Likewise, the force of the signal or pulse from the coherent beam of light is more powerful than that of any single wave. These properties make lasers useful in many ways. The directionality of laser light allows it to travel great distances and remain intense. It can be focused to drill holes or weld metal. The monochromaticity of laser light makes it useful in the analysis of chemicals based on the patterns of light each element absorbs.
Lasers consist of four components.
An excitation medium that is a source of energy such as an electric current or a flash of light that excites or stimulates the active medium so that it produces light. The feedback mechanism, usually two carefully aligned mirrors, lets the light bounce back and forth again and again through the active medium so the light is amplified. The light that escapes is the laser output. This output can be either a steady beam or bursts of light. Today, hundreds of lasers serve in thousands of ways.