ABSTRACT
Lasers produce light with many characteristics that are unique compared to other light sources. For example, the monochromatic nature of a laser beam means that it emits photons at a single wavelength with very little energy at wavelengths other than the central peak. The temporal nature of a laser beam enables it to vary from a continuous wave to an extremely short pulse providing very high power densities. The coherence of a laser enables it to travel in a narrow beam with a small and welldefined divergence or spread. This allows a user to exactly define the area irradiated by the laser beam. Because of this coherence, a laser beam can also be focused to a very small and intense spot, resulting in a highly concentrated energy density. This property makes the laser beam useful for many applications in physics and chemistry and in medical and industrial applications. Finally, a laser beam has a unique spatial intensity profile that gives it very significant characteristics. The beam profile is the quantitative pattern of the distribution of the irradiance across the beam.
