment.Laser beams are focused through large telescopes on earth aimed toward the arrays, and the time taken for the beam to be  reflected back to earth measured to determine the distance between the Earth and Moon with high accuracyA very useful and interesting application of laser is in the field of communications, which takes advantage of its wide bandwidth and narrow beam width over long distances. The laser beams can be created in a range of wavelengths from the ultraviolet to the infrared regions of the electromagnetic spectrum. The colour of the emitted light is relatively not important. The infrared region is preferred by the military, as it is more difficult to detect. The advent of semiconductor lasers has made possible the use of lasers for signal transmission. They are excited directly by electric cur-rent to yield a laser beam in the invisible infrared region.

MILITARY USES

Military uses of lasers include applications such as target designation and ranging, defensive countermeasures, communications and directed energy weapons

A particular aspect of laser transmission, which makes it preferable to the ordinary radio waves for military purposes is the strict secrecy provided by the narrow beam width. Since no unwanted reception outside the narrow bundles of rays is possible, a high degree of secrecy can be maintained . between two points, and thus, an interception-proof communication network can be realized. Besides, laser communication system is immune from jamming and from interference by spurious radio noise.

Anti-Missile Defense System (Star Wars)

In an antimissile defense system, laser is used to dispose the energy of warhead, not by vaporizing or melting it, but by partially damaging the missile, say by drilling a hole. Tremendous energy is required to completely burn the missile, which is not practicable. If a guided vane of a missile is fractured, several vibrations will be developed in the air frame thereby disintegrating major sensitive portion of the missile

LASERS IN RESEARCH AND MEDICINE

Scientists count lasers among the most powerful investigational tools of modern science. Again, the laser’s narrow beam is valuable, but in the laboratory the other characteristics of laser light are often important too. Because a laser’s beam contains light of such pure color, it can probe the dynamics of a chemical reaction while it happen started out in research laboratories, and many of the most sophisticated ones are still being used there. Chemists, biologists, spectroscopists, r it can even stimulate a reaction to happen. In medicine, the laser’s narrow beam has proven a powerful tool for therapy. In particular, the carbon dioxide laser has been widely adopted by surgeons as a bloodless scalpel because the beam cauterizes an incision even as it is made. Indeed, some surgeries that cause profuse bleeding had been impossible to perform before the advent of the laser. The laser is especially useful in ophthalmic surgery because the beam can pass through the pupil of the eye and weld, cut, or cauterize tissue inside the eye. Before lasers, any procedure inside the eye necessitated cutting open the eyeball. Even more exciting is the promise of new, emerging techniques in laser medicine. The LASIK procedure, promises to restore perfect eyesight to millions of people. Because a laser’s color is so pure, it may have the capability to destroy a diseased tumor while leaving nearby tissue undamaged. Laser radial keratotomy—cutting several tiny incisions with a laser in the cornea—may one day make eyeglasses and contact lenses obsolete for millions of people.

Nowadays, law enforcement officers use Laser technology to detect when automobiles are exceeding speed limits. Technology has led to the development of modern machines such as cars and motorcycles which allow us to be mobile and travel freely and airplanes which travel at a supersonic speed. 3D laser scanning is a powerful tool, which can have several applications in highway engineering and design The ability to construct a highly detailed model of the infrastructure at its actual current state is valuable as it can be used to monitor its condition.

3Dlaser scanning technology can be very useful in in-depth accident investigation, assisting not only the detailed identification of accident causes but also the design of the appIn this research, the use of 3D laser scanning technologies is proposed as a tool to support the evaluation of the effectiveness of road safety measures at intersections. This includes obtaining more detailed representations of the junction geometry and conditions appropriate countermeasures. Laser communication in space has long been a goal for NASA because it would enable data transmission rates that are 10 to1000 times higher than traditional radio waves. While lasers and radio transmissions both travel at high speed, lasers can pack more data. It’s similar to moving from a dial -up internet connection to broad band.

Astronomers’ cold use lasers like very accurate rulers to measure the movement of planets with unprecedented precesion.With micro waves, limited to numbers, whereas lasers have a potential for getting down in to well beyond the centimeter range.