 |
Lasers
|
Below is one of our free research papers on Lasers. If the term paper below is not exactly what you're looking for, you can search our essay database for other topics.
Lasers The light from lasers differs from ordinary light in several important aspects. Ordinary light from a light bulb travels randomly in all directions (unless the bulb is equipped with an integral reflector that directs the light). The light is thus incoherent. Even when incoherent light is directed with a reflector, it still spreads rapidly. The light from a laser is temporary and spatially coherent. This means that all of the wave-fronts of light are lined up in time and space (see Diagrams). The waves of light go up and down in sync, and travel in the same direction. Coherent light spreads less than other types of light. For example the beam of a tightly focused flashlight would spread between 2 degrees and 5 degrees over a 3 meter (10 ft) throw distance. The sides of a laser beam are almost parallel but the light still spreads slightly. This spread is called divergence and is measured in milliradians (mrad). If a laser has a specified divergence of 5 mrad, then in the above example with a 3 meter throw (10 ft), a laser beam will spread only about 3/20 of a degree. This is a simplified explanation of the process of stimulated emission. If you are interested in more detailed information about this subject, you should consult a science or physics book. Let us take the HeNe laser as an example. If a glass tube were filled with a mixture of helium and neon gas; and an electrical current were applied to the electrodes, the gas wo...
|