Gas And Semiconductor A Solid State Lasers example essay topic

Lasers and Their Uses 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 boring metals, communication, bar-code scanners, etc. Over the past three decades' lasers have become a tool used daily 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 have chosen this topic to write about. The term laser is an acronym.

It stands for 'light amplification by stimulated emission of radiation'. They produce a narrow, intense beam of coherent light. In a laser the atoms or molecules of a crystal, like ruby or garnet-or of a gas, liquid, or other substance-are excited so that more of them are at higher energy levels than are at lower energy levels. If a photon whose frequency corresponds to the energy difference between the excited and ground states strikes an excited atom, the atom is stimulated, as it falls back to a lower energy state, to emit a second photon of the same frequency, in phase with and in the same direction as the bombarding photon.

This process is called stimulated emission. The bombarding photon of the emitted photon may then strike other excited atoms, stimulating further emission of photons, all of the same frequency and phase. This process produces a sudden burst of coherent radiation as all the atoms discharge in a rapid chain reaction. The light beam produces is usually pencil thin and maintains its size and direction over 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 grain of salt. There are many parts to lasers. I will now explain what they are and their uses. 1) Pumping systems: The pumping system is used to transmit energy to the atoms or molecules of the medium used in the laser. a. optical pumping systems uses photons provided by a source such as a Xenon gas flash lamp or another laser to transfer energy to the lasing material.

The optical source must provide photons which correspond to the allowed transition levels of the lasing material. b. collision pumping relies on the transfer of energy to the lasing material by collision with the atoms or molecules of the lasing material. Again, energies which correspond to the allowed transition must be provided. This often done by electrical discharge in a pure gas - or gas mixture - in a tube. c. chemical pumping systems use the binding energy released in chemical reactions to raise the lasing material to the metastable state. 2) Optical Cavity: An optical cavity is required to provide the amplification desired in the laser and to select the photons which are traveling in the desired direction. As the first atom or molecule in the metastable state of the inverted population decays it triggers (by stimulated emission) the decay of another atom or molecule in the metastable state. 3) Laser Media: Lasers are usually classified by the lasing material used by the laser.

There are four types which are solid state, dye, gas and semiconductor. a. solid state lasers employ a lasing material distributed in a solid. Accessory devices which may be internal or external may be used to convert the output. b. gas lasers use a gas or a mixture of gas within a tube. The most common gas laser uses a mixture of helium and neon with a primary output of 632.8 nm which is a red visible colour. c. dye lasers use a laser medium that is usually a complex organic dye in a liquid solution or suspension. The most striking feature of these lasers is their 'tunability'.

Proper choice of the dye and it's concentration allows production of laser light over a broad range of wavelength in or near the visible spectrum. d. semiconductor lasers are not to be confused with solid state lasers. Semiconductor devices consist of two layers of semiconductor material sandwiched together. Laser Applications Laser Surgery The small, intense, bright beam of light can be focused with lenses to provide a point of energy intense enough to burn through living flesh. Laser Welding, Cutting & Blasting Once again the laser's intense energy when focused make it ideal for providing concentrated welding and cutting. Laser Shows The intense color of laser light has opened up a whole new world for laser artists to weave a new kind of art using different coloured lenses, mirrors and crystals. Power Generation Laser-powered fusion holds hope of generating tremendous amounts of electricity through the use of lasers.

Information Technology Using fiber optic bundles to carry them, modulated laser beams can transfer huge amounts of information (internet). Lasers in compact disc players read tiny reflections on CD's and laser discs to play back audio and video. Someday your house could be fitted with fiber optics to carry cable tv and phone service.