Laser beam material processing, Mechanical Engineering



Light Amplification of Stimulated Emission of Radiation (LASER) is generated when a lasing medium is excited by a source of energy. Gases like argon, helium, neon and carbon dioxide are used as a lasing medium. In addition, Neodymium - Doped Yttrium Aluminium Garnet (Nd:YAG) is the most widely used solid state lasing medium. At the heart of the lasing phenomenon is the ability of photons to stimulate the emission of other photons, each having the same wavelength and direction of travel as the original. According to quantum theory, atoms and molecules have discrete energy levels and can change from one level t o anot her in discontinuous jumps. The energy change required for a jump is provided by the atom's absorption or emission of a burst of electromagnetic radiation. The radiation frequencies involved and the energy spacings between levels are characteristic of the atom, and thus differ from element to element.

Generally, atoms or molecules remain quiescent at their lowest energy level, or ground state. But, if these particles are excited into higher energy states by an intense flash of light, an electrical Charge, or other means they will in dropping back to the normal ground state, emit incoherent light in the process. (This is what happens in fluorescent lamps and some types of street lights). In a laser cavity, such emitted photons are trapped between highly polished and parallel mirrors, forcing them to bounce back and Forth in the cavity. Whenever, a photon of any particular wavelength passes close to another excited particle, the second particle will also be stimulated to emit a photon that is identical in wavelength phase and spatial coherence to the first. Both phot ons are now capable of stimulating the emission of more photons like themselves and these too, become part of the growing wave between mirrors. The wave length of each photon is related to its energy E. Lasing begins when enough photons are present and if one of the mirrors is partially transparent, a highly disciplined, intense, now coherent beam is emitted.

Posted Date: 9/17/2012 7:56:02 AM | Location : United States

Related Discussions:- Laser beam material processing, Assignment Help, Ask Question on Laser beam material processing, Get Answer, Expert's Help, Laser beam material processing Discussions

Write discussion on Laser beam material processing
Your posts are moderated
Related Questions
Industrial applications of ultrasonics-cleaning, welding, soldering, drilling

Idle Circuit : During Idling while the throttle valve is almost closed the vacuum is very high at Venturi area and no air-fuel mixture is drawn through the main circuit, as t

Working of Sleeve in Radial drilling machine The sleeve or quill assembly does not revolve but might be slide in its bearing in a direction parallel to its axis. When the slee

Q. Local operator panel for steam generator? A local operator's panel is required for operator use during Steam Generator light off. This panel shall contain the following equ

Q. Horizontal Vessels and Vertical Vessels? Horizontal Vessels A horizontal vessel, designed to support a full weight load of water, shall be tested while resting on its sup

Normal 0 false false false EN-IN X-NONE X-NONE MicrosoftInternetExplorer4

Determine the stresses in the shell: A thin spherical shell of 1.5 m diameter & 8 mm thickness is filled having a liquid at an internal pressure of 1.5 N/mm 2 . Determine the

Data given for gear problem T P = 30 TG = 80 φ = 20o m = 12 mm Addendum = 10 mm then determine the length of path of contact, length of Arc of contact and contact Ratio.

Illustrate governing Mechanism of Francis turbine.

(Rigid body rotation) Derive the equation for the shape of the surface zsurf(rsurf) for a rigid-body rotation of water at angular speed (rad/sec). Follow this process: 1) S