We have all at some point in our lives used or seen someone use a laser. They are used in compact disc players for stereos or computers, laser surgery,laser printers, holography, cutting and borring metals, communication, bar-codescanners, etc.
Over the past three decades’ lasers have become a tool useddaily by many people and they have become very useful in scientific research. As you can see lasers are a very useful and important tool which is why I havechosen this topic to write about. The term laser is an acronym. It stands for “light amplification bystimulated emission of radiation”. They produce a narrow, intense beam ofcoherent light.
In a laser the atoms or molecules of a crystal, like ruby or garnet-orof a gas, liquid, or other substance-are excited so that more of them are athigher energy levels than are at lower energy levels. If a photon whosefrequency corresponds to the energy difference between the excited and groundstates strikes an excited atom, the atom is stimulated, as it falls back to alower energy state, to emit a second photon of the same frequency, in phasewith and in the same direction as the bombarding photon. This process iscalled stimulated emission. The bombarding photon of the emitted photon maythen strike other excited atoms, stimulating further emission of photons, allof the same frequency and phase. This process produces a sudden burst ofcoherent radiation as all the atoms discharge in a rapid chain reaction.
Thelight beam produces is usually pencil thin and maintains its size and directionover very long distances. Lasers vary greatly in the way they look and what they are used for. Some lasers are as large as buildings while others can be the size of a grainof salt. There are many parts to lasers. I will now explain what they are andtheir uses. 1) Pumping systems:The pumping system is used to transmit energy to the atoms or moleculesof the medium used in the laser.
a. optical pumping systems uses photons provided by a source such as a Xenongas flash lamp or another laser to transfer energy to the lasing material. Theoptical source must provide photons which correspond to the allowed transitionlevels of the lasing material. b.
collision pumping relies on the transfer of energy to the lasing material bycollision with the atoms or molecules of the lasing material. Again, energieswhich correspond to the allowed transition must be provided. Thisoften done by electrical discharge in a pure gas – or gas mixture – in a tube. c. chemical pumping systems use the binding energy released in chemicalreactions to raise the lasing material to the metastable state. 2) Optical Cavity: An optical cavity is required to provide the amplification desired in thelaser and to select the photons which are traveling in the desired direction.
As the first atom or molecule in the metastable state of the invertedpopulation decays it triggers (by stimulated emission) the decay of anotheratom or molecule in the metastable state. 3) Laser Media:Lasers are usually classified by the lasing material used by the laser. Thereare four types which are solid state, dye, gas and semiconductor. a. solid state lasers employ a lasing material distributed in a soloid matrixsytem.
Accessory devices which may be internal or external may be used toconvert the output . b. gas lasers use a gas or a mixture of gas within a tube. The most common gaslaser uses a mixture of helium and neon with a pimary output of 632.
8 nm whichis a red visible colour. c. dye lasers use a laser medium that is ususally a complex organic dye in aliquid solution or suspension. The most striking feature of these lasers istheir “tunability”.
Proper choice of the dye and it’s concentration allowsproduction of laser light over a broad range of wavelength in or near thevisible spectrum. d. semiconductor lasers are not to be confused with solid state lasers. Semiconductor devices consist of two layers of semiconductor material sandwichedtogether. Laser ApplicationsLaser SurgeryThe small, intense, bright beam of light can be focused with lenses to providea point of energy intense enough to burn through living flesh.
Laser Welding, Cutting & BlastingOnce again the laser’s intense energy when focused make it ideal for providingconcentrated welding and cutting. Laser ShowsThe intense color of laser light has opened up a whole new world for laserartists to weave a new kind of art using different coloured lenses, mirrors andcrystals. Power GenerationLaser-powered fusion holds hope of generating tremendous amounts of electricitythrough the use of lasers. Information TechnologyUsing fiber optic bundles to carry them, modulated laser beams can transferhuge amounts of information(internet). Lasers in compact disc players read tinyreflections on CD’s and laser discs to play back audio and video.
Someday yourhouse could be fitted with fiber optics to carry cable tv and phone service.Category: Science
